Hi all, i need some help working out the following;
a cylinder has;
internal diameter 60mm = 0.06m /2 for radius = 0.03m
external diameter 100mm = 0.10m /2 for radius = 0.05m
the cylinder is subjected to an internal pressure of 20Mpa
and external pressure 5Mpa, determine:

1) the radial inner wall
2) hoop stress inner wall
3) the radial outer wall
4) hoop stress outer wall
5) longitudinal stress in the cylinder wall

firstly, i would work out the longitudinal stress using lame's constant stress for A

a = σL = (P1(R1²)) - (P1(R2²))
(R2²) - (R1²)

a = σL = ((20x10^6(0.03²)) - (5X10^6(0.05²))
(0.05²) - (0.03²)
= 5500/0.0016
=3.44Nm² ....are these units correct?

how do yout work out the hoop/radial stresses?