Effect of Mean Stress on Fatigue Strength of Carburized Steel

Abstract

Although it is known that the fatigue strength of carburized steel is greatly influenced by the residual stress on the surface, it is very difficult to assess the effect quantitatively. In this report, the effect of mean stress on the fatigue strength of carburized steel is studied, and therefrom the effect of residual stress can be estimated. Following results are obtained. (1) The fatigue strength of a high hardness and brittle steel, is more sensitive to mean stress, as compared to those of medium and low hardness steels. (2) As the Tempering temperature of carburized steel is increased, the effect of mean stress on the fatigue strength decreases. (3) During the fatigue test little change was observed in the residual stress and half value breadth of X-ray diffraction line of carburized steel. On the basis of these results, the mechanism of fatigue failure of carburized steel was discussed.