| Project/Area Number |
17K14565
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Japan Atomic Energy Agency |
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Principal Investigator |
Naoe Takashi 国立研究開発法人日本原子力研究開発機構, 原子力科学研究部門 J－PARCセンター, 研究副主幹 (00469826)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2019: ¥520,000 (Direct Cost: ¥400,000、Indirect Cost: ¥120,000)
Fiscal Year 2018: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2017: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
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| Keywords | ギガサイクル疲労 / 超音波疲労試験 / 溶接 / 転位密度 / 中性子回折 / 機械材料・材料力学 / 転位 / 繰返し硬化 / き裂検出 |
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| Outline of Final Research Achievements |
As a fundamental study of the fatigue durability investigation and its diagnostic technique under high-cycle and high-strain rate loading, we have performed gigacycle fatigue test using an ultrasonic fatigue testing method aiming to focusing on metal structure change. Change in the dislocation density by cyclic loading up to gigacycle for austenitic stainless steel was evaluated through the neutron diffraction method. Change in the dislocation densities by cyclic loading were well-correlated with the change of the hardness and the residual strength.
Furthermore, the effect of the weld bead on the gigacycle fatigue was investigated. The fatigue strength of the removed weld bead specimen was greater than without weld specimen. By contrast, fatigue strength of the weld specimen with bead, wherein we estimated the stress amplitude while ignoring the bead shape, was obviously degrade degraded because of the stress concentration at the weld toe in comparison with removed bead specimen.
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| Academic Significance and Societal Importance of the Research Achievements |
オーステナイト系ステンレス鋼のギガサイクル疲労データは，報告例があるものの，溶接材及び溶接金属については調べられていない．溶接材のギガサイクル領域の疲労データを整備することは効率的な機器の設計や寿命評価のために重要である．また，ギガサイクル疲労過程における力学特性変化は報告例がなく，繰返し応力負荷により生じる硬化及び軟化減少と転位密度の変化を関連づけて評価することは学術的意義も高い．
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