The fatigue properties and the cyclic stress-strain response of SCM4 steel are investigated under strain controlled tests.
It was observed that quench-tempered SCM4 steel cyclically softened at all the strain levels tested. Shapes of hysteresis loops cyclically change at each constant strain level. Cyclic hardening exponent and cyclic strength coefficient of stable hysteresis loop decreases as the strain amplitude level becomes higher. Using the concept of useful life, $N_R$, fatigue life equations are obtained. Experimental parameters of cyclic stress-strain curve are obtained by several methods. The value of the cyclic hardening exponent which is derived from two fatigue life equations is reasonable when plastic strain amplitude and elastic strain amplitude are of the same order. It was found that Lo-Hi sequence test was in good agreement with linear damage rule, while Hi-Lo sequence test was not in good agreement.