1999 Fiscal Year Final Research Report Summary
Investigation on Threshold Behavior of High Temperature Fatigue Crack Propagation and Its Mechanisms Using Macroscopic Experiments and Microscopic Molecular Dynamic Analyses
| Project/Area Number |
09450050
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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 |
KUBO Shiro Graduate School of Engineering, Osaka University, Professor, 大学院・工学研究科, 教授 (20107139)
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| Co-Investigator(Kenkyū-buntansha) |
TSUJI Masahiro Graduate School of Engineering, Osaka University, Research Associate, 大学院・工学研究科, 助手 (10132630)
SAKAGAMI Takahide Graduate School of Engineering, Osaka University, Associate Professor, 大学院・工学研究科, 助教授 (50192589)
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| Project Period (FY) |
1997 – 1999
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| Keywords | High Temperature Fatigue / Fatigue Crack Propagation / Threshold / Molecular Dynamics / Simulation / Fracture Mechanics |
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| Research Abstract |
The present project investigated the near-threshold fatigue crack propagation behavior and mechanisms of the threshold For this purpose macroscopic high temperature fatigue crack propagation experiments were conducted. Effects of environment, loading frequency, temperature and loading history were examined. On the other hand microscopic molecular dynamic analyses on near-threshold fatigue crack propagation were made. The results obtained are summarized as follows.
1.For SUS 304 stainless steel and Ni-base super alloy, high temperature fatigue crack propagation experiments were conducted in air and in vacuum. It was found that environment, loading frequency, and temperature had major influences on the near-threshold fatigue crack propagation rate da/dN and the threshold. The crack propagation resistance was lower that in air.
2.For aged Cr-Mo-V steel, high temperature crack propagation behavior was investigated. The effect of aging on the crack propagation was small. The estimation of remaining life was made. The influences of many parameters on the life were identified.
3.The simulations of the near-threshold fatigue crack propagation in iron were made using the molecular dynamics. A scheme was proposed which considered the decrease in the inter-atomic force due to oxidation of the new crack surface. It was found that near-threshold fatigue crack propagation behavior can be simulated by using the molecular dynamics. The effects of the orientation and grain boundary were examined. The crack propagation behavior contained in the linear elastic singular stress field was compared with that in the Hutchinson-Rice-Rosengren plastic singular field.
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