Multi-objective Robust Optimization Design Of Crashworthiness Of Vehicle Structure

With the rapid development of the automobile industry, the ownership of vehicles has increased year by year, and the safety requirements of the vehicles are becoming much higher. The optimization design research of vehicle structures for crashworthiness is of great significance in improving its safety. In the process of optimization design of vehicle structures for crashworthiness, the design variables are treated as deterministic values in traditional optimization methods; while in practical, uncertain factors such as material properties and structure geometr ies etc., are frequently encountered in the optimization process of the vehicles. And for the existence of these uncertain factors, it is possible for the optimal value of the objective function derived by deterministic optimization to violate the constraints, and thus affecting the quality characteristics of the products. Therefore, it is necessary to take the influences of the uncertain factors on the crashworthiness design of vehicles into consideration, to formulate a robust optimization design.In this paper, to improve the crashworthiness and robustness of the passenger vehicles, three collision forms including the side impact, the 100% frontal impact and the 25% small overlap frontal impact of the vehicles are studied in the optimization design. The specific research contents and results are stated as follows:1) A multi-objective robust optimization design for crashworthi ness of vehicle structures based on the optimal polynomial response surface is proposed. B y the structural selection techniques of the error reduction ratio, the optimal polynomial response surface used for substitution of the practical v ehicle side impact model is constructed; and by the combination of the 6σ conception from the management engineering, the multi-objective robustness optimization design for the side structure of a certain vehicle is carried out. When constructing the multi-objective robustness optimization model, the material properties and the structure geometries are treated as uncertain design variables. According to the result, both the crashworthiness of the side structure and the robustness of the crashworthiness index es are improved.2) Combined with the optimal polynomial response surface method, a multi-objective robustness optimization method is proposed for vehicles under different crash conditions. Consider the crashworthiness of the vehicle under 100% and 25% small overlap frontal crash conditions, and take five structural parts of the vehicle’s forepart as the research objects, the multi-objective robustness optimization design is carried out by integrating experimental design and NSGA-II genetic algorithm(GA). The optimization results show that the acceleration of the vehicle body under 100% overlap frontal crash is reduced by 12.6%; the treadle invasion value under 25% small overlap frontal crash is also reduced, and both the crashworthiness and the robustness of the object ive response are improved to some extent.In conclusion, the robustness optimization design method developed in this paper is able to improve the crashworthiness and robustness of the vehicle structures comprehensively, which shows engineering practicability and also provides an enlightened approach for crashworthiness and robustness optimization design of vehicle structures under different crash conditions.