You are working for an aerospace contractor building lightweight pressure vessel

Question

You are working for an aerospace contractor building lightweight pressure vessels from beryllium metal (p=2.0 g/cm^3,K_1c=4 MPa sqrt(m), yield stress=155 MPa) for rocket applications. A x-ray system used to search for cracks in pressure vessels can detect cracks as small as .1 mm in length. You are asked if the system is good enough to detect all cracks that might result in rupture of the pressure vessel before plastic deformation can occur. Provide a response with a calculation to back up your answer. Assume Y=1

Explanation / Answer

crack will propagate when Ki will be greater than Kic.

Ki = Y*sigma *(pi*a)^0.5

so for crack to propagate, 1*sigma*(pi*0.1*10

so sigma = 225.67MPa

this value of sigma is higher than the Yield strength of the material.so the stress required for brittle failure due to crack propagation is higher than stress for ductile failure. so failure will be ductile and hence the test is good enough to be use as a passing test.^-3)^0.5 = Kic

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