Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
A New Approach for IIHS shell elements barrier model
development
Salim Abdennadher (Altair)
Petros Goutas (CELLBOND), Franck Njilie (Altair)
Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
IIHS side MDB : Radioss shell model
IIHS Side MDB aims to evaluate vehicle occupant protection
Barrier shape and crushing strength represents SUV’s and pickups vehicle front ends.
Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Honeycomb scaled cell size modeling method
Honeyomb structure
3
5
056.16
S
tm
Mean crushing strength in principal cell axe direction (T. Wierzbicki 1983)
S
t
S
t
=> Target time step and barrier number of elements adjusted by thickness to cell size ratio
Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Honeycomb scaled cell size modeling method
=> Applied successfully for ODB and FMVSS214/301 MDB
S
t
Realistic barrier deformation shape
Better prediction of loading events in full vehicle crash test simulation.
Better prediction of biomechanical criterion
CPU time acceptable regarding the accuracy improvement
Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Safety tools : development scheme
M
Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Parameters IIHS Side FE Model Version 100
Radioss Version 10
Natural time step (µs) 1.0
Nodes 474,926
1D elements (beam /
spring) 2/28
Shell 4-nodes 492,959
Shell 3-nodes 1,619
Solids (Tetra4 / Bricks) 0/17,731
IIHS side MDB : Radioss model statistics
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Test configuration IIHS with or without
bumper
Mass of trolley and
impactor (kg)
Impact velocity
(m/s)
Number of
tests
IIHS against flat LCW w
1503 13.9 m/s 2
IIHS against flat LCW w/o 1503 11.5 m/s 2
Pole against IIHS w 1498 8.3 m/s 2
Sill against IIHS w/o 1499 7.9 m/s 1
Sill against IIHS w 1499 7.9 m/s 1
IIHS side MDB : Validation test matrix
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IIHS side MDB : Beta version validation status
Entrapped air has some effect at certain level of crush.
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IIHS side MDB: Cellbond sample test
Sample shape after full crash
Impactor (falling mass)
Rigid support & loadcell
Honeycomb
sample
Test set up
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IIHS side MDB: Cellbond sample test correlation
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IIHS side MDB: Flat wall test
Entrapped air has significant effect at certain level
of crush.
The air effect will be introduced by using Radioss
monitored volume with adequate pressure function.
Modeling air effect
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IIHS side MDB : release version validation status
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IIHS side MDB : release version full vehicle crash test
Copyright © 2009 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Conclusion & perspective
Conclusion
In some test configuration (mainly rigid flat wall cases), air entrapped inside honeycomb cells
generates additional resistance to honeycomb structure.
The air effect modeling option has been validated through sample tests provided by CELLBOND.
In order to enhance the IIHS MDB Radioss FE model reliability, air effect has been successfully modeled.
The actual model accuracy has been proven for the hole validation test matrix (pole impact, Sill test …)
Perspective
Carry back the air effect modeling option to ODB and FMVSS214/301
Partnership with CELLBOND : European side MDB coming soon.