Les propriétés thermomécaniques étonnantes des alliages à mémoire de forme (AMF) sont mises à profit dans de nombreux domaines. Ce matériau est capable de mettre en mouvement une structure suite à un changement de température. Or les façades de bâtiments contemporains, pour s’adapter à des conditions climatiques variables, doivent réguler le passage de la lumière et de l’énergie thermique, par exemple au moyen de systèmes motorisés. Le potentiel de fils AMF pour l’actionnement de protections solaires en façade est exploré ici. La modélisation du couplage mécanique induit par l’introduction de tels matériaux dans une structure a été peu étudiée : l’AMF agit sur la structure qui en retour modifie le comportement de l’AMF. La première étape de ce travail a consisté en une contribution à la modélisation du comportement thermomécanique de ce matériau reposant sur le choix d’une énergie libre, d’un potentiel de dissipation et de plusieurs variables internes. Deux modèles unidimensionnels ont été proposés : un premier modèle monocristallin reproduit de façon simplifiée le comportement du matériau, et un second modèle polycristallin propose une description plus fidèle. En parallèle un dispositif d’essai original à température contrôlée a été développé, il a permis une caractérisation fiable de fils Nickel-Titane et l’identification des paramètres des modèles. Dans un second temps ces modèles ont permis de résoudre des cas de couplage élémentaires (fil AMF + ressort, lame élastique + fil AMF noyé) pour des chargements thermomécaniques simples, et des solutions analytiques ont été établies. Les modèles ont été implémentés numériquement via un script matériau utilisateur (UMAT) pour le logiciel éléments finis ABAQUS et au moyen d’un algorithme d’optimisation sous contraintes. Ceci permet de simuler la réponse couplée de systèmes structuraux a priori quelconques intégrant des AMF, connectés à ou noyés dans, une structure. Dans un troisième temps, divers actionneurs ont été conçus, réalisés et testés dans le cadre de l’occultation solaire des façades. Le principe est d’utiliser un cycle de température permettant à l’AMF de déformer la structure, puis à l’énergie élastique de déformation de la structure d’assurer le retour à la forme originale. Le comportement réel de ces actionneurs a été comparé aux calculs analytiques et éléments finis. Des tests cycliques ont également été réalisés / The surprising thermomechanical properties of shape memory alloys (SMA) are harnessed in many engineering fields. This material is able to set a structure in motion upon a temperature change. Today, contemporary building facades must adapt to variable climate conditions as well as to evolving building use and occupancy. In particular, they must regulate light and thermal energy passing through the facade, with motorized systems, for example. We explore the potential of SMA wires for putting in motion solar shading devices in facades. The modelling of the mechanical coupling induced by the introduction of such materials in a structure has received little attention as of now. The SMA acts on the structure which in return modifies the SMA behavior. The first step of this work is a contribution to modelling the thermomechanical behavior of this material through the choice of a free energy, a dissipation potential and internal variables. We propose two one-dimensional models: a first monocrystalline model reproduces the material behavior in a simplified way, and a second polycrystalline model offers a more accurate description of it. An original temperature-controlled testing apparatus was developed in parallel. This led to a reliable characterization of Nickel-Titanium wires and the identification of the model parameters. In a second stage, these models allowed to solve elementary coupling cases (SMA wire + Spring, Elastic plate + Embedded SMA wire) for simple thermomechanical loadings and we established analytical solutions. The models were then numerically implemented via a user-material script (UMAT) for the finite elements software ABAQUS, by using a constrained optimization algorithm. This enables the simulation of the coupled response of, in principle, any structural system including SMA wires, connected or embedded in the structure. Finally, we designed, fabricated and tested different actuators in the context of sunlight control in facades. The working principle lies in using a temperature cycle which allows the SMA to deform the structure, and then allows the elastic strain energy in the structure to ensure the return to the original shape. The real behavior of these actuators have been compared to analytical and finite element calculations. We also performed cyclic tests

[pt] O estudo de materiais inteligentes tem instigado várias aplicações nas mais diversas áreas do conhecimento (da área médica à industria aeroespacial). Os materiais mais utilizados em estruturas inteligentes são as ligas com memória de forma, as cerâmicas piezoelétricas, os materiais magneto-estrictivos e os fluidos eletro- reológicos. Nas últimas décadas, as ligas com memória de forma vêm recebendo atenção especial, sendo utilizadas principalmente como sensores ou atuadores. Existe uma gama de fenômenos associados a estas ligas que podem ser explorados. Visando uma análise mais precisa do comportamento destes materiais, tem se tornado cada vez maior o interesse no desenvolvimento de modelos matemáticos capazes de descrevê-los de maneira adequada, permitindo explorar todo o seu potencial. O objetivo deste trabalho é propor um modelo constitutivo unidimensional que considera quatro variantes de microconstituintes (austenita, martensita induzida por temperatura, martensita induzida por tensão trativa e martensita induzida por tensão compressiva) e diferentes propriedades para cada fase. O efeito das deformações induzidas por temperatura é incluído na formulação. O modelo contempla ainda o efeito das deformações plásticas e o acoplamento entre os fenômenos de plasticidade e transformação de fase. Além disso, são introduzidas modificações na formulação que permitem o alargamento do laço de histerese da curva tensão-deformação, fornecendo resultados mais coerentes com dados experimentais. Por fim, incorpora-se a assimetria no comportamento tração-compressão. A validação do modelo é obtida comparando os resultados numéricos obtidos através do modelo com resultados experimentais encontrados na literatura para ensaios de tração a diferentes temperaturas e para a assimetria no comportamento tração- compressão. / [en] The study of intelligent materials has instigated many applications within the various knowledge areas (from medical field to aerospace industry). The most used materials in intelligent structures are the shape memory alloys (SMA), the piezoelectric ceramics, the magnetostrictive materials and the electrorheological fluids. In the last decades, SMAs have received special attention, being mainly used as sensors or actuators. There is a number of phenomena related to these alloys that can be explored. Aiming a more precise analysis of SMA behavior, the interest on the development of mathematical models capable of describing these phenomena properly has grown, allowing to explore all their potential. The aim of this work is to propose a unidimensional constitutive model which considers four microconstituent variants (austenite, martensite induced by temperature, martensite induced by tensile loading and martensite induced by compressive loading) and different material properties for each phase. The effect of thermal strains is included in the formulation. The model considers the effect of plastic strains and the plastic-phase transformation coupling. Besides, some changes are introduced in the formulation in order to enlarge the stress-strain hysteresis loop, resulting in better agreements with experimental data. Eventually, the tensioncompression asymmetry is incorporated. The model validation is obtained through the comparison between the numerical results given by the model and experimental results found in the literature for tensile tests at different temperatures and for tension- compression asymmetry.

Submitted by MARCELO FRANCISCO MAESTÁ null (mfmaesta@gmail.com) on 2017-02-22T00:41:17Z No. of bitstreams: 1 Tese MArcelo Francisco Maesta.pdf: 11803249 bytes, checksum: c99c02808167e733ec292281a2b8c183 (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-02-24T18:06:13Z (GMT) No. of bitstreams: 1 maestra_mf_dr_ilha.pdf: 11803249 bytes, checksum: c99c02808167e733ec292281a2b8c183 (MD5) / Made available in DSpace on 2017-02-24T18:06:13Z (GMT). No. of bitstreams: 1 maestra_mf_dr_ilha.pdf: 11803249 bytes, checksum: c99c02808167e733ec292281a2b8c183 (MD5) Previous issue date: 2016-12-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A busca por aeronaves capazes de modificar sua geometria melhorando suas características aerodinâmicas incentivou diversos autores a sugerirem modelos de asas adaptativas. Tais modelos utilizam atuadores leves de modo a substituir os atuadores clássicos convencionais sem, no entanto, comprometer a e ciência de voo da aeronave. Dentre os materiais utilizados para isto se destacam as ligas de memória de forma (Ni-Ti), que são capazes de converter energia térmica em energia mecânica e, uma vez deformadas, podem retornar a sua condição original de forma através de seu aquecimento. Neste contexto, o presente trabalho objetiva controlar a posição angular de um aerofólio utilizando para isto um par de os de liga de memória de forma. No modelo de asa proposto, deseja-se estabelecer uma forma para o per l aerodinâmico a partir da determinação de um ângulo entre duas seções da asa. Este ângulo é atingido pelo efeito de memória de forma da liga através da passagem de uma corrente elétrica. A função da corrente elétrica é alterar a temperatura dos atuadores através do efeito Joule, modificando a forma da liga. Devido à presença de efeitos não-lineares, principalmente no modelo matemático da liga, propõe-se a aplicação de controladores não-lineares do tipo liga-desliga. / The search for aircraft capable of modifying its geometry improving its aerodynamic characteristics, encouraged several authors to suggest models of adaptive wings. These models use lightweight actuators to replace conventional classic actuators without, however, compromise aircraft flight efficiency. Shape Memory Alloys (SMA) can be used efficiently for this application. These materials are capable of converting thermal energy into mechanical energy and a deformed time, can return to its original condition so through its heating. The current work aims to control the angular position of an airfoil using a couple of alloy wires of shape memory. In the proposed wing model, it is desired to establish a way for the aerodynamic pro le of the determination of an angle between two sections of the wing. This angle is attained by the alloy shape memory effect by passing an electric current. The function of the electric current is to change the temperature of the actuators through the Joule effect, modifying the shape of the shape memory alloy. Due to the presence of non-linear effects, especially in the mathematical model of the alloy, it proposes the application of nonlinear controllers type on-of

Les travaux de recherches développés dans cette thèse concernent la réalisation de couchesminces, à partir de l’alliage à mémoire de forme (AMF) NiTi mécanoélaboré et de structurenanocristalline, en vue de leur intégration dans des microsystèmes. Le but est d’améliorer lespropriétés AMF de leurs homologues de structure microcristalline, dits conventionnels.Les techniques de caractérisation physico-chimiques (DRX, MET, MEB) nous ont permisd’une part, de suivre le mécanisme de formation de l’intermétallique B2-NiTi en fonction dutemps de broyage et d’autre part, de déterminer les paramètres microstructuraux à savoir, lataille des cristallites, le taux de microdéformations et la densité de dislocations des élémentspurs ainsi que ceux de la phase B2-NiTi. Ces paramètres révèlent le caractère nanocristallin etdésordonné des poudres broyées.Par ailleurs, nous avons fabriqué pour la première fois une cible B2-NiTi de structurenanocristalline, par l’intermédiaire d’une méthode alternative (mécanosynthèse et procédé deprojection à froid).Nous avons montré également qu’il est possible de déposer sous forme de couche mincel’intermétallique NiTi nanostructuré. Ce film mince d’épaisseur 447 nm a été déposé parpulvérisation cathodique à magnétron à partir de la cible élaborée par projection à froid (coldspray). / The research work developed in this thesis is related to preparing a thin film of NiTi shapememory alloy used to integrate into microsystems. The goal is to improve the properties oftheir counterparts of microcrystalline structure (conventional target).Physical and chemical techniques of characterization (XRD, TEM and SEM) have allowed onthe one hand, to follow the mechanism of intermetallic NiTi formation as a function ofmilling time and on the other hand, to determine the microstructural parameters : crystallitesize, the microstrain and dislocation density of the pure elements and the B2-NiTi phase.These parameters reveal the character of the disordered nanocrystalline of the milled powders.Furthermore, we fabricated a target of B2-NiTi nanocrystalline structure by an alternativemethod (mechanical alloying and cold spray).We also showed that it is possible to deposit the nanocrystalline NiTi intermetallic thin film.This film with a thickness of about 447 nm was deposited by magnetron sputtering techniquefrom the NiTi target.

The utilization of ferromagnetic shape memory alloys (FSMAs) in small scale devices has attracted considerable attention within the last decade. However, the lack of sufficient studies on their reversible shape change mechanisms, i.e, superelasticity, magnetic field-induced martensite variant reorientation and martensitic phase transformation, at the micron and submicron length scales prevent the further development and the use of FSMAs in small scale devices. Therefore, investigating the size effects in these mechanisms has both scientific and technological relevance. Superelastic behavior of Ni54Fe19Ga27 shape memory alloy single crystalline pillars was studied under compression as a function of pillar diameter. Multiple pillars with diameters ranging between 200 nm and 10 µm were cut on a single crystalline bulk sample oriented along the [110] direction in the compression axis and with fully reversible two-stage martensitic transformation. The results revealed size dependent two-stage martensitic transformation which was suppressed for pillar sizes of 1 µm and below. We also demonstrated that the reduction in pillar diameter decreases the transformation temperature due to the difficulty of martensite nucleation in small scales. Size effects in the magnetic field-induced martensite variant reorientation were investigated in the Ni50Mn28.3Ga21.7 single crystals oriented along the [100] direction of the austenite phase. Single crystalline compression pillars were fabricated on the martensite twins between the sizes of 630 nm and 20 µm. It was found that the stress-induced and magnetic field-induced martensite variant reorientation are size dependent and became more difficult with the reduction in sample size. Surprisingly, it was still possible to magnetically activate the shape change in the micropillars which indicates the fact that magnetocrystalline anisotropy energy increases with the reduction in sample dimensions. Ni45Mn36.6Co5In13.4 pillars between the 600 nm and 10 µm diameters were investigated along the [100] direction of the austenite to study the size effects in the magnetic field-induced phase transformation (MFIPT). MFIPT was obtained down to 5 µm size in these pillars with reasonable magnetic field levels similar to their bulk counterparts.

Shape memory alloys (SMAs) provide exciting opportunities for miniature actuation systems. As SMA actuators are scaled down in size, cooling increases and bandwidth, improves. However, the inclusion of a bias element with which to cycle the SMA actuator becomes difficult at very small scales. One technique used to avoid the necessity of having to include a separate bias element is the use of local annealing to fabricate a monolithic device out of nickel titanium (NiTi). The actuator geometry is machined out of a single piece of non-annealed NiTi. After locally annealing a portion of the complete device, that section exhibits the shape memory effect while the remainder acts as structural support and provides the bias force required for cycling. This work proposes one such locally-annealed monolithic SMA actuator for future incorporation in a device that navigates the digestive tract. After detailing the derivation of lumped electro-mechanical models for the actuator, a description of the prototyping procedure, including fabrication and local annealing of the actuator, is provided. This thesis presents the experimental prototype actuator behaviour and compares it with simulations generated using the developed models.

Shape memory alloys (SMAs) provide exciting opportunities for miniature actuation systems. As SMA actuators are scaled down in size, cooling increases and bandwidth, improves. However, the inclusion of a bias element with which to cycle the SMA actuator becomes difficult at very small scales. One technique used to avoid the necessity of having to include a separate bias element is the use of local annealing to fabricate a monolithic device out of nickel titanium (NiTi). The actuator geometry is machined out of a single piece of non-annealed NiTi. After locally annealing a portion of the complete device, that section exhibits the shape memory effect while the remainder acts as structural support and provides the bias force required for cycling. This work proposes one such locally-annealed monolithic SMA actuator for future incorporation in a device that navigates the digestive tract. After detailing the derivation of lumped electro-mechanical models for the actuator, a description of the prototyping procedure, including fabrication and local annealing of the actuator, is provided. This thesis presents the experimental prototype actuator behaviour and compares it with simulations generated using the developed models.

This dissertation addresses new developments in the constitutive modeling and structural analysis pertaining to rate-independent and rate-dependent irrecoverable inelasticity in Shape Memory Alloys (SMAs). A new model for fully recoverable SMA response is derived that accounts for material behaviors not previously addressed. Rate-independent and rate-dependent irrecoverable deformations (plasticity and viscoplasticity) are then considered. The three phenomenological models are based on continuum thermodynamics where the free energy potentials, evolution equations, and hardening functions are properly chosen. The simultaneous transformation-plastic model considers rate-independent irrecoverable strain generation and uses isotropic and kinematic plastic hardening to capture the interactions between irrecoverable plastic strain and recoverable transformation strain. The combination of theory and implementation is unique in its ability to capture the simultaneous evolution of recoverable transformation strains and irrecoverable plastic strains. The simultaneous transformation-viscoplastic model considers rate-dependent irrecoverable strain generation where the theoretical framework is modfii ed such that the evolution of the viscoplastic strain components are given explicitly. The numerical integration of the constitutive equations is formulated such that objectivity is maintained for SMA structures undergoing moderate strains and large displacements. Experimentally validated analysis results are provided for the fully recoverable model, the simultaneous transformation-plastic yield model, and the transformation-viscoplastic creep model.

Η παρούσα διδακτορική διατριβή πραγματεύεται την κατασκευή και τον έλεγχο ενός καινοτόμου τεχνητού χεριού, για προσθετικές κυρίως εφαρμογές, κάνοντας χρήση βιομιμητικών ενεργοποιητών και πιο συγκεκριμένα ειδικά κατεργασμένων λεπτών κυλινδρικών αγωγών από μορφομνήμονα μεταλλικά κράματα νικελίου-τιτανίου. Εκμεταλλευόμενοι τα συγκριτικά πλεονεκτήματα των ενεργοποιητών αυτών έναντι των αντίστοιχων συμβατικών, αναπτύσσεται μια πλήρως λειτουργική συσκευή με μικρό μέγεθος και βάρος, ανθρωπομορφική εμφάνιση, αθόρυβη λειτουργία και χαμηλό κόστος κατασκευής και συντήρησης, ικανή να εκπληρώσει σε μεγάλο βαθμό τις απαιτήσεις των ατόμων με αναπηρία στα άνω άκρα. Για τη φυσική υλοποίηση του σκελετού του τεχνητού αυτού χεριού χρησιμοποιείται η τεχνολογία της ταχείας προτυποποίησης. Καθένα από τα πέντε δάκτυλά του ελέγχεται ανεξάρτητα μέσω ενός υπο-ενεργοποιούμενου μηχανισμού κίνησης με τεχνητούς τένοντες. Για τον έλεγχο θέσης κάθε δακτύλου, αναπτύσσεται και εφαρμόζεται μία νέα μέθοδος ελέγχου βασισμένη στην έμφυτη δυνατότητα ανάδρασης θέσης των προαναφερθέντων ενεργοποιητών μέσω μέτρησης της ηλεκτρικής τους αντίστασης. Επιπλέον, αναπτύσσεται κατάλληλος αλγόριθμος για τον σχηματισμό διαφόρων θέσεων και συλλήψεων του τεχνητού χεριού. Για τη βελτίωση του ελέγχου, το χέρι εξοπλίζεται με αισθητήρες αφής στα ακροδάκτυλα, καθώς και με τη δυνατότητα οδήγησης συσκευών οπτικής και απτικής ανάδρασης. Όλα τα ηλεκτρονικά κυκλώματα που είναι απαραίτητα για την οδήγηση των ενεργοποιητών και τον έλεγχο του χεριού αναπτύσσονται και ενσωματώνονται στο εσωτερικό του φυσικού πρωτοτύπου. Με τη βοήθεια ειδικού προγραμματιστικού πακέτου, σχεδιάζεται μία γραφική διεπαφή ελέγχου μέσω της οποίας μελετάται και αξιολογείται η δυνατότητα του αναπτυχθέντος χεριού σε πειράματα σύλληψης διαφόρων αντικειμένων. Τέλος, προτείνονται διάφορες τεχνικές ελέγχου του χεριού από τους χρήστες του, ενώ αναπτύσσεται και κατάλληλος αλγόριθμος ελέγχου βασισμένος στη χρήση ηλεκτρομυογραφικών σημάτων. / This doctoral thesis presents the development and control of an innovative artificial hand, mostly for use in prosthetic applications, utilizing biomimetic actuators, and, more specifically, specially processed thin cylindrical wires made of shape memory nickel-titanium alloys. By exploiting the comparative advantages of these actuators over the conventional ones, a fully functional device is developed, of low size and weight, anthropomorphic appearance, silent operation, low fabrication and maintenance cost, which is capable of satisfying to a great extent the needs of the upper limb amputees. The physical implementation of the chassis of this artificial hand has been performed using rapid prototyping technology. Each of its five digits is independently controlled via a tendon-driven underactuated mechanism. For the position control of each digit, a novel control scheme is devised and implemented based on the inherent position feedback capability of these actuators via the measurement of their electrical resistance. In addition, the necessary algorithm is developed for the formation of various hand postures and prehension patterns. In order to improve the overall hand control, the hand is equipped with tactile sensors at its fingertips, and is also capable of driving optical and tactile feedback devices. All the necessary electronics for driving the actuators and controlling the hand are developed and embedded inside the physical prototype. Using a special programming package, a graphical user interface is designed, through which the grasp capabilities of the developed hand are studied and evaluated for various objects. Finally, several user control techniques of the hand are proposed, and a control algorithm based on the use of electromyographic signals is also developed.

Surface-assisted directed assembly allows ultrasoft and replusive functional polymeric “colloids” to assemble into the organized supramolecular ultrathin films on a monomolecular level. This study aims at achieving a fundamental understanding of molecular morphology and responsive behavior of major classes of branched star-shaped polymers (star amphiphilic block copolymers and star polyelectrolytes) and their aggregation into precisely engineered functional ultrathin nanofilms. Thus, we focus on elucidating the role of molecular architecture, chemical composition, and intra/intermolecular interactions on the assembly behavior of highly-branched entities under variable environmental and confined interfacial conditions. The inherent molecular complexity of branched architectures facilitates rich molecular conformations and phase states from the combination of responsive dynamics of flexible polymer chains (amphiphilic, ionizable arms, multiple segments, and free chain ends) and extened molecular design parameters (number of arms, arm length, and segment composition/sequence). These marcromolecular building components can be affected by external conditions (pH, salinity, solvent polarity, concentration, surface pressure, and substrate nature) and transformed into a variety of complex nanostructures, such as two-dimensional circular micelles, core/shell unimicelles, nanogel particles, pancake & brush micelles, Janus-like nanoparticles, and highly nanoporous fractal networks. The fine balance between repulsive mulitarm interactions and surface energetic effects in the various confined surfaces and interfaces enables the ability to fabricate and tailor well-organized ultrathin nanofilms. The most critical findings in this study include: (1) densely packed circular unimicelle monolayers from amphiphilic and amphoteric multiblock stars controlled by arm number, end blocks, and pH/pressure induced aggregation, (2) monolayer polymer-metal nanocomposites by in-situ nanoparticle growth at confined interfaces, (3) on-demand control of exponentially or linearly grown heterogeneous stratified multilayers from self-diffusive pH-sensitive star polyelectrolyte nanogels, (4) core/shell umimicelle based microcapsules with a fractal nanoporous multidomain shell morphology, and (5) preferential binding and ordering of Janus-like unimicelles on chemically heterogeneous graphene oxide surfaces for biphasic hybrid assembly. The advanced branched molecular design coupled with stimuli responsive conformational and compositional behavior presents an opportunity to control the lateral diffusion and phase segregation of branched compact supermolecules on the surface resulting in the generation of well-controllable monolayers with tunable ordering and complex morphology, as well as to tailor their stratified layered nanostructures with switchable morphological heterogeneity and multicompartmental architectures. These surface-driven star polymer supramolecular assemblies and interfaces will enable the design of multifunctional nanofilms as hierarchical responsive polymer materials.