Lightweight Design Of Automobile Bumper Based On The Method Of Multi-Objective Optimization

Most of the accident of our country are caused by low-speed collision, in which there are two categories, one is the collision between car and obstacle that resulted in the damage on the front component of the car, but it is not harmful to driver and passenger. The other is the collision between the low-speed car and pedestrian, which begins at the contact of the car to the legform of the pedestrian and then the upper legform and headform. The collision caused a big harm to the pedestrian. In the paper, the structure of the bumper was optimized by using the method respectively of integrated balance method、response surface model and multi-objective genetic algorithms base on the variables of material and thickness to improve the performance of RCAR front40%low-speed impact and the requirements of the EEVC WG17.Based on the law of EEVC WG17, we establish the finite element model of the pedestrian protection of the lower-leg by the selection of test area and hard points; we also establish the finite element about the40%of the car’s width under the regulation of RCAR grade evaluation, and submit to Ls-dyna for calculation. The result is that the car we test can meet the performance of the pedestrian protection, while the RCAR40%front impaction has a poor performance, and because of the large invasion of the first contact point between the car and the RCAR obstacles, which cause a damage of the fins or the stringer behind the bumper.Taking the four components’material of the car bumper as variables, orthogonal experimental is designed and so is the integration of the optimize process, and the most important factor to the each performance of the bumper is found with the method of range analysis. The material matching of four components of car bumper is optimized with integrated balance method for improving both the performance of the pedestrian protection and RCAR evaluation which provide the basement for the subsequent mass optimization of the car bumper.Base on the optimization of the material matching of the component of the car bumper, the optimization of the thickness of the seven component of the car bumper system is made for the goal of lower weight. The Latin Hypercube experimental is designed for the seven components’thickness and then constructing the high-precision Response surface model in the Isight software. The Pareto Set was explored by using the multi-objective genetic algorithms NSGA-Ⅱ based on the model constructed before. Then simulation analysis about the effects of optimization is done on the most satisfactory set. The analysis shows that the mass of the car bumper reduced about1.61percent than before under the premise of the limitation of each performance of the car bumper.In the paper, the idea of the multi-objective optimization is applied to the lightweight design of automobile structure, which provides the methods of the optimization about the material and thickness of the automobile structure, which lays the foundation of lightweight design for the whole structure of the automobile.