Viscoplastic deformation of granular nickel alloy at high temperatures

The viscoplastic deformation of a granular nickel alloy during isothermal rolling under high temperature conditions is considered. The stress state of the alloy during rolling is inhomogeneous and multiaxial during repeated deformation with a variable deformation rate. The diagrams of the viscoplastic deformation of the alloy at high temperatures and various deformation rates have a falling (softening) section up to destruction, which is due to a short-term creep during powerful softening. Mathematical modeling of the viscoplastic behavior of the alloy under such conditions is proposed to be carried out on the basis of a variant of the theory of thermoviscoplasticity based on the theory of flow under combined hardening. A variant of the theory of thermoviscoplasticity is generalized to non-isothermal loading and to dependence of the violation process on the deformation rate. The main provisions and equations of the variant of the theory of thermoviscoplasticity are presented. The material parameters that close the version of the theory, the basic experiment and the method of obtaining material parameters are determined. The material parameters of the granular nickel alloy at high temperatures and various deformation rates are obtained. The results of experiments on uniaxial stretching of cylindrical samples made of granular nickel alloy at high temperatures and different deformation rates are presented. Tests with unloading and subsequent loading are also considered. Mathematical modeling of tests of a granular nickel alloy is carried out on the basis of a numerical solution of the Cauchy problem by the Runge-Kutta method of the 4th order of accuracy of the system of equations for a uniaxial stress state under rigid loading obtained on the basis of general equations of a variant of the theory of thermoviscoplasticity. The obtained calculated diagrams of viscoplastic deformation are compared with experimental ones. There is a reliable correspondence between the calculated and experimental results, which indicates the adequacy of the developed version of the theory of thermoviscoplasticity and the method of identification of material parameters.