Session: 02-02: Shape Memory Alloy Actuator Material and Characterization Standards

Paper Number: 111147

111147 - Standard Test Methods for Shape Memory Alloys for Actuation 

Many promising aeronautical applications using shape memory alloy (SMA) based actuators have been proposed, developed and even demonstrated in flight tests. Approved test methods are needed to support the transition of these prototype demonstration to commercial flight applications. With this in mind, a committee was formed under the Aerospace Vehicle Systems Institute (AVSI) with members from industry, government and academia to develop and publish standard test methods that are specifically intended to measure SMA actuation properties. Under this committee standard test methods for Uniaxial Constant Force Thermal Cycling (UCFTC) and Uniaxial Pre-strain and Thermal Free Recovery (UPFR) were published under ASTM as E3097 and E3098, respectively. These two test methods capture the two most important responses in SMAs for actuation, which is load-biased shape memory effect and classical shape memory effect. These test methods measure the transformation properties including transformation temperatures, actuation strain and residual strain to provide data for the characterization and selection of SMA materials, quality control, design allowables and actuator design.

Additional test methods are still needed to fully support the transition of SMA actuators to production use. First, rotary SMA actuation has been demonstrated as a practical and valuable actuator form as highlighted recently during flight test of reconfigurable vortex generators and in actuated wind tunnel models. Second, there is a need for a test method that defines and characterizes functional and structural fatigue and failure during repeated UCFTC. The objective of this test method is to address failure with regard to the SMA material’s ability to perform in an actuation application for the application’s required lifecycle. This is to be distinguished from conventional material fatigue and failure due to fracture. To this end, two new test methods have been proposed for Constant Torque Thermal Cycling (CTTC) and Force Controlled Repeated Thermal Cycling (FCRTC) of SMA. To manage this broader effort, an ASTM task group (E08.05.10 – Shape Memory Alloys for Actuation), in association with AVSI and the Consortium for the Advancement of Shape Memory Alloy Research and Technology (CASMART), was formed to develop standards for characterizing the thermomechanical behaviour and material properties of SMAs subject to thermally induced phase change. This presentation will cover the recent development of CTTC and FCRTC including their methodology and examples of their use.

Presenting Author: Douglas Nicholson Boeing

Presenting Author Biography: Dr. Doug Nicholson currently resides as a technical lead engineer in Boeing Research and Technology (BR&T) on the Integrated Vehicle Systems (IVS) team. His current work focuses on the development and transition of smart materials and adaptive structures for aerospace applications. These activities include standards development, material development and processing, advanced manufacturing, design optimization, system integration, and wind tunnel testing to sub and full-scale flight demonstrations. Doug earned his Ph.D. in mechanical engineering from the University of Central Florida (UCF) in 2017, M.S. in aerospace engineering from UCF in 2011 and B.S. in mathematics and physics from Florida Atlantic University in 2008.