An Explanation of the Fatigue Strengths of Strength-Anisotropic Steels

抄録

In this paper an idea to explain the features of the fatigue strength of strength-anisotropic steels is proposed. The underlying idea is that the incipient fatigue crack, developed near the surface of the specimen as a result of an occurrence of extrusions and intrusions due to fatigue stressing, spreads step by step by the cracking of the plastic zone at the root of the crack. The cracking is assumed to follow the Griffith's energy condition. The portion where the incipient crack appears differs from torsional to bending specimens, since the specimens have strength anisotropy. It is assumed that in twisted specimens a plane crack and in bent specimens a semi-circular crack propagates under the action of normal and shearing stresses. The expressions of fatigue strength obtained represent satisfactorily the experimental results made with carbon steels which are reported elsewhere¹⁰.