The dynamics of cyclic plastic deformation and fatigue life of low carbon steel at low temperatures

Abstract

The cyclic plastic stress-strain response and fatigue life of a low carbon steel at low temperatures was studied. The cyclic hardening/softening curves and cyclic stress-strain curves at different temperatures were measured. Two components contributing to the cyclic flow stress were resolved, i.e., the internal stress and the effective stress. The effective stress component was found to be strongly dependent on the temperature and independent of the strain amplitude. The internal stress component was found to be dependent on the plastic strain amplitude and nearly independent of temperature. An analytical form of the cyclic stress-strain curve suitable for the analysis of the temperature and strain rate dependence of the cyclic plastic stress-strain response is proposed. The Manson-Coffin curves were found to be independent of temperature down to 113 K. A tendency to lowering the fatigue life was observed at the lowest temperature and highest strain amplitude only, and was connected with the appearance of brittle fracture, originated from short fatigue cracks.