Crush Behavior of Spot Welded Hat Section Components With Material Comparison

Abstract

The computer aided design of vehicle steel alloy structures is well understood and fairly reliable. Finite element (FE) models for crash analysis, in both frontal and side impact, can be developed with high degrees of fidelity, and are playing a major role in automotive design today. The substitution of aluminum alloys in the load bearing components has added a level of complexity in the FE modeling. Issues related to validation of material constitutive models, failure modes, fracture and general material modeling have to be addressed in these new materials. This paper describes the results of a study conducted to investigate and compare the crush performance of mild steel and aluminum alloy in main frontal load bearing vehicle components. Finite element models of spot-welded hat section stub columns were created and numerically simulated using the non-linear dynamic code LS-DYNA3D. Recommendations are provided for both FE models and simulation parameters in order to obtain an accurate and fair representation of the real test. Much of the analysis is obtained on optimization of results with respect to computation time. The crush behavior of hat section stub columns was studied under quasi-static and dynamic loading rates and then validated against published experimental results. Two different steel alloys and two different aluminum alloys have been used in the analysis. The strain rate effect has been considered for the steel alloys under two crushing rates of 8 m/s and 12 m/s. The mathematical modeling of resistance spot-welding joints in aluminum was also considered. Parameters as energy absorption, peak crush load capacity, and the crush distance are used to compare the crush behavior of steel and aluminum alloys in the main load bearing components.