1. What is the magnitude of the maximum stress that exists at the tip of an internal crack hav- ing a radius of curvature of 1.9 X 10-4 mm (7.5 X 10-6 in.) and a crack length of 3.8 X 10-2 mm (1.5 X 10-3 in.) when a tensile stress of 140 MPa (20,000 psi) is applied?
2. Estimate the theoretical fracture strength of a brittle material if it is known that fracture occurs by the propagation of an elliptically shaped surface crack of length 0.5 mm (0.02 in.) and having a tip radius of curvature of 5 X
3. A specimen of a 4340 steel alloy with a plane strain fracture toughness of 54.8 MPa 1m (50 ksi 1in.) is exposed to a stress of 1030 MPa (150,000 psi). Will this specimen experience fracture if it is known that the largest surface crack is 0.5 mm (0.02 in.) long? Why or why not? Assume that the parameter Y has a value of 1.0.