5) A cylindrical steel pressure vessel of 7.5 m diameter and 40 mm wall thickness is to operate at a working pressure of 5 MPa. The design assumes that small cracks may be present that will gradually extend due to fatigue. a) If the fracture toughness of the steel is 200 MN /2, would you expect the vessel to fail by leaking, or by fast fracture? [6% ] The growth of a crack may be represented by the equation da ACAK) dN Where do/dNV is the extent of crack growth per loading cycle and K is the stress intensity factor for the crack