Answer:
2.93 mm
Explanation:
Plane strain fracture toughness [tex]K_{IC}=38.5 Mpa\sqrt{m}[/tex]
Yield strength, [tex]\sigma=535 Mpa[/tex]
Design stress=0.5*535=267.5 Mpa
Dimensionless parameter Y=1.5
Critical length of surface flaw is given by
[tex]a_c=\frac {1}{\pi}\times (\frac {K_{IC}}{Y\sigma})^{2}=\frac {1}{\pi}\times (\frac {38.5}{1.5*267.5})^{2}= 0.00293\approx 2.93 mm[/tex]