1987 Fiscal Year Final Research Report Summary
Evaluation of Creep-Fatigue-Environment Interaction Based on Mechanical Response
| Project/Area Number |
61460085
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
材料力学
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| Research Institution | University of Tokyo |
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Principal Investigator |
ASADA Yasuhide Faculty of Engineering, University of Tokyo, 工学部, 教授 (20011091)
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| Co-Investigator(Kenkyū-buntansha) |
MITSUHASHI Shunsaku Faculty of Engineering, University of Tokyo, 工学部, 助手 (20010845)
HISADA Toshiaki Faculty of Engineering, University of Tokyo (BABA,Hiroshi), 工学部, 助教授 (40126149)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Creep-Fatigue Interaction / Environmental Effect / Overstress / Internal Stress / Back Stress / Drag Stress / Life Prediction Equation / Time-Dependent Damage / 時間非依存損傷 |
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| Research Abstract |
Creep-Fatigue Tests were made with 304 stainless steel at 650゜C and with 2 1/4Cr-lMo steel at 550゜C in arr and vacuum of 0.1 mPa and 0.1 <mu>Pa under a wide variety of strain loading conditions. Test data of stress-strain response and fatigue properties were stored in a data base for further analyses.
It was shown that the stress-strain response is independent of test environments for both steels. A measured stress is composed of the overstress and the internal stress. The internal stress of 304 steel is composed of the back stress. However, in 2 1/4Cr-1Mo steel, the internal stress is composed of the drag component and back component of the stress.
The overstress and back stress of 304 steel depend upon both inelastic strain rate and strain range. However, in 2 1/4Cr-1Mo steel, the overstress is independent of these test variables. The drag stress of this steel depends upon only a strain range. The back stress depends upon the inelastic strain rate. It was shown with both steels that the back stress depends upon the cyclic strain hardening or softening behavior.
The time-independent damage factor of both steels can be described with the overstress and a mean stress. Regarding the time-dependent damage factor, that of 304 steel can be described with the overstress. But that of 2 1/4Cr-1Mo steel can be described with the internal stress. Based on these results, an evaluation equation was derived for the pure creep-fatigue behavior of these two steels.
Based on the above equation, the environmental effect was seperated from the creep-fatigue interaction and was abalyzed with mechanical quantities of stress and strain. It was shown that the environmental effect is mainly affected by a strain rate. An evaluation oquation was obtained with respect ot the environmental damage described with mechanical parameters.
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