As the aerospace sector aims to decrease its greenhouse gas emissions from historical levels, vehicle lightweighting is seen as key to achieving meaningful reductions in the sector. Shape memory alloy (SMA) materials have been shown to have extremely high work density that, when applied in an actuator, can yield significant weight savings compared to electric motor and hydraulic powered alternatives.

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.

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 a discrete output range. With their compact form factor and high energy density, SMA rotary actuators can often be directly integrated into or near a hinge line reducing the need for complex kinematics (e.g., linkages and gears) that are typically required to transfer the work from a rotary actuator’s output to an effector such as a flap or aileron. Boeing has executed high technology readiness level (TRL) demonstrations and production use of scalable SMA rotary actuation technology across several size scales and aeronautical platforms. Applications range from wind tunnel models to full-scale laboratory demonstrators and flight tests. Successful demonstrations include reconfigurable vortex generators, actuated wind tunnel models, adaptive trailing edges, power door opening systems, spanwise adaptive wings, variable area nozzles and variable geometry structures.