2011 European HyperWorks Technology Conference · 2011 European HyperWorks Technology Conference Model updating considering damping effects Charline Bonfils, EDAG GmbH & Co. KGaA

2011 European HyperWorks Technology Conference

Model updating considering damping effects

Charline Bonfils, EDAG GmbH & Co. KGaA

Antoine Guellec, AUDI AG

Fahrzeugphysik


© Copyright 2010 EDAG GmbH & Co. KGaA. Alle Rechte vorbehalten. Charline Bonfils EDAG, Antoine Guellec AUDI AG, 06-09/11/2011


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Issue

Low-frequency NVH analysis

Ways to represent damping in FEM

modal damping

viscous damping

structural damping

Damping modelling generally not accurate enough

FEM validation using experimental data

Interest of optimization: identify model differences

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Contents: The successive steps of validation

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Comparison of the models

Test vs. FEM

Experiment FEM Simulation

Eigen mode comparison

Curve comparison

Optimization with Optistruct

Objective Definition & Design Variables

Sensitivity Analysis and Results


© Copyright 2010 EDAG GmbH & Co. KGaA. Alle Rechte vorbehalten. Charline Bonfils EDAG, Antoine Guellec AUDI AG, 06-09/11/2011 Folie 4 von 17

Step 1: Comparison of the models (FE vs. Test)

Total mass TB

Mass distribution

Step 2: Eigen modes

only platform and body selected

→ projection on FEM

MAC calculation

measure 1 2 3 4

4

3

2

1

analy

sis

Modal Assurance Criterion

torsion

bending Very good correlation

for the global modes

correlation model test model

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Test

FEM

Eigen mode: Torsion

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X

XYZ

Y

Z

Step 3: Experimental Transfer Functions

Large number of output points groups


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node 1

node 2

node 3

node 4

Reduction to 14 groups / 42 curves

Comparison with simulation

4 nodes → 4 FRFs / shaker

→ Fahrzeugphysik

Mean value of these 4 FRFs




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Step 4: FEM Simulation

Model: TB...

Material Property Definition (MAT1)

Modal Frequency Response Analysis (RADIOSS)

FRF computed

Responses: same nodes as in the experiment

Results as curves (using the groups of experiment)

1 2 3 4 5 6 7 8 9

MAT1 MID E G NU RHO A TREF GE

Structural Element Damping coefficient Young’s Modulus

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Step 5: Comparison

BONNET

COOLER

FRONTEND

UPPER BODY

FLOOR

REAR DOOR

DOOR

D

M, K Fahrzeugphysik




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Step 6: Optimization with Optistruct: Objective

Run Type: Sizing Optimization

Design Response: DRESP1: acceleration for each node of a group

DRESP2: average of these accelerations

Objective function: MINMAX command

System identification with beta method (DSYSID)

- weighting factor

- target value

- response

target function target values (Ti)

response frequency sub ranges

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Step 7: Optimization with Optistruct: Variables

Design Variables (DESVAR / DVMREL1)

1 2 3 4 5 6 7 8 9

DESVAR ID LABEL XINIT XLB XUB DELXV DDVAL

user-defined name initial value

lower/upper bound

initial move limit ID for discrete values

1 2 3 4 5 6 7 8 9

DVMREL1 ID TYPE MID MPNAME C0

DVID1 COEF1 DVID2 COEF2 etc.

Spot Welds : HEXA solid elements

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Step 8: Sensitivity Analysis and Results

First investigation

adhesive lines of windscreen

and side windows

focus on the

most sensitive

FRONTEND

UPPER BODY

FLOOR

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Reconsider damping for glass parts / sealings




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Step 8: Sensitivity Analysis and Results

Second investigation

focus on the front

area of the car

only spot welds of the front area

FRONTEND

UPPER BODY

FLOOR

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Precise localisation by using 1 MID for each element

Spot Welds connected elements have to be further investigated




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Conclusion

Sensitivity analysis helps to highlight the areas with insufficient

characterisation of damping

Optimization allows to identify the potential to adjust damping

New measurements for the identified components

New model techniques

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updated model




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Acknowledgements

Fa. ID, G. Lindner for the experimental analysis

H. Gruber, Altair

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References

RADIOSS User’s Guide, version 10

Optistruct User’s Guide, version 10

HyperGraph User’s Guide, version 10

Geometry Correlation & MAC Calculation, FE-Graph - User’s Manual,

von Mach Engineering

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© Copyright 2010 EDAG GmbH & Co. KGaA. Alle Rechte vorbehalten. Charline Bonfils EDAG, Antoine Guellec AUDI AG, 06-09/11/2011 Folie 16 von 17

Thank you for your attention!

Questions?


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Documents

2011 European HyperWorks Technology Conference · 2011 European HyperWorks Technology Conference Model updating considering damping effects Charline Bonfils, EDAG GmbH & Co. KGaA