Version of the theory of thermoplasticity

The paper explains the basic concepts and equations of the theory of thermoplasticity belonging to the class of theories of plastic flow in the combined hardening. The tensor strain rate is represented as a sum of tensors of the velocities of elastic and plastic deformations. The elastic deformation follows the generalized Hooke's law distributed to non-isothermal loading. The surface loading is introduced which isotropically widens or narrows and shifts in the process of loading. For the radius of the surface loading the authors formulated evolutionary equation taking into account the additional isotropic hardening under non-proportional loading, also generalized to non-isothermal loading. We have taken the parameter of Kadashevich-Mosolova corresponding to the angle between the velocity vectors of strain and stress as the parameter characterizing the degree of complexity of the process of loading. Surface displacement loading is described based on the model of Novozhilov-Chaboche implying that the total displacement is the sum of the displacements and each displacement has its own evolutionary equation. An earlier analysis of a loop of plastic hysteresis allowed distinguishing three types of micro-strains (displacements) and formulating three types of evolution equations. Here these evolutionary equations are generalized to the non-isothermal loading. To determine the axial velocity of plastic deformation we used associate (gradient) flow law. It became possible to determine expressions for speed of the accumulated plastic strain for hard and soft modes of loading. The authors have formulated conditions of elastic and elastic-plastic conditions. The kinetic equation of damage accumulation is introduced for the description of nonlinear processes of damage accumulation. Here, energies equal to the work of microstresses of the first and second types to the field of plastic deformations are accepted as the energy spent on creating damage in the material. These equations are generalized to the non-isothermal loading. We have highlighted material options completing theory option, formulated the basic experiment and the method of identifying material functions. The paper describes the verification of thermoplasticity theory on a wide range of structural steels and alloys and programs of experimental studies. New results have adequate descriptions within one theory of the following phenomena: - landing loop of plastic hysteresis in nonsymmetrical rigid cyclic loading; - ratcheting of loop plastic hysteresis in nonsymmetrical soft cyclic loading; - the regularities of complex loading as on planar or spatial trajectories; - the effects of additional isotropic hardening under disproportionate (complex) cyclic loading; - the effects of non-linear summation of damage to arbitrary loading processes; - the patterns of non-isothermal loading.