Thomas Georges

Design of Shape Memory Alloy Actuators for Morphing Laminar Wing With Flexible Extrados

An active structure of a morphing wing designed for subsonic cruise flight conditions is composed of three principal subsystems: (1) fexible extrados, (2) rigid intrados, and (3) an actuator group located inside the wing box. The four-ply laminated composite flexible extrados is powered by two individually controlled shape memory alloy (SMA) actuators. Fulfilling the requirements imposed by the morphing wing application to the force-displacement characteristics of the actuators, a novel design methodology to determine the geometry of the SMA active elements and their adequate assembly conditions is presented. This methodology uses the results of the constrained recovery testing of the selected SMA. Using a prototype of the morphing laminar wing powered by SMA actuators, the design approach proposed in this study is experimentally validated.

Morphing laminar wing with flexible extrados powered by shape memory alloy actuators

An active structure of a morphing wing designed for subsonic cruise flight conditions combines three principal subsystems: (1) flexible extrados, (2) rigid intrados and (3) an actuator group located inside the wing box. A structural model of the flexible extrados built with ANSYS finite element software is coupled with X’Foil fluid dynamics software to evaluate mechanical and aerodynamic performances of the morphing wing in different flight conditions. Using the multicriteria optimization technique, an active structure consisting of the 4-ply laminated composite flexible extrados powered by two individually controlled actuators is selected. Shape memory alloy (SMA) actuators are designed as power elements for the morphing wing. To meet the functional requirements of the application, the geometry of the SMA elements is calculated using the results of the constrained recovery testing of the selected material.Copyright

Characterization and design of antagonistic shape memory alloy actuators

Antagonistic shape memory actuators use opposing shape memory alloy (SMA) elements to create devices capable of producing differential motion paths and two-way mechanical work in a very efficient manner. There is no requirement for additional bias elements to ?re-arm? the actuators and allow repetitive actuation. The work generation potential of antagonistic shape memory actuators is determined by specific SMA element characteristics and their assembly conditions. In this study, the selected SMA wires are assembled in antagonistic configuration and characterized using a dedicated test bench to evaluate their stress?strain characteristics as a function of the number of cycles. Using these functional characteristics, a so-called ?working envelope? is built to assist in the design of such an actuator. Finally, the test bench is used to simulate a real application of an antagonistic actuator (case study).

Experimental Bench for Shape Memory Alloys Actuators Design and Testing

Shape memory alloys (SMAs) are used as active elements in novel actuation devices. Two generic types of SMA actuators can be distinguished according to the type of bias passive-bias actuators where an elastic component serves as a bias and active-bias actuators where two SMA elements are connected together. This paper describes an experimental testing bench developed for the characterization of SMA active elements and their testing in a real actuation environment. The characterization of SMA active elements is performed under three complementary testing modes: (a) constant-stress, (b) fixed-support, and (c) elastic-bias recovery modes. Force, displacement and temperature data acquired during testing of a given SMA active element are then used to assess the mechanical work-generation potential of this active element and, ultimately, for the design of an SMA actuator containing this element. Finally, a case study is presented to illustrate the experimental design methodology and results.

Design of active bias SMA actuators for morphing wing applications

Shape Memory Alloys (SMAs) can provide compact and effective actuation for a variety of mechanical systems. Generally speaking, SMA-driven actuator systems can be divided into three subsystems: a) SMA active element, b) the transmission and c) a bias element. In respect to the type of bias, two actuator configurations can be distinguished: passive bias actuators where the SMA active element is coupled with an elastic bias element (spring), and active bias actuators in which two SMA active elements are connected together. This work is focused on designing an SMA actuator using active bias elements for morphing wing applications. Keywords: SMA actuator, active bias, antagonist, design, morphing wing

Functional Properties of Nanostructured Ti-Ni SMA Produced by a Combination of Cold, Warm Rolling and Annealing

In this study, different combinations of cold and warm rolling routes are compared to determine the processing conditions that will best allow the production of nanostructured Ti-Ni shape memory alloy, while reducing mechanical damage from rolling and enhancing the material texture. The processed alloy is characterized using stress-free strain recovery and constrained stress recovery techniques, both in static and cyclic regimes. The results of such a comparative functional characterization of nanostructured Ti-Ni alloy obtained by five different manufacturing routes are discussed.

Wind-Tunnel Testing of Shape Memory Alloys Actuators as Morphing Wing Driving Systems

A morphing wing, composed of flexible extrados, rigid intrados and a Shape Memory Alloys (SMA) actuator group located inside the wing box, is used to adapt an airfoil profile to variable flight conditions. The SMA actuator group developed for the morphing wing prototype consists of three main subsystems: the SMA active element, the transmission system, and the passive bias element. The functional requirements for the actuator group were determined using a coupled fluid-structure model of the flexible extrados. An original design approach was applied to determine the geometry and assembly conditions of the SMA active elements. For validation purposes, the morphing wing powered by SMA actuators was tested in a wind tunnel under subsonic flight conditions (Mach = 0.2 to 0.3 and α = −1 to 2°). The ability of the actuator group to move the flexible extrados up to 8 mm of vertical displacement and to bring it back to the initial profile has been successfully proven for all of the wind tunnel testing conditions. During the repetitive actuation, the force, displacement and temperature of the SMA active elements were measured and the results obtained in the force-displacement-temperature space were used to validate the SMA performances predicted during the design phase.Copyright