2003 Fiscal Year Final Research Report Summary
Variation in Functional Properties of Shape Memory Materials under Use of Long Duration
| Project/Area Number |
13650104
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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 | Aichi Institute of Technology |
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Principal Investigator |
TOBUSHI Hisaaki Aichi Inst. of Tech., Dept. of Mechanical Engineering, Professor, 工学部, 教授 (70103231)
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| Project Period (FY) |
2001 – 2003
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| Keywords | shape memory alloy / shape memory polymer / cyclic deformation property / fatigue property / creep / stress relaxation / shape recocery / secondary shape forming |
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| Research Abstract |
In the present study, functional properties of shape memory alloy (SMA) and shape memory polymer (SMP), fatigue properties of SMA and deformation properties of SMP held at the fixed shape for a long duration were investigated. The results obtained can be summarized as follows.
(1)In the subloop loading of SMA under the stress-controlled conditions, stress relaxation under constant strain and creep deformation under constant stress appear in the loading process. Stress recovery and creep recovery appear in the unloading press. These pseudoviscoelastic behaviors are induced due to the martensitic transformation based on variation in temperature.
(2)An alternating-plane bending fatigue testing machine for an SMA wire was newly developed. The influence of strain ratio on fatigue life is systematically expressed by using maximum strain for rotating-bending, pulsating-plane bending and alternating-plane bending fatigue of an SMA wire. Fatigue life of a newly developed superelastic thin-walled
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tube is shorter than that of a wire. Fatigue crack of a thin tube initiates on an inner surface. The ratio of fracture surface due to fatigue in a thin tube is small.
(3)With respect to a newly developed highelastic thin wire, the stress-strain curve is almost straight till a stress level of 1400 MPa and an amount of strain of 4%. The fatigue property does not depend on temperature and frequency. Modulus of elasticity is one fourth of that of stainless steel. The highelastic thin wire has high performance for a medical guide wire.
(4)If an SMP foam is loaded at high temperature and the deformed shape is held at low temperature, both ratios of shape fixity and shape recovery are larger than 98 % without depending on maximum strain after holding for six months.
(5)If the deformed shape of an SMP foam is held at high temperature, secondary shape forming occurs, resulting in imperfect shape recovery. The ratio of shape irrecoverableness increases in proportion to shape-holding temperature, shape-holding strain and shape-holding time. Less
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