Assessment of the resolution of nonplanar flaws in pressure retaining components in terms of stress intensity factors

Lacroix, V.*; Dulieu, P.*; Hasegawa, Kunio

When flaws are detected, assessments are done to demonstrate the fitness-for-service. The first step is the flaw characterization determining the flaw geometry for analyses. This key step is done by flaw characterization rules provided in FFS Codes. According to the flaw characterization rules of ASME Code Section XI, a nonplanar flaw shall be resolved into two planar flaws by projection of the flaw area into planes normal to the maximum principal stresses. This approach allows to simplify the flaw assessment but remains conservative. Therefore, the conservatisms by the simplified projection for nonplanar flaws are investigated in this paper. Current computations have been improved so that the modelling of nonplanar flaws are not significant difficulty. This paper compares the stress intensity factors (SIF) of projected nonplanar flaws and the mixed mode SIF of actual nonplanar flaws. The scope is to quantify how the flaw projection into planes normal to the maximum principal stresses is conservative.