1131 等価応力比法による鉄鋼材料の疲労強度線図の特性化と定式化に関する考察(OS11-7 材料の疲労挙動と損傷評価-疲労損傷・寿命予測-)

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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, (1) Accuracy-improved equations on fatigue strength are proposed for high stress ratios of cyclic stress conditions. (2) From fatigue strength data on notched specimens with very shallow notch-depths, size effect is examined and characterized. (3) The two type of fatigue strength equations, where size effect of notch is taken into consideration, are formulated on the basis of the above-mentioned conclusion (1).
2010-10-09