| Project/Area Number |
16K05978
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Kobe University |
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Principal Investigator |
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| Project Period (FY) |
2016-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000)
Fiscal Year 2018: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2017: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2016: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
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| Keywords | 構造・機能材料 / マイクロマシン / 金属物性 / 引張圧縮疲労 / 軸力 / 機械材料・材料力学 / 引張圧縮費用 |
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| Outline of Final Research Achievements |
In this study, a new tension/compression fatigue test method under cyclic axial loading for metallic thin wires used for MEMS was developed. The electrolytic polishing was applied to commercially pure iron wire to prepare a test piece with a minimum wire diameter of 700-180μm, and developed tension/compression fatigue tests were successfully conducted. The developed method is much better than conventional fatigue tests using reversed bending loading, because an accurate value of stress could not be obtained under bending due to plastic deformation.
The fatigue life decreased as the stress ratio, R, increased for R=-1, -0.1 and 0.1. For R=-1 and high-cycle fatigue of R=-0.1, the fatigue crack propagation caused failure, while for R=0.1 and low-cycle fatigue of R=-0.1, fatigue failure due to accumulation of plastic deformation was observed. Also, the effect of wire diameter was examined. Compared at the same stress amplitude, the fatigue life increased as the wire diameter decreased.
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| Academic Significance and Societal Importance of the Research Achievements |
これまでに行われていた細線の引張圧縮疲労試験としては，軸力ではなく，繰返し曲げを与える方法がとられてきた．しかし，曲げでは塑性変形が生じると応力の値を正確に知ることができない致命的な欠点があった．本研究で開発した軸力を用いた試験によって，初めて正しいS-N曲線が得られるようになった．これによって，微小素材に対してS-N曲線に基づく耐疲労設計が可能になることは，工学上とても大きな意義があると考える．
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