Synergetic Principles and Regularities of Materials Fracture under Low-Cycle Fatigue Conditions

This work discusses the synergetic principles of fatigue failure, which allow for the identification of fundamental mechanical characteristics of materials and the assessment of damage kinetics during metal failure through critical parameters that control bifurcation points. Fatigue failure herewith is considered as a kinetic process dependent on the order of energy input from cyclic loading. Based on the principles of physical mesomechanics and synergetics, it is shown that the mechanical characteristics of cyclically loaded tribocontacts are important material parameters that determine the level of deformation energy introduced in each loading cycle at every scale. It has been identified that in tribocontacts, for practical purposes, it is necessary to ensure that the stress between the coating and the substrate corresponds to the ultimate elasticity of the materials, according to Griffith’s criterion, while for viscous materials, a different value of critical stress is taken into account: Irwin–Orawan modification. Criteria for transitional contact modes are presented, considering that the coating should undergo changes in full accordance with the substrate when the system is deformed under cyclic loading. The results of the research on assessing the mechanical characteristics of materials in the “coating–substrate” system can be used as diagnostic indicators when analyzing the development of damage in tribocontacts operating under conditions of cyclic fatigue loading.