中文摘要：

镍钛形状记忆合金在应用过程中，不可避免地承受热机械循环载荷作用，进而导致材料的结构性和功能性疲劳失效。热力学循环变形试验在自主开发的热机械循环试验平台上开展，并实时采集力、位移和温度信号，提取循环应力、应变和温度演化曲线，研究热机械循环变形对形状记忆效应的劣化作用。试验结果表明：机械循环载荷将轻微降低镍钛形状记忆合金在升温过程中的应变回复能力；同时，形状记忆效应随着热机械循环和温度循环次数的增加出现显著劣化。研发的热机械循环变形试验平台可用于揭示镍钛形状记忆合金功能性退化机理，为进一步对形状记忆合金器件的性能评估提供有益参考。

英文摘要：

NiTi shape memory alloy is often subjected to the thermo-mechanically cyclic loadings in applications, which leads to structural and functional fatigue failures of the alloy. The thermo-mechanically cyclic deformation tests were carried out by using the self-developed thermo-mechanically cyclic test platform ; the signals of force, displacement and temperature were collected in real time. By extracting the evolution curve of cyclic stress, strain and temperature, the influences of the thermo-mechanically cyclic deformation on shape memory effect were investigated. Results show that a pre mechanically cyclic loading reduces slightly the strain recovery capacity during heating process, but the shape memory effect decreases remarkably with the increasing number of cyclic under the thermo-mechanically cyclic loading and temperature cycling load- ing. The developed platform using for the test of thermo-mechanically cyclic deformation can be used to indicate the functional degradation mechanism of NiTi shape memory alloy. It is a useful reference for the further performance evaluation of shape memory alloy based devices.