Fatigue Limit Diagram of a Mild Steel under repeating Tension-compression with Tensile Static Stresses

Among many experimental results of fatigue limits of various materials under repeating tension-compression stresses, we find few reports under plastic tensile region in steels. Then we shall need more detailed experiments in this region for the research of fatigue phenomena or condition of fatigue rupture. This report state my experiments of mild steel specimens of the value of notch factor 1.4,tested by Nishihara's t esting machine under above mentioned stresses. The essential result of this experiment is that the characteristic line of fatigue limit in the diagram of repeating stress amplitude against mean tensile stress has been formed of curve and straight lines in each elastic, plastic and rupture region. The Fatigue limit and the diagram of un-notched specimen which can be deduced from this experiment by multiplying the notch factor βk, shall be compared with the fatigue limit calculated from the equation (1).