Determination of Tensile Strain Capacity of Girth-Welded X70 and X100 Grade Pipelines With Surface Cracks Under Tension and Bending

Abstract

Abstract. This paper presents a comprehensive finite element analysis using abaqus to obtain the tensile strain capacity (TSC) of X70 and X100 pipelines with external semi-elliptical cracks in the heat-affected zone (HAZ) under tension and bending. The analysis estimates the crack driving forces using the J-integral in relation to the pipeline's remote strain. Subsequently, the evaluation of TSC was carried out employing both initiation and ductile tearing criteria. The study investigates the effects of internal pressures, HAZ softening levels, loading type, and weld strength overmatch ratios on TSC. The results reveal similar trends in TSC between the initiation and ductile tearing criteria, as well as between tension and bending for both types of steel. Notably, TSC decreases with increased HAZ softening and internal pressures, while higher overmatch ratios appear to enhance it. These findings highlight the critical influence of these factors on the structural integrity of pipeline girth welds, offering essential insights for the design and maintenance of pipeline systems.