Finite Element Primer for Engineers: Part 3adfisher/7962-07/Presentations/FEA-Part3.pdf · • Heat transfer analysis »Temperature ... Finite element analysis works on the premise

Finite Element Primer for Engineers: Part 3Mike Barton & S. D. Rajan

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©, 2000, Barton & Rajan 2

Contents

••• Introduction to the Finite Element Method (FEM)Introduction to the Finite Element Method (FEM)Introduction to the Finite Element Method (FEM)

••• Steps in Using the FEM (an Example from Solid Steps in Using the FEM (an Example from Solid Steps in Using the FEM (an Example from Solid Mechanics)Mechanics)Mechanics)

• Examples

••• Commercial FEM SoftwareCommercial FEM SoftwareCommercial FEM Software

••• Competing TechnologiesCompeting TechnologiesCompeting Technologies

••• Future TrendsFuture TrendsFuture Trends

••• Internet ResourcesInternet ResourcesInternet Resources

••• ReferencesReferencesReferences


Information Available from Various Types of FEM Analysis

• Static analysis» Deflection » Stresses » Strains » Forces » Energies

• Dynamic analysis» Frequencies » Deflection (mode

shape) » Stresses » Strains » Forces » Energies

• Heat transfer analysis»Temperature » Heat fluxes » Thermal gradients » Heat flow from convection faces

• Fluid analysis» Pressures » Gas temperatures » Convection coefficients » Velocities


Example FEM Application Areas

• Automotive industry» Static analyses » Modal analyses» Transient dynamics » Heat transfer » Mechanisms » Fracture mechanics » Metal forming » Crashworthiness

• Aerospace industry» Static analyses » Modal analyses» Aerodynamics » Transient dynamics » Heat transfer » Fracture mechanics » Creep and plasticity analyses » Composite materials » Aeroelasticity» Metal forming » Crashworthiness

• Architectural» Soil mechanics» Rock mechanics» Hydraulics» Fracture mechanics» Hydroelasticity


Variety of FEM Solutions is Wide and Growing Wider

• The FEM has been applied to a richly diverse array of scientificand technological problems.

• The next few slides present some examples of the FEM applied to a variety of real-world design and analysis problems.


• This example shows an intravenous pump modeled using hexahedral elements.


Car tires require sophisticated analysis because of their complex geometry, large deformations, nonlinear material behavior, and varying contact conditions. Brick elements are used to represent the tread and steel bead, while shell elements are used in the wall area. Membrane elements are used to represent the tire cords.


This forging example is a simulation of a bulk forming process with multiple stages. This axisymmetric analysis begins with a cylinder of metal meshed very simply.


A 3-D finite element model of an instrumented canine cervical spine.The model consisted of four vertebrae (C3-C6), a titanium alloy plate, and two screws attached to the back of two vertebrae (C4-C5).


Finite element analysis works on the premise that a complex structure like the helicopter shown here can be simulated on a computer screen so that the helicopter's physical properties can be studied to determine how well the design will perform under real-world conditions. The computer models permit the design team to examine a wide range of options and to detect design flaws long before the prototype stage.


This guitar features two strips of graphite running the length of the neck. This FEM model was used to study how much the neck moved when string forces were applied and moisture contentchanged.

Using the FEM calculations, designers could try different reinforcement scenarios to increase neck stability.


The boat’s hull consists of a thick core material sandwiched between two thinner layers of plys oriented in different directions. The initial analysis work focused on maximizing the hull's overall stiffness by examining different core-material densities and varying the ply thickness and orientations.


Dynamic analysis of a tuning fork, to find it's first eight modes of vibration.

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Contents



••• ExamplesExamplesExamples

• Commercial FEM Software






Commercially Available FEM Software Suites

• Here we present a survey of some of the better-known integrated FEM software packages. These integrated systems allow users to perform all facets of FEM analysis, including modeling, meshing, solution and post-processing.

• The Internet provides a vast new resource for individuals interested in the FEM. See the Reference section of this paper for interesting FEM links to start your Internet research.

• In addition to the integrated FEM packages listed below, many vendors offer dedicated software for solid modeling, mesh generation, FE equation generation and solution, and post-processing.


Commercially Available FEM Software Suites (cont.)(partial list)

Software Package Introduced CommentsABAQUS 1978 General purpose, with special emphasis on advanced linear and nonlinear structures and heat transfer applications.ADINA 7.0 1975 Optimized for structural and heat transfer applications. Limited element library. Extensive material model library.

ALGOR 1984 First FEM package available for PC use. ANSYS/LS-DYNA N/A For solving highly nonlinear structural dynamics problems (impact, large deformation, nonlinear materials, etc.)

ANSYS/MECHANICAL 1970 Probably the best-known and most widely-used FEM software. Complete structures/thermal/acoustics modleing.ANSYS/Multiphysics N/A Coupled-field, multidisciplinary FEM program.

ELFEN N/A Includes linear and nonlinear buckling, modal analysis, transient heat transfer analysis, impact and fragmentation.GENESIS N/A Fully integrated finite element analysis and numerical optimization software for structural analysis.

LUSAS N/A Includes automatic meshing, advanced non-linear analysis, and composites analysis.MARC 6.2 1970 3D automated contact analysis capabilities suited for studying tough manufacturing problems, (metal forming/ etc.)MSC/FEA 1971 MSC participated in the 1965 development of NASA's public-domain FEM code, NASTRAN.

MSC/NASTRAN for Windows N/A Handles stress, vibration, dynamic, nonlinear, heat transfer, and fluid flow analyses of mechanical components.NISA/DISPLAY 1973 A family of general purpose FEM programs for PCs and workstations. Modular design.

PAM 1973 FEM software optimized to study restraint systems (PAM-SAFE), impacts (PAM-SHOCK) and metal forming.SAMCEF 1965 One of the oldest FEM codes available. A powerful FEM package for structural and heat transfer analysis.

STARDYNE 1967 The world's first commercially available Finite Element Analysis software.STARS N/A Integrated, general-purpose, finite element software. Developed by NASA.


Contents





• Competing Technologies





Technologies That Compete With the FEM

• Other numerical solution methods:– Finite differences

» Approximates the derivatives in the differential equation usingdifference equations.» Useful for solving heat transfer and fluid mechanics problems.» Works well for two-dimensional regions with boundaries parallel to the coordinate axes.» Cumbersome when regions have curved boundaries.

– Weighted residual methods (not confined to a small subdomain):» Collocation» Subdomain» Least squares*» Galerkin’s method*

– Variational Methods* (not confined to a small subdomain)

* Denotes a method that has been used to formulate finite element solutions.


Technologies that Compete With the FEM (cont.)

• Prototype Testing» Reliable. Well-understood.» Trusted by regulatory agencies (FAA, DOT, etc.)» Results are essential for calibration of simulation software.» Results are essential to verify modeled results from simulation.» Non destructive testing (NDT) is lowering costs of testing in general.» Expensive, compared to simulation.» Time consuming.» Development programs that rely too much on testing are increasingly less competitive in today’s market.» Faster product development schedules are pressuring the quality of development test efforts.» Data integrity is more difficult to maintain, compared to simulation.


Contents






• Future Trends




Future Trends in the FEM and Simulation

• The FEM in particular, and simulation in general, are becoming integrated with the entire product development process (rather than just another task in the product development process):

– FEM cannot become the bottleneck.

• A broader range of people are using the FEM:– Not just hard-core analysts.

• Increased data sharing between analysis data sources (CAD, testing, FEM software, ERM software.)

• FEM software is becoming easier to use:– Improved GUIs, automeshers.– Increased use of sophisticated shellscripts and “wizards.”


Future Trends in the FEM and Simulation (cont.)

• Enhanced multiphysics capabilities are coming:– Coupling between numerous physical phenomena.

» Ex: Fluid-structural interaction is the most common example.» Ex: Semiconductor circuits, EMI and thermal buildup vary with current densities.

• Improved life predictors, improved service estimations.

• Increasing use of non-deterministic analysis and design methods:– Statistical modeling of material properties, tolerances, and anticipated loads.– Sensitivity analyses.

• Faster and more powerful computer hardware. Massively parallel processing.

•Decreasing reliance on testing.

• FEM and simulation software available via Internet subscription.


Contents







• Internet Resources



Selected FEM Resources on the Internet

• The internet offers virtually unlimited resources to persons interested in the FEM.

• The following links are a small sample of FEM sites on the Internet which the author has found useful. Thousands more (at least!) are readily available.

• Most commercial FEM developers have extensive presence on the Internet, with web pages that include company histories, descriptions of software products, and example FEM solutions.

• Other good FEM resources on the web originate with academia, government, and discussion and user groups.


Selected FEM Resources on the Internet (cont.)

• http://www.engineeringzones.com - A website created to educate people in the latest engineering technologies, manufacturing techniques and software tools. ExellentFEM links, including links to all commercial providers of FEM software.

• http://www.comco.com/feaworld/feaworld.html - Extensive FEM links, categorized by analysis type (mechanical, fluids, electromagnetic, etc.)

• http://femur.wpi.edu - Extensive collection of elementary and advanced material relating to the FEM.

• http://www.engr.usask.ca/%7Emacphed/finite/fe_resources/fe_resources.html -Lists many public domain and shareware programs.

• http://sog1.me.qub.ac.uk/dermot/ferg/ferg.html#Finite - Home page of the the Finite Element Research Group at The Queen's University of Belfast. Excellent set of FEM links.

• http://www.tenlinks.com/cae/ - Hundreds of links to useful and interesting CAE cited, including FEM, CAE, free software, and career information.

•http://www.geocities.com/SiliconValley/5978/fea.html - Extensive FEM links.

• http://www.nafems.org/ - National Agency for Finite Element Methods and Standards (NAFEMS).


Contents








• References


References

Cashman, J., 2000. “Future of Engineering Simulation,” ANSYS Solutions, Vol. 2, No. 1, pp. 3-4.

Chandrupatla, T. R. and Ashok D. Belegundu, 1997. Introduction to Finite Elements in Engineering, Prentice Hall, Upper Saddle River, New Jersey.

Kardestuncer, H., 1987. Finite Element Handbook, McGraw-Hill, New York.

Krouse, J., 2000. “Physical Testing Gets a Bum Rap,” ANSYS Solutions, Vol. 2, No. 2, p. 2.

Lentz, J., 1994. Finite Element Analysis Cross Training, unpublished lecture notes, Honeywell Engines and Systems, Phoenix, Az.

Nikishkov, G.V., 1998. Introduction to the Finite Element Method, unpublished lecture notes, University of Arizona, Tucson, Az.

Rajan, S.D., 1998. Finite Elements for Engineers, unpublished lecture notes, Arizona State University, Tempe, Az.

Segerlind, L. J., 1984. Applied Finite Element Analysis, John Wiley and Sons, New York.

Finite Element Primer for Engineers: Part 3adfisher/7962-07/Presentations/FEA-Part3.pdf · • Heat transfer analysis »Temperature ... Finite element analysis works on the premise

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