Os transformadores são equipamentos fundamentais para o sistema elétrico e o acompanhamento regular de suas condições de operação é muito importante para que se reduzam custos associados ao seu ciclo de vida, bem como para que se possa garantir a sua confiabilidade e a sua durabilidade. As falhas elétricas ocorrem, muitas vezes, motivadas pela degradação do sistema isolante e consequentemente danificam o equipamento. O óleo é um dos componentes isolantes que se deteriora com facilidade devido ação de falhas ou variação de temperatura e umidade. O acompanhamento e a manutenção da qualidade do óleo isolante são etapas essenciais para proporcionar uma operação confiável dos equipamentos elétricos garantindo a confiabilidade do fornecimento de energia. Um dos parâmetros que pode ser monitorado no óleo é a água, pois esta reduz drasticamente a rigidez elétrica do dielétrico. Uma revisão na literatura relata alguns procedimentos de diagnósticos disponíveis para avaliar a condição do óleo de transformadores, tais como as análises físico química e a análise de gases dissolvidos (DGA). Pesquisas recentes revelam um tópico ressaltado que consiste na utilização de sensores acústicos para caracterização de líquidos, uma vez que essa análise possui a vantagem de ser não destrutiva, com possibilidade de aplicações não invasivas e em transformadores em operação. Neste contexto, esta tese propõem uma metodologia acústica para contribuir na detecção de umidade no óleo mineral isolante utilizando sensores piezoelétricos. A metodologia consiste na utilização de sensores para emitir e recepcionar os sinais transmitidos através de amostras de óleos de transformadores. Os experimentos foram realizados na faixa de MHz, utilizando transdutores comerciais e na faixa de kHz, utilizando um transdutor piezoelétrico desenvolvido pelo Grupo de Alta Tensão e materiais da USP de São Carlos. Medidas da amplitude do sinal são correlacionadas com o teor de água contido nas amostras de óleos. Os resultados revelam que é possível diagnosticar se as amostras de óleo estão aptas ou não para uso em transformadores. Em alguns casos é possível distinguir as quatro classes das amostras de óleo mineral isolante testadas: óleo novo (virgem), óleo regenerado, óleo sujo e óleo queimado. A metodologia proposta, além de ser inédita, se mostra promissora para auxiliar no diagnóstico de amostras de óleo mineral isolante em campo. / Transformers are fundamental equipment in electrical power system and constant monitoring their operating conditions is very important to reduce the costs associated with their life cycle, as well as to guarantee their reliability and durability. One of the main cause of electrical failures in power transformers is the degradation of the power transformer insulation system, which can cause permanent damages. A crucial element in their insulation system is oil used to insulate parts, but also to cool the equipment. Therefore monitor and maintain the insulating oil are essential steps to provide a reliable operation of the electrical equipment guaranteeing the reliability of the power supply. A review in the literature reports a wide variety of diagnostic procedures available to assess the condition of transformer oil, such as physical chemical analysis and dissolved gas (DGA) analysis. Recent research reveals a highlighted topic that consists of the use of acoustic sensors for characterizing liquids, since the acoustic analysis presents the characteristic of being non-destructive with possibility of non-invasive and application during transformer operation i.e. in line. In this context, this thesis proposes an acoustic methodology for the analysis of mineral insulating oil using piezoelectric sensors. The methodology consists of the use of sensors to emit and receive signals transmitted through oil transformer samples. The experiments were carried out in the MHz band, using commercial transducers and in the kHz band, using a piezoelectric transducer developed by the High Voltage and Materials Group from USP of São Carlos. Measurements of signal amplitude are correlated with the water content contained in the oil samples. The results show that it is possible to diagnose whether or not the oil samples are suitable for use in transformers. In some cases it is possible to distinguish the four classes of tested mineral oil samples. The proposed methodology is promising for the diagnosis of mineral insulation oil samples in the field.

A força dos músculos Abdutor curto do polegar (ACP) e Abdutor do quinto dedo (AQD) serve como parâmetro para a avaliação da função dos nervos mediano e ulnar, respectivamente. Um aparelho foi desenvolvido para realizar a medida da força daqueles músculos em mãos de diferentes tamanhos, com a mesma eficiência. Este aparelho foi construído inteiramente com materiais de fácil obtenção e baixo custo, incluindo o aço, o latão, o alumínio e o duralumínio, e consiste de uma base dotada de uma coluna rígida para a fixação de um transdutor de força do tipo resistivo (célula de carga) e de um apoio para a mão para mantê-la firme durante os testes. Acessórios foram construídos segundo medidas antropométricas previamente obtidas nos polegares e quintos dedos voluntários, de modo que pudessem ser acoplados à célula de carga e permitir a avaliação de mãos direitas e esquerdas de diferentes tamanhos. A célula de carga foi calibrada. Quando pronto, o protótipo final foi utilizado para medir a força dos músculos ACP e AQD de 42 voluntários, sendo 20 mulheres e 22 homens, cujo critério de inclusão era a total ausência de qualquer patologia nos membros superiores. Dois pontos de aplicação da carga foram selecionados, sendo um proximal, no nível da falange proximal, e outro distal, no nível da falange distal. Três medidas eram tomadas para cada ponto de aplicação da carga, para cada um dos músculos, e uma média foi obtida para uso na análise estatística dos resultados, que mostraram que a força de ambos os músculos era consistentemente maior nos homens e na mão direita. Quanto aos dois pontos de aplicação da carga, a força foi sempre maior no ponto proximal, tanto para o polegar, como para o quinto dedo. A avaliação geral do desempenho do aparelho mostrou que ele é versátil, fornecendo informações confiáveis para as mãos direitas e esquerdas de todos os tamanhos. / The strength of the Abductor pollicis brevis and Abductor digiti quinti muscles may serve as a parameter to the evaluation of the median and ulnar nerve function, respectively. A device was developed especially for carrying out measurements of the strength of those muscles in hands of different sizes with the same efficiency. The device was built entirely with easily obtained low cost materials, including steel, solid brass, aluminium and duralumin, and consists of a metal base provided with a rigid colunm for fixation of a resistive type strength transducer (load cell) and a hand stand to keep the hand still while in test. Accessories were built according to a previous anthropometric measurement of both thumb and fifth fingers of volunteers, so as to be coupled onto the load cell and allow for the evaluation of the strength of different size hands. The load cell was calibrated. Once ready, the final prototype was used to measure the strength of the APB and AbDQ muscles in 42 volunteers, being 20 women and 22 men, whose inclusion criterion was the total absence of any pathology in the upper limbs. Two points of load application were selected, being one proximal, at the level of the proximal phalanx, and another one distal, at the level of the distal phalanx. Three measurements were taken for each point of load application for both muscles, an average value being obtained for use in the statistical analysis of the results, which showed that the strength was consistantly greater in men and in the right hand. As refers to the different points of load application, the strength was always greater at the proximal point, both for the thumb and the fifth finger. The overall evaluation of performance of the prototype showed that it is versatile, supplying reliable information for all size hands.

Os termo eletretos piezelétricos de teflon FEP apresentam-se como elementos que podem competir em preço e funcionalidade com os transdutores atuais. Quando carregados impulsivamente, as folhas de teflon FEP retêm cargas elétricas superficiais por um período longo, superior a 500 anos. Excitados mecanicamente, resultam em um alto nível de sinal elétrico e, excitados eletricamente, retornam a energia em deformação mecânica. O processo de fabricação projetado envolve a produção de um transdutor piezelétrico com uma densidade superficial de carga uniforme, através da formação de vacúolos gasosos formados sobre a superfície do filme polimérico. Os altos índices piezelétricos dos transdutores fabricados são confirmados por um sistema de medição estático, também projetado e desenvolvido neste trabalho, onde o coeficiente piezelétrico é medido de maneira direta. / The thermo-formed electrets of teflon FEP films are shown as elements that can be competitive either in price and functionality matters, as per the transducers being used nowadays. Once charged by an impulse voltage, the teflon FEP sheets keep the superficial electric charges for long periods, up to 500 years. Mechanically excited, they result in a high electric signal and, once electrically excited, return in a mechanical deformation. The projected manufactory process includes the production of a piezoelectric transducers with uniformly charged superficial density, though the formation of gaseous vacuoles over the polymeric film surface. The high piezoelectric levels of the manufactured transducers are confirmed by a static measurement system, also projected and developed in this same work, where the piezoelectric coefficient is measured by a direct way.

Os equipamentos elétricos instalados em linhas de transmissão e distribuição de energia são normalmente submetidos a condições anormais e intensos campos elétricos, que, eventualmente, levam, entre outros fenômenos, as descargas parciais (DPs). Estas descargas têm sido apontadas como uma das principais causas de falhas de equipamentos e envelhecimento precoce. Portanto, detectar DPs se tornou uma questão importante na busca de uma energia elétrica eficiente e confiável. No que se refere a detecção de DPs existem vários sensores que podem ser aplicados, a exemplos: óptico, magnético ou acústico, e cada um deles apresentando vantagens particulares e limitações. Uma das desvantagens de tais sensores é o custo elevado, o que restringe o monitoramento de DPs no âmbito da distribuição de energia mais especificamente em transformadores de potência. Embora, se o foco do monitoramento é apenas detectar a ocorrência de DPs, uma nova classe de sensores acústicos implementados com piezoeletretos pode ser uma alternativa econômica viável. Deste modo, nesta dissertação, foi investigado o comportamento acústico de tais transdutores expostos a diferentes condições de DPs, onde o sensor piezoelétrico foi utilizado na detecção de DPs produzidas por uma configuração de eletrodos ponta - ponta separados por diferentes gaps de ar (único ou múltiplo) e excitado por altas tensões alternadas. As amplitudes dos sinais registrados foram correlacionadas com a distância do gap e com a amplitude da tensão aplicada. A partir dos resultados obtidos foi possível observar que a intensidade do som das DPs, capturado com o transdutor piezoelétrico, está relacionada com o tamanho do gap e da amplitude da tensão, como relatado na literatura. / Electrical equipment installed in power transmission and distribution lines are usually subjected to abnormal conditions and intense electric fields, which eventually lead, among others phenomena, to partial discharges (PDs). These discharges have been pointed as one of the main causes of equipment failures and premature aging. Therefore, detect PDs became an important issue in the prospect of efficient and reliable electric energy. Concerning PD detection there are several sensors that can be employed e.g. optical, magnetic or acoustic, and each of them presenting particular advantages and limitations. One of the drawback of such sensors is their elevated cost, which restricts the PD monitoring within the distribution of energy more specifically in power transformers. Although, if the intention of monitoring is only to detect the PD occurrence a new class of acoustic sensors implemented with piezoelectrets may be a feasible economic alternative. Therefore, in this work was investigated the acoustic behavior of such transducers exposed to different PD conditions, for instance, the piezoelectret sensor was employed on the detection of PD produced by a single or multiple point-to-point electrode setup with different air gaps excited by high AC voltages. The recorded signals amplitudes were correlated with the gap distance and voltage amplitude applied. Based on the results obtained it was observed that the intensity of the DPs sound, captured with the piezoelectric transducer, is related to the size of the gap and voltage amplitude, as reported in the literature.

Os equipamentos elétricos instalados em linhas de transmissão e distribuição de energia são normalmente submetidos a condições anormais e intensos campos elétricos, que, eventualmente, levam, entre outros fenômenos, as descargas parciais (DPs). Estas descargas têm sido apontadas como uma das principais causas de falhas de equipamentos e envelhecimento precoce. Portanto, detectar DPs se tornou uma questão importante na busca de uma energia elétrica eficiente e confiável. No que se refere a detecção de DPs existem vários sensores que podem ser aplicados, a exemplos: óptico, magnético ou acústico, e cada um deles apresentando vantagens particulares e limitações. Uma das desvantagens de tais sensores é o custo elevado, o que restringe o monitoramento de DPs no âmbito da distribuição de energia mais especificamente em transformadores de potência. Embora, se o foco do monitoramento é apenas detectar a ocorrência de DPs, uma nova classe de sensores acústicos implementados com piezoeletretos pode ser uma alternativa econômica viável. Deste modo, nesta dissertação, foi investigado o comportamento acústico de tais transdutores expostos a diferentes condições de DPs, onde o sensor piezoelétrico foi utilizado na detecção de DPs produzidas por uma configuração de eletrodos ponta - ponta separados por diferentes gaps de ar (único ou múltiplo) e excitado por altas tensões alternadas. As amplitudes dos sinais registrados foram correlacionadas com a distância do gap e com a amplitude da tensão aplicada. A partir dos resultados obtidos foi possível observar que a intensidade do som das DPs, capturado com o transdutor piezoelétrico, está relacionada com o tamanho do gap e da amplitude da tensão, como relatado na literatura. / Electrical equipment installed in power transmission and distribution lines are usually subjected to abnormal conditions and intense electric fields, which eventually lead, among others phenomena, to partial discharges (PDs). These discharges have been pointed as one of the main causes of equipment failures and premature aging. Therefore, detect PDs became an important issue in the prospect of efficient and reliable electric energy. Concerning PD detection there are several sensors that can be employed e.g. optical, magnetic or acoustic, and each of them presenting particular advantages and limitations. One of the drawback of such sensors is their elevated cost, which restricts the PD monitoring within the distribution of energy more specifically in power transformers. Although, if the intention of monitoring is only to detect the PD occurrence a new class of acoustic sensors implemented with piezoelectrets may be a feasible economic alternative. Therefore, in this work was investigated the acoustic behavior of such transducers exposed to different PD conditions, for instance, the piezoelectret sensor was employed on the detection of PD produced by a single or multiple point-to-point electrode setup with different air gaps excited by high AC voltages. The recorded signals amplitudes were correlated with the gap distance and voltage amplitude applied. Based on the results obtained it was observed that the intensity of the DPs sound, captured with the piezoelectric transducer, is related to the size of the gap and voltage amplitude, as reported in the literature.

Orientador: Cláudio Kitano / Banca: Ricardo Tokio Higuti / Banca: Ailton Akira Shinoda / Banca: Agnaldo Aparecido Freschi / Banca: Gefeson Mendes Pacheco / Resumo: Nesta tese, cinco novas técnicas de demodulação de fase óptica são propostas, as quais constituem versões melhoradas do método espectral J1...J4 clássico. As técnicas são adequadas para uso com sistemas interferométricos de dois feixes, homódinos, operando em malha aberta e sob excitação senoidal. As novas técnicas, aqui denominadas de métodos J1/J3A, J1...J3, Jm/Jm+2 e J0...J3, para medição do índice de modulação de fase, e, um novo método de medição da fase quase-estática, são de fácil implementação, não sendo afetadas pelo desvanecimento de sinal detectado, instabilidade da fonte óptica e visibilidade das franjas de interferência, possibilitando medições em tempo real. Os novos métodos espectrais foram avaliados com ruído branco, 1/f2 e fase quase-estática aleatória, usando o Matlab. Além disso, simulações dinâmicas realizadas no Simulink evidenciaram as vantagens dos novos métodos, que também foram testados em dois experimentos distintos: o primeiro foi direcionado à medições de tensões elétricas senoidais, usando um sensor óptico de tensão (SOT), baseado numa célula Pockels de cristal de niobato de lítio; o segundo, foi dedicado à medições de amplitudes de deslocamentos nanométricos de um atuador piezoelétrico flextensional (APF), usando-se um interferômetro de Michelson. Por ser um sistema que pode ser modelado analiticamente, o SOT serviu para validar os novos métodos espectrais. A caracterização de APF's usando os novos métodos ópticos é a aplicação relevante desta tese. Medições de deslocamentos no APF, desde a faixa subnanométrica até a micrométrica, realizadas usando-se os métodos J0...J3 e Jm/Jm+2, permitiram analisar sua linearidade e resposta em freqüência, as quais foram comparadas com os resultados obtidos com um analisador de impedâncias vetorial. Ambos os resultados experimentais, ...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, five novel optical phase demodulation techniques are proposed, which overcome some of the limitations of the J1…J4 classical method. These improved techniques are applied with two beams, homodyne, open loop and sinusoidal phase modulation interferometer systems. These new techniques, named in this work as "J1/J3A, J1...J3, Jm/Jm+2 and J0...J3 methods," which are applied to phase modulation index measurements, and "the novel method for quasi-static phase measurements," are of simple implementation, and are unaffected by signal fading, laser source instabilities or changes in fringe visibility. In addition they allow real time measurements. The new methods were evaluated with white noise, 1/f2 noise and random fading, using Matlab/Simulink, making evident their advantages in relation to the classical methods. These methods were also tested in two experiments: the first one, corresponds to an optical voltage sensor (OVS), based on lithium niobate Pockels cell; the second one, refers to the measurement of nanometric displacement amplitudes of a piezoelectric flextensional actuator (PFA), by using a Michelson interferometer. Because the OVS has an analytic response, it was suitable to validate the new spectral methods. The characterization of the PFA by using the new optical methods is the main application of this thesis. PFA displacements, from sub-nanometer up to micrometer range were detected by applying the J0…J3 and Jm/Jm+2 methods. By measuring the PFA displacements, the linearity and frequency response of the PFA were evaluated. To confirm the observed frequencies of resonance an impedance analyzer was used to measure the magnitude and phase of the PFA admittance. Results obtained for the OVS and PFA systems, with the new methods and those produced by the J1...J4, J1...J6-neg, J1...J6-pos and J0...J2 classic methods, ...(Complete abstract, click electronic access below) / Doutor

L’utilisation de revêtements et de couches minces déposés sur substrats est très recherchée dans de nombreuses applications. Les objectifs de ces revêtements et dépôts sont multiples (améliorer la durabilité des structures, leur résistance à l’usure et à la fatigue, etc.). D'autre part, les matériaux à gradient sont également développés en vue de répondre à de nouvelles exigences fonctionnelles, comme de meilleures tenues en température, en usure, en corrosion. Pour toutes ces applications, la caractérisation de ces revêtements et de ces matériaux à gradients, afin d’en déterminer leurs propriétés (épaisseur, constantes élastiques, adhérence, contraintes résiduelles, …etc), est déterminante pour le contrôle santé des pièces et pour leur fonctionnement optimal au cours de leur utilisation. Pour caractériser ces structures, nous avons choisi d’exploiter la dispersion des ondes de surface sur une large gamme de fréquences (10 à 60 MHz). Afin d’exciter ces ondes, des capteurs MEMS de type IDT-SAW ont été réalisés à différentes fréquences couvrant la totalité de la gamme fréquentielle considérée. L’excitation quasi-harmonique a été privilégiée dans le but d’obtenir des mesures précisesde vitesses de phase. Nous avons montré les potentialités de cette approche en caractérisant premièrement des structures à couche mince allant jusqu’à 500 nm et deuxièmement des structures amorphes à gradient de contraintes. / The use of coatings and thin layers deposited on substrates is highly sought in many applications. The objectives of these coatings and deposits are multiple (improve the durability of structures, their wear resistance and fatigue, etc.). On the other hand, gradient materials are being developed to meet new functional requirements, such as a better resistance to temperature, wear and corrosion. For all of these applications, the characterization of these coatings and gradient materials, in order to determine their properties (thickness, elastic constants, adherence, residual stresses, etc…), is decisive for the health control of pieces and for their optimum operation during their use. To characterize these structures, wechose to exploit the dispersion of surface acoustic waves over a wide frequency range (10 to 60 MHz).To excite these waves, SAW-IDT MEMS sensors have been carried out at different frequencies covering the entire frequency range we considered. The quasi-harmonic excitation was preferred to obtain accurate measures of phase velocities. We showed the potential of this approach by characterizing, first, thin layers structures (500 nm) and second, amorphous structures with a stressesgradient.

[pt] A presente dissertação apresenta o desenvolvimento de um transdutor de pressão de alta sensibilidade, desenvolvido para aplicações biomédicas. O transdutor é baseado em um sensor de magnetoimpedância gigante (MIG), anteriormente desenvolvido, pelo Laboratório de Biometrologia da PUC-Rio. O conhecimento a cerca das principais características do fenômeno MIG serviu de guia para as ações que foram tomadas, a fim de se estabelecer uma configuração que apresentasse maior sensibilidade ao transdutor. Mesmo que algumas dificuldades encontradas, principalmente devidas a características acústicas não levadas em consideração, apontem para a necessidade de aperfeiçoamentos, com a configuração desenvolvida no presente trabalho já é possível obter o registro do pulso arterial carotídeo. Comparações entre o transdutor ora desenvolvido e com outros transdutores de pressão existentes no mercado também destinados a aplicações biomédicas, apontam para uma sensibilidade do transdutor ora desenvolvido de magnitude igual ou mesmo superior aos convencionais. / [en] This dissertation presents a high sensitivity pressure transducer, developed for biomedical applications. The transducer is based on a Giant Magnetoimpedance (GMI) sensor previously developed at the Laboratory of Biometrology of PUC-Rio. Knowing the main characteristics of the phenomenon and of the GMI strips used, the configuration which should yield the highest possible sensitivity has been implemented. Even though some enhancements in the acoustic characteristics of the transducer are still necessary, it was already possible to record the carotid arterial pulse. Comparing the transducer herein presented with other pressure transducers also destined to biomedical applications, it already has a sensitivity of the same order of magnitude or even higher.

Doctor of Philosophy(PhD) / Soil Stiffness is an important parameter for any geotechnical engineering design. In laboratory tests it can be derived from stress-strain curves or from dynamic measurement based on wave propagation theory. The second method is a more accurate and direct method for measuring stiffness at very small strains. Until now dynamic measurements have usually been obtained manually from the triaxial test. Attempts have been made to automate the procedure but have apparently failed due to the high level of variability in dynamic measurements. Moreover, triaxial tests of soil can be very lengthy and manual dynamic measurements can be very tedious and impractical for long stress-path tests. In this research a computer program has been developed to automate the stiffness measurement (using bender elements) based on the cross- correlation technique. In this method the program records all the peaks and corresponding arrival times in the cross-correlation signal during the test. The stiffness is calculated and displayed on the screen continuously. The Bender Element enabled to get the small strain shear modulus. An arbitrary “Chirp” waveform of 4 kHz frequency was used for this purpose. Subsequently Bender Element test results were checked by ‘Sine’ waveforms of frequencies 5kHz to 20kHz, as well as by manual inspection of the arrival time. This thesis discusses the method and some of the difficulties in truly automating the process. Finally some results from a number of stress path tests on uncemented and cemented calcareous sediments are presented. Bender elements have been used by many researchers to determine the shear modulus at small strain. Most previous studies have used visual observation of arrival time, which is time consuming and often requires some judgement from the operator. This thesis will describe the use of cross-correlation as a method for automation of Gmax measurement. Cross-correlation has been claimed to be unreliable in the past. However, it will be shown that provided several peaks in the cross-correlation signal are monitored it is possible to follow the variation of Gmax throughout consolidation and shearing. The measurement can be made at regular intervals within the software controlling a stress-path apparatus. Details of the apparatus used and practical considerations including selection of waveform and frequency are discussed. A series of drained cyclic triaxial tests was carried out on artificially cemented and uncemented calcareous soil of dry unit weights 13, 15, and 17 kN/m3 and sheared with constant effective confining stress 300 kPa. Gypsum cement contents of 10%, 20% and 30% of the dry soil weight were used. In addition a series of stress path tests were performed on Toyuora sand samples. Results will be presented for two uncemented and one cemented sand. In addition to the bender elements, all tests had internal instrumentation to monitor axial and lateral strains. Results will be presented for Toyura sand to show that the measurements are consistent with those obtained by other methods. Results will also be presented for carbonate sand subjected to a wide range of stress paths. Finally, results will be presented for the carbonate sand cemented with gypsum. The degradation of Gmax of the cemented soil subjected to variety of monotonic and cyclic stress-paths is presented. Analysis of the results includes assessment of the factors influencing Gmax for uncemented sand. Preliminary analysis indicates that in order of importance these are the mean effective stress, the stress history, void ratio and stress ratio. For cemented sand, Gmax is initially constant and independent of stress path. After yielding the modulus degrades, becoming increasingly stress level dependent and eventually approaches the value for uncemented sand. Factors influencing the rate of degradation are discussed. For the Toyuora sand samples the effects of end restraint on the stress-strain response at small strains were investigated. The conventional method of mounting triaxial specimen has the effect of introducing friction between sample and end platen during a compression test. This inevitably restricts free lateral movement of the specimen ends. Frictional restraint at the sample ends causes the formation of 'dead zones' adjacent to the platens, resulting in non-uniform distribution of stress and strain (and of pore pressure if undrained). On the other hand the specimen with 'free' ends maintain an approximate cylindrical shape instead of barrelling when subjected to compression, resulting in a more uniform stress distribution.

The objectives of the thesis work were to study theinteraction between embedded piezoceramic transducers andcomposite structures as well as determine techniques tosimplify the Lamb waves analysis. Firstly, this studyconsidered the design of the embedded piezoceramic transducers.Secondly, the effect of the embedded transducer on thecomposite strength as well as the influence of the mechanicallyloaded composite on the characteristics of the embeddedtransducer were investigated. Finally, to simplify the analysisof such complex Lamb wave responses, two techniques weredeveloped. They were based on the wavelet technique and amodelling technique, respectively. The design of the embedded piezoceramic transducers wasimproved by reducing the stress concentrations in the compositeas well as in all components constituting the piezoceramictransducer, that is, the piezoceramic element, interconnectorand conductive adhesive. The numerical analysis showed that thethickness of the interconnector had no significant influence onthe stress state of the piezoceramic transducer. It was alsofound that a compliant conductive adhesive reduced the stressconcentration located at the edge of the piezoceramic element.The structural integrity of composites embedded with theimproved piezoceramic transducer was investigated. Theexperiments, performed in tensile and compressive staticloading, indicated that the strength of the composite was notsignificantly reduced by the embedded piezoceramic transducer.Further investigations were conducted to evaluate theperformance of the improved piezoceramic transducer used as aLamb wave generator embedded in composites subjected tomechanical loading. The tests were conducted in tensile andcompressive static loading as well as fatigue loading. Thestudy showed a large working range of the embedded piezoceramictransducer. A post processing technique based on the waveletswas further assessed in the detection of damage and in thedamage size evaluation. A new wavelet basis was developedspecially for processing the Lamb wave response. This method,focused on the wavelet coefficients from the decomposition Lambwave response, showed promising results in evaluating thedamage size. The wavelets offered a sensitive tool to detectsmall damage, compared to other detection methods, improvingthe damage detection capabilities. The other technique wasdevoted to the simplification of the generated Lamb waves bythe use of multi-element transducers. The transducers weredesigned using both a normal-mode expansion and a FE-method.This technique allowed reducing the effect of a Lamb wave modetowards another. This technique was successfully implemented ina damage detection system in composites. <b>Keywords:</b>Embedded piezoceramic, transducer, composite,structural integrity, health monitoring, damage detection, Lambwaves, wavelets, normal-mode expansion, FE-method