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Agenda_Intro1.pdf
Intro1_M00_toc.pdf
Intro1_M01_intro.pdf
Intro1_M02_fea.pdf
Intro1_M03_getting_started.pdf
Intro1_M04_basics.pdf
Intro1_M05_gen_procedure.pdf
Intro1_M06_create_solid_model.pdf
Intro1_M07_create_FEA_model.pdf
Intro1_M08_define_material.pdf
Intro1_M09_loading.pdf
Intro1_M10_solution.pdf
Intro1_M11_structural.pdf
Intro1_M12_thermal.pdf
Intro1_M13_postprocessing.pdf
Intro1_M14_short-topics.pdf
Intro1_MAPP_Appendix.pdf
I d i ANSYS
Training Manual
Introduction to ANSYS Part 1Part 1
Training ManualIntroduction to ANSYS - Part 1
Inventory Number: 002268First Edition
ANSYS Release: 10.0Published Date: February 7, 2006
Registered Trademarks:ANSYS® is a registered trademark of SAS IP Inc.All other product names mentioned in this manual are trademarks or registered trademarks of their respectiveAll other product names mentioned in this manual are trademarks or registered trademarks of their respective manufacturers.
Disclaimer Notice:This document has been reviewed and approved in accordance with the ANSYS, Inc. Documentation Review and Approval Procedures. “This ANSYS Inc. software product (the Program) and program documentation (Documentation) are furnished by ANSYS, Inc. under an ANSYS Software License Agreement that contains provisions concerning non-disclosure, copying, length and nature of use, warranties, disclaimers and remedies, and other provisions. The Program and Documentation may be used or copied only in accordance with the terms of that License Agreement.”
A. Overview 7 2B. Element Attributes 7-4C. Multiple Element Attributes 7-29D. Workshop 7-36E. Controlling Mesh Density 7-37F. Mesh Order Control 7-46G Generating the Mesh 7-47
ANSYS Release: 10.0Published Date: February 7, 2006
Registered Trademarks:ANSYS® is a registered trademark of SAS IP Inc.All other product names mentioned in this manual are trademarks or registered trademarks of their respectiveAll other product names mentioned in this manual are trademarks or registered trademarks of their respective manufacturers.
Disclaimer Notice:This document has been reviewed and approved in accordance with the ANSYS, Inc. Documentation Review and Approval Procedures. “This ANSYS Inc. software product (the Program) and program documentation (Documentation) are furnished by ANSYS, Inc. under an ANSYS Software License Agreement that contains provisions concerning non-disclosure, copying, length and nature of use, warranties, disclaimers and remedies, and other provisions. The Program and Documentation may be used or copied only in accordance with the terms of that License Agreement.”
C. Multiple Element Attributes 7 29D. Workshop 7-36E. Controlling Mesh Density 7-37F. Mesh Order Control 7-46G. Generating the Mesh 7-47H. Changing a Mesh 7-49I Mapped Meshing 7-52
B. Start File 14-9C. APDL 14-10D. Defining Parameters 14-11E. Using Parameters 14-15F. Retrieving Database Information 14-18G. Batch Mode 14-22H I t Fil 14 23
Part 1Part 1Part 1Part 1Part 1Part 1
H. Input Files 14-23I. Session Editor 14-28J. Workshops 14-30
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Training Manual
Introduction to ANSYS - Part 1
Table of ContentsIN
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2. FEA and ANSYS
3. Getting Started
10. Solution
11. Structural Analysis ON
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4. ANSYS Basics
5. General Analysis Procedure
12. Thermal Analysis
13. Postprocessing
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6. Creating the Solid Model
7. Creating the Finite Element Model
14. Short Topics
Appendix Part 1Part 1Part 1Part 1Part 1Part 1
8. Defining the Material
(Slide shown for Hyperlinking to Chapters)
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(Slide shown for Hyperlinking to Chapters)
Chapter 1
Introduction
Training Manual
Chapter 1 - Introduction
Welcome!IN
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• Welcome to the Introduction to ANSYS Training Course!
Thi t i i th b i f h t ANSYS f
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• This training course covers the basics of how to use ANSYS for static or steady-state analyses.
• It is intended for all new or occasional ANSYS users regardless of ON
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• Several advanced training courses are available on specific topics See the training course schedule on the ANSYS
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topics. See the training course schedule on the ANSYS homepage: www.ansys.com under “Training Services”.
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Training Manual
Chapter 1 - Introduction
Course ObjectivesIN
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To teach the basics of ANSYS in the following areas:
ANSYS biliti b i ANSYS t i l d th ANSYS GUI
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• ANSYS capabilities, basic ANSYS terminology, and the ANSYS GUI
• How to perform a complete ANSYS analysis… the basic steps involved O
pfor geometry modeling, mesh manipulation,structural/thermal analysis, and optimization,which is tightly integrated with CAD packages N
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• CFX – State-of-the-art CFD solvers, including the coupled, parallel CFX-5 solver
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• ICEM CFD – Powerful meshing tools with general pre- and post-processing features,including ICEM CFD for generating complexCFD grids and AI*Environment for creating
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CFD grids and AI Environment for creatingwith sophisticated structural FEA meshes
Training Manual
Chapter 2 - FEA and ANSYS
…About ANSYSIN
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• ANSYS is a complete FEA software package used by engineers worldwide in virtually all fields of engineering. Partial listing of the
biliti
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capabilities:– Structural
• Linear• Nonlinear
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• Nonlinear – Material, Geometric, Contact
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– Modal, Harmonic, Transient Dynamic, Spectrum, Random Vibration– Explicit Dynamics with ANSYS LS-DYNA
– Thermal• Steady State and Transient Part 1
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Steady State and Transient– Fluid (CFD, Acoustics, and other fluid analyses)– Low- and High-Frequency Electromagnetics– Coupled Field
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Training Manual
Chapter 2 - FEA and ANSYS
…About ANSYSIN
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• A partial list of industries in which ANSYS is used:– Aerospace O
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– Automotive– Biomedical– Bridges & Buildings
Electronics & Appliances
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Training Manual
Chapter 2 - FEA and ANSYS
…About ANSYSIN
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• ANSYS Multiphysics - Provides the analysis industry's most comprehensive coupled physics tool combining structural, thermal, CFD, acoustic and electromagnetic simulation capabilities into a single software product
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simulation capabilities into a single software product.
• ANSYS Mechanical - Structural and Thermal analysis tool which includes a full complement of nonlinear and linear elements, material laws ranging from metal to rubber, and the most comprehensive set of solvers available. O
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• ANSYS Structural - Provides all the power of ANSYS nonlinear structural capabilities -- as well as linear capabilities -- to deliver the highest quality, most-reliable structural simulation results available. N
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• ANSYS Professional – Inexpensive, easy-to-use program for structural/thermal analysis projects.
• ANSYS DesignSpace – An easy-to-use package that gives designers the tool to Part 1Part 1Part 1Part 1Part 1Part 1
conceptualize, design and validate ideas right on the desktop.
• ANSYS LS-DYNA – Meets design challenges by fusing LSTC’s LS-DYNA explicit dynamic solver technology with the pre-/post-processing power of ANSYS software. This powerful pairing helps engineers understand the elaborate combinations of nonlinear
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powerful pairing helps engineers understand the elaborate combinations of nonlinear phenomena found in crash tests, metal forging, stamping and catastrophic failures.
• ANSYS Emag – Addresses the analysis needs of the low-frequency electromagnetics market.
Training Manual
Chapter 2 - FEA and ANSYS
…About ANSYSIN
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Workbench Modules:
• DesignModeler – Workbench application that provides modeling functions unique for simulation that
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g pp p g qinclude detailed geometry creation, CAD geometry modification, and concept model creation tool.
• DesignXplorer – Works within the Workbench environment to perform Design Of Experiments (DOE) analyses of any Workbench simulation, including those with CAD parameters.
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• DesignXplorer VT – A robust Variational Technology solution that gives users a broader view of design concepts providing complete FEA results for every design point.
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• ANSYS Fatigue – Adds the capability to simulate performance under anticipated cyclic loading conditions over anticipated product life span.
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Training Manual
Chapter 2 - FEA and ANSYS
…About ANSYSIN
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• Other products:– ANSYS ICEM CFD – Provides sophisticated geometry acquisition, mesh O
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generation, post-processing and mesh optimization tools.
– ANSYS CFX – Suite of finite-volume-based Computational Fluid Dynamics (CFD) software, offered by CFX, an ANSYS, Inc. subsidiary including CFX-5, the best-in-class CFD software.
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CFD software.
– ANSYS ParaMesh – a tool that works directly on legacy models. The mesh, a tessellated representation, can be parameterized and made to move almost as though it were geometry, giving a legacy model incredible utility. N
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Training Manual
Chapter 2 - FEA and ANSYS
C. What is FEA?IN
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• Finite Element Analysis is a way to simulate loading conditions on a design and determine the design’s response to those conditions
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conditions.
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– Each element has exact equations that describe how it responds to a certain load.
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– The “sum” of the response of all elements in the model gives the total response of the design.
– The elements have a finite number
by academic and industrial researchers during the 1950s and 1960s.
• The underlying theory is over 100 years old and was the basis
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The elements have a finite number of unknowns, hence the name finite elements.
100 years old, and was the basis for pen-and-paper calculations in the evaluation of suspension bridges and steam boilers.
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Training Manual
Chapter 2 - FEA and ANSYS
…What is FEA?IN
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has infinite unknowns.– So the question arises: How good is the approximation?
– Unfortunately, there is no easy
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simulation. We will, however, attempt to give you guidelines throughout this training course.
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Physical System F.E. Model
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Training Manual
Chapter 2 - FEA and ANSYS
…What is FEA?IN
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Why is FEA needed?
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• To reduce the amount of prototype testing– Computer simulation allows multiple “what-if” scenarios to be tested
quickly and effectively. ON
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• To simulate designs that are not suitable for prototype testing– Example: Surgical implants, such as an artificial knee
• The bottom line:
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• The bottom line:– Cost savings– Time savings… reduce time to market!– Create more reliable, better-quality designs Part 1
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Create more reliable, better quality designs
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Training Manual
Chapter 2 - FEA and ANSYS
D. Instructor ExampleIN
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• Your instructor is going to do a simple example so you get a feel for what you’re going to be learning. O
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• The instructor will do the example through the GUI without going into any detail on how to generate the model.
The e ample is of a cantile er beam ith a load at the end
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• You will see that the deflection at the tip matches theory.→ δ = PL3/3EI = (-100)*(103)/(3)*(30e6)*(1/12) = -0.013 N
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reside) and a Job Name of your choosing. The default Job Name is “file”. N
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Chapter 3 – Getting Started
…Product LauncherIN
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• Customization/Preferences tab allows you to set
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memory options, run a custom version of ANSYS, define parameters, set the language to be used by the O
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• A customizable file called start100.ans can also be read at start-up. Part 1
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Training Manual
Chapter 3 – Getting Started
…Product LauncherIN
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tab is used to set up Parallel Performance solving options.
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are also selected here..
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Training Manual
Chapter 3 – Getting Started
…Product LauncherIN
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• MFX - ANSYS/CFX Setup tab is used to set up ANSYS Multi-
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set up ANSYS Multi-field solving options for ANSYS and CFX.
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Training Manual
Chapter 3 – Getting Started
D. ANSYS WorkbenchIN
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• Quick note about the ANSYS Workbench... O
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Chapter 3 – Getting Started
...ANSYS WorkbenchIN
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• CAD Associativity
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– Provides control of your key CAD model parameter in the Workbench parameter manager.
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Parameter management driving DOE optimization
– Ability to control both simulation parameters - such as material properties, force direction, and temperature - as well as CAD parameters.
• The Finite Element Model can be transferred to the ANSYS Environment.
• ANSYS Workbench is covered in detail in a separate training Part 1Part 1Part 1Part 1Part 1Part 1
ANSYS Workbench is covered in detail in a separate training course (Workbench – Simulation Introduction).
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Training Manual
Chapter 3 – Getting Started
E. Memory OverviewIN
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• System virtual memory is simply a portion of the computer's hard
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• System virtual memory is simply a portion of the computer s hard disk used by the system to supplement physical memory.
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Chapter 3 – Getting Started
…Memory DefinitionsIN
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y• Workspace space (i.e –m ) is the memory ANSYS needs to run.
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calculations, and so on.
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S t h W k D t b
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Scratch space = Workspace - Database
Training Manual
Chapter 3 – Getting Started
…ANSYS Memory ManagerIN
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Product Launcher.– When the ANSYS Memory Manager is specified, ANSYS will allocate
more memory from the system when it is needed.– When custom memory settings are specified, no more memory can be
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• In general, you shouldn t worry about memory management in ANSYS. The ANSYS Memory Manager will do the job for you. However, there are exceptions when you will need set the Total Workspace. Part 1
Part 1Part 1Part 1Part 1Part 1• See Chapter 19 of the Basic Analysis Guide for more details on
Memory Management and Configuration.
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Training Manual
Chapter 3 – Getting Started
F. GUI - Layout Utility Menu
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Output Window
Icon Toolbar Menu Input Line Raise/Hidden Icon
Contact Manager Icon
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Abbreviation Toolbar Menu
Command Window Icon
Model Control Toolbar O
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Current SettingsUser Prompt Info
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Chapter 3 – Getting Started
…GUI - LayoutIN
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• Fonts of the layout can be customized:– Windows System
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• Utility Menu > Menu Ctrls > Font Selection...– Unix system:
• Common Desktop Environment (CDE) uses the system settings• Otherwise (e g a telnet to a Unix Machine) uses the ~/ Xdefaults settings
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• Otherwise (e.g. a telnet to a Unix Machine) uses the ~/.Xdefaults settings– *EUIDL*Font: Times 12 normal– *EUIDL*Background: purple
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• The GUI has been modularized using the Tcl/Tk language which allows for dialog boxes, ANSYS messages, etc. to be easily changed to a country’s native language. Part 1
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Training Manual
Chapter 3 – Getting Started
…GUI - Graphics WindowIN
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O• Display location of model entities, postprocessing contours, and postprocessing graphs. O
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Graphics Area
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 3 – Getting Started
…GUI - Main MenuIN
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• Tree structure format.
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• Contains the main functions required for an analysis.
• Use scroll bar to gain access to long tree ON
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g gstructures.
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scroll bar
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Training Manual
Chapter 3 – Getting Started
…GUI - Main MenuIN
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OBefore collapsing Preprocessor Branch After expanding Preprocessor Branch • Tree structure behavior – sub branch preserved
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Select to collapse Preprocessor Branch N
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The tree structure is the same before
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and after the Preprocessor branch of Main Menu is collapsed
Training Manual
Chapter 3 – Getting Started
…GUI - Main MenuIN
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OPosition mouse cursor on branch of Main
• Expand all option
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Menu – then select right mouse button
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The option to expand the branch is displayed Part 1
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Selecting “Expand All” expands th b h t t
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the branch contents
Training Manual
Chapter 3 – Getting Started
…GUI - Main MenuIN
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ORight Click in Main Menu and select “Preferences”
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and select Preferences .
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Level color, filtering and expansion of Main Menu can be changed. N
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Training Manual
Chapter 3 – Getting Started
…GUI - Main MenuIN
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With “Expand headings” and “Collapse siblings” behavior active … O
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When the Delete branch is opened, the Create branch is closed
Note, inactivate “Collapse siblings” to
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, p gkeep open the Create branch
Training Manual
Chapter 3 – Getting Started
…GUI - Main Menu Filtered BranchesIN
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Main Menu with structural and thermal element type defined
Main Menu with only thermal element type defined O
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Only “Apply” branches shown are those for defined element types
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Training Manual
Chapter 3 – Getting Started
…GUI - Abbreviation Toolbar MenuIN
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• Contains abbreviations -- short-cuts to commonly used commands and functions. O
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• A few predefined abbreviations are available, but you can add your own. Requires knowledge of ANSYS commands. O
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• A powerful feature which you can use to create your own “button menu” system!
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Training Manual
Chapter 3 – Getting Started
…GUI - Icon Toolbar MenuIN
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• Contains icons of commonly used functions.
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• Can be customized by the user (i.e adding icons, additional toolbars)
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Pan-Zoom-RotateSave Analysis
Image Capture NSYS
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Open ANSYS FileImage Capture
Report Generator
Part 1Part 1Part 1Part 1Part 1Part 1New Analysis ANSYS Help
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Training Manual
Chapter 3 – Getting Started
…GUI - Icon Toolbar MenuIN
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• Jobname definition when using Open ANSYS File Icon:– the ANSYS jobname will be changed to the prefix of the database file being resumed. O
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Open ANSYS File
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When opening the “blades.db” database (using the Open ANSYS File Icon), the jobname will be changed to “blades”.
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The Open ANSYS File Icon can be used to open either ANSYS
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Database or ANSYS Command file types
Training Manual
Chapter 3 – Getting Started
…GUI - Raise/Hidden IconIN
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• The Raise/Hidden Icon can be used to “bring to the front” any hidden ANSYS created windows (except the output window). O
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Select Raise/ Hidden Icon
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Pan/Zoom/Rotate Widget Hidden
Part 1Part 1Part 1Part 1Part 1Part 1
Pan/Zoom/Rotate Widget Shown
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Training Manual
Chapter 3 – Getting Started
…GUI - Input WindowIN
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• Allows you to enter commands. (Most GUI functions actually “send” commands to ANSYS. If you know these commands, you O
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can type them in the Input Window).
• As a command is typed, the format of the command is dynamically displayed.
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dynamically displayed.
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Click on the X to return the input to the toolbar.
Clicking on the ANSYS Command Window Icon
th i t li t
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moves the input line to a separate command window, which can be moved around the screen.
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Training Manual
Chapter 3 – Getting Started
…GUI - Input WindowIN
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List of issued commands• Reissuing commands:
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Use scroll bar to gain access to all commands issued
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li ki th li t d d
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Select down arrow to see list of issued commandsclicking on the listed command
Part 1Part 1Part 1Part 1Part 1Part 1The up and down arrows on the keyboard can be
used to select different listed commands
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Training Manual
Chapter 3 – Getting Started
…GUI - Utility MenuIN
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• Contains utilities that are generally available throughout the ANSYS session: graphics, on-line help, select logic, file controls,
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etc.
• Conventions used in Utility Menu:– “ ” indicates a dialog box
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(blank) indicates an action
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Training Manual
Chapter 3 – Getting Started
…GUI - Current SettingsIN
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• The current element attributes settings, and currently active coordinate system are displayed at the bottom on the GUI. O
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Element Attributes Active Coordinate System
Training Manual
Chapter 3 – Getting Started
…GUI - User prompt infoIN
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• Instructions to the user are displayed in the lower left hand area of the GUI. The user will be given user prompt info for operations
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such as picking operations.
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User Prompt Info
Training Manual
Chapter 3 – Getting Started
…GUI - Output WindowIN
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• The output window gives the user feedback on how ANSYS interpreted the user’s input. O
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• The Output Window is independent of the ANSYS menus. Caution: Closing the output window closes the entire ANSYS session! O
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Note: The output can be sent to a file using the /OUTPUT command.
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Able to verify the ANSYS version
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Training Manual
Chapter 3 – Getting Started
…GUI - PreferencesIN
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• The Preferences dialog (Main Menu > Preferences) allows you to filter out
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menu choices that are not applicable to the current analysis.
• For example, if you are doing a thermal l i h t filt t
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analysis, you can choose to filter out other disciplines, thereby reducing the number of menu items available in the GUI: N
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– Only thermal element types will be shown in the element type selection dialog.
– Only thermal loads will be shown.– Etc. Part 1
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Training Manual
Chapter 3 – Getting Started
…GUI – Other NotesIN
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Other GUI Notes
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• Some dialog boxes have both Apply and OK buttons.– Apply applies the dialog settings, but retains (does not close) the
dialog box for repeated use.– OK applies the dialog settings and closes the dialog box. O
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• Remember that you are not restricted to using the menus. If you know the command, feel free to enter it in the Input Window! N
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• The output window is not affected by the Raise/Hidden Button. For convenience, the user may want to resize the GUI, so part of the output window is displayed to allow easy access. Part 1
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Training Manual
Chapter 3 – Getting Started
…GUI - DemoIN
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• Demo:– Start ANSYS using the ANSYS Product Launcher O
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– Show the various parts of the GUI– Bring up “Keypoints in Active CS” dialog box and show the difference
between OK and Apply– Show the Preferences dialog
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Training Manual
Chapter 3 – Getting Started
G. The Database and FilesIN
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• The term ANSYS database refers to the data ANSYS maintains in memory as you build, solve, and postprocess your model. O
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• The database stores both your input data and some results data:– Input data -- information you must enter, such as model dimensions,
material properties, and load data. ON
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p p ,– Results data -- a set of quantities that ANSYS calculates, such as
displacements, stresses, strains, and reaction forces.
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Training Manual
Chapter 3 – Getting Started
…The Database and FilesIN
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Save and Resume
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• Since the database is stored in the computer’s memory (RAM), it is good practice to save it to disk frequently so that you can restore the information in the event of a computer crash or power failure. O
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• The SAVE operation copies the database from memory to a file called the database file (or db file for short).
Th i t t d i t li k T lb > SAVE DB
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– The easiest way to do a save is to click on Toolbar > SAVE_DB– Or use:
• Utility Menu > File > Save as Jobname.db• Utility Menu > File > Save as
Part 1Part 1Part 1Part 1Part 1Part 1
• Utility Menu > File > Save as…• SAVE command
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Training Manual
Chapter 3 – Getting Started
…The Database and FilesIN
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• To restore the database from the db file back into memory, use the RESUME operation. O
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– Toolbar > RESUME_DB– Or use:
• Utility Menu > File > Resume Jobname.dbUtilit M > Fil > R f
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• Utility Menu > File > Resume from…• RESUME command
• The default file name for SAVE and RESUME is jobname.db, but NSYS
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j ,you can choose a different name by using the “Save as” or “Resume from” functions.
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Training Manual
Chapter 3 – Getting Started
…The Database and FilesIN
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• Notes on SAVE and RESUME:– Choosing the “Save as” or “Resume from” function does NOT change
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the current jobname.– If you save to the default file name and a jobname.db already exists,
ANSYS will first copy the “old” file to jobname.dbb as a back-up. Note, ANSYS only supports one backup file (i.e. jobname.dbb). O
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– The db file is simply a “snapshot” of what is in memory at the time the save is done.
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Chapter 3 – Getting Started
…The Database and FilesIN
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• Tips on SAVE and RESUME:– Periodically save the database as you progress through an analysis.
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ANSYS does NOT do automatic saves.– You should SAVE the database before attempting an unfamiliar
operation (such as a Boolean or meshing) or an operation that may cause major changes (such as a delete). O
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• RESUME can then be used as an “undo” if you don’t like the results of that operation.
– SAVE is also recommended before doing a solve. NSYS
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Chapter 3 – Getting Started
…The Database and FilesIN
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Clearing the Database
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• The Clear Database operation allows you to “zero out” the database and start fresh. It is similar to exiting and re-entering ANSYS. O
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g– Utility Menu > File > Clear & Start New– Or use the /CLEAR command.
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Training Manual
Chapter 3 – Getting Started
…The Database and FilesIN
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Files
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• ANSYS writes and reads several files during an analysis. File names are of the format jobname.ext.
• Jobname ON
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– A name you choose while starting ANSYS, up to 32 characters. Defaults to file.
– Can be changed within ANSYS with the /FILNAME command (Utility Menu > File > Change Jobname) N
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File > Change Jobname).
• Extension– Identifies the contents of the file, such as .db for database. Part 1
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– Usually assigned by ANSYS but can be defined by user (/ASSIGN).
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Training Manual
Chapter 3 – Getting Started
…The Database and FilesIN
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• Typical files:jobname.log: Log file, ASCII. O
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• Contains a log of every command issued during the session.• If you start a second session with the same jobname in the same
working directory, ANSYS will append to the previous log file (with a time stamp)
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jobname.db, .dbb: Database file, binary.• Compatible across all supported platforms.
jobname.rst, .rth, .rmg, .rfl: Results files, binary.C i l d l l d b ANSYS d i l i
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• Contains results data calculated by ANSYS during solution.• Compatible across all supported platforms.
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Training Manual
Chapter 3 – Getting Started
…The Database and FilesIN
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File Management Tips
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y p j p g y
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• You should keep the following files after any ANSYS analysis:– log file ( .log)
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• Use /FDELETE or Utility Menu > File > ANSYS File Options to automatically delete files no longer needed by ANSYS during that session.
A t ANSYS Fil i
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• A note on ANSYS File sizes:– The maximum size of an ANSYS file depends on the system limit and on the
ability of ANSYS to handle large files on that system. Most computer systems now handle very large files without any need for the automatic file splitting option that is provided in ANSYS. See the Operations Guide for system
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p p p yspecifics.
Training Manual
Chapter 3 – Getting Started
H. Exiting ANSYSIN
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• Three ways to exit ANSYS:– Toolbar > QUIT
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– Utility Menu > File > Exit– Use the /EXIT command in the Input Window
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Training Manual
Chapter 3 – Getting Started
I. On-Line HelpIN
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• ANSYS uses an on-line documentation system to provide extensive help. O
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• You can get help on:– ANSYS commands– element types
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• You can also access:– Tutorials– Verification models
The ANSYS web site
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– The ANSYS web site
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Training Manual
Chapter 3 – Getting Started
…On-Line HelpIN
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• There are several ways to start the help system:– Launcher > Product Help O
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– Utility Menu > Help > Help Topics– Any dialog box > Help– Type HELP,name in the Input Window. Name is a command or
element name
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element name.– On a PC, Start > Programs > ANSYS 10.0 > Help > ANSYS Help
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Training Manual
Chapter 3 – Getting Started
…On-Line HelpIN
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• Pressing the Product Help button on the launcher brings up a help browser with:
– a navigational window containing Table of Contents Index and a Search Utility
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a navigational window containing Table of Contents, Index, and a Search Utility– a document window containing the help information.
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Training Manual
Chapter 3 – Getting Started
…On-Line HelpIN
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O• Use the Contents tab to browse to the item of interest. O
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Training Manual
Chapter 3 – Getting Started
…On-Line HelpIN
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• ANSYS also provides an HTML-based on-line tutorial.
The tutorial consists of
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• To access the tutorial, click on Utility Menu > Help > ANSYS Tutorials.
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Training Manual
Chapter 3 – Getting Started
…On-Line HelpIN
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• Demo:– Launch the help system from the launcher O
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– Bring up an Analysis Guide– Type “help,kplot” in the Input window– Search for the string “harmonic response” O
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Training Manual
Chapter 3 – Getting Started
J. WorkshopIN
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• Refer to your Workshop Supplement for instructions on:W3 Getting Started Workshop O
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Chapter 4
ANSYS Basics
Training Manual
Chapter 4 - ANSYS Basics
A. OverviewIN
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• Later in this course you will be using geometrical entities such as volumes, areas, lines and keypoints as well as FEA entities such as
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nodes and elements. This chapter introduces the following techniques used to display and manipulate those entities within the GUI:
– Plotting
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Plotting– Picking – Coordinate Systems– Select Logic N
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– Components and Assemblies
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Training Manual
Chapter 4 - ANSYS Basics
B. PlottingIN
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• It is often advantageous to plot only certain entities in the model.
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• Within the Utility Menu > Plot, you will see that geometric, finite element and other entities can be plotted.
/replotkplot
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kplotlplot
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Training Manual
Chapter 4 - ANSYS Basics
…PlottingIN
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• The PlotCtrls menu is used to control how the plot is displayed:
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– plot orientation– zoom– colors
symbols
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– symbols– annotation– animation– etc. N
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• Among these, changing the plot orientation (/VIEW) and zooming are the most commonly used functions
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most commonly used functions.
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Training Manual
Chapter 4 - ANSYS Basics
…PlottingIN
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• The default view for a model is the front view: looking down the +Z axis of the model. There are several methods to change the model view
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are several methods to change the model view.
• Use dynamic mode — a way to orient the plot dynamically using the Control key and mouse buttons
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buttons.– Ctrl + Left mouse button pans the model.– Ctrl + Middle mouse button:
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spins the model (about screen Z)– Ctrl + Right mouse button rotates the model:
about screen Xabout screen Y
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Note, the Shift-Right button on a two-button mouse is equivalent to the Middle mouse
P Z RCtrl
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ouse s equ a e t to t e dd e ousebutton on a three-button mouse.
Training Manual
Chapter 4 - ANSYS Basics
…PlottingIN
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• Use the Model Control Toolbar Icons to
h th i
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change the view.
• The Model Control Toolbar also includes O
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a dynamic rotate option.
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Dynamic Model Mode Icon performs same function as CTRL key.
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Training Manual
Chapter 4 - ANSYS Basics
…PlottingIN
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• A Dynamic Mode setting is also available using Pan-Zoom-Rotate .
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– The same mouse button assignments apply.
– On 3-D graphics devices, you can also dynamically orient the light source. O
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y y gUseful for different light source shading effects.
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When using 3-D driver
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Training Manual
Chapter 4 - ANSYS Basics
…PlottingIN
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• Other functions in the Pan-Zoom-Rotate dialog box:
Front +Z view, from (0,0,1)Back -Z view (0,0,-1)T Y i (0 1 0)
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– Preset views– Zoom-in on specific regions of
the model– Pan, zoom, or rotate in
Top +Y view (0,1,0)Bot -Y view (0,-1,0)Right +X view (1,0,0)Left -X view (-1,0,0)Iso Isometric (1,1,1) O
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Pan, zoom, or rotate in discrete increments (as specified by the Rate slider)
• Rotation is about the screen X Y Z coordinates
Obliq Oblique (1,2,3)WP Working plane view
Z B i ki t f
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screen X, Y, Z coordinates.– Fit the plot to the window– Reset everything to default
Zoom By picking center of a square
Box Zoom By picking two corners of a box
Win Zoom Same as Box Zoom, b t b i ti l
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• The majority of these options are available in the Model Control Toolbar.
but box is proportional to window.
Back Up “Unzoom” to previous zoom.
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Training Manual
Chapter 4 - ANSYS Basics
…PlottingIN
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• Many of the plotting features are also available by right mouse clicking on the graphics window.
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Training Manual
Chapter 4 - ANSYS Basics
C. PickingIN
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Picking
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• Picking allows you to identify model entities or locations by clicking in the Graphics Window. O
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• For example, you can create keypoints by picking locations in the Graphics Window and then pressing OK in the picker. Part 1
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Training Manual
Chapter 4 - ANSYS Basics
…PickingIN
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Two types of picking:
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• Retrieval picking– Picking existing entities for a
subsequent operation.– Allows you to enter entity numbers
Example ofLocational Picker
Example ofRetrieval Picker
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– Use the Pick All button to indicate all entities. N
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• Locational picking– Locating coordinates of a point,
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– Allows you to enter coordinates in the Picker Window.
• Note, you must hit the <Enter> key
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after entering information in the Picker Window, then hit [OK] or [Apply].
Training Manual
Chapter 4 - ANSYS Basics
…PickingIN
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Mouse button assignments for picking:
• Left mouse button picks (or unpicks) the entity
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• Left mouse button picks (or unpicks) the entity or location closest to the mouse pointer. Pressing and dragging allows you to “preview” the item being picked (or unpicked). Apply
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• Middle mouse button does an Apply. Saves the time required to move the mouse over to the Picker and press the Apply button. Use Shift-Right button on a two-button mouse
Pick TogglePick / Unpick
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Right button on a two-button mouse.
• Right mouse button toggles between pick and unpick mode. Part 1
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Note, the Shift-Right button on a two-button mouse is equivalent to the Middle mouse button on a three-button mouse.
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Cursor display:
Training Manual
Chapter 4 - ANSYS Basics
…PickingIN
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Cannot use the Command Input area to enter the values
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Type input followed by Enter, then [OK]
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Training Manual
Chapter 4 - ANSYS Basics
…PickingIN
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Hotspot locations for picking:
A d V l h h t t th t id f th
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• Areas and Volumes have one hotspot near the centroid of the solid model entity.
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pend.
• Why this is important: When you are required to “pick” an entity you must pick on the hotspot
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entity, you must pick on the hotspot.
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Training Manual
Chapter 4 - ANSYS Basics
…PickingIN
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• Demo:– Show locational picking by creating a few keypoints. Also show the
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use of middle and right mouse buttons.– Show retrieval picking by creating a few lines– Show “Loop” by creating an AL area– Show “Pick All” by deleting area only
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Show Pick All by deleting area only– Do KPLOT, LPLOT, etc. with and without numbering. Type in a few of
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Training Manual
Chapter 4 - ANSYS Basics
D. Coordinate SystemsIN
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The ANSYS program has several types of coordinate systems, each used for a different reason:
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• Global and local coordinate systems are used to locate geometry items (nodes, keypoints, etc.) in space.
• The display coordinate system determines the system in which geometry items are listed or displayed
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geometry items are listed or displayed.
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• The element coordinate system determines the orientation of material properties and element results data.
• The results coordinate system is used to transform nodal or Part 1Part 1Part 1Part 1Part 1Part 1
element results data to a particular coordinate system for listings, displays, or general postprocessing operations. (discussed in Chapter 13)
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Training Manual
Chapter 4 - ANSYS Basics
...Coordinate SystemsIN
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Global Coordinate System
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• The global reference system for the model.
• May be Cartesian (system 0), cylindrical (1), or spherical (2).– For example, location (0,10,0) in global Cartesian is the same as
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For example, location (0,10,0) in global Cartesian is the same as (10,90,0) in global Cylindrical.
NSYS
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 4 - ANSYS Basics
...Coordinate SystemsIN
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Local Coordinate System
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• A user-defined system at a desired location, with ID number 11 or greater. The location may be:
– At WP origin [CSWP]– At specified coordinates [LOCAL]
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At specified coordinates [LOCAL]– At existing keypoints [CSKP] or nodes [CS]
• May be Cartesian, cylindrical, or spherical. NSYS
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• May be rotated about X, Y, Z axes.
Part 1Part 1Part 1Part 1Part 1Part 1
YY11
X12Y12
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XX11
Training Manual
Chapter 4 - ANSYS Basics
...Coordinate SystemsIN
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Display Coordinate System
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• Can be changed to show and list entities in multiple coordinate systems
• Default is Global Cartesian ON
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ON
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• Used mostly for listing and plotting models in non-Cartesian systems. Is useful in only a few cases:
If li d i di l d i it li d i l di t t ( ith 1 0 0
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– If a cylinder is displayed in its cylindrical coordinate system (with a 1,0,0 view), it will be unrolled (developed) into a flat plane (with theta along the Y direction).
– DSYS,1 - List nodal coordinates in r,theta,z Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 4 - ANSYS Basics
...Coordinate SystemsIN
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Active Coordinate System
• Defaults to global Cartesian
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• Defaults to global Cartesian.
• Use CSYS command (or Utility Menu > WorkPlane > Change Active CS to) to change it to
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to– global Cartesian [csys,0]– global cylindrical [csys,1]– global spherical [csys 2] N
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global spherical [csys,2]– working plane [csys,4]– [csys,5] cylindrical coordinate system with Y as
the axis (X is in the global +X direction, local Y i i th l b l Z di ti d l l Z (th
Part 1Part 1Part 1Part 1Part 1Part 1
is in the global -Z direction, and local Z (the cylindrical axis) is in the global +Y direction)
– or a user-defined local coordinate system [csys, n]
February 7, 2006Inventory #002268
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• Used for geometry input and generation and Select Logic (discussed next)
Training Manual
Chapter 4 - ANSYS Basics
E. Select LogicIN
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• Suppose you wanted to do the following:– Plot all areas located in the second quadrant
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– Delete all arcs of radius 0.2 to 0.3 units– Apply a convection load on all exterior lines– Write out all nodes at Z=3.5 to a file
View results only in elements made of steel
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– View results only in elements made of steel
The common “theme” in these tasks is that they all operate on a subset of the model. N
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• Select Logic allows you to select a subset of entities and operate only on those entities. Part 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 4 - ANSYS Basics
…Select LogicIN
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• Three steps:– Select a subset
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– Perform operations on the subset– Reactivate the full set
• Most selecting tools are available in the Select Entitiesdialog box: Utility Menu > Select > Entities...
y
Criterion bywhich to select
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ON
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• Or you can use the xSEL family of commands: KSEL, LSEL ASEL VSEL NSEL
which to select
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LSEL, ASEL, VSEL, NSEL, ESEL Type of
selection
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 4 - ANSYS Basics
…Select LogicIN
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• Criterion by which to select:– By Num/Pick: to select based on entity numbers or by
i ki
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picking– Attached to: to select based on attached entities. For
example, select all lines attached to the current subset of areas. O
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ON
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ON
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– By Location: to select based on X,Y,Z location. For example, select all nodes at X=2.5. X,Y,Z are interpreted in the active coordinate system.
– By Attributes: to select based on material number, real NSYS
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NSYS
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By Attributes: to select based on material number, real constant set number, etc. Different attributes are available for different entities.
– Exterior: to select entities lying on the exterior.B R lt t l t titi b lt d t d l
Part 1Part 1Part 1Part 1Part 1Part 1
– By Results: to select entities by results data, e.g, nodal displacements.
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Training Manual
Chapter 4 - ANSYS Basics
…Select LogicIN
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• Type of selection– From Full: selects a subset from
th f ll t f titi
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the full set of entities.– Reselect: selects (again) a subset
from the current subset.– Also Select: adds another subset
Reselect
From Full
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ON
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ON
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to the current subset.– Unselect: deactivates a portion of
the current subset.Invert: toggles the active and
Also Select
Unselect NSYS
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– Invert: toggles the active and inactive subsets.
– Select None: deactivates the full set of entities.
Invert
Part 1Part 1Part 1Part 1Part 1Part 1
– Select All: reactivates the full set of entities.
Select None
Select All
February 7, 2006Inventory #002268
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Training Manual
Chapter 4 - ANSYS Basics
…Select LogicIN
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Operations on the Subset
T i l ti l i l d li ti
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• Typical operations are applying loads, listing results for the subset, or simply plotting the selected entities.
– The advantage of having a subset selected is that
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The advantage of having a subset selected is that you can use the [Pick All] button when the picker prompts you pick desired entities. Or you can use the ALL label when using commands.
– Note that most operations in ANSYS including the NSYS
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NSYS
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– Note that most operations in ANSYS, including the SOLVE command, act on the currently selected subset.
• Another “operation” is to assign a name to the
Part 1Part 1Part 1Part 1Part 1Part 1
• Another “operation” is to assign a name to the selected subset by creating a component(discussed in the next section).
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Training Manual
Chapter 4 - ANSYS Basics
…Select LogicIN
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Reactivating the Full Set
Aft ll d i d ti d th l t d b t
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• After all desired operations are done on the selected subset, you should reactivate the full set of entities.
– If all nodes and all elements are not active for solution, the solver will issue a warning to that effect. O
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ON
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ON
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g
• The easiest way to reactivate the full set is to select “everything”:– Utility Menu > Select > Everything
O i th d ALLSEL
NSYS
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NSYS
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– Or issue the command ALLSEL
You can also use the [Sele All] button in the Select Entities dialog box to reactivate each entity set separately. (Or issue KSEL,ALL; Part 1
Part 1Part 1Part 1Part 1Part 1
y p y ( , ;LSEL,ALL; etc.)
February 7, 2006Inventory #002268
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Training Manual
Chapter 4 - ANSYS Basics
F. ComponentsIN
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• Components are user-named subsets of entities. The name can then be used in dialog boxes or commands in place of entity numbers or the label ALL
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numbers or the label ALL.
• A group of nodes, or elements, or keypoints, or lines, or areas, or volumes can be defined as a component. Only one entity type is associated with a component
ON
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ON
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associated with a component.
• Components can be selected or unselected. When you select a component, you are actually selecting all of the entities in that
t
NSYS
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component.
• Component Manager is used to Create, Display, List and Select Components and A bli
Part 1Part 1Part 1Part 1Part 1Part 1
Assemblies.– Utility Menu > Select > Component Manager...
February 7, 2006Inventory #002268
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Training Manual
Chapter 4 - ANSYS Basics
…ComponentsIN
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• Creating a component– Utility Menu > Select > Component Manager
Click on the Create Component Icon
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– Click on the Create Component Icon• All of the currently selected entities will be included in the component, or you
can select (pick) the desired entities at this step.• Enter a name O
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ON
TO A
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– Up to 32 characters - letters, numbers, and _ (underscore) - are allowed– Beginning a component with _ (underscore) will make it a “hidden
component” and it cannot be picked from the list. This is NOT recommended. N
SYS N
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SYS ---PPPN
SYS N
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– Suggestion: Use the first letter of the name to indicate the entity type. For example, use N_HOLES for a node component.
Part 1Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 4 - ANSYS Basics
…ComponentsIN
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• Creating an assembly– Highlight the components for the assembly
Click on the Create Assembly Icon and enter a name
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– Click on the Create Assembly Icon and enter a name– Checking the box next to a component under the assembly number will also put a
component in an assembly
ON
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ON
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ON
TO A
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ANN
SYS N
SYS N
SYS ---PPPN
SYS N
SYS N
SYS ---PPPPart 1Part 1Part 1Part 1Part 1Part 1• In the Component Manager above, N_OUTER and N_INNER are in the
ASSM_NODES (ASM1) assembly. ASSM_NODES is in the ASSM_2 (ASM2) assembly.
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Training Manual
Chapter 4 - ANSYS Basics
G. WorkshopIN
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• Refer to your Workshop Supplement for instructions on:WS4 ANSYS Basics O
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ON
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February 7, 2006Inventory #002268
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Chapter 5
General Analysis Procedure
Training Manual
Chapter 5 - General Analysis Procedure
OverviewIN
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O• The objective of this chapter is outline a general analysis procedure to be used to solve a simulation. Regardless of O
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procedure to be used to solve a simulation. Regardless of the physics of the problem, the same general procedure can be followed.
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ON
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• The problem on the following slide will be used to demonstrate the general analysis procedure.
NSYS
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 5 - General Analysis Procedure
…OverviewIN
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Given: A 1” thick spherical aluminum tank with a height of 180” and radius of 100” tank is filled with water to a height of 80”. The l i ti E 10E6 P i 0 3
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aluminum properties are E = 10E6 Psi, ν = 0.3.
100 “
A
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1 “100 “100 “ A
Section Definition NSYS
NSYS
NSYS ---PPP
NSYS
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NSYS ---PPP80 “ 3163279.1
inlbf
=ρmσ
cσ Part 1Part 1Part 1Part 1Part 1Part 1
Stress ConventionSection A-A
February 7, 2006Inventory #002268
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Question: Predict the membrane stress distributions in the meridional (σm) and circumferential (σc) directions?
Stress Convention
Training Manual
Chapter 5 - General Analysis Procedure
…OverviewIN
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Every analysis involves four main steps:
• Preliminary Decisions
Preliminary Decisions O
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• Preliminary Decisions– Which analysis type?– What to model?– Which element type?
Decisions
ON
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ON
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ON
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• Preprocessing– Define Material– Create or import the model geometry
M h th t
Preprocessing
NSYS
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NSYS ---PPP
NSYS
NSYS
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– Mesh the geometry
• Solution– Apply loads Solution Part 1
Part 1Part 1Part 1Part 1Part 1
– Solve
• Postprocessing– Review results
February 7, 2006Inventory #002268
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– Check the validity of the solution Postprocessing
Training Manual
Chapter 5 - A. Preliminary Decisions
Which analysis type?IN
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y y
• The analysis type usually belongs to one of the following disciplines: O
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Structural Motion of solid bodies, pressure on solid bodies, or contact of solid bodies
Thermal Applied heat, high temperatures, or changes in temperature ON
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ON
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ON
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pElectromagnetic Devices subjected to electric currents (AC or DC),
electromagnetic waves, and voltage or charge excitation
Fluid Motion of gases/fluids or contained gases/fluids NSYS
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NSYS
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NSYS ---PPP
Fluid Motion of gases/fluids, or contained gases/fluidsCoupled-Field Combinations of any of the above
Part 1Part 1Part 1Part 1Part 1Part 1•The appropriate analysis type for this model is a structural analysis!
February 7, 2006Inventory #002268
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Training Manual
Chapter 5 - A. Preliminary Decisions
…What to model?IN
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O
• What should be used to model the geometry of the spherical tank?– Axisymmetry since the loading, material, and the boundary O
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conditions are symmetric. This type of model would provide the most simplified model.
– Rotational symmetry since the loading, material, and the boundary conditions are symmetric Advantage over
ON
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ON
TO A
NO
N TO
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ON
TO A
NO
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boundary conditions are symmetric. Advantage over axisymmetry: offers some results away from applied boundary conditions.
– Full 3D model is an option, but would not be an efficient choice NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
p ,compared to the axisymmetric and quarter symmetry models. If model results are significantly influenced by symmetric boundary conditions, this may be the only option. Part 1
Part 1Part 1Part 1Part 1Part 1An axisymmetric and a one-quarter symmetry (i.e. rotational
symmetry) model will be analyzed for this model!
February 7, 2006Inventory #002268
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Training Manual
Chapter 5 - A. Preliminary Decisions
…Which Element Type?IN
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O
y
• What element type should be used for the model of the spherical tank? O
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– Axisymmetric model:• Axisymmetric since 2-D section can be revolved to created 3D
geometry.• Linear due to small displacement assumption
ON
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ON
TO A
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N TO
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ON
TO A
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N TO
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• Linear due to small displacement assumption.– PLANE42 with KEYOPT(3) = 1
– Rotational symmetry model:• Shell since radius/thickness ratio > 10 N
SYS N
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SYS ---PPPN
SYS N
SYS N
SYS ---PPP
Shell since radius/thickness ratio 10• Linear due to small displacement assumption.• membrane stiffness only option since “membrane stresses” are
required. Part 1Part 1Part 1Part 1Part 1Part 1
– SHELL63 with KEYOPT(1) = 1• Since the meshing of this geometry will create SHELL63 elements
with shape warnings, a mid-side noded equation of the SHELL63 was used:
February 7, 2006Inventory #002268
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used:– SHELL93
Training Manual
Chapter 5 - B. Preprocessing
…Create the Solid ModelIN
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O
• A typical solid model is defined by volumes, areas, lines, and keypoints. O
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– Volumes are bounded by areas. They represent solid objects.– Areas are bounded by lines. They represent faces of solid objects, or
planar or shell objects.– Lines are bounded by keypoints. They represent edges of objects.
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
Lines are bounded by keypoints. They represent edges of objects.– Keypoints are locations in 3-D space. They represent vertices of
objects.
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPPPart 1
Part 1Part 1Part 1Part 1Part 1
Volumes Areas Lines & KeypointsFebruary 7, 2006
Inventory #0022685-8
Volumes Areas Lines & Keypoints
Training Manual
Chapter 5 - B. Preprocessing
…Create the Solid ModelIN
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INTR
O
• What geometry should be used to model the spherical tank?
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N TO
AN
ON
TO A
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N TO
AN
ON
TO A
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N TO
AN
ON
TO A
NNSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPPPart 1
Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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One-quarter Symmetry ModelAxisymmetric model
Training Manual
Chapter 5 - B. Preprocessing
Create the FEA ModelIN
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INTR
OIN
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INTR
O
• Meshing is the process used to “fill” the solid model with nodes and elements, i.e, to create the FEA model. O
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– Remember, you need nodes and elements for the finite element solution, not just the solid model. The solid model does NOT participate in the finite element solution.
ON
TO A
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N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
ANN
SYS N
SYS N
SYS ---PPPN
SYS N
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SYS ---PPP
meshing
Part 1Part 1Part 1Part 1Part 1Part 1Solid model FEA model
meshing
February 7, 2006Inventory #002268
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Training Manual
Chapter 5 - B. Preprocessing
…Create the FEA ModelIN
TRO
INTR
OIN
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TRO
INTR
O
• What would the mesh of the spherical tank look like?
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N TO
AN
ON
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NO
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AN
ON
TO A
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N TO
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ON
TO A
NNSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPPPart 1
Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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One-quarter Symmetry ModelAxisymmetric model
Training Manual
Chapter 5 - B. Preprocessing
Define MaterialIN
TRO
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Material Properties
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Chapter 5 – C. Solution
Define LoadsIN
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• There are five categories of loads:DOF Constraints Specified DOF values, such as displacements
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in a stress analysis or temperatures in a thermal analysis.
Concentrated Loads Point loads, such as forces or heat flow rates.Surface Loads Loads distributed over a surface, such as O
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,pressures or convections.
Body Loads Volumetric or field loads, such as temperatures (causing thermal expansion) or internal heat generation. N
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generation.Inertia Loads Loads due to structural mass or inertia, such
as gravity and rotational velocity.
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Chapter 5 – C. Solution
…Define LoadsIN
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• What are the loads on the spherical tank models?
* Tangential constraint used to allow comparison to Roarke closed form solution.
Training Manual
Chapter 5 - D. Postprocessing
Review ResultsIN
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• Postprocessing is the final step in the finite element analysis process. O
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• It is imperative that you interpret your results relative to the assumptions made during model creation and solution. O
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• ANSYS has two postprocessors:– POST1, the General Postprocessor, to review a single set of results
over the entire model. Part 1Part 1Part 1Part 1Part 1Part 1
– POST26, the Time-History Postprocessor, to review results at selected points in the model over time. Mainly used for transient and nonlinear analyses. (Not discussed in this course.)
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Chapter 5 - D. Postprocessing
…Review ResultsIN
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• What are the circumferential stress results in the spherical tank models? O
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One-quarter Symmetry ModelAxisymmetric model
Training Manual
Chapter 5 - D. Postprocessing
…Review ResultsIN
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• What are the meridional stress results in the spherical tank models? O
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One-quarter Symmetry ModelAxisymmetric model
Training Manual
Chapter 5 - D. Postprocessing
VerificationIN
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• It is always a good idea to do a “sanity check” and make sure that the solution is acceptable. O
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• What you need to check depends on the type of problem you are solving, but here are some typical questions to ask: O
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• Do the reaction forces balance the applied loads?
• Where is the maximum stress located?If it i t i l it h i t l d t t th
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– If it is at a singularity, such as a point load or a re-entrant corner, the value is generally meaningless.
– Are the stress values beyond the elastic limit?– If so, the load magnitudes may be wrong, or you may need to do a Part 1
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, g y g, y ynonlinear analysis.
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Chapter 5 - D. Postprocessing
…VerificationIN
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• How do the ANSYS results compare with Roarke?
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Membrane Stress Distributions for Axisymmetric Model
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Membrane Stress Distributions for Quarter Symmetry Model
• The purpose of this chapter is to review some preliminary modeling considerations, discuss how to import one’s geometry i t ANSYS d fi ll i t d h t t ’ t
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into ANSYS, and finally introduce how to create one’s geometry using ANSYS native commands.
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Training Manual
Chapter 6 – Creating the Solid Model
A. What to model?IN
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• Many modeling decisions must be made before building an analysis model: O
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– How much detail should be included?– Does symmetry apply?– Will the model contain stress singularities? O
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Training Manual
Chapter 6 – A. What to Model
…What to model?IN
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Details
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• Small details that are unimportant to the analysis should not be included in the analysis model. You can suppress such features before sending a model to ANSYS from a CAD system. O
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• For some structures, however, "small" details such as fillets or holes can be locations of maximum stress and might be quite important, depending on your analysis objectives. N
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Chapter 6 – A. What to Model
…What to model?IN
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Symmetry
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• Many structures are symmetric in some form and allow only a representative portion or cross-section to be modeled.
• The main advantages of using a symmetric model are: ON
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g g y– It is generally easier to create the model.– It allows you to make a finer, more detailed model and thereby obtain
better results than would have been possible with the full model. NSYS
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Chapter 6 – A. What to Model
…What to model?IN
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• To take advantage of symmetry, all of the following must be symmetric: O
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– Geometry– Material properties– Loading conditions O
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• There are different types of symmetry:– Axisymmetry– Rotational N
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– Planar or reflective– Repetitive or translational
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Chapter 6 – A. What to Model
…What to model?IN
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Axisymmetry
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• Symmetry about a central axis, such as in light bulbs, straight pipes, cones, circular plates, and domes.
• Plane of symmetry is the cross-section anywhere around the ON
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y y ystructure. Thus you are using a single 2-D “slice” to represent 360° — a real savings in model size!
• Loading is also assumed to be NSYS
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Loading is also assumed to be axisymmetric in most cases. However, if it is not, and if the analysis is linear, the loads can be separated into h i t f i d d t
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harmonic components for independent solutions that can be superimposed.
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Chapter 6 – A. What to Model
…What to model?IN
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Rotational symmetry
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• Repeated segments arranged about a central axis, such as in turbine rotors.
• Only one segment of the structure needs to be modeled. ON
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y g
• Loading is also assumed to be symmetric about the axis.
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Training Manual
Chapter 6 – A. What to Model
…What to model?IN
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Planar or reflective symmetry
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• One half of the structure is a mirror image of the other half. The mirror is the plane of symmetry.
• Loading may be symmetric or anti-symmetric about the plane of ON
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g y y y psymmetry.
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both reflective and Part 1Part 1Part 1Part 1Part 1Part 1
rotational symmetry
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Training Manual
Chapter 6 – A. What to Model
…What to model?IN
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Repetitive or translational symmetry
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• Repeated segments arranged along a straight line, such as a long pipe with evenly spaced cooling fins.
• Loading is also assumed to be “repeated” along the length of the ON
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Part 1Part 1Part 1Part 1Part 1This model illustrates both repetitive and reflective symmetry.
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Training Manual
Chapter 6 – A. What to Model
…What to model?IN
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• In some cases, only a few minor details will disrupt a structure's symmetry. You may be able to ignore such details (or treat them
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as being symmetric) in order to gain the benefits of using a smaller model. How much accuracy is lost as the result of such a compromise might be difficult to estimate. O
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Training Manual
Chapter 6 – A. What to Model
…What to model?IN
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Stress singularities
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• A stress singularity is a location in a finite element model where the stress value is unbounded (infinite). Examples:
– A point load, such as an applied force or moment– An isolated constraint point, where the reaction force behaves like a
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An isolated constraint point, where the reaction force behaves like a point load
– A sharp re-entrant corner (with zero fillet radius)
A th h d it i fi d t
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• As the mesh density is refined ata stress singularity, the stress valueincreases and never converges.
P σ = P/AAs A ⇒ 0, σ ⇒ ∞
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Chapter 6 – A. What to Model
…What to model?IN
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• Real structures do not contain stress singularities. They are a fiction created by the simplifying assumptions of the model. O
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• So how do you deal with stress singularities?– If they are located far away from the region of interest, you can simply
ignore them by deactivating the affected zone while reviewing results. ON
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g y g g– If they are located in the region of interest, you will need to take
corrective action, such as:• adding a fillet at re-entrant corners and rerunning the analysis. N
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• replacing a point force with an equivalent pressure load.• “spreading out” displacement constraints over a set of nodes.
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Training Manual
Chapter 6 – B. Importing Geometry
B. IGES ImportsIN
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• Importing an IGES file– Utility Menu > File > Import > IGES… O
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– the two methods, No Defeaturing and Defeaturing– the Merge, Solid, and Small options
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Chapter 6 – B. Importing Geometry
Connection ProductsIN
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• IGES importing works quite well, but because of the dual translation process — CAD ⌫ IGES ⌫ ANSYS — there are many
h 100% t l ti i t hi d
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cases when a 100% translation is not achieved.
• ANSYS Connection products help overcome this problem by directly reading the “native” part files produced by the CAD O
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y g p p ypackage:
– Connection for Pro/ENGINEER (“Pro/E” for short)– Connection for Unigraphics (“UG” for short) N
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– Connection for SAT– Connection for Parasolid– Connection for CATIA Part 1
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• To use a connection product, you need to purchase the appropriate license.
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Training Manual
Chapter 6 – B. Importing Geometry
…Connection ProductsIN
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• Connection for SAT– Reads .sat file produced by CAD packages that use the ACIS modeler. O
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– Does not require ACIS software.– Utility Menu > File > Import > SAT...– Or ~satin O
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Option to read only selected geometry types
Part 1Part 1Part 1Part 1Part 1Part 1Defeaturing option available
No Defeaturing is default
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Training Manual
Chapter 6 – B. Importing Geometry
…Connection ProductsIN
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• Connection for Parasolid– Reads .x_t or .xmt_txt file produced by CAD packages that use the
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Parasolid modeler.– Does not require Parasolid software.– Utility Menu > File > Import > PARA...– Or ~parain
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No Defeaturing is default
Option to scale geometry
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Training Manual
Chapter 6 – B. Importing Geometry
…Connection ProductsIN
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• The importing procedure from other CAD systems is similar. See the Connection Users Guide for detailed instructions for each CAD system. O
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• Supported CAD systems on Windows:
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• Supported CAD systems on UNIX:
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Training Manual
Chapter 6 – B. Importing Geometry
WorkshopsIN
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• Refer to your Workshop Supplement for instructions on:W6A. Importing Geometry – IGES Import O
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W6B. Importing Geometry – SAT Part ImportW6C. Importing Geometry – SAT Assembly ImportW6D. Importing Geometry – Parasolid Part ImportW6E Importing Geometry Parasolid Assembly Import
• Importing geometry is convenient, but sometimes you may need to create it in ANSYS. Some possible reasons: O
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– You may need to build a parametric model — one defined in terms of variables for later use in design optimization or sensitivity studies.
– The geometry may not be available in a format ANSYS can read.– The Connection product you need may not be available on your
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The Connection product you need may not be available on your computer platform.
– You may need to modify or add geometry to an imported part or assembly. N
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• ANSYS has an extensive set of geometry creation tools, which we will introduce next.
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Chapter 6 – C. ANSYS Native Commands
DefinitionsIN
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• Solid Modeling can be defined as the process of creating solid models. O
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• Definitions:– A solid model is defined by volumes, areas, lines,
and keypoints.
Volumes
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yp– Volumes are bounded by areas, areas by lines, and
lines by keypoints.– Hierarchy of entities from low to high:
k i t li l
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keypoints < lines < areas < volumes – You cannot delete an entity if a higher-order entity
is attached to it.
Lines &Keypoints
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• Also, a model with just areas and below, such as a shell or 2-D plane model, is still considered a solid model in ANSYS terminology.
Keypoints
Lines
Areas
Volumes
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Keypoints
Training Manual
Chapter 6 – C. ANSYS Native Commands
…DefinitionsIN
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• There are two approaches to creating a solid model:– Top-down O
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– Bottom-up
• Top-down modeling starts with a definition of volumes (or areas), which are then combined in some fashion to create the final O
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which are then combined in some fashion to create the final shape.
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Chapter 6 – C. ANSYS Native Commands
…DefinitionsIN
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• Bottom-up modeling starts with keypoints, from which you “build up” lines, areas, etc. O
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• You may choose whichever approach best suits the shape of the model, and also freely combine both methods.
Part 1Part 1Part 1Part 1Part 1Part 1
• The top-down and bottom-up modeling approaches are not discussed here, but are described in detail in the Appendix.
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Training Manual
Chapter 6 – D. ANSYS Native Geometry Creation
D. Working PlaneIN
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• The “WP” in the prompts and in the picker stands for Working Plane — a movable, 2-D reference plane used to locate and orient
i iti
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primitives.– By default, the WP origin coincides with the global origin, but you can
move it and/or rotate it to any desired position.– By displaying a grid, you can use the WP as a “drawing tablet.” O
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y p y g g , y g– WP is infinite despite the grid settings.
NSYS
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NSYS
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NSYS ---PPPWY
WXWY Part 1Part 1Part 1Part 1Part 1Part 1
X2
X1 Y2
Y1 WP (X Y)
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WXY1 WP (X,Y)
Training Manual
Chapter 6 – D. ANSYS Native Geometry Creation
…Working PlaneIN
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• All working plane controls are in Utility Menu > WorkPlane.
gO
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• The WP Settings menu controls the following:
– WP display - triad only (default), grid only, or
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WP display triad only (default), grid only, or both.
– Snap - allows you to pick locations on the WP easily by “snapping” the cursor to the nearest grid point N
SYS N
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grid point.– Grid spacing - the distance between grid
lines.– Grid size - how much of the (infinite) working
l i di l d
Part 1Part 1Part 1Part 1Part 1Part 1
plane is displayed.
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Training Manual
Chapter 6 – D. ANSYS Native Geometry Creation
…Working PlaneIN
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• You can move the working plane to any desired position using th Off t d Ali
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the Offset and Align menus.– Offset WP by Increments…
• Use the push buttons (with increment set by slider).
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increment set by slider).• Or type in the desired
increments.• Or use dynamic mode N
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(similar to pan-zoom-rotate).
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 6 – D. ANSYS Native Geometry Creation
…Working PlaneIN
TRO
INTR
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– Offset WP to >This simply “translates” the WP, maintaining its current orientation to
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maintaining its current orientation, to the desired destination, which can be:
• Existing keypoint(s). Picking multiple keypoints moves WP to O
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their average location.• Existing node(s).• Coordinate location(s).
Gl b l i i
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• Global origin.• Origin of the active coordinate
system (discussed later). Part 1Part 1Part 1Part 1Part 1Part 1
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Chapter 6 – D. ANSYS Native Geometry Creation
…Working PlaneIN
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– Align WP with >This reorients the WP.
gO
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• For example, Align WP with Keypointsprompts you to pick 3 keypoints -one at the origin, one to define the X-axis, and one to define the X-Y O
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plane.• To return the WP to its default
position (at global origin, on global X-Y plane), click on Align WP with > N
SYS N
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p ), gGlobal Cartesian.
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Training Manual
Chapter 6 – D. ANSYS Native Geometry Creation
…Working PlaneIN
TRO
INTR
OIN
TRO
INTR
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TRO
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O
• Demo:– Clear the database
Display WP and create a few keypoints by picking Note the coordinates
gO
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– Display WP and create a few keypoints by picking. Note the coordinates displayed in the picker.
– Turn on the grid, change spacing, and activate snap.– Create more keypoints. Note how the cursor snaps to grid points.
Define 2 rectangles one by picking corners and one by dimensions
ON
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ON
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ON
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– Define 2 rectangles — one by picking corners and one by dimensions.– Now offset WP to average of a few keypoints, then rotate in-plane by 30º.– Define 2 more rectangles by picking and by dimensions. Note the change in
rectangle orientation.Align WP with global origin then define some 3 D primitives Use picking as well
NSYS
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NSYS
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– Align WP with global origin, then define some 3-D primitives. Use picking as well as “By dimensions.”
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 6 – E. ANSYS Coordinate Systems
Active Coordinate SystemIN
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Active Coordinate System
D f lt t l b l C t i
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• Defaults to global Cartesian.
• Use CSYS command (or Utility Menu > WorkPlane > Change Active CS to) to O
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g )change it to
– global Cartesian [csys,0]– global cylindrical [csys,1] N
SYS N
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– global spherical [csys,2]– working plane [csys,4]– or a user-defined local coordinate
system [csys, n] Part 1Part 1Part 1Part 1Part 1Part 1
system [csys, n]
Each of these systems is explained next.
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Training Manual
Chapter 6 – E. ANSYS Coordinate Systems
Global Coordinate SystemIN
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Global Coordinate System
Th l b l f t f th d l
yO
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• The global reference system for the model.
• May be Cartesian (system 0), cylindrical (1), or spherical (2).– For example, location (0,10,0) in global Cartesian is the same as
ON
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For example, location (0,10,0) in global Cartesian is the same as (10,90,0) in global Cylindrical.
NSYS
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Part 1Part 1Part 1Part 1Part 1
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Chapter 6 – E. ANSYS Coordinate Systems
Local Coordinate SystemIN
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Local Coordinate System
A d fi d t t d i d l ti ith ID
yO
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• A user-defined system at a desired location, with ID number 11 or greater. The location may be:
– At WP origin [CSWP]– At specified coordinates [LOCAL]
ON
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ON
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ON
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At specified coordinates [LOCAL]– At existing keypoints [CSKP] or nodes [CS]
• May be Cartesian, cylindrical, or spherical. NSYS
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NSYS
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• May be rotated about X, Y, Z axes.
Part 1Part 1Part 1Part 1Part 1Part 1
YY11
X12Y12
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XX11
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Chapter 6 – E. ANSYS Coordinate Systems
Working Plane Coordinate SystemIN
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Working Plane Coordinate System
Att h d t th ki l
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• Attached to the working plane.
• Used mainly to locate and orient solid model primitives. ON
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ON
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ON
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• You can also use the working plane to define keypoints by picking.
NSYS
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Part 1Part 1Part 1Part 1Part 1
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Chapter 6 – E. ANSYS Coordinate Systems
CSYSIN
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• You can define any number of coordinate systems, but only one may be active at any given time
OD
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may be active at any given time.
• Several geometry items are affected by the coordinate system [CSYS] that is active at the time they are defined:
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ON
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ON
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is active at the time they are defined:– Keypoint and node locations– Line curvature– Area curvature
G ti d “filli ” f k i t
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– Generation and “filling” of keypoints and nodes
– Etc.
• The graphics window title shows the
Part 1Part 1Part 1Part 1Part 1Part 1
• The graphics window title shows the active system.
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Areas created between keypoints at (1,0,0), (0,1,0), & (0,0,1)
Training Manual
Chapter 6 – E. ANSYS Coordinate Systems
Active Coordinate System DemoIN
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• Demo:– Clear the database
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– Create 5 keypoints at (1,2), (3,2), (4,0), (1,1.5), (2.5,0)– Switch to CSYS,1 and create a line “in active CS” between KP4 & KP5– Switch back to CSYS,0 and create an area “through KP’s.” Notice that
the remaining lines were automatically generated lines all of them
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ON
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the remaining lines were automatically generated lines, all of them straight.
– Define two circles:• 0.3R, centered at (2.25,1.5) N
SYS N
SYS N
SYS ---PPPN
SYS N
SYS N
SYS ---PPP
• 0.35R, centered at (3.0,0.6)– Subtract the two circles from base area. (We have used a combination
of bottom-up and top-down modeling.)Save as r db
Part 1Part 1Part 1Part 1Part 1Part 1
– Save as r.db
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Chapter 7
Create Finite Element Model
Training Manual
Chapter 7 – Creating the Finite Element Model
A. OverviewIN
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• The purpose of this chapter is to discuss the meshing element attributes, various means to create a mesh in ANSYS, and finally h t i t ’ fi it l t d l di tl i t ANSYS
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how to import one’s finite element model directly into ANSYS. Recall, ANSYS does not use the solid model in the solution of the model, rather it needs to use finite elements. O
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…OverviewIN
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• Meshing is the process used to “fill” the solid model with nodes and elements, i.e, to create the FEA model. O
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– Remember, you need nodes and elements for the finite element solution, not just the solid model. The solid model does NOT participate in the finite element solution.
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meshing
Part 1Part 1Part 1Part 1Part 1Part 1Solid model FEA model
meshing
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Training Manual
Chapter 7 – Creating the Finite Element Model
B. Element AttributesIN
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• There are three steps to meshing:– Define element attributes O
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– Specify mesh controls– Generate the mesh
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• Element attributes are characteristics of the finite element model that you must establish prior to meshing. They can include:
– Element types NSYS
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NSYS
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NSYS ---PPP
– Real constants– Material properties– Section properties Part 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
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OIN
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O
Element Type
Th l t t i i t t h i th t d t i th
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• The element type is an important choice that determines the following element characteristics:
– Degree of Freedom (DOF) set. A thermal element type, for example, has one dof: TEMP, whereas a structural element type may have up to O
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, yp y psix dof: UX, UY, UZ, ROTX, ROTY, ROTZ.
– Element shape -- brick, tetrahedron, quadrilateral, triangle, etc.– Dimensionality -- 2-D (X-Y plane only), or 3-D.
A d di l t h li d ti
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
– Assumed displacement shape -- linear vs. quadratic.
• ANSYS has a “library” of over 170 element types from which you can choose. Details on how to choose the “correct” element type Part 1
Part 1Part 1Part 1Part 1Part 1
ypwill be presented later. For now, let’s see how to define an element type.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
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OIN
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Element category
ANSYS ff diff t t i f l t S f th
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• ANSYS offers many different categories of elements. Some of the commonly used ones are:
– Line elements– Shells
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ON
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Shells– 2-D solids– 3-D solids
NSYS
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NSYS ---PPPPart 1
Part 1Part 1Part 1Part 1Part 1
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Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
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OIN
TRO
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• Line elements:– Beam elements are used to model bolts, tubular members, C-sections,
l i l l d b h l b d
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angle irons, or any long, slender members where only membrane and bending stresses are needed.
– Link elements are used to model springs, bolts, preloaded bolts, and truss members. O
N TO
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ON
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ON
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– Spring (combination) elements are used to model springs, bolts, or long slender parts, or to replace complex parts by an equivalent stiffness.
NSYS
NSYS
NSYS ---PPP
NSYS
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NSYS ---PPPPart 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
• Shell elements:– Used to model thin panels or curved surfaces. O
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– The definition of “thin” depends on the application, but as a general guideline, the major dimensions of the shell structure (panel) should be at least 10 times its thickness.
ON
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ON
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AN
ON
TO A
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N TO
ANN
SYS N
SYS N
SYS ---PPPN
SYS N
SYS N
SYS ---PPPPart 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
• 2-D Solid elements:– Used to model a cross-section of solid objects. O
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– Must be modeled in the global Cartesian X-Y plane.– All loads are in the X-Y plane, and the response (displacements) are
also in the X-Y plane.– Element behavior may be one of the following:
ON
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Element behavior may be one of the following:• plane stress• plane strain• generalized plain strain N
• Plane stress assumes zero stress in the Z direction. O
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– Valid for components in which the Z dimension is smaller than the X and Y dimensions.
– Z-strain is non-zero.
Y
XZ
ON
TO A
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N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
– Optional thickness (Z direction) allowed.
– Used for structures such as flat plates subjected to in-plane loading or thin
X Z
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
subjected to in-plane loading, or thin disks under pressure or centrifugal loading.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
• Plane strain assumes zero strain in the Z direction. O
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– Valid for components in which the Z dimension is much larger than the X and Y dimensions.
– Z-stress is non-zero.– Used for long constant cross-section structures Z
ON
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N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
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– Used for long, constant cross-section structures such as structural beams.
Y X
Z
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPPPart 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
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TRO
INTR
O
• Generalized Plane Strain assumes a finite deformation domain length in the Z direction, as opposed to the infinite value assumed O
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for standard plane strain. – Gives more practical results for deformation problems where the Z-
direction dimension is not long enough.– Gives users a more efficient way to simulate certain 3-D deformations
ON
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ON
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ON
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– Gives users a more efficient way to simulate certain 3-D deformations using 2-D element options.
– Option is a feature developed for PLANE182 and PLANE183. – The deformation domain or structure N
SYS N
SYS N
SYS ---PPPN
SYS N
SYS N
SYS ---PPP
is formed by extruding a plane area along a curve with a constant curvature.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
• Axisymmetry assumes that the 3-D model and its loading can be generated by revolving a 2-D
ti 360° b t th Y i
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section 360° about the Y axis.– Axis of symmetry must coincide with the global Y
axis.– Negative X coordinates are not permitted. O
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g p– Y direction is axial, X direction is radial, and Z
direction is circumferential (hoop) direction.– Hoop displacement is zero; hoop strains and
stresses are usually very significant
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stresses are usually very significant.– Used for pressure vessels, straight pipes, shafts,
etc.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
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OIN
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O
• Axisymmetric harmonic is a special case of axisymmetry where the loads can be non-axisymmetric. O
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– The non-axisymmetric loading is decomposed into Fourier series components, applied and solved separately, and then combined later. No approximation is introduced by this simplification!
– Used for non-axisymmetric loads such as torque on a shaft. ON
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y q
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
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OIN
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• 3-D Solid elements:– Used for structures which, because of geometry, materials, loading, or
d t il f i d lt t b d l d ith i l l t
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detail of required results, cannot be modeled with simpler elements. – Also used when the model geometry is transferred from a 3-D CAD
system, and a large amount of time and effort is required to convert it to a 2-D or shell form. O
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Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
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OIN
TRO
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O
Element Order
El t d f t th l i l d f th l t’
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• Element order refers to the polynomial order of the element’s shape functions.
• What is a shape function? ON
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p– It is a mathematical function that gives the “shape” of the results
within the element. Since FEA solves for DOF values only at nodes, we need the shape function to map the nodal DOF values to points within the element N
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within the element.– The shape function represents assumed behavior for a given element.– How well each assumed element shape function matches the true
behavior directly affects the accuracy of the solution, as shown on the t lid
Part 1Part 1Part 1Part 1Part 1Part 1
next slide.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
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OIN
TRO
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O
Quadratic distribution of
Linear approximation (Poor Results) O
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Quadratic distribution of DOF values
Actual quadratic curve O
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NNSYS
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NSYS
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(Best Results)
Linear approximation with multiple elements
(Better Results)
Part 1Part 1Part 1Part 1Part 1Part 1
(Best Results)(Better Results)
February 7, 2006Inventory #002268
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
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O
• When you choose an element type, you are implicitly choosing and accepting the element shape function assumed for that
l t t Th f h k th h f ti i f ti
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element type. Therefore, check the shape function information before you choose an element type.
• Typically, a linear element has only corner nodes, whereas a ON
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yp y, y ,quadratic element also has midside nodes.
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
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OIN
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O
Linear elements
• Can support only a linear variation of
Quadratic elements
• Can support a quadratic variation of
OD
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pp ydisplacement and therefore (mostly) only a constant state of stress within a single element.
Highly sensitive to element distortion
pp qdisplacement and therefore a linear variation of stress within a single element.
Can represent curved edges and
ON
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• Highly sensitive to element distortion.
• Acceptable if you are only interested in nominal stress results.
• Can represent curved edges and surfaces more accurately than linear elements. Not as sensitive to element distortion.
NSYS
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• Need to use a large number of elements to resolve high stress gradients.
• Recommended if you are interested in highly accurate stresses.
• Give better results than linear elements in many cases with fewer
Part 1Part 1Part 1Part 1Part 1Part 1
elements, in many cases with fewer number of elements and total DOF.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
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O
• Notes:– For shell models, the difference between linear and quadratic
l t i t d ti f lid d l Li h ll
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elements is not as dramatic as for solid models. Linear shells are therefore usually preferred.
– Besides linear and quadratic elements, a third kind is available, known as p-elements. P-elements can support anywhere from a quadratic to O
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an 8th-order variation of displacement within a single element and include automatic solution convergence controls.
NSYS
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
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TRO
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O
Mesh Density
Th f d t l i f FEA i th t th b f
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• The fundamental premise of FEA is that as the number of elements (mesh density) is increased, the solution gets closer and closer to the true solution. O
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• However, solution time and computer resources required also increase dramatically as you increase the number of elements.
• The objectives of the analysis usually decide which way the slider
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• The objectives of the analysis usually decide which way the slider bar below should be moved.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
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O
• Stress Analyses:– If you are interested in highly accurate stresses: O
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• A fine mesh will be needed, omitting no geometric details at any location in the structure where such accuracy is needed.
• Stress convergence should be demonstrated.Any simplification anywhere in the model might introduce
ON
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ON
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• Any simplification anywhere in the model might introduce significant error.
– If you are interested in deflections or nominal stresses:• A relatively coarse mesh is sufficient. N
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y• Small geometry details may be omitted.
• Thermal Analyses: Part 1Part 1Part 1Part 1Part 1Part 1
– Small details can usually be omitted, but since many thermal analyses are followed by a stress analysis, stress considerations generally dictate the detail of the model.
– Mesh density is usually determined by expected thermal gradients. A
February 7, 2006Inventory #002268
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y y y gfine mesh is required for high thermal gradients, whereas a coarse mesh may be sufficient for low gradients.
Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
• To define an element type:– Main Menu > Preprocessor >
El t T > Add/Edit/D l t
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Element Type > Add/Edit/Delete• [Add] to add new element type• Choose the desired type
(such as SOLID92) and press
ON
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ON
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ON
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(such as SOLID92) and press OK
• [Options] to specify additional element options
O th ET d
NSYS
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– Or use the ET command:• et,1,solid92
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
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O
• Notes:– Setting preferences to the desired discipline (Main Menu > Preferences)
ill h l th l t t lid f th t di i li
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will show only the element types valid for that discipline.– You should define the element type early in the preprocessing phase
because many of the menu choices in the GUI are filtered out based on the current DOF set. For example, if you choose a structural O
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element type, thermal load choices will not be not shown at all.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
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O
Real Constants and Section Properties:
OD
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• Used for geometric properties that cannot be completely defined by the element’s geometry. For example:
– A beam element is defined by a line joining two nodes. This defines only the length of the beam To specify the beam’s cross-sectional
ON
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only the length of the beam. To specify the beam s cross-sectional properties, such as the area, moment of inertia or dimensions, you need to use real constants or section properties.
– A shell element is defined by a quadrilateral or triangular area. This defines only the surface area of the shell To specify the shell
NSYS
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defines only the surface area of the shell. To specify the shell thickness or layers, you need to use real constants or section properties.
– Most 3-D solid elements do not require a real constant since the l t t i f ll d fi d b it d
Part 1Part 1Part 1Part 1Part 1Part 1
element geometry is fully defined by its nodes.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
• To define real constants:– Main Menu > Preprocessor > Real
C t t
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Constants• [Add] to add a new real constant
set.• If multiple element types have
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ON
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If multiple element types have been defined, choose the element type for which you are specifying real constants.Then enter the real constant
NSYS
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• Then enter the real constant values.
– Or use the R family of commands.
Part 1Part 1Part 1Part 1Part 1Part 1
• Different element types require different real constants. Check the Elements Manual, available on-line, for details
February 7, 2006Inventory #002268
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for details.
Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
• To define section properties:– Main Menu > Preprocessor > Sections
Abilit t I t S ti
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• Ability to Import Sections• Beam, Shell and Pretension sections can
be created.• Or use the SECxxx family of commands
ON
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ON
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ON
TO A
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Or use the SECxxx family of commands.
• Different element types require different section properties. See the Elements M l f d t il
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Manual for details.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Element AttributesIN
TRO
INTR
OIN
TRO
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OIN
TRO
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O
Material Properties
E l i i t i l t i t Y ’
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• Every analysis requires some material property input: Young’s modulus EX for structural elements, thermal conductivity KXX for thermal elements, etc. O
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• Refer to Chapter 8 for details on the two ways to define material properties.
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
C. Multiple Element AttributesIN
TRO
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OIN
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O
• Most FEA models have multiple attributes. For example, the silo shown here has two element types, three real constant sets, and two materials. O
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TYPE 1 = shell
ON
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ON
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ON
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MAT 1 = concreteMAT 2 = steel
TYPE 1 shellTYPE 2 = beam
NSYS
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REAL 1 = 3/8” thicknessREAL 2 = beam propertiesREAL 3 = 1/8” thickness Part 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Multiple Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
• Whenever you have multiple TYPEs, REALs, MATs and SECNUMs, you need to make sure that each element is assigned the proper
tt ib t Th th t d thi
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attributes. There are three ways to do this:– Assign attributes to the solid model entities before meshing– Activate a “global” setting of TYPE, REAL, MAT and SECNUM before
meshing ON
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ON
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ON
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g– Modify element attributes after meshing
• If no assignments are made, ANSYS uses default settings of TYPE 1 REAL 1 MAT 1 d SECNUM 1 f ll l t i th
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TYPE=1, REAL=1, MAT=1 and SECNUM=1 for all elements in the model. Note, the current active setting dictates mesh operation.
• Good practice is to use the same number for TYPE, REAL, MAT Part 1Part 1Part 1Part 1Part 1Part 1
p , ,and SECNUM for a given part.
February 7, 2006Inventory #002268
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Multiple Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
Assigning Attributes to the Solid Model
1 Define all necessary element types materials and
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1. Define all necessary element types, materials, and real constant sets.
2. Then use the “Element Attributes” section of the MeshTool (Main Menu > Preprocessor > MeshTool):
ON
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ON
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ON
TO A
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MeshTool (Main Menu > Preprocessor > MeshTool):– Choose entity type and press the SET button.– Pick the entities to which you want to assign
attributes.Set the appropriate attributes in the subsequent N
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– Set the appropriate attributes in the subsequent dialog box.
Or select the desired entities and use the VATT, AATT, LATT, or KATT command. Part 1
Part 1Part 1Part 1Part 1Part 1
AATT, LATT, or KATT command.
3. When you mesh an entity, its attributes are automatically transferred to the elements.
February 7, 2006Inventory #002268
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Multiple Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
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O
Using Global Attribute Settings
1 Define all necessary element types
OD
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1. Define all necessary element types, materials, real constant sets and section numbers
2 Then use the “Element Attributes” section
ON
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ON
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ON
TO A
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2. Then use the Element Attributes section of the MeshTool (Main Menu > Preprocessor > MeshTool):
– Choose Global and press the SET button.Activate the desired combination of attributes
NSYS
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– Activate the desired combination of attributes in the “Meshing Attributes” dialog box. We refer to these as the active TYPE, REAL, MAT and SECNUM settings. Part 1
Part 1Part 1Part 1Part 1Part 1
Or use the TYPE, REAL, MAT and SECNUMcommands.
3. Mesh only those entities to which the above
February 7, 2006Inventory #002268
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ysettings apply.
Training Manual
Chapter 7 – Creating the Finite Element Model
…Multiple Element AttributesIN
TRO
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OIN
TRO
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OIN
TRO
INTR
O
Modifying Element Attributes
1 Define all necessary element types materials and real constant
OD
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1. Define all necessary element types, materials, and real constant sets.
2. Activate the desired combination of TYPE, REAL, MAT, and SECNUM settings
ON
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ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
SECNUM settings:– Main Menu > Preprocessor > Meshing > Mesh Attributes > Default Attribs– Or use the TYPE, REAL, MAT and SECNUM commands
NSYS
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NSYS
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3. Modify the attributes of only those elements to which the above settings apply:
– Issue EMODIF,PICK or choose Main Menu > Preprocessor > Modeling > Move/Modify > Elements > Modify Attrib Part 1
Part 1Part 1Part 1Part 1Part 1
y y– Then pick the desired elements
4. In the subsequent dialog box,set attributes to “All to current.”
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set attributes to All to current.
Training Manual
Chapter 7 – Creating the Finite Element Model
…Multiple Element AttributesIN
TRO
INTR
OIN
TRO
INTR
OIN
TRO
INTR
O
Some points to keep in mind:
• You can verify element attributes by activating
OD
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OD
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• You can verify element attributes by activating attribute numbering:
– Utility Menu > PlotCtrls > Numbering– Or /PNUM,attr,ON, where attr may be TYPE,
REAL MAT or SECNUM
ON
TO A
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N TO
AN
ON
TO A
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N TO
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ON
TO A
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N TO
AN
REAL, MAT or SECNUM
NSYS
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• Element attributes assigned directly to solid model entities will override the default attribute pointers. Part 1
Part 1Part 1Part 1Part 1Part 1
• By assigning attributes to solid model entities, you can avoid having to reset attributes in the middle of meshing operations. This is advantageous because ANSYS meshing algorithms are most efficient when meshing all entities at once.
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g
• Clearing a solid model entity of its mesh will not delete attribute assignments.
Training Manual
Chapter 7 – Creating the Finite Element Model
…Multiple Element AttributesIN
TRO
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OIN
TRO
INTR
OIN
TRO
INTR
O
• Demo:– Resume ribgeom.db O
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– List element types, real constants, and materials. One of each has been defined.
– Bring up MeshTool, choose area attributes, and press Set– Pick the single area show the Area Attributes dialog box and press
ON
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AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
Pick the single area, show the Area Attributes dialog box, and press OK. (There is only one set of attributes, but this illustrates the general procedure.)
NSYS
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
D. WorkshopIN
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INTR
O
• Refer to your Workshop Supplement for instructions on:W7A. Silo O
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TIOON
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ON
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ON
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ANN
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Training Manual
Chapter 7 – Creating the Finite Element Model
E. Controlling Mesh DensityIN
TRO
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OIN
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OIN
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O
• ANSYS provides many tools to control mesh density, both on a global and local level:
g yO
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– Global controls• SmartSizing• Global element sizing
D f lt i i
ON
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N TO
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ON
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ON
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• Default sizing– Local controls
• Keypoint sizing• Line sizing N
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• Line sizing• Area sizing
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Chapter 7 – Creating the Finite Element Model
…Controlling Mesh DensityIN
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SmartSizing
D t i l t i b i i di i i ll li
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• Determines element sizes by assigning divisions on all lines, taking into account curvature of the line, its proximity to holes and other features, and element order. O
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ON
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N TO
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ON
TO A
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• SmartSizing is off by default, but is recommended for free meshing. It does not affect mapped meshing. (Free meshing vs. mapped meshing will be discussed later.) N
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Chapter 7 – Creating the Finite Element Model
…Controlling Mesh DensityIN
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• To use SmartSizing:– Bring up the MeshTool (Main Menu > Preprocessor >
M hi M hT l) t S tSi i d t th
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Meshing > MeshTool), turn on SmartSizing, and set the desired size level.
• Or use SMRT,level• Size level ranges from 1 (very fine) to 10 (very
ON
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ON
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N TO
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ON
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Size level ranges from 1 (very fine) to 10 (very coarse). Defaults to 6.
– Then mesh all volumes (or all areas) at once, rather than one-by-one. N
SYS N
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Chapter 7 – Creating the Finite Element Model
…Controlling Mesh DensityIN
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• Examples of different SmartSize levels are shown here for a tetrahedron mesh
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tetrahedron mesh.
• Advanced SmartSize controls, such as mesh expansion and transition factors are available on the SMRT
ON
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ON
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ON
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factors, are available on the SMRTcommand or:
Main Menu > Preprocessor > Meshing > Size Cntrls > SmartSize > Adv Opts N
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• You can turn off SmartSizing using the MeshTool or by issuing smrt,off.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Controlling Mesh DensityIN
TRO
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Global Element Sizing
• Allows you to specify a maximum element edge length
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Allows you to specify a maximum element edge length for the entire model (or number of divisions per line):
– ESIZE,SIZE– or Main Menu > Preprocessor > Meshing > MeshTool; then
select “Size Controls”, “Global” ,and [Set] ON
TO A
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N TO
AN
ON
TO A
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N TO
AN
ON
TO A
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N TO
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– or Main Menu > Preprocessor > Meshing > Size Cntrls > ManualSize > Global > Size
• Can be used by itself or in conjunction with SmartSizing N
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SmartSizing.– Using ESIZE by itself (SmartSizing off) will
result in a uniform element size throughout the volume (or area) being meshed.
– With SmartSizing on, ESIZE acts as a “guide,”
Part 1Part 1Part 1Part 1Part 1Part 1
With SmartSizing on, ESIZE acts as a guide, but the specified size may be overridden to accommodate line curvature or proximity to features.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Controlling Mesh DensityIN
TRO
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Default Sizing
If d ’t if t l ANSYS d f lt i i hi h
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• If you don’t specify any controls, ANSYS uses default sizing, which assigns minimum and maximum line divisions, aspect ratio, etc. based on element order. O
N TO
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ON
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ON
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ON
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• Meant for mapped meshing, but is also used for free meshing if SmartSizing is off.
• You can adjust default size specifications using DESIZE or
NSYS
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NSYS
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• You can adjust default size specifications using DESIZE or Main Menu > Preprocessor > Meshing > Size Cntrls > ManualSize > Global > Other
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Controlling Mesh DensityIN
TRO
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OIN
TRO
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O
Keypoint Sizing
C t l l t i t k i t
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• Controls element size at keypoints:– Main Menu > Preprocessor > Meshing > MeshTool; then
select “Size Controls, “Keypt”, and [Set]– or KESIZE command O
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
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– or Main Menu > Preprocessor > Meshing > Size Cntrls > ManualSize > Keypoints
Different keypoints can have different KESIZEs giving NSYS
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NSYS
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Different keypoints can have different KESIZEs, giving you more control over the mesh.
• Useful for stress concentration regions. Part 1Part 1Part 1Part 1Part 1Part 1• Specified sizes may be overridden by SmartSizing to
accommodate line curvature or proximity to features.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Controlling Mesh DensityIN
TRO
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OIN
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Line Sizing
• Controls element size at lines:
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– Main Menu > Preprocessor > Meshing > MeshTool; then select “Size Controls”, “Lines”, and [Set]
– or LESIZE command– or Main Menu > Preprocessor > Meshing > Size Cntrls O
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
N
p g> ManualSize> Lines
Different lines can have different LESIZEs.
• Size specifications may be “hard” or “soft ”
Yes for “soft”No for “hard”
NSYS
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• Size specifications may be hard or soft.– “Hard” sizes are always honored by the mesher, even if
SmartSizing is on. They take precedence over all other size controls.
– “Soft” sizes may be overridden by SmartSizing. Part 1Part 1Part 1Part 1Part 1Part 1
• You can also specify a spacing ratio — ratio of last division to first. Used to bias the divisions towards one end or towards the middle.
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Chapter 7 – Creating the Finite Element Model
…Controlling Mesh DensityIN
TRO
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OIN
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TRO
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O
Area Sizing
C t l l t i i th i t i f
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• Controls element size in the interior of areas:– Main Menu > Preprocessor > Meshing > MeshTool; then
select “Size Controls”, “Areas”, and [Set]– or AESIZE command O
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
N
– or Main Menu > Preprocessor > Meshing > Size Cntrls > ManualSize > Areas
Different areas can have different AESIZEs NSYS
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NSYS
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Different areas can have different AESIZEs.
• Bounding lines will use the specified size only if they have no LESIZE or KESIZE specified and if no Part 1
Part 1Part 1Part 1Part 1Part 1
adjacent area has a smaller size.
• Specified sizes may be overridden by SmartSizing to accommodate line curvature or proximity to features
February 7, 2006Inventory #002268
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accommodate line curvature or proximity to features.
Training Manual
Chapter 7 – Creating the Finite Element Model
F. Mesh Order ControlIN
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O• By default, ANSYS will mesh areas or volumes in ascending entity number. O
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• The AORDER field on the MOPT command instructs ANSYS to mesh a group of areas or volumes in order of ascending size.
Main Menu > Preprocessor > Meshing > Mesher Opts or
ON
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ON
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ON
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– Main Menu > Preprocessor > Meshing > Mesher Opts , or– MOPT,AORDER,ON (default is OFF)
• In cases where SmartSizing does not mesh as fine as needed, NSYS
NSYS
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NSYS
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gthe MOPT, AORDER,on command generates finer meshes in critical areas for volume meshes
• This option is not available when SmartSizing is on
Part 1Part 1Part 1Part 1Part 1Part 1
• This option is not available when SmartSizing is on.
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Training Manual
Chapter 7 – Creating the Finite Element Model
G. Generating the MeshIN
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Generating the mesh is the final step in meshing.
• First save the database
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• First save the database.
• Then press [Mesh] in the MeshTool.– This brings up a picker. Press [Pick All] in the picker O
N TO
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ON
TO A
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N TO
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ON
TO A
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ON
TO A
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g p p [ ] pto indicate all entities.
NSYS
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Generating the MeshIN
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• Demo:– Resume ribgeom.db
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– Mesh with SMRT,6. (Not a very good mesh)– Re-mesh with SMRT,3 (good mesh)– Set ESIZE to 0.2 and re-mesh. The mesh becomes coarse even though
SMRT is set to 3 because the smart-mesher takes ESIZE into account
ON
TO A
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N TO
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ON
TO A
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N TO
AN
ON
TO A
NO
N TO
AN
SMRT is set to 3, because the smart mesher takes ESIZE into account. Also, note that the element sizes are not uniform (because SMRT is on).
– Turn off SMRT and re-mesh. Element sizes are now more uniform (but not ideal) N
SYS N
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not ideal).– Re-mesh with ESIZE set to 0.1.
G f S S
Part 1Part 1Part 1Part 1Part 1Part 1
• Good meshes generated for this geometry with SMRT,3 or ESIZE,0.1.
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Chapter 7 – Creating the Finite Element Model
H. Changing a MeshIN
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• If a mesh is not acceptable, you can always re-mesh the model by following these steps:
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1. Clear the mesh.• The clear operation is the opposite of mesh: it
removes nodes and elements.• Use the [Clear] button on the MeshTool or use
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
• Use the [Clear] button on the MeshTool, or use VCLEAR, ACLEAR, etc.
(If you are using the MeshTool, you may skip this step since the program will prompt you whether to clear or not hen o e ec te step 3 )
NSYS
NSYS
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NSYS
NSYS
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clear or not when you execute step 3.)2. Specify new or different mesh controls.3. Mesh again.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Changing a MeshIN
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O
• Another meshing option is to refine the mesh in specific regions.
Available for all area elements and only
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– Available for all area elements and only tetrahedral volume elements.
– Easiest way is to use the MeshTool:• First save the database.
Th h h t t
ON
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N TO
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ON
TO A
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N TO
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ON
TO A
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N TO
AN
• Then choose how you want to specify the region of refinement — at nodes, elements, keypoints, lines, or areas — and press the Refine button.
• Pick the entities at which you want NSYS
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NSYS
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• Pick the entities at which you want the mesh to be refined. (Not required if you choose “All Elems.”)
• Finally, choose the level of refinement. Level 1 (minimal Part 1
Part 1Part 1Part 1Part 1Part 1
(refinement) is a good starting point.
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Chapter 7 – Creating the Finite Element Model
…Changing a MeshIN
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• Demo:– Continuing the last demo… (ribgeom has been meshed with ESIZE =
0 2)
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0.2)– Choose refinement at Lines and press Refine– Pick the top line, then choose the default “minimal refinement” O
N TO
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ON
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ON
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Training Manual
Chapter 7 – Creating the Finite Element Model
I. Mapped MeshingIN
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• There are two main meshing methods: free and mapped.
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• Free Mesh– Has no element shape restrictions.– The mesh does not follow any pattern.
ON
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ON
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ON
TO A
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The mesh does not follow any pattern.– Suitable for complex shaped areas and volumes.
• Mapped Mesh NSYS
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– Restricts element shapes to quadrilaterals for areas and hexahedra (bricks) for volumes.
– Typically has a regular pattern with obvious rows of elements. Part 1
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– Suitable only for “regular” areas and volumes such as rectangles and bricks.
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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Free Mesh
+ Easy to create; no need to divide
Mapped Mesh
+ Generally contains a lower
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+ Easy to create; no need to divide complex shapes into regular shapes.
– Volume meshes can contain only
+ Generally contains a lower number of elements.
+ Lower-order elements may be acceptable so the number of
ON
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N TO
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ON
TO A
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N TO
AN
ON
TO A
NO
N TO
AN
– Volume meshes can contain only tetrahedra, resulting in a large number of elements.
– Only higher-order (10-node)
acceptable, so the number of DOF is lower.
– Areas and volumes must be “regular” in shape and mesh N
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Only higher-order (10-node) tetrahedral elements are acceptable, so the number of DOF can be very high.
regular in shape, and mesh divisions must meet certain criteria.
– Very difficult to achieve
Part 1Part 1Part 1Part 1Part 1Part 1
Very difficult to achieve, especially for complex shaped volumes.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
TRO
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Creating a Free Mesh
• Free meshing is the default setting for both area
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• Free meshing is the default setting for both area and volume meshes.
• Create a free mesh is easy:Bring up the MeshTool and verify that free meshing is
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
– Bring up the MeshTool and verify that free meshing is set.
– SmartSizing is generally recommended for free meshing, so activate it and specify a size level. Save the database. N
SYS N
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– Then initiate the mesh by pressing the Mesh button.• Press [Pick All] in the picker to choose all entities
(recommended).– Or use the commands VMESH,ALL or AMESH,ALL.
Part 1Part 1Part 1Part 1Part 1Part 1
Or use the commands VMESH,ALL or AMESH,ALL.
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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Creating a Mapped Mesh
Thi i t f hi b th d
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• This is not as easy as free meshing because the areas and volumes have to meet certain requirements:
– Area must contain either 3 or 4 lines (triangle or quadrilateral).– Volume must contain either 4, 5, or 6 areas (tetrahedron, triangular
ON
TO A
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N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
Volume must contain either 4, 5, or 6 areas (tetrahedron, triangular prism, or hexahedron).
– Element divisions on opposite sides must match.• For triangular areas or tetrahedral volumes, the number of element
di i i t b
NSYS
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divisions must be even.
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
TRO
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• For quadrilateral areas or hexahedral volumes, unequal divisions are allowed, as shown in these examples, but the number of divisions must satisfy a formula (shown on the next page)
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divisions must satisfy a formula (shown on the next page).
ON
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N TO
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ON
TO A
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N TO
AN
ON
TO A
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N TO
ANN
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…Mapped MeshingIN
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AN
ON
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ON
TO A
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N TO
ANN
SYS N
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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O
• Thus mapped meshing involves a three-step procedure:– Ensure “regular” shapes, i.e, areas with 3 or 4 sides, or volumes with
4 5 6 id
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4, 5, or 6 sides.– Specify size and shape controls– Generate the mesh O
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AN
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AN
ON
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ON
TO A
NNSYS
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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O
Ensure regular shapes
I t th d l t i h th t th h
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• In most cases, the model geometry is such that the areas have more than 4 sides, and volumes have more than 6 sides. To convert these to regular shapes, you may need to do one or both of these operations: O
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
NO
N TO
AN
ON
TO A
N
p– Slice the areas (or volumes) into smaller, simpler shapes.– Concatenate two or more lines (or areas) to reduce the total number of
sides. NSYS
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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O
• Slicing can be accomplished with the Boolean divide operation.– Remember that you can use the working plane, an area, or a line as
th li i t l
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the slicing tool.– Sometimes, it may be easier to create a new line or a new area than to
move and orient the working plane in the correct direction.
ON
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ON
TO A
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N TO
AN
ON
TO A
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N TO
ANN
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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• Concatenation creates a new line (for meshing purposes) that is a combination of two or more lines, thereby reducing the number of li ki th
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lines making up the area.– Use the LCCAT command or Main Menu > Preprocessor > Meshing >
Concatenate > Lines, then pick the lines to be concatenated.– For area concatenation, use ACCAT command or Main Menu > O
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Concatenatingthese two lines Part 1
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makes this a4-sided area
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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• You can also imply a concatenation by simply identifying the three or four corners of the area. In this case ANSYS internally generates the concatenation
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case, ANSYS internally generates the concatenation.– To do this, choose Quad shape and Map mesh in the
MeshTool.– Then change 3/4 sided to Pick corners.
Press the Mesh button pick the area and then pick the 3 or
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– Press the Mesh button, pick the area, and then pick the 3 or 4 corners that form the regular shape.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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• Notes on concatenation:– It is purely a meshing operation and therefore should be the last step before
meshing after all solid modeling operations This is because the output entity
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meshing, after all solid modeling operations. This is because the output entity obtained from a concatenation cannot be used in any subsequent solid modeling operation.
– You can "undo" a concatenation by deleting the line or area it produced.– Concatenating areas (for mapped volume meshing) is generally much more
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Co cate at g a eas ( o apped o u e es g) s ge e a y uc o ecomplicated because you may also need to concatenate some lines. Lines are automatically concatenated only when two adjacent, 4-sided areas are concatenated.
– Consider the add (Boolean) operation if the lines or areas meet at a tangent. NSYS
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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Specify size and shape controls
• This is the second step of the three-step mapped
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Meshing Areas:
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• This is the second step of the three-step mapped meshing procedure.
• Choosing the shape is simple. In the MeshTool, choose Quad for area meshing and Hex for volume meshing
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Quad for area meshing, and Hex for volume meshing, then click on Map.
• Commonly used size controls and the order in which they are applied: Meshing Volumes: N
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they are applied:– Line sizing [LESIZE] is always honored.– Global element size , if specified, will be applied to “unsized”
lines.Default element sizing [DESIZE] will be applied to unsized
Meshing Volumes:
Part 1Part 1Part 1Part 1Part 1Part 1
– Default element sizing [DESIZE] will be applied to unsized lines only if ESIZE is not specified.
– (SmartSizing is not valid.)
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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• If you specify line divisions, remember that:– divisions on opposite sides must match, but you only need to specify
id Th h t ti ll t f di i i t th
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one side. The map mesher automatically transfers divisions to the opposite side.
– if you have concatenated lines, divisions can only be applied to the original (input) lines, not the composite line. O
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N6 divisions specified on each original line N
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each original line.
12 divisions will be automatically applied to this line (opposite to Part 1
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composite line).
How many divisions are used for the other two lines? (Upcoming demo
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lines? (Upcoming demo will answer it.)
Training Manual
Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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Generate the mapped mesh
O h d l h d i d th
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• Once you have ensured regular shapes and assigned the appropriate divisions, generating the mesh is easy. Just press the Mesh button in the MeshTool, then press [Pick All] in the picker or choose the desired entities. O
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Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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• Question: How would you slice this model for
d hi ?
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mapped meshing?
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• Answer: It may not be worth the
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effort!
Training Manual
Chapter 7 – Creating the Finite Element Model
…Mapped MeshingIN
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• Demo:– Resume ribfull.db
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– Bring up MeshTool and apply 6 divisions to top and right lines– Map-mesh the area using “Pick corners.” Notice that the left and
bottom lines get only two divisions each (from DESIZE).– Now specify ESIZE 4 (4 divisions per line) and re-mesh
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Now specify ESIZE,,4 (4 divisions per line) and re mesh– Finally, clear line divisions, specify ESIZE,0.1 (size), and re-mesh
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Training Manual
Chapter 7 – Creating the Finite Element Model
J. Hex-to-Tet MeshingIN
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• For volume meshing, we have only seen two options so far:
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– Free meshing, which creates an all-tet mesh. This is easy to achieve but may not be desirable in some cases because of the large number of elements and total DOF created. O
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– Mapped meshing, which creates an all-hex mesh. This is desirable but usually very difficult to achieve.
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• Hex-to-tet meshing provides a third option that is the “best of both worlds.” It allows you to have a combination of hex and tet meshes without compromising the integrity of the mesh
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without compromising the integrity of the mesh.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Hex-to-Tet MeshingIN
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• This option works by creating pyramid-shaped elements in the transition region between hex and tet regions.
Requires the hex mesh to be available (or at least a quad mesh at the shared
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– Requires the hex mesh to be available (or at least a quad mesh at the shared area).
– The mesher first creates all tets, then combines and rearranges the tet elements in the transition region to form pyramids.
– Available only for element types that support both pyramid and tet shapes e g:
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Available only for element types that support both pyramid and tet shapes, e.g:• Structural SOLID95, 186, VISCO89• Thermal SOLID90• Multiphysics SOLID62, 117, 122 N
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SOLID95
gregion. Element faces are compatible even when transitioning from a linear hex element to a quadratic tet element.
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SOLID95
Training Manual
Chapter 7 – Creating the Finite Element Model
…Hex-to-Tet MeshingIN
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– Hex-to-tet meshing is valid for both quadratic-to-quadratic and linear-to-quadratic transitions. Element type must support a 9-node pyramid for the latter.
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Hex Mesh Transition Layer Tet Mesh
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Quadraticto
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10-Node Tet13-Node Pyramid20-Node Hex
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Quadratic
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8-Node Hex 9-Node Pyramid 10-Node Tet
Training Manual
Chapter 7 – Creating the Finite Element Model
…Hex-to-Tet MeshingIN
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Procedure involves four steps:
1 C t th h h
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1. Create the hex mesh.– Start by map-meshing the regular-shaped volumes. (Or mesh the
shared areas with quads.)– For stress analysis, use either an 8-node brick (SOLID45 or SOLID185) O
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y , ( )or a 20-node brick (SOLID95 or SOLID186).
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Chapter 7 – Creating the Finite Element Model
…Hex-to-Tet MeshingIN
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2. Activate an element type that supports both pyramids and tets.– These are usually brick elements that can degenerate into pyramids
d t t Ch k th El t M l il bl li t fi d t
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and tets. Check the Elements Manual, available on-line, to find out which element types are valid.
3. Generate the tet mesh.– First activate free meshing.
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– Then mesh the volumes that are to be tet-meshed.
Pyramids are automatically generated at the interface. ON
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Chapter 7 – Creating the Finite Element Model
…Hex-to-Tet MeshingIN
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4. Convert degenerate tets to true 10-node tets.– The tet mesh created by the transition mesher consists of degenerate
l t 10 d t t h d d i d f 20 d b i k f
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elements — 10-node tetrahedra derived from 20-node bricks, for example.
– These elements are not as efficient as true 10-node tets such as SOLID92, which use less memory and write smaller files during O
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solution.– To convert the degenerate tets into true tets:
• Main Menu > Preprocessor > Meshing > Modify Mesh > Change TetsO th TCHG d
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• Or use the TCHG command.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Hex-to-Tet MeshingIN
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• Demo:– Resume hextet.db
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– Show element type list using Element Type > Add/Edit/Delete. There are two element types: SOLID45 & 95
– Bring up MeshTool and set ESIZE,1 (size)– Map-mesh the regular shaped volume
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Map mesh the regular shaped volume– Set element type to 2, and activate tet-meshing– Free-mesh the other volume– Convert degenerate tets to SOLID92 N
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– Show element type list. There are now three element types.– Select elements of type 2 (SOLID95 pyramids) and plot elements
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Chapter 7 – Creating the Finite Element Model
K. Mesh ExtrusionIN
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• When you extrude an area into a volume, you can extrude the area elements along with it, resulting in a meshed volume. This is called mesh extrusion. O
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• Advantage: Easy to create a volume mesh with all bricks (hexahedra) or a combination of bricks and prisms.
O S f f
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• Obvious requirement: Shape of the volume must lend itself to extrusion.
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Mesh ExtrusionIN
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Procedure
1 D fi t l t t
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1. Define two element types — an area element and a volume element.
– Area element: Choose MESH200 quadrilaterals. MESH200 is a mesh- O
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qonly (Not Solved) element and has no DOFs or material properties associated with it.
– Volume element: Should be NSYS
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Volume element: Should be compatible with the MESH200 element type. For example, if you choose midside nodes for MESH200, the 3-D solid element should also Part 1
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the 3 D solid element should also have midside nodes.
– ET command or Main Menu > Preprocessor > Element
T Add/Edit/D l t
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Type > Add/Edit/Delete
Training Manual
Chapter 7 – Creating the Finite Element Model
…Mesh ExtrusionIN
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2. Mesh the area to be extruded with MESH200 elements.– Use mapped or free meshing with desired mesh density.
Main Menu > Preprocessor > Meshing > MeshTool
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– Main Menu > Preprocessor > Meshing > MeshTool
3. Choose element extrusion options.
EXTOPT command or Main Menu >
ON
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– EXTOPT command or Main Menu > Preprocessor > Modeling > Operate > Extrude > Elem Ext Opts
– Typical options are:• Active TYPE attribute (should be 3-D N
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• Active TYPE attribute (should be 3-D solid).
• Number of element divisions in the extrusion direction (i.e, number of elements through the thickness). Must Part 1
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g )be greater than zero; otherwise, only the area will be extruded, without elements.
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Chapter 7 – Creating the Finite Element Model
…Mesh ExtrusionIN
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4. Extrude the area.– First delete concatenated lines, if any. If concatenations are present,
ANSYS ill t ll th t i ti
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ANSYS will not allow the extrusion operation.• Main Menu > Preprocessor > Meshing > Concatenate > Del Concats > Lines
– Then extrude the area using any of the extrusion methods. ON
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Training Manual
Chapter 7 – Creating the Finite Element Model
…Mesh ExtrusionIN
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• Demo:– Resume ribgeom.db O
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– Bring up the Element Types dialog, delete PLANE82 element type, and replace it with MESH200 4-node quad
– Also add SOLID45 as element type 2– Bring up MeshTool and set ESIZE 0 1
ON
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ON
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ON
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Bring up MeshTool and set ESIZE,0.1– Choose free quad-meshing and mesh the area– Set extrusion options: TYPE=2, number of element divisions = 4– Rotate view to ISO N
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– Extrude area along normal with offset = 0.4– Save the database to ribvol.db
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Training Manual
Chapter 7 – Creating the Finite Element Model
L. Sweep MeshingIN
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• Sweep meshing is yet another option available for volume meshing. It is the process of meshing an existing volume by
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sweeping an area mesh.
• Similar to mesh extrusion, except that the volume already exists in this case (from a geometry import, for example). O
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( g y p , p )
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Chapter 7 – Creating the Finite Element Model
…Sweep MeshingIN
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• Advantages:– Easy to create a volume mesh with all
b i k (h h d ) bi ti
Target surface(1 area)
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bricks (hexahedra) or a combination of bricks and prisms.
– Option to tet-mesh volumes that are not “sweepable.” Transition
S f
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ON
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ON
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pyramids are automatically generated.
• Requirements:
Source surface(1 area)
Valid for sweep meshing NSYS
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q– Topology of the volume must be
consistent in the sweep direction. Example: a block with a through hole (ok even if the hole is tapered)
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(ok even if the hole is tapered).– Source and target surfaces must be
single areas. Concatenated areas are not allowed for either the source or the target
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the target.Not valid for sweep meshing
Training Manual
Chapter 7 – Creating the Finite Element Model
…Sweep MeshingIN
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Procedure
• Define and activate a 3-D hexahedral solid element
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• Define and activate a 3-D hexahedral solid element type, such as structural SOLID45 or SOLID95.
• Bring up MeshTool and choose Hex/Wedge and Sweep. ON
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ON
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ON
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• Choose how the source and target surfaces are identified:
– “Auto Source/Target” means that ANSYS will automatically choose them based on the volume’s topology N
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choose them based on the volume s topology.– “Pick Source/Target” means that you will be choosing
them.
• Press the SWEEP button and follow prompt Part 1Part 1Part 1Part 1Part 1Part 1
Press the SWEEP button and follow prompt instructions from the picker. (Or use VSWEEPcommand.)
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Chapter 7 – Creating the Finite Element Model
…Sweep MeshingIN
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Tet-Mesh Option
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• A useful sweep option is to generate a tet-mesh in non-sweepable volumes.
• To use this option: ON
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p– Make sure that the element type supports
degenerate pyramid and tetrahedron shapes. Examples:
– Choose Main Menu > Preprocessor > Meshing Part 1Part 1Part 1Part 1Part 1Part 1
> Mesh > Volume Sweep > Sweep Opts and activate the tet-mesh option. (Or use the EXTOPT,VSWE command.)
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Chapter 7 – Creating the Finite Element Model
…Sweep MeshingIN
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Notes
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• To map-mesh a complex volume, you may need to slice it several times and also do some area and line concatenations. For sweep meshing, you typically need only a few slicing operations, and noconcatenations are needed! O
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• You can control the source area mesh using standard mesh controls. SmartSizing is generally not recommended since it is meant for free meshing
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meant for free meshing.
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Chapter 7 – Creating the Finite Element Model
…Sweep MeshingIN
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• Demo:– Resume ribvol.db
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– Clear all volumes and all areas, then plot volumes– Bring up MeshTool and activate sweep meshing– Sweep mesh the volume O
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 7 – Creating the Finite Element Model
M. F.E. ImportsIN
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• In addition to solid model geometry, ANSYS can also import finite element model data (nodes and elements) from certain packages. O
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• The most common approach is for the software vendor to “write out” the nodes and elements in a format that ANSYS can read (using NREAD and EREAD). This format is published in the O
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( g ) pANSYS Programmer’s Manual.
• Some software packages provide an interface that allows you to transfer more than just nodes and elements from another finite
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transfer more than just nodes and elements from another finite element package into ANSYS.
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Training Manual
Chapter 7 – Creating the Finite Element Model
N. WorkshopsIN
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• This workshop consists of five exercises:W7B. Pillow Block O
• In this chapter, we discuss units, importing ANSYS defined materials, as well as describe how to define a user defined
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material.
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Training Manual
Chapter 8 – Defining the Material
A. UNITSIN
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A Note on Units
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• You do not need to tell ANSYS the system of units you are using. Simply decide what units you will use, then make sure all of your input is consistent.
– For example, if the model geometry is in inches, make sure that all
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For example, if the model geometry is in inches, make sure that all other input data — material properties, real constants, loads, etc. —are in terms of inches.
• ANSYS does NOT do units conversion! It simply accepts all NSYS
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• ANSYS does NOT do units conversion! It simply accepts all numbers you input without questioning their validity.
• The command /UNITS allows you to specify a units system, but it Part 1Part 1Part 1Part 1Part 1Part 1
is simply a recording device to let other users of your model know what units you used.
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Training Manual
Chapter 8 – Defining the Material
B. ANSYS Defined MaterialsIN
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Using the Material Library
• This method allows you to choose a predefined set of properties for a
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• This method allows you to choose a predefined set of properties for a given material.
• ANSYS supplies typical structural and thermal properties (linear only) for some common materials but we strongly recommend that you create your
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some common materials, but we strongly recommend that you create your own material library.
• To choose a material from the library:– First define the library path. N
SYS N
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y p• Main Menu > Preprocessor > Material Props > Material Library > Library Path
– Enter the location from which to READ material data, e.g, \v100\ANSYS\matlib.• Or use the /MPLIB command. Part 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 8 – Defining the Material
…ANSYS Defined MaterialIN
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– Then “import” a material from the library.• Main Menu > Preprocessor > Material
Library > Import Library OD
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– Choose the units system. This is used only to filter the list of files shown in the subsequent dialog. ANSYS has no knowledge of units and does NOT do unit conversion
ON
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and does NOT do unit conversion.– Choose the desired material file,
such as steel AISI C1020.• Or use the MPREAD command with the
LIB option
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LIB option.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 8 – Defining the Material
C. Material Model GUIIN
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Specifying Individual Material Properties
• Instead of choosing a material name this method involves directly
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• Instead of choosing a material name, this method involves directly specifying the required properties through the Material Model GUI.
• To specify individual properties:Main Menu > Preprocessor > Material Props > Material Models
ON
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– Main Menu > Preprocessor > Material Props > Material Models• Double-click on the appropriate property to be defined.
NSYS
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Training Manual
Chapter 8 – Defining the Material
…Material Model GUIIN
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• Work through the tree structure to the material t t b d fi d
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type to be defined.
• Then enter the individual property values. O
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p p y
• Or use the MP command.– mp,ex,1,30e6
mp prxy 1 3
NSYS
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– mp,prxy,1,.3
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 8 – Defining the Material
…Material Model GUIIN
TRO
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O
• Add temperature dependent properties O
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• Graph properties vs. temperature
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Training Manual
Chapter 8 – Defining the Material
…Material Model GUIIN
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• Copy material models from one table to another O
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• Delete material models
ON
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Training Manual
Chapter 8 – Defining the Material
…Material Model GUIIN
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• Material GUI Favorites Option• Stores shortcuts to groups of
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frequently used material properties.
• Allows you to define a template based on the currently selected model in the database, then specify O
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, p yyour own name for the template (which can be a useful descriptor such as "Steel" or "Metal Plasticity").
D t ifi d t i l
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• Does not save specified materials and related data. It does, however, save your Favorites template to the ANSYS registry file for use in all
b t l
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subsequent analyses.
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Training Manual
Chapter 8 – Defining the Material
D. Listing Defined MaterialsIN
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g
• The Material Model GUI shows one material at a time. Multiple material properties can be listed by: O
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– Utility Menu > List > Properties > All Materials– Or, use the MPLIST command
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– Note, Nonlinear material properties can be listed using Utility Menu > List Properties > Data Tables or via the TBLIST command.
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Training Manual
Chapter 8 – Defining the Material
E. WorkshopsIN
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• This workshop consists of two exercises:W8A. User Input Material O
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W8B. Material Library Input
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Chapter 9
Loading
Training Manual
Chapter 9 - Loading
OverviewIN
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• The solution step is where we apply loads on the object and let the solver calculate the finite element solution. O
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• Loads are available both in the Preprocessor and Solution menus.
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Training Manual
Chapter 9 - Loading
A. Define LoadsIN
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• There are five categories of loads:DOF Constraints Specified DOF values, such as displacements
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in a stress analysis or temperatures in a thermal analysis.
Concentrated Loads Point loads, such as forces or heat flow rates.Surface Loads Loads distributed over a surface, such as O
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,pressures or convections.
Body Loads Volumetric or field loads, such as temperatures (causing thermal expansion) or internal heat generation. N
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generation.Inertia Loads Loads due to structural mass or inertia, such
as gravity and rotational velocity.
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Training Manual
Chapter 9 - Loading
…Define LoadsIN
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• You can apply loads either on the solid model or directly on the FEA model (nodes and elements). O
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– Solid model loads are easier to apply because there are fewer entities to pick.
– Moreover, solid model loads are independent of the mesh. You don’t need to reapply the loads if you change the mesh. O
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Pressures on element facesPressure on line NSYS
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t dConstraint
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at nodes
FEA model
on line
Solid model
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Force at nodeForce at keypoint
Training Manual
Chapter 9 - Loading
…Define LoadsIN
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• Regardless of how you apply the loads, the solver expects all loads to be in terms of the finite element model. Therefore, solid
d l l d t ti ll t f d t th d l i d
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model loads are automatically transferred to the underlying nodes and elements during solution.
• Solid Model Loads can be transferred to the finite element mesh ON
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manually before solving by using the SBCTRAN command. This can be useful to see all of the loads, both solid model and FE, that have been applied.
F l if i li d t l t f th l t
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– For example, if a pressure is applied to an area, a plot of the elements will not show the pressure until the SBCTRAN command is issued or the model is solved.
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Training Manual
Chapter 9 - Loading
B. Nodal Coordinate SystemIN
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y
• All forces, displacements, and other direction-dependent nodal quantities are interpreted in the nodal coordinate system. O
– Output quantities:• Calculated displacements UX UY UZ ROTX ROTY ROTZ N
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• Calculated displacements UX, UY, UZ, ROTX, ROTY, ROTZ• Reaction forces FX, FY, FZ, MX, MY, MZ• Etc. Part 1
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Training Manual
Chapter 9 - Loading
...Nodal Coordinate SystemIN
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• A nodal coordinate system is attached to every node in the model.
B d f lt th d l CS i ll l t Gl b l C t i i ll
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• By default, the nodal CS is parallel to Global Cartesian, i.e, all applied forces and displacement constraints are interpreted in Global Cartesian by default. O
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X Xn
Training Manual
Chapter 9 - Loading
...Nodal Coordinate SystemIN
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• If necessary, you can rotatethe nodal CS to a different
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orientation.
For example:– To simulate an inclined roller
ON
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To simulate an inclined roller support.
– To apply radial forces.– To apply radial constraints
(perhaps to simulate a rigid
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(perhaps to simulate a rigid, press-fitted pin).
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 9 - Loading
...Nodal Coordinate SystemIN
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• To “rotate nodes,” use this four-step procedure:1. Select the desired nodes. O
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2. Activate the coordinate system (or create a local CS) into which you want to rotate the nodes, e.g, CSYS,1.
3. Choose Main Menu > Preprocessor > Modeling >
ON
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3. Choose Main Menu Preprocessor Modeling Move/Modify > Rotate Node CS > To Active CS, then press [Pick All] in the picker.Or issue NROTAT,ALL.
4 Reactivate all nodes
NSYS
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• Note: When you apply symmetry on anti-symmetry boundary conditions, ANSYS automatically rotates all nodes on that boundary.
4. Reactivate all nodes.
Part 1Part 1Part 1Part 1Part 1Part 1• Very Important: Nodal Coordinate Systems ALWAYS behave in a
Cartesian manner. NROTAT simply aligns the nodal CS with a global or local CS. Consequently, remember that (a) there is no dependency
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or association of a nodal CS with a global/local CS to which it is rotated and (b) the nodal CS still acts as a Cartesian CS.
Training Manual
Chapter 9 - Loading
...Nodal Coordinate SystemIN
TRO
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O
• Demo:– Resume rib.db.
Off t ki l t t f b tt i l ( i k i t l ti )
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– Offset working plane to center of bottom circle (using average keypoint location).– Create local cylindrical CS at working plane origin.– Select nodes at radius = 0.35 and plot them.– Rotate all selected nodes into active system. O
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– Apply a UX displacement constraint (or an FX force) at all selected nodes. Note the radial direction.
– Now activate global Cartesian (CSYS,0).– Rotate all selected nodes into active system. N
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– Replot, and note the new direction of the loads.
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Training Manual
Chapter 9 - Loading
C. Displacement ConstraintsIN
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• Displacement constraints are also used to enforce symmetry or antisymmetry boundary conditions. O
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– Symmetry BC: Out-of-plane displacements and in-plane rotations are fixed.
– Antisymmetry BC: In-plane displacements and out-of-plane rotations are fixed. O
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Y
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Antisymmetry BoundaryUY=UZ=0
Symmetry BoundaryUX=0
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UY=UZ=0ROTX=0
UX=0ROTY=ROTZ=0
Training Manual
Chapter 9 - Loading
D. Concentrated ForcesIN
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• A force is a concentrated load (or “point load”) that you can apply at
d k i t
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a node or keypoint.
• Point loads such as forces are appropriate for line element O
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pp pmodels such as beams, spars, and springs.
In solid and shell models point
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In solid and shell models, point loads usually cause a stress singularity, but are acceptable if you ignore stresses in the vicinity. Part 1
Part 1Part 1Part 1Part 1Part 1
Remember, you can use select logic to “ignore” the elements in the vicinity of the point load.
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Training Manual
Chapter 9 - Loading
...Concentrated ForcesIN
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• In the 2-D quarter symmetry solid model shown at bottom left, notice that maximum stress SMAX (23,590) is reported at the location of the force. O
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When the nodes and elements in the vicinity of the force are unselected, SMAX (12,281) moves to the bottom left corner, which is another singularity due to the reentry corner. Reflected about x-z plane
half symmetry model
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half symmetry model
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Training Manual
Chapter 9 - Loading
…Concentrated ForcesIN
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By unselecting nodes and elements near the bottom left corner, you get the expected stress distribution with SMAX (7,945) near th t h l
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the top hole.
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Training Manual
Chapter 9 - Loading
…Concentrated ForcesIN
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Note that for axisymmetric models:
• Input values of forces are based on the full 360°
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• Input values of forces are based on the full 360 .
• Output values (reaction forces) are also based on the full 360°.
• For example suppose a cylindrical shell of radius r has an edge load of P
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• For example, suppose a cylindrical shell of radius r has an edge load of P lb/in. To apply this load on a 2-D axisymmetric shell model (SHELL51 elements, for example), you would specify a force of 2πrP.
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r
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Training Manual
Chapter 9 - Loading
E. Verifying LoadsIN
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Verifying applied loads
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• Plot them by activating load symbols:– Utility Menu > PlotCtrls > Symbols– Commands -- /PBC, /PSF, /PBF O
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• Or list them:– Utility Menu > List > Loads >
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Chapter 10
Solution
Training Manual
Chapter 10 – Solution
A. SolversIN
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• The function of the solver is to solve the system of linear simultaneous equations representing the structure’s degrees of f d
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freedom.
• The solution could take anywhere from a few seconds to several hours depending primarily on the size of the model, the solver O
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p g p y ,selected, and the speed of your computer.
• A linear static analysis with one load step requires only one such solution but a nonlinear or transient analysis may require tens
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solution, but a nonlinear or transient analysis may require tens, hundreds, or even thousands of solutions.
Therefore, the type of solver you choose for solution can be quite Part 1Part 1Part 1Part 1Part 1Part 1
important.
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Training Manual
Chapter 10 – Solution
…SolversIN
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• The solvers available in ANSYS can be categorized into four types:
1) Direct elimination
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1) Direct elimination2) Iterative3) Distributed ANSYS †
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1) Direct elimination solvers• Sparse (default)• Frontal
† Part of the Parallel Performance for ANSYS add-on license
Training Manual
Chapter 10 – Solution
…SolversIN
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3) Distributed ANSYS (D-ANSYS) (all of the ANSYS /SOLUTION phase is in parallel which includes stiffness matrix generation, linear equation solving and results calculation) O
– Factorization of the matrix and back/forward substitution is done in distributed parallel mode O
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• Existing Shared Memory Sparse Solver (EQSLVE,SPARSE) – The solver itself runs only on the master process (other parts run in distributed
parallel)– May be run in shared memory parallel mode on the master machine
(/CONFIG,NPROC,N) NSYS
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( , , )
A general discussion of direct and iterative solvers will be covered in the next slides.
Part 1Part 1Part 1Part 1Part 1Part 1
December 17, 2004Inventory #002170
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† Part of the Parallel Performance for ANSYS add-on license
Training Manual
Chapter 10 – Solution
…SolversIN
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• Calculate the solution as follows:
1 Formulate individual element matricesFormulate element
t i
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1. Formulate individual element matrices.2. Assemble the global stiffness matrix.3a. (Sparse direct solver) Factorize the stiffness
matrix, then calculate DOF solution from back-substitution
matrices
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back-substitution.3b. (Iterative Solver) Start with an assumed zero
value for all DOF and iterate to convergence (based on an input tolerance on residual force).
Assembleglobal matrix
.fullfile N
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4. Use element matrices to calculate the element solution.
Part 1Part 1Part 1Part 1Part 1Part 1Solve matrix
equation.rst /.rth
file
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Training Manual
Chapter 10 – Solution
…SolversIN
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Direct solver vs. Iterative solver (simplified discussion)
• If given the linear static case of [K]{x} = {F}, Direct solvers factorize [K] to solve for OD
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g [ ]{ } { } [ ][K]-1. Then, {x} = [K]-1{F}.
– This factorization is computationally expensive but is done once.
• Iterative solvers use a preconditioner [Q] to solve the equation [Q][K]{x} = [Q]{F}. A th t [Q] [K] 1 I thi t i i l [I]{ } [K] 1{F} H th
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Assume that [Q] = [K]-1. In this trivial case, [I]{x} = [K]-1{F}. However, the preconditioner is not usually [K]-1. The closer [Q] is to [K]-1, the better the preconditioning is. However, the preconditioner is not usually [K]-1, so this process is repeated - hence the name, iterative solver.
– For iterative solvers, matrix multiplication (not factorization) is performed. This is NSYS
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For iterative solvers, matrix multiplication (not factorization) is performed. This is much faster than matrix inversion if done entirely in RAM, so, as long as the number of iterations is not very high (which happens for well-conditioned matrices), iterative solvers can be more efficient than sparse solvers.
– The main difference between the iterative solvers in ANSYS — PCG, JCG, ICCG Part 1Part 1Part 1Part 1Part 1Part 1
AMG (Algebraic Multigrid)– Iterative solver that can be used in single and multiprocessor environments
• DDS (Distributed Domain Solver)– Decomposes large models into smaller domains, and then sends those domains
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p g ,to multiple processors for solving. The DDS solver is scalable, intended for large static or full transient analyses, with symmetric matrices that do not involve inertia relief or problems using the probabilistic design system (PDS).
– Iterative equation solver based on the JCG solver. Scalability of this solver is superior to the JCG solver with little extra memory required. DJCG solver is available only for static and full transient analyses where the stiffness is
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symmetric.
Training Manual
Chapter 10 – Solution
…SolversIN
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• To choose a solver:– Main Menu > Solution > Analysis Type > Sol’n Controls, then choose Sol’n
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Options tab– Or use EQSLV command
The default is to use a “program chosen” solver [eqslv,-1], which ON
) A loadstep can be defined as one set of loading conditions for which you obtain a solution
Part 1Part 1Part 1Part 1Part 1Part 1
5
10
Fo Substep 1 of Loadstep 2solution.
A substep can be defined as a subdivision of a loadstep.
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00 10 20 30 40 50 60 70 80 90 100
time (seconds)
Training Manual
Chapter 10 – Solution
C. Multiple LoadstepsIN
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• The procedure to solve for one set of loading conditions (i.e, one load step) is as follows: O
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– Import or create the model– Mesh it– Apply loads
Solve (one load step)
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– Solve (one load step)– Review results
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Training Manual
Chapter 10 – Solution
…Multiple LoadstepsIN
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• If you have multiple loading conditions, you can choose one of two ways: O
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– Solve for all loads together in a single load step
– Or apply each loading condition separately and solve multiple load steps. O
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Training Manual
Chapter 10 – Solution
…Multiple LoadstepsIN
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• By using multiple load steps, you can:– “isolate” the structure’s response to each loading condition. O
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– combine these responses in any desired fashion during postprocessing, allowing you to study different “what-if” scenarios. (This is called load case combination and is valid for linear analyses only. Load case combinations are covered in a later chapter.) O
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• There are two ways to define and solve multiple load steps:– Multiple solve method
Load step file method
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– Load step file method
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 10 – Solution
…Multiple LoadstepsIN
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Multiple Solve Method
• An extension of the single-load-step Import or create the model
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• An extension of the single-load-step solution, where you solve each load step sequentially without leaving the Solution processor.
– Import or create the model– Mesh it– Apply loads– Solve (load step 1)
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• Best suited for batch mode.
• When used in interactive mode, this method is useful only for models that
– Apply different loads– Solve (load step 2)– Apply different loads– Solve (load step 3) N
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method is useful only for models that solve quickly. – Etc.
– Review results
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 10 – Solution
…Multiple LoadstepsIN
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Load Step File Method
• In this case instead of solving each load Import or create the model
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• In this case, instead of solving each load step, you write the load step information to a file, called the load step file:
– Main Menu > Solution > Load Step Opts > Write LS File
– Import or create the model– Mesh it– Apply loads– Write to LS file (.s01)
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LS File– Or use LSWRITE command.
• The load step file is named jobname.s01, s02 s03 etc
– Apply different loads– Write to LS file (.s02)– Apply different loads– Write to LS file (.s03) N
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.s02, .s03, etc.
• After all load steps have been written out, you can use one command — LSSOLVE or Main Menu > Solution > Solve > From LS Files
– Etc.– Solve from LS files– Review results
Part 1Part 1Part 1Part 1Part 1Part 1
Main Menu > Solution > Solve > From LS Files— to read in each file sequentially and solve it.
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Training Manual
Chapter 10 – Solution
…Multiple LoadstepsIN
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• The advantage of the load step file method is that you can interactively set up all load steps even for a large model and then
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solve them while you are away from the computer.
• Note: The loading commands on the load step file are always in terms of nodes and elements, even if you apply loads on the solid O
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, y pp ymodel.
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Training Manual
Chapter 10 – Solution
…Multiple LoadstepsIN
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• For both methods:– It is recommended that the user specify a new title prior
t SOLVE (M lti l S l M th d) d LSWRITE (L d
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to SOLVE (Multiple Solve Method) and LSWRITE (Load Step File Method) since /TITLE is saved in the results file for each load step.
– Loads applied in a previous load step will stay in the ON
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database unless they are deleted. So be sure to delete any loads that are not part of the current load step.
– Results for each load step are appended to the results file and identified as load step 1, load step 2, etc. N
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p , p ,– In postprocessing, you first “read in” the desired set of
results and then review them.– The database contains the loads and results for the last
load step that was solved
Part 1Part 1Part 1Part 1Part 1Part 1
load step that was solved.
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Training Manual
Chapter 10 – Solution
…Multiple LoadstepsIN
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• Demo:– Resume rib.db
Fi l ft li i UX d b tt li i UY
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– Fix left line in UX and bottom line in UY– Apply pressure = 100 on top line– Write LS file 1, then list it and show F.E. load commands– Apply pressure = 50 to 100 (tapered) on right line O
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– Delete the top pressure load– Write LS file 2– LSSOLVE,1,2– Review results for each load step separately N
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Training Manual
Chapter 10 – Solution
D. WorkshopsIN
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• This workshop consists of three exercises:W10A. 3-D Bracket O
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W10B. Connecting RodW10C. Wheel
Refer to your Workshop Supplement for instructions
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Refer to your Workshop Supplement for instructions.
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Chapter 11
Structural Analysis
Training Manual
Chapter 11 – Structural Analysis
OverviewIN
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• In this chapter, we will describe the specifics of a structural analysis. O
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• The purpose is two-fold:– To reiterate the general analysis procedure.– To introduce you to structural loads and boundary conditions
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To introduce you to structural loads and boundary conditions
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Training Manual
Chapter 11 – A. Preprocessing
GeometryIN
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Geometry
C ith b t d ithi ANSYS i t d
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• Can either be created within ANSYS or imported.
• Include details to improve results:– Goal is to sufficiently model the stiffness of the structure
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Goal is to sufficiently model the stiffness of the structure– Add details to avoid stress singularities (e.g. fillets)– Exclude details not in region of interest (e.g. exclude small holes)– Add details to improve boundary conditions (e.g. apply pressure to an N
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area rather than using concentrated load)
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Training Manual
Chapter 11 – A. Preprocessing
MeshingIN
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• Element type• The table below shows commonly used structural element types.
gO
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y yp• The nodal DOF’s may include: UX, UY, UZ, ROTX, ROTY, and ROTZ.
Commonly used structural element types2-D Solid 3-D Solid 3-D Shell Line Elements ON
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ON
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Linear PLANE42 SOLID45 SHELL63 BEAM3PLANE182 SOLID185 SHELL181 BEAM4
BEAM188Quadratic PLANE2 SOLID95 SHELL93 BEAM189 N
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PLANE82 SOLID92PLANE183 SOLID186
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– Minimum requirement is Young s Modulus, EX. If Poisson s Ratio is not entered a default of 0.3 will be assumed.
– Setting preferences to “Structural” limits the Material Model GUI to display only structural properties.
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• Real constants and Section properties– Primarily needed for shell and line elements.
Training Manual
Chapter 11 – B. Solution
Define LoadsIN
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• Structural loading conditions can be:
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DOF Constraints Regions of the model where displacements are known.
Concentrated Forces External forces that can be simplified as a point load. ON
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ON
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Pressures Surfaces where forces on an area are known.
Uniform Temperature Temperatures applied as a body force used with a reference t t t di t th l t i
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temperature to predict thermal strains.
Gravity Accelerations applied as inertia boundary conditions
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 11 – B. Solution
Displacement ConstraintsIN
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Displacement Constraints
• Used to specify where the model is fixed (zero displacement locations)
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• Used to specify where the model is fixed (zero displacement locations).
• Can also be non-zero, to simulate a known deflection.
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ON
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• To apply displacement constraints :– Main Menu > Solution > Define Loads > Apply
> Structural > Displacement• Choose where you want to apply the
constraint NSYS
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constraint.• Pick the desired entities in the
graphics window.• Then choose the constraint direction.
Value defaults to zero. Part 1Part 1Part 1Part 1Part 1Part 1
– Or use the D family of commands: DK, DL, DA, D.
• Question: In which coordinate system are UX UY and UZ interpreted?
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are UX, UY, and UZ interpreted?
Training Manual
Chapter 11 – B. Solution
Concentrated ForcesIN
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• To apply a force, the following information is needed:– node or keypoint number (which you can identify by picking) O
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– force magnitude (which should be consistent with the system of units you are using)
– direction of the force — FX, FY, or FZ ON
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ON
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ON
TO A
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Use:– Main Menu > Solution > Define Loads > Apply > Structural > Force/Moment– Or the commands FK or F N
SYS N
SYS N
SYS ---PPPN
SYS N
SYS N
SYS ---PPP
• Question: In which coordinate system are FX, FY, and FZ interpreted? Part 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 11 – B. Solution
PressureIN
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Pressures
T l
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• To apply a pressure:– Main Menu > Solution > Define Loads > Apply
Structural > Pressure• Choose where you want to apply the
ON
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ON
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ON
TO A
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Choose where you want to apply the pressure -- usually on lines for 2-D models, on areas for 3-D models.
• Pick the desired entities in the graphics window
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
window.• Then enter the pressure value.
A positive value indicates a compressive pressure (acting towards Part 1
Part 1Part 1Part 1Part 1Part 1
the centroid of the element).– Or use the SF family of commands: SFL,
SFA, SFE, SF.
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Training Manual
Chapter 11 – B. Solution
…PressureIN
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• For a 2-D model, where pressures are usually applied on a line, you
if t d500
L3500 O
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can specify a tapered pressure by entering a value for both the I and J ends of the line. VALI = 500
L3
ON
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ON
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ON
TO A
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• I and J are determined by the line direction. If you see the taper going in the wrong direction, simply reapply the pressure with VALI = 500
L3
1000500
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
simply reapply the pressure with the values reversed.
VALI = 500VALJ = 1000
1000 Part 1Part 1Part 1Part 1Part 1Part 1
VALI = 1000VALJ = 500
L3500
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Training Manual
Chapter 11 – B. Solution
Uniform temperatureIN
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Uniform Temperature
T d fi if t t
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• To define uniform temperature– Main Menu > Solution > Define Loads > Apply > Structural > Temperature > Uniform Temp– Or use the TUNIF command
ON
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ON
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ON
TO A
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Or use the TUNIF command.
)( refth TT −=αε• Recall, NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
• To define reference temperature– Main Menu > Solution > Load Step Opts > Other > Reference Temp– Or use the TREF command or as MP REFT
Part 1Part 1Part 1Part 1Part 1Part 1
– Or use the TREF command or as MP,REFT
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Training Manual
Chapter 11 – B. Solution
GravityIN
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Gravity
T l it ti l l ti
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• To apply gravitational acceleration:– Main Menu > Solution > Define Loads >
Apply > Structural > Inertia > Gravity– Or use the ACEL command. O
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ON
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ON
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ON
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• Notes:– A positive acceleration value causes deflection in the negative
direction. If Y is pointing upwards, for example, a positive ACELY NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
value will cause the structure to move downwards.– Density (or mass in some form) must be defined for gravity and other
inertia loads.– Acceleration can also be applied on an element component with the Part 1
Part 1Part 1Part 1Part 1Part 1
Acceleration can also be applied on an element component with the CMACEL command.
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Training Manual
Chapter 11 – B. Solution
Modifying and Deleting LoadsIN
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Modifying and Deleting Loads
T dif l d l i l l th l d
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• To modify a load value, simply reapply the load with the new value.
• To delete loads: ON
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ON
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ON
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– Main Menu > Solution > Define Loads > Delete– When you delete solid model loads, ANSYS also
automatically deletes all corresponding finite element loads N
SYS N
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SYS N
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element loads.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 11 – B. Solution
Solutions OptionsIN
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Static vs. Dynamic Analysis
A t ti l i th t l th tiff f
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• A static analysis assumes that only the stiffness forces are significant.
• A dynamic analysis takes into account all three types of forces. ON
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ON
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ON
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y y yp
• For example, consider the analysis of a diving board.– If the diver is standing still, it might be sufficient to do N
SYS N
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SYS ---PPPN
SYS N
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g , ga static analysis.
– But if the diver is jumping up and down, you will need to do a dynamic analysis. Part 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 11 – B. Solution
Solutions OptionsIN
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• Inertia and damping forces are usually significant if the applied loads vary rapidly with time. O
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• Therefore you can use time-dependency of loads as a way to choose between static and dynamic analysis.
– If the loading is constant over a relatively long period of time, choose
ON
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ON
TO A
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N TO
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ON
TO A
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If the loading is constant over a relatively long period of time, choose a static analysis.
– Otherwise, choose a dynamic analysis.
• In general if the excitation frequency is less than 1/3 of the
NSYS
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NSYS
NSYS
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• In general, if the excitation frequency is less than 1/3 of the structure’s lowest natural frequency, a static analysis may be acceptable.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 11 – B. Solution
Solutions OptionsIN
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Linear vs. Nonlinear Analysis
A li l i th t th l di li ibl
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• A linear analysis assumes that the loading causes negligible changes to the stiffness of the structure. Typical characteristics are:
– Small deflections
ON
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ON
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ON
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Small deflections– Strains and stresses within the elastic limit– No abrupt changes in stiffness such as two bodies coming into and
out of contact NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPPStress Part 1
Part 1Part 1Part 1Part 1Part 1
Elastic modulus(EX)
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Strain
Training Manual
Chapter 11 – B. Solution
Solutions OptionsIN
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• A nonlinear analysis is needed if the loading causes significant changes in the structure’s stiffness. Typical reasons for stiffness t h i ifi tl
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to change significantly are:– Strains beyond the elastic limit (plasticity)– Large deflections, such as with a loaded fishing rod– Contact between two bodies
ON
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ON
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ON
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Contact between two bodies
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
Stress
Part 1Part 1Part 1Part 1Part 1Part 1
Strain
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Training Manual
Chapter 11 – C. Postprocessing
Review ResultsIN
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• Reviewing results of a stress analysis generally involves:– Deformed shape O
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– Stresses– Reaction forces
ON
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ON
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ON
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Deformed Shape
• Gives a quick indication of whether the loads were applied in the NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
correct direction.
• Legend column shows the maximum displacement, DMX. Part 1Part 1Part 1Part 1Part 1Part 1
• You can also animate the deformation.
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Training Manual
Chapter 11 – C. Postprocessing
…Review ResultsIN
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• To plot the deformed shape:– General Postproc > Plot
R lt D f d Sh
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Results > Deformed Shape– Or use the PLDISP command.
• For animation: ON
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ON
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N TO
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ON
TO A
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– Utility Menu > PlotCtrls > Animate > Deformed Shape
– Or use the ANDISPcommand
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
command.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 11 – C. Postprocessing
…Review ResultsIN
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Stresses
Th f ll i t t i ll il bl f 3 D lid
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• The following stresses are typically available for a 3-D solid model:
– Component stresses — SX, SY, SZ, SXY, SYZ, SXZ (global Cartesian directions by default) O
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ON
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ON
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ON
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N
y )– Principal stresses — S1, S2, S3, SEQV (von Mises), SINT (stress
intensity)
• Best viewed as contour plots which allow you to quickly locate NSYS
NSYS
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NSYS
NSYS
NSYS ---PPP
• Best viewed as contour plots, which allow you to quickly locate “hot spots” or trouble regions.
– Nodal solution: Stresses are averaged at the nodes, showing smooth, continuous contours. Part 1
Part 1Part 1Part 1Part 1Part 1
– Element solution: No averaging, resulting in discontinuous contours.
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Training Manual
Chapter 11 – C. Postprocessing
…Review ResultsIN
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• To plot stress contours:– General Postproc > Plot Results > Contour Plot > Nodal Solu or PLNSOL command
General Postproc > Plot Results > Contour Plot > Element Solu or PLESOL command
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– General Postproc > Plot Results > Contour Plot > Element Solu or PLESOL command
• You can also animate stress contours:– Utility Menu > PlotCtrls > Animate > Deformed Results... or ANCNTR command O
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ON
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ON
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NNSYS
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NSYS
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 11 – C. Postprocessing
…Review ResultsIN
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A Note on PowerGraphics
• It is the default graphics setting (/GRAPH POWER)
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• It is the default graphics setting (/GRAPH,POWER).
• Plots only the visible surfaces and ignores everything “underneath.” O
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ON
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ON
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ON
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• Advantages:– Faster REPLOT, crisp graphics.– Smooth, almost photo-realistic displays.
Prevents stress averaging across material and real
NSYS
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NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
– Prevents stress averaging across material and real constant boundaries.
• To deactivate PowerGraphics (or activate “full graphics”):
Part 1Part 1Part 1Part 1Part 1Part 1
graphics ):– Toolbar > POWRGRPH– Or issue /GRAPH,FULL– Or interactively, Utility Menu>PlotCtrls>Style>
HiddenLineOptions> Graphics Display Method is Full Model
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HiddenLineOptions> Graphics Display Method is...Full Model
Training Manual
Chapter 11 – C. Postprocessing
…Review ResultsIN
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Reaction Forces
Th f th ti f i h di ti t l th
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• The sum of the reaction forces in each direction must equal the sum of applied loads in that direction.
• Best viewed as a listing: ON
TO A
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ON
TO A
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N TO
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ON
TO A
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N TO
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g– General Postprocessor > List Results > Reaction Solution or PRRSOL
command
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
This example had an applied pressureof 1000 psi in the Y direction over a10” x 10” area, which results in reactionforces at nodes where constraints were
Part 1Part 1Part 1Part 1Part 1Part 1
forces at nodes where constraints wereapplied. Notice that the total value offorce in the X and Z directions are zero,and the Y direction is 1000*(10x10) = 0.1e6.
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Training Manual
Chapter 11 – C. Postprocessing
Verify ResultsIN
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It is always a good idea to do a “sanity check” and make sure that the solution is acceptable. What you need to check depends on the type of problem you are solving but here are some typical
yO
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the type of problem you are solving, but here are some typical questions to ask:
• Do FEA results agree with hand calculations or experimental data?
ON
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ON
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N TO
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ON
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data?
• Is the displacement solution correct? Check the FEA displacement solution first since FEA stresses are second order
lt
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPP
results.
• Do the reaction forces balance the applied loads?
Part 1Part 1Part 1Part 1Part 1Part 1
• Where is the maximum stress located?– If it is at a singularity, such as a point load or a re-entrant corner, the
value is generally meaningless. – Are the stress values beyond the elastic limit?
February 7, 2006Inventory #002268
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y– If so, the load magnitudes may be wrong, or you may need to do a
nonlinear analysis.
Training Manual
Chapter 11 – C. Postprocessing
…Verify ResultsIN
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• Is the mesh adequate?– This is always debatable, but you can gain confidence in the mesh by
i ti ti
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using error estimation.– Other ways to check mesh adequacy:
• Plot the element solution (unaveraged stresses) and look for elements with high stress gradients. These regions are candidates
ON
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ON
TO A
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ON
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elements with high stress gradients. These regions are candidates for mesh refinement.
• If there is a significant difference between the nodal (averaged) and element (unaveraged) stress contours, the mesh may be too coarse N
SYS N
SYS N
SYS ---PPPN
SYS N
SYS N
SYS ---PPP
coarse.• Similarly, if there is a significant difference between
PowerGraphics and full graphics stresses, the mesh may be too coarse. Part 1
Part 1Part 1Part 1Part 1Part 1
• Re-mesh with twice as many elements, re-solve, and compare the results. (But this may not always be practical.)
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Training Manual
Chapter 11 – D. Workshops
WorkshopsIN
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• This workshop consists of two problems:11A. Lathe Cutter O
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11B. 2-D Corner Bracket Tutorial
Refer to your Workshop Supplement for instructions. ON
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ON
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ON
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ANN
SYS N
SYS N
SYS ---PPPN
SYS N
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SYS ---PPPPart 1Part 1Part 1Part 1Part 1Part 1
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Chapter 12
Thermal Analysis
Training Manual
Chapter 12 – Thermal Analysis
OverviewIN
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• In this chapter, we will describe the specifics of a thermal analysis.
Th i t f ld
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• The purpose is two-fold:– To reiterate the general analysis procedure.– To introduce you to thermal loads and boundary conditions O
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ON
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ON
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NNSYS
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NSYS ---PPP
NSYS
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 12 – A. Preprocessing
GeometryIN
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Geometry
C ith b t d ithi ANSYS i t d
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• Can either be created within ANSYS or imported.
• Include details to improve results:– Goal is to sufficiently model the thermal mass of the structure.
ON
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ON
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N TO
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ON
TO A
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N TO
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Goal is to sufficiently model the thermal mass of the structure.– Convection loads requires areas be correctly modeled.– Heat generation loads requires the volumes be correctly modeled.
NSYS
NSYS
NSYS ---PPP
NSYS
NSYS
NSYS ---PPPPart 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 12 – A. Preprocessing
MeshingIN
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• Element type• The table below shows commonly used thermal element types.
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• The nodal DOF is: TEMP.
Commonly used thermal element types2-D Solid 3-D Solid 3-D Shell Line Elements2-D Solid 3-D Solid 3-D Shell Line Elements O
N TO
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ON
TO A
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N TO
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ON
TO A
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ON
TO A
N
Linear PLANE55 SOLID70 SHELL57 LINK31, 32, 33, 34SHELL131
Quadratic PLANE77 SOLID90 SHELL132PLANE35 SOLID87
Linear PLANE55 SOLID70 SHELL57 LINK31, 32, 33, 34SHELL131
Quadratic PLANE77 SOLID90 SHELL132PLANE35 SOLID87 N
SYS N
SYS N
SYS ---PPPN
SYS N
SYS N
SYS ---PPP
• Material properties– Minimum requirement is Kx, thermal conductivity for steady state
analysis
Part 1Part 1Part 1Part 1Part 1Part 1
analysis.– Setting preferences to “thermal” limits the Material Model GUI to
display only Thermal properties.
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Inventory #00226812-4
• Real constants / Section properties– Primarily needed for shell and line elements.
Training Manual
Chapter 12 – B. Solution
OverviewIN
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• Thermal loading conditions can be:Temperatures Regions of the model where temperatures are known. O
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Heat flow Points where the heat flow rate is known.
Heat flux Surfaces where the heat flow rate per unit area is known. ON
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ON
TO A
NO
N TO
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ON
TO A
NO
N TO
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Convections Surfaces where heat is transferred to (or from) surroundings by means of convection. Input consists of film coefficient h and bulk temperature of the surrounding fluid Tb. N
SYS N
SYS N
SYS ---PPPN
SYS N
SYS N
SYS ---PPP
fluid Tb.
Heat generation Regions where the volumetric heat generation rate is known. Part 1
Part 1Part 1Part 1Part 1Part 1
Adiabatic surfaces “Perfectly insulated” surfaces where no heat transfer takes place.
Radiation* Surfaces where heat transfer occurs by means of radiation
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Radiation Surfaces where heat transfer occurs by means of radiation. Input consists of emissivity, Stefan-Boltzmann constant, and optionally, temperature at a “space node.”
* Not covered in this course
Training Manual
Chapter 12 – B. Solution
Nodal Coordinate SystemIN
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y
• Unlike the structural analysis displacement and force boundary conditions, the analogous thermal analysis temperature and heat fl b d diti t d d t th d l
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flow boundary conditions are not dependent on the nodal coordinate system.
ON
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ON
TO A
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N TO
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ON
TO A
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N TO
ANN
SYS N
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SYS ---PPPN
SYS N
SYS N
SYS ---PPPPart 1Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – B. Solution
Temperature ConstraintsIN
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Temperature Constraints
• Used to specify a known temperature in the model
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• Used to specify a known temperature in the model.
• To apply displacement constraints :– Main Menu > Solution > Define Loads > Apply > O
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pp yThermal > Temperature
• Choose where you want to apply the constraint.
• Pick the desired entities in the graphics NSYS
NSYS
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g pwindow.
• Then enter the temperature value. Value defaults to zero.
– Or use the D family of commands: DK, DL, Part 1Part 1Part 1Part 1Part 1Part 1
DA, D.
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – B. Solution
Concentrated Heat FlowIN
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• To apply a heat flow, the following information is needed:– node or keypoint number (which you can identify by picking) O
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– heat flow magnitude (which should be consistent with the system of units you are using)
Use: ON
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– Main Menu > Solution > Define Loads > Apply > Thermal > Heat Flow– Or the commands FK or F
NSYS
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Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – B. Solution
Heat FluxIN
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Heat Flux:
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• To apply heat flux:– Main Menu > Solution > Define
Loads > Apply > Thermal > Heat flux• Choose where you want to
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Choose where you want to apply the heat flux-- usually on lines for 2-D models, on areas for 3-D models.
• Pick the desired entities in the
NSYS
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NSYS
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• Pick the desired entities in the graphics window.
• Then enter the heat flux values. Part 1
Part 1Part 1Part 1Part 1Part 1
• Or use the SF family of commands: SFL, SFA, SFE, SF.
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – B. Solution
ConvectionsIN
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Convective Loads
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• To apply a convection:– Main Menu > Solution > Define Loads > Apply
> Thermal > Convection• Choose where you want to apply the
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Choose where you want to apply the convection -- usually on lines for 2-D models, on areas for 3-D models.
• Pick the desired entities in the graphics window
NSYS
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window.• Then enter the film coefficient and bulk
temperature values. • Or use the SF command family: Part 1
Part 1Part 1Part 1Part 1Part 1
ySFL, SFA, SFE, SF.
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – B. Solution
Heat GenerationIN
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Heat Generation
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• To apply heat generation:– Maine Menu > Solution > Define Loads >
Apply > Thermal > Heat Generation• Choose where you want to apply
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ON
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Choose where you want to apply the heat generation-- usually on areas for 2-D models, on volumes for 3-D models.
• Pick the desired entities in the
NSYS
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• Pick the desired entities in the graphics window.
• Then enter the heat generation values. Part 1
Part 1Part 1Part 1Part 1Part 1
• Or use the BF family of commands: BFL, BFA, BFE, BF.
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – B. Solution
Adiabatic SurfacesIN
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O• Adiabatic Surfaces– “Perfectly insulated” surfaces where no heat transfer takes place
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Perfectly insulated surfaces where no heat transfer takes place.– This is the default condition, i.e, any surface with no boundary
conditions specified is automatically treated as an adiabatic surface
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February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – B. Solution
Modifying and Deleting LoadsIN
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Modifying and Deleting Loads
T dif l d l i l l th l d
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• To modify a load value, simply reapply the load with the new value.
• To delete loads: ON
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ON
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– Main Menu > Solution > Define Loads > Delete– When you delete solid model loads, ANSYS also
automatically deletes all corresponding finite element loads N
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loads.
Part 1Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – B. Solution
Solutions OptionsIN
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Steady State vs. Transient Analysis
A t d t t l i th t th l di diti h
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• A steady state analysis assumes that the loading conditions have “settled down” to a steady level, with little or no time dependency.
• A transient analysis conditions that are changing with time. ON
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y g g
• For example, consider the analysis of a clothes iron which takes 1 minute to reach a constant temperature N
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– The analysis of the clothes iron for the first 1 minute of operation would be transient.After a constant temperature is reached the analysis would be steady
Part 1Part 1Part 1Part 1Part 1Part 1
– After a constant temperature is reached, the analysis would be steady state.
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Training Manual
Chapter 12 – C. Postprocessing
Review ResultsIN
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O• Reviewing results of a thermal analysis generally involves:– temperature distribution
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temperature distribution– thermal gradient distribution– thermal flux distribution O
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February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – C. Postprocessing
…Review ResultsIN
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Temperature Distribution:
• To plot temperature contours OD
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– General Postproc > Plot Results > Contour Plot > Nodal Solution > Temperature– Or use the PLNSOL command.
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Training Manual
Chapter 12 – C. Postprocessing
…Review ResultsIN
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Thermal Gradients:
• To plot thermal gradient contours: OD
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p g– General Postproc > Plot Results > Contour Plot > Nodal Solu or PLNSOL command– General Postproc > Plot Results > Contour Plot > Element Solu or PLESOL command
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February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – C. Postprocessing
…Review ResultsIN
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Thermal Flux:
• To plot thermal gradient contours: OD
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p g– General Postproc > Plot Results > Contour Plot > Nodal Solu or PLNSOL command– General Postproc > Plot Results > Contour Plot > Element Solu or PLESOL command
ON
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Training Manual
Chapter 12 – C. Postprocessing
…Review ResultsIN
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Reaction Forces
Th f th ti h t fl t b l th f th
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• The sum of the reaction heat flows must balance the sum of the applied heat flows
• Best viewed as a listing: ON
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ON
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g– General Postprocessor > List Results > Reaction Solution or PRRSOL
command
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Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – C. Postprocessing
Verify ResultsIN
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It is always a good idea to do a “sanity check” and make sure that the solution is acceptable. What you need to check depends on th t f bl l i b t h t i l
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the type of problem you are solving, but here are some typical questions to ask:
• Do FEA results agree hand calculations or experimental data? ON
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g p
• Is the temperature solution correct? Check the FEA temperature solution first since FEA heat fluxes are second order results. N
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• Do the reaction heat flows balance the applied heat flows?
• Where is the maximum heat flux located? Part 1Part 1Part 1Part 1Part 1Part 1
– If it is at a singularity, such as a point load or a re-entrant corner, the value is generally meaningless.
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Training Manual
Chapter 12 – C. Postprocessing
…Verify ResultsIN
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• Is the mesh adequate?– This is always debatable, but you can gain confidence in the mesh by
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using error estimation.– Other ways to check mesh adequacy:
• Plot the element solution (unaveraged stresses) and look for elements with high heat flux gradients. These regions are
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elements with high heat flux gradients. These regions are candidates for mesh refinement.
• If there is a significant difference between the nodal (averaged) and element (unaveraged) heat flux contours, the mesh may be too coarse N
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coarse.• Similarly, if there is a significant difference between
PowerGraphics and full graphics heat flux, the mesh may be too coarse. Part 1
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• Re-mesh with twice as many elements, re-solve, and compare the results. (But this may not always be practical.)
February 7, 2006Inventory #002268
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Training Manual
Chapter 12 – D. Workshop
WorkshopIN
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• Refer to your Workshop Supplement for instructions on:W12. Axisymmetric Pipe with Fins O
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February 7, 2006Inventory #002268
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Chapter 13
Postprocessing
Training Manual
Chapter 13 - Postprocessing
OverviewIN
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• There are many ways to review results in the general postprocessor (POST1), some of which have already been
d
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covered.
• In this chapter, we will explore two additional methods — query picking and path operations — and also introduce you to the O
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p g p p yconcepts of results transformation, error estimation, and load case combination.
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
A. Query PickingIN
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• Query picking allows you to “probe” the model for stresses, displacements, or other results quantities at any picked location.
y gO
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• You can also quickly locate the maximum and minimum values of the item being queried. O
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• Available only through the GUI (no commands):– General Postproc > Query Results > Nodal or Element or Subgrid Solu– Choose a results quantity and press OK N
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PowerGraphicsOFF
PowerGraphicsON
Part 1Part 1Part 1Part 1Part 1Part 1
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Chapter 13 - Postprocessing
…Query PickingIN
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– Then pick any point in the model to see the results value at that point.• Min and Max will show the value at the minimum and maximum
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points.• Use Reset to clear all values and start over.• Notice that the entity number, its location, and the results value are
also shown in the Picker.
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also shown in the Picker.
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generate text
Part 1Part 1Part 1Part 1Part 1Part 1
annotation
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Query PickingIN
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• Demo:– Continue from the last multi-load-step solution of rib.db
Pl t SEQV f l d t 1
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– Plot SEQV for load step 1– Query “Nodal Solu” SEQV at several locations, including MIN & MAX. (Switch to
full graphics if needed.)– Switch to PowerGraphics and query “Subgrid Solu.” O
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
B. Results Coordinate SystemIN
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• All direction-dependent quantities that you view in POST1, such as component stresses, displacements, and reaction forces, are
t d i th lt di t t (RSYS)
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reported in the results coordinate system (RSYS).
• RSYS defaults to 0 (global Cartesian). That is, POST1 transforms all results to global Cartesian by default, including results at O
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g y , g“rotated” nodes.
• But there are many situations — such as pressure vessels and spherical structures where you need to check the results in a
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spherical structures — where you need to check the results in a cylindrical, spherical, or other local coordinate system.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Results Coordinate SystemIN
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• To change the results CS to a different system, use:
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– General Postproc > Options for Outp…– or the RSYS command
All b t t l t li ti i k t ill t
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All subsequent contour plots, listings, query picks, etc. will report the values in that system.
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Part 1Part 1Part 1Part 1Part 1
Default orientation RSYS,0
Local cylindrical system RSYS,11
Global cylindrical system RSYS,1
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Chapter 13 - Postprocessing
…Results Coordinate SystemIN
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• RSYS,SOLU– Sets the results CS to “As calculated.”
yO
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– All subsequent contour plots, listings, query picks, etc. will report the values in the nodal and element coordinate systems. N
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• DOF results and reaction forces will be in the nodal CS.• Stresses, strains, etc. will be in the element CS. (The orientation of
the element CS depends on the element type and the ESYS attribute of the element Most solid elements for example default
Part 1Part 1Part 1Part 1Part 1Part 1
attribute of the element. Most solid elements, for example, default to global Cartesian.)
– Not supported by PowerGraphics.
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Training Manual
Chapter 13 - Postprocessing
C. Path OperationsIN
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• Another way to review results is via path operations, which allow you to: O
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– map results data onto an arbitrary “path” through the model– perform mathematical operations along the path, including integration
and differentiation– display a “path plot” — see how a result item varies along the path
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display a path plot see how a result item varies along the path
• Available only for models containing 2-D or 3-D solid elements or shell elements. N
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Chapter 13 - Postprocessing
…Path OperationsIN
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• Three steps to produce a path plot:– Define a path O
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– Map data onto the path– Plot the data
1 Define a Path
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1. Define a Path– Requires the following information:
• Points defining the path (2 to 1000). You can use existing nodes or locations on the working plane. N
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• Path curvature, determined by the active coordinate system (CSYS).
• A name for the path. Part 1Part 1Part 1Part 1Part 1Part 1
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Chapter 13 - Postprocessing
…Path OperationsIN
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1. Define a Path (cont’d)– First activate the desired coordinate system (CSYS). O
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– General Postproc > Path Operations > Define Path > By Nodes or On Working Plane
• Pick the nodes or WP locations that form the desired path, and press OK O
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p• Choose a path name. The nSets and nDiv fields are best left to
default in most cases.
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Training Manual
Chapter 13 - Postprocessing
…Path OperationsIN
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O
2. Map Data onto Path– General Postproc > Path Operations > Map onto Path (or PDEF
command)
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command)• Choose desired quantity, such as SEQV.• Enter a label for the quantity, to be used on plots and listings.
– You can now display the path if needed
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– You can now display the path if needed.• General Postproc > Path Operations > Plot Paths• (or issue /PBC,PATH,1 followed by NPLOT or EPLOT)
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Path OperationsIN
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3. Plot the Data– You can plot path items either on a graph: O
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• PLPATH or General Postproc > Path Operations > Plot Path Item > On Graph
– or along path geometry:• PLPAGM or General Postproc > Path Operations > Plot Path Item >
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• PLPAGM or General Postproc > Path Operations > Plot Path Item > On Geometry
NSYS
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Path OperationsIN
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• ANSYS allows you to define multiple paths, each with a unique name that you assign. Only one
th b ti t ti
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path can be active at a time.
• Besides plots and listings, there are many other path capabilities, including: O
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p p , g– Stress linearization — used in the pressure vessel
industry to decompose stress along a path into its membrane and bending components.Calculus functions used in fracture mechanics to N
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– Calculus functions — used in fracture mechanics to calculate J-integrals and stress concentration factors. Also useful in thermal analyses to calculate the heat lost or gained across a path.D t d t d d t d id l i
Part 1Part 1Part 1Part 1Part 1Part 1
– Dot products and cross products — used widely in electromagnetics analyses to operate on vector quantities.
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Training Manual
Chapter 13 - Postprocessing
…Path OperationsIN
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• Demo:– Continue with rib postprocessing…
Pl t d th it h t CSYS 1 if d i d
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– Plot nodes, then switch to CSYS,1 if desired– Define a path using nodes– Map SX or SEQV or other data onto path– Plot the path itself O
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– Plot the path item on graph and on geometry– Define a second path elsewhere in the model and show how to toggle between
the two.
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Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 – Postprocessing
D. Error EstimationIN
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• The finite element solution calculates stresses on a per-elementbasis, i.e, stresses are individually calculated in each element. O
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• When you plot nodal stress contours in POST1, however, you will see smooth contours because the stresses are averaged at the nodes. O
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If you plot the element solution, you will see unaveraged data, which shows the discontinuity between elements. N
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σavg = 1100• The difference between averaged and unaveraged stresses gives an indication Part 1
Part 1Part 1Part 1Part 1Part 1Elem 1 Elem 2
σ = 1200σ = 1000
σ = 1300σ = 1100
of how “good” or how “bad” the mesh is. This is the basis for error estimation.
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σavg = 1200
Training Manual
Chapter 13 - Postprocessing
…Error EstimationIN
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• Error estimation is available only in POST1 and is valid only for:– linear static structural and linear steady-state thermal analyses O
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– solid elements (2-D and 3-D) and shell elements– Full Graphics (not PowerGraphics)
If these conditions are not met ANSYS automatically turns off
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If these conditions are not met, ANSYS automatically turns off error estimation calculations.
• To manually activate or deactivate error estimation, use NSYS
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– ERNORM,ON/OFF– or General Postproc > Options for Outp
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Error EstimationIN
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• POST1 calculates the following error measures.– Stress analysis: O
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• percentage error in energy norm (SEPC)• element stress deviations (SDSG)• element energy error (SERR) O
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• maximum and minimum stress bounds (SMXB, SMNB)– Thermal analysis:
• percentage error in energy norm (TEPC)l t th l di t d i ti (TDSG)
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• element thermal gradient deviations (TDSG)• element energy error (TERR)
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Error EstimationIN
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Percentage error in energy norm (SEPC)
SEPC i h ti t f th t ( di l t
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• SEPC is a rough estimate of the stress error (or displacement, temperature, or thermal flux) over the entire set of selected elements. O
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• Can be used to compare similar models of similar structures subjected to similar loadings.
• SEPC is shown in the legend column of deformed shape displays
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• SEPC is shown in the legend column of deformed shape displays. You can list it manually using PRERR or General Postproc > List Results > Percent Error.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Error EstimationIN
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• As a general rule of thumb, look for SEPC to be 10% or l If it i hi h th SEPC = 35.149
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less. If it is higher, then:– Check for point loads or
other stress singularities and unselect elements in the
SEPC 35.149
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vicinity.– If it is still higher, plot the
element energy error. The elements with high values of N
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genergy error are candidates for mesh refinement. SEPC = 3.484
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Error EstimationIN
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Element stress deviations (SDSG)
• SDSG is a measure of the amount by
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• SDSG is a measure of the amount by which an element’s stress disagrees with the stress averages at its nodes.
• You can plot SDSG contours using
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• You can plot SDSG contours using PLESOL,SDSG or General Postproc > Plot Results > Contour Plot > Element Solu...
• A high value of SDSG is not necessarily NSYS
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A high value of SDSG is not necessarily bad, especially if it is a small percentage of the nominal stresses in the structure.
For example this plate-with-a-hole model SDSG t l ti f i t t
Part 1Part 1Part 1Part 1Part 1Part 1
For example, this plate-with-a-hole model shows only a 1.5% stress deviation in the region of interest.
SDSG at location of interest = ~450 psi, which is ~1.5% of ~30,000 psi nominal stress
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Training Manual
Chapter 13 - Postprocessing
…Error EstimationIN
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Element energy error (SERR)
SERR i th i t d ith th t i t h t th
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• SERR is the energy associated with the stress mismatches at the nodes of the element. This is the basic error measure from which the other error quantities are derived. SERR has units of energy. O
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• To plot SERR contours, issue PLESOL,SERR or General Postproc > Plot Results > Contour Plot > Element Solu
• Generally the elements with the highest SERR are candidates for
NSYS
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• Generally, the elements with the highest SERR are candidates for mesh refinement. However, since SERR will always be highest at stress singularities, be sure to unselect those elements first.
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Error EstimationIN
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Stress bounds (SMXB and SMNB)
Th t b d h l d t i th t ti l ff t f
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• The stress bounds can help you determine the potential effect of mesh discretization error on the maximum stress.
• They are displayed on stress contour plots in the legend column ON
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y p y p gas SMXB (upper bound) and SMNB (lower bound).
• The bounds are not estimates of the actual maximum and minimum but they do define a “confidence band ” Without other
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minimum, but they do define a “confidence band.” Without other supporting verification, you have no basis for believing that the true maximum stress is below SMXB.
Part 1Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Error EstimationIN
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O
• Caution: If you don’t unselect elements near stress singularities, the stress bounds are meaningless, as shown below. O
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SMXB = 6,401SMXB = 15,750
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
E. Load Case CombinationsIN
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• Whenever you solve multiple load steps, the results of each load step are stored as separate sets on the results file (identified by load O
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step number).
• A load case combination is an operation between two sets of results which are called load cases
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results, which are called load cases.– The operation occurs between one load case in the database and the
second load case on the results file.– The result of the operation — the combined load case — is stored back N
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in the database.
Part 1Part 1Part 1Part 1Part 1Part 1
Load case in database Load case Combined load case in database
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Load case in database(computer memory)
Load caseon results file
Combined load case in databaseoverwrites previous contents
Training Manual
Chapter 13 - Postprocessing
…Load Case CombinationsIN
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Typical procedure:
1 C t th l d
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1. Create the load cases
2. Read one load case into the database ON
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ON
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3. Perform the desired operation
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Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Load Case CombinationsIN
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Create Load Cases
A l d i l t i t t t
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• A load case simply acts as a pointer to a set of results. It requires two pieces of information:
– a unique ID number
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a unique ID number– the results set it represents (load step and
substep number)
• Use the LCDEF command or General
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• Use the LCDEF command or General Postproc > Load Case > Create Load Case
Part 1Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Load Case CombinationsIN
TRO
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Read One Load Case into the Database (memory)
Si l id tif th lt t b it l d
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• Simply identify the results set by its load case number using LCASE or General Postproc > Load Case > Read Load Case. O
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• Or use one of the standard “Read Results” choices in the postprocessor (SET command).
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Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Load Case CombinationsIN
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Perform the Desired Operation
M ti il bl h i
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• Many operations are available as shown in the menu here.
• Use the LCOPER command or General ON
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Postproc > Load Case > Add, Subtract, etc.
• Remember that the results of the operation are stored in the database (memory) The
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are stored in the database (memory). The combined load case is identified on plots and listings as number 9999.
Part 1Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Load Case CombinationsIN
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• There are two useful options to save the combined load case:
Write a load case file
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– Write a load case file– Append the load case to the results
file
• Writing a load case file (LCWRITE ON
TO A
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ON
TO A
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ON
TO A
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or General Postproc > Write Results) creates a file that is similar to, but much smaller than the results file.
• The Append option (RAPPND or NSYS
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pp p (General Postproc > Load Case > Write Load Case) allows you to add the combined load case to the results file and identify it with a Part 1
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ygiven load step number and time value.
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
F. WorkshopsIN
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• Refer to your Workshop Supplement for instructions:W13A. Connecting Rod O
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W13B. Spherical ShellW13C. Axisymmetric Fin with Multiple Load Steps
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February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
G. Results ViewerIN
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• The Results Viewer is a specialized postprocessing menu and graphic system.
Fast graphics for large models or models that have many time steps
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– Fast graphics for large models or models that have many time steps– Easy to use menu system for quick results viewing
ON
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February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Results ViewerIN
TRO
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• Can be created two different ways …– Use the POUTRES command before solving
to write a jobname pgr file during solution
OD
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to write a jobname.pgr file during solution.– Main Menu > Solution > Load Step Opts >
Output Ctrls > PGR File
ON
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ON
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Hold CTRL key for multiple selection Part 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Results ViewerIN
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– Use the PGWRITE command after solution to write a jobname.pgr file.
– General Postproc > Write PGR File
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General Postproc > Write PGR File
ON
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ON
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ON
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February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Results ViewerIN
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• Open the Results Viewer from the General Post Processor.
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Part 1Part 1Part 1Part 1Part 1
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Results ViewerIN
TRO
INTR
OIN
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INTR
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INTR
O
Nodal/element/vector/trace results plots
A i t i
Time History Variable Viewer
Report Image
Capture
Report Animation Capture O
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Element Plot
Animate using PNG files Report
Listing Capture O
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AN
ON
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N TO
AN
ON
TO A
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N TO
AN
ON
TO A
N
Report Table
Capture
NSYS
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NSYS
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Locator Time Substep
Raise Hidden
Part 1Part 1Part 1Part 1Part 1Part 1Query Results
ListImage CaptureReport Generation
Mode
Load Step
Substep
February 7, 2006Inventory #002268
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List Results
Mode
Training Manual
Chapter 13 - Postprocessing
…Results ViewerIN
TRO
INTR
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INTR
O
• The graphics window becomes “Context Sensitive”.
OD
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Context-sensitive graphics window
ON
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ON
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AN
ON
TO A
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N TO
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Context sensitive graphics window
NSYS
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NSYS
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Right Click on Model
Part 1Part 1Part 1Part 1Part 1Part 1
Right Click on Model
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Results ViewerIN
TRO
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INTR
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INTR
O
Context-sensitive graphics window
OD
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g p
ON
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ON
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AN
ON
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N TO
ANN
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February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Results ViewerIN
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Context-sensitive graphics window
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February 7, 2006Inventory #002268
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Right Click on Contour Bar
Training Manual
Chapter 13 – Postprocessing
H. Variable ViewerIN
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• The Variable Viewer is a specialized tool allowing one to postprocess results with respect to time. O
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• The Variable Viewer can be started by:– Simply opening the Time History Postprocessor, or– Main Menu > TimeHist Postproc > Variable Viewer O
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February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Variable ViewerIN
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1 2 3 4 5 6 7 8 9 10 11
Add variable button1
Delete variable button2
Graph variable button3 OD
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List variable button4
Properties button5
Import data button6 ON
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Export data button7
Export data type8
Clear Time History Data9
R f h Ti Hi D10
1413 NSYS
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Refresh Time History Data10
Variable name input area
1116
Real/Imaginary Components
Variable list12
13
15
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17Variable name input area
Expression input area14
Defined APDL variables15
Defined Post26 variables16
13
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17 Calculator
Training Manual
Chapter 13 - Postprocessing
…Variable ViewerIN
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100kgx
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k = 36kN/m
y Part 1Part 1Part 1Part 1Part 1Part 1
F
⎩⎨⎧
<>
=0,0
0,4000t
tNF
y
February 7, 2006Inventory #002268
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⎩ < 0,0 t
Training Manual
Chapter 13 - Postprocessing
I. Report GeneratorIN
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• A time consuming part of any analysis is documenting the
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model and results. This procedure has been partially automated through the implementation of the ANSYS O
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pReport Generator.
• The Report Generator allows the user to quickly capture
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the user to quickly capture pictures, listings, tables, and other pertinent information.
Part 1Part 1Part 1Part 1Part 1Part 1
• It also facilitates the creation of an HTML formatted file ready to be distributed to colleagues or posted to a web site
February 7, 2006Inventory #002268
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posted to a web site.
Training Manual
Chapter 13 - Postprocessing
…Report GeneratorIN
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• Launching the Report Generator will shrink the graphics window and set the b k d t hit
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background to white.
• The “Capture Tool” will be opened allowing the user to grab plots, listings, O
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g g p , g ,and tables.
– Utility Menu> File> Report Generator…or
i ’ idl t t lb t ’
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– ~eui,’euidl::report::toolbar::create’or
– Select on the Icon Toolbar.
Part 1Part 1Part 1Part 1Part 1Part 1
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Capture Tool
Training Manual
Chapter 13 - Postprocessing
…Report GeneratorIN
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OTable • Capture Tool
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Animation Capture(multiple PNG files)
Capture
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Image Capture(single PNG file)
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Settings
Part 1Part 1Part 1Part 1Part 1Part 1HTML Report
AssemblerLi ti
The Log File records all captures!
The Log File records all captures!
February 7, 2006Inventory #002268
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Listing Capture
Training Manual
Chapter 13 - Postprocessing
…Report GeneratorIN
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HTML Assembler . . .
• A tool that allows quick
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• A tool that allows quick organization of ANSYS graphics, tables, listings .
• Log file can be used as an HTML
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• Log file can be used as an HTML template.
– utilize parameter substitution
• The generated HTML file can be NSYS
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• The generated HTML file can be used with Netscape Composer, Microsoft FrontPage, or any other HTML editor to finalize the report. Part 1
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Training Manual
Chapter 13 - Postprocessing
…Report GeneratorIN
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• Insert TEXT
• Insert any HTML FILE
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• Insert any HTML FILE– possibly created outside ANSYS
• Insert an IMAGE possibly one from an external
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– possibly one from an external source like a digital photo
• Insert DYNAMIC DATA information specific to your current N
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– information specific to your current ANSYS run like version, run time, etc.
• Insert a Report Heading Part 1Part 1Part 1Part 1Part 1Part 1
p g– Including your name, analysis title,
date, and company name
February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Report GeneratorIN
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• Insert information grabbed using the Capture Tool O
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• Report Images– Contour plots, element plots,
volume plots, graphs ON
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• Report Tables– Material properties, reaction forces,
etc.
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• Report Lists– Stress along a path, constraints,
etc. Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Chapter 13 - Postprocessing
…Report GeneratorIN
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• Preview the report
• Delete sections of the report
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• Delete sections of the report
• Move sections of the report up or down O
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February 7, 2006Inventory #002268
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Training Manual
Chapter 13 - Postprocessing
…Report GeneratorIN
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Training Manual
Chapter 13 - Postprocessing
J. WorkshopsIN
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• Refer to your Workshop Supplement for instructions:W13D. Results Viewer O
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W13E. Report Generator
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Chapter 14
Short Topics
Training Manual
Chapter 14 – Short Topics
OverviewIN
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• In this chapter, we will present some general tips and “tricks” on how to use ANSYS more efficiently O
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Training Manual
Chapter 14 – Short Topics
A. Toolbar and AbbreviationsIN
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• An abbreviation is a short-cut to commonly used functions. It is a character string that represents one or more ANSYS commands. O
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• Whenever you define an abbreviation, it appears as a button in the ANSYS Toolbar, giving you one-button access to the desired function. O
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• There are five predefined abbreviations when you first start ANSYS, but you can modify them or add your own — up to 100 total abbreviations
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total abbreviations.
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Training Manual
Chapter 14 – Short Topics
…Toolbar and AbbreviationsIN
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• As an example, to display line numbers on a line plot, you would need to do the following:
Utility Menu > PlotCtrls > Numbering > Line numbers On > OK
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– Utility Menu > PlotCtrls > Numbering… > Line numbers On > OK– Utility Menu > Plot > Lines
Later, to turn off line numbers, you would have to use the same menus again
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again.
• Instead, you could define three abbreviations:– LINE_ON for the command string *ABBR,LINE_ON,/pnum,line,on
LINE OFF f *ABBR LINE OFF / li ff
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– LINE_OFF for *ABBR,LINE_OFF,/pnum,line,off– LPLOT for the command string *ABBR,LPLOT,lplot
and simply press the appropriate combinations of buttons in the toolbar to turn line numbering on or off For example hit followed by to
Part 1Part 1Part 1Part 1Part 1Part 1
turn line numbering on or off. For example, hit followed by to turn line numbering on and display a line plot.
February 7, 2006Inventory #002268
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Training Manual
Chapter 14 – Short Topics
…Toolbar and AbbreviationsIN
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• The following information is needed for an abbreviation:– The short-cut name
The command string it represents To find out the command for a particular
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– The command string it represents. To find out the command for a particular function, first execute the function using the GUI, then list the log file (Utility Menu > List > Files > Log File).
• Use the *ABBR command to define abbreviations:
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Use the ABBR command to define abbreviations:
– *ABBR, name, command_string
A convenient dialog box is available for this: NSYS
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A convenient dialog box is available for this:– Utility Menu > MenuCtrls > Edit Toolbar…– or Utility Menu > Macro > Edit Abbreviations…
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Training Manual
Chapter 14 – Short Topics
…Toolbar and AbbreviationsIN
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• Abbreviations are stored in the standard ANSYS database, so they get saved to the .db file when you save the database. O
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• You can also write abbreviations to an ASCII file, jobname.abbr:– Utility Menu > MenuCtrls > Save Toolbar…– or Utility Menu > Macro > Save Abbr
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or Utility Menu > Macro > Save Abbr…– or ABBSAV command
• To restore abbreviations from a file, use: NSYS
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– Utility Menu > MenuCtrls > Restore Toolbar…– or Utility Menu > Macro > Restore Abbr…– or ABBRES command Part 1
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Training Manual
Chapter 14 – Short Topics
…Toolbar and AbbreviationsIN
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• By creating a series of .abbr files and with a clever use of ABBSAVand ABBRES functions, you can create “nested” toolbars —b tt th t b i ti l t f b tt d t
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buttons that bring up an entirely new set of buttons — and put together a menu of your own!
• Once you master the ANSYS command language, there is virtually ON
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y g g , yno limit to the power and usefulness of abbreviations!
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February 7, 2006Inventory #002268
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Training Manual
Chapter 14 – Short Topics
…Toolbar and AbbreviationsIN
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• Demo:– Resume rib.db O
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– Create abbreviations EPLOT, APLOT, LPLOT, KPLOT– Delete KPLOT abbreviation– Save abbreviations to file.abbr, then list the file
Now list the log file and show the ABBSAVE command (This is how
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– Now list the log file and show the ABBSAVE command. (This is how you can find out the commands for a given function.)
– Resume rib.db again– Restore abbreviations from file.abbr and use the buttons N
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Training Manual
Chapter 14 – Short Topics
B. Start FileIN
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• Whenever you start ANSYS, it reads a start file called start100.ans(or start90.ans, start81.ans, etc. depending on ANSYS revision). O
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• You can include any commands in the start file. The most common ones are abbreviation definitions. O
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• ANSYS checks for the start file first in the working directory and then in your home directory. If no file is found, it will read the “default” start file in the ANSYS apdl directory (..\v100\ansys\apdl).
Th “d f lt” t t fil t i l t d bb i ti ll f
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– The “default” start file contains several suggested abbreviations, all of them commented out. You can make a copy of it and “uncomment” the ones you want to use.
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Training Manual
Chapter 14 – Short Topics
C. APDLIN
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• APDL is an acronym for ANSYS Parametric Design Language, a powerful scripting language that allows you to parameterize your
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model and automate common tasks.
• Using APDL, you can:– input model dimensions, material properties, etc. in terms of
ON
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input model dimensions, material properties, etc. in terms of parameters rather than numbers.
– retrieve information from the ANSYS database, such as a node location or maximum stress.perform mathematical calculations among parameters including
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– perform mathematical calculations among parameters, including vector and matrix operations.
– define abbreviations (short cuts) for frequently used commands or macros. Part 1
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– create a macro to execute a sequence of tasks, with if-then-else branching, do-loops, and user prompts.
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Training Manual
Chapter 14 – Short Topics
D. Defining ParametersIN
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• To define a parameter, use the format
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Name=Value– Can be typed in the input window or in
the Scalar Parameters dialog (Utility Menu > Parameters > Scalar Parameters...) O
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– Name is the parameter name, thirty-two alphanumeric characters or less.
– Value may be a number, a previously defined parameter a mathematical N
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defined parameter, a mathematical function, a parametric expression, or a character string (enclosed in single quotes).Can be kept in start## ans file for
Part 1Part 1Part 1Part 1Part 1Part 1
– Can be kept in start##.ans file for commonly used parameters, such as PI = acos(-1)
dist=sqrt((y2-y1) 2+(x2-x1) 2)slope=(y2-y1)/(x2-x1)theta=atan(slope)jobname=‘proj1’ N
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p ( ) j p j
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See *SET command for a list of valid function
Training Manual
Chapter 14 – Short Topics
...Defining ParametersIN
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g
• The examples above are scalar parameters, which have a single value — either numeric or character. O
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• ANSYS also supports array parameters, which have multiple values. Both numeric and character arrays are available. Array parameters will not be discussed in this course. O
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p
28 7 j b1
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28.7-9.2-2.151.0
xvalues =
job1job2job3job4
filnam = Part 1Part 1Part 1Part 1Part 1Part 1
0.0 jjob5
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Training Manual
Chapter 14 – Short Topics
...Defining ParametersIN
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O
g
Some naming rules:
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• Parameter names must be thirty-two characters or less, beginning with a letter.
• Only letters, numbers, and the underscore character are ON
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y , , _allowed.
• Avoid underscore _ as starting character… reserved for ANSYS use
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use.
• Names are not case-sensitive, i.e, “RAD” and “Rad” are the same. All parameters are internally stored in capital letters. Part 1
Part 1Part 1Part 1Part 1Part 1• Avoid common ANSYS labels such as STAT, DEFA, and ALL.
February 7, 2006Inventory #002268
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Training Manual
Chapter 14 – Short Topics
E. Using ParametersIN
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g
• To use a parameter, simply enter its name in the appropriate field in the dialog box or on the command. O
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• For example, to define a rectangle using the parameters w=10 and h=5,
– you can use the menu: ON
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you can use the menu:Main Menu > Preprocessor > Modeling > Create > Area > Rectangle > By 2 Corners
– or commands: NSYS
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/prep7blc4,,,w,h
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Training Manual
Chapter 14 – Short Topics
...Using ParametersIN
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• Whenever you use parameters, ANSYS immediately substitutes their values.
The rectangle in the previous example is stored as a 10x5 area, ON
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g p p ,not as w x h. That is, if you change the value of w or h aftercreating the rectangle, the area will NOT be updated.
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Training Manual
Chapter 14 – Short Topics
...Using ParametersIN
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• Other examples of using parameters:jobname=‘proj1’ O
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/filnam,jobname ! Jobname/prep7youngs=30e6 O
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y gmp,ex,1,youngs ! Young’s modulusforce=500fk,2,fy,-force ! Force at KP 2 N
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yfk,6,fx,force/2 ! Force at KP 6
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Training Manual
Chapter 14 – Short Topics
F. Retrieving Database InformationIN
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• To retrieve information from the database and assign it to a parameter, use the *GET command or Utility Menu > Parameters > G t S l D t
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Get Scalar Data...
• A vast amount of information is available, including model and results data. Refer to the *GET command description for details. O
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Training Manual
Chapter 14 – Short Topics
...Retrieving Database InformationIN
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• Examples:*get,x1,node,1,loc,x ! x1 = X coordinate of node 1 [CSYS]* O
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/post1*get,sx25,node,25,s,x ! sx25 = X stress at node 25 [RSYS]**get,uz44,node,44,u,z ! uz44 = UZ displacement at node 44 [RSYS]*nsort s eqv ! Sort nodes by von Mises stress
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nsort,s,eqv ! Sort nodes by von Mises stress*get,smax,sort,,max ! smax = maximum of last sortetable,vol,volu ! Store element volumes as volssum ! Sum all element table columns N
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*get,totvol,ssum,,vol ! totvol = sum of vol column
*CSYS = In the active coordinate system (CSYS) Part 1Part 1Part 1Part 1Part 1Part 1
RSYS = In the active results coordinate system (RSYS)
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Chapter 14 – Short Topics
...Retrieving Database InformationIN
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• Some data can be retrieved with a get function.
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Examples:x1=nx(1) ! x1 = X coordinate of node 1 [CSYS]*nn=node(2.5,3,0) ! nn = node at or near (2.5,3,0) [CSYS]*/post1
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/post1ux25=ux(25) ! ux25 = UX at node 25 [RSYS]*temp93=temp(93) ! temp93 = temperature at node 93width=distnd(23,88) ! width = distance between nodes 23 & 88 N
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RSYS = In the active results coordinate system (RSYS)
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Chapter 14 – Short Topics
...Retrieving Database InformationIN
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• You can use a get function directly in a field, just like a parameter. For example: O
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k,10,kx(1),ky(3) ! KP 10 at X of KP 1, Y of KP 3 [CSYS]*k,11,kx(1)*2,ky(3) ! [CSYS]*f,node(2,2,0),fx,100 ! FX force at node(2,2,0) [CSYS]* O
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*CSYS = In the active coordinate system (CSYS)
Training Manual
Chapter 14 – Short Topics
G. Batch ModeIN
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• In batch mode, ANSYS reads commands from an input file you supply, and writes responses to an output file. The process runs i th b k d f i t f th k
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in the background, freeing up your computer for other work.
• Of the three main phases of an analysis — preprocessing, solution, postprocessing — the solution phase is best suited for O
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, p p g pbatch mode. Thus a batch input file could be as simple as:
/batchresume,... ! Resume database from preprocessing session N
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/solusolvefinish Part 1
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Chapter 14 – Short Topics
H. Input filesIN
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• ANSYS is a command-driven program and can accept commands from several sources:
f GUI di l b ( hi h i l “ d” d t ANSYS
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– from GUI dialog boxes (which simply “send” commands to ANSYS when you press OK or Apply)
– from the keyboard– from input files O
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command sequence:– Utility Menu > File > Read Input from…– or the /INPUT command
Part 1Part 1Part 1Part 1Part 1Part 1
(The start file is just an input file that is automatically read at start-up by a built-in /input command.)
• The path of the input file can have a maximum length of 250
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• The path of the input file can have a maximum length of 250 characters (path and filename) plus an eight character extension
Training Manual
Chapter 14 – Short Topics
…Input filesIN
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• For example, you can create a file called rectangle.inp containing the following lines: O
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/prep7 ! Enter preprocessorrect,0,3,0,1 ! Create a 3x1 rectangleaplot O
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and then read it into ANSYS:/input,rectangle,inp ! or File > Read Input from…
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• The ! character above indicates a comment and can be used to:– annotate the input file with explanations.– “comment out” an entire command. Part 1
Part 1Part 1Part 1Part 1Part 1• Note: Cutting and pasting commands into the Input window is
NOT a supported feature.
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Training Manual
Chapter 14 – Short Topics
…Input filesIN
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• When an input file ( or a macro ) is executed in the wrong module, repeated warnings occur. Upon encountering five such warnings
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a dialog box appears allowing you to stop and exit cleanly.
• You can use the log file jobname.log as an input file. Keep in mind the following points when you do this: O
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g p y– The log file records all commands executed during an ANSYS session.– Always use a copy of the log file, don’t just rename it.– It may be helpful to edit the copy first and: N
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• add descriptive comments• “clean it up” by removing erroneous commands and graphics
• *ASK prompts the user for input and assigns the response to a parameter. For example, you can modify rectangle.inp as follows:
/prep7 ! Enter preprocessor*ask w WIDTH OF RECTANGLE 3
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ask,w,WIDTH OF RECTANGLE,3rect,0,w,0,1 ! Create a wx1 rectangleaplot
Wh i t thi fil i t ANSYS ill th t
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When you input this file into ANSYS, you will see the prompt shown below. Your response, say 5.2, is assigned to the parameter w, which is used in the subsequent RECT command.
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Chapter 14 – Short Topics
…Input filesIN
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• *ASK, Par, Query, DVAL– Par is the parameter name to which the response value is assigned. O
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– Query is the prompt string, up to 32 characters. The word ENTER automatically appears as the first word of the prompt.
– DVAL is the default value assigned to Par if the response is blank. ON
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Training Manual
Chapter 14 – Short Topics
I. Session EditorIN
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• Session Editor– Powerful ANSYS “Undo” O
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– ANSYS keeps a running copy of your log file from your last save command.
– By modifying the values in the Session Editor window and clicking OK, the modified commands O
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g ,are read back into ANSYS.
– Main Menu > Session Editor…
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Chapter 14 – Short Topics
SummaryIN
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Summary:
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• Define parameters using the format Name=Value.
• Value may be a number, a previously defined parameter, a mathematical function, a parametric expression, or a character O
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, p p ,string.
• Use *GET or get functions to retrieve data from the ANSYS database
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database.
• ANSYS stores data in their actual form (numbers or strings), not in the form of parameter names. Part 1
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Chapter 14 – Short Topics
J. WorkshopsIN
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• Refer to your Workshop Supplement for instructions on:W14A Abbreviations O
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W14B 2-D Bracket Using Parameters
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Appendix A
ANSYS Native Geometry Creation and Best Modeling
PracticesPractices
Training Manual
Appendix – A. ANSYS Native Geometry Creation
OverviewIN
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• Importing geometry is convenient, but sometimes you may need to create it in ANSYS. Some possible reasons: O
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– You may need to build a parametric model — one defined in terms of variables for later use in design optimization or sensitivity studies.
– The geometry may not be available in a format ANSYS can read.– The Connection product you need may not be available on your
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The Connection product you need may not be available on your computer platform.
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• ANSYS has an extensive set of geometry creation tools, which we will discuss next.
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Appendix – A. ANSYS Native Geometry Creation
A. DefinitionsIN
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• Solid Modeling can be defined as the process of creating solid models. O
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• Definitions:– A solid model is defined by volumes, areas, lines,
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Volumes
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yp– Volumes are bounded by areas, areas by lines, and
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k i t li l
Areas
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keypoints < lines < areas < volumes – You cannot delete an entity if a higher-order entity
is attached to it.
Lines &Keypoints
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• Also, a model with just areas and below, such as a shell or 2-D plane model, is still considered a solid model in ANSYS terminology.
Keypoints
Lines
Areas
Volumes
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Keypoints
Training Manual
Appendix – A. ANSYS Native Geometry Creation
…DefinitionsIN
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• There are two approaches to creating a solid model:– Top-down O
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– Bottom-up
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which are then combined in some fashion to create the final shape.
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…DefinitionsIN
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• Bottom-up modeling starts with keypoints, from which you “build up” lines, areas, etc. O
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• You may choose whichever approach best suits the shape of the model, and also freely combine both methods.
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• We will now discuss each modeling approach in detail.
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
B. Top-Down ModelingIN
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• Top-down modeling starts with a definition of volumes (or areas), which are then combined in some fashion to create the final
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shape.– The volumes or areas that you initially define are called primitives.– Primitives are located and oriented with the help of the working plane.– The combinations used to produce the final shape are called Boolean
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Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Primitives are predefined geometric shapes such as circles, polygons, and spheres.
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• 3-D primitives include blocks, cylinders, prisms, spheres, and cones.
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• When you create a 2-D primitive, ANSYS defines an area, along with its underlying lines and keypoints.
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• When you create a 3-D primitive, ANSYS defines a volume, along with its underlying areas, lines and keypoints. O
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Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• You can create primitives by specifying their dimensions or by picking locations in the graphics window.
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– For example, to create a solid circle:• Main Menu > Preprocessor > Modeling > Create > Areas > Circle >
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Instructions
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By picking
Part 1Part 1Part 1Part 1Part 1Part 1Area Input:
1.) Pick the center and radius in graphics window...
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2.) Or enter in Picker Box
Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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– To create a block:• Main Menu > Preprocessor > Modeling > Create > Volumes >Block >
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By picking
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Volume Input:
1.) Pick the 2 diagonal corners and Part 1Part 1Part 1Part 1Part 1Part 1
Z-depth in graphics window...
2.) Or enter in Picker Box
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Boolean operations are computations involving combinations of geometric entities. ANSYS Boolean operations include add,
bt t i t t di id l d l
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subtract, intersect, divide, glue, and overlap.
• The “input” to Boolean operations can be any geometric entity, ranging from simple primitives to complicated volumes imported O
• All Boolean operations are available in the GUI under Main Menu Preprocessor > Modeling > Operate > Booleans
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• By default, input entities of a Boolean operation are deleted after the operation. O
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• Deleted entity numbers become “free” (i.e., they will be assigned to a new entity created, starting with the lowest available number).
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…Top-Down ModelingIN
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• Add– Combines two or more entities into one.
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Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Glue– Attaches two or more entities by creating a common boundary
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between them.– Useful when you want to maintain the distinction between entities
(such as for different materials).
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Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Overlap– Same as glue, except that the input entities overlap each other.
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Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Subtract– Removes the overlapping portion of one or more entities from a set of
“b ” titi
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“base” entities.– Useful for creating holes or trimming off portions of an entity.
ON
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Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Divide– Cuts an entity into two or more pieces that are still connected to each
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other by common boundaries.– The “cutting tool” may be the working plane, an area, a line, or even a
volume.– Useful for “slicing and dicing” a complicated volume into simpler O
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g g p pvolumes for brick meshing.
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Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Intersect– Keeps only the overlapping portion of two or more entities.
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– If there are more than two input entities, you have two choices: common intersection and pairwise intersection
• Common intersection finds the common overlapping region among all input entities.
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among all input entities.• Pairwise intersection finds the overlapping region for each pair of
entities and may produce more than one output entity.
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Part 1Part 1Part 1Part 1Part 1
Common Pairwise
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Co oIntersection Intersection
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Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Partition– Cuts two or more intersecting entities into multiple pieces that are still
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connected to each other by common boundaries.– Useful, for example, to find the intersection point of two lines and still
retain all four line segments, as shown below. (An intersection operation would return the common keypoint and delete both lines.) O
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Partition Part 1Part 1Part 1Part 1Part 1Part 1L5
L4
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Top-Down ModelingIN
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• Demo:– “Drill” a hole by subtracting a circle from a rectangle (or a cylinder
f bl k)
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from a block)– Create two overlapping entities, save db, and do the overlap
operation. Now resume db and add the entities. Note the difference between the two operations. (Glue is similar to overlap.) O
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– Interesting model:• block,-2,2, 0,2, -2,2• sphere,2.5,2.7 N
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• vinv,all ! intersection
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
C. WorkshopIN
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• Refer to your Workshop Supplement for instructions on:WAPP-A 1. Pillow Block O
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
D. Bottom-Up ModelingIN
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• Bottom-up modeling begins with a definition of keypoints, from which other entities are “built up.”
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• To build an L-shaped object, for example, you could start by defining the corner keypoints as shown below. You can then create the area by simply “connecting the dots” or by first O
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y p y g ydefining lines and then defining the area by lines.
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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• To define keypoints:– Main Menu > Preprocessor > Modeling > Create >
K i t
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Keypoints– Or use the K family of commands: K, KFILL,
KNODE, etc.
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• The only data needed to create a keypoint is the keypoint number and the coordinate location.
– Keypoint number defaults to the next available number. Part 1Part 1Part 1Part 1Part 1Part 1
– The coordinate location may be provided by simply picking locations on the working plane or by entering the X,Y,Z values.How are the X,Y,Z values interpreted? It depends on the active coordinate system.
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coordinate system.
Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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• There are many ways to create lines, as shown here.
If d fi l ANSYS ill t ti ll t
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• If you define areas or volumes, ANSYS will automatically generate any undefined lines, with the curvature determined by the active CS. O
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• Keypoints must be available in order to create lines.
Create > Lines > Arcs
Create > Lines > Lines
Create > Lines > Splines
Operate >Extrude N
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ArcsLines Splines Extrude
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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• Creating areas using bottom-up method requires keypoints or lines to be already defined.
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• If you define volumes, ANSYS will automatically generate any undefined areas and lines, with the curvature determined by the active CS. O
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Create > Areas > Arbitrary
Operate > Extrude
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y
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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• Creating volumes using bottom-up method requires keypoints or areas to be already defined.
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Arbitraryp
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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• Boolean operations are available for entities created by both top-down and bottom-up modeling approaches.
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• Besides Booleans, many other operations are available:– Extrude– Scale
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Scale– Move– Copy– Reflect N
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– Merge– Fillet
Part 1Part 1Part 1Part 1Part 1Part 1
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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Extrude
• To quickly create volumes from existing areas (or areas
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• To quickly create volumes from existing areas (or areas from lines, and lines from keypoints).
• If the area is meshed, you can extrude the elements along with the areas
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along with the areas.
• Four ways to extrude areas:– Along normal — creates volume by normal offset of areas
[VOFFST] NSYS
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[VOFFST] .– By XYZ offset — creates volume by a general x-y-z offset
[VEXT]. Allows tapered extrusion.– About axis — creates volume by revolving areas about an
axis (specified by two keypoints) [VROTAT]. Part 1Part 1Part 1Part 1Part 1Part 1
( p y yp ) [ ]– Along lines — creates volume by “dragging” areas along a
line or a set of contiguous lines [VDRAG].
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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• Scaling is typically needed when you want to convert the geometry to a different set of units, say from inches to millimeters.
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• To scale a model in ANSYS:– First save the database -- Toolbar >
SAVE_DB or SAVE command.Th M i M P O t
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– Then Main Menu > Preprocessor > Operate > Scale > Volumes (choose the highest-level entity available in the model)
• [Pick All] to pick all volumesTh d i d l f f
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• Then enter desired scale factors for RX, RY, RZ and set IMOVE to “Moved” instead of “Copied”
– Or use the VLSCALE command:l l ll 25 4 25 4 25 4 1
Part 1Part 1Part 1Part 1Part 1Part 1
• vlscale,all,,,25.4,25.4,25.4,,,1
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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Move
• To translate or rotate an entity by
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y yspecifying DX,DY,DZ offsets.
– DX,DY,DZ are interpreted in the active CS.– To translate an entity, make the active CS
Cartesian.To rotate an entity make the active CS
ON
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– To rotate an entity, make the active CS cylindrical or spherical.
– Or use the commands • VGEN, AGEN, LGEN, KGEN
Transfer from csys,0 to csys,11
Rotate -30°
NSYS
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• Another option is to transfer coordinatesto a different system.
– Transfer occurs from the active CS to a specified CS.
– This operation is useful when you need to
Part 1Part 1Part 1Part 1Part 1Part 1
p ymove and rotate an entity at the same time.
– Or use the commands • VTRAN, ATRAN, LTRAN, KTRAN
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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Copy
• To generate multiple copies of an
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• To generate multiple copies of an entity.
• Specify the number of copies (2 or greater) and the DX DY DZ offset for
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greater) and the DX,DY,DZ offset for each copy. DX,DY,DZ are interpreted in the active CS.
• Useful to create multiple holes ribs
Copy inlocalcylindricalCS N
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Useful to create multiple holes, ribs, protrusions, etc.
Part 1Part 1Part 1Part 1Part 1Part 1Create outer
areas byskinning
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skinning
Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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Reflect
T fl t titi b t l
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• To reflect entities about a plane.
• Specify the direction of reflection:– X for reflection about the YZ plane
ON
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X for reflection about the YZ plane– Y for XZ plane– Z for XY plane
All di ti i t t d i th
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All directions are interpreted in the active CS, which must be a Cartesian system. Part 1
Part 1Part 1Part 1Part 1Part 1
What is the direction of
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What is the direction of reflection in this case?
Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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Merge
• To attach two entities together by removing coincident keypoints
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• To attach two entities together by removing coincident keypoints.– Merging keypoints will automatically merge coincident higher-order entities, if
any.
• Usually required after a reflect copy or other operation that causes
ON
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Usually required after a reflect, copy, or other operation that causes coincident entities.
NSYS
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Merge or glueReflect
Part 1Part 1Part 1Part 1Part 1Part 1
Merge or gluerequired
Reflect
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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Fillet
• Line fillet requires two intersecting lines with a
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• Line fillet requires two intersecting lines with a common keypoint at the intersection.
– If the common keypoint does not exist, do a partition operation first.
– ANSYS does not update the underlying area (if any)
ON
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– ANSYS does not update the underlying area (if any), so you need to either add or subtract the fillet region.
• Area filleting is similar. Create NSYS
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gfillet
Part 1Part 1Part 1Part 1Part 1Part 1
Subtract frombase area
Createarea
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Training Manual
Appendix – A. ANSYS Native Geometry Creation
…Bottom-Up ModelingIN
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• Demo:– Resume r.db (if necessary)
Create two keypoints for the axis at (0 0) and (0 1) then extrude the area by
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– Create two keypoints for the axis, at (0,0) and (0,1), then extrude the area by revolving about the axis 60º
– Resume r.db– Make copies of the rib tangentially about the Y-axis:
C t l l li d i l CS t l b l i i ith THYZ 90
ON
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• Create a local cylindrical CS at global origin, with THYZ = -90• Generate 7 total copies (6 new ones) with DY=15
– Create the three outer “skin” areas using ASKIN,P– Resume r.db N
SYS N
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– Create a 0.5R fillet between the top and right lines. (Notice that the lines attached to the area have been modified. This is allowed in some cases.)
– Create the triangular fillet area by lines (AL,P), then subtract it from the main area. Part 1
Part 1Part 1Part 1Part 1Part 1
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Training Manual
Appendix – Workshops
E. WorkshopsIN
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• Refer to your Workshop Supplement for instructions on:WAPP-A 2. Connecting Rod – Bottom-Up Approach O
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WAPP-A 3. Connecting Rod – Importation/Clean-up
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Training Manual
Appendix – A. Best Modeling Practices
F. Best Modeling PracticesIN
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• This section is intended to give users advice on best modeling practices that will help the user avoid corrupt databases.
Put as much of your ANSYS input as you can into an input file Even simple
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– Put as much of your ANSYS input as you can into an input file. Even simple items such as material data and real constant data, so that your analysis is easier to debug (and even parameterize).
– Do not keep ‘deletes’ in your database. Use the input file edit a volume or a element size setting instead of deleting volumes or clearing a mesh
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element size setting instead of deleting volumes or clearing a mesh.– Perform element attributes (xATT) and Boolean operations BEFORE
meshing. (Absolutely no Booleans after meshing.)– Don't use NUMMRG,KP to pull together non-coincident keypoints.
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– Examine any imported geometry for slivers, voids, edges not meeting, or any other geometrical issue.
– Ideally, creating the geometry in ANSYS is best for meshing, however some users must import geometry. Users first option should be to use a connection product and import a SAT Parasolid etc file As a last resort
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connection product and import a SAT, Parasolid, etc file. As a last resort IGES files can also be imported. (Note: It has been some users experience that the time spent in repeatedly ‘cleaning-up’ IGES files, makes the purchase of a Connection Product more than worth the minimal cost.) Try all methods and see what works best for your case.
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Training Manual
Appendix – A. Best Modeling Practices
...Best Modeling PracticesIN
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• More Suggestions…– Do element attribute assignment on solid model geometry (xATT). Don’t
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use EMODIF or global settings (TYPE, MAT, REAL) unless you need to.– Make backup copies periodically (such as jobname.db1, jobname.db2, etc.).– Check the *.err file for all error messages and understand why warning
messages are printed. ON
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g p– Use the /EDGE command to display common lines between all adjacent
element faces. With the edge key on, an element plot displays only the element edges without coplanar share element edges. The NSEL,S,EXT command will select external nodes for the selected set of elements After N
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command will select external nodes for the selected set of elements. After plotting these nodes, the user should only see the nodes on the edges of the selected elements, any other nodes demonstrate problem locations.
– Do not perform any Booleans operations while you have any concatenated lines or areas in the model
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lines or areas in the model.– Don’t divide a line by a meshed line – always clear the mesh before
performing Booleans.– Delete any FE-based elements (ie: contact, pretension, surface effect
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elements) before clearing a mesh.
Training Manual
Appendix – A. Best Modeling Practices
...Best Modeling Practices IN
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• More Suggestions…– Import all geometry at one time - ie.: don’t import, mesh, import. O
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– Don't subtract or overlap coincident or tangent geometry. For example: block,,1,,1,,1 block,,1,,1,,1 vsbv,1,2.
– Minimize use of hardpoints.– Minimize use of dragging and skinning
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Minimize use of dragging and skinning.– Minimize use of cylindrical and spherical coordinate systems to create
geometry bottom-up from keypoints.– Where surface or rotation are required, for cylinders, spheres, torus, etc.,
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extrude the wire around an axis and then trim the surface as necessary. This will eliminate the COONS patch problem by providing more precise NURBS surfaces from the extrusion process.
– Use COONS patches generated on non-cartesian coordinate systems only Part 1Part 1Part 1Part 1Part 1Part 1
as the last resort. When these are used and the results are needed for Boolean operations use these surfaces or their associated volumes last in your operations.
– If using multiple load step files (LSWRITE), do this last since .s00 files only
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g p p ( ) ycontain loadings for FE data.
Training Manual
Appendix – A. Best Modeling Practices
...Best Modeling PracticesIN
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• More Suggestions…– Start with very simple models, using a few elements of the element type
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desired and start with simple material properties before upgrading to, say, a hyperelastic material model.
– Take a Verification Manual problem with a known solution and then start tweaking that towards what you are trying to do. O
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– Use the same numbering even though it is redundant – such as TYPE 1, REAL 1, MAT 1 for one part, and TYPE 2, REAL 2, MAT 2, for another part. This makes attribute assignment easy to keep track of.
– Start with a working database and record all Boolean operations in a text NSYS
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Start with a working database and record all Boolean operations in a text file. If something goes wrong, you can just edit the file and your db will be fine.
– If the database is corrupt, you can resume the database and archive the file with the CDWRITE as a last resort
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with the CDWRITE as a last resort.– Take the time before modeling to plan your approach - this will save you a