The energy absorption of a shrinking-expanding circular tube: An experimental and numerical investigation

A new type of combined energy absorber working on the principle of shrinking and expanding of the circular metal tube was proposed. First, quasi-static experiments of aluminum alloy tubes were conducted. The results show that this type of energy absorber is completely feasible. Afterward, finite element models were established to estimate the tube deformation and force-displacement response, which were in good agreement with the experimental results. A theoretical solution for the steady-state crushing force of the tube was derived. Moreover, the effects of various structural parameters were investigated using a validated finite element model. According to the results, the force increases with the increase of the wall thickness and has a monotonically decreasing relationship with the radius of the shrinking die, but it first decreases, then increases with the increase in the cone angle of the expanding die. Compared with the energy absorber that only produces shrinking deformation, the steady-state force of the combined absorber is increased by 123%, and the energy absorption under the same stroke is higher. The result can provide guidance for the optimal design of the collision energy-absorbing structure on a rail vehicle.