Comparative study on determination methods of resistance curves of circular joints based on single edge notched tensile specimens

In recent years, single edge notched tension (SENT) specimens have been used for strain-based design and evaluation of pipelines, and several fracture toughness testing standards have been developed, including DNVGL-RP-F108, CANMET, BMT, USP and BS 8571. However, there are still great differences between relevant test standards in test principles, test methods and calculation methods of fracture toughness. It is necessary to further study the differences between them. Therefore, different determination methods of crack tip opening displacement (δ) and J-integral resistance curves for clamped SENT specimens of API X80 pipeline girth weld joints were compared. By fitting the J-R curves, δ-R curves and initial fracture toughness values J_0.2 and δ_0.2, the recommended equations for the fracture toughness resistance curve of SENT specimens were given.