| 研究課題/領域番号 |
19F19730
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| 研究種目 |
特別研究員奨励費
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| 配分区分 | 補助金 |
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| 応募区分 | 外国 |
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| 審査区分 |
小区分18010:材料力学および機械材料関連
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| 研究機関 | 九州大学 |
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研究代表者 |
陳 強 九州大学, 工学研究院, 教授 (30264451)
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| 研究分担者 |
YANG KUN 九州大学, 工学(系)研究科(研究院), 外国人特別研究員
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| 研究期間 (年度) |
2019-07-24 – 2021-03-31
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| 研究課題ステータス |
完了 (2020年度)
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| 配分額 *注記 |
2,300千円 (直接経費: 2,300千円)
2020年度: 1,100千円 (直接経費: 1,100千円)
2019年度: 1,200千円 (直接経費: 1,200千円)
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| キーワード | Titanium Alloy / Ultra-High Cycle Fatigue / Crack Initiation / Crack Growth / Bimodal Structure / Fatigue / Titanium Alloys / Bimodal Microstructure / Ultrasonic Fatigue |
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| 研究開始時の研究の概要 |
In the current research, we will investigate very high cycle fatigue strength and fracture mechanism of Titanium alloys that have found increasing structural applications to secure reliability design and ultra-long fatigue lives. The initiation mechanism and ultra-slow crack growth behavior will be deeply studied.
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| 研究実績の概要 |
In ultra-high cycle fatigue failure, ultra-slow crack growth of small cracks has great contribution to fatigue life. Micron-sized notches were prefabricated on the specimen surface by focused ion beam (FIB) technology. Ultrasonic fatigue tests (20 kHz) were suspended at specific life intervals and field emission scanning electron microscope (SEM) was used to carefully observe the fatigue crack growth behavior at end of the notches. Two types of bimodal microstructures and different cyclic stress amplitudes were employed to investigate the ultra-slow crack growth behavior of the alloys. The path of small fatigue cracks is relatively straight at the primary alpha grain, whilst it is more tortuous at the colony. The colony has a higher resistant to the growth of small fatigue cracks than the primary alpha grain in the bimodal microstructure. If small fatigue cracks pass through very few colonies, fatigue crack growth rate will be higher, even if a lower cyclic stress was applied. Owing to the difference in local microstructure characteristics, the growth rate data of small fatigue cracks show obvious dispersity. The higher volume fraction of colonies should be beneficial to improve the growth resistance of small fatigue cracks. In addition, we also found that deformation twins that were induced by the laser shock peening, can retard the growth of small fatigue cracks. These results may provide insightful ideas for the anti-fatigue microstructure design of titanium alloys.
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| 現在までの達成度 (段落) |
令和2年度が最終年度であるため、記入しない。
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| 今後の研究の推進方策 |
令和2年度が最終年度であるため、記入しない。
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