Shape Memory Alloy Rotary Actuators for Aerospace: Part 1 Design and Testing

Abstract Shape memory alloys (SMA) provide a compact, robust, light-weight and scalable rotary actuation technology suitable for many aerospace applications that require precise control and high torque. Over the last 25 years Boeing has fabricated, processed and characterized several hundred NiTi-based tubes with the objective of optimizing performance for aerospace applications. The effects of supplier, material composition, processing, heat treatment, training parameters and component size were characterized and mapped in NiTi and NiTiHf systems. The effects of lower and upper cycle temperature (LCT and UCT, respectively), applied torsional loading (including nominal, minimum, maximum, reversed and varying), rotational limits (blocking) and repeated thermal cycling (to over 100,000 cycles) were systematically investigated. Based on those results, torsional SMA components were fabricated for optimal performance and evaluated under repeated thermal cycling under load to assess their ability to meet actuator requirements for an applications’ required life cycle. Additionally, isothermal torque-deflection and constant torque thermal cycling test (similar to E3414) have been performed across all relevant actuator parameters. This paper reviews and summarizes test outcomes, providing additional insight into the design and characterization of SMA rotary actuator components in context of the SMA material, component processing, operational parameters and their intended use in applications.