What should CAE engineers now.

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

What Should CAE Engineers Know
and What They Do Not Need to Know
Univ.-Prof. Dr.-Ing. Martin Meywerk
Department of Automotive and Power Train Engineering
Helmut-Schmidt-University
University of the Federal Armed Forces, Hamburg

15. Nov. 2007

What Should CAE Engineers Know and What They
Do Not Need to Know?

1/14


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 results
But: It is very important to anaylse results from CAE-software from
a physical point of view

15. Nov. 2007


2/14


Workflow for CAE engineers
Boss:

This is our new part in the suspension; are you able
to calculate the durability?

CAE engineer: Yes, of course
Boss:

By tomorrow?

CAE engineer: By next week!?
Boss:

...

Now the work starts for the CAE engineer.

15. Nov. 2007


3/14


Modelling
physical → geometrical → mathematical
Simulating (software)
Analysing the results

15. Nov. 2007


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Physical Modelling
Which physical phenomena are involved in the problem?
change of

⇒ principal physical equations
Which phenomena could be neglected?
⇒ assumptions
Simple estimations or experiments
concerning the assumption have to be done

possible

⇒ Final set of equations
A lot of knowledge of physical phenomena is necessary.

15. Nov. 2007


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Geometrical modelling
1. CAD-data Clean up
unique (not double defined)
anywhere (no holes)
2. Physically motivated modification (strong link to physical modelling)

15. Nov. 2007


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Geometrical modelling
little Bohrung
Kleinehole

little bead
Kleine Sicke

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Physically motivated modifications / simplifications
small
beads

holes

radii

discipline

o

+

+

Modal analysis (eigenvalues)

+

+

+

heat conduction

o

-

-

statics (stress)

+ can be simplified
o with restrictions: can be simplified
- should not be simplified
- a lot of experience is necessary for simplifacation of geometry
- anticipation of the solution
- simplification is necessary
15. Nov. 2007


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Physically motivated modifications / simplifications
a)

c)

b)

b

a/4

a
2b/3

9x
....

b/20

b/5
4b/5

b/10

4b/5

b/20

9x
....

modifications depend
additionally to discipline on:

x

Number, shape and location
b/10

d)

e)
b/10
b/5
b/5

b/10

f)

b/5

15. Nov. 2007


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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

15. Nov. 2007


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Simulating (software)

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

15. Nov. 2007


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Analysing the results
-

plausibility of the results

-

simple estimations

-

comparison with known facts

-

conservation of mass, momentum, energy

It 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

15. Nov. 2007


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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

15. Nov. 2007


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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

15. Nov. 2007


14/14


Demands on knowledge:
basic:
standard:

s

high:

Demands

b
h

Classification of CAE engineer
CAD engineer

: CAD

CAE standard user

: CAE

CAE specialist (developer) : Spec.

15. Nov. 2007


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Matrix: Demands vs. Classification
Static/FEM
b
CAD

s

MBS
h

b

Crash
s

h

b

s

h

Should not be done

CAE
Spec.

15. Nov. 2007


16/14


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 descriptions
for rigid bodies, simple tensor calculus, general
3D force / momentum-deflection/rotation law,
flexible bodies (Craig Bampton), …

spec.:

DAE solver, index 3 systems, floating frame of reference
formulation for flexible bodies in MBS, …
Examples, no complete list!

15. Nov. 2007


17/14


Example: Continuum Mechanics
basic:

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), adaptive
meshing, compatibility, …

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Example: Crash
basic:

Crash on a low level should not be applied!

standard:

nonlinear material laws, elasto-plastic, composites,
phaenomenological material laws, foams, reduced/full/selective
integration, hourglass modes/control, mass scaling, contact
algorithm, parts of standard MBS, tensors, invariants, time step
control, mass scaling, penetration removal, airbag and
restraint modelling, dummy models, basics of nonlinear
dynamics, ….

spec.:

alternative discretization method (MLS, Trefftz, …), adaptive
meshing, ….

15. Nov. 2007


19/14

What should CAE engineers now.

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