Development of Stress Intensity Factors for Subsurface Flaws in Plates Subjected to Polynomial Stress Distributions

The stress intensity factor (SIF) solutions for subsurface flaws near the free surfaces of components, which are known to be important in engineering applications, have not been provided yet. Thus, in this paper, SIF solutions for subsurface flaws near the free surfaces in flat plates were numerically investigated based on the finite element analyses. The flaws with aspect ratios a/ℓ = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5, the normalized ratios a/d = 0.0, 0.1, 0.2, 0.4, 0.6, and 0.8, and d/t = 0.01 and 0.10 were taken into account, where a is the half flaw depth, ℓ is the flaw length, d is the distance from the center of the subsurface flaw to the nearest free surface, and t is the wall thickness. Fourth-order polynomial stress distribution in the thickness direction was considered. In addition, the developed SIF solutions were incorporated into a Japanese probabilistic fracture mechanics (PFM) code, and PFM analyses were performed for a Japanese reactor pressure vessel (RPV) containing a subsurface flaw near the inner surface. The PFM analysis results indicate that the obtained SIF solutions are effective in engineering applications.