Made available in DSpace on 2014-06-11T19:22:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-11-30Bitstream added on 2014-06-13T20:49:10Z : No. of bitstreams: 1 takiy_ae_me_ilha.pdf: 1702331 bytes, checksum: b89d2b4960ee7bbc0e01a3a5d3e7a2be (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Neste trabalho estuda-se a interferometria laser, a qual constitui uma técnica adequada para determinar grandezas físicas com sensibilidade extremamente elevada. Basicamente, no interferômetro óptico, a informação a respeito do dispositivo sob teste é inserida na fase da luz. Utilizando-se o fotodiodo, promove-se a transferência de informação, do domínio óptico para o elétrico, no qual pode ser demodulada usando-se as várias técnicas disponíveis na literatura para detectar sinais modulados em fase. Ênfase é dada a um novo método de demodulação de fase óptica auto-consistente e de grande sensibilidade. Neste método, utiliza- se a modulação dada por uma forma de onda triangular e é baseado na análise do espectro do sinal fotodetectado, sendo capaz de estender a faixa dinâmica de demodulação a valores tão elevados quanto às dos métodos clássicos. Simulações dinâmicas computacionais de interferômetros ópticos são executadas em Simulink juntamente com este método, levando-se em consideração tensões de ruído eletrônico do tipo ruído branco, evidenciando a eficiência do método quando comparados com dados teóricos obtidos em Matlab. A validação experimental do método é realizada com o auxílio de um modulador eletro-óptico de amplitudes, cujas características de fase podem ser previstas analiticamente. Trata-se de um sensor polarimétrico baseado em cristal de Niobato de Lítio, em que a diferença de fase óptica induzida pela tensão elétrica aplicada pode ser determinada através de análise espectral, tal como o novo método descrito neste trabalho. Um interferômetro de Michelson homódino de baixo custo é implementado e a eficiência do novo método de demodulação de fase óptica é avaliada através de testes com atuadores e manipuladores piezoelétricos flextensionais, cujas características de linearidade são conhecidas... / In this work, has been done a study the laser interferometer, which is a technique for determining physical quantities with extremely high sensitivity. Basically, in the optical interferometer, information about the device under test modulates the phase of light. Using a photodiode, promotes the transfer of information from the optical domain for the electric, which can be demodulated using the various techniques available in literature to detect modulated signals in phase. Emphasis is given to a new method of phase demodulation of optical self-consistent and high sensitivity. The method employs a linear modulation given by a triangular waveform, and is based on analysis of the spectrum of the photodetected signal, being able to extend the dynamic range of the demodulation values as high as the classical methods. Dynamic computational simulations of optical interferometers are implemented in Simulink with this method, taking into account strains of electronic noise like white noise, indicating the efficiency of the method compared with theoretical data obtained in Matlab workspace. The experimental validation of the method is performed with the aid of an electro- optic amplitude modulator, whose phase characteristics can be analytically predicted. This is a polarimetric sensor based on lithium niobate crystal, in which the optical phase difference induced by electric voltage can be determined by spectral analysis, using new method described in this work. A low cost homodyne Michelson interferometer is implemented and the efficiency of the new method of optical phase demodulation is evaluated by testing with piezoelectric flextensional actuators whose characteristics of linearity are well known.The experimental results agree with theoretical analysis and reveal this method is more efficient than the classical methods

Submitted by Roberta Irma Martin (robertagortan@gmail.com) on 2018-04-10T11:54:24Z No. of bitstreams: 1 Tese_Roberta_Martin_FINAL.pdf: 33647313 bytes, checksum: 7d8c8a7a029acf674e2e269e15cb1251 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-04-10T17:39:20Z (GMT) No. of bitstreams: 1 martin_ri_dr_ilha.pdf: 33647313 bytes, checksum: 7d8c8a7a029acf674e2e269e15cb1251 (MD5) / Made available in DSpace on 2018-04-10T17:39:20Z (GMT). No. of bitstreams: 1 martin_ri_dr_ilha.pdf: 33647313 bytes, checksum: 7d8c8a7a029acf674e2e269e15cb1251 (MD5) Previous issue date: 2018-03-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta um estudo teórico e experimental de um sistema de controle não linear baseado em estrutura variável e modos deslizantes desenvolvido para interferômetro de dois feixes. O sistema proposto apresenta alta precisão, robustez e, além disso, é simples e de baixo custo, aumentando a capacidade de medição para diferentes aplicações de sensores interferométricos. Comparado a outras técnicas de controle aplicadas a interferometria óptica, esta técnica apresenta importantes vantagens e leva em consideração a característica não linear do interferometro, aumentando seu poder de medição. Consequentemente, um circuito de reset não é necessário, o interferometro pode trabalhar em ambientes com grandes perturbações, a montagem e ajuste dos parâmetros é mais simples (fácil implementação), com simples configuração e custo efetivo, atingindo alta robustez e acurácia. Comparado as técnicas de demodulação baseado no espectro do sinal (J1..J4), o sistema proposto tem faixa dinâmica e resolução maiores, podendo medir atraso no tempo e operar com formas de onda arbitrárias. Além disso, aperfeiçoa os métodos de demodulação temporais aumentando a precisão para sinais de baixa amplitude, mantendo a condição de quadratura (ponto máximo de sensibilidade) e, portanto, elimina o efeito do desvanecimento do sinal, mesmo diante de grandes perturbações ao redor do sistema como, vibrações, variações de temperatura e correntes de ar. A estabilidade do sistema linearizado foi estudada através do método de linearização de Lyapunov e a estabilidade local dos pontos de equilíbrio foram provadas. Através do método do plano de fase, todas as não linearidades do sistema foram consideradas, e provou-se que para qualquer condição inicial, o sistema não linear é estável e converge para o ponto de equilíbrio. Como resultado, o sistema é globalmente assintóticamente estável e não tende a um ciclo limite ou à intabilidade. Finalmente, foi obtido a equação de Lyapunov do sistema não linear considerando a análise do plano de fase, provando novamente a estabilidade do sistema de controle. Portanto, essa abordagem pode compensar o comportamento não linear do interfometro, mantendo-o na condição de quadratura e eliminando o efeito do desvanecimento do sinal para formas de onda arbitrárias, senoidais ou sem sinal de entrada, mesmo diante de grandes perturbações externas. O sistema provou ser eficiente para operações dinâmicas em diferentes aplicações como: caracterização de atuadores piezoelétricos, caracterização da resposta da fibra à temperatura, detecção de ultrassom e detecção de ondas longitudinais geradas por um laser Q-switched em amostras de alumínio e aço, conforme mostrado neste trabalho. A alta robustez oferecida pelo controlador permite que o sistema seja embarcado e opere em ambientes com grandes perturbações como fábricas, trazendo a interferometria para fora do laboratório. / This work presents the theoretical and experimental study of a nonlinear control system designed for two beam optical interferometry based on variable structure and sliding modes. The proposed system presents high accuracy, robustness and, furthermore, is simple and low cost, increasing the measurement capability for different applications of interferometric sensors. Compared with other control techniques applied in optical interferometry, this control technique presents important features and takes in account the nonlinear characteristic of the interferometer, increasing its measurement capability. Consequently, a reset circuit is not necessary, the interferometer can work in harsh environments, the assembly and adjustment of the parameters is simpler (easy implementation), with simple setup and the effective cost, achieving high robustness and accuracy. Regarding demodulation techniques based on signal spectrum (J1..J4), the proposed system has a higher dynamic range, resolution, can measure time delay and operate with arbitrary signal waveforms. Also, it improves the temporal demodulation methods increasing the accuracy for small amplitude signals, maintaining the quadrature condition (maximum point of sensitivity) and, therefore, eliminates the effect of signal fading, even under strong external disturbances around the interferometer setup such as vibration, temperature variation and air current flow. The stability of the linearized system was studied through the Lyapunov’s linearization method and the local stability of the equilibrium points were proved. Through the phase plane method, we considered all the nonlinearities from the system, and we proved that for any initial condition, the nonlinear system is stable and converges to the equilibrium point. As a result, the system is globally asymptotically stable and it does not tend to a limit cycle nor to instability. Finally, we obtained the Lyapunov equation for the nonlinear system taking into account the phase plane analysis, proving the system’s stability. Therefore, this approach can fully compensate the nonlinear behavior of the interferometer, keep it in the quadrature point and suppress the signal fading for arbitrary signal waveforms, sinusoidal signals or zero input signal, even under strong external disturbances. The system proved to be suitable for dynamic operations, in different applications as: characterization of piezoelectric actuators, characterization of fiber response to temperature, ultrasound detection and the detection of longitudinal waves generated by a Q-switched laser on aluminum and steel samples, as shown in this work. The high robustness allows the system to be embedded and to operate in harsh environments such as factories, bringing the interferometry outside the laboratory.

Disertační práce se zabývá chováním a odezvou elastohydrodynamického (EHD) mazacího filmu za neustálených provozních podmínek. V úvodní části práce jsou shrnuty poznatky z oblasti EHD mazání; od jeho historie, přes základní mechanismy mazání a používané experimentální metody, až po nedávno publikované studie zaměřené na transientní podmínky. Hlavním cílem práce bylo experimentálně objasnit vliv provozních parametrů a reologických vlastností maziv na chování mazacího filmu v bodovém kontaktu při jeho nárazovém zatěžování a vystavení příčným vibracím. Za tímto účelem byla vyvinuta laboratorní zařízení umožňující měření rozložení mazacího filmu a tření za kontrolovaných nestacionárních podmínek. Experimenty odhalili zásadní roli přibližovacích a zatěžovacích rychlostí na formování stlačených mazacích filmů při nárazovém zatěžování. Výsledky byly srovnávány s nedávným teoretickým řešením. Bylo ukázáno na jeho nedostatky, jež byly následně odstraněny implementací empirických vztahů zohledňujících reologii maziv. V případě příčných vibrací byly nalezeny hranice selhání mazacího filmu a určeny vztahy popisující vliv příčných vibrací na centrální tloušťku filmu a její fluktuace jednotně pro všechny maziva. Závěrečná část práce poskytuje nový pohled na reologii maziv pomocí inovativního přístupu měření třecích reakcí maziva současně ve dvou směrech kontaktu za podmínek příčných vibrací. Tyto původní výsledky rozšiřují pochopení mechanizmů EHD mazání a mohou být použity k dokonalejším návrhům strojů, a vylepšit tak jejich účinnost, spolehlivost a životnost.

The main objective of this diploma thesis is to determine the influence of synovial fluid compodition and the influence of surface microtextures on lubrication of hip join replacements. For all experiments, hip joint simulator based on the pendulum principle was utilized. Metal heads (CoCrMo) manufactured by B Braun company and and tailor made acetabular cups from optical glass were used as contact couples. Acetabulum dimensions were fabricated according to dimensions of real implants. Experiments with surface microtextures simulated walking cycle for 210 s and development of lubrication film over time was observed.Results have shown that all types of tested structures improved lubrication of contact area, where the best results were obtained for square and triangle shapes respectively. Second set of experiments was based on the fact, that the composition of synovial fluid of healthy people differs from the composition of patients with various stages of osteoarthritis. Therefore, experiments with different model fluids were compared, which in their composition correspond to different groups of patients. For the model fluid that corresponds to the largest number of cases, experiments with individual components and combinations thereof were subsequently performed to provide a more detailed description of how these components affect the film-forming mechanism. The results show, that a change in fluid composition of patients with osteoarthritis can have a major negative effect on fluid formation process within the pair.

This diploma thesis deals with the experimental study of the influence of operating conditions on the tribological aspects of the wheel flange and rail gauge contact. The wheel flange contact occurs when the vehicle moves on a curve track and it leads to severe up to catastrophic wear regime. For effective reduction of wear is important to apply a suitable amount of lubricant at appropriate intervals into the contact. The issue in this work comprehensively studies using of three laboratory apparatus and six methods that are theoretically and experimentally compared. Assessed are friction, wear, distribution and film thickness of lubricants for different contact conditions. The resulted amount of lubricant and interval of its application eliminates development of seizure at low consumption of lubricant. The understanding of mechanisms that occur in the wheel-rail contact not only helps to reduce operating costs and improved to energy efficiency of movement of vehicle on a track, but it is the basis for safe, reliable and ecological operation of rail transport.

The master's thesis is concerned with design and execution of an experimental acetabulofemoral joint simulator. Its primary use is the study of lubrication film thickness in hip implants. The work first describes available hip joint simulators, which simulate particular joint positions. Next, the thesis proposes author’s own designs and solutions. The result is a produced device allowing for dynamic change of load in simulation of hip joint flexion and extension as set by ISO standard. Contact is recorded by an optical apparatus composed of a high-speed camera and a microscope. The work also includes the initial testing experiment and the complete design documentation of the device including electrical wiring diagrams.

Dizertační práce se zabývá mechanismy mazání v náhradách kyčelního kloubu. Byla provedena systematická studie formování proteinového filmu při zahrnutí různých materiálů a provozních podmínek. Hlavní pozornost je přitom věnována roli jednotlivých proteinů obsažených v synoviální kapalině při současné přítomnosti dalších proteinů. Jelikož metody aplikované v předchozích studiích neumožňovaly separovat jednotlivé složky maziva, byla vyvinuta optická měřící metoda na principu fluorescenční mikroskopie. Z důvodu verifikace metody byly provedeny dvě nezávislé studie zaměřené na měření tloušťky mazacího filmu a dělení maziva na výstupu mazaného kontaktu. Z důvodu určitých limitací fluorescenční mikroskopie byla dále využita i metoda optické interferometrie, jejíž využití je ilustrováno ve studii zabývající se formováním mazacího filmu v náhradách kyčelního klubu při uvažování reálné konformity třecích povrchů. Závěrečná část práce představuje nový metodologický přístup založený na in situ pozorování kontaktní oblasti umožňující popsat roli jednotlivých proteinů ve vztahu k vývoji tloušťky mazacího filmu. Práce obsahuje originální výsledky, které přináší nové poznání v oblasti biotribologie náhrad kyčelního kloubu vedoucí k dalšímu vývoji implantátů při snaze zabránit jejich selhání v důsledku omezené životnosti.

Orientador: Cláudio Kitano / Resumo: Nesta dissertação de mestrado é apresentado um vibrômetro para a medição de deslocamentos nanométricos. O vibrômetro proposto está baseado em um interferômetro de Michelson modificado, homódino e em malha fechada. A demodulação em tempo real é executada inteiramente em modo digital, utilizando uma plataforma embarcada que realiza a aquisição de dados, processamento dos sinais, controle PI (proporcional-integral) e a geração dos sinais que acionam o modulador de fase óptica (baseado em uma célula Pockels) e o atuador piezoelétrico sob estudo. Dois sinais em quadratura de fase são obtidos a partir de um único sinal interferométrico utilizando uma tensão de modulação principal e, em seguida, a conhecida técnica de multiplicação cruzada é aplicada para calcular a variação da fase óptica de interesse. A condição de quadratura é atingida pelo próprio controlador PI por meio da análise da figura de Lissajous dos sinais fora de fase. O novo vibrômetro óptico é capaz de medir deslocamentos nanométricos, e é simples, barato, exato, imune ao desvanecimento e auto-consistente. O controlador PI é robusto, uma vez que o método de demodulação é capaz de trabalhar com elevado ruído eletrônico, variações indesejáveis no ganho do amplificador e na tensão de meia-onda da célula Pockels com a temperatura e outras perturbações externas. O novo sistema foi utilizado para determinar a magnitude da resposta em frequência de dois protótipos de atuadores piezoelétricos flextensionais multiatuados. As ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: A vibrometer to measure nanometric displacements is presented in this work. The proposed vibrometer is based on a modified closed loop homodyne Michelson interferometer. Real-time phase demodulation is carried out entirely in a digital mode, using an embedded platform that performs data acquisition, signal processing, PI (proportional-integral) control and the generation of signals that drive the electrooptic Pockels cell phase shifter and the piezoelectric actuator under test. Two phase quadrature signals are generated from a single interferometric output, using the interleaving action, in alternation, of a digitally generated principal modulating signal, and then the well-known cross-multiplication technique is applied to perform the computation of the phase shift of interest. The quadrature condition is reached by the PI control itself, using the length difference between the major axis and the minor axis of the ellipse formed by the Lissajous figure associated with the out of phase signals as the controller error signal. The new optical vibrometer is capable of measuring nanometric displacements, and is simple, inexpensive, accurate, immune to fading and self-consistent. The PI controller is robust, since the demodulation method is able to work under high electronic noise, undesirable variations in Pockels cell half-wave voltage with temperature, amplifier gain and other external entrances. The new method was used to determine the displacement frequency response curves of... (Complete abstract click electronic access below) / Mestre

This PhD thesis deals with elastohydrodynamic lubrication (EHL) under the conditions that occur between mated hypoid gear teeth. The aim is to describe experimentally the behaviour of lubricating film and mechanisms of its formation. The focus is mainly placed on clarifying the influence of direction and magnitude of sliding velocity in circular and elliptical contacts. Generally, it is still assumed that the direction of sliding velocity has no effect on the resulting lubricant film. In this study optical interferometry is used to determine distribution of lubricant film thickness. This work includes new and original results which clarify the studied problem. It was found that the direction of sliding velocity affects shape of the film at high speeds. This relates to the effect on heat flow through the contact. The results have an impact on the development of general EHL theory and provide knowledge applicable in film thickness prediction in the design of real tribological nodes.

No description available.