circumferential strain

Dear All,

I require to calculate the circumferential strain of cylinder. consider a hollow cylinder as active element. a1 = inner radii b1 = outer radii E = Young's modulus v = Poisson ratio ec = circumferential strain

I require to obtain the circumferential strain in two different condition:

1. the inner pressure of cylinder is P and the outer pressure is 0

1. the inner pressure is 0 and the outer pressure is P

I can calculate stress components of cilynder such as radial and tangential and longitudinal stress in two above condition. what relation are there between thess stresses and circumferential strain.

Best, Aref.