Answer: 0.0033 m = 3.3 mm (0.13 in.)
Explanation:
since this problem requires us to calculate the maximum internal crack length allowable for the 7075-T651
aluminum alloy is given that it is loaded to a stress level equal to one-half of its yield strength.
For this alloy, KIc 24 MPa [tex]\sqrt{m}[/tex](22 ksi [tex]\sqrt{in}[/tex]); also, σ= σ_y/2 = (495 MPa)/2 = 248 MPa (36,000 psi).
Now solving for 2ac gives us;
2a_c=2/π (K_IC/γσ)^2=2/π [(24MPa √m)/(1.35)(248MPa) ]^2=0.0033m=3.3mm (0.13 in.)