Answer :
Answer:
Maximum permitted surface crack length is 1.29 mm
Explanation:
As per the question:
Tensile stress, [tex]\sigma = 10.5\ MPa = 10.5\times 10^{6}\ Pa[/tex]
Surface energy of magnesium oxide, SE = [tex]1.0\ J/m^{2}[/tex]
Modulus of elasticity of the material, E = 225 GPa = [tex]225\times 10^{9}\ Pa[/tex]
Now,
To calculate the maximum allowable surface crack length:
[tex]L = \frac{2E\times SE}{\sigma^{2}\pi }[/tex]
[tex]L = \frac{2\times 225\times 10^{9}\times 1.0}{10.5\times 10^{6}\times \pi } = 1.29\times 10^{- 3}\ m = 1.29\ mm[/tex]