炭素鋼の回転曲げ疲労強度に及ぼす周期的引張大荷重の影響

概要

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In the two previous papers, the authors discussed the effect of a single high tensile load applied prior to stress cycling or during stress cycling on fatigue strength. In the present study, the effect of periodic high tensile loads on the rotating bending fatigue strength of 0.33% carbon steel were investigated. The main conclusions obtained are summarized as follows : (1) In the case of the high tensile load (σ_H=39.5kg/mm^2 corresponding to the lower yield point of virgin specimen, the S-N curve bends slightly to the side of shorter life at the stress near the fatigue limit of virgin specimen. (2) In the case of the high tensile load (σ_H=60.0kg/mm^2 corresponding to 8.7% true strain of virgin specimen, the fatigue life is shorter than that of (σ_H=39.5kg/mm^2 and the S-N curve bends abruptly to the side of shorter life at the stress near the fatigue limit of virgin specimen. (3) The effects of frequency and sequence of high tensile loads are not found. (4) In the case of the high tensile load aH=39.5kg/mm^2, the fracture surface of specimens exhibits fatigue fracture surface, while in the case of aH=60.0kg/mm^2 it shows fatigue fracture surface above the S-N diagram's nose but local contraction fracture surface below that point. (5) In most cases the values of the cumulative cycle ratio are very small.
社団法人日本材料学会の論文
1977-07-15