L’objectif de ce travail est d’élaborer et de caractériser pour des applications biomédicalesun matériau auto-enchevêtré à base d’une seule fibre d’alliage à mémoire deforme de type Nickel-Titane. Nous avons optimisé un procédé de fabrication consistantà enchevêtrer et figer un ressort par des traitements thermiques. Les échantillonsont été caractérisés en compression et traction, avec suivi par caméra optique ettomographie in-situ. Les structures obtenues sont homogènes, isotropes, superélastiquesà température ambiante jusqu’à des déformations d’au moins 30%, et peuventdevenir ferroélastiques avec un effet mémoire d’au moins 16% par un traitement thermiqueadditionnel. Leur comportement en compression est consolidant puis dilatantet en traction, légèrement auxétique. Une comparaison avec des milieux similairesconstitués de fils ductiles et viscoélastiques, ainsi qu’avec des simulations par élémentsdiscrets sur des milieux élastiques sans frottement, montre que les propriétésmécaniques des structures auto-enchevêtrées sont contrôlées par leur architecturesingulière, à mi-chemin entre milieux continus et discrets. / The aim of this work is to process and characterize for biomedical applications,self-entangled structures made of a single NiTi shape memory fiber. We have optimizeda processing route consisting in entangling and shape-setting a spring bythermomechanical treatments. The samples were characterized in compression andtension, using optical and x-ray tomographic observations. The structures thus obtainedare homogeneous, isotropic, superelastic at room temperature up to strains ofat least 30%, and can become ferroelastic with a shape memory effect up to at least16% strain by an additional heat treatment. The mechanical behavior in compressionis first consolidating and then dilating, while in tension, the samples are slightlyauxetic. A comparison with similar media made of ductile and viscoelastic fibers,as well as with discrete element simulations on friction-free elastic fibers, show thatthe mechanical properties of these self-entangled structures are controlled by theirunique architecture, in-between continuous and discrete media.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-08-17T17:30:45Z No. of bitstreams: 1 JOSÉ RICARDO FERREIRA OLIVEIRA – DISSERTAÇÃO (PPGEM) 2017.pdf: 2648257 bytes, checksum: 5e08d81aaa5973d7c6fd8bac23c313cc (MD5) / Made available in DSpace on 2018-08-17T17:30:45Z (GMT). No. of bitstreams: 1 JOSÉ RICARDO FERREIRA OLIVEIRA – DISSERTAÇÃO (PPGEM) 2017.pdf: 2648257 bytes, checksum: 5e08d81aaa5973d7c6fd8bac23c313cc (MD5) Previous issue date: 2017-11-30 / CNPq / A caracterização termofísica dos materiais utilizados na Engenharia é de grande importância para realização de projetos nas mais diversas áreas de conhecimento onde os fenômenos ligados aos processos de transferência de calor exercem um papel fundamental. A difusividade térmica é uma propriedade termofísica importantíssima na análise de problemas de difusão de energia térmica. Este trabalho teve como proposta a determinação desta propriedade utilizando um campo de temperatura periódico. Para isto, foi construído um dispositivo experimental com princípio de funcionamento no método de Angstrom, o qual faz uso de um fluxo de calor periódico de uma fonte controlada, gerando assim, um campo de temperatura periódico na amostra em teste. Termopares foram instalados nas amostras para captar os sinais de temperatura gerados pelo fluxo de calor periódico. A amplitude e a fase destes sinais foram obtidas por meio de um software de análise gráfica. O termopar mais próximo da fonte de calor foi adotado como referência, ao passo que a razão de amplitudes e a defasagem, entre os sinais térmicos registrados pelos demais termopares em relação ao registrado por àquele termopar , foram calculadas. Estes resultados foram utilizados em modelos matemáticos para determinar a difusividade térmica, que pode ser identificada ou atra vés da razão de amplitudes ou através da defasagem entre os perfis de temperatura. As amostras utilizadas neste trabalho foram de aço inox AISI 304, aço inox AISI 316 e de uma liga de memória de forma de níquel-titânio. Os valores de difusividade térmica identificados para estes materiais, quando foram comparados com valores disponíveis na literatura, obtiveram uma boa concordância, tendo em vista a faixa de incerteza apresentada. / Thermophysical characterization of materials used in engineering is very important for realization of projects in the most diverse areas of knowledge where the phenomena related to the process of heat transfer play an important role. Thermal diffusivity is a very important thermal property on the analysis of problems of diffusion of thermal energy. This work proposes the determination of this property using a periodic temperature field. For this, an experimental device was built with principle of operation in Angstrom’s method, which makes use of a periodic heat flow from a controlled source, thereby generating a periodic temperature field in the test sample. Thermocouples were installed on the samples for capture of signals generated by the periodic heat flow. Amplitude and phase of these signals were obtained by means of graphic analysis software. The thermocouple closest to the heat source was adopted as reference, and the ratio and phase lag, between the thermal signals registered by other thermocouples in relation to that registered by that thermocouple, were calculated. These results were utilized in mathematical models to determine the thermal diffusivity, whose identification can be performed either through the amplitude ratio or through the phase lag between the temperature profiles. Samples utilized in this work were stainless steel AISI 304, stainless steel AISI 316 and a shape memory alloy of nickel-titanium. Identified values of thermal diffusivity of these materials, when compared whit values available in literature obtained a good agreement, considering the range of uncertainty presented.

En tant que nouveau matériau magnétique à mémoire de forme, les alliages basés sur le système Ni-Mn-Sn possèdent de multiples propriétés physiques telles que l'effet de mémoire de forme des alliages polycristallins, l'effet magnétocalorique géant, l'effet de magnétorésistance et l'effet de polarisation d'échange. Jusqu'à présent, la plupart des études ont été axées sur l'amélioration des multifonctionnalités de ces alliages, mais l'information fondamentale qui est fortement associée à ces propriétés n'est toujours pas claire. Ainsi, une étude approfondie sur les structures cristallines de la martensite et de l'austénite, les caractéristiques microstructurales et cristallographiques de la transformation martensitique a été menée dans le cadre du présent travail de doctorat. Il a été confirmé que l'austénite de Ni50Mn37.5Sn12.5 possède une structure cubique L21 (Fm3 ̅m, No.225). Le paramètre de réseau de l'austénite dans Ni50Mn37.5Sn12.5 est aA = 5.9813 Å. La martensite possède une structure orthorhombique (4O) à quatre couches (Pmma, No.51). Les paramètres de réseau de la martensite dans Ni50Mn38Sn12 et Ni50Mn37.5Sn12.5 sont a4O = 8.6068 Å; b4O = 5.6226 Å and c4O = 4.3728 Å, and a4O = 8.6063 Å, b4O = 5.6425 Å, and c4O = 4.3672Å, respectivement. La martensite 4O Ni-Mn-Sn présente une microstructure hiérarchiquement maclée. La martensite est organisée en larges plaques dans le grain d'austénite d'origine. Les plaques contiennent des colonies à forme irrégulière avec deux modèles caractéristiques de microstructures : le motif lamellaire classique et le motif en arête de poisson. Dans chaque colonie, il existe quatre variantes d'orientation (A, B, C et D) et elles forment trois types de macles (Type I, Type II et macles composées). Les interfaces entre les variantes correspondantes sont en coincidence avec leur plan de maclage K1. Les plans d'interface des paires de macles composées A-D et B-C peuvent avoir une ou deux orientations différentes, ce qui conduit aux deux modèles microstructuraux. Les variantes correspondantes dans les colonies voisines dans une même large plaque (colonies intra-plaques) possèdent des orientations proches et le joint de colonie est courbé, tandis que la limite de colonie inter-plaques est relativement droite. La relation d’orientation de Pitsch (Orientation Relation OR), spécifiée comme {1 0 1} A//{22 ̅1}4O and <1 0 1 ̅> A//<1 ̅2 2>4O, a été exclusivement déterminée à être une OR effective entre l'austénite cubique et la martensite modulée 4O. Sous cette OR, 24 variantes peuvent être générées dans un grain d'austénite. Ces 24 variantes sont organisées en 6 groupes et chaque groupe correspond à une colonie de martensite. La structure de martensite finement maclée (microstructure sandwich) est le composant microstructural de base produit par la transformation martensitique. Une telle structure assure une interface de phase invariante (plan d'habitat) pour la transformation. Au cours de la transformation, les variantes de la martensite sont organisées en clusters en forme de diamant composés de colonies de variantes et avec des structures en forme de coin au front de transformation. Chaque coin est composé de deux structures sandwich séparées par un plan de nervure médiane {1 0 1}A. Les paires de variantes dans chaque coin devraient avoir le même type de macles avec une relation de Type I ou de Type II pour garantir de bonnes compatibilités géométriques des variantes à l'interface de phase et au plan de la nervure centrale. Dans les diamants, les colonies sont séparées par des frontières présentant des marches à faible énergie interfaciale qui évoluent vers les joints des colonies intra-plaques et par des joints droits qui deviennent les joints entre les plaques. Les diamants s'allongent le long de la direction presque parallèle aux plans de la nervure centrale des coins et la forme de la plaque de la martensite est finalement formée. [...] / Being a novel magnetic shape memory material, Ni-Mn-Sn based alloy systems possess multiple physical properties, such as shape memory effect of polycrystalline alloys, giant magnetocaloric effect, large magnetoresistance effect and exchange bias effect. So far, most studies have been focused on the improvement of the multifunctionalities of these alloys, but the fundamental information which is highly associated with these properties is still unclear. Thus, a thorough study on the crystal structures of martensite and austenite, microstructural and crystallographic features of martensitic transformation has been conducted in the present PhD work. The austenite of Ni50Mn37.5Sn12.5 was confirmed to possess a L21 cubic structure (Fm"3" ̅m, No.225). The lattice parameter of austenite in Ni50Mn37.5Sn12.5 is aA=5.9813 Å. The martensite possesses a four-layered orthorhombic (4O) structure (Pmma, No.51). The lattice parameters of martensite in Ni50Mn38Sn12 and Ni50Mn37.5Sn12.5 are a4O = 8.6068 Å; b4O = 5.6226 Å and c4O = 4.3728 Å, and a4O = 8.6063 Å, b4O = 5.6425 Å, and c4O = 4.3672Å, respectively. The 4O Ni-Mn-Sn martensite exhibits a hierarchically twinned microstructure. The martensite is organized into broad plates in the original austenite grain. The plates contain irregularly shaped colonies with two characteristic microstructural patterns: classical lamellar pattern and herring-bone pattern. In each colony, there are four orientation variants (A, B, C and D) and they form three types of twins (Type I, Type II and compound twin). The interfaces between the corresponding variants are in coincidence with their twinning plane K1. The interface planes of the compound twin pairs A-D and B-C can have one or two different orientations, which leads to the two microstructural patterns. The corresponding variants in the neighboring colonies within one broad plate (intra plate colonies) possess close orientations and colony boundary is curved, whereas the inter plate colony boundary is relatively straight. The Pitsch OR, specified as "{1 0 1}" A//"{2 " "2" ̅" " "1" ̅"}" 4O and "<1 0 " "1" ̅">" A//"<" "1" ̅" " "2" ̅" 2>" 4O, was uniquely determined to be an effective OR between the cubic austenite and 4O modulated martensite. Under this OR, 24 variants can be generated within one austenite grain. Such 24 variants are organized into 6 groups and each group corresponds to a martensite colony. The finely twinned martensite structure (sandwich microstructure) is the basic microstructural constitute produced by martensitic transformation. Such a structure ensures an invariant phase interface (habit plane) for the transformation. During the transformation, martensite variants are organized into diamond shaped clusters composed of variant colonies and with wedge shaped structures at the transformation front. Each wedge is composed of two sandwich structures separating by a midrib plane {1 0 1}A. The variant pairs in each wedge should have the same twin type with either Type I or Type II relation to ensure good geometrical compatibilities of the variants at phase interface and at the midrib plane. Within the diamonds, colonies are separated by step-like boundaries with low interfacial energy that evolve into the intra plate colony boundaries and by straight boundaries that become the inter plate colony boundaries. The diamonds elongates along the direction nearly paralleled to the midrib planes of the wedges and plate shape of martensite is finally formed. Such features of the diamond structure in Ni-Mn-Sn alloys are realized by self-accommodation of transformation strains for energy minimization. The present work provides comprehensive microstructural and crystallographic information on martensite and on martensitic transforamtion of Ni-Mn-Sn alloys and it is useful for understanding their multi functionalities associated with martensitic transformation and helpful on property optimization

This thesis focuses on the role of interfacial strain in heterostructures to modify the magnetism of thin ferromagnetic films due to the inverse magnetostrictive effect, defined as the change of magnetization produced in ferromagnetic materials by an external stress. Thus, the magnetic control can be obtained without applying an external field by using heterostructures composed of a non-magnetic layer characterized by a temperature-driven structural phase transition coupled to a ferromagnetic layer. In such heterostructures, the magnetization of the ferromagnetic layer is modified through changes in the stress field at the interface when the structural phase transition in the non-magnetic layer (actuator) is carried out. In this work, we used NiTi shape memory alloy as the actuator to modify the magnetic behavior of ferromagnetic films through the magneto-elastic coupling in novel NiTi/Ni and NiTi/Co heterostructures. NiTi, when near its equiatomic composition, is a shape memory alloy that undergoes a reversible structural phase transition with temperature, providing stress on the ferromagnetic film. We chose this alloy because NiTi exhibits a large recovery stress with transition temperatures above room temperature for Ti-rich NiTi films, which is of interest for technological applications of the heterostructures. Since the right microstructure of NiTi is important to observe structural phase transition and it defines the characteristic of the transition, an extensive review on previous research on NiTi is detailed in this thesis. Thus, to ensure large stress during the NiTi structural transition with temperature, the NiTi alloy must be near its equiatomic composition with a thickness above 800 nm. Both characteristics were confirmed by Rutherford Backscattering analyses. The crystal structure and its transition with temperature were studied by X-ray diffraction measurements. In-plane magnetization and hysteresis measurements with temperature, performed on a superconducting quantum interference device (SQUID) magnetometer, prove the magneto-elastic coupling that was observed as an enhancement in the magnetic moment of the ferromagnetic layer. Such enhancement becomes the feature of magneto-elastic coupling in these novel NiTi/ferromagnetic heterostructures. / Esta tese estuda o papel da tensão interfacial em filmes heterogêneos na modificação do magnetismo de camadas ferromagnéticas finas por meio do efeito magnetoestritivo inverso, definido como a mudança de magnetização produzida em materiais ferromagnéticos por um estresse externo. Tecnologicamente, isto visa ter um grau de controle magnético do material sem a aplicação de um campo externo, usando heteroestruturas compostas por uma camada não magnética caracterizada por uma transição de fase estrutural acionada pela temperatura, acoplada a uma camada ferromagnética. Em tais heteroestruturas, a magnetização da camada ferromagnética é modificada através de alterações no campo de tensão na interface quando a transição de fase estrutural na camada não magnética (atuador) é realizada. Assim, utilizamos a liga com memória de forma NiTi como atuador, para modificar o comportamento magnético de filmes ferromagnéticos através do acoplamento magnetoelástico em novas heteroestruturas de NiTi/Ni e NiTi/Co. O NiTi, quando próximo à sua composição equiatômica, é uma liga com memória de forma que sofre uma transição de fase estrutural reversível com a temperatura, proporcionando tensão no filme ferromagnético. Escolhemos esta liga porque o NiTi apresenta uma grande tensão de recuperação com temperaturas de transição acima da temperatura ambiente, para filmes de NiTi ricos em Ti, o que é de interesse para aplicações tecnológicas das heteroestruturas. A microestrutura do NiTi é fundamental para favorecer a transição de fase estrutural e definir as suas características. Assim, uma extensa revisão de pesquisas anteriores sobre NiTi é detalhada nesta tese. Para garantir um grande estresse durante a transição estrutural do NiTi com a temperatura, o filme de NiTi deve estar próximo de sua composição equiatômica e ter espessura acima de 800 nm. Ambas as características foram confirmadas pelas análises de espectroscopia de retroespalhamento Rutherford. A estrutura cristalina e sua transição com a temperatura foram estudadas por medidas de difração de raios X. Medidas de magnetização e histerese em função da temperatura, com campo aplicado no plano dos filmes, realizadas em um magnetômetro SQUID, comprovaram a existência do acoplamento magnetoelástico, o qual se manifestou através de variações no momento magnético da camada ferromagnética. Essas mudanças de magnetização, observadas principalmente na heteroestrutura com Ni, torna-se a característica principal do acoplamento magnetoelástico nesses novos materiais.

Orientadores: Helder Anibal Hermini, Paulo R. G. Kurka / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-10T05:53:08Z (GMT). No. of bitstreams: 1 Mendes_EduardoFelippeAguiar_M.pdf: 4299696 bytes, checksum: d73355f383b74bd0e49b3bc2473e5b6b (MD5) Previous issue date: 2007 / Resumo: Este trabalho visou o estudo de manipuladores à semelhança do membro superior humano. Após o estudo do membro superior humano e dos robôs antropomórficos disponíveis tanto na industria quanto no meio acadêmico, utilizaram-se teorias de modelagem geométrica, cinemática direta e cinemática inversa para realizar o modelo de um manipulador robótico antropomórfico. A partir desse modelo desenvolveu-se um software em LabVIEW de Cinemática Direta e Cinemática Inversa de operação em tempo real. Com a intenção de verificar os acionadores mais apropriados disponíveis atualmente, um estudo de músculos artificiais se seguiu, onde se observou a maior viabilidade do músculo artificial de SMA ativado eletricamente. Um protótipo de junta acionada por músculos artificiais foi desenvolvido e controlado via computador. Como resultado deste trabalho conclui-se que há ainda muito para ser desenvolvido na área de manipuladores antropomórficos, principalmente no que diz respeito aos músculos artificiais / Abstract: This work sought the study of manipulators to the similarity of the human superior member. After the study of human superior member, and of anthropomorphics robotics available in the industries and in the academic middle, it was used theories of geometric modelling, direct kinematics modelling and inverse kinematics modelling to make the model of a anthropomorphic robotic manipulator. With that model it grew a software in LabVIEW of real time Direct Kinematics and Inverse Kinematics. With the intention of verifying the available most appropriate actuators, a study of artificial muscles was proceeded, where the largest viability of the artificial muscle of SMA activated electrically was observed. A joint prototype actuated by artificial muscles was developed and controlled through computer. As a result of this work it is ended that there is still a lot to be developed in the area of anthropomorphic manipulators, mainly in what it concerns the artificial muscles / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Disertace analyzuje vliv koncentrátorů napětí na průběh martensitické transformace, vznik plastické deformace a její vliv na přerozdělení napětí a vznik zbytkového pnutí a reziduálního martenzitu v okolí koncentrátorů v prvcích ze slitin s tvarovou pamětí NiTi. Vliv je analyzován v režimech superelastického isotermálního cyklování a aktuačního cyklování, t.j. teplotního cyklování pod vnějším napětím. Disertace využívá pro vyhodnocení vlivu experimentální přístup spolu s numerickými simulacemi metodou konečných prvků na modelových případech tenkých pásků ze slitin NiTi opatřených půlkruhovými vruby. V experimentální části je vyhodnocován vliv koncentrátorů pomocí termomechanických experimentů s využitím metod obrazové korelace a rentgenové mikrodifrakce pro lokální analýzu deformací a fázových objemových podílů v průběhu cyklování v okolí vrubů. Simulace metodou konečných prvků poskytují komplementární informace o průběhu napětí, deformací a martensitické transformaci, zejména o vývoji jednotlivých složek celkové deformace, tj. elastické a plastické, a vývoji zbytkového pnutí a s ním souvisejícím zbytkovým martensitem.Disertace je dále doplněna o numerickou analýzu vlivu konstrukce stentů na lokální cyklický průběh martensitické transformace a jeho vliv na únavové vlastnosti.

Hold down release mechanisms (HDRMs) are used for tightly attaching segments of bodies together when it is desired to release them rapidly at some point. When transporting sensitive payloads on launch vehicles, the challenge arises of releasing the fastened segments of the spacecraft without risking damage to the costly equipment. Non-explosive HDRMs are favourable from a safety perspective as there is a lower risk of producing potentially destructive shock-waves throughout the structure.  One variant of a non-explosive HDRM uses a so called 'split spool initiator'. This initiator can only be used once in the actuator mechanism and to reuse the HDRM the initiator must be replaced. The purpose of this thesis is to design an improved split spool initiator which can be reusable while conserving the functionality aspects of the existing design. To achieve this, different ideas were considered and ultimately a solution using shape memory alloys (SMAs) was explored. A prototype was constructed to demonstrate the functionality of the design and simulations are done to determine the forces acting on different parts of the mechanism. / Hold down release-mekanismer (HDRM) används för att säkert kunna fästa samman delar av strukturer för att sedan kunna lossa dessa vid rätt tillfälle. När det transporteras känslig last på exempelvis rymdfarkoster uppkommer utmaningen att göra så på ett sätt som inte riskerar att skada den ofta dyra utrustningen. Det finns en mängd olika HDRM, dessa kan delas upp i två typer som är icke explosiva release-mekanismer och pyrotekniska release-mekanismer. Icke explosiva release-mekanismer har en fördel över pyrotekniska som är att de inte producerar potentiellt destruktiva chock-vågor som sprids genom strukturen. En typ av icke-explosiva release-mekanismer är den så kallade split spool-initieraren. Denna kan endast användas en gång när fästelementet är aktiverat och för att kunna använda fästelementet igen måste hela initieraren bytas ut. Syftet med denna studie har varit att att designa en förbättrad split spool-initierare som är återanvändbar, medan funktionaliteten hos den ursprungliga designen är bevarad. För att åstadkomma detta övervägdes olika idéer och slutligen valdes en lösning som använder minnesmetaller eller Shape memory alloys på engelska (SMA). En prototyp konstruerades för att demonstrera funktionaliteten hos designen. Simuleringar gjordes även för att bestämma krafter som agerade på split spool-strukturen och för att få en överblick över spänningsfördelningen genom initieraren.

No description available.

Magnetic Shape Memory (MSM) alloys show a superelastic behaviour with possible deformation rates up to 6% until 12% and a sufficient lifetime performance [1, 2]. In this paper, a passive application for a superelastic Ni-Mn-Ga-alloy is presented by using the MSM element as an accurately defined inner friction in a system of a multistable actuator, in particular a multistable proportional valve. The multistable valve is characterized by a currentless holding of the valve displacement in any position of the stroke. This circumstance makes the concept a very low energy consumption valve, compared to conventional proportional valves with solenoid actuators. The new aspect of a rigid connection of MSM Materials enables an absorption of tension as well as compressive forces. To realize an applicable controlling valve, a simple and effective controlling strategy has been implemented. Due to the stabilizing effect of the MSM element, an accurate controlling of the valve stroke and the usage for example as a pressure-, mass-flow or temperature-controlling valve was made possible. Furthermore, some potential applications in pneumatics as well as in hydraulics are presented.

This contribution describes the properties and limitations of multi-layered mechanical devices with variable flexural stiffness. Such structures are supposed to be components of new smart, self-sensing and self-controlling composite materials for lightweight constructions. To enable a proper stiffness control, reliable actuators with high actuation capabilities based on smart materials are used. Those actuators are either driven by electroactive polymers (EAPs) or shape memory alloy (SMA) wires. They control the area moment of inertia of the multi-layered bending structures. To change the area moment of inertia and, hence, the flexural stiffness of an multi-layered beam within a wide range, it is necessary to stack as many layers as possible over each other. The fundamental function of this approach is demonstrated with a three-layer stack consisting of three independent layers and four form closure actuators driven by SMAs. This experimental set-up was able to change its bending stiffness k by a factor of 14.6, with a minimum and maximum stiffness of kmin = 0.11 N mm¯¹ and kmax = 1.73 N mm¯¹, respectively. The usage of four independently controllable actuators yields nine independent flexural-stiffness states of the beam. Both analytical and numerical calculations have shown good agreement with the measured stiffness values.