Axisymmetric deformation of circular elastic-plastic tubes under axial tension and internal pressure

Abstract

The axisymmetric bifurcation and post-bifurcation behaviour of circular tubes subjected to the combined action of axial tension and internal pressure are investigated numerically using the finite element method. It is assumed that the tubes are made of elastic-plastic strain hardening material with a smooth yield surface and that they deform without shear stress at both ends under the proportional stress path based on the stress values averaged over the cross-section. The bifurcation point and associated mode shape are obtained for each stress path. The initial to medium nonuniform deformation was studied for several specific stress paths and the growth of necking of the tube wall and swelling of the middle plane due to bifurcation are clarified.