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Daytona Beach


Aerospace Engineering

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Shape-memory alloys (SMAs) have been used in many engineering applications because of their shape-memory effect and pseudoelasticity. SMA behavior is well understood under steady and constant temperature and loading conditions, whereas transient and non-ideal conditions effects should be further investigated. In this research, SMA torque tubes are studied for use in thermal management applications as self-regulated actuators responding to a process fluid with changes in temperature, with the goal of improved system efficiency by keeping components at an optimal temperature. When utilized in a thermal management configuration, it is likely that the SMA’s thermal environment will be different than that to which it was trained for, leading to challenges from a modeling standpoint. Process fluid transients lead to temperature fluctuations in the SMA, which may not be negligible in a self-regulated system. Similarly, without perfect insulation of the SMA, a temperature gradient (potentially both along the length and along the thickness) will occur when the SMA is subject to a different boundary condition than what they were trained for (steady isothermal). Empirical efforts have shown that this leads to deviations from expected behavior, challenging the modeling of an open-loop system. This study looks at Nitinol (Nickel-Titanium alloy) rotational actuator tubes, with the goal further understanding the non-ideal conditions for a future model system. The SMA tube was subjected to both insulated and natural convection boundary conditions, with low and high mass flow rates for both heating and cooling cases. The one-dimensional model was compared to experiments as well as a modified thermal model to help improve modeling efforts. Experimental efforts show that a convection boundary leads to temperature gradients, especially at high temperatures and low flow rates. Thermal modeling showed no significant variation along the thickness, mostly due to the small thickness of the tube.

Publication Title




American Institute of Aeronautics and Astronautics


Chicago, IL & Virtual

Paper Number

AIAA 2022-3372