A cylindrical pressure vessel with closed ends, internal radius of 0.4 m and a wall
thickness of 10 mm is to be subjected to a combination of internal pressure and an
external axial tensile force of magnitude 50 kN while in service. The external axial force is
applied through rigid plates at the ends of the cylinder. Determine the maximum allowable
internal pressure if the tensile stress in the cylinder is not to exceed 35 N/mm2.
Force= Pressure(internal) / (pi*r(i)^2) = Axial Stress * (2pi*r(i)*t)
r(i)= inner radius
t= wall thickness