Experimental Investigation of Cyclic Thermo-Mechanical Training Effects in NiTi-Based Elastocaloric Alloys

Superelastic NiTi-Based Alloys represent promising candidates for next-generation elastocaloric cooling applications, combining high energy efficiency with environmental sustainability. Their thermal and mechanical long-term performance depends on the evolution of these characteristics under repeated loading and unloading during training procedure. Thus, experimental investigation of cyclic behavior is essential for material knowledge and optimization of material exploitation.

In this study, NiTi-based materials were subjected to controlled mechanical cycling to quantify training-induced changes in mechanical parameters such as transformation stresses, hysteresis shape and area, and residual strain. Uniaxial tensile tests with defined strain amplitudes and strain rates were combined with in-situ temperature monitoring via infrared thermography to record the coupled thermo-mechanical response.

The experimental results reveal successive and characteristic changes in the mechanical and thermal properties, allowing for a characterization of the stabilization of these properties during the training process. In collaboration with a thermodynamics-based simulation framework, the resulting datasets serve as input for parameter calibration and as basis for validating the simulation model. By comparing experimental results and simulative predictions, the accuracy of the model is critically evaluated and stepwise optimized. This combined experimental–numerical approach provides insights into functional cyclic mechanisms of NiTi-based superelastic alloys and supports the development of training procedures for durable elastocaloric materials.