Engineering approach for circumferential flaws in girth weld pipes subjected to bending load

• J and CTOD estimation procedure for defective girth weld pipes containing surface cracks along weld centerline is proposed.
• Coupled effects of mismatch ratio and geometry on J (CTOD) become important when overmatching level surpasses 30%.
• The applicability analysis determines its effectiveness for bimetallic configurations with overmatch ratio less than 30%.
• Errors between simulations and proposed solutions are less than 10% for the maximum J value attained by a reeled pipe.

The current investigation pursues extending the applicability of fully plastic solutions for J-integral and crack-tip opening displacement (CTOD), originally cataloged in a series of handbooks (also known as EPRI handbooks), in defective girth weld pipes subjected to bending load for a wide range of surface crack dimensions and weld strength mismatch levels. The suitability of the given set of solutions in this work is constrained by a certain number of parameters that are derived from the coupled effect of weld strength mismatch and configurational effects upon near-tip stress-strain fields in heterogeneous media. These results reveal a weak dependence of coupled effect of weld strength mismatch and weld groove size upon crack driving force, when the ratio of the mismatch between weld and base normalizing stresses is considered moderate (≤1.3), whereby the proposed estimation method becomes essentially valid for failure assessment procedures and fitness-for service (FFS) evaluations.