Numerical Simulation of Circumferential Propagation of Surface Cracks on Pipeline Based on XFEM

In order to study the influence of surface circumferential crack defects on pipelines， based on the extended finite element method(XFEM)， a numerical simulation study was carried out on the crack propagation law of the X60 steel pipeline with circumferential circular surface cracks using the finite element software ABAQUS. Furthermore，the effects of crack location，internal pressure and initial crack size on the circumferential propagation of surface crack were discussed， and the maximum stress of the pipeline with cracked defects only under the action of internal pressure as well as the tensile displacement of the pipeline when the crack expands and penetrates the pipeline wall were analyzed.Results showed that the maximum stress on the pipeline was at the tip of the crack， and the stress there decreased after the crack expanded.When only under the action of internal pressure， the maximum stress of the pipe with circumferential cracks increased linearly with the rising of internal pressure， and the initial size and location of the crack had little effect on the maximum stress of the pipeline with circumferential cracks. Under the effect of axial displacement， the initial size of the crack had a significant influence on the displacement when the crack propagated. The axial displacement of the pipeline when the crack expands and penetrates the pipeline wall decreased rapidly with the rising of the crack size. When the crack size was in a certain range， the axial displacement of the pipeline when the inner wall crack expands and penetrates the pipe wall was smaller than the outer wall crack， which indicated that the crack on the inner wall was more dangerous. After the cracks increased to a certain size， the outer wall cracks became more dangerous.