A cylindrical thin walled pressure vessel is subject to an internal pressure of 4Mpa. The mean radius of the cylinder(r) is to be 500mm. If the low alloy steel from which it is made has a yield stress of 300MPa and a safety factor of 3 is to be used determine:

i) the wall thickness (t) using both the tresca and von mises theories of yielding.

ii) what value would you choose for the thickness of the cylinder?