Investigating energy absorption of thin-walled steel structures with combined mechanisms including inversion, folding and expansion

In this research, thin-walled steel energy absorbers were investigated. The introduced structures absorb energy through the processes of inversion, folding and expansion. Each absorber consists of two end-capped frusta and a cylindrical shell. The intended absorbers were experimentally made and then tested. The mechanical properties of the used materials were extracted by performing tensile tests and then used for simulation. The simulations of this research were carried out using LS-DYNA software. After comparing the experimental and numerical results, a good agreement between the results was observed and then the obtained results were discussed. The intended absorbers were examined in terms of the thickness of the lower frustum, the height of the middle shell and the angle of the upper frustum. The obtained results showed that by increasing the thickness of the lower frustum, energy absorption in the inversion process increased. In addition, the investigations related to the effect of height on the collapse properties showed that increasing the height of the middle shell with a thickness of 2 mm for the lower frustum led to a decrease in energy absorption. Also, in the investigations carried out on the half angle of the frustum, it was found that the contribution of energy absorption in the expansion process was low.