What should CAE engineers now

What Should CAE Engineers Know and What TheyDo Not Need to Know?15. Nov. 2007

Automotive and Power Train EngineeringProf. Dr.-Ing. M. Meywerk (Automotive Engineering)

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What Should CAE Engineers Knowand What They Do Not Need to Know

Univ.-Prof. Dr.-Ing. Martin MeywerkDepartment of Automotive and Power Train Engineering

Helmut-Schmidt-UniversityUniversity of the Federal Armed Forces, Hamburg



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Introduction

What is the background?Giving lectures both for engineers in industry and students (topic:

CAE methods in automotive engineering). The experiences are the following:

the „pupils“ learn very quick the functionality of buttons and how to produce coloured pictures

the „pupils“ do not want to analyse or interpret the resultsBut: It is very important to anaylse results from CAE-software from

a physical point of view



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Workflow for CAE engineers

Boss: This is our new part in the suspension; are you ableto calculate the durability?

CAE engineer: Yes, of courseBoss: By tomorrow?CAE engineer: By next week!?Boss: ...

Now the work starts for the CAE engineer.



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Modellingphysical → geometrical → mathematical

Simulating (software)

Analysing the results



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Physical ModellingWhich physical phenomena are involved in the problem?⇒ principal physical equations

Which phenomena could be neglected?⇒ assumptions

Simple estimations or experimentsconcerning the assumption have to be done⇒ Final set of equations

possible

chan

geof

A lot of knowledge of physical phenomena is necessary.



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Geometrical modelling

1. CAD-data Clean upunique (not double defined)

anywhere (no holes)

2. Physically motivated modification (strong link to physical modelling)



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Geometrical modellingKleine Bohrung

Kleine Sicke

little hole

little bead



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Physically motivated modifications / simplifications

- a lot of experience is necessary for simplifacation of geometry- anticipation of the solution- simplification is necessary

statics (stress)--oheat conduction+++Modal analysis (eigenvalues)++o

disciplineradiiholesbeads

small

+ can be simplifiedo with restrictions: can be simplified- should not be simplified



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Physically motivated modifications / simplificationsa)

a

b

b/20

a/4

2b/3

c)

b/109x....

4b/5

b)b/20

4b/5b/5

x

b/10

b/5

b/10

b/5

b/10

b/5

d) e)

f)

9x....

modifications dependadditionally to discipline on: Number, shape and location



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Mathematical Modelling

Correct choice of: • solver for ODE • discretization method for PDE• parameter of the solving algorithm

- knowledge of the algorithms is necessary



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Simulating (software)

– knowledge of the most capabilities of the software– knowledge of all relevant input parameters



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Analysing the results

- plausibility of the results- simple estimations- comparison with known facts- conservation of mass, momentum, energyIt is the responsibility of the CAE engineer to check the results!

- basic principles has to be known- simple estimation formulas have to be applied

(known by heart or by book)- basic physical parameters has to be known by heart



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Lack of knowledge

- properties of tensors (of second order)- how to apply simple estimation formulas- broad knowledge of physics- plausibility checks



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Summary

What should CAE Engineers know

• a lot of physics, some numerical mathematics, little CAD facts,how to estimate, how to anticipate, and how to interprete results

and what they do not need to know?

• script languages for pre- or post processing or workflow definition,programming languages e.g. C#, customizing of software



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Demands on knowledge:

basic: bstandard: shigh: h

Classification of CAE engineerCAD engineer : CADCAE standard user : CAECAE specialist (developer) : Spec.

Demands



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Matrix: Demands vs. Classification

Should not be done

b

Crash

s

Spec.

CAE

CAD

hshs hbb

MBSStatic/FEM



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Example: MBS (some keywords)basic: kinematics and kinetics of rigid bodies in three dimensions,

solver for ODE, angles for orientation of rigid bodies(e.g. Euler), simple 1D-force-deflection-laws, …

standard: broad survey of solvers for ODE (incl. one-step, multi-step,implicit, explicit), stiff ODE, survey of orientation descriptionsfor rigid bodies, simple tensor calculus, general3D force / momentum-deflection/rotation law, flexible bodies (Craig Bampton), …

spec.: DAE solver, index 3 systems, floating frame of referenceformulation for flexible bodies in MBS, …

Examples, no complete list!



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Example: Continuum Mechanicsbasic: linear material laws, lin. FEA, tensors; limits of the

simplified, linear modelling, …

standard: nonlinear material laws, elasto-plastic, composites,phaenomenological laws, higher order FE, locking effects, …

spec.: alternative discretization method (MLS, Trefftz), adaptivemeshing, compatibility, …




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Example: Crashbasic: Crash on a low level should not be applied!

standard: nonlinear material laws, elasto-plastic, composites,phaenomenological material laws, foams, reduced/full/selectiveintegration, hourglass modes/control, mass scaling, contactalgorithm, parts of standard MBS, tensors, invariants, time stepcontrol, mass scaling, penetration removal, airbag andrestraint modelling, dummy models, basics of nonlineardynamics, ….

spec.: alternative discretization method (MLS, Trefftz, …), adaptivemeshing, ….


Education

What should CAE engineers now