This paper aimed at improving a bumper system to meet the second phase EEVC (European Enhanced Vehicle Safety Committee) requirements for pedestrian lower leg protection. An approach is presented to optimize the front bumper system for minimizing the risk of pedestrian's lower leg injuries from the bumper impact. Firstly, a vehicle FE model was developed, a two-layer-material EA (Energy Absorber) and a lower stiffener were also developed to attach in the front bumper system. Then some structure parameters of the EA and the lower stiffener were selected and the design of experiment with orthogonal arrays was used to generate the test sample points. Finally, the multi-objective optimization of the structure parameters was conducted based on the NSGA-II (Non-dominated Sorting Algorithm). The maximum tibia acceleration, the maximum knee bending angle and the maximum shear displacement were chosen as the objective functions. The optimized results were used to redevelop the EA and the lower stiffener FE modals. The results of the study show that the performance of the vehicle for lower leg protection could be dramatically improved by the optimization of EA and lower stiffener and the second phase EEVC requirements for pedestrian lower leg protection can be satisfied.
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