Study on pure bending collapse of square tubes in consideration of work-hardening effect

In this paper, the elastoplastic collapse of square tubes subjected to the statically pure bending is studied by using the finite element method (FEM). It is found that there are three types of collapse modes. The first type is a collapse mode due to buckling at the compression side. The second type is a collapse mode due to flattening of the cross section. The third type is a collapse mode by mixing the first type and the second one. Based on these facts, approximate numerical methods to estimate the maximum moment of these collapse modes are proposed, and their validity are verified by comparing with numerical results of FEM.