Overview and future advanced engineering applications for morphing surfaces by Shape Memory Alloy Materials

The development of structures able to autonomously change their characteristics in response to an external simulation is considered a promising research field. Indeed, these structures, called smart structures, can be adopted to improve the aerodynamic performance of air and land vehicles. In this work, an overview and future applications of Shape Memory Alloys (SMA)-based smart structures are presented. The use of SMA materials seems to be very promising in several engineering sectors. Advanced SMA-based devices, designed to improve the aerodynamic performance of vehicles by modifying the shape of the spoiler and the rear upper panel, are briefly introduced and discussed in this paper. Indeed, a simplified model simulating the SMA mechanical behavior has been considered to demonstrate the feasibility of the introduced smart structures for adaptive aerodynamic applications. Numerical simulations of the investigated structures are provided as a justification of the proposed designs

Simultaneous use of shape memory alloys and permanent magnets in multistable smart structures for morphing aircraft applications

This Thesis considers the simultaneous use of shape memory alloys and permanent magnets for achieving multistable smart structures aiming towards morphing applications. Motivation for this approach lies in the poor energetic efficiency of shape memory alloys, which can void system-level benefits provided by morphing technologies. Multistability can therefore be adopted to prevent continuous operation of shape memory alloy actuators. Objectives of the study involve the combination of shape memory alloys and permanent magnets in new geometrical arrangements to achieve multistable behavior; the development of a numerical modeling procedure that is able to simulate the multi-physics nature of the studied systems; and the proposal of a geometric arrangement for morphing applications that is based on a repeating pattern of unit cells which incorporate the combined use of shape memory alloy wires and permanent magnets for multistability. The proposed modeling strategy considers a geometrically nonlinear beam finite element; a thermo-mechanical constitutive behavior for shapememoryalloys;theinteractionofcuboidalpermanentmagnetswitharbitraryorienta- tions; and node-to-element contact. Experiments are performed with three distinct systems, including a proof-of-concept beam, a three cell morphing beam metastructure, and a morphing airfoil prototype with six unit cells. Results show that the combination of shape memory alloys and permanent magnets indeed allows for multistable behavior. Furthermore, the dis- tributedactuationcapabilitiesofthe morphingmetastructureallowforsmoothandlocalized geometrical shape changes.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorCNPq - Conselho Nacional de Desenvolvimento Científico e TecnológicoTese (Doutorado)Esta Tese considera o uso simultâneo de ligas com memória de forma e ímãs permanentes para a obtenção de estruturas inteligentes multiestáveis, com vistas a sua aplicação em aeronaves de geometria variável. A motivação para tal abordagem reside na baixa eficiência energética associada às ligas com memória de forma, a qual pode eliminar benefícios oriundos de tecnologias relacionadas a geometria variável. Multiestabilidade pode, desta forma, ser adotada para prevenir operação contínua de atuadores baseados em ligas com memória de forma. Objetivos do estudo envolvem a combinação de ligas com memória de forma e ímãs permanentes em novos arranjos geométricos para a obtenção de comportamento multiestável; o desenvolvimento de um procedimento de modelagem numérica que pode simular a natureza multifísica dos sistemas estudados; e a proposição de um arranjo geométrico para aplicações que envolvem geometria variável, o qual é baseado num padrão repetitivo de células unitárias que incorporam o uso combinado de ligas com memória de forma e ímãs permanentes para mul- tiestabilidade. A estratégia de modelagem proposta considera um elemento finito de viga com não-linearidades geométricas; um modelo constitutivo termomecânico para ligas com memória de forma; a interação entre ímãs permanentes cúbicos com orientação arbitrária; e contato entre elemento-e-nó no contexto de elementos finitos. Experimentos são realizados com três sistemas distintos, incluindo uma viga para prova de conceito, uma metaestrutura do tipo viga com geometria variável composta por três células unitárias, e um protótipo de aerofólio com geometria variável composto por seis células unitárias. Resultados mostram que a combinação de ligas com memória de forma e ímãs permanentes permite a obtenção de comportamento multiestável. Além disso, a característica de atuação distribuída das metaestruturas com geometria variável permite alterações de forma suaves e localizadas

Smart Material Wing Morphing for Unmanned Aerial Vehicles.

Morphing, or geometric adaptation to off-design conditions, has been considered in aircraft design since the Wright Brothers’ first powered flight. Decades later, smooth, bio-mimetic shape variation for control over aerodynamic forces still remains elusive. Unmanned Aerial Vehicles are prime targets for morphing implementation as they must adapt to large changes in flight conditions associated with locally varying wind or large changes in mass associated with payload delivery. The Spanwise Morphing Trailing Edge (SMTE) concept is developed to locally vary the trailing edge camber of a wing or control surface, functioning as a modular replacement for conventional ailerons without altering the wing’s spar box. The SMTE design was realized utilizing alternating active sections of Macro Fiber Composites (MFCs) driving internal elastomeric compliant mechanisms and passive sections of anisotropic, elastomeric skin with tailorable stiffness, produced by additive manufacturing. Experimental investigations of the modular design via a new scaling methodology for reduced-span test articles revealed that increased use of more MFCs within the active section did not increase aerodynamic performance due to asymmetric voltage constraints. The comparative mass and aerodynamic gains for the SMTE concept are evaluated for a representative finite wing as compared with a conventional, articulated flap wing. Informed by a simplistic system model and measured control derivatives, experimental investigations identified a reduction in the adaptive drag penalty up to 20% at off-design conditions. To investigate the potential for augmented aeroelastic performance and actuation range, a hybrid multiple-smart material morphing concept, the Synergistic Smart Morphing Aileron (SSMA), is introduced. The SSMA leverages the properties of two different smart material actuators to achieve performance exceeding that of the constituent materials. Utilizing the relatively higher work density and phase transformation of Shape-Memory Alloys combined with the larger bandwidth and conformal bending of MFCs, the resultant design is demonstrated to achieve the desired goals while providing additional control authority at stall and for unsteady conditions through synergistic use of reflex actuation. These advances highlight and motivate new morphing structures for the growing field of UAVs in which adaptation involves advanced compliance tailoring of complex geometry with synergistic actuation of embedded, smart materials.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111533/1/alexmp_1.pd

Design and Fabrication of Origami Elements for use in a Folding Robot Structure

The aim of the research is to investigate the methodology of the design and fabrication of folding robots that depend on the origami structures. The use of origami structures as a foundation to build reconfigurable and morphing robots that could assist in search and rescue (SAR) tasks are investigated. The design of the origami folding structures divided into three stages: consideration of the geometry of the origami structure, the hinge design, and the actuation system. The result of investigating three origami structures shows the ability to use the unit cell of the origami ball structure as a self-folding element. Furthermore, the novel type of origami structure for manipulation was created according to this result. This novel structure was designed to be a soft manipulation robot arm. Two approaches are used to design and fabricate flexure hinge. The first is by using a 3D printed multi-material technique. By this technique, the hinge printed using soft and solid material at the same time, which is Tango plus flx930 for soft material and Vero for solid material. The soft material act as a flexure hinge. Therefore, three tests were operated for it to calculate the tensile force, fatigue limit, and the required bend force. The second approach is by using acrylic and Kapton materials. Two types of actuation systems were studied: the external actuation system and embedded actuation system. The external actuation system was used for the Origami structure for manipulation, while the embedded actuation system was used for the self-folding structure. The shape memory alloy wires in torsion (TSW) and bending (BSW) was used in an embedded actuation system. A unit cell of origami ball was fabricated as a self-folding element by using three approaches: manually, acrylic, and Kapton and 3D printing. It is actuated by using shape memory alloy wire. Furthermore, an origami structure for manipulation was fabricated and actuated using an external actuation system. This novel type of origami structure provided an excellent bend motion ability

Shape memory alloy based 3D printed composite actuators withvariable stiffness and large reversible deformation

Soft composite actuators can be fabricated by embedding shape memory alloy (SMA) wires into soft poly- mer matrices. Shape retention and recovery of these actuators are typically achieved by incorporating shape memory polymer segments into the actuator structure. However, this requires complex manufac- turing processes. This work uses multimaterial 3D printing to fabricate composite actuators with variable stiffness capable of shape retention and recovery. The hinges of the bending actuators presented here are printed from a soft elastomeric layer as well as a rigid shape memory polymer (SMP) layer. The SMA wires are embedded eccentrically over the entire length of the printed structure to provide the actuation bending force, while the resistive wires are embedded into the SMP layer of the hinges to change the temperature and the bending stiffness of the actuator hinges via Joule heating. The temperature of the embedded SMA wire and the printed SMP segments is changed sequentially to accomplish a large bending deformation, retention of the deformed shape, and recovery of the original shape, without applying any external mechanical force. The SMP layer thickness was varied to investigate its effect on shape retention and recovery. A nonlinear finite element model was used to predict the deformation of the actuators

Microgripper design and evaluation for automated µ-wire assembly: a survey

Microgrippers are commonly used for micromanipulation of micro-objects from 1 to 100 µm and attain features of reliable accuracy, low cost, wide jaw aperture and variable applied force. This paper aim is to review the design of different microgrippers which can manipulate and assemble µ-wire to PCB connectors. A review was conducted on microgrippers’ technologies, comparing fundamental components of structure and actuators’ types, which determined the most suitable design for the required micromanipulation task. Various microgrippers’ design was explored to examine the suitability and the execution of requirements needed for successful micromanipulation

Design of a composite morphing wing

Morphing aircraft components can increase the possibility of optimising the performance of an aircraft at various flight conditions. A morphing aircraft wing can change the wing shape to modify the lift and drag distribution on the wing surface, allowing the lift-to-drag ratio to be tailored to the desired performance. A camber morphing and a trailing edge morphing wing changes the aerodynamic lift by altering the camber and by deflecting the wing trailing edge, potentially reducing the aerodynamic drag by eliminating the gaps; which exist between the main wing and the control surfaces of a conventional wing. Among the technology used to achieve camber morphing and trailing edge morphing, were mechanical and smart actuations, such as piezoelectrics and shape memory alloys (SMAs). Compliant structures, cellular structures, shape memory polymers, and multi-stable structures were exploited to improve the flexibility of the aerofoil sections or wings. SMA wires were one of the smart actuators which had been extensively utilised to morph various aerofoils/wings, mainly due to the high actuation force and compatibility, which reduce the volume and weight of the actuators and the complexity of moving mechanical components. In this research, a user defined material model (UMAT) was developed within the explicit LS-DYNA FE code, for NiTi shape memory alloy (SMA) wires, and used for actuation of the composite morphing wing. The Tanaka SMA constitutive model was implemented in MATLAB and FORTRAN codes for the SMA-actuation of various structures. The UMAT was used to simulate actuations of various complex morphing structures, including several aluminium and composite aerofoils with corrugated sections, and a pre-curved corrugated plate. Actuations of the two aluminium aerofoils, with corrugated sections in the lower surface and the middle cantilever section, by a 0.5mm-diameter SMA wire with a maximum recoverable strain or a pre-strain of 1.6%, resulted in trailing edge (TE) deflections of 7.8 mm and 65.9 mm, respectively. Actuation of the carbon fibre (CF) composite aerofoil, with the corrugated section as a middle cantilever section, and with 8 layers of CF in ±45° directions, produced a TE deflection of 52.0 mm. To demonstrate the SMA-actuated morphing concept, a composite 3D-printing technology was explored to manufacture a carbon fibre (CF) composite structure, consisted of a flat vertical front plate, a corrugated section, and a rear trailing edge (TE) section. Due to the nature of 3D-printing, two layers of CF were 3D-printed along the circumference of the corrugation and the TE section, and the minimum thickness of the structure was 3 mm. Experimentally, actuation of the CF composite corrugated structure by a NiTi SMA wire with a diameter of 0.2 mm and a pre-strain of 4.77%, and with a diameter of 0.5 mm and a pre-strain of 1.68%, aligned in the chordwise direction, resulted in 1.1 mm and 6.0 mm TE deflections, respectively. Cyclic tests (10 and 30 cycles) of the actuation of the CF composite corrugated structure showed the TE deflection converged after few cycles. A 1.25m-span composite morphing wing was finally designed and manufactured, consisted of a CF composite D-nose spar which resisted the main aerodynamic loading, and rear sections which were made of rigid and flexible foams. CF composite spar flanges, spar web, front and rear ribs, were 3D-printed, and were assembled with a CF composite skin which was autoclave-manufactured, to form the CF composite D-nose spar. Sections of rigid and flexible foams were CNC-machined and were attached to the front CF composite D-nose spar, 3D-printed long rear ribs, trailing edge sections and the morphed corrugated structure, to form a complete composite morphing wing.Open Acces

Advanced design and control concepts for actuators based on shape memory alloy wires

Intelligente Materialien eröffnen durch ihre einzigartigen Formfaktoren ganz neue Designmöglichkeiten und ihre Eigenschaft, Aktorik mit Sensorik zu kombinieren, kann in multifunktionalen Systemen zu bisher ungenutzten Mehrwerten führen. Gleichzeitig führt die hiermit verbundene Komplexität zu neuen Herausforderungen bei der Entwicklung und Ansteuerung von Systemen, sodass es bisher trotz der Vielzahl an Vorteilen noch vergleichsweise wenige kommerzielle Produkte gibt. Diese Dissertation setzt sich als Ziel, diese Herausforderungen zum einen durch die Entwicklung einer systematischen Konstruktionsmethodik als auch durch die beispielhafte Illustration von Konstruktionslösungen anzugehen. Sie konzentriert sich dabei speziell auf das Technologiefeld der Formgedächtnislegierungen (FGL) und erläutert nach einer grundlegenden Einführung in den Entwurf von FGL-Aktorsystemen die intelligente Kopplung von FGL-Aktordrähten mit bistabilen, nichtlinearen Federelementen. Durch diese Kombination lassen sich die oft zitierten Nachteile von FGL – langsame Aktuierung und Energieineffizienz – für viele Anwendungen eliminieren. Ein zweiter Weg zu hoher Geschwindigkeit und Energieeffizienz liegt in der Ansteuerung mit Pulsen bei hohen elektrischen Spannungen. Zusammenfassend zeigt diese Arbeit innovative und gleichzeitig systematische Konzepte zur Entwicklung von FGL-Aktoranwendungen auf und möchte damit einen Beitrag zur weiteren zukünftigen Verbreitung dieser noch jungen Technologie leisten.Versatility and variability in form factor of smart materials, combined with their actuation and sensing abilities, allow for the design and construction of multifunctional systems. These systems add value to industrial and consumer products. Despite the considerable number of advantages, only a few smart-material-based actuator-sensor-systems are commercially available, mainly due to challenges in design, fabrication, and control of these materials. This dissertation attacks these challenges by providing a systematic design framework, as well as exemplary illustrations of design solutions. Special focus of this work is on the technological field of shape memory alloys (SMA). After a basic introduction to the design of SMA actuator systems, the intelligent combination of SMA actuator wires with bi-stable, nonlinear spring elements is described. This combination eliminates oftentimes-quoted disadvantages of SMAs – slow actuation and energy-inefficiency – for a wide range of applications. A second approach for the realization of high-speed actuation and energy-efficiency is the activation of SMA wires with high voltage pulses, which leads to actuation times in the millisecond-range and energy-savings up to 80 % in comparison to the suppliers’ recommendations. In summary, this thesis demonstrates innovative, and at the same time systematic concepts for the design and control of SMA actuator systems. Thus, it aims at contributing to future spreading of this still young technology

Martensitic Thin Wires under Restrained Recovery: Theoretical and Experimental Aspects

A one-dimensional model for the evolution of microstructure in single crystal shape memory wires has been recently proposed in (Rizzoni (2011)). The model is based on the constrained theory of martensite introduced by (Ball et al. (1995); De Simone and James (2002)) and on the assumption that stable equilibrium configurations are deformations lying at the energy wells on most parts of the wire. In this paper we compare the response simulated for restrained recovery conditions (Rizzoni (2011)) with experimental data obtained in restrained recovery tests performed on NiTi wires. As an application, we consider a truss made of shape memory wires and rigid elements, and we calculate its deformation after thermal activation of the shape recovery

A cooling system for s.m.a. (shape memory alloy)based on the use of peltier cells

The aim of this thesis has been the study and the implementation of an innovative cooling system for S.M.A. (Shape Memory Alloy) material by using a Peltier cell. This system has demonstrated a consistent cooling time reduction during the application and so that the solution adopted has confirmed that it can be used for a better operability of the S.M.A. material during the cooling phase. After an accurate selection of possible cooling system to be adopted on these materials the better choice in terms of efficiency and energy consumption reduction has converged on Peltier cell design development. In this context for our research three investigation have been conducted. The first one has concerned an analytic investigation in order to understand the phenomenology and the terms involved during the heat exchange. After this study a numerical investigation through a Finite Element approach by commercial software has been carried out. Also an experimental investigation has been conducted, at the CIRA Smart Structure Laboratory, in order to verify the results obtained by the numerical prediction. The set-up with the Peltier cell used as heater and cooler of the S.M.A. has confirmed the soundness of the solution adopted. Finally, a correlation between numerical and experimental results have been presented demonstrating the validity of the obtained results through the developed investigations. This system, composed of Peltier cell has confirmed also an energy consumption reduction because the cell has been used for heating and cooling phase without additional system as resistive system (Joule effect). This project shall be also industrial involvement in a new cost cut down point of vie