EFFECT OF PRE-STRAIN ON TORSIONAL FATIGUE PROPERTIES OF MIDDLE CARBON STEEL

Fatigue test was performed to investigate thereversed torsional fatigue properties of non-pre-strained carbon steel and three kinds ofpre-strained carbon steel. Main results summarized in this study are asfollows: In the case of pre-strain rate lower than 5\%, the fatigue limitis 10\% lower than the non-pre-strained specimen. In the case ofpre-strain rate higher than 5\%, the fatigue limit increases withincreasing pre-strain rate. For the pre-strain rate of 8\%, thefatigue limit is equal to the fatigue limit of non-pre-strained specimen. Thenon-propagatinig cracks are observed in all specimens' surfaces after1\times 10^7 cycles under the stress amplitude of fatigue limit.