Characterizing properties of pipeline girth welds: A novel testing protocol and validation

Accurate, region-specific mechanical properties of pipeline girth welded joints are fundamental for structural safety design and integrity assessment. This study focuses on X80 pipeline girth welded joints, integrating microstructure analysis, small-scale in-situ tensile tests, full-wall-thickness tensile experiments, and finite element (FE) simulations to validate the necessity and accuracy of refined mechanical parameter testing across joint regions. Based on the Gurson-Tvergaard-Needleman (GTN) damage model, region-specific parameters of the girth welded joint were precisely calibrated and applied to FE models. Results indicate that the refined partitioned FE models closely replicate experimental load-displacement curves, strain distributions, fracture initiation points, and crack propagation paths. Geometric discontinuities and material weaknesses in the coarse-grained heat-affected zone (CGHAZ) were identified as primary contributors to strain concentration and joint failure under tension load. This work establishes a methodological framework for refined mechanical characterization and fracture analysis of high-grade pipeline girth welds, providing an important reference for safety design and structural integrity assessment.