Question

1. AA 6061, a high-strength aluminum alloy, has a 0.2% offset yield strength of 37,500-psi and a plane strain fracture toughness (Kic) 26,400-psi (inch) At a service stress equivalent to 80% of the yield strength, will this structure fracture if it contains an edge crack of length 2.24-inches. Assume that the geometric factor, f, is 1.12. 2. A steel alloy, which has a plane strain fracture toughness (Kle) of 49-MPa(m) is exposed to a service stress of 1010-MPa. Is fracture predicted if it is known that the largest surface crack (2a =2-mm) in length? Assume f= 1.

Answer 1

The calculations are attached below :

We know, K= fracture toughnem k=forzal 0 = Applied strem. f = Geometrical factor a = crack length (1) Given, f=1.12. K = 26, 400 psi.(inch) 2 2a = 2.24 inch 0.2% offset 10) = 37,500 psi 80% [ yeild strem io '- (39 500X0.8) psi = 30,000 psi K'= forza → k'21-12 x 30000 x H x TaxP.12 => K'= W 63026.5 psikinch)? The value of k is much higher than fracture toughnen of the material. Hence, crack will occour. (2) Given, f= 1.00 K = 49 MPa. (m)² = 49X100 Pa. (mitz o = 1010 MPa = 1010 X106 pa 20 = 2 mm > a = 10m. x= forza x = 1x 1010x108 AJ 2x103 >> K = 56.81 MPalms. The value of k is much higher than toughnen . Hence, fracture will occour. fracture