The study on fracture response of cracked pipeline considering the Lüders effect

Abstract

Since pipeline steel typically exhibits yield discontinuities, some pipelines may experience high local strains during service that exceed the strain limits required by existing fracture assessment methods, thereby posing a significant threat to pipeline integrity. By establishing a finite element fracture model of a cracked pipeline with the Lüders effect and incorporating a developed constitutive model with a trilinear stress-strain relationship, the mechanical and fracture responses of the cracked pipeline with the Lüders effect under uniaxial tensile loading are analyzed in this study. The effects of crack configurations and material parameters on the crack driving force are discussed in detail. The results indicate that an increase in crack length and strain hardening exponent lowers the crack driving force plateau and shortens its length. Conversely, increases in crack depth, softening modulus, and Lüders strain raise the crack driving force plateau. Specifically, as crack depth increases, the plateau length of the crack driving force shortens, while an increase in the softening modulus and Lüders strain extends the plateau length. These conclusions provide guidance for the fracture analysis and assessment of pipelines with cracks affected by the Lüders effect.