Prediction of Failure Bending Moment for a Pipe With an Arbitrary-Shaped Circumferential Flaw

Abstract

When a flaw is detected in a stainless steel piping system, failure bending moment can be predicted by limit load criterion in accordance with Appendix E-8 in the JSME S NA-1-2004 and Appendix C in the ASME Code Section XI. However, in these current codes, the limit load criterion is only calculated for the case of a pipe containing a single flaw with constant depth, although the actual flaw depth is variable along the circumferential direction. Particularly, geometrical shapes of stress corrosion cracks are generally complex. The objective of this paper is to propose a method for predicting the load-carrying capacity by formula for a pipe containing a circumferential surface flaw with any arbitrary shape. The failure bending moment is obtained by dividing the surface flaw into several sub-flaw segments. Using this method, good agreement is observed between the numerical solution and the reported experimental result. Several numerical examples are also given to show the validity of this method. Finally, it can be found that the number of the sub-flaw segments is sufficient to be three for the semi-elliptical surface flaw.