Abstract: Lightweight design of car body structure is in demand to meet performance requirements of modes, stiffness, collision safety, etc. In order to improve the robustness of design, the uncertainty factors in the design process must be considered. In a variety of optimization designs, non-dominated sorting genetic algorithm NSGA-Ⅱis more and more widely used in the multi-objective and reliability engineering design. After application of high strength steel to the body structure in attempt for lightweight, the investigative procedures are carried out as follows to determine the effective thickness values of the key structure components in the front body structure: first, the finite element models of both the body in white and the 40% offset frontal collision are established; second, the property indexes including the torsional stiffness of entire body in white, the maximum collision force and the mean acting force, the collision energy absorption and the minimum mass etc. are considered throughout in the multi-optimization model, and then the NSGA-Ⅱ algorithm is used to perform 6σ reliability optimization based on the high-precision response surface approximation model; at last, Monte Carlo simulation technique is used to evaluate the robustness performance of the optimization scheme. The optimization results show that the vehicle collision safety performance is improved and the body torsional stiffness and structural component weight are well controlled.

Key words: Carbody structure, Lightweight, Multi-objective optimization, Reliability design