Injury biomechanics-based nondeterministic optimization of front-end structures for safety in pedestrian–vehicle impact

Abstract

Lower extremity is the most frequently injured body region in a pedestrian–vehicle impact. To evaluate lower extremity injuries, both the Flexible Pedestrian Legform Impactor (FlexPLI) and the Flexible Pedestrian Legform Impactor with Upper Body Mass (FlexPLI-UBM) have been used in practice. In general, UBM would have considerable influence on the design of front-end structures. In this study, a sedan was used to perform the experimental tests first for evaluating the effects of different lower extremities. The experimental results indicated that placement of UBM can lead to a higher risk evaluation of knee ligament damage and a more significant increase in femur bending moment than that in tibia bending moment. Second, a new multiobjective discrete robust optimization (MODRO) algorithm was developed to optimize front-end structures subject to FlexPLI-UBM impact involving uncertainties. In the proposed MODRO algorithm, the order preference by similarity to ideal solution (TOPSIS) was coupled with the fuzzy approach for developing a fuzzy multiple attribute decision making (MADM) model for converting multiple conflicting objectives into a single unified cost function. The presented optimization procedure is iterated using the successive orthogonal experiment to deal with a large number of design variables and design levels. The optimal results showed that in contrast to the structures subject to the FlexPLI impact, the front-end structures under FlexPLI-UBM impact require a higher stiffness of tibia contact area but a lower stiffness of knee and femur contact area. This study provides automotive engineers with new insights into the injury biomechanics-based design of frontal structure from a road safety perspective.