Evaluation of Thermo-Mechanical Cyclic Properties of Shape Memory Alloy Aiming to Electric Generation System with Mass and Low Temperature Heat Source.

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The basical study of the evaluation of thermo-mechnaical cyclic properties of shape memory alloy (SMA) were performed in order to investigate a possibility to apply of SMA as the energy conversion elements for the electric generation system. The SMA's used in this study were TiNiCu group alloy which had superior properties in the alloy stability, the corrosion resistance, the transformaton temperature and the fatigue property arid four kinds of alloys with Cu contents of 0-13 at.% . The results obtained were summarized as the followings.1. The martensitic transformation temperature Ms increased with increasing of the Cu contents, and the inversed transformation temperature As decreased with the Cu contents and saturated at the high strain range.2. The effective strain energy-W^<av> by strain cycling increased with the Cu contents in the range of the maximum strain epsilon_<max>*3%, and saturated to constant in the high strain range.3. The dispersion strain energy which were determined as the decrease in the recovery strain energy per 1 cycle, decreased with the Cu contents. The recovery strain enrgy was determined as the area of cyclic stress - strain hysteresis loop.4. The relationship between the recovery strain energy and the fatigue life was a straight line in log -log diagram in the range of epsilon_<max>*3% in spite of the defference of shape memory heat treatment temperature.5. The relationship between the dispersion strain energy and the fatigue life was evaluated as a straight line in log - log diagram in the experimental conditions of the maximum strain and the heat treatment temperature in this study.6. The fatigue life in the condition of the super elasticity cycles showed low life in the range of the Cu contents of 5-10%. On the other hand, the fatigue life in the condition of the thermo-mechnaical cucles decreased with the Cu contents.