DIFF-CRASH

Stability Analysis for Simulation Results

Logo DIFFCrash

DIFF-CRASH is a software package for the stability analysis of crash simulations. Physical bifurcations in automobile design and numerical instabilities in simulation packages often cause extremely sensitive dependencies of simulation results on even the smallest model changes. Among other things, DIFF-CRASH allows the designer to find these critical structural regions and offers suggestions for their removal.

 

Info

 

Flyer

DIFF-CRASH: Robust Design

Press Release

Licenses

Starting 01.01.2013 DIFF-CRASH will be distributed and further developed by
SIDACT GmbH.

www.sidact.com

 

 

Background

DIFF-CRASH
© Fraunhofer SCAI
Comparison of the node positions of parallel simulation runs on 32 SP-2 CPUs (each curve compares two simulations).

In collision simulations, quite often there are large deviations among the calculated results. These deviations are caused by rounding errors which either are incorporated systematically into the initial data or which result randomly from parallel computations. These errors can propagate either because of the model properties of because of the numerical algorithms used in the code. 

The figure shows a comparison of the results of simulations attained with PAM-CRASH. A BMW model with 60,000 elements was calculated on a parallel computer with distributed memory. Deviations simular to the one shown were also observed on SMP architectures. 

In order to investigate these effects, SCAI, together with ESI and the BMW-group developed DIFF-CRASH.

Functions DIFF-CRASH

Arbeitsweise von DIFF-CRASH
© Fraunhofer SCAI
Flow chart for DIFF-CRASH
  • processes the results of several simulation runs
  • delivers a statistical analysis of the whole model as well as of individual nodes
  • generates data formats which can be used by the VR-visualization system developed by FHI-IMK
  • incorporates data into PAM-CRASH's simulation results so that they can be analyzed with PAM-VIEW

Examples from Industrial Practice

DIFF-CRASH

Figure 1 shows typical results from DIFF-CRASH simulations, which are displayed on the Institute's Responsive Workbench. The colors show diverse variations in the simulation results.

CONTACT 46

SCAI has analyzed larger variations in simulation results on a real BMW test model. It turned out that in many cases an edge-to-edge detection would have led to the correct simulation result. On a model which was reworked with CONTACT 46, substantially reduced variations were observed. Using the correct contact model influenced the simulation results.

Motor Carrier

Figure 5 shows variations of the results in the drivers foot area in the reworked model. This was perhaps due to the instability of a certain part of the motor carrier. Figure 6 shows a more detailed analysis: The variety of variations after a simulation run of 35 milliseconds was quite noticeable.

Various simulation results highlighted in colour.
© Fraunhofer SCAI
Various simulation results highlighted in colour.
Various simulation results highlighted in colour.
© Fraunhofer SCAI
Various simulation results highlighted in colour.
Various simulation results after 20 milli seconds. Results are for a model with and without using CONTACT 46.
© Fraunhofer SCAI
Various simulation results after 20 milli seconds. Results are for a model with and without using CONTACT 46.
Various simulation results after 20 milli seconds. Results are for a model with and without using CONTACT 46.
© Fraunhofer SCAI
Various simulation results after 20 milli seconds. Results are for a model with and without using CONTACT 46.
A view from the back of the automobile into the foot area shows different simulation results.
© Fraunhofer SCAI
A view from the back of the automobile into the foot area shows different simulation results.
Various simulation results of the left motor carrier 35 milliseconds after the collision.
© Fraunhofer SCAI
Various simulation results of the left motor carrier 35 milliseconds after the collision.