慶應義塾大学 · 工学
Hayama教授の研究室では、表面処理技術が金属材料の疲労特性に与える影響を、X線回折を用いた在来式応力測定法を駆使して解明しています。特に、フェニッシュ処理によって発生する圧縮残留応力の疲労循環による緩和挙動や、炭素拡散処理鋼における保持オースナイトの相変態と応力状態の関係を詳細に分析しています。材料の耐久性向上に不可欠な残留応力の安定性とその制御法の解明が、主な研究の方向性です。
Figures are computed from collected data and may differ slightly.
To clarify the relaxation behavior of compressive residual stress during the first push and pull loading cycle, an in situ X-ray stress measurement method was formulated, in which a fine particle peening-treated hourglass-shaped specimen was fixed on an axial-loading fatigue testing machine, and the surface stress of the specimen—which is the sum of applied stress and residual stress—was directly measured via X-ray diffraction without removing the specimen from the testing machine. A noticeable
The transformation behavior of retained austenite in carburized SCM420H steel and its effect on the change in residual stress on a surface are investigated. The retained austenite on the carburized steel is transformed significantly in the first cycle of fatigue loading with a stress ratio of -1, and the transformation is less significant thereafter. Tensile loading significantly affects the transformation of retained austenite as compared with compressive loading. This is because the mechanical
The transformation behavior of retained austenite in carburized SCM420H steel and its effect on the change in residual stress on a surface are investigated. The retained austenite on the carburized steel is transformed significantly in the first cycle of fatigue loading with a stress ratio of −1, and the transformation is less significant thereafter. Tensile loading significantly affects the transformation of retained austenite as compared with compressive loading. This is because the mechanical
To clarify the relaxation behavior of compressive residual stress during the first push and pull loading cycle, an in situ X-ray stress measurement method was formulated, in which a fine particle peening-treated hourglass-shaped specimen was fixed on an axial-loading fatigue testing machine, and the surface stress of the specimen—which is the sum of applied stress and residual stress—was directly measured via X-ray diffraction without removing the specimen from the testing machine. A noticeable
The difference of the effects of residual stress and stress ratio on fatigue properties of S45C steel was examined. Two types of specimens were prepared, one is polished to mirror finish (P series) and the other is treated by fine particle peening (FPP series). The residual stress of the specimens was measured by X-ray diffraction residual stress measurement system. The surface roughness of the specimens was measured by a laser microscope. FPP series exhibited higher compressive residual stress
Compressive residual stress formed by fine particle peening improves the fatigue properties of steel. However, it is relaxed during the fatigue process particularly during the first cycle of fatigue because of the compressive residual stress layer yield. In this study, the compressive residual stress was induced for specimens with different yield strength by fine particle peening, and the residual stress relaxation behavior was measured and compared using in situ X-ray stress measurement. The re
The formation of a compressive residual stress layer on surfaces improves the fatigue properties of steel. However, compressive residual stress relaxation occurs during the fatigue process, necessitating the examination of this behavior. Herein, an on-site residual stress measurement system that can measure the residual stress under various load conditions was built. The load was changed in a stepwise manner and the residual stress was measured at each step to investigate compressive residual st
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