Experimental and numerical investigation of the strain response of a dented API 5L X52 pipeline subjected to continuously increasing internal pressure

Abstract

A dent is a common type of defect that occurs during pipeline service. A dented region on a pipe usually creates a strong stress concentration that may become a threat to the safety and integrity of the pipeline. Therefore, such issues are major concerns for pipeline managers. To investigate the strain history behaviour of a dented steel pipeline subjected to increasing internal pressure, a full-scale experimental burst test was performed, and a nonlinear finite element method was used to compare the numerical and experimental results in this study. The paper first discusses the test specimens and test results. Then, the finite element numerical results are verified using the experimental measurement results. Subsequently, the strain behaviour at measurement points and the deformation behaviour of the test pipes were analysed in detail. Furthermore, a sensitivity analysis of strain in the axial and circumferential directions from the dent centre was performed. Deformation analysis reveal that an outward convex phenomenon occurred in axial shoulders on both sides of the dent when the Pipewall Yield Pressure reached. Test results and finite element analysis show that the strain in the dented regions changes rapidly and sharply with a large range, which can easily lead to fatigue under operation pressure for an unconstrained dent.