| Project/Area Number |
63302024
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| Research Category |
Grant-in-Aid for Co-operative Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
機械材料工学
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| Research Institution | Osaka University |
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Principal Investigator |
OHJI Kiyotsugu Osaka University, Faculty of Engineering, Professor, 工学部, 教授 (20028939)
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| Co-Investigator(Kenkyū-buntansha) |
KUBO Shiro Osaka University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (20107139)
YOKOBORI Toshimitsu Jr. Tohoku University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (00124636)
YUUKI Ryoji University of Tokyo, Institute of Industrial Science, Associate Professor, 生産技術研究所, 助教授 (70114709)
OHTANI Ryuichi Kyoto University, Faculty of Engineering, Professor, 工学部, 教授 (50025946)
OKAZAKI Masakazu Nagaoka University, of Technology, Faculty of Engineering, Associate Professor, 工学部, 助教授 (00134974)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥8,400,000 (Direct Cost: ¥8,400,000)
Fiscal Year 1989: ¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 1988: ¥4,900,000 (Direct Cost: ¥4,900,000)
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| Keywords | High Temperature Strength / Creep Fatigue / Crack Growth / Fatigue Threshold / Small Crack / Surface Crack / Fracture Mechanics / クリープ・疲労 |
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| Research Abstract |
It was pointed out that the crack growth under creep fatigue conditions in some metallic materials was either purely time dependent or purely cycle dependent, and that the transition between these two modes were almost reversible. In this study this fundamental law of creepfatigue interaction effect in high temperature fatigue crack growth was examined for several metallic materials and several specimen configurations. The main results obtained are summarized as follows.
1. The hold time effect on crack growth rate was examined. The crack growth rate could be interpreted reasonably by the fundamental crack growth law. 2. The crack growth behavior of large surface cracks was coincident with that of through cracks. A numerical method was proposed for evaluating fracture mechanics parameters of surface cracks. 3. To investigate the character of high temperature fatigue threshold, crack growth experiments were made using two-step varying loads. It was found that cracks grew even under load ranges lower than the threshold value for constant amplitude conditions. The process of recovery of the threshold, and the effects of temperature and load frequency on this phenomenon was studied. 4. The interrelation of the high temperature strength of unidirectionally solidified alloys and the high temperature low-cycle crack growth behavior was examined. The effect of microstructure on the crack growth behavior was discussed. 5. The detailed observations of the behavior of small crack initiation and growth were made. Models of the small crack initiation and growth under creep fatigue conditions were proposed. Monte Carlo simulations showed that the proposed models were useful for understanding the behavior of small cracks. 6. A laser interferometry was applied to develop a high precision extensometer. This extensometer can be applied to monitor the fatigue crack closure.
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