| Project/Area Number |
16K05980
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Fukuoka University (2018)
Kyushu University (2016-2017) |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
藤川 正毅 琉球大学, 工学部, 助教 (70549047)
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Project Status |
Completed (Fiscal Year 2018)
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| Budget Amount *help |
¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000)
Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2017: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2016: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
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| Keywords | 疲労き裂進展 / 水素拡散 / 有限要素法 / 水素 / 環境強度 / 鉄鋼材料 / 疲労 |
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| Outline of Final Research Achievements |
Fatigue crack growth (FCG) tests of an annealed, low-carbon steel, JIS-SM490B, were performed under various combinations of hydrogen pressures, test frequencies, and test temperatures. The FCG rate was hardly dependent on the hydrogen-gas pressure. In contrast, in certain conditions, the FCG rate increased with a decrease in the test frequency; then, peaked out. In the lower test frequency regime, the FCG rate decreased and became nearly equivalent to the FCG rate in air. The stress intensity factor range, ΔK, for the onset of the FCG acceleration in hydrogen gas was shifted to a higher ΔK with an increase in the test temperature. Hydrogen diffusion / Elastoplastic coupling analysis in a commercial finite element method (FEM) software Abaqus was conducted and revealed that the onset and ratio of FCG acceleration could be predicted by using two novel parameters: a gradient of hydrogen concentration near a crack tip and an effective diffusion depth based on its gradient, respectively.
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| Academic Significance and Societal Importance of the Research Achievements |
従来の水素脆化の研究の多くは，電気化学的に水素チャージを実施するため，高温での試験が困難である．また，数少ない高温水素ガスを用いた研究も，水素に極めて敏感な高強度鋼を対象としており，社会に波及するような実用的な研究ではない．これに対して，本研究では実用鋼を対象とし，高温水素ガス中での水素脆化挙動を明らかにするとともに，これまで報告されていない独創的な発想である局所パラメータを用いて水素脆化を定量的に評価することに成功している．さらに，高温水素ガスにおける研究成果は，今後の技術として期待される水素発電など，種々の水素機器の強度設計に展開できるという点で，学術的および社会的意義は大きいといえる．
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