Axial crushing and optimal design of square tubes with graded thickness

• Square tubes with graded thickness are experimentally studied under axial loading.
• Energy absorption characteristics of tubes with graded thickness are investigated.
• Graded thickness leads to up to 30–35% increase in energy absorption efficiency.
• Numerical simulations by LS-DYNA compare very well with experiment.
• RSM optimization is conducted and validates the merits of graded thickness.

Introducing thickness gradient in cross-section is a quite promising approach to increase the energy absorption efficiency and crashworthiness performance of thin-walled structures. This paper addresses the deformation mode and energy absorption of square tubes with graded thickness during axial loading. Experimental study is firstly carried out for square tubes with two types of thickness distributions and numerical analyses are then conducted to simulate the experiment. Both experimental and numerical results show that the introduction of graded thickness in cross-section can lead to up to 30–35% increase in energy absorption efficiency (specific energy absorption) without the increase of the initial peak force. In addition, structural optimization of the cross-section of a square tube with graded thickness is solved by response surface method and the optimization results validate that increasing the material in the corner regions can indeed increase the energy absorption efficiency of a square tube.