日本機械学会論文集
Online ISSN : 2187-9761
ISSN-L : 2187-9761
材料力学,機械材料,材料加工
円周切欠きを有する丸棒試験片におけるひずみ速度集中係数の提案と応力集中係数の関係についての考察
野田 尚昭赤木 大地沈 雨濃高木 怜池田 朋弘佐野 義一高瀬 康
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2017 年 83 巻 851 号 p. 17-00034

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High-speed tensile testing is now being recognized as a standard testing method for evaluating the impact strength of engineering materials. The impact speeds of Izod and Charpy tests cannot be controlled and therefore do not correspond to the real failure of real products. The brittle-ductile transition of structural materials is affected by the temperature and loading speed. In the high-speed tensile test, it is necessary to obtain the strain rate at the notch root accurately to understand the effect of impact load. For smooth specimens, the strain rate can be determined from the tensile speed u/t and specimen length l as εsmooth = u/tl. For notched specimens, however, the strain rate at the notch root εnotch should be analyzed accurately. In this study, therefore, the strain rate concentration factor defined as K = εnotch/εsmooth is studied with varying the notch geometry. To predict the strain rate concentration factor K accurately, the relationship between K and the stress concentration factor Kt* = σmax/σgross is investigated. Here, σgross is the remote tensile stress and P is the tensile load. It is found that the strain concentration factor K can be estimeted from stress concentration factor Kt* when the relative notch depth 2t/D≦0.5 (t : notch depth, D : the specimen diameter).

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