Effect of Internal Pressure on Tensile Strain Capacity of X80 Pipeline

Abstract

This paper examines the influence of internal pressure on the tensile strain capacity of pipelines. A pressurized full-pipe tension test and curved wide plate (CWP) test were conducted together with FE analyses in order to investigate the strain behavior of pipe under large axial loading with high internal pressure. The critical tensile strain drastically decreased under a high internal pressure condition. Single edge notch tension (SENT) tests with shallow notched specimens were also performed to obtain the material resistance curve (R-curve), and a series of FE analyses was conducted to obtain the crack driving force for ductile crack propagation. The R-curve and crack driving force curve were used in predicting the tensile strain limit of X80 girth welded pipe with a surface defect in the HAZ. The predicted critical tensile strain showed good agreement with that obtained in the pressurized full-pipe tension test. These results demonstrate that the tensile strain capacity of pressurized pipes can be predicted by using the R-curve from SENT tests and the crack driving force curve from FE analyses.