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))

therefore(R2²) - (R1²)

a = σL =((20x10^6(0.03²)) - (5X10^6(0.05²))

= 5500/0.0016(0.05²) - (0.03²)

=3.44Nm² ....are these units correct?

how do yout work out the hoop/radial stresses?