Specifying Steel Properties and Incorporating Forming Effects in Full Vehicle Impact Simulation

Mechanical properties of as-rolled steels used in a vehicle vary with many parameters including gages, steel suppliers and manufacturing processes. The residual forming and strain rate effects of automotive components have been generally neglected in full vehicle crashworthiness analyses. Not having the above information has been considered as one of the reasons for the discrepancy between the results from computer simulation models and actual vehicle tests. The objective of this study is to choose the right material property for as-rolled steels for stamping and crash computer simulation, and investigate the effect of forming and strain rate on the results of full vehicle impact analyses. Major Body-in-White components which were in the crash load paths and whose material property would change in the forming process were selected in this study. The post-formed thickness and yield stress distributions on the components were estimated using One Step forming analyses. Material properties of the steels at elevated strain rates are obtained from dynamic tensile tests. Results were compared for different analysis scenarios based on crash modes, vehicle accelerations and velocities at concerned locations. The results demonstrate that incorporation of material properties after forming and at high strain rates are necessary to improve the prediction accuracy of frontal impact analysis. Incorporating forming and strain rate effects in full vehicle impact simulation needs very little extra effort.