A cylindrical pressure vessel, with a diameter of 40cm and a wall thickness of 10mm is made of steel (isotropic, with Young's modulus = 200GPa; Poisson's ratio = 0.28) and is pressurized to 20MPa. The longitudinal and hoop stresses in the wall, σl and σh, respectively, are given by:
σl=pr/2t and σh=pr/t
What is the strain in the radial direction, through the thickness of the pressure vessel?