Estimation of the unstable fracture of pipe with a circumferential surface crack.

Abstract

Several criteria are proposed to predict the failure bending moment of a pipe which has a circumferential crack and is subjected to external bending moment in LWR (Light Water Reactor) pressure boundary piping. However, those criteria give an unconservative prediction when the pipe has a short and deep circumferential surface crack. This paper presents a half-empirical criterion on the basis of the test results. This criterion gives a conservative prediction by choosing the optimum parameter, even if the pipe has an arbitrary circumferential surface crack. This paper also presents a method to calculate a tearing modulus, TappL, of the pipe containing the circumferential surface crack just after the ligament failure. Moreover, the compliance of a four-point bending machine is converted to an equivalent pipe length, which is used to calculate the value of TappL.