2005 Fiscal Year Final Research Report Summary
Development of Elevated Temperature Fatigue Testing Technique for Micro Components used in Micro Power Generating Systems
| Project/Area Number |
16560086
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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 | Ritsumeikan University |
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Principal Investigator |
LEE Yeonkyeon Ritsumeikan University, Fac. Science and Engineering, Assistant Professor, 理工学部, 助手 (40373104)
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| Co-Investigator(Kenkyū-buntansha) |
ISONO Yoshitada Ritsumeikan University, Fac. Science and Engineering, Professor, 理工学部, 教授 (20257819)
TORIYAMA Toshiyuki Ritsumeikan University, Fac. Science and Engineering, Professor, 理工学部, 教授 (30227681)
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| Project Period (FY) |
2004 – 2005
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| Keywords | Fatigue Life / Bending Testing / Atomic Force Microscope / Silicon / Cantilever / Micro Structural Design |
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| Research Abstract |
Single crystal silicon (SCS) micro components used in MEMS often suffer from cyclic fatigue damage due to their fluctuating motion. Evaluating fatigue damage as well as quasi-static mechanical properties of micro SCS structures is essential for safe operation and life extension of MEMS. The authors have so far carried out high cyclic fatigue tests of microscale SCS specimens under uniaxial tensile and one-directional bending stressing at elevated temperatures. Here, the applicable parameter to predict fatigue lives of SCS was proposed on a broad-range of specimen size from nanoscale to microscale. However, SCS components in MEMS would undergo not only tensile stress but also compressive stress. For example, components used in silicon based power MEMS, such as micro turbo machinery and micro reciprocating engine operating at high temperatures ; usually receive tension/compression fatigue damage with lower strain rate attributed to cyclic thermal hysteresis at the start/stop of the devic
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es. Optical micro switches will be also subject to tension-compression cyclic loading in a full-reversed bending deformation. In order to establish a reliable design criterion for silicon-based MEMS, new damage evaluation technique under cyclic tensile/compressive loads is required. This research developed a full-reversed bending fatigue tester that can apply cyclic tensile/compressive loads to a microscale SCS specimen using twin thick-cantilevers.
A novel full-reversed bending fatigue tester was developed for cyclic fatigue damage evaluation of MEMS materials. This paper focuses on ; 1)the design of the micro fatigue tester ; 2)establishment of the bending fatigue testing procedure ; and 3)revealing fatigue lives of microscale single crystal silicon (SCS) specimens. In fatigue testing, an SCS specimen was reciprocated between the twin thick-cantilevers to induce tensile and compressive stresses at both fixed ends of the specimen, respectively. The twin cantilevers played two roles ; one is as an indenter for bending and the other as a detector of cyclic loads applied to a specimen. The bending loads were measured by the deflection of the twin cantilevers using a laser reflection system based on AFM technique. Quasi-static bending tests of micro SCS specimens demonstrated the measurement accuracy of bending force and reliability of the displacement control systems of the tester. We succeeded the full-reversed cyclic bending tests, whereby the elastic stress-strain hysteresis loops of micro SCS specimen was obtained. This research will propose an effective parameter to predict fatigue lives of microscale SCS without respect to test conditions. Less
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