Plastic and creep deformations of thick-walled cylinder with a rigid casing under internal pressure

The creep and plastic flow of cylindrical pressurized vessel with rigid casing was considered. To combine creep and plastic deformations the vessel was heated and subjected to the high inner pressure. The semi-analytical solution for plain strain problem of a thick-walled cylinder with rigid casing in the frame of small strain theory was obtained in this paper. This solution consists of analytical formula for displacement distribution with asking values of pressure and irreversible strains (plastic and creep) and a numerical solution for irreversible strain values. The Norton power law and advanced Mises condition for viscoplasticity, associated with flow rules have been used to describe creep and plastic behavior of medium.
Four stages of the deformation process were considered: pressure increasing, pressure fixed on maximum value for a long time, pressure decreasing and relaxing stage with zero pressure. Two cases of maximum pressure values of 200 MPa and 320 MPa were studied. An additional case of elastoplastic deformation was considered to investigate the influence of creep on the deformational process. It has been observed that creep has a significant influence on stress and strain evolution in medium, especially on stages with maximum and zero pressure. Also, because of the creep plastic flow evolves slower and stoppes earlier on the loading stage. In the unloading stage, the plastic flow starts earlier and affects greater area due to greater irreversible strains. Creep leads to sufficient stress relaxation and stresses for two pressure cases get similar values at the end of the stage with maximum pressure value. At the end of the relaxing stage besides stresses displacement and deformation also became similar for the two cases.