A technique consisting of a marriage between stress freezing photo-elasticity and a numerical method was used to obtain stress intensity factors for natural cracks emanating from the corner at which a hole intersects a plate surface. Geometries studied were: crack depth to thickness ratios of approximately 0.2, 0.5 and 0.75; crack depth to crack length ratios of approximately 1.0 to 2.0; and crack length to hole radius ratios of about 0.5 to 2.0. All final crack geometries were grown under monotonic loading &r6 growth was not self similar, with most of the growth occurring through the thickness under remote extension. Stress intensity factors were determined at the intersection of the flaw border (i) with the plate surface (KSs) and (11) with the edge of the whole (KH,). Results showed that for the relatively shallow flaws KH = 1.5KS, for the moderately deep flaws KH = KS and for the deep flaws K„ » O.5KS5, revealing a severe sensitivity of !C to flaw geometry. Results were compared with the Bowie Theory, and approximate criteria developed by Hall and Finger and Hsu and Liu. These comparisons showed that these theories significantly over-estimated the SIF for moderately deep flaws a/t = 0.5 at both the plate surface and the hole, but for shallow flaws, and Hall-Finger theory under-estimated the SIF at the hole and the Bowie theory under-estimated the SIF at the surface for deep flaws.
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