Design for cost performance of crashworthy structures made of high strength steel

The existing studies on thin-walled structures have focused on structural optimization mainly for enhancing crashworthiness and lightweighting, whilst relatively little attention has been paid to analysis of cost efficiency of an optimized structure. How to develop cost-effective products has always been a primary goal pursued by enterprises in different ways. To address this issue, this study aims to elucidate a systematic approach for exploring the effects of various material grades and structural dimension (e.g. wall thickness) on cost efficiency relative to the crashworthiness performance by taking the double-hat (DH) thin-walled structure as an example. First, a series of drop-weight tests for the DH structure are carried out under axial and lateral impacts. The experimental results show that different material grades and dimensions have different effects on the crash worthiness under different impact velocities. Second, the finite element (FE) models are established and validated with the experiments to analyze the effects of the three factors (wall thickness, material grade, and impact velocity) on the crashworthiness criteria. Third, the surrogate models for each crashworthiness performance indicator and cost efficiency (namely, specific energy absorption - SEA, bending moment - M-b, SEA/cost and M-b/cost) are constructed by using the regression technique. Finally, the combined effects of material grade and structural dimension on cost and performance are analyzed and compared respectively; and the results show that there is room to significantly reduce production cost without sacrificing the crashworthiness performance. For mass production implemented in modern automotive industry, the proposed design methodology allows to better balance performance and cost.