Thick Cylinders: Internal & External Pressures, Hoop & Radial Stresses

[tone999]

Homework Statement

A thick cylinder of 100mm internal radius and 150mm external radius is subjected to an internal pressure of 60MN/m^2 and an external pressure of 30MN/m^2. Determine the hoop and radial stresses at the inside and outside of the cylinder together with the longitudinal stress of the cylinder is assumed to have closed ends.

Homework Equations

radial stress = A - B/r^2

The Attempt at a Solution

Ok so we've got:

at r = 0.1m, radial stress = -60MN/m^2
at r = 0.15m, radial stress = -30MN/m^2

Therefore using the equation:
radial stress = A - B/r^2

we get -60 = A -100 B
-30 = A - 44.5 B

I don't know how they got the 100 and 44.5 here? Quite confused

 

[nvn]

at r = 0.10 m, radial stress = -60 MPa
at r = 0.15 m, radial stress = -30 MPa

That's right.

All your other equations appear to make no sense and are incorrect. You would need to post coherent relevant equations, and a coherent, valid attempt, in order to receive help.