A novel experimental setup is presented that allows for precise control of thermal and mechanical loads, and simultaneous monitoring of the temperature and the full-field deformation of small SMA structures that undergo phase transformations. The facility is used to conduct two experiments in which NiTi tubes are taken through a temperature cycle under constant load that leads to phase transformations in the form of helical localization bands that propagate along the specimen. The latent heat of transformation causes a complex interaction with the prescribed load and thermal environment. By changing the rate of the airflow through the environmental chamber it is revealed that the velocities of the transformation fronts depend on the rate at which heat is removed/added by the controlled environment. The experiments are simulated using a new fully coupled thermomechanical extension of the constitutive framework developed by this research group. Key features of the framework include the modeling of the reversible $A\rightleftarrows M$ transformation through a single surface in the deviatoric stress-temperature space that obeys kinematic hardening; with the transformation strain and entropy as the internal variables governed by an associative flow rule; and the inhomogeneous deformation exhibited in tension being modeled as softening. The tube is analyzed in a finite element coupled static displacement transient temperature analysis, and taken through the cool/heat cycle of the experiment. The temperature-strain response is accurately reproduced with the two transformations initiating at essentially the same temperatures as in the experiment and propagating in similar localized banded manners at similar speeds. Reproduction of the complex behavior observed in the experiments requires the calibration of the constitutive model, its discretization, and the modeling of the structure and its boundary conditions to work together to near perfection. The simulation also demonstrated that the heat exchange between the structure and the environment, in the present analysis governed by only by convection, requires further enhancement.

提出了一种新颖的实验装置，可以精确控制热负荷和机械负荷，并同时监测经历相变的小型 SMA 结构的温度和全场变形。该设施用于进行两个实验，其中 NiTi 管在恒定负载下通过温度循环，导致沿样品传播的螺旋定位带形式的相变。转变潜热导致与规定负载和热环境的复杂相互作用。通过改变通过环境室的气流速率，可以看出转换前沿的速度取决于受控环境移除/添加热量的速率。使用该研究小组开发的本构框架的新的完全耦合热机械扩展来模拟实验。该框架的主要特征包括可逆建模$A\rightleftarrows 米$通过服从运动硬化的偏应力-温度空间中的单个表面进行转换；以变​​换应变和熵为内部变量，受关联流法则约束；并且将在拉伸中表现出的不均匀变形建模为软化。该管在有限元耦合静态位移瞬态温度分析中进行了分析，并通过了实验的冷/热循环。通过在与实验中基本相同的温度下开始并以相似的速度以相似的局部带状方式传播的两种转变，准确地再现了温度-应变响应。实验中观察到的复杂行为的再现需要本构模型的校准、离散化、和结构建模及其边界条件一起工作以接近完美。模拟还表明，在目前的分析中，结构与环境之间的热交换仅受对流影响，需要进一步加强。