Evaluation of crack opening displacement of through-wall circumferential-cracked pipe using direct weight function method

This paper presents a direct weight function-based method to evaluate the crack opening displacement (COD) which is a key parameter in leak-before-break (LBB) assessment and in probabilistic fracture mechanics (PFM) assessment of nuclear piping systems. The focus of this study is a circumferential-cracked pipe with non-linearly through-wall distributed stress loaded on the crack face. Parametric finite element analyses (FEA) were performed to calculate COD associated with different crack face pressure (CFP) loadings. The analyses matrix covers a wide range of pipe size and crack lengths. The crack mouth COD values at three locations: at outside surface, inner surface and mid-thickness were considered. The numerical results were then used to determine the coefficients that construct the direct weight functions. The proposed solution can be used to predict the COD resulted from given weld residual stress (WRS) field with the general prediction error being less than 8%. The research outcome can provide more computational efficiency in both deterministic LBB assessment as well as PFM analyses of pressurized pipes.