Stress creep and stress relaxation in the case of loading and unloading of a cylindrical layer with allowance for the development and deceleration of a viscoplastic flow

The theory of large deformations is used to solve a problem of an elastic-viscoplastic material placed in a gap between two coaxial cylindrical surfaces, with one of them rotating with an alternating velocity and the other one at rest. It is shown that an increase in the stresses in a cylindrical layer due to a mechanical influence on it initially causes irreversible creep strains because of viscosity of the material and then the accumulation of plastic strains because of the arrival of stress states at the loading surface. The unloading is accompanied by a plastic strain and then a viscous one. The stress-strain parameters of the medium with a varying rotation velocity of the cylinder are calculated. Stress relaxation after its complete stop is described.