北海道大学 · 工学
Takashi Nakamura教授の研究室では、高強度鋼の超高サイクル疲労（VHCF）における亀裂の発生と成長挙動を、放射線を用いた非破壊観察技術（特にSPring-8のシンチロトロン放射線マイクロCT）を駆使して解明しています。特に、表面ではなく内部から発生する亀裂と、その特徴的な「ODA」（凹凸模様）と呼ばれる破壊面の形成機構に注目しており、材料の安全性向上に貢献する基礎的知見の確立を目指しています。
Figures are computed from collected data and may differ slightly.
Very high cycle fatigue (VHCF) of high strength steel has become an important issue for mechanical engineers in recent years. In VHCF regime over 107 cycles, fatigue crack initiates not from surface but from sub-surface of materials. The sub-surface fractures even occur in a lower stress than surface-originating fractures; therefore, to clarify its mechanism is strongly needed for the safety use of high strength steel. In sub-surface fractures, a typical fracture surface with a fine concavo-conv
Abstract Small internal fatigue cracks initiated in Ti‐6Al‐4V in the very high cycle regime were detected by synchrotron radiation microcomputed tomography (SR‐μCT) at SPring‐8 in Japan. The initiation and growth behaviours of the cracks were nondestructively observed, and the da/dN ‐ ΔK relationship was measured and compared with that obtained in a high vacuum environment. SR‐μCT revealed that more than 20 cracks were initiated in one specimen. The crack initiation life varied widely from 20% t
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