МАЛОЦИКЛОВАЯ УСТАЛОСТЬ ОБРАЗЦОВ С КОЛЬЦЕВОЙ ВЫТОЧКОЙ ПРИ ЖЕСТКОМ НАГРУЖЕНИИ

Abstract

The results of tests of cylindrical specimens of alloy 01570C for low-cycle fatigue are presented. The tests were carried out on a smooth sample and samples with an annular recess. Specimens with an annular groove were tested under rigid cyclic alternating loading with a constant range of elongation of the working part. To simulate the experiments performed, a variant of the plasticity model based on the theory of flow under combined hardening is used. In the chosen mathematical model, a memory surface is introduced that separates monotonous and cyclic loading. This division allows one to take into account various features of isotropic and anisotropic hardening of the material. Anisotropic hardening is described by the sum of backstresses of three different types, which make it possible to describe the effects of fitting and stepping out of the elastoplastic hysteresis loop. The plasticity model makes it possible to assess the damaged state of a material using an equation that describes the process of damage accumulation based on the energy criterion of durability. According to the results of testing a smooth sample, the parameters of the plasticity model were determined. The finite element method was used to carry out mathematical modeling of experiments on loading samples with an annular groove. The material behavior model was implemented in the SIMULIA Abaqus software package, for which the model equations were linearized and the Jacobi matrix was calculated, which determines the change in each of the stress increment components caused by an infinitesimal change in each component of the strain increment tensor. Based on the results of mathematical modeling, the dependences of the load applied to the sample on the elongation of its working part were obtained. The article compares the dependences of the load applied to the sample, obtained from the results of the calculation, with the experimental ones, as well as the number of cycles until the destruction of the sample.