-For the material and member of Prob. 11.31, replace the loading with repeated applications of the axial force history shown in Figure P11.50. How many repetitions are required to grow the crack from ai = 2 mm to failure?

A double-edge-cracked member of 7075-T6 aluminum has dimensions, as defined in Fig. 8.12(b), of b = 28.6 and t = 2.3 mm, and it contains equal initial cracks on each side of length ai = 2.0 mm. Estimate the number of repetitions of the load history shown in Fig. P11.51 necessary to grow the cracks to failure. Materials constants as in Table 11.2 apply, except that the fracture toughness for this thickness is Kc = 78.7 MPa√m.

-For the material and member of Prob. 11.31, replace the loading with repeated applications of the axial force history shown in Figure P11.50. How many repetitions are required to grow the crack from ai = 2 mm to failure?

A double-edge-cracked member of 7075-T6 aluminum has dimensions, as defined in Fig. 8.12(b), of b = 28.6 and t = 2.3 mm, and it contains equal initial cracks on each side of length ai = 2.0 mm. Estimate the number of repetitions of the load history shown in Fig. P11.51 necessary to grow the cracks to failure. Materials constants as in Table 11.2 apply, except that the fracture toughness for this thickness is Kc = 78.7 MPa√m.