FEA in Solid Edge and FEMAP - Siemens PLM Community... · FEA in Solid Edge and FEMAP ... NX Nastran through the latest release of NX Nastran 8.1 ... linear static Finite Element

FEA in Solid Edgeand FEMAPMark Sherman

Realize innovation.Restricted © Siemens AG 2016

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Restricted © Siemens AG 2016

XX.XX.20XXPage 2 Siemens PLM Software

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FEMAP

Continuous development with the same core team!

Since 1985 there have been more than 35 releases of FEMAP with only one major architecture change (DOS to Windows)

FEMAP Development Team is all engineers turned programmers – FEA By Engineers for Engineers

Product development has been driven by FEA Analyst input



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What you will learn

Come learn how to apply finite element analysis techniques to your models using Solid Edge’s built-in simulation as well as Femap, our CAD-independent, advanced simulation program. Digital simulation allows you to predict and improve the performance and reliability of your models, reduce time-consuming and costly physical prototyping, evaluate different designs and materials, and optimize your designs. This session will show you the benefit of integrating simulation in your design work, with emphasis on interpreting the results of an analysis to effectively influence product design.



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Objectives of

introducing 3D CAD?



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Objectives introducing 3D CAD – Top 20

Source: Survey by Japan society for the promotion of science

200 companies responded in 2001• General machinery• Electric• Transportation• Precision machinery• Other



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Objectives introducing 3D CAD

1 Shorten the development cycle2 Eliminate the inconsistency in the design3 Improve product quality4 Reduce the number of prototypes5 Reduce the number of development steps6 Leverage the 3D design data for analysis… ……12 Expand the analysis by design engineers… ……16 Increase the types of analysis




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Expand the analysis by design engineers

CAE by designer

20%

CAE by specialist

80%

1998

CAE by designer

30%

CAE by specialist

70%

2001


Analysis by design engineers is increasing



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Simulation driven design

A Solution for Challenges in manufactures

TimeDevelopmentDesign Validation

CostMaterials PrototypesWarranty

Quality Performance

Innovation



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Why Simulation?

Optimize design• Reduce weight• Reduce materials• Promote innovation

C

C

Q

Failure analysis• Improve performance• Improve reliability• Reduce recalls CT

Q

Q

Q

T

C

Q

Time

Cost

Quality

Virtual testing• Reduce prototypes• Reduce physical tests• Speed time to market

T

T

T

C

C



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A Brief History of FEA and FEM

The concept of a “Finite Element” was introduced by Prof. R.W. Clough of UC Berkeley in 1960 at an ASCE Conference.

NASTRAN (NASA STRuctural ANalysis) was developed for NASA by a consortium of several companies for the analysis of the Saturn V rocket.

Siemens PLM Software acquired MSC.Nastran source code in 2003 and has greatly improved the performance and capabilities of NX Nastran through the latest release of NX Nastran 8.1

Finite Element Modelers(Pre/Post Processors), the tools used to generate Finite Element meshes and view results, were first commercialized in the 1970s.

Siemens PLM Software began the first commercial offering of FEM software with the introduction of SDRC SuperTab in the 1970’s.

Siemens continues to support the analysis community with Femap and NX CAE pre/post-processors.



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The Solution

Consider a single degree of freedom system – a simple spring:

Apply the following conditions to generate a system of simultaneous equations where displacements are the unknowns:

Equilibrium of forces and moments

Strain- displacement relations

Stress-strain relations

K: spring stiffnessP: applied load

u: displacement

K u = P (static analysis) ?



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Solution for Multiple DOFs

Any real structure can be modeled as a collection of elements connected at nodes

With many elements and nodal dof’s, a matrix approach to the solution is adopted

All element matrices are assembled into a global stiffness matrix

Kgg =

k11 k12

k21 k22ka =

Element stiffness matrix ka kb

1 2 3

ka11 ka12

ka21 ka22 + kb22 kb23

kb32 kb33



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Modeling of Real Structures

• The behavior of the real structure is obtained by considering the collective behavior of the discrete elements.

• The user is responsible for the subdivision or discretization of real-world structures.

• Element choice has significant influence on the behavior• A graphic preprocessor such as FEMAP/SE Simulation is the key tool for

generating a model that accurately simulates real world structures

Kgg =

ka -ka

-ka ka + kb -kb

-kb kb

• Contributions from all other elements

n x n



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Small Example



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Small Example

K u = P (static analysis)

u = K-1 P



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Small Example in FEMAP



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Linear Static Analysis

• 90%+ of all FEA projects• 100% Linear – if you double the loads,

you get double the response• Material stays in the elastic range –

return to original shape• Small Deformation

Maximum Displacement much smaller than characteristic dimensions of the part being studied, i.e. displacement much less than the thickness of the part

• Loads are applied slow and gradually, i.e. not Dynamic or Shock Loading



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Linear Static Analysis

• What can you expect to learn from a linear static Finite Element Analysis

• Displacements

• Load Paths

• Stress*



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Linear Analysis is small displacement, small angle theory

Must use nonlinear analysis if the displacement changes the stiffness or loads

Pressure loads on flat surfaces, have no membrane component unless nonlinear large displacement solution performed.(load carried by bending stiffness only)

Linear contact is a misnomer, contact condition is iterative solution, but no other nonlinear effects are considered.

Mesh density required is a function of the desired answers

Must have enough nodes so model can deform smoothly like the real structure.

In general, accurate stresses require more elements than accurate displacements.

Goal is for a small stress gradient across any individual element

Normal modes should always be run before any dynamic solution

Confirm model behavior, stiffness and mass properties are correct

Important Guidelines



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Normal Modes

• Function of stiffness and mass, both must defined correctly

• Understand fundamental vibration characteristics; shapes and frequencies

• All dynamic response is a linear combination of the normal modes of a structure

• Run Normal Modes to make sure your model is correct



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Nonlinear Statics

• Material nonlinear effects:• Material yielding• Nonlinear stress/strain relationship

• Large displacement effects:• displacement changes the stiffness; thin walled

pressure vessel• displacement changes the load direction; pressure,

beam column

• Contact



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Design Optimization – Example – Idler Pulley

• Idler Pulley with following inputs to optimization• Material is Aluminum 1060 (Yield Stress of 4000

psi)• Torque Load of 1000 in-lbf• Inner Cylinder/Geometry Fully Constrained• Initial Solve indicates Max Von Mises Stress of

897 psi• Optimization Inputs

• Initial Solution of 897 psi for Max Von Mises• Objective – Minimize Mass (Initial Mass is

7.281 lbm)• Design Limit – Von Mises Stress Less than

1333 psi (ie. FOS of 3)• Design Variables using Angle and Height

Dimensions• Max Iterations - 20



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Design Optimization – Example – Continued

• UI Inputs



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Design Optimization – Example – Final Solution

• Final Solution after 10 iterations• Minimized Mass to 5.715 lbm (

reduction of 1.566 lbm from model)• Max Von Mises Stress of 1285 psi

(below 1333 psi ) with FOS of 3• Original angle dimension of 40

degrees now 87.71 degrees• Original Height of cutout of 3 in now

3.9 in



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Frequency Response

• Response of structure vs frequency

• Load is function of frequency

• Examples:• Washing Machine• Generator in Power Plant• Automobile Tire out of balance



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Transient Response

• Response of structure is function of time.• Load changes vs time

• Examples:• Vehicle on road with potholes• Building subjected to earthquake• Impact loading; drop testing• Rocket wind and thrust load



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Nonlinear Transient Response

• Loading and structural response a function of time

• Large displacement effects considered

• Material nonlinear effects considered

• Implicit and Explicit Solvers

• Examples:• Impact/crash where material

stress exceeds yield

Model from - National Crash Analysis Centerhttp://www.ncac.gwu.edu/vml/models.html



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Solution from Siemens

Daily work

Advanced Modeling &

Analysis

Dynamic Response

Nonlinear

Ana

lysi

s ex

pert

ise

SOLID EDGE SIMULATION• Linear Static

• Normal Modes• Heat Transfer

• Geometric Nonlinear

Femap with NX Nastran

Flow-Thermal

Design Optimization



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Advanced Modeling

• “Beam Like” structures modeled as two node beam elements

• Thin structures (1 to 10) modeled as shells

• Rigid components modeled as Lumped Masses

• Model Size now smaller, Advanced Analyses now possible



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Advanced Modeling

• Mid-Surface Extraction• Model thin-shell structures with plate

elements• Reduces FEA model size significantly• Quickly change thickness value to

optimize design



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Solid Edge Simulation

• Shell & Solid tetrahedral elements• Local mesh size control • Based on Femap meshing technology

• Geometry based constraints & loads• Handles help define direction and orientation• Quick Bar input options

• Fringe, color plots and contours• Displacement, animation and mode shapes• Report generation

• Remove unnecessary features• Change geometry shape quickly & easily• Mesh automatic update

• Industry standard solver - NX Nastran• Statics, normal modes and buckling analysis• Automatic element quality checks

Automatic Finite Element Model Creation

Full Boundary

Condition Support

Comprehensive

Post Processing

Synchronous Technology

with model associativity

Powerful Analysis

Capability



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Customer SuccessGEA Farm Technologies

“FEA allows us to save money during the design process, and save iterations at the prototype step. We can reduce four to five physical prototypes down to just one, shaving the design cycle by months.”Alexander LapriseEngineerGEA Farm Technologies



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Customer SuccessZumex

“The use of FEA has become a great time-saving device. During physical machine testing, the breakages that

occur coincide exactly as predicted by the FEA analysis.”

Eloy HerreroMarketing

ManagerZumex



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Example – An electric drive system

Objective : • Verify the bracket’s strength so that the maximum deformation is within the

design criteria.• Design the better products reducing vibration level during operation, so that

the noise level can be kept lower than the competitors eventually.

Solution : • Predict the maximum deformation of the

bracket by applying linear statics analysis.• Predict the product’s dynamic characteristics

by using the frequency response analysis.



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CAD assembly of an electric drive system

Bracket

Frame

Motor



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Supporting structures



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Connections defined between parts

Glued connection



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Connections defined between parts

Glued connection



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Constraints

Fixed surfaces



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Bearing load



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Mesh for FEA



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Static analysis - Result

Result < CriteriaOk!



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Linear Statics - Stresses

To accurately recover stresses in shell and solid elements, the mesh must be very dense in areas of high stress gradients

Stress Changing TooFast Across One Element



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Stresses from the Web



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To accurately recover stresses in shell and solid elements, the mesh must be very dense in areas of high stress gradients

Stress Changing Less Acrossan Element – More Accurate



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Keeping Model Size “Reasonable”Increase the Mesh Density where you need it, decrease it where you don’t



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Guidelines for Good Stress Interpretation - Singularities



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Guidelines for Linear Static Analysis - Stresses

• Remember the limitations of “Linear” analysis

• Increase Mesh Density in High Stress Regions

• Ignore Stress Answers at Singularities

• Zero Radius Fillets

• Inside Corners

• Loaded and Constrained Nodes



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Normal Modes - Result

No Mode Frequency Mode Shape

1 206 Hz

2 265 Hz

3 317 Hz



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Normal Modes

No Mode Frequency Mode Shape

4 411 Hz

5 505 Hz

6 527 Hz



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Results summary

Category Item to check Results GO/NG

Strength • Deformation• Stress < Design criteria GO

Normal modes • Modal frequencies

≠ Excitation frequencies(3000 RPM = 50 Hz) GO



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Considerations

Source input = Rotating motor = 3000 RPM = 50 HzResonance frequencies to avoid = n*RPM

= 50 Hz, 100 Hz, 150 Hz, 200 Hz, …..

Need to carefully investigate the vibration level around Mode 1 and 5 as these are close to the above input frequencies.• Mode 1 = 206 Hz• Mode 5 = 505 Hz

Response Analysis

Vibration level?



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Switch to the dedicated CAE software

In Solid Edge, you can save your simulation model as the Femap file.• Direct file translation including the results• Open the file in the Femap for the further analysis



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Frequency Response

Excitation = Force= Motor mass x Gravity= 2 [kg] x 9.8 [mm^2/s]= 19.6 [N]



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Frequency Response



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Flow Analysis

Air volume

Flow velocity

FanVent



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Advanced Dynamics Examples

Frequency response analysis is used to compute structural response to steady-state oscillatoryexcitation. Examples of oscillatory excitation include rotating machinery, unbalanced tires,and helicopter blades. In frequency response analysis the excitation is explicitly defined inthe frequency domain. Excitations can be in the form of applied forces and enforced motions(displacements, velocities, or accelerations).

Request responses between 50 and 80 Hz, every 0.05 Hz



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Advanced Dynamics Examples



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Two Takeaways

• Run Normal Modes on your Design to make sure everything is set up correctly, especially for assemblies

• Always be skeptical of a Stress Plot

FEA in Solid Edge and FEMAP - Siemens PLM Community... · FEA in Solid Edge and FEMAP ... NX Nastran through the latest release of NX Nastran 8.1 ... linear static Finite Element

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