Quantification of J-integral for the circumferentially cracked pipes under mechanical and thermal loads between R6 and A16

As most part of pressurized plant components are subject to various stresses. Stresses applied to plant components can be classified into primary (mechanical loading) and secondary stress (such as thermal and residual stress). When a crack is found in a pressurized plant component under combined primary and secondary stress, it is important to estimate relevant fracture mechanics parameters. J-integral is one of the fracture mechanics parameters used for elastic plastic analysis. Detail procedure for J-integral estimation under combined stresses are tabulated in R6 and A16. This paper compares the estimated J-integral between R6 and A16 for combined stresses through FE analysis results. J value for the fully circumferential surface crack are conservative in contained yielding regime in A16 method. But in R6 method, less conservative result in contained yielding regime. Under large scale yielding (LSY) regime, R6 simplified method and A16 method produced similar result to J estimation. But detailed method are close to the FE results even for large Lr values. And this paper revealed that occurs when thermal loading is applied after mechanical loading the most severe loading sequence