ПОСТРОЕНИЕ ПОВЕРХНОСТИ ПАМЯТИ ДЛЯ РАЗДЕЛЕНИЯ ПРОЦЕССОВ МОНОТОННЫХ И ЦИКЛИЧЕСКИХ НАГРУЖЕНИЙ

Abstract

Non-stationary and asymmetric processes of cyclic deformation are considered, which consist of a sequence of monotonic and cyclic loading modes, in which peculiar effects of landing and ratcheting of plastic hysteresis loops occur. Mathematical modeling of such processes of deformation and damage accumulation is based mainly on variants of plasticity theories belonging to the class of theories of plastic flow with combined (isotropic and anisotropic) hardening. In this paper, mathematical modeling of the processes of deformation and damage accumulation is based on a variant of the theory of plasticity – the Bondar model. Based on the analysis of the results of experimental studies of samples of stainless steel 12Х18Н10T under a rigid (controlled deformation) deformation process, which is a sequence of monotonic and cyclic loading modes, under conditions of uniaxial tension-compression at normal temperature, the features and differences in the processes of monotonic and cyclic loading are revealed. To describe these features and separate the processes of monotonic and cyclic loading modes in the theories of plastic flow with combined hardening, various variants of memory surfaces are introduced. An analysis of the results of experimental studies of stainless steel showed that in the space of the plastic strain tensor, the size of the memory surface is determined by the range of plastic strains, and the position of the center is determined by the values of average plastic strains under cyclic loading. Various variants of the memory surface are considered, their capabilities and disadvantages are identified, and proposed variant of the memory surface.To confirm the operability of proposed version of the memory surface, together with the equations of the Bondar plasticity model, the calculated and experimental results were compared and a reliable agreement was obtained between these results both in terms of the kinetics of the stress-strain state and in terms of the number of cycles to failure.