The plastic loss of stability of a thin-walled tube under axial compression

A theoretical model of the plastic shaping of ring folds in the axial compression of a thin-walled tube with smooth plates after local loss of stability is presented. The initial stage of the shaping is calculated using membrane theory of a rigid-plastic envelope under the von Mises plasticity condition, taking into account the deformation strengthening and the change in the wall thickness. The final stage is calculated using moment theory with the finite curvature of the curvilinear parts of the folds. The calculated forms of the folds and the force-displacement dependences when there is loss of stability agree satisfactorily with experimental data.