Ductile crack growth behaviors at different locations of a weld joint for an X80 pipeline steel: A numerical investigation using GTN models

Abstract

The finite element method (FEM) based on the Gurson–Tvergaard–Needleman (GTN) model was used to investigate the ductile crack growth behaviors at different weld joint locations of X80 pipeline steel. As the result of the welding process, the X80 weld joints are inhomogeneous and can be divided into different zones (base metal, weld metal and heat affected zones), with different material properties and ductile crack growth resistance characteristics. By fitting the experimental results of uniaxial tension and single-edge notched bending (SENB) tests for specific zones, the GTN model parameters were calibrated in consideration of the inhomogeneity of the weld joint. The calibrated GTN models were then used to analyze the ductile crack growth behaviors in single-edge notched tension (SENT) tests at different locations of the weld joint. In addition, the effect of T-stress on the crack propagation at different locations was also studied using the small-scale yield model. It is demonstrated the calibrated GTN models are capable of predicting crack growth resistance curves at different weld joint locations, under different constraint conditions.