Crack Growth Testing of an X80 Pipeline Girth Weld Using SE(T) and SE(B) Fracture Specimens

Abstract

Accurate measurements of fracture resistance properties, including crack growth resistance curves for pipeline girth welds, become essential in defect assessment procedures of the weldment region and the heat affected zone, where undetected cracklike defects (such as lack of penetration, deep undercuts, root cracks, etc.) may further extend due to to high tension stresses and strains. This work presents an investigation of the ductile tearing properties for a girth weld made of an API 5L X80 pipeline steel using experimentally measured crack growth resistance curves ((J-Δa curves). Use of these materials is motivated by the increasing demand in the number of applications for manufacturing high strength pipes for the oil and gas industry including marine applications and steel catenary risers. Testing of the pipeline girth welds utilized side-grooved, clamped single edge notched tensiles (SE (T)) specimens and three-point (3P) bend single edge bend (SE(B)) specimens with a weld centerline notch to determine the crack growth resistance curves based upon the unloading compliance (UC) method using a single specimen technique. Recently developed compliance functions and η-factors applicable for SE (T) and SE(B) fracture specimens with homogeneous material and overmatch welds are introduced to determine crack growth resistance data from laboratory measurements of load-displacement records. This experimental characterization provides additional toughness data which serve to evaluate crack growth resistance properties of pipeline girth welds using SE (T) and SE(B) specimens with weld centerline cracks.