Takeda Kohei, Tobushi Hisaaki, Pieczyska Elzbieta A
Department of Mechanical Engineering, Aichi Institute of Technology, 1247 Yachigusa, Yakusa-cho, Toyota 470-0392, Japan.
Institute of Fundamental Technological Research, Polish Academy of Sciences, Pawinskiego 5B, Warsaw 02-106, Poland.
Materials (Basel). 2012 May 22;5(5):909-921. doi: 10.3390/ma5050909.
If the shape memory alloy is subjected to the subloop loading under the stress-controlled condition, creep and creep recovery can appear based on the martensitic transformation. In the design of shape memory alloy elements, these deformation properties are important since the deflection of shape memory alloy elements can change under constant stress. The conditions for the progress of the martensitic transformation are discussed based on the kinetics of the martensitic transformation for the shape memory alloy. During loading under constant stress rate, temperature increases due to the stress-induced martensitic transformation. If stress is held constant during the martensitic transformation stage in the loading process, temperature decreases and the condition for the progress of the martensitic transformation is satisfied, resulting in the transformation-induced creep deformation. If stress is held constant during the reverse transformation stage in the unloading process, creep recovery appears due to the reverse transformation. The details for these thermomechanical properties are investigated experimentally for TiNi shape memory alloy, which is most widely used in practical applications. The volume fraction of the martensitic phase increases in proportion to an increase in creep strain.
如果形状记忆合金在应力控制条件下进行子循环加载，基于马氏体相变会出现蠕变和蠕变恢复。在形状记忆合金元件的设计中，这些变形特性很重要，因为形状记忆合金元件的挠度在恒定应力下会发生变化。基于形状记忆合金马氏体相变的动力学，讨论了马氏体相变进行的条件。在恒定应力速率加载过程中，由于应力诱发马氏体相变，温度会升高。如果在加载过程中的马氏体相变阶段应力保持恒定，温度会降低，并且满足马氏体相变进行的条件，从而导致相变诱发的蠕变变形。如果在卸载过程中的逆相变阶段应力保持恒定，由于逆相变会出现蠕变恢复。针对实际应用中使用最广泛的TiNi形状记忆合金，对这些热机械性能的细节进行了实验研究。马氏体相的体积分数与蠕变应变的增加成正比。
