2040 等価応力比にもとづく金属材料疲労強度の新しい整理法 : 疲労強度線図の分類と特性(S11-3 表面処理・応力比等の影響,S11 金属材料の超高サイクル疲労特性の解明)

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 at fatigue 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, the relations diagramed by the equivalent stress ratios vs. notch root stress ranges at fatigue strength represent the characteristics on fatigue strength of unnotched specimens. 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.