Cross-Section Design of the Crash Box to Maximize Energy Absorption

Vehicle collisions frequently happen at a low-speed. Insurance companies and the RCAR (Research Council for Automobile Repairs) require reducing repair costs and improving occupant safety in a low-speed crash. In order to reduce repair costs in the RCAR test conditions, an energy absorbing device such as the crash box (C/Box) is usually installed. The C/Box is a thin-walled structure attached between the vehicle bumper structure and the side rail. The determination of the C/Box geometry is quite important to absorb the impact energy since the installation space of the C/Box is not very large. In this research, the determination process for the cross-sectional dimensions is proposed to improve the energy absorption efficiency of the C/Box. The proposed process has two steps. First, the cross-sectional dimensions are determined by two ways. One is a parameter study using an orthogonal array and the other is topology optimization. The cross-sectional dimensions of the C/Box are selected among the available cross-sections, such as a circle and polygon. The cross-sectional dimensions are determined by the analysis of mean (ANOM) from the orthogonal array. And topology optimization is performed to determine the cross-section of the C/Box to maximize the absorbed strain energy based on the RCAR test conditions. The equivalent Static Loads method for non linear static response Structural Optimization (ESLSO) is employed to solve the formulated topology optimization problems. Second, the detailed design processes are performed by using an orthogonal array for the three models that are selected in the first step. The optimization problem for the C/Box is formulated considering the geometric constraints to fit into the given space for the C/Box. Through the proposed process, three new types of C/Box are suggested with the detailed shapes.