2002 Fiscal Year Final Research Report Summary
Fatigue strength of in situ processed Cu-Nb composite wires
| Project/Area Number |
13650072
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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 | IWATE UNIVERSITY |
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Principal Investigator |
KATAGIRI Kazumune IWATE Univ., Faculty of Eng. Professor, 工学部, 教授 (90029893)
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| Co-Investigator(Kenkyū-buntansha) |
KASABA Koichi IWATE Univ., Faculty of Eng. Lecturer, 工学部, 講師 (00271841)
SATO Tadashi IWATE Univ., Faculty of Eng. Associate Professor, 工学部, 助教授 (30003859)
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| Project Period (FY) |
2001 – 2002
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| Keywords | Cu-Nb composite wires / Fatigue strength / Fracture mechanisms / Stress-strain characteristics / Cryogenic temperature / Drawing strain / Nb weight fraction / Electric resistivity |
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| Research Abstract |
In order to investigate the fatigue strength of multi- and mono-strand in-situ Cu-Nb composite wires, fatigue tests at room and cryogenic temperatures and fractographic observations were carried out.
1. The 0.2% proof stress and the UTS increased with the Nb content and drawing strain. The Young's modulus did not change with the drawing strain, while it decreased with the Nb content. With decrease in the temperature to 77K, the 0.2% proof stress and the UTS increased by 5 to 10%, while the Young's modulus was almost constant.
2. Although the fatigue strength at high stress amplitude region was high in the wire with high drawing strain, it was almost the same in low stress region regardless of the drawing strain. A drastic decrease in the plastic strain range in the initial stage was observed in the fatigue. At 77K, the fatigue strength increased by a factor of 2.
The fatigue strength in the wire with high Nb content was high at high stress region, while it was rather low at low sterss region. This is explained by the magnitude of plastic strain range associated with the Young's modulus and work hardening in the wires with high and low Nb content in the high and low stress regions.
4. The slip plane decohesion facets and inclusions within the Cu wire sheath were possible sites for the crack initiation. Te magnitude of small irregularity in the fatigue crack propagation region was smaller at low temperature.
5. Evidence on the roles of the Nb filaments acting as barriers against crack propagation was obtained.
6. The effect of mean stress on the fatigue strength was small.
7. The residual resistivity at 4.2K and 14T was 0.10μΩcm and it increased by 0.02μΩ cm with straining by 1.8%.
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