Due to increasingly shorter development times and high licence fees, there is a desire for calculations to be completed as quickly as possible while ensuring the same quality of results. As part of a research project TECOSIM realise significant saving on calculation times for crash models.

1. Reducing calculation times for crash models
Abstract of research project results

2. More details require more computing capacity
1. INITIAL SITUATION
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§ Today's vehicle models for crash simulation contain around three million elements and
take between 24 and 48 hours to calculate, depending on the code and hardware
§ There is a desire for greater detail, so that special effects can be reproduced
§ This will increase the calculation time further
§ Due to increasingly shorter development times and high licence fees, there is a desire
for calculations to be completed as quickly as possible while ensuring the same quality
of results

3. Aims and specifications of the research project
2. TASK
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§ examine crash models in ABAQUS Explicit
§ Reduce calculation time by around 30 per cent
§ Significance/validity of models to remain same as in the base model
§ As less time and effort to adapt existing models as possible
The project was funded by the German Federal Ministry of Economics as part of its Central
Innovation Program (ZIM).

4. Method and procedure
3. SOLUTIONS
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§ Parts of the model which have no impact on results for a particular loadcase are
defined as a rigid body. These are perfectly stiff and therefore require hardly any
calculation time.
§ Rigid bodies automatically dissolved as soon as the component enters the influence
zone of deformation
§ Multi-STEP and restart function are used in ABAQUS to dissolve the Rigid Body and re-
start the model with current boundary conditions
§ The approach was checked on analogous models and applied to a complete vehicle
afterwards

5. Preliminary studies on partial models
4. PROJECT DESCRIPTION / IMPLEMENTATION
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§ Testing the methodology: "switching from rigid to
deformable" on a simple square tube
§ Challenge: element properties cannot be changed
between two ABAQUS steps
§ Solution: import the current stress loads and node
speeds and apply them to an updated model using a
script
§ Apply the method to a partial model (vehicle front
end 56 km/h against rigid wall)
Method test: square tube against
rigid wall
Front end of a TEC|BENCH model

6. Verifying the method on a complete vehicle model
4. PROJECT DESCRIPTION / IMPLEMENTATION
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§ One rigid body per include
(modelling time kept low)
§ Bumper include is the only one not set as rigid.
If minimum stress loads occur there, all adjacent
includes will be switched from rigid to
deformable, etc.
§ Potential: more detailed sub-division into more
rigid bodies since the body in white extends
throughout the whole vehicle and thus rigids are
also converted in the rear section at a very early
stage.Partitioning into rigid bodies by includes –
optimisation potential: subdivide body in
white into several includes
TEC|BENCH model: 520,000 nodes and 2.8
million degrees of freedom

7. Significant saving on calculation time
§ A saving of almost 20 per cent on calculation times for partial model and almost 10 per
cent for complete vehicle model were achieved with almost identical results
§ A more detailed rigid body partition, separate from the includes, would lead to much
more savings.
§ The method can also be adapted and optimised for different load conditions (front,
side or rear)
5. RESULTS AND PROSPECTS
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8. TECOSIM Technische Simulation GmbH
Wolfgang Woost
General Manager
Wilhelm-Wagenfeld-Str. 3
D-80807 Munich
Tel +49 (0)89 552 679-17
Fax +49 (0)89 552 679-22
Mail w.woost@de.tecosim.com
www.tecosim.com
Contact:
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