Experimental and Numerical Investigation of Failure Criterion of Girth Welds With I-II Mixed Mode Crack Considering Crack Tip Constraint Effect

Abstract In practical engineering scenarios, the establishment of a robust fracture criterion for girth welds featuring mixed mode cracks has become pivotal for ensuring pipeline safety. To account for the influence of shear deformation of micro-voids, the shear-modified Gurson-Tvergaard-Needleman (GTN) model for girth welds was determined. Compact-tensile-shear (CTS) tests, employing digital image correlation technology, were conducted to analyze the I-II mixed mode fracture behavior. The area enclosed by the plastic strain contour (Ap) at the crack tip was utilized to characterize the constraint state of the crack tip, while the J-integral was employed to characterize the crack fracture parameters. Employing finite element numerical calculations, the study analyzed the effects of load parameter, material damage parameters, material mechanical properties parameters, and size parameters on resistance curve of I-II mixed mode cracks, and crack tip constraint state of CTS samples. Furthermore, a linear correlation between the constraint state and the fracture toughness of CTS samples was established. Leveraging a neural network regression prediction algorithm, a data-driven prediction model for the fracture toughness of girth welds with I-II mixed mode cracks was proposed. This research serves as a valuable reference and guide for the analysis of fracture behavior and safety evaluation of pipeline girth welds with I-II mixed mode cracks.