The incessant quest for more efficient aircraft has driven research into the development of aircraft with morphing wings. This concept aims to increase the flight efficiency of the aircraft by adapting the wing to the present air flow condition. This technology still has some limitations, among them the control mechanism of the shape adaptation mechanism. Some researchers have proposed the application of intelligent materials as alternative to conventional drive systems. Particularly shape memory alloys (SMAs) have been investigated due to their ability to recover large deformations if subjected to a suitable temperature (simple drive mechanism by Joule heating). This work presents a thermomechanical characterization of NiTi SMA micro-springs for application in morphing wings. The actuators work in a regime where the shape memory effect is created by heating of the stress-induced martensite phase, a phenomenon little explored in the literature. An adaptive wing prototype was constructed; the variation in camber deflection is the response of actuator heating by the Joule effect. A 3D wing prototype was tested in a wind tunnel under different air flows, showing the suitability of the actuators for this application. Next, the behavior of these spring actuators when subjected to force and strain under realistic conditions is discussed based on the phase transformation temperatures and the actuator response to heating. These results are fundamental for choosing the actuator size for a particular application and for the parameterization of controllers.
Shape memory alloys have recently gained attention for applications in motor driving components. The most expressive advantage of shape memory alloy components in that type of application is the high torque to motor weight ratio. Considering the importance of these studies, this article presents the design, manufacture, and theoretical and experimental analyses of a rotary motor driven by Ni–Ti shape memory alloy mini springs. The adopted motion mechanism allows the motor to run in continuous and bidirectional rotation mode, where speed and torque are determined by a drive sequence. A simplified analytical model was implemented, considering the thermomechanical characteristics of the shape memory alloy springs. Experimental tests with and without electrical drives were performed using properly designed electronic measurement instrumentation. The principal scientific contribution of this work is the demonstration of the motor’s functionality and torque generation. An energy density index of 1.41 × 10−3 Nmm/mm3 was attained, which is higher to those of other similarly constructed motors in the literature.
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