Predicting the crack response for a pipe with a complex crack.

摘要

Traditional flaw evaluation in the nuclear field uses conservative methods to predict maximum load carrying capacity for flaws in a given pipe. There is a need in the nuclear industry for more accurate estimates of the load carrying capacity of nuclear piping such that probabilistic tools can be used to predict the time to failure for various types of cracks. These more accurate estimates will allow the nuclear industry to repair flaws at a more appropriate time considering external factors such as costs and man-rem planning along with the flaw repair. Analysis of the maximum load carrying capacity of a pipe with a complex crack (CC) has gained increased importance due to the recent identification of long CC's that have appeared in dissimilar metal (DM) welds thought to be caused by primary water stress corrosion cracking (PWSCC).;A coded solution for a single material with a weld was developed that gives an accurate maximum load and crack driving force prediction for a pipe with a through wall crack (TWC), called LBBEng. To support the analysis of a CC, traditionally, an assumption is used that the CC performs similar to that of a TWC of a reduced thickness (TWCr). This modification gives a conservative prediction of the maximum load carrying capacity for a CC in a single material but was never verified for a CC in a DM weld. From the evaluation of the DM weld test data, along with finite element analysis, it can be demonstrated that the crack response of a CC can be predicted by a TWC model when modifications are made to the reduced thickness method.