Damage accumulation and limit states under the low-cycle loading of structural softening steel

Abstract

Determination and study of patterns of deformation and fracture of structural materials under cyclic loading is an important fundamental scientific problem. The kinetics of damage accumulation in softening TC (12Kh2MFA) structural steel under low-cycle loading is investigated in the paper based on the unified strain-kinetic criterion of fatigue fracture developed by the author. The damaging role of plastic and elastic strain depending on the loading (durability) is shown. Limit states and peculiarities of their occurrence during static, quasi-static, and fatigue failure are described. The force and deformation parameters determining the load-bearing capacity of the material and the nature of its exhaustion under static and cyclic loading have been established. The critical values of deformation and strength characteristics of steel under soft and hard loading are obtained. It is noted that it is reasonable to use these characteristics when modeling the stress–strain states. A method for determining the cyclic behavior of the material (hardening, softening, stabilization) by static fracture curves is proposed. The possibility of describing the kinetics of damage accumulation and limit states of softening materials by the strain-kinetic criterion of fatigue fracture is confirmed.