8.) A thin-walled pressure vessel is made of the 7075-T651 aluminium alloy given in Q6. The internal pressure induces a circumferential hoop stress of 200 MPa. The vessel has a semi-elliptical surface crack oriented such that its major plane is normal to the hoop stress. For this type of loading and geometry conditions, K is given by K = 1.120 Q Where, Q = p - 0.212 2(%ys); 3 ; + 8 8 c What is the critical crack size that will lead to rupture of the pressure vessel it its wall thickness is 12 mm and the a/2c ratio of the crack is 0.5? What would be the critical crack length if its a/2c ratio is 0.05? If the inner diameter of the pressure vessel is 90 cm, what is the maximum pressure that can be permitted in the vessel?