Damage accumulation in cyclically stable steel under low-cycle loading and elevated temperature

Abstract

Abstract Based on the strain-kinetic fatigue fracture criterion, the kinetics of accumulated damages in structural carbon steel under low-cycle loading at an elevated temperature (150°C), at which the material begins to develop stress aging processes, is estimated. It is shown that stress aging, strengthening the material, narrows the durability area in which there is quasistatic destruction, the limiting case of which is the buckling failure of plastic strain, like single static destruction. This increases the fatigue fracture range, the limiting case of which is the formation of the primary fracture. The recoverable plastic strain causes the main damaging effect. Stress aging contributes to an increase in damage from elastic strain, although in the area of low-cycle failure, the share of damage from elastic strain remains small, growing with increased durability, and in the area of multi-cycle fatigue, this share becomes prevalent. Hardening from stress aging inhibits the development of damage from the one-way accumulated strain. The author confirms the validity of applying the strain-kinetic criterion of fatigue fracture to describe the damage kinetics and limit states during the cyclic elastic-plastic strain of carbon steel in the presence of weak stress aging.