The Research On The Front Bumper System Based On Lowspeed Collision And Pedestrian Leg Protection

The automobile bumper system is a safety device, which absorbs and relaxes the outside impulse, and protects the front part of car body. Under the low-speed collision, the bumper system can reduce the destruction to the automobile body, and protect both automobile and passengers. With the continuous improvement of pedestrian protection requirements both home and abroad, the shape of the vehicle will increasingly tend to consider pedestrian protection.While in pedestrians to car collision, the bumper system which located in front of the car body will contact directly with the legs, causing damage to the pedestrian legs. Therefore,protection of the pedestrian legs must also be one of the important targets as evaluated the safety performance of the front bumper system. In recent years, the low-speed collision and pedestrian leg protection are integrated into the bumper system’s development design cycle successively. In designing the bumper system comprehensive considering the low speed collision performance and the pedestrian leg protection function has certain guiding sense for structure optimization and improvement of car’s crashworthiness.Firstly, a finite element model of a car under the low-speed collision is established in accordance with the requirements of GB17354-1998, and the safety performance under the low-speed collision with center and corner impact is analyzed respectively. Based on the failure criterion of the bumper system, the impact properties under the two impacts are evaluated, and the influence of the material property and thickness of the foam and bumper beam on the impact crashworthiness is studied.According to the requirements of Euro-NCAP regulations, the collision of the front part of the vehicle bumper to the pedestrian legs is simulated, and the influence of main parameters of the bumper system on the protection of pedestrian legs is analyzed. The results show that car bumper system meeting the requirements of the automotive low-speed collision cannot satisfy the restricted hurt value of the pedestrian leg required by the Euro-NCAP regulation.Based on the simulation results, the improvement and the union optimization design to the bumper system are proposed by comprehensive considering the low-speed collision and pedestrian performance requirements, and the influence of the bumper parameters on the low-speed collision as well as the pedestrian leg damage are analyzed. The optimal combination of the system parameters satisfying car’s low-speed collision and the pedestrian’s legs protection requirements simultaneously are obtained. Then the integrated performance of the bumper system is optimized by the response surface methodology in the range of each parameter. Finally, the bumper system of the optional parameters is simulated. The results show that not only pedestrian leg protection performance is improved, and the crashworthiness requirement was met by using the optional parameters obtained by orthogonal design and response surface analysis, which indicate the feasibility of the two methods and provide valuable reference to the bumper system’s design and development.