| Project/Area Number |
09650087
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | Chiba University |
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Principal Investigator |
KOBAYASHI Kennichi CHIBA UNIVERSITY, CENTRE FOR COOPERATIVE RESEARCH, ASSOCIATED PROFESSOR, 共同研究推進センター, 助教授 (50114278)
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| Co-Investigator(Kenkyū-buntansha) |
ASADA Yasuhide THE UNIVERSITY OF TOKYO, GRADUATED SCHOOL OF ENGINEERING, EMERITUS PROFESSOR, 大学院・工学系研究科, 教授 (20011091)
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| Project Period (FY) |
1997 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1999: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1998: ¥900,000 (Direct Cost: ¥900,000)
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| Keywords | CREEP / MULTI AXIAL STRESSES / TERTIARY CREEP / FLUCTUATION OF STRESS / CONSTITUTIVE EOUATION / THETA PROFECTION CONCEPT |
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| Research Abstract |
Severe damage is usually performed in tertiary stage of creep and creep deformation is also unstable in this area. Thus, the tertiary creep has not been taken into account for designing high temperature components. However, the tertiary creep occupied great part of the creep life even for heat resistant materials recently developed. In order to establish reasonable design code under elevated temperature, the tertiary stage should be utilized after the recognition of feasibility of materials and description of creep behavior. Theta projection concept has been proposed not only to describe the whole creep curve shape but also to estimate creep life time under lower stresses and lower temperatures. Since this concept has been mainly studied suing constant stress creep apparatus, it is studied whether it could also be applied to biaxial creep behavior. After tension torsion creep machine was renewed, several biaxial creep tests employing thin walled specimens were performed to investigate biaxial creep deformation. When specimen was deformed over 20% of equivalent creep strain, creep buckling was clearly observed on surface of hollow specimens. Before applying the theta projection concept to creep behavior under biaxial stresses, it was examined with configuration of hollow specimens was the best for large deformation. Experimental results showed that no part of gage length deformed uniformly even at an early part of the secondary stage of creep, and that creep deformation depended on a number of slits machined on circular ridges of specimen. Finite element meshods(FEM) based on elastic creep analysis revealed that the deformation between gage part of the specimen depends on a number of slits. Application of the theta projection concept to the FEM-creep analysis which has initailly been planned has not perfectly performed due to the lack of investigation run time.
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