At the conceptual design stage, thin-walled beams (TWBs) with the complex cross-sectional shapes are extensively used to compose the automobile frame. Thus, the performances of automobile frame are determined by cross-sectional shapes of TWBs. Currently, the modifications of complex cross-sectional shapes depend on the experience of engineers, which often causes the design risk. Meanwhile, to our knowledge, the previous studies mainly focused on the regular cross sections and paid little attention for the complex cross-sectional shape for the automobile frame. Therefore, this paper proposes an analytical sensitivity analysis method to modify the complex cross-sectional shapes. This method regards the coordinates of points and the thicknesses of sheets as design variables to describe the cross-sectional shapes. The bending stiffness, torsional stiffness and frequency are used to evaluate the performances of automobile frame. Finally, an example of the RAV4 automobile frame verifies that the analytical sensitivity analysis method can effectively guide the modification of the cross-sectional shape and achieve the lightweight automobile frame.

在概念设计阶段，具有复杂横截面形状的薄壁梁（TWB）被广泛用于组成汽车框架。因此，汽车框架的性能由TWB的横截面形状决定。当前，复杂横截面形状的修改取决于工程师的经验，这通常会导致设计风险。同时，据我们所知，先前的研究主要集中在规则的横截面上，而对汽车车架的复杂横截面形状却很少关注。因此，本文提出了一种分析灵敏度分析方法来修改复杂的截面形状。该方法将点的坐标和薄片的厚度视为设计变量来描述横截面形状。弯曲刚度 扭转刚度和频率用于评估汽车车架的性能。最后，以RAV4汽车车架为例，验证了其分析灵敏度分析方法可以有效地指导截面形状的修改，实现轻量化。