On the Micro-deformation Mechanism of Shape Memory Alloy under Complex Thermo-mechanical Loading Conditions and its Applications

研究成果总结：目前形状记忆合金的工业/工程应用还相当局限于单轴变形，例如使用简单的伸长-收缩进行简单的线性驱动运动。另一方面，从形状记忆合金的基本变形机理来看，可以期望形状记忆合金的变形方式更加复杂和优雅。即形状记忆合金的基本变形机制是马氏体相变（及其反向相变）。该相变由7个独立参数控制，即温度张量和应力张量，其独立分量个数为6。本研究的目的是从根本上、系统地研究形状记忆合金的7个参数的作用，并开发形状记忆合金的工业应用，如三维致动器、复杂器件、使用这些致动器和器件的智能材料系统。在本研究中，对cu基形状记忆合金薄壁管状试样施加了各种轴向力和扭矩的组合载荷，并观察了相应的变形性能。此外，建立了新的显微观察系统，观察了复杂加载条件下马氏体变形的行为。在这些基础实验研究中，收集了许多重要的数据，这些数据对于分析复杂加载条件下晶粒中马氏体变异的形核、生长和消失之间的关系具有重要意义。

Summary of Research Results : The present industrial/engineering application of shape memory alloy has been rather limited to the uniaxial deformation, e.g., the simple linear actuating movement using the simple elongation-contraction. On the other hand, the shape memory alloy can be expected to deform in more complex and elegant way, judging from the fundamental deformation mechanism of shape memory alloy. That is, the fundamental deformation mechanism of shape memory alloy is the martensite phase transformation (and its reverse phase transformation). This phase transformation is controlled by 7 independent- parameters, that is, the temperature and the stress tensor whose number of independent components is 6. The aim of this research work is to investigate fundamentally and systematically the role of 7 parameters and to develop the industrial applications of shape memory alloy, for examples, the three-dimensional actuator, complex device, intelligent material systems using these actuators and devices. In this research work, the various kind of combined loads of axial force and torque were applied to the thin-walled tubular specimen of Cu-based shape memory alloy and the corresponding deformation performances were observed. Moreover, the new microscopic observation system was constructed, and the behavior of martensite variant under complex loading conditions was observed. In these fundamental experimental investigations, numerous important data were collected, which are very important for the analysis of the relationship among the nucleation, growth and disappearance of martensite variant in the crystal grain under the complex loading conditions.