1999 Fiscal Year Final Research Report Summary
Nano-Fractography Study of Fatigue Crack Growth under Service Loading in Ceramics
| Project/Area Number |
09450051
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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 | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Osaka University |
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Principal Investigator |
SUGETA Atsushi Graduate School of Engineering, Osaka University Associate Professor, 大学院・工学研究科, 助教授 (60162913)
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| Co-Investigator(Kenkyū-buntansha) |
UEMATSU Yoshihiko Graduate School of Engineering, Osaka University Research Associate, 大学院・工学研究科, 助手 (80273580)
JONO Masahiro Graduate School of Engineering, Osaka University Professor, 大学院・工学研究科, 教授 (20029094)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Fatigue Strength / Fatigue Crack Growth / Ceramics / Crack Closure / Small Crack / Service Loading / KィイD2effィエD2 / Crack Initiation |
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| Research Abstract |
In order to investigate cyclic fatigue crack growth behavior of a gas-pressure-sintered silicon nitride, SiィイD23ィエD2NィイD24ィエD2 and SiィイD23ィエD2NィイD24ィエD2 /BN compound sintered ceramics under constant and variable amplitude load sequences, fatigue crack growth tests were carried out using compact type (CT) specimens. Crack length and macroscopic crack closure were measured using an unloading elastic compliance method. The grain interlocking was observed around crack wake in all fatigue test conditions, which implied fatigue crack growth of this material was associated with progressive degradation of the grain interlocking by cyclic loading. Fatigue crack growth rate, da/dn, under constant amplitude loading was controlled not only by maximum stress intensity factor, KィイD2maxィエD2, but also stress amplitude, while KィイD2maxィエD2 was the most important factor in cyclic fatigue crack growth. The overload and high-level load excursion produced the acceleration of fatigue crack growth and the decrease of crack closure point under low-level loading. This decrease was thought to result from much severer crash or frictional wear of grain interlocking and the crack closure could explain the acceleration behavior qualitatively.
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