Session: 04-23-01: Mechanics and Materials of Soft/Flexible/Stretchable Electronics

Paper Number: 116495

116495 - Characterizing the Shape Memory Behavior of Nitinol Wires in a Low Temperature Environment 

In 2018 scientists and engineers at NASA’s Glenn Research Center launched the Advanced Electric Bus (ALBus). It was the first Cube Satellite to use Nickel Titanium Alloy’s (NiTiNOL) shape memory effect to deploy solar arrays, and the mission highlighted the value of shape memory alloys throughout the planning, construction, and launch phases. Currently, there have been no publications on how temperatures colder than -60 degrees Celsius impact NiTiNOL’s shape memory effect. Given the extreme temperature gradients in space, particularly with the implementation of modern sunshields, a more comprehensive thermal characterization of the material will bolster the ability to accurately predict NiTiNOL performance.

The team is characterizing the permanent deformation of NiTiNOL wire as a function of bending strain at -80 degrees Celsius. This data is then compared to control tests performed at room temperature at the same bending strain rates. The team achieves consistent strain rates by bending the NiTiNOL wire 180 degrees around 3D printed molds with varying radius of curvatures. This step is completed at room temperature when the material is in its martensitic phase and monoclinic crystal lattice structure. The NiTiNOL is then cooled to -80 degrees Celsius in a freezer. The team constructed a device that uses a thermocouple to identify when the NiTiNOL wire reaches the desired temperature. When this occurs, a switch is activated and current passes through the wire. This causes resistive heating and initiates an austenitic phase transformation to a body centered cubic structure when the wire’s temperature rises above 40 degrees Celsius. During this process the team monitors the wire to ensure that the two-way shape memory effect does not interfere with the experimental goals. The team then images and processes the data to determine the final permanent deformation rates. The control tests are identical apart from not first cooling the wire.

The team expects that the extreme temperatures will have a significant retarding effect on the rate that the shape memory effect occurs. The temperature gradient of the NiTiNOL will be recorded for full exploitation, and these rates will be compared between samples with different strains. The team does not expect that the temperatures will impact the final deformation of the NiTiNOL wires, only the process which the material takes to get there. However, the permanent deformation rates will be compared to the control to see if there was an effect. The team also expects that there will be an exponential increase in permanent deformation as the bending strain in the wire is increased.

Presenting Author: Daniel Noel University of Southern Maine

Presenting Author Biography: Dan is an undergraduate Mechanical Engineering junior at the University of Southern Maine (USM). He served for eight years in the US military from 2012-2020 as an intelligence analyst. Since then, he has been pursuing his engineering education and is involved in a myriad of research projects that include USM's CubeSat program, and is also creating new laboratory experiences for the engineering curriculum.

Authors:

Daniel Noel University of Southern Maine
Asheesh Lanba N/A