OS4-8-6 Characteristics of Fatigue Strength Diagrams Represented by Equivalent Stress Ratios

Abstract

In the previous study, equivalent stress ratios were proposed as parameters for correspondence between fatigue test conditions of notched and unnotched specimens. Diagraming the relations between equivalent stress ratios and notch root stress ranges for fatigue limits and fatigue life strength, the relations proper to materials could be represented by consistent curves in spite of the difference of specimen types (plates and round-bars), loading types (axial, bending, torsional and their combined loading) and stress concentration factors of notches. In other words, it can be said that the relations diagramed by the equivalent stress ratios vs. notch root stress ranges for fatigue limits and fatigue life strength represent the characteristics on fatigue limits and fatigue life strength of unnotched specimens just as they are. In the present study, experimental data on fatigue strength of notched and unnotched specimens are widely picked up from literature and rearranged on the diagrams of equivalent stress ratios vs. notch root stress ranges. As a result, fatigue strength diagrams are categorized into three groups in accordance with fatigue processes and their characteristics are discussed.