Research On The Thin-Walled Structure In Bumper For Pedestrian Protection

Pedestrians are in the most disadvantaged position in the traffic system, and they are the most vulnerable groups. Data shows that pedestrian casualties in traffic accidents is in the high. Currently, pedestrian protection have been got more and more governments and car manufacturers attention. Front bumper is the initial contact position with the pedestrian in an collision between car and pedestrian, but also it absorbs energy initially in the vehicle frontal collision. Therefore, the research on the internal structure of the front bumper for both energy absorption in front collision and the protection of pedestrians is very urgent and necessary.The structure requirement of bumper for pedestrian protection is pointed out in this paper. Design guideline is proposed that the structure should have the maximum deformation energy absorption in premise of the protection of pedestrian. Firstly, the traditionally compressing thin-walled tube is studied. Setting section sizes as design variable, sampling points been chosen according to comprehensive experimental design, the sample models are on the finite element analysis by Ansys/LS-DYNA respectively. The deformation energy absorption and acceleration values corresponding to the sample design variables are recorded. The functions of deformation energy absorption and acceleration values to the section sizes are constructed seperately using response surface method. The optimizational crashworthiness definition of compressing thin-walled tube for pedestrian protection is put forward, and the sectional sizes are optimized. Because of the scale of acceleration, compressing thin-walled tube is very difficult to achieve the standard of pedestrian protection.With new research ideas, thin-walled tube occur plastic deformation by expanding to achieve the purpose of energy absorption. Because of the existence of many factors, each factors are analysed by orthogonal experimental method to get the most influential factors to the deformation energy absorption and the acceleration, the wall thickness of thin-walled tube and the maximum diameter of cone block being the result. The two factors are optimized with the optimizational crashworthiness definition of expanding thin-walled tube for pedestrian protection. Optimizational parameters of expanding thin-walled tube meeting the structural requirements are got.In the destination of pedestrian protection, there is space left in bumper. Variable stiffness structure is put forward combining the characteristics of both expanding and compressing tube. At this time, the optimal expanding structure get shorter, so the influence of the truncated thin-walled tube is analysed. The optimizational crashworthiness definition of the back compressing thin-walled tube for the front collision is put forward, and the sectional sizes are optimized. Optimizational parameters of the back compressing thin-walled tube meeting the structural requirements are get. The variable stiffness structure combined by the front expanding tube and the back compressing tube is optimizational for both pedestrian protection and frontal collision.According to the structure of bumper and variable stiffness tube, the layout plan of the filled structure in the internal bumper is proposed, and the number of the absorption components is determined. The finite element models of the pedestrian-car collision and the front collision are established, and they are evaluated with their evaluating indicator under the collision velocity by laws. The pedestrian-friendly bumper using the optimizational structure is verified.