| Research Abstract |
The aim of this research work is to try to construct/design the three-dimensionally controlled positioning material device by using the Shape Memory Alloy with the combined bias stresses. This positioning system may not have some quick responses to the change of atomoshere. On the other hand, the device may be quite stable and tough in a longterm, and this device have an important role in the robot-systems which response to the gradual temperature change of atmosphere (air, river, ocean and so on) in a day, or in a year. The most important point in this research work is to formulate the reliable consititutiveequations which can predict the complicated behaviors of shape memoryalloy under the general thermo-mechanical conditions. It is very important to note that the shape memory alloy is controlled by 7parameters, that is, 6 stress components and temperature. This reliable and precise constitutive equations are indispensable to design the positioning system which can behaive according
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to our purpose/intension. Based on this idea, in the first fiscal year of this project, a set of constitutive equations was formulated. In this formulation, the meso-mechanical approach was used, because the shape memory materials used in the industrial application arepolycrystalline materials whose structure is not in homogeneous. In the(final) next fiscal year, the reliability and accuracy of the formulated constituive equations were confirmed experimentally by applying the combined loads of axial force and torque to the thin-walled tubular specimens made of Cu-based shape memory alloy. Moreover, in this experiments, the assumptions used in the formualtion of constitutive equations are also confirmed by the observation of microstructural change in the materials subjected to the complex thermo-mechanical loading conditions including the loading path. In the final stage of this research work, an idea of pilot device of positioning device was proposed, which is controlled by the three parameter ; torsional stress, tensile stress and temperature. Unfortunetely, the detail of this device is still under discussion. The head investigator hopes to publish the detail of the device in some near future. Less
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