Characterization of NiTi-based SMA Performance for Transient Thermomechanical Heat Engine Applications

Worldwide, two-thirds of the consumed thermal energy is wasted as heat. Shape memory alloys (SMAs) have shown promising potential for capturing and converting this heat into useful work. In typical mechanical systems, work output is directly proportional to the generated force and displacement against an external load. However, in fluid based SMA systems, such as heat engines, additional factors like heat transfer, flow rates, material composition, processing, geometry, and pre-strain affect the work output and the overall efficiency. Traditional methods like tensile testing and differential scanning calorimetry struggle to characterize these factors due to their neglect of dynamic transients and biasing elements. This study introduces a fluid-based test setup designed to account for and characterize these SMA factors. Using this apparatus, the study presents results and analyses for different SMA compositions, geometries, thermomechanical histories, and operating conditions, aiming to optimize power output and efficiency in fluid-based heat engine applications.