Diagraming of Fatigue Strength and Interpretation of Notch Effect Based on the Equivalent Stress Ratio

Abstract

Based on an equivalent stress ratio R_<EQ> which was previously proposed as a parameter for correspondence between the cyclic stress conditions of notched and unnotched specimens, the fatigue strength concerning axial, bending, torsional and their combination loading is rearranged on the diagram where the abscissa indicates R_<EQ> and the ordinate indicates the notch-root-concentrated stress range (Δσ_<NR.w1>). As a result, it is found that the diagram is consistent in spite of differences of stress concentration factors and loading types. Moreover, the notch sensitivity of material is discussed on the basis of the diagrams.