Microstructural evolution of strain rate related tensile elastic prestrain on the high-cycle fatigue in medium-carbon steel

Abstract

When engineered structures undergo regular cyclic loading processes, they would often be affected by extensional strain. To highlight the effect of tensile strain rate on subsequent fatigue damage in medium-carbon steel, predeformation was entirely controlled in the elastic regime with strain rates ranging from 10−5s−1 to 10−2s−1. Evolutionary response of sample temperature and peak cyclic strain, microstructures, internal fatigue initiation, fatigue propagation in samples fractured during tensile elastic prestrain (TEP)-HCF tests were studied. Our results revealed that compared with non-prestrained, the effect of TEP rate on fatigue life was non-monotonic and beneficial. Strain rate related TEP had fundamentally realized lattice structure reconstruction and transform in sliding mode, and overall slipping of lattice structure and free consumption of interface dislocations that resist fatigue crack propagation was key for the observed leap in fatigue strength.