Variation of Fatigue Notch Factor With Lifetime, Stress Ratio and Temperature

Abstract

An understanding of the influence of various loading parameters on the fatigue notch factor Kf is important to the designer, who often relies exclusively on the limited fatigue data available in handbooks. The significance and limitations of Kf values so obtained are discussed in the light of geometry, fatigue lifetime, stress ratio, and temperature. Ultimately fatigue notch factor data in the literature are very limited, and often there is no recourse but to make use of the theoretical stress concentration factor Kt. The results of this procedure are usually very conservative. Handbook fatigue failure data were reexamined in order to determine the variation of Kf for a representative range of materials, including aluminum, steel, titanium and nickel alloys. Results are presented in the form of Kf over a wide range of notch and loading conditions. The results are interpreted and generalized in terms of stress concentration, and material mechanical and microstructural response.