O tratamento endodôntico é constituído por uma sequência de fases que devem ser respeitadas e conduzidas com o mesmo grau de importância para o sucesso da terapia endodôntica. Atenção especial é dada a fase do o preparo biomecânico do canal radicular, que pode ocasionar extrusão de restos pulpares, tecido necrosado, rapas de dentina e substâncias químicas auxiliares através do forame apical, provocando uma reação inflamatória ou flare-up. Com o intuito de se obter um pós-operatório com êxito, realizou-se um estudo com o objetivo de avaliar, ex vivo, a quantidade de material extruído através do forame apical durante o preparo do canal radicular pelas seguintes técnicas: manual Step-Back, mecanizada rotatórias Crown Down e Free Tip Preparation. Trinta incisivos inferiores foram distribuídos aleatoriamente em 3 grupos (n=10), de acordo com as seguintes técnicas de instrumentação: G1- técnica manual Step Back (controle); G2- Crown Down; G3- Free Tip Preparation. Todos os grupos foram instrumentados a 0,5mm aquém do forame apical. O material extruído foi coletado em um Dispositivo Coletor de Material Extruído(DCME), confeccionado especificamente para essa finalidade e a extrusão apical foi calculada pela determinação da massa de material sólido extruído. Os valores obtidos foram analisados pelo teste de Kruskal- Wallis e o teste complementar de Dunn`s Multiple, com P=0.05, como nível de significância estatística. Os resultados mostraram que a técnica Step-Back promoveu maior quantidade de material extruído através do forame apical; e que não houve diferença estatística significante entre as técnicas Crown Down e Free Tip Preparation. Pode-se concluir também que houve extrusão de material sólido através do forame apical em todas as técnicas de instrumentação estudadas. / Endodontic treatment is constituted of a sequence of stages that must be respected and performed with the same degree of importance in order to ensure the success of endodontic therapy. Special attention is paid to the stage of biomechanical preparation of the root canal, which may cause the extrusion of pulp remainders, necrotic tissue, dentin scrapings and auxiliary chemical substances through the apical foramen, causing an inflammatory reaction or flare-up. With the intention of achieving successful post-operative period, a study was conducted with the aim of making an ex vivo evaluation of the quantity of material extruded through the apical foramen during root canal preparation, by means of the following techniques: manual Step-Back, mechanized rotary Crown Down and Free Tip Preparation. Afterwards, the teeth were randomly assigned to three equal groups (n=15) according to post length, as follows: G1 manual Step-Back technique (control); G2 - Crown Down; G3 - Free Tip Preparation. All the groups were instrumented to 0.5 mm short of the apical foramen. The extruded was collected in an Extruded Material Collecting Device (EMCD), made specifically for this purpose, and apical extrusion was calculated by determining the mass of solid material extruded. The values obtained were analyzed by the Kruskal-Wallis test and complementary Dunns Multiple test, with P=0.05, as the level of statistical significance. The results showed that the Step-Back technique promoted the largest amount of material extruded through the apical foramen; and that there was no statistically significant difference between the Crown Down and Free Tip Preparations. It could also be concluded that there was extrusion of solid material through the apical foramen in all the studied instrumentation techniques used.

The purpose of the present study was to assess the feasibility of a laser layer manufacturing technique for realization of shape memory alloy (SMA) components with complex geometry. Pre-placed laser solid freeform fabrication (LSFF) was utilized to produce straight and curvaceous SMA parts from a mixture of 55.2 wt%Ni - 44.8 wt%Ti powder. A pulsed Nd:YAG laser was used; while laser pulse width and frequency were held constant at what are considered their optimal values (4 ms and 50 Hz, respectively), laser energy and scanning speeds were varied across samples to determine appropriate values for fabrication of high quality SMA parts . Different pre-placed powder thicknesses were deposited and then mechanically and physically studied. Optical microscopy, SEM, EDS, and XRD methods, as well as microhardness measurements, were used to examine the microstructural characteristics and hardness of the SMA samples. Also, differential scanning calorimetry (DSC) was performed to determine the transformation temperatures of the fabricated parts. The results confirmed the formation of crack-free solid surfaces in which two types of microstructure exist: solid (non-prose) and dendrite arms. EDS chemical composition analysis confirmed the absence of any impurity or oxidise in the cross section of the samples as well as the presence of only nickel and titanium. XRD spectrum analysis indicated the presence of Ni-Ti intermetallic phases, which are almost Ni-Ti but contain a small amount of Ti2Ni. The XRD results also indicated the presence of austenite and martensite phases, which are exchanged during heating or mechanical deformation. The hardness of these samples varied from 250 to 450 HV0.3. Several tests were carried out to investigate the shape memory effect (SME). It was observed that the fabricated SMAs can recover from the bent condition very quickly (i.e., 1 to 8 seconds) depending on their thickness. In general, the fabricated parts were first bent out of their original shapes then heated, in various ways, above the transformation temperature. To theoretically assess the SME performance of the fabricated SMAs with the proposed geometry two models were developed. The first model was established based upon a lump approach in which the part was exposed to an electrical current. The second model, however, was established based upon a finite element method in which a specific domain at one end of the sample was exposed to a source of heat. It was found that the theoretical outputs from both models were in good agreement with the experimental results.

The purpose of the present study was to assess the feasibility of a laser layer manufacturing technique for realization of shape memory alloy (SMA) components with complex geometry. Pre-placed laser solid freeform fabrication (LSFF) was utilized to produce straight and curvaceous SMA parts from a mixture of 55.2 wt%Ni - 44.8 wt%Ti powder. A pulsed Nd:YAG laser was used; while laser pulse width and frequency were held constant at what are considered their optimal values (4 ms and 50 Hz, respectively), laser energy and scanning speeds were varied across samples to determine appropriate values for fabrication of high quality SMA parts . Different pre-placed powder thicknesses were deposited and then mechanically and physically studied. Optical microscopy, SEM, EDS, and XRD methods, as well as microhardness measurements, were used to examine the microstructural characteristics and hardness of the SMA samples. Also, differential scanning calorimetry (DSC) was performed to determine the transformation temperatures of the fabricated parts. The results confirmed the formation of crack-free solid surfaces in which two types of microstructure exist: solid (non-prose) and dendrite arms. EDS chemical composition analysis confirmed the absence of any impurity or oxidise in the cross section of the samples as well as the presence of only nickel and titanium. XRD spectrum analysis indicated the presence of Ni-Ti intermetallic phases, which are almost Ni-Ti but contain a small amount of Ti2Ni. The XRD results also indicated the presence of austenite and martensite phases, which are exchanged during heating or mechanical deformation. The hardness of these samples varied from 250 to 450 HV0.3. Several tests were carried out to investigate the shape memory effect (SME). It was observed that the fabricated SMAs can recover from the bent condition very quickly (i.e., 1 to 8 seconds) depending on their thickness. In general, the fabricated parts were first bent out of their original shapes then heated, in various ways, above the transformation temperature. To theoretically assess the SME performance of the fabricated SMAs with the proposed geometry two models were developed. The first model was established based upon a lump approach in which the part was exposed to an electrical current. The second model, however, was established based upon a finite element method in which a specific domain at one end of the sample was exposed to a source of heat. It was found that the theoretical outputs from both models were in good agreement with the experimental results.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-06-08T20:13:29Z No. of bitstreams: 1 ARTUR SOARES CAVALCANTI LEAL – TESE (PPGEP) 2015.pdf: 3350275 bytes, checksum: 82c914b993b5ca424066ec905959c6f6 (MD5) / Made available in DSpace on 2018-06-08T20:13:29Z (GMT). No. of bitstreams: 1 ARTUR SOARES CAVALCANTI LEAL – TESE (PPGEP) 2015.pdf: 3350275 bytes, checksum: 82c914b993b5ca424066ec905959c6f6 (MD5) Previous issue date: 2015-07-29 / CNPq / O uso de sistemas epoxídicos no campo da moderna tecnologia industrial, aliado aos materiais nanocompósitos tem sido extensivamente estudado nos últimos anos. As ligas com efeito de memória de forma (LMF) inseridos em matriz poliméricas a base de resina epóxi e argila organofílica podem formar estruturas exageradamente denominadas “compósitos inteligentes”. Esse desenvolvimento tecnológico vem ocorrendo devido à necessidade de utilização de materiais com propriedades especiais, não encontradas em um único material, mas que podem ser obtidos pela combinação de diversos outros, originando propriedades singulares. O estudo do comportamento térmico de fios de Ni-Ti incorporados em nanocompósitos aquecidos por efeito Joule utilizando a técnica de termografia de infravermelho, assim como a modelagem e simulação, visando desenvolver e otimizar compósitos ativos para controle de vibração mecânica é de grande interesse e originalidade. Neste contexto, o presente estudo tem como objetivos avaliar o efeito térmico teórico-experimental em fios de Ni-Ti embebidos em nanocompósitos poliméricos a base de resina epóxi e argilas organofílicas comercial, aquecidos por efeito Joule. O foco principal está na caracterização térmica dos compósitos híbridos através da simulação numérica com auxílio do software ANSYS CFX. Para tanto, nanocompósitos poliméricos foram obtidos para receber fios de Ni-Ti. O modelo matemático utilizado reproduziu o fenômeno de transferência de calor no interior da resina, obtendo resultados coerentes e aproximados aos resultados obtidos experimentalmente. A adição de argila na composição química da amostra apresentou influência proporcional ao aquecimento por efeito Joule. A localização dos fios na matriz, o teor de argila e o coeficiente de transferência de calor assim como a fração volumétrica de fios afetam a distribuição da temperatura no interior do compósito. / Use of the epoxy systems in the area and performance of modern industry technology, combined with the nanocomposite materials has been extensively studied in recent years. The Shape Memory Alloy (SMA) wire embedded in polymer matrix with epoxy resin and organoclay may form an exaggeratedly named structure “smart composites”. This technological development occurred due necessary use of materials with special properties not found in a single material, but can be obtained by combining others material, craving unique properties. The study the thermal behavior of wires of the wire Ni-Ti incorporated in to nanocomposites heated by Joule effect using infrared thermography technique, modeling and simulation, in order to develop and optimize composites for mechanical active vibration control is of great interest and originality. In this context the present study evaluate the theoretical and experimental thermal effect in Ni-Ti wires embedded in polymer nanocomposites epoxy/organoclay commercial organoclays, heated by Joule effect. For both, polymer nanocomposites were obtained for receiving the Ni-Ti wire, the temperature distribution of wires embedded in polymer nanocomposites, using infrared thermography technique and simulation using ANSYS CFX commercial software were evaluated. The mathematical model used reproduced the phenomenon of heat transfer in the resin, aproximate efficiency consistent results and the results obtained experimentally. The addition of clay in the chemical composition of the sample had proportional influence to heating by Joule effect. The locations of the wires in the matrix, the clay and the heat transfer coefficient as well as the volume fraction affect the temperature distribution with in the composite.

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-09-27T19:14:47Z No. of bitstreams: 2 Dissertação - Leonardo S. Oliveira.pdf: 12252504 bytes, checksum: 0e50a939b3de4c6ee29549c3e7da914c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2017-09-27T19:15:01Z (GMT) No. of bitstreams: 2 Dissertação - Leonardo S. Oliveira.pdf: 12252504 bytes, checksum: 0e50a939b3de4c6ee29549c3e7da914c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-09-27T19:15:01Z (GMT). No. of bitstreams: 2 Dissertação - Leonardo S. Oliveira.pdf: 12252504 bytes, checksum: 0e50a939b3de4c6ee29549c3e7da914c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-08-07 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A blend of elemental powders of Ni, Ti, Ge in the nominal composition Ni33Ti33Ge34 was subjected to mechanical alloying for 84h20min. The evolution of its structural and thermal characteristics was investigated by X-ray diffraction (XRD), Rietveld method (RM) and differential scanning calorimetry (DSC). Indeed, the inclusion of defects caused by milling induced a number of structural changes. I just five minutes of synthesis, it was ascertained the nucleation of intermetallics with crystallites sizes in nanometric dimensions. The formation of multiple phases is assigned to the low formation energy of the formed compound, among them the ternary alloy NiTiGe of the space group Pnma. From 2h20min, the crystalline structures undergo a remarkable degree of amorphization, reaching its maximum in 34h20min. Subsequently, in 59h20min, the metastability of the amorphous component gives rise to the re-nucleation of NiGe and Ni2.74Ge2 phases, which minimizing its free energy. In addition to this, the mechanical crystallization led to the formation of the TiO2-II high pressure phase and the B19’-NiTi shape memory alloy. In sequence, the amorphous content grows again and, with the growth of the tetragonal TiO2 phase, in 84h20min, the system recrystallizes and the milling was stopped. Therefore, it is observed that the system under study experiences a succession of metastable equilibrium due to the milling. / Uma mistura de pós elementares de Ni, Ge e Ti na composição nominal Ni33Ti33Ge34 foi submetida a mechanical alloying (MA) por 84h20min. A evolução das suas características estruturais e térmicas foram investigadas por difração de raios-X (DRX), método de Rietveld (MR) e calorimetria diferencial de varredura (DSC). De fato, a inclusão de defeitos provocados pela moagem induziu uma série de modificações estruturais. Em apenas cinco minutos de síntese, foi observada a nucleação de intermetálicos com cristalitos de dimensões nanométricas. A formação de múltiplas fases é atribuída a baixas energia de formação dos compostos formados, dentre elas a liga ternária NiTiGe do grupo espacial Pnma. A partir de 2h20min, as estruturas cristalinas presentes sofrem um notável grau de amorfização, atingindo seu máximo em 34h20min. Posteriormente, em 59h20min, a metaestabilidade da componente amorfa dá origem a re-nucleação das fases NiGe e Ni2.74Ge2, minimizando sua energia livre. Além dessas, a cristalização mecânica conduziu a cristalização da fase de alta pressão TiO2-II e da liga de memória de forma B19’-NiTi. Na sequência, a fração amorfa volta a crescer e, com a cristalização da fase TiO2 tetragonal em 84h20min, sistema recristaliza e a moagem foi interrompida. Dessa forma, nota-se que o sistema em estudo sofre uma sucessão de equilíbrios metaestáveis em função da moagem.

No description available.

Shape memory alloys (SMAs) possess the unique ability to change their shape by undergoing a solid-state phase transformation at a particular temperature. The shape change is associated with a large strain recovery as the material returns to its "remembered" shape. Their ability to act as both sensor and actuator has made them an attractive subject of study for numerous applications. SMAs have many characteristics which are advantageous in space-related applications, including generation of large forces associated with the strain recovery, smooth and controlled movements, large movement to weight ratio, high reliability, and spark-free operation. The objective of this work is the further development and testing of a cryogenic thermal conduction switch as part of NASA funded projects. The switch was developed to provide a variable conductive pathway between liquid methane and liquid oxygen dewars in order to passively regulate the methane temperature. Development of the switch concept has been continued in this work by utilizing Ni-Ti-Fe as the active SMA element. Ni-Ti-Fe exhibits the shape memory effect at cryogenic temperatures, which makes it well suited for low temperature applications. This alloy is also distinguished by an intermediate phase change known as the rhombohedral or R-phase, which is characterized by a small hysteresis (typically 1-2 deg C) and offers the advantage of precise control over a set temperature range. For the Ni-Ti-Fe alloy used, its thermomechanical processing, subsequent characterization using dilatometry and differential scanning calorimetry and implementation in the conduction switch configuration are addressed. This work was funded by grants from NASA KSC (NAG10-323) and NASA GRC (NAG3-2751).

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-16T19:08:32Z No. of bitstreams: 1 JOSIANE DANTAS COSTA - DISSERTAÇÃO PPGEQ 2015..pdf: 2694660 bytes, checksum: b1f464f2e8b29d82a5339c5bd52471b3 (MD5) / Made available in DSpace on 2018-03-16T19:08:32Z (GMT). No. of bitstreams: 1 JOSIANE DANTAS COSTA - DISSERTAÇÃO PPGEQ 2015..pdf: 2694660 bytes, checksum: b1f464f2e8b29d82a5339c5bd52471b3 (MD5) Previous issue date: 2015-09-29 / A liga de Ni-Ti, conhecida por Nitinol, é constituída dos elementos níquel e titânio e vem sendo bastante aplicada nas mais diversas áreas: aeroespacial, automotiva, construção civil, dispositivos médicos e ortodônticos. Esse potencial de aplicação decorre das propriedades particulares de efeito de memória de forma e superelasticidade, associada a uma boa resistência à corrosão e excelente biocompatibilidade. Com intuito de aumentar as aplicações desse material em dispositivos médicos, o desenvolvimento de tecnologias de união torna-se necessário para possibilitar a fabricação das mais diferentes formas geométricas e combinações entre materiais similares e dissimilares. Nesse contexto, é fundamental que se realize estudos sobre a resistência a corrosão da região em que foi feita a união (junta), principalmente quando utilizados processos de soldagem, já que podem deixar falhas induzindo a uma maior suscetibilidade a corrosão. Diante disto, neste trabalho foi realizada a união de fios ortodônticos de Ni-Ti com fios ortodônticos de Ti-Mo através do processo de soldagem TIG (“Tungsten Inert Gas”) autógeno. Como se trata de biomateriais, este estudo teve como objetivo geral avaliar a resistência à corrosão dos fios comerciais íntegros e da junta soldada Ni-Ti/Ti-Mo em solução salina tamponada SBF (“Saline Buffered Phosphate”) que simula o sangue humano, para verificar se a soldagem afetaria a resistência a corrosão das juntas. Os resultados obtidos revelaram que o processo da soldagem TIG utilizado neste trabalho gerou juntas soldadas de excelente qualidade, apresentando uma resistência à corrosão superior à dos fios íntegros. O planejamento experimental utilizado para verificar a influência da temperatura e do tempo do tratamento térmico nos resultados de corrosão, gerou um experimento ótimo com temperatura de 350°C e um tempo de 40 minutos. Este resultado foi confirmado através dos ensaios de espectroscopia de impedância eletroquímica. / The Ni-Ti alloy, known as Nitinol, is made of nickel and titanium elements and has been widely applied in several areas: aerospace, automotive, construction, medical and orthodontic appliances. Nitinol's application potential is due to its particular superelasticity properties and shape memory effect associated with a good corrosion resistance and excellent biocompatibility. In order to increase the applications of this material in medical devices, the development of joining technologies is necessary to enable manufacture of the most different geometric shapes and combinations of similar and dissimilar materials. In this context, it is essential to conduct studies on the corrosion resistance of the region where the union (joint) was done, especially when welding processes are used, as they can leave gaps leading to greater susceptibility to corrosion. With this in mind, this work carried out the union of Ni-Ti orthodontic wire with Ti-Mo orthodontic wire through the autogenous TIG (Tungsten Inert Gas) welding process. As biomaterials are involved, this study aimed to evaluate the corrosion resistance of the upright commercial wire and welded joint Ni-Ti/Ti-Mo in buffered saline solution SBP (Saline Buffered Phosphate) which simulates human blood, to check if the welding would affect the corrosion resistance of the joint. The results revealed that the TIG welding process used in this work generated welds of excellent quality, having a corrosion resistance higher than that of intact wires. The experimental design used to determine the influence of temperature and time of heat treatment on the results of corrosion generated a great experiment with temperature of 350 ° C and a time of 40 minutes. This result was confirmed by means of electrochemical impedance spectroscopy test.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-03-14T21:54:07Z No. of bitstreams: 1 NATHÁLIA CRISTINA MORAIS LIA FOOK - DISSERTAÇÃO PPGEQ 2015..pdf: 2182368 bytes, checksum: 5948d7190b44ee52e0cbfdbf788ee8dd (MD5) / Made available in DSpace on 2018-03-14T21:54:07Z (GMT). No. of bitstreams: 1 NATHÁLIA CRISTINA MORAIS LIA FOOK - DISSERTAÇÃO PPGEQ 2015..pdf: 2182368 bytes, checksum: 5948d7190b44ee52e0cbfdbf788ee8dd (MD5) Previous issue date: 2015-10-05 / Capes / As ligas de Ni-Ti têm possibilitado uma melhoria em muitos projetos tradicionais de engenharia e das áreas médicas e ortodônticas, com suas propriedades únicas de superelasticidade e efeito de memória de forma. Nas últimas décadas, as pesquisas e análises para aplicações destas ligas se tornaram cada vez mais específicas, para estudos sobre micro e nano atuadores visando aplicações em dispositivos médicos e ortodônticos e em microssistemas eletromecânicos. Assim, os processos de soldagem se tornaram importantes aliados, promovendo a união entre atuadores de liga de memória de forma (LMF) com semelhantes e dissemelhantes, uma forma de aumentar as aplicações úteis de materiais disponíveis, principalmente como biomateriais. Nesse contexto, este estudo teve como objetivo geral a avaliação da resistência à corrosão em uma região de solda obtida por microssoldagem TIG autógena em fios de Ni-Ti superelásticos com fios de Ni-Ti termoativados em solução que simula a saliva humana. Os fios soldados também passaram por um tratamento térmico feito com base em um planejamento fatorial 3². A caracterização dos fios íntegros e soldados (com e sem tratamento térmico) foi realizada utilizando ensaios de calorimetria diferencial de varredura (DSC), microscopia eletrônica de varredura (MEV) e também quanto à resistência à corrosão. Os resultados obtidos revelaram que o processo de soldagem TIG utilizado neste trabalho gerou juntas soldadas de excelente qualidade, apresentando uma boa resistência à corrosão no eletrólito que simula a saliva humana. O planejamento experimental utilizado para verificar a influência da temperatura e do tempo do tratamento térmico nos resultados de corrosão gerou um experimento ótimo com temperatura de 350°C e um tempo no intervalo de 20 a 40 minutos. Estes resultados foram confirmados através dos ensaios de espectroscopia de impedância eletroquímica. / The Ni-Ti alloys have enabled the improvement in many projects from the traditional engineering and from the medical and orthodontic areas with their unique properties of superelasticity and shape memory effect. In recent decades, researches and analysis for applying these alloys have become increasingly more specific, tending to studies on micro and nano actuators targeting applications in medical and orthodontic devices and in electromechanical microsystems. Thus, the welding processes have become important allies by promoting the union between shape memory alloy actuators (SMA) with similar and dissimilar ones, which is one way of increasing the useful applications of available materials, especially biomaterials. In this context, this study aimed at analyzing the corrosion resistance in the weld region obtained by autogenous TIG micro welding in Ni-Ti superelastic wires with thermo-active Ni-Ti wires in a solution that simulates human saliva. The welded wires also Soldiers wires also undergone heat treatment made based on a factorial design 3. The characterization of the original and welded wires (with and without heat treatment) was performed using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) tests and also regarding its resistance to corrosion. The results revealed that the TIG welding process used in this work generated welds of excellent quality, showing a good resistance to corrosion in the electrolyte that simulates human saliva. The experimental design used to investigate the influence of temperature and time of heat treatment in corrosion results generated a great experiment with temperature of 350 °C and time in the range of 20 to 40 minutes. These results were confirmed by means of electrochemical impedance spectroscopy tests.

Submitted by Rafael Santana (rafael.silvasantana@ufpe.br) on 2018-03-12T19:13:22Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) COMPORTAMENTO EM FADIGA TERMOMECÂNICA DE FIOS DE LIGA COM MEMÓRIA DE FORMA Ni-Ti-Cu.pdf: 4577247 bytes, checksum: 80f553611587916c4a69ac3a78c41e28 (MD5) / Made available in DSpace on 2018-03-12T19:13:22Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) COMPORTAMENTO EM FADIGA TERMOMECÂNICA DE FIOS DE LIGA COM MEMÓRIA DE FORMA Ni-Ti-Cu.pdf: 4577247 bytes, checksum: 80f553611587916c4a69ac3a78c41e28 (MD5) Previous issue date: 2017-02-22 / Na maioria das aplicações tecnológicas os atuadores de liga de memória de forma (LMF) estão submetidos aos mais diversos tipos de carregamentos mecânicos, o que torna imprescindível o estudo da vida em fadiga destes tipos de materiais. Diante disto, o presente trabalho tem como objetivo analisar o comportamento dinâmico e a fadiga termomecânica de fios de LMF Ni-Ti-Cu, submetidos a ensaios dinâmicos em modo de flexão simples (Single Cantilever) utilizando um equipamento de Análise Mecânico Dinâmico (DMA – Dynamic Mechanical Analysis). Assim, foram realizadas análises para determinar a capacidade de amortecimento dos fios, além da fadiga estrutural nos estados martensítico e austenítico. A vida em fadiga dos fios foi avaliada por meio do número de ciclos até a ruptura em função das amplitudes de deformação aplicadas durante o processo de ciclagem mecânica. Os resultados demonstraram uma considerável capacidade de amortecimento dos fios, principalmente durante a transformação de fase e uma influência direta da amplitude de deformação imposta, nos valores de força e no tempo de vida dos fios, revelando que a fadiga situa-se numa faixa entre 103 a 105 ciclos, caracterizando uma fadiga de baixo ciclo. / In most technological applications, Shape Memory Alloy (SMA) actuators are subjected to the most diverse types of mechanical loads, which makes it essential to study the fatigue life of these types of materials. Therefore, the present work has the objective of analyzing the dynamic behavior and thermomechanical fatigue of SMA Ni-Ti-Cu wires, submitted to dynamic tests in single cantilever mode using a Dynamic Mechanical Analysis (DMA). Thus, analyzes were carried out to determine the damping capacity of the wires, besides the structural fatigue in the martensitic and austenitic states. The fatigue life of the wires was evaluated by means of the number of cycles until the rupture as a function of the strain amplitudes applied during the mechanical cycling process. The results demonstrated a considerable damping capacity of the wires, especially during phase transformation and a direct influence of the imposed strain amplitude, on the values of force and the life time of the wires, revealing that the fatigue is in the range of 103 To 105 cycles, characterizing a low cycle fatigue.