Effects of In-Service Strain on Girth Weld Failure of an X80 Pipeline

Abstract In general, transmission pipelines are designed by hoop stress induced by internal pressure, and maximum longitudinal stress. The paper is mainly about the failure analysis of an X80 pipeline brittle fracture on girth weld under in-service strain. The digital image correlation (DIC) in the tensile tests was used to analyze the permanent plastic strain on girth weld metal under in-service strain. Then, the Charpy energy of the girth weld metal with the concentrated plastic strain was tested to evaluate the deterioration of toughness. Finally, the mechanism of the brittle fracture of the girth weld is clarified. The results show that the girth welds may have obvious plastic deformation under an elastic in-service strain of the pipeline. It may lead to a significant deterioration of the toughness, which results in the failure of the pipeline under the strain-controlled load.