On instability failure of corroded rings under external hydrostatic pressure

• An analytical model was used on buckling of corroded rings under external pressure.
• Verification against FEA results shows improved accuracy.
• Stress analysis in detail reveals the location of maximum stress.
• A simple singular perturbative method is proposed to calculate bifurcation pressure.

Analytical formulations were derived for bifurcation pressure and non-linear static analysis of a corroded ring under external pressure. The mid-surface inextensional condition was included in the derivation which resulted in much improved accuracy in the prediction of bifurcation pressure. Afterwards, an analytical method was presented to solve the non-linear deformation problem of a corroded ring with initial ovality included under external pressure. A finite element analysis was carried out to verify the accuracy of the developed model. By setting the initial yielding as the failure criterion, a parametric study was carried out to study the effect of corrosion depth and corrosion angular extent. Moreover, the interaction effect of two circumferential corroded regions on the critical pressure was studied. Finally, some comments on the analytical methods were given to consider the case of continuously varying thickness and an alternative perturbative method was proposed. This research is intended to enhance the understanding of instability and failure for a corroded tube under external pressure mainly applicable to offshore industry.