A New Method for Diagramming Fatigue Strength of MetalsBased on the Equivalent Stress Ratio Parameter andCharacterization of Fatigue Strength Diagrams

摘要

In the present paper, equivalent stress ratios (REQ-ratios) which have been proposed asrnparameters for correspondence between cyclic stress conditions of notched and unnotched specimensrnare reviewed, and a method for diagramming fatigue strength of metals based on the parameter ofrnREQ-ratios is newly proposed. The relation between REQ-ratios and notch-root-concentrated stressrnranges at fatigue strength can be represented by a consistent curve in spite of difference of specimenrntypes (plates and round-bars), loading types (axial, bending, torsion and their combined loads) andrnstress concentration factors of notches. Accordingly, it can be thought that the relation diagrammedrnwith the REQ-ratio vs. notch-root-concentrated stress ranges at the fatigue strength represents thernintrinsic characteristics of material itself. Fatigue strength diagrams are characterized by two charactersrnof σw1 and σw2 . A proposed method for diagramming is applied to fatigue problems of heatandrnsurface-treated materials.