The vessel is to be tested to ensure crack of the size found in b) is not present. You have the choice of doing the test with water or air - What will you choose and why? To what pressure must the vessel be raised in the pressure test to ensure it can survive 3000 load cycles?

5) A cylindrical steel pressure vessel of 7.5m diameter and 40mm wall thickness is to operate al working pressure of 5MPa. The design assumes that small cracks may be present that will gradu extend due to fatigue. a) If the fracture toughness of the steel is 200MN3/2, would you expect the vessel to fail by leaki or by fast fracture? The growth of a crack may be represented by the equation dNda=A(K)4 Where da/dN is the extent of crack growth per loading cycle and K is the stress intensity factor for the crack. b) Calculate the maximum crack length that can be present for the vessel not to fail after 3000 loading cycles from zero to full load and back again. Tests have indicated that under these conditio A=2.441014(MNm2)4m1 c) The vessel is to be pressure tested to ensure cracks of the size found in b) are not present. You have the choice of doing the test with water or air - which would you choose and why? To what pressure must the vessel be raised in the pressure test to ensure it can survive 3000 load cycles