Standardization of Shape Memory Alloys from Material to Actuator

Development of standard specifications and test methods for shape memory alloys (SMAs) in the context of actuator materials and components are outlined. A material specification centers on mill product wrought NiTi or NiTi + X + X′ based alloys, where X and X′ can be any alloying element addition to the base NiTi. This standard is aimed toward specifying the chemical, mechanical, thermal, and metallurgical requirements of NiTi-based alloys. Two newly proposed standard test methods are aimed toward expanding the applicability of the following published SMA actuator standards: E3097—Standard Test Method for Uniaxial Constant Force Thermal Cycling (UCFTC) and E3098—Standard Test Method for Uniaxial Pre-strain and Thermal Free Recovery (UPFR). First, Force-Controlled Repeated Thermal Cycling (FCRTC), addresses repeated thermal cycling under a constant force and associated terminology. FCRTC’s primary objective is to address failure with regard to the SMA material’s ability to perform its function as an actuator for an application’s required lifecycle. Second, Constant Torque Thermal Cycling (CTTC) deals with thermally cycling SMAs under a constant torque for rotary actuator applications. Key features of each proposed standard and progress on their development are outlined, considering novelty and applicability to actuation from raw material to final actuator component in its application.