A cylindrical pressure vessel of radius 1.2m and thickness 4 mm is made from Ductile steel. a. If the pressure if varied cyclically between 0 and 0.4p, for the resulting cyclically varying combined biaxial stress state, estimate the equivalent mean stress, stress amplitude and stress ratio. b. Using the Soderberg fatigue failure criteria estimate value of the pressure p that will lead to failure after 108 cycles. The material yield strength is 300Mpa and the fatigue strength is 250 MPa (at 108 cycles).