Rod torsion in kinematic creep regimes

Problems are considered that describe the process of obtaining the residual angle of twist of a rod under creep conditions, taking into account elastic recovery after unloading. It is assumed that a constant linear angle of twist is set for the section being formed, i.e., the section is in conditions of pure torsion, without constraining the ends of the rod. It is believed that strains and stresses depend only on time and two spatial coordinates in the plane of the cross section of the rod. Direct and inverse problems of torsion of a rod with rectangular and angular cross sections in various kinematic creep regimes are considered. The speed of the angle of twist during the entire deformation process is set constant. A method of numerical calculation based on the finite element method is proposed, which makes it possible to obtain the stiffness characteristics of the section under torsion in the case of creep. It is shown that the minimum level of residual stresses is observed in the relaxation mode of deformation. For a rod with a cross-section of the angular type, modes are found in which stresses significantly decrease in the area of their concentration.