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New materials, new simulation approaches
By Design News Staff -- Design News, October 6, 2002
Wilhelm Karmann, best known for the famous Karmann Ghia, has started to include stamping simulation data in its crash simulations. By adding information on the increased hardening effects of DP600 steel following the forming process, Karmann is achieving better correlation between crash simulation and prototype testing.
Wilhelm Karmann is a full-service supplier to the automobile industry with particular expertise in convertibles. The company has developed and manufactured more than three million automobiles for major OEMs including the Mercedes CLK and the Audi A4 convertibles. Karmann engineers use a variety of simulation software, including PAM-STAMP for stamping and PAM-CRASH for crash and occupant safety simulation.
Karmann regularly reviews new materials that could optimise the vehicle's structural behaviour while at the same time reducing overall weight. "The new high-strength steel DP 600 has excellent crash behaviour when used for specific components," says Norbert Schulte-Frankenfeld, manager of CAE at Karmann. "The CAE engineers give input on which parts would benefit from this steel. We need to have a body structure as light as possible, so using DP 600 steel is one way to reduce overall vehicle weight."
However, after the stamping process, the DP 600-based parts have both a higher yield stress and varied thickness. DP 600-based parts which have either a large strain during the stamping process or a particularly high load during crash could therefore effect the overall crash behavior of the complete vehicle. For this reason, the company launched a study to identify which components require the input of stamping data into the crash simulation data.
A preliminary study was performed on the reinforcement for the A-pillar in the body-in-white of a convertible. This A-pillar reinforcement compensates the weaker car structure because of the missing roof. The study compared, among other things, crash simulations of the high-strength DP 600 part with and without the stamping data.
The results indicated that this DP 600 part had a significantly higher load level if the stamping history is taken into account because of the pre-straining during the forming process, and this behavior would significantly influence the crash results.
"We are currently working on a new vehicle project, and for certain new steel parts we have included the stamping data into the crash simulation," said Schulte-Frankenfeld. "However, we are continually evaluating how to optimize the application of the stamping data so that it is only used where it is really needed. Optimal use of stamping data will help us obtain good correlation with the test data, without overburdening the simulation." Enter the number at www.designnews.com/info: PAM-CRASH from ESI: Enter 535
