循环加载条件下TiNi形状记忆合金超弹性变形特性分析与模拟

Analysis and simulation on cyclic superelastical deformation behavior of TiNi shape memory alloy subjected to loading and unloading

超弹性是形状记忆合金(SMA)重要的力学性能之一,本文在试验研究的基础上讨论了在不同试验温度和应变速率的循环加载条件下,TiNiSMA的超弹性变形特性。从唯象观点分析了循环变形期间相变应力和弹性模量的变化。通过引入三个内变量,即循环期间所累积的残余应力、残余应变和残余马氏体相,表征承受加载和卸载的TiNiSMA循环超弹性变形。在此基础上,提出了模拟TiNiSMA的超弹性变形方法。在部分加载的内循环情况下,采用相变应变函数的混合规则表达材料的弹性模量。

Superelasticity is one of the important mechanical properties of shape memory alloy (SMA). In the present paper, the superelastic deformation behavior of TiNi SMA under various loading conditions with different experimental temperatures and strain rates was discussed based on the experimental studies. The change of transformation stress and the modulus of elasticity during cyclic deformation was analyzed from the continuum mechanical point of view. The cyclic superelastic deformation of TiNi SMA subjected to loading and unloading is characterized by introducing three internal variables, that is, the residual stress and strain which are accumulated during cycling and the residual martensite phase which is also accumulated. The method of simulating cyclic superelastic behavior deformation was proposed. The modulus of elasticity during the internal loop is expressed by the mixed rule with the function of transformation strain. It is important to design perfect SMA working elements and to evaluate their reliability.