鋼材の平面曲げ疲労強度に及ぼす試験片形状の影響に関する研究 : 第2報

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It was found in the previous paper that ductility of steel plate under statical and dynamical bending loads was affected by shape of specimen, especially ratio of width to thickness of plate. In this paper, to investigate the effect of width to thickness ratio on the fatigue strength more precisely, reversed plane bending fatigue tests were carried out in intermediate cycle ranges. Specimens were mild steel plates of 6 mm thickness and width to thickness ratios were from 2 to 40. From the test results, the following conclusions were obtained. 1) State of strain distribution approaches to plane strain and range of the plane strain state extend to edges from center portion of plate with increase of width to thickness ratio. 2) Location of fatigue crack in transverse direction of plate is affected by width to thickness ratio, and the cracks initiate in center part of plate having the ratio larger than l0. 3) Fatigue crack initiation life is much more affected by the ratio than failure life. 4) For the fatigue life represented by the nominal bending stress, there is no distinct difference among all kinds of specimens.
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