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An aluminum plate which had a 0.8 in . diameter hole in the middle, failed when it was subjected to a 40 ksi tensile stress. Post mortem of the failure indicated brittle fracture due to presence of a sharp crack, which was located in the perpendicular direction to the reference stress. The plate edges were far away from the opening. Estimate the size of the crack if the plane-strain fracture toughness of aluminum was 27 ksi (in.) ^((1)/(2)).
Figure 3.10 Comparison of correction factors for double and single cracks at round holes (DC, double crack; SC, single crack) (from Ret. 6).