Dynamic axial crush analysis and design optimization of a square multi-cell thin-walled tube with lateral variable thickness

In this paper, we proposed a strategy to improve the energy absorption efficiency of a square multi-cell tube by designing the lateral wall thickness distribution. We uniformly arranged the walls so that we could vary the thickness of the walls while forming a square multi-cell tube. Explicit formulations for predicting the mean crushing force of the multi-cell tube under axial compression were derived based upon the Super Folding Element method. The energy absorption capacities of a variety of typical square multi-cell tubes with different lateral thickness distribution were obtained by theoretical and numerical analysis. The predicting results of the formulations have good agreement with the numerical simulation performed by explicit non-linear finite element method. The theoretical and numerical results showed that the energy absorption capacities could be improved by modifying the lateral thicknesses of the multi-cell tube. The optimization based on a surrogate model and the explicit prediction formulations was carried out to find the optimal lateral thickness distribution of 3 × 3 square multi-cell tube. We found that the tube has better energy absorption properties when the material is concentrated in the center of the cross-section. Based on the optimization results, a non-convex multi-corner multi-cell square tube with lateral variable thickness was proposed that resulted in a 48.3% improvement in energy absorption capacity compared with traditional uniform thickness multi-cell tube.