研究者詳細 - 坂本　惇司

In this study, we propose a method for assessing the applicability of an artificial defect as a small initial crack for fatigue limit evaluation. The proposed method is applied to drill holes and sharp notches introduced using a focused ion beam (FIB) technique in annealed 0.45% carbon steel. It is found that under rotating bending fatigue, an FIB notch can be used as a small initial crack for fatigue limit evaluation, whereas a drill hole cannot, for of ∼50 μm. Here, is the square root of the area obtained by projecting the defect onto a plane perpendicular to the load axial direction. The results indicate that an FIB notch can be used as a small initial crack for fatigue limit evaluation in a greater number of materials than those in which a drill hole can be used.

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その他リンク： http://orcid.org/0000-0002-2108-2258

FIB加工による人工欠陥を有するS45C焼鈍し材の微小疲労き裂進展挙動

坂本惇司, 高橋可昌, 野口博司

日本機械学会M&M材料力学カンファレンス(CD-ROM) 2011年

Effect of gaseous hydrogen on cyclic slip behavior around a stage i fatigue crack tip in an iron alloy

Takahashi Y, Sakamoto J, Tanaka M, Higashida K, Noguchi H

18th European Conference on Fracture: Fracture of Materials and Structures from Micro to Macro Scale 2010年12月1日

In order to investigate the effect of gaseous hydrogen on cyclic slip behavior around an early stage (stage Ifatigue crack tip, fatigue crack growth (FCGtests using a single-crystalline Fe-3.2wt.%Si alloy are conducted respectively in a hydrogen atmosphere and in a helium atmosphere. The cross-sectional observations of the crack tips by both electron backscatter diffraction (EBSDmethod and transmission electron microscopy (TEMsuccessfully reveal the following points. In helium atmosphere, FCG is preceded by formation of cell structures and crack propagates along cell boundaries. In hydrogen atmosphere, on the other hand, no cells are seen, and crack growth process is similar to that observed in a stage II type FCG. Crack extension resistance in hydrogen is postulated to be lower than that in helium, indicating that the mode of FCG in hydrogen is more critical than that in helium.

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その他リンク： http://orcid.org/0000-0002-2108-2258

透過型電子顕微鏡による傾斜疲労き裂先端の微視的すべり挙動におよぼす水素の影響解析

坂本惇司, 高橋可昌, 田中將己, 東田賢二, 野口博司

日本材料学会学術講演会講演論文集 2010年5月21日

フレッティング疲労強度向上のための応力逃がし溝形状の最適化

坂本惇司, 近藤良之, 久保田祐信

日本機械学会年次大会講演論文集 2009年9月12日

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