The properties of Shape Memory Alloy (SMA) wires are determined by experimentation, and previously used experimental equipment contributes to measurement errors in data. In this study, various characterization experiments are designed and carried out using a precision characterization instrument for shape memory alloy wires to determine the properties and parameters of the alloy. These experiments demonstrate the behavior of SMA wires under different thermal and loading conditions as they occur in actuation applications.
As SMA wires go through phase transformation, a significant amount of contraction force is produced. This actuation force has been used in bias spring actuators and differential actuators. In this dissertation, the force generated during the twinning of martensite is used to actuate positioning systems with small displacements at the micrometer level. A micropositioning system is designed and tested that has a positioning accuracy of about ±0.15 μm. A relation between the current input and the displacement output is determined for the specific preload.
The transformation force generated during the phase change from martensite to austenite is used as an actuation force for a second positioning system that uses linear bearing with a displacement range of about a millimeter. This positioning system actuated with a single nitinol wire and guided by symmetric parallel diaphragm flexures, was designed and tested. The actuation is repeatable to about ±15 μm with variation of about ±5 μm in postion at steady temperature.
|Advisor:||Vallance, R. Ryan|
|Commitee:||Garris, Charles A., Kaufman, Roger E., Mittal, Rajat, Zara, Jason M.|
|School:||The George Washington University|
|Department:||Mechanical and Aerospace Engineering|
|School Location:||United States -- District of Columbia|
|Source:||DAI-B 69/08, Dissertation Abstracts International|
|Subjects:||Mechanical engineering, Materials science|
|Keywords:||Actuator, Mesopositioning, Micropositioning, Nitinol, Positioning systems, SMA precision characterization, Shape memory alloy wires|
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