On design of multi-cell tubes under axial and oblique impact loads

• Finite element modeling and experimental validation for multi-cell tubes are conducted.
• The crashworthiness of a group of multi-cell tubes under multiple load cases is investigated.
• The multicriteria decision making process is adopted.
• Multiobjective optimization design for multi-cell tubes under multiple load cases is conducted.

Multi-cell tubes have been drawn increasing attention for their excellent energy-absorbing ability. However, the effect of cell number and oblique loads on crashing behaviors has seldom been studied to date. In this paper, a group of multi-cell tubes with different cell numbers were comprehensively investigated under both axial and oblique loads. The finite element models were first established and then validated by experimental tests. The simulation results showed that the increase in cell number can be beneficial to the energy absorption (EA) but detrimental due to increase in peak force (Fmax) under axial load. When the oblique loads were taken into account, the tubes could undergo global bending, which is an inefficient deformation mode. By applying complex proportional assessment (COPRAS) method, the 7×7 tube was selected as the best based on multi-criteria under multiple loading angles. Then the Kriging modeling technique and multiobjective particle optimization (MOPSO) algorithm were integrated to address the optimization problems, where EA and Fmax were taken as objectives and tube sizes as design variables. The results demonstrated that different loading angles have different requirements on cell allocation and optimizations of multiple load cases (MLC) can yield better solutions in a weighted average fashion, whereas the optimization for separate single load cases (SLC) could result in inferior performance under other load cases.