– A double-edge-cracked plate of 7075-T651 aluminum has dimensions, as defined in Fig. 8.12(b), of b = 15.9 mm, t = 6.35 mm, large h, and sharp precracks with a = 5.7 mm. Under tension load, failure by sudden fracture occurred at a force of Pmax = 55.6 kN. Prior to this, there was a small amount of slow-stable crack growth, with the P-v curve being similar to Fig. 8.28, Type I, and crossing the 5% slope deviation at PQ = 50.3 kN
(a) Calculate K Q corresponding to PQ. (b) At the K Q point, determine whether or not plane strain applies and whether or not LEFM is applicable. (c) What is the significance of the K Q calculated?