不同温度和应力状态下Ni-Ti形状记忆合金力学行为分析

Research on the Mechanical Behavior of Ni-Ti SMA at Various of Stress States and Temperature

摘要:

为了研究Ni-Ti形状记忆合金在不同应力状态下的力学行为,文中通过分离式Hopkinson杆实验装置分别对不同Ni-Ti形状记忆合金试样进行了动态拉伸和压缩试验。实验温度从291~573 K。从不同应力状态和试验温度的试验结果分析中发现:Ni-Ti形状记忆合金的相变屈服应力和位错屈服应力均随着试验温度的增加而增加；此外,同一Ni-Ti形状记忆合金压缩状态下的相变屈服应力和位错屈服应力均明显高于其拉伸状态下的相变屈服极限和位错屈服极限；而且对于同一Ni-Ti形状记忆合金,变形后材料的逆相变起始温度比变形前材料逆相变的起始温度高,且应变率越高,逆相变起始温度增加的越快。

Abstract:

In order to understand the mechanical behavior of Ni-Ti shape-memory alloy (SMA) at various temperatures and stress states, a series tests are performed. The dynamic tensile and compressive response of a Ni-Ti shape-memory alloy are investigated at various strain rates, using a modified split Hopkinson bar. The dynamic deformation behavior of Ni-Ti shape-memory alloys, in relation to different substructures, is discussed for different stress states and temperatures and a few noteworthy conclusions are as follows that the phase yield limit and dislocation yield limit increase with the increasing test temperature; the phase yield limit and dislocation yield limit of compression are higher than that of tention; the reverse transformation doesn’t occur during high strain rate deformation even though the temperature exceeds the As and Af of the unreformed specimen.