Simulation of fatigue properties for the weld joint of the X80 weld pipe before and after removing the weld reinforcement

Abstract Fatigue fracture in pipelines is the major failure mode during the service of oil and gas pipeline transportation. Welded joints, as the weakest region of a line-pipe, should be paid more attention firstly. Due to the need to remove the weld reinforcement at the beginning and end of each part of the pipeline for connection, it is necessary to study the fatigue properties of the welded joints before and after the removal of the weld reinforcement. In this work, a model with different heat affected sub-zones in the finite element analysis (FEA) was conducted to explore the fatigue properties of the welded joints with and without weld reinforcement for a ferrite/bainite dual-phase X80 line-pipe. The results show that the initiation positions of fatigue cracks are significantly different, and the fatigue strength is increased by about 1.3 times after removing the weld reinforcement. The reasons for the change of the initiation position before and after the removal of the weld reinforcement are discussed in terms of the material properties of HAZ and the effect of weld reinforcement. At the same time, the influence range of stress concentration at the weld toe on the fatigue property of the X80 line-pipe was analyzed by the FEA.