Energy absorption of thin-walled circular tubes with gradient thickness under oblique loads

Introducing nonuniform thickness has shown promising potential in enhancing the energy absorption of thin-walled tubes. However, existing studies were focused on the axial loading, with little attention being paid to the oblique loading condition. In this paper, the energy absorption performance and the deformation modes of the circular tubes with gradient thicknesses under oblique loads are investigated. Finite element simulations and experiments were carried out for both uniform-thick and gradient-thick tubes under the axial and oblique loads, and satisfactory agreement was achieved betweent the numerical and the experimental results. The validated finite element models were used to investigate the effects of the thickness gradient and loading angle on the deforamtion modes and the energy absorption. The results highlight the advantages of the gradient-thickness tubes in improving the energy absorption performance under the oblique loading condition, especially at a larger loading angle. A novel progressive bending deformation mode was observed for the tube with large thickness gradient at a loading angle larger than 15 degrees, which is beneficial for the energy absorption performance.