Multidisciplinary optimization of an automotive door with a tailored blank

Abstract

The automotive door has many design requirements such as stiffness, natural frequency, side impact, etc. Thus, various related governing equations should be solved for systematic analysis and design. It is almost impossible to solve them simultaneously. Instead, they are separately handled and the analysis results are incorporated into the design separately. Multi-disciplinary optimization (MDO) can be exploited well to include various analysis disciplines. Firstly, single optimization methods are carried out by considering one discipline for the automobile door design. Various optimization formulations are defined and the formulated problems are solved to determine the topology, shape, and size of the door with a tailored blank. The design is expanded to MDO to consider multiple disciplines. Although existing MDO methods are mathematically excellent, they are only adequate for the design of airplane wings. In this research, a few MDO methods are proposed to solve problems that share design variables among disciplines. This idea is from the fixed-point root finding method for multidiscipline analysis. Firstly, optimization of the entire system is divided into multiple domains according to the required analysis methods. Secondly, design variables are assigned to one domain according to the contribution or sensitivity. An optimization formulation is defined for each domain. Thirdly, optimization is performed at each domain where only the assigned variables are regarded as design variables and others are constant. If all the design variables are updated, then the single optimizations are iteratively conducted until the design is not changed. The developed method is verified by a standard mathematical problem. Then the developed methods are applied to the design of an automobile door. The design considers the stiffness, the natural frequency, and the side impact of the door. Most of the optimization processes use mathematical optimization. When mathematical optimization is too complicated, an approximation method such as the response surface method (RSM) is utilized. The developed methods show stable convergence and the weight of the door is reduced by 15 per cent. Since commercial systems are employed for analysis and design by coding the interfacing parts, the developed methods can be easily utilized in design practice. © IMechE 2006.