Abstract: The finite element model for the collision between the front-end of a car and the lower legs of a pedestrian is established, and a simulation on which reveal that as the injury indicators of pedestrian legs, the peaks of the tibial acceleration at the center of the bumper (Y₀), the tibial acceleration and the knee bending angle near the energy absorption box (Y₃₉₀) all exceed safety threshold. In order to improve the pedestrian leg protection performance of vehicle, thirty sets of aluminum honeycomb energy-absorbing structures with six different honeycomb cell lengths and five different honeycomb cell thicknesses are designed according to energy-absorbing space and analyzed with LS-DYNA to get the changing trend of the corresponding mean square evaluation (MSE) and specific energy absorption (SEA) of pedestrian legs at Y₀, with the relative optimum 14 mm of honeycomb cell length determined. Then an optimization is conducted by using software Hyperstudy and LS-DYNA integrated optimization technique with minimizing the MSE of pedestrian legs at Y₃₉₀ as objective and the thicknesses of the front cover plate and honeycomb cell as variables. After optimization, all three injury indicators of pedestrian legs at both Y₀ and Y₃₉₀ reduce significantly and meet the requirements of safety threshold. The aluminum honeycomb energy-absorbing structure optimized effectively improves the pedestrian leg protection performance of vehicle

Key words: pedestrian leg protection, vehicle front-end structure, aluminum honeycomb, optimization