Material arrangement optimization for weight minimization of an automotive body in white using a bi-level design strategy

In this study, we propose a practical approach for designing an automobile body in white using multiple materials. This approach includes design optimization to reduce the weight subject to bending and torsional stiffness constraints in a real application considering realistic limitations on the product development time. Whereas conventional bodies in white are at present composed of only steel, we reduce the weight by using steel and aluminium. Although there have been many studies related to body-in-white design, practical design processes have rarely considered the whole vehicle body owing to the difficulties in handling the large number of design variables. Therefore, the proposed design optimization strategy consists of two levels: on the first level, many design variables are screened for significance and, on the second level, the significant design variables are optimized. The screening drastically reduces the number of design variables, from 195 to 81, allowing efficient optimization on the second level. By using this approach, the weight of a reference body in white was reduced by 27.3% while satisfying all the design requirements.