Analysis on cyclic deformation and low-high-cycle fatigue in uniaxial stress state

Having analyzed the hysteresis loop of plastic, the authors have formulated the evolution equations for three types of backstresses which are responsible for the shift of yield surface; and based on them the equations of the theory of plastic flow under combined hardening have been formulated. By integrating the evolution equation for the backstresses of the second type under rigid symmetric cyclic loading with a constant magnitude of plastic deformation in uniaxial stress state,we have obtained the expressions for the backstresses on the first half cycle and a stable maximum and minimum values of backstresses. After it, we have examined the work of backstresses of the second type on the field of plastic deformations; andbased on the experimental dataitis shown that the value of this work is a constant feature of fracture in the conditions of low-high-cycle fatigue (from 101 to 106 cycles). Based on these results we formulatedthelow-high cycle fatiguecriterion. Its asymptotes at a small and large number of cycles beforefailure have been obtained. The computational and experimental results for fatigue have been compared. The computational and experimental behavior of the accumulated plastic strain underlow-high-cycle fatigue has been analyzed. Kinetic equation of damage accumulation describing the nonlinear process of damage accumulation has been formulated based on the analysis of experimental data with regard to damageaccumulation under cyclic loadings.A comparison of the calculated and experimental results in multi-block cyclic loading is considered. The ratcheting and landing processes with respect to plastic hysteresis loops under asymmetric cyclic loading have been analyzed as well as a parameter and its functional relationship to describe these processes have been determined. Thecomputational and experimental research results of processes in soft and hard asymmetrical cyclic loadings have been compared.