Robôs de reabilitação como próteses ativas e exoesqueletos necessitam de atuadores capazes de atender certos requisitos como baixa impedância de saída, backdrivability, geração de torques grandes e precisos, e uma estrutura leve e compacta. Este trabalho apresenta o projeto de um Atuador Elástico em Série rotacional (AESr) para ser usado em uma prótese ativa para auxiliar na flexão/extensão da articulação do joelho durante a fisioterapia. O dispositivo é constituído de um motor de corrente contínua, um redutor de velocidade do tipo coroa e rosca sem-fim e uma mola torcional personalizada. Uma vez que o elemento elástico é o componente mais importante no projeto do AESr, um procedimento de análise baseado no Método dos Elementos Finitos (MEF) é utilizado para cumprir os requisitos definidos para a reabilitação do joelho. Com uma massa total de 2,53 Kg, é possível montar diretamente o atuador proposto em uma estrutura de prótese de joelho. Controladores de torque e impedância são implementados para assegurar uma interação segura com o paciente, permitindo que novas estratégias de reabilitação sejam avaliadas. As especificações do projeto bem como o desempenho dos controladores são validados experimentalmente. / Wearable robots, like prostheses, active orthosis and exoskeletons need of actuators able to meet certain requirements as low output impedance, backdrivability, precise and large torque generation, and a compact and lightweight design. This work presents the design of a rotary Series Elastic Actuator (rSEA) to be used in an active orthosis to assist in flexion/extension of the knee joint during physical therapy. The device includes a DC motor, a worm gear and a customized torsion spring. Since the elastic element is the most important component in the design of the rSEA, an analysis procedure based on Finite Element Method (FEM) is used in order to meet the requirements for the specific application. With a total weight of 2.53 kg, it is possible to directly mount the actuator on the frame of a knee orthosis. Torque and impedance controllers are implemented to ensure secure interaction with the patient and enable new strategies for rehabilitation. The design specifications as well as the controllers performance are verified by experiments.

The aim of this study was to evaluate the mechanical properties of engine-driven Nickel-Titanium instruments manufactured by different thermal treatments. In the first part of this study, 60 reciprocating instruments were used (n=20): Reciproc R25 (REC 25.08), Unicone L25 (UNC 25.06) e Prodesign R 25 (PDR 25.06). The cyclic flexural fatigue resistance was performed measuring the time to failure in an artificial stainless steel canal with a 60º angle and a 5 mm radius of curvature (n=10). The torsional test was performed according to ISO 3630-1, measuring the torque and angle of rotation at failure in the 3 mm from the tip portion (n=10). Additionally, the fractured surface of each instrument was examined by scanning electron microscopy (SEM) to assess the topographic features of the fractured surface. Data were analyzed using one was analysis of variance ANOVA and Tukey test, the level of significance was set at 5%. The results of the cyclic flexural fatigue showed that PDR 25.06 presented significantly higher values than the other groups (P<0.05). REC 25.08 showed higher fatigue resistance than UNC 25.06 (P<0.05). In relation to the torsional test, the PDR 25.06 presented the lowest torque load than REC 25.08 and UNC 25.06 (P<0.05). In addition, there was no significant difference between REC 25.08 and UNC 25.06 (P>0.05). The PDR 25.06 and UNC 25.06 showed higher angular rotation until fracture than REC 25.08 (P<0.05). No difference was found between PDR 25.06 and UNC 25.06. All the instruments showed typical topographic features of cyclic flexural and torsional fatigue. The second part of this study evaluated the cyclic flexural and torsional fatigue resistance of reciprocating instruments Reciproc Blue (RB 25.08), WaveOne Gold Primary (WOG 25.07) and Prodesign R 25 (PDR 25.06) (n=20). The cyclic flexural fatigue test was performed with the same previsoly described device, using a root curvature with 60º and a 5 mm radius (n=10) and the torsional test was performed according to ISO 3630-1 (n=10). The fractured surface of each instrument was examined by scanning electron microscopy (SEM). Data were analyzed using one was analysis of variance ANOVA and Tukey test, the level of significance was set at 5%. The results of the cyclic flexural fatigue test showed that PDR 25.06 presented significantly higher values than the other groups (P<0.05). RB 25.08 showed higher fatigue resistance than WOG 25.07 (P<0.05). The torsional test showed that PDR 25.06 had lowed torsional load (P<0.05). No difference was found between RB 25.08 and WOG 25.07 (P>0.05). In relation the angular rotation, the PDR 25.06 showed higher angular rotation values than RB 25.08 and WOG 25.07 (P<0.05). RB 25.08 presented higher angular values than WOG 25.07 (P<0.05). All the instruments showed typical topographic features of cyclic flexural and torsional fatigue. The third part of this study was to evaluate the torsional fatigue resistance of NiTi rotary glide path instruments. The torsional test was performed according to ISO 3630-1, measuring the torque and angle of rotation at failure in the 3 mm from the tip portion. A total of 56 glide path instruments were used (n=8): Logic 25.01 (LOG 25.01), Logic CM 25.01(LOG CM 25.01), Proglider 16.02 (PGD 16.02), Hyflex GPF 15.01, 15.02, 20.02 (HGPF) and Mtwo 10.04. The fractured surface of each instrument was examined by scanning electron microscopy (SEM). Data were analyzed using one was analysis of variance ANOVA and Tukey test, the level of significance was set at 5%. The results showed that LOG 25.01 had a significantly higher torsional load than the other groups (P<0.05). The PGD 16.02 had significantly difference in comparison with HGPF 15.01 and 15.02 (P<0.05). LOG CM 25.01 had higher torsional load than HGPF 15.01 and 15.02 (P<0.05). No difference was found among Mtwo 10.04, HGPG 15.01, 15.02 and 20.02. In relation the angular rotation, LOG CM 25.01 and HGPF 15.01 presented the highest values (P<0.05). PGD 16.02 had the lowest values (P<0.05) followed by Mtwo 10.04. LOG 25.01 had higher angle of rotation than PGD 16.02 and Mtwo 10.04 (P<0.05). All the instruments showed typical topographic features of torsional fatigue. / O objetivo deste estudo foi avaliar o comportamento mecânico de instrumentos mecanizados de Níquel-Titânio (NiTi) fabricados com diferentes tratamentos térmicos. Na primeira parte do estudo foram utilizados 60 instrumentos reciprocantes para a realização dos teste de fadiga cíclica flexural e torcional (n=20): Reciproc R25 (REC 25.08), Unicone L25 (UNC 25.06) e Prodesign R 25 (PDR 25.06). O teste de fadiga cíclica flexural foi realizado com o objetivo de mensurar o tempo para a fratura dos instrumentos em um canal artificial de aço inoxidável com curvatura com 60º de angulação e 5 mm de raio (n=10). Para o teste de torção, os 3 mm inicias das pontas dos instrumentos foram fixadas em um aparelho de torção (n=10), de acordo com a norma ISO 3630-1. Este teste foi realizado com o objetivo de mensurar o torque máximo e o ângulo de rotação suportado pelos instrumentos até sua fratura. Adicionalmente, todos os fragmentos dos instrumentos fraturados foram examinados em microscopia eletrônica de varredura (MEV) para avaliar as características topográficas da superfície da área da fratura. A análise-estatística foi realizada utilizando o teste de análise de variância com um fator ANOVA e teste de Tukey, o nível de significância foi de 5%. Os resultados de fadiga cíclica flexural demonstraram que o PDR 25.06 apresentou maior tempo para a fratura do que os outros grupos (P<0.05). O instrumento REC 25.08 apresentou maior resistência a fadiga cíclica flexural do que o UNC 25.06 (P<0.05). O teste de torção demonstrou que o PDR 25.06 apresentou significantemente menor resistência torcional do que o REC 25.08 e UNC 25.06 (P<0.05). Além disso, não houve diferença entre REC 25.08 e UNC 25.06. Com relação ao ângulo de rotação, o PDR 25.06 e UNC 25.06 apresentaram diferença significante quando comparado ao REC 25.08. Não houve diferença entre PDR 25.06 e UNC 25.06 (P>0.05). Todos os instrumentos apresentaram característica topográficas típicas de fadiga cíclica flexural e torcional. Na segunda parte deste estudo avaliou-se a fadiga cíclica flexural e torcional dos instrumentos reciprocantes Reciproc Blue R25 (RB 25.08), WaveOne Gold Primary (WOG 25.07) e Prodesign R 25 (PDR 25.06) (n=20). O teste de fadiga cíclica flexural foi realizado com dispositivo descrito anteriormente, utilizando curvaturas de 60º e 5 mm de raio (n=10). O teste de torção foi realizado de acordo com a norma ISO 3630-1 (n=10). Todos os fragmentos dos instrumentos fraturados foram examinados em microscopia eletrônica de varredura (MEV) para avaliar as características topográficas da superfície da área da fratura. A análise-estatística foi realizada utilizando o teste de análise de variância com um fator (ANOVA) e teste de Tukey, o nível de significância foi de 5%. Os resultados de fadiga cíclica flexural demonstraram que o PDR 25.06 apresentou a maior resistência a fadiga cíclica flexural do que dos outros grupos (P<0.05). O RB 25.08 apresentou maior tempo para à fratura do que o WOG 25.07 (P<0.05). O teste de torção, o PDR 25.06 apresentou a menor resistência à torção do que os outros grupos (P<0.05). Não houve diferença significante entre RB 25.08 e WOG 25.07 (P>0.05). Em relação ao ângulo de rotação, o PDR 25.06 apresentou maiores valores quando comparados com RB 25.08 e WOG 25.07. O RB 25.08 apresentou diferença significante quando comparado com WOG 25.07. Todos os instrumentos apresentaram características topográficas típicas de fadiga cíclica flexural e torcional. Na terceira parte deste estudo avaliou-se a resistência torcional de instrumentos empregados para patência do canal radicular, de acordo com a norma ISO 3630-1. Foram utilizados 56 instrumentos rotatórios (n=8): Logic 25.01 (LOG 25.01), Logic CM 25.01 (LOG CM 25.01), Proglider 16.02 (PGD 16.02), Hyflex GPF 15.01, 15.02, 20.02 (HGPF) e Mtwo 10.04. Os fragmentos dos instrumentos fraturados foram examinados em microscopia eletrônica de varredura (MEV) para avaliar as características topográficas da superfície da área da fratura. A análise-estatística foi realizada utilizando o teste de análise de variância com um fator ANOVA e teste de Tukey, o nível de significância foi de 5%. Os resultados demonstraram que o LOG 25.01 apresentou significantemente maior resistência torcional do que os demais grupos (P<0.05). O grupo da PGD 16.02 apresentou diferença significante quando comparado com HGPF 15.01 e 15.02 (P<0.05). O LOG CM 25.01 apresentou maior resistência torcional do que o grupo do HGPF 15.01 e 15.02 (P<0.05). Não houve diferença significante entre os intrumentos Mtwo 10.04 e HGPF 15.01, 15.02 e 20.02. Com relação ao ângulo de rotação, o LOG CM 25.01 e HGPF 15.01 apresentaram os maiores valores (P<0.05). O PGD 16.02 apresentou o menor valor de todos os grupos (P<0.05) seguido pelo Mtwo 10.04. O LOG 25.01 apresentou maiores ângulos de rotação do que o PGD 16.02 e Mtwo 10.04 (P<0.05). Todos os instrumentos apresentaram característica topográficas típicas de fadiga torcional. As características da secção transversal, tipo de núcleo, taper e o tratamento térmico possuem forte influência sobre as propriedades mecânicas dos instrumentos de NiTi. No entanto, o tratamento térmico é um dos fatores primordiais para maior flexibilidade dos instrumentos. O instrumento PDR 25.06 apresentou maior resistência à fadiga cíclica flexural e maior ângulo de rotação no teste de torção do que todos os outros instrumentos reciprocantes avaliados. No entanto, menor resistência torcional. Os intrumentos LOG 25.01 apresentaram maior resistência torcional e o LOG CM 25.01 maiores ângulos de rotação.

The validity of transfer matrix method (TMM) employed in a nonlinear gear cam system is studied in this thesis. The nonlinear dynamic responses of each part in the nonlinear system are estimated by applying the 4th-order Runge-Kutta method. A high speed gear cam drive automatic die cutter was analyzed in this study. A 25 horsepower AC induction motor is designed to drive the system. To complete the cutting work, a sequential process of the harmonic motion and the intermittent motion are generated by the elbow mechanism and the gear cam mechanism, respectively. A simplified branched multi-rotor system is modeled to approximate the motion of the system. The variation of the dynamic parameters of the system in a loading cycle is estimated under a branched torsional system. The Holzer¡¦s transfer matrix method is used to study the variation of the system parameters during the intermittent movement. Moreover, the effect of time-varied speed introduced from the torque variation of the induction motor and gear cam mechanism on the nonlinear dynamic response of the system has also been investigated. To explore the dynamic effect of different cam designs, three different cam motion curves and seven operating rates have been analyzed in this work. The residual vibration of the last sprocket has also been discussed. Numerical results indicate that the proposed model is available to simulate the dynamic responses of a nonlinear gear cam drive system.

The results from an experimental study on the dynamic properties of sand with nonplastic silt are presented. Combined resonant column and torsional shear equipment is used to evaluate the effects of confining pressure, shearing strain, frequency, and number of cycles of loading on the dynamic properties of silty sand. The goal of this study is to determine if relationships in the literature for sands and gravels are accurate for predicting the shear modulus and material damping characteristics of soil with nonplastic fines or if the incorporation of a fines content parameter improves predictions. This goal was primarily accomplished by reconstituting and testing samples of an alluvial deposit from Dillon Dam, Dillon, Colorado according to predetermined gradation curves with variable amounts of non-plastic fines. Among the findings of this investigation are: (1) soil parameters such as Cu and D50 can be related to dynamic properties of soils with up to 25% fines, (2) the effects of non-plastic fines on the small-strain dynamic properties of soils are not very pronounced for soils with less than 25% fines, and (3) an increase in the amount of non-plastic fines in uniform soils or soils with more than 25% fines generally results in lower values of small-strain shear modulus, higher values of small-strain material damping, and more linear G/Gmax - log([gamma]) and D - log([gamma]) curves. The effect of non-contacting, larger granular particles in a finer soil matrix is also investigated along with the impact of removing larger particles from laboratory samples. / text

The current design procedure for steel frame structures is a two-step process including an elastic analysis to determine design actions and a separate member capacity check. This design procedure is unable to trace the full range of load-deflection response and hence the failure modes of the frame structures can not be accurately predicted. In recent years, the development of advanced analysis methods has aimed at solving this problem by combining the analysis and design tasks into one step. Application of the new advanced analysis methods permits a comprehensive assessment of the actual failure modes and ultimate strengths of structural steel systems in practical design situations. One of the advanced analysis methods, the refined plastic hinge method, has shown great potential to become a practical design tool. However, at present, it is only suitable for a special class of steel frame structures that is not subject to lateral torsional buckling effects. The refined plastic hinge analysis can directly account for three types of frame failures, gradual formation of plastic hinges, column buckling and local buckling. However, this precludes most of the steel frame structures whose behaviour is governed by lateral torsional buckling. Therefore, the aim of this research is to develop a practical advanced analysis method suitable for general steel frame structures including the effects of lateral-torsional buckling. Lateral torsional buckling is a complex three dimensional instability phenomenon. Unlike the in-plane buckling of beam-columns, a closed form analytical solution is not available for lateral torsional buckling. The member capacity equations used in design specifications are derived mainly from testing of simply supported beams. Further, there has been very limited research into the behaviour and design of steel frame structures subject to lateral torsional buckling failures. Therefore in order to incorporate lateral torsional buckling effects into an advanced analysis method, a detailed study must be carried out including inelastic beam buckling failures. This thesis contains a detailed description of research on extending the scope of advanced analysis by developing methods that include the effects of lateral torsional buckling in a nonlinear analysis formulation. It has two components. Firstly, distributed plasticity models were developed using the state-of-the-art finite element analysis programs for a range of simply supported beams and rigid frame structures to investigate and fully understand their lateral torsional buckling behavioural characteristics. Nonlinear analyses were conducted to study the load-deflection response of these structures under lateral torsional buckling influences. It was found that the behaviour of simply supported beams and members in rigid frame structures is significantly different. In real frame structures, the connection details are a decisive factor in terms of ultimate frame capacities. Accounting for the connection rigidities in a simplified advanced analysis method is very difficult, but is most critical. Generally, the finite element analysis results of simply supported beams agree very well with the predictions of the current Australian steel structures design code AS4100, but the capacities of rigid frame structures can be significantly higher compared with Australian code predictions. The second part of the thesis concerns the development of a two dimensional refined plastic hinge analysis which is capable of considering lateral torsional buckling effects. The formulation of the new method is based on the observations from the distributed plasticity analyses of both simply supported beams and rigid frame structures. The lateral torsional buckling effects are taken into account implicitly using a flexural stiffness reduction factor in the stiffness matrix formulation based on the member capacities specified by AS4100. Due to the lack of suitable alternatives, concepts of moment modification and effective length factors are still used for determining the member capacities. The effects of connection rigidities and restraints from adjacent members are handled by using appropriate effective length factors in the analysis. Compared with the benchmark solutions for simply supported beams, the new refined plastic hinge analysis is very accurate. For rigid frame structures, the new method is generally more conservative than the finite element models. The accuracy of the new method relies on the user's judgement of beam segment restraints. Overall, the design capacities in the new method are superior to those in the current design procedure, especially for frame structures with less slender members. The new refined plastic hinge analysis is now able to capture four types of failure modes, plastic hinge formation, column buckling, local buckling and lateral torsional buckling. With the inclusion of lateral torsional buckling mode as proposed in this thesis, advanced analysis is one step closer to being used for general design practice.

Rotating blades are considered to be the one of the most common cause of failures in rotating machinery. Blade failure modes normally occur as a result of cracks due to unexpected operating conditions, which are normally caused by accidents of foreign objects damage, high cycle fatigue, blade rubbing, blade root looseness, and degradation from erosion and corrosion. Thus, detection of blade faults has an important role in reducing blade related failures and allowing repairs to be scheduled for the machinery. This in turn will lead to reduction in maintenance costs and thus raise productivity and safety aspects of operation. To maintain vital components of rotating machines, such as blades, shafts, bearings and gear boxes, at optimal levels, detection of failures in such components is important, because this will prevent any serious damage that could affect performance. This research study involves laboratory tests on a small rig with a bladed disc rotor that applied vibration measurements and analysis for blade fault detection. Three measurements: shaft torsional vibration, on-bearing vibration (OBV) and on-casing vibration (OCV), are used. A small test rig of a single stage bladed disc holding 8-blades was designed and manufactured, to carry out this research study to assess the usefulness and capability of each vibration technique in detection of incipient defects within machine blades. A series of tests was conducted on a test rig for three different cases of blade health conditions: (a) healthy blade(s) with mistuned effects, (b) blade root looseness and (c) cracks in a blade on two different blade sizes (long and short blades) in order to discover changes in blades' dynamic behaviour during the machine running-up operation. The data were collected using the three measurements during machine run-up and then recorded. The measured vibration data were analysed by computing the blades' resonance at different engine orders (EOs) related to the blade(s) resonance frequencies and their higher harmonics, to understand the blade(s) dynamics behaviour for the cases of healthy and faulty blade(s). Data have been further processed using a polar plot presentation method which provides clear results that can be used for monitoring blade integrity. To validate the obtained experimental results, a simplified mathematical model was also developed. Finally, a comparative study between three methods was undertaken to understand the relative advantages and limitations in the blade heath monitoring.

Les progrès de la microélectronique, axés en premier lieu sur l’amélioration des performances et la réduction des coûts des processeurs et des mémoires, ont aussi bénéficié depuis de nombreuses années aux capteurs, à l’éclairage, aux actionneurs et autres technologies dites More than Moore. La détection infrarouge à l’aide de détecteurs thermiques fait partie de ces bénéficiaires. Les détecteurs thermiques actuels utilisent principalement une fine couche résistive (typiquement du dioxyde de vanadium ou du silicium amorphe) déposée sur une membrane suspendue comme thermomètre : ce sont les microbolomètres. Cette technique a permis de produire des caméras thermiques dont le coût de fabrication a drastiquement chuté avec des performances qui se rapprochent des détecteurs photoniques onéreux, fonctionnant à des températures cryogéniques. Néanmoins, le coût de ces imageurs reste encore excessif pour des applications grand public (conduite nocturne, smartphones, domotique) tandis que les applications militaires (surveillance, lunettes portatives) demandent des performances accrues dans un budget maîtrisé. Un des objectifs des industriels du domaine est donc de réduire la surface des détecteurs, le pas pixel, afin d’augmenter le nombre de rétines fabriquées sur une plaque de silicium. Néanmoins, la réduction de cette surface diminue de facto le flux infrarouge incident sur le pixel, et donc le signal. Il faut donc améliorer la sensibilité des détecteurs à chaque nouveau pas pixel. La technologie résistive, largement employée par l’industrie jusqu’à maintenant, se prêtait volontiers à cet exercice jusqu’au pas de 17 µm, permettant de densifier d’un facteur 4 le nombre de détecteurs tous les 5 ans. L’auto-échauffement lié à la lecture résistive et le bruit en 1/f sont les principales causes du ralentissement observé dans cette réduction des échelles ces dernières années. Nos travaux se sont focalisés sur un nouveau principe de détection au pas de 12 µm, fonctionnant avec un auto-échauffement minime. Dans cette approche, une planche suspendue est mise en résonance mécanique autour de deux bras ancrés subissant une torsion. L’actionnement et la détection électrostatique du mouvement de la membrane sont réalisés avec deux électrodes situés 2 µm sous la planche. La modification du module d’Young avec la température et les contraintes thermiques vont modifier la fréquence de résonance. Les résonateurs mécaniques étant peu bruités, le suivi cette fréquence de résonance doit permettre de réaliser des détecteurs thermiques performants. Le travail de thèse a consisté à concevoir, fabriquer et caractériser de tels pixels et à comparer cette technique aux détecteurs résistifs. Différents modèles (linéaire et nonlinéaire) du mouvement de la structure sont présentés et comparés aux caractérisations expérimentales de résonateurs fabriqués en réseaux denses, selon différentes variantes. Nous avons mesuré le bruit fréquentiel de nos détecteurs puis leur sensibilité à un flux infrarouge. Les meilleurs dispositifs montrent une limite de sensibilité de 30 pW/√Hz. Une résolution sur la scène (NETD) de 2 K est obtenu pour un temps d’intégration adapté au temps image. Ces performances sont inégalées pour un résonateur non refroidi à ces dimensions. Nous montrons qu’un NETD de 20 mK est atteignable au pas de 12 µm (pour un temps de réponse de 10 ms) en se focalisant sur 3 axes de recherche : une cointégration des résonateurs avec leur électronique de lecture, une acquisition plus précise du signal par un temps d’intégration adapté au temps image et l’amélioration de la sensibilité thermique (TCF) du résonateur d’un facteur 10. Pour ce dernier point, nous présentons des méthodes afin d’améliorer le TCF. Finalement, nous étudions des architectures de pixels au pas de 5 µm présentant des performances théoriques proches de celles requises par l’imagerie infrarouge (NETD=70 mK et τth=8 ms). Des perspectives de transductions tout optiques sont finalement évoquées. / Progress in microelectronics has been mainly driven by informatics needs for addressing both increased performances and lower costs for processors and memories, according to the well-known Moore’s Law. For many years, these tremendous progresses in silicon fabrication and integration have also contributed to the emergence of new type of devices, such as sensors, actuators, filters, clocks or imagers, forming a new class of devices called More than Moore. Uncooled infrared imaging, which uses thermal sensors belongs to this new class of devices. Today thermal sensors principally use a thin resistive layer (mainly vanadium dioxide or amorphous silicon) on a suspended membrane as a thermometer and are called microbolometers. The fabrication cost of thermal cameras has dramatically dropped over the last 20 years, while attaining performances close to the expensive cooled cameras. Nevertheless, the cost of these imagers still remains too high for consumer market (night driving, smartphones, home automation) whereas military applications (surveillance, personal googles) need improved resolutions – in an affordable camera. Therefore, one objective of the microbolometers industry roadmap is to scale down the sensor surface – the pixel pitch – in order to increase the number of imagers fabricated on a silicon wafer. Yet, the pixel pitch reduction goes necessarily with a reduction of the captured infrared power leading to a reduction of the sensor signal. As a consequence, the sensor sensitivity needs to be improved as the pixel pitch scales down. The resistive technology has managed this scaling so far, down to 17µm pixel pitch, allowing a densification of the sensors by a factor 4 every 5 years. Despite this success, the scaling has been recently slowed down, mostly because of microbolometers self-heating issue and 1/f noise which are inherent to the resistive transduction. Our work has focused on a new type of sensor at 12µm pixel pitch, which theoretically gets rid of self-heating and 1/f noise. In our approach, an absorbing plate is excited at its mechanical resonance through two tiny torsion arms using an actuation electrode placed 2µm underneath. Pixel motion is also transduced electrostatically. Since micromechanical resonators feature very low frequency noise, we believe that an uncooled infrared sensor based on the monitoring of its resonance frequency (which changes with temperature through the TCF) should be extremely sensitive. In our work, we present different models (linear and nonlinear) for the pixel mechanical behavior and compare them to experimental characterization of resonators which were fabricated in dense arrays, according to several designs. We measure the frequency stability of our sensors along with their sensitivity to infrared flux. The best devices show a resolution of 30pW/sqrt(Hz), with a response time lower than one millisecond. The scene resolution (NETD) is 2K for an integration time compatible with imaging frame rate. These performances overtake results previously published on this topic with such reduced pixel pitch. We show that a NETD of 20mK (with a response time of 10ms) is reachable at 12µm pixel pitch if we can address the following 3 challenges: a cointegration of the resonators with their electronics, a shared readout of several pixels in the imaging frame rate and an improved TCF by a factor 10. Therefore, we provide different methods in order to improve the TCF. Finally, we present different pixel designs at 5µm pixel pitch which show theoretical performances close to uncooled infrared imaging requirements (NETD=70mK and tau_th=8ms). An optical transduction may also be a new route toward even better signal to noise ratio at low pitch.

[pt] Uma prospecção bem sucedida de petróleo e gás requer muitos esforços para se sobrepor os desafios encontrados, tais como vibrações axiais, laterais e torcionais. Estes fenômenos podem causar a falha prematura de componentes do sistema de perfuração, disfunção nos equipamentos de medição e aumento no tempo e custo no processo de perfuração. Em particular, vibrações torcionais estão presentes em grande parte dos processos de perfuração e podem alcançar um estado crítico: stick-slip. Um melhor entendimento sobre este fenômeno proporciona ferramentas para evitar o aumento do tempo e do custo da prospecção, assegurando o investimento e sucesso do processo de perfuração. Neste trabalho, é descrito um procedimento experimental com um atrito não linear objetivando induzir stick-slip e é feito uma modelagem analítica simples do problema. O modelo de atrito é baseado em um atrito seco imposto por um dispositivo de freio desenvolvido. O comportamento não linear da bancada experimental é analisada e o modelo numérico é validado comparando diagramas de bifurcações numérica e experimentais. / [en] A successful oil and gas prospecting requires many efforts to overcome the encountered challenges, some of these challenges include drill string axial, lateral and torsional vibrations. These phenomena may cause premature component failures of the drilling system, dysfunction of measurement equipments, and increase time and costs of the prospecting process. Torsional vibrations are present in most drilling processes and may reach a severe state: stick-slip. An improved understanding about the stick-slip phenomenon provides tools to avoid the increase of prospecting time and costs, assuring the investment and success of the drilling process. Firstly, a numerical analysis of the drill string is performed with different friction models. These models are proposed in order to get familiar with the drill string dynamics. Also, it is described the experimental procedure with a nonlinear friction aiming to induce stick-slip and is performed a simple analytical modeling of the problem. The friction model is based on dry friction imposed by a break device. The nonlinear behavior of the experimental apparatus is analyzed and the numerical model is validated comparing experimental and numerical bifurcation diagrams.

[pt] Em virtude de sua eficiência, elementos estruturais de paredes finas com seções abertas são comuns em estruturas de aço, sendo secção em I, L, C e T usuais na prática de engenharia. A maior parte das vigas de parede fina tem uma boa resistência à flexão em relação ao eixo principal de inércia, mas uma baixa rigidez à flexão em relação ao eixo de menor inércia e uma baixa rigidez em torção. É por isso que estes elementos apresentam em geral uma instabilidade que leva a um acoplamento de flexo-torção. Muitas destas estruturas trabalham em um regime não linear e uma formulação não linear que leve em conta grandes deslocamentos e os acoplamentos inerentes é necessária. Neste trabalho um modelo não linear para vigas de seção aberta e paredes finas, considerando grandes deslocamentos, os efeitos de encurtamento e acoplamentos em flexão e torção é adotado. Inicialmente um estudo das frequências naturais, das cargas críticas e da relação frequência-carga axial é apresentado para diversos perfis. Com base nestes resultados, faz-se um estudo detalhado do comportamento dinâmico não linear destes perfis destacando o efeito do acoplamento não linear na região de ressonância e sua influência na estabilidade dinâmica da estrutura. Para isto são usadas diversas ferramentas de dinâmica não linear, tais como diagramas de bifurcação, respostas no tempo e plano de fase e bacias de atração. Os resultados mostram que a consideração dos acoplamentos não lineares é essencial para se avaliar o nível de segurança destas estruturas. / [en] Due to its efficiency, thin-walled structural elements with open sections, such as I, L, C and Z profiles, are common in steel structures, being usual in engineering applications. Most thin-walled beams have a good flexural strength around of the principal axis of inertia, but a low one around the axis of lower inertia as well as low torsional stiffness. That is why these elements, generally, show instabilities that lead to flexural torsional coupling. Many of these structures do not work in a linear range and a non-linear formulation that takes into account large displacements and associated couplings is required. This dissertation presents a nonlinear model for extensional beams with thin-walled open section, considering large displacements, and flexural-torsional couplings. Initially a study of the natural frequencies, critical load and axial load vs. frequency relation is presented for different profile kinds. Based on these results, a detailed study of the dynamic behavior of non-linear profiles is made, highlighting the effect of non-linear coupling in the resonance region and its influence on the dynamic stability of the structure. For this, various tools of nonlinear dynamics are used, such as bifurcation diagrams, time histories and phase-space portraits and basins of attraction. The results show that the consideration of non-linear couplings is essential to availed the safety level of these structures.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Restrições de espaço e altura são frequentemente impostas às edificações residenciais, comerciais, industriais, depósitos e galpões com um ou diversos pavimentos em função de aspectos de regulamentos regionais, técnicos, econômicos ou ainda de natureza estética. A fim de proporcionar a passagem de tubulações e dutos de grande diâmetro sob vigas de aço, grandes alturas são normalmente requeridas, demandando por vezes, magnitudes de altura inviáveis entre pavimentos de edificações. Diversas soluções estruturais podem ser utilizadas para equacionar tais obstáculos, onde dentre outras, pode-se citar as vigas com inércia variável, stub-girders, treliças mistas, vigas misuladas e vigas com uma ou múltiplas aberturas na alma com geometrias variadas. No que tange às vigas casteladas, solução estrutural pautada neste estudo, a estabilidade é sempre um motivo de preocupação tipicamente durante a construção quando os contraventamentos laterais ainda não estão instalados. De qualquer forma, o comprimento destravado em geral alcançado pelos vãos destas vigas, são longos o suficiente para que a instabilidade ocorra. Todavia, o acréscimo substancial da resistência à flexão de tais membros devido ao aumento da altura oriundo de seu processo fabril em relação ao perfil matriz, aliada a economia de material e utilidade fim de serviço, garante a atratividade no aproveitamento destas, para grandes vãos junto aos projetistas. Não obstante, este aumento proporcional no comprimento dos vãos faz com que a instabilidade lateral ganhe importância especial. Neste contexto, o presente trabalho tem por objetivo desenvolver um modelo numérico que permita a realização de uma avaliação paramétrica a partir da calibração do modelo com resultados experimentais, efetuar a análise do comportamento de vigas casteladas e verificar seus mecanismos de falha, considerando comportamento elasto-plástico, além das não-linearidades geométricas. Também é objetivo deste trabalho, avaliar, quantificar e determinar a influência das diferenças geométricas características das vigas casteladas em relação às vigas maciças com as mesmas dimensões, analisando e descrevendo o comportamento estrutural destas vigas de aço para diversos comprimentos de vãos. A metodologia empregada para tal estudo baseou-se em uma análise paramétrica com o auxílio do método numérico dos elementos finitos. / Restrictions of space and height are often imposed to residential, commercial, industrial, warehouses and sheds with one, or several floors, due to aspects like regional regulations, technical, economic or aesthetic nature. In order to provide the passage of pipes and ducts with large diameter under steel girders, that normally requires great heights, sometimes leads to floors building highs with an unviable magnitudes. Several structural solutions can be used to overcome these obstacles, where the most popular are the beams with variable inertia (tapered and haunched beams), stub-girders, trusses, and beams with one or more web openings with various geometries. When castellated beams, structural solution studied and discussed in this dissertation, are considered stability issues at the construction stage becomes to attract the structural engineer attention since the lateral bracing are not yet installed. The unbraced span lengths generally reached by these beams are often long enough to cause instability effects. However, the substantial enhancement in the flexural strength of such members, due to the extra height coming from the manufacturing process in relation with the original profile, combined with the economy of material and utility services, ensures to the designers the attractiveness of this solution, especially when applied to large spans. On the other hand, this proportional increase in span lengths enhances the significance of improving the beam lateral instability resistance. The present investigation aims to develop a numerical model, that calibrated with experimental results, enables the development of a parametric analysis. This analysis aimed to determine the structural behavior of the castellated beams and their associated failure mechanisms, considering an elastic-plastic behavior as well the geometric non-linearities. The investigation was also able to evaluate, quantify and determine the influence of geometry variables like span lengths and cross sections dimensions. The methodology used for this study was developed based on a parametric analysis centred on the finite element method.