Lightweight Beam Structure Topology Design Solution for Steel and Aluminum Hybrid Body

Abstract

To solve the problems of low bending and torsional stiffness and high weight of the all-steel body-in-white (BIW), an aluminum (Al) alloy profile with optimized cross-section is used to replace the original sheet metal threshold beam. Firstly, considering the feasibility of extrusion process, the Al alloy profile cross-section is designed based on the original threshold beam cross-section. Then, we extracted the equivalent load acting on the center of mass of the threshold beam section during the calculation of the bending and torsional stiffness of the BIW, and carried out the planar topology optimization with the design boundary conditions to minimize the cross-sectional flexibility, resulting in an Al alloy section with superior performance. The optimization results show that the bending stiffness and torsional stiffness of the BIW are improved by 2.1% and 3.4%, respectively, after replacing the Al alloy foundation beam with internal reinforcing ribs. Additionally, there is a 5.0% enhancement in first-order bending mode and a 2.7% improvement in first-order torsional mode, accompanied by a slight weight reduction of 0.1%.