Computational simulation of ratcheting in dented pipes due to monotonic and cyclic axial loading

Abstract

This article presents a computational simulation framework developed to capture the ratcheting response of dented straight pipes. The results are compared against the results obtained from our previously conducted experiments. Ratcheting occurs when a structure is subjected to a primary axial load along with a secondary cyclic load, provided that the applied loads are sufficiently large in magnitude to cause the material to yield. The dented pipes investigated in this study were initially subjected to a monotonic axial compression load, which caused the initiation of small amplitude wrinkles, and were subsequently subjected to an axial cyclic loading regime. A nonlinear finite element analysis, using a combined hardening model, was adopted to model the response of the material during the entire loading regime. The parameters required by the material model were obtained from cyclic tests conducted on representative coupon specimens. The results of the numerical simulations were compared to experimentally obtained data. The results demonstrated that the ratcheting response of dented pipes could be numerically simulated with a reasonable accuracy. The results also revealed that the surface imperfections exerted a very pronounced effect on the ratcheting response of the dented pipes. The computational model was also used to investigate the influence of some key parameters, such as the initial strain level, stress amplitude, mean stress, loading regime, and material hardening properties, on the resulting ratcheting.