Strength, damage and failure of iron-carbon alloys subiected to cyclic plasticity

Abstract

Abstract The cyclic deformation behaviour, fracture mechanisms and damage accumulation in pure iron and mild steel have been studied in strain control at various temperatures and deformation rates. Explanations are offered for the effects of prior cold working, cyclic deformation rate and temperature, including combinations of these parameters, on the cyclic stress response, dislocation substructure, surface damage and fatigue fracture.It has been found that steady state cyclic deformation may be achieved by a critical amount of prior monotonic strain and the equivalence of monotonic and cyclic hardening processes is considered and supporting microstructural work is provided.The influence of cyclic deformation rate on the material behaviour is considered. At room temperature the stress response increases with increasing deformation rate and it is shown that the effective stress component is lower than the equivalent value for monotonic deformation, however, the dislocation velocity exponent is independent...