| Project/Area Number |
10555233
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 展開研究 |
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| Research Field |
Structural/Functional materials
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| Research Institution | Toyota Technological Institute |
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Principal Investigator |
UENO Akira Toyota Technological Institute, Dept. of Advanced Science and Technology, Associate Professor, 工学部, 助教授 (30160188)
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| Co-Investigator(Kenkyū-buntansha) |
KISHIMOTO Hidehiro Technological Institute, Dept. of Advanced science and Technology, Professor, 工学部, 教授 (10148348)
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| Project Period (FY) |
1998 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥4,100,000 (Direct Cost: ¥4,100,000)
Fiscal Year 2001: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 2000: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1999: ¥3,300,000 (Direct Cost: ¥3,300,000)
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| Keywords | Ceramics / Crack initiation / Small crack / Scanning laser microscope / Atomic force microscope / Photon emission / Mixed mode fracture / Crack propagation / モードII / レーザー顕微境 / 窒素ケイ素セラミックス / 微小き裂 / その場観察 / レーザー顕微鏡 / フラクトエミッション / モンテカルロシミュレーション |
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| Research Abstract |
In this study, following four subjects were investigated.
(1) A Monte-Calro simulation taking into account the defects size distribution and the micro-crack propagation behavior was conducted by using virtual bending specimens. For the cases of the simulation using micro-crack propagation behavior, the estimated bending strength well coincided with the factual bending strength. Through the evaluation of the effects of scatter in a crack propagation rate, it is reconfirmed that the wide scatter in fracture strength mainly originated from the scatter of defect size.
(2) Fatigue crack initiation and propagation in smooth specimens of a sintered Si_3N_4 have been investigated under a static fatigue conditions. Naturally initiated small cracks in smooth specimens propagate with stress-intensity factors which are far lower than the apparent threshold stress-intensity factor of artificial long cracks. In some cases, small crack stops propagation or propagates very slowly after the crack initiation. In case of a naturally initiated small crack, the effect of cyclic loading on the propagation behavior is less than that of artificial long crack. Also, using the AFM, we can detect the some evidence of grain-bridging degradation on the naturally initiated small cracks.
(3) To evaluate the crack initiation properties in ceramic materials, photon emission are measured by using a photon multifier tube. A lot of photon are emitted at the instant of fracture. Photon emission continues for a little while. In case of Si_3N_4, photon count number increases gradually by the fracture. It is considered that this phenomen on caused by crack initiation.
(4) In this study, crack propagation behavior on glass have been studied by using the newly developed in-situ type bi-axial bending machine. The threshold stress intensity under mixed mode tends to decrease with increase in the stress mixing ratio R. The criteria in which the crack began to grow under mixed mode condition were proposed.
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