Elastic–plastic response of unpressurised pipes subjected to axially-long radial indentation

Elastic–plastic force-deflection analysis of unpressurised pipes with long axial indentations are carried out. Solutions from an analytical method are compared to the corresponding finite element solutions and experimental test results. The analytical method is based on a simple energy-based approach developed to predict the initial gradients of the force-deflection curves and the limit loads of the indented rings using linear beam bending theory and upper bound theories. A comprehensive finite element study of indented unpressurised pipes is performed to study their sensitivities to the elastic–plastic responses. The finite element analysis covers six different materials, four different geometries and two different boundary conditions, and is compared with the corresponding analytical solutions. The results presented in this paper indicate that by using the analytical solutions for limit loads incorporating a representative flow stress as the average value of the yield stress and ultimate tensile stress, it is possible to obtain reasonably accurate predictions for the peak loads.