加载频率对镍钛形状记忆合金循环压缩过程中相变、塑性与传热相互作用的影响

探讨了多晶超弹性镍钛形状记忆合金在静止空气环境下位移控制循环的压缩响应，特别关注了在最大应变4.2%的条件下，频率范围为0.000 7～50 Hz合金的动态行为。深入探讨了相变、奥氏体相的塑性流动以及传热这三种机制之间的相互作用。利用热成像技术同步记录了温度振荡与应力-应变关系的动态演变。研究结果显示，在给定应变条件下，存在一个关键的频率阈值。当频率低于这一阈值时，热机械响应主要由纯相变与传热之间的频率依赖耦合所主导；一旦频率超过该阈值，奥氏体相的宏观塑性变形便会显著参与循环的瞬态阶段，并与相变和传热发生复杂的相互作用。这一发现为深入理解镍钛形状记忆合金在动态加载条件下的性能提供了重要的参考依据。

Displacement-controlled cyclic compressive responses of polycrystalline super-elastic NiTi shape memory alloyswere investigated at a maximum strain of 4. 2% and over frequency ranging from 0. 000 7 Hz to 50 Hz in stagnant air. The study focused on the interactions among three mechanisms: phase transformation (PT),plastic flow of austenite phase and heat transfer. Temperature oscillations recorded by thermography technique were synchronized with the evolutions of stress-strain relations. It is found that for a given strain, there is a critical frequency, below which the thermomechanical responses are dominated by the frequency dependent coupling between pure PT and heat transfer and above which the macroscopic plastic deformation of austenite phase gets involved in the transient stage of the cycling and interacts with PT and heat transfer. This finding provides an important reference for us to understand the performance of NiTi shape memory alloys under dynamic loading conditions.