Notch Effect of High Carbon Steel on the High Temperature Fatigue

Abstract

The authors already reported(11) the effect of the notch on the fatigue strength of the low carbon steel at the high temperature. On the low carbon steel it was indicated that at about 300°C the smooth specimen takes the highest fatigue strength, and as the notch becomes sharper, the temperature where the highest strength appears is gradually elevated. In this paper the same rotating bending fatigue tests were performed on the 0.72% C carbon steel, and the effects of the test temperature, the test speed and the notch sharpness on the fatigue strength and the notch factor were studied. The data indicate that on the high carbon steel also the temperature, where the increase of the fatigue strength occurrs based on the bluebrittleness, is elevated as the notch becomes sharper. At the high temperature the notch factor takes constant value when ακ>2, The notch factor is not so much effected on the high carbon steel as on the low carbon steel by the test speed and by the number of revolutions to fracture at the high temperature.