A CASMART Review of Processing Case Studies of NiTi and NiTiHf Shape Memory Alloy Torque Tubes for Actuation Devices

Shape memory alloys (SMAs) are used for a wide range of engineering applications, including biomedical, automotive, aerospace, and technological fields, where each of these fields require specific functions for the SMAs and specific environmental conditions to consider. Furthermore, processing these SMAs into usable forms, depending on each application, is a critical consideration for optimizing the performance and commercial success of the device. For example, applications in the aerospace industry can be shape-morphing wings or extending solar panels, which can be designed to activate passively or actively while operating in extreme environmental conditions. These SMA actuation devices in the aerospace industry are often in the form of torque tubes. While many routes to producing torque tubes exist, there is a need to evaluate these various methods of processing to produce torque tubes and examine the effectiveness of these processing methods both economically and performance-wise. In this Consortium for the Advancement of Shape Memory Alloy Research and Technology (CASMART) Processing Working Group review, various processing routes for SMA torque tube production will be discussed through case studies. From each of these case studies, the lessons learned, current standards and guidelines for certification, advantages/disadvantages of the particular processing route, and potential future directions in light of current state-of-the-art technology will be presented.