1. A single edge cracked panel of an Al alloy is tested in tension to failure. The panel is 3 cm. wide, 1 cm. thick and the edge crack is 7.5 mm long. A displacement gauge is attached to the crack faces at the edge of the panel so that the load can be monitored as a function of the crack edge displacement throughout the test. A plot of measured load vs displacement for this specimen is shown in Figure 1. The yield strength of the alloy in question is 520 MPa and Young's modulus is 7 x 104 MPa. Poisson's ratio can be taken to be equal to 0.3. Calculate the plane strain fracture toughness from these data. 30 Load (KN) 20 10 0 0.0 10 10 0.1 0.2 0.3 0.4 Displacement (mm) 0.5 0.6 Figure 1. Load vs crack edge displacement for a single edge notch specimen.