NUMERICAL MODELING OF THE FATIGUE LIFE OF STRUCTURAL STEELS UNDER SINGLE-FREQUENCY AND DUAL-FREQUENCY LOADING

In this article, the elastoplastic behavior and resource characteristics for structural materials widely used in industry under fatigue single-frequency and dual-frequency loading is investigated. Amathematical model of the mechanics of a damaged medium has been developed, which makes it possible to model the elastoplastic behavior and determine the resource characteristics for structural materials under fatigue loading. The processes of low-cycle and high-cycle fatigue are considered. The model is based on the joint integration of equations describing the kinetics of the stress-strain state and damage accumulation processes. The closing ratio is the strength criterion, the fulfillment of which corresponds to the formation of a macrocrack.The plasticity equations are based on the basic principles of the flow theory. The relationships that simulate the accumulation of damage are based on the energy approach to determining the resource characteristics. The kinetics of fatigue damage accumulation is based on the introduction of a scalar parameter of damage to a structural material and a unified energy form of representing the degradation mechanism under low-cycle and high-cycle loading. Based on the proposed mathematical model of the mechanics of a damaged medium, numerical studies of the kinetics of the stress-strain state and fracture of polycrystalline materials – steels 20 and 08Х18Н12Т under conditions of single-frequency and two-frequency fatigue loading are carried out. The results of the reliability assessment showed that the developed model describes the low-cycle and high-cycle fatigue processes with a high degree of accuracy.