Optimizing the layout of nested three-tube structures in quasi-static axial collapse

• Making a difference in the height of multi-tube structures is a good way to reduce the maximum force.
• Through optimization, absorbers with high energy absorption capacity and low maximum force can be achieved.
• Reducing the difference between the tubes will lead to a reduction in force mutations.

In this study, energy absorption characteristics of aluminum nested three-tube structures as one of the types of thin-wall energy absorbers were experimentally and numerically examined and some optimal conditions were presented for such structures. In so doing, after determining the type of alloy and stress-strain curves of the tubes, four samples were analyzed under quasi-static collapse. The structures were simulated using finite element software LS-Dyna and the results were compared with data from experimental tests. There was good agreement between experimental and numerical results. After comparing multi-tubular structures with single conventional structures, it was indicated that these structures have a higher capacity to absorb energy. Then, with considering different height and thickness for the structures, the optimal value of these quantities was determined and it was shown that through optimizing three-tube structures, the maximum collapse force can be as low as possible and energy absorption capacity can be hold high. Finally, by optimizing the results with response surface method using Minitab software, samples with optimal performance in the process of collapse were obtained.