Study on Criterion for Leak Before Break Assessment of Pressure Pipes

Based on the elasto-plastio fracture mechanics, this paper established the expression formulas of limit buckling pressure P_u on the ligament of axial and circumferential surface cracks and the initial pressure for the through cracks P_c. A new Leak Before Break （LBB） assessment criterion was put forward to predict the failure mode of pressure pipes, i.e., when P_u is less than P_c, the pipe will leak; when P_u is equal to or larger than P_c, the pipe will break, which is verified by the test data reported in literatures.