Evaluation of Degrading Characteristics of Ti-Ni Shape Memory Alloy under Combined Cyclic Condition of Load, Displacement and Temperature

本研究于1988年和1989年进行，目的是评估Ni-Ti形状记忆合金在载荷、位移和温度复合循环条件下的循环降解特性。在1988年的第一年，我们开发了一个实验系统来研究Ni-Ti形状记忆合金的材料性能。然后，利用该测试系统对两相低循环范围内的降解过程进行了精确研究；一个是形状记忆效应，另一个是超弹性效应。1989年第二年，采用电阻加热法系统地进行了长达10000次的长寿命循环降解试验，使我们能够进行周期约为20秒的热循环试验。经过2年的研究，得出的主要结论如下：(1)证实了本研究中用于评价形状记忆合金降解过程的实验系统的性能水平较高。(2)控制形状记忆效应的热处理条件主要影响马氏体转变温度，热处理温度越低，诱导马氏体转变的负荷水平越高。(3)低温热处理可长期保持形状记忆效应和超弹性。

The aim of this Study, conducted during two years of 1988 and 1989, is to evaluate the cyclic degrading characteristics of Ni-Ti shape memory alloy under combined cyclic conditions of load, displacement and temperature. In the first year of 1988, an experimental system was developed to investigate the material performance of the Ni-Ti shape memory alloy.And then, by using this testing system, degrading processes in low cycles range were studied precisely on two phases; one was shape memory effect and another was superelasticity. In the second year of 1989, degrading tests in long life range up to 10000 cycles were conducted systematically by adopting resistance-heating procedure, which enable us to conduct thermal cycle tests with period of about 20 sec.Major conclusions obtained through 2 year investigation can be summarized as follows:(1) It was confirmed that the level of performance of the experimental system used in this study to evaluate the.degrading processes of shape memory alloy-was high. (2) Heat-treatment condition to control the shape memory effect predominantly influenced the martensite transformation temperature, and the lower was the heat-treatment temperature the higher was the load level to induce the martensite transformation. (3) Shape memory effect and superelasticity could be kept during long term range when heat-treated at low temperature.