Fracture assessment based on unified constraint parameter for pressurized pipes with circumferential surface cracks

The fracture assessment capability and methodology based on the unified constraint parameter Ap have been comparably investigated with the conventional procedures without considering constraint effect and the assessment approach based on the constraint parameter Q for pressurized pipes with circumferential surface cracks. The results show that the Ap can be used in failure assessment diagram based fracture assessment by modifying the fracture toughness using the unified correlation formulae of fracture toughness with Ap. A fracture assessment methodology based on the parameter Ap for incorporating both in-plane and out-of-plane constraints has been proposed. The constraint characterization and fracture assessment using the parameter Ap for the pipe cracks may get the best accuracy and can reduce excessive conservatism of the conventional assessments. The benefits from the unified constraint assessments increase with decreasing crack depth and length.