| Project/Area Number |
16K06815
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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 |
Metal making/Resorce production engineering
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| Research Institution | Tokyo City University |
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Principal Investigator |
Shiraki Naoto 東京都市大学, 工学部, 教授 (20298011)
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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 |
¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
Fiscal Year 2018: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000)
Fiscal Year 2017: ¥260,000 (Direct Cost: ¥200,000、Indirect Cost: ¥60,000)
Fiscal Year 2016: ¥1,820,000 (Direct Cost: ¥1,400,000、Indirect Cost: ¥420,000)
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| Keywords | X線CT / 球状黒鉛鋳鉄鋳鉄 / 疲労限度 / 欠陥寸法 / 破壊起点 / Ｘ線ＣＴ / 球状黒鉛鋳鉄 / Ｘ線CT / 疲労試験 / 推定 / 極値確率紙 / X線CT装置 / 欠陥 / 集合黒鉛 / 引け巣 |
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| Outline of Final Research Achievements |
Axial load fatigue specimen were cut out from a large ingot of spheroidal graphite cast iron equivalent to FCD 350, and high resolution X-ray CT was used for all specimen to detect internal graphite and defects in the material. The fatigue limit was estimated using the dimensions of graphite and defects and the fatigue limit estimation equation. As a result, the fatigue limit estimated by the defect size of the defect with the largest volume detected by X-ray CT was a safety side with an error of 5% with respect to the fatigue limit of 125 MPa obtained by the experiment. It is an estimation of the danger side with an error of 11% with respect to the fatigue limit obtained by the experiment. From these results, it is judged that estimation of fatigue strength by nondestructive testing is possible.
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| Academic Significance and Societal Importance of the Research Achievements |
一般に鉄鋼材料の疲労限度は，引張強さの1/2又はビッカース硬さHVの1.6倍といわれているが，球状黒鉛鋳鉄の様に材料中に大きな欠陥が存在する場合，引張強さのみでは評価できない場合がある．欠陥を矩形近似し，その面積平方根を√areaとし，基地組織のビッカース硬さを考慮することで疲労限度を高い精度で推定できる推定式が提案されている．一方，鋳造品に内在する欠陥の検出は，高精度のX線CTで内在する欠陥を検出することが可能で，同様の手法で疲労限度を非破壊的に予測できる可能性をしめした．本手法は疲労試験を行うことなく球状黒鉛鋳鉄を構造材料として用いるための実用的な疲労強度評価方法となり得ることを示した．
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