Plastic collapse of thin-walled elasto-plastic pipes under internal pressure and superposed axial loading

This paper is concerned with the failure analysis of elasto-plastic thin-walled pipes under combined internal pressure and axial loading (monotonic or alternating). Depending on the loading history (pressure and axial loading histories) the pipe may exhibit a different mechanical behavior due to the progressive accumulation of plastic deformation. The study, performed under different loading histories, is adequate to identify the history dependent failure pressure. The analysis of the results allows obtaining a very simple safety criterion for the plastic collapse. The main result is that, regardless the load history, a safe region can be defined analytically in the space of circumferential and axial stresses. A comparison of the theoretical predictions with experiments shows coherent preliminary results. The simplified methodology proposed in this study provides a safe and reliable preliminary tool for designers and engineers that can be used to help to plan inspection and preventive maintenance.