The car front bumper system needs to meet the requirements of both pedestrian safety and low-speed impact which are somewhat\ncontradicting. This study aims to design a new kind of modular self-adaptive energy absorber of the front bumper system which can\nbalance the two performances. The X-shaped energy-absorbing structure was proposed which can enhance the energy absorption\ncapacity during impact by changing its deformation mode based on the amount of external collision energy. Then, finite element\nsimulations with a realistic vehicle bumper system are performed to demonstrate its crashworthiness in comparison with the\ntraditional foam energy absorber, which presents a significant improvement of the two performances. Furthermore, the\nstructural parameters of the X-shaped energy-absorbing structure including thickness (tu), side arc radius (R), and clamping\nboost beam thickness (tb) are analyzed using a full factorial method, and a multiobjective optimization is implemented\nregarding evaluation indexes of both pedestrian safety and low-speed impact. The optimal parameters are then verified, and the\nfeasibility of the optimal results is confirmed. In conclusion, the new X-shaped energy absorber can meet both pedestrian safety\nand low-speed impact requirements well by altering the main deformation modes according to different impact energy levels.
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