Parmi les méthodes appliquées dans le cadre de la maintenance des installations industrielles, l'analyse vibratoire constitue une des plus répandues. En effet, les signatures vibratoires apparaissant sur une installation en cours de fonctionnement sont étroitement liées à leur comportement dynamique et à leur état fonctionnel. Ce travail a pour objectif de développer et expérimenter des techniques et outils de calculs numériques pour l'interprétation d'indicateurs d'état issus de mesures vibratoires sur une machine tournante. La validation est faite sur un ensemble motoréducteur à engrenages. Pour cela, nous avons développé deux outils d'analyse numérique : un premier permettant de déterminer les caractéristiques modales d'une structure complexe puis un second, développé sur la base des ondelettes, pour détecter les défauts naissants sur un motoréducteur. Les performances relatives des différents outils sont comparées au regard de ce qui se fait dans la littérature. Enfin, une étude expérimentale sur banc d'essais a été menée dans le but de tester la sensibilité et les limites de la méthode. Le mémoire est articulé comme suit : une première partie développe les principales techniques vibratoires actuelles avec leurs performances et limites. De la deuxième partie traitant les théories et méthodes d'analyse modale découle une troisième présentant des méthodes améliorées. Dans la quatrième partie, une étude expérimentale sur banc d'essais a été menée dans le but de tester la sensibilité de la méthode. Une approche par la décomposition en ondelettes des signaux a été notamment utilisée. Il est démontré que cette méthode a une application intéressante dans le domaine des analyses vibratoires de structures complexes

Les matériaux viscoélastiques sont utilisés dans tous les domaines de l'ingénierie et des systèmes mécaniques, de l'électroménager, spatial, l'automobile, l'aéronautique ou le génie civil (ponts...) grâce à leur capacité d'amortir les chocs ou de filtrer les vibrations. Ce travail constitue une contribution à l'étude du comportement dynamique non linéaire des composants viscoélastiques notamment les élastomères. Dans ce mémoire, on introduit, d'abord, les propriétés mécaniques des élastomères, pour les aspects viscoélasticité et friction. Un rappel des différents phénomènes physiques et une liste non-exhaustive des modèles existants dans la littérature sont présentés. Ensuite, on propose des techniques expérimentales afin de décrire le comportement dynamique sous sollicitations uniaxiales d'un élastomère. Une description des bancs d'essais, des chaines d'analyse vibratoire, des méthodes de traitement des données des essais et d'analyse des mesures expérimentales est détaillée dans ce manuscrit. Une nouvelle approche du modèle de Maxwell généralisé a été proposée pour décrire le comportement dynamique du composant viscoélastique. Ce modèle permet une description précise et une bonne connaissance du comportement dynamique des composants viscoélastiques en fonction de l'amplitude, de la précharge et de la fréquence. La dissipation d'énergie identifiée sous forme d'amortissement peut être issue de l'amortissement intrinsèque des matériaux polymère comme de la friction aux interfaces dans le cas de composants caoutchoucs non adhérisés sur les pièces, dans ce travail, un nouveau modèle visco-tribologique a été développé en couplant les propriétés rhéologiques linéaires du modèle de Maxwell généralisé et le modèle de frottement de Dahl pour la description du comportement de frottement hystérétique des liaisons viscoélastiques non adhérisées.

La thématique de la thèse est très vaste. Sont présentées les grandeurs cinématiques locales ou régionales qui agissent sur le corps humain. La deuxième partie de la thèse décrit les méthodes optiques, par lesquelles on peut mesurer les vibrations produites par les machines-outils sur le système humain main-bras au cours de l'activité au travail. Dans la troisième partie sont donnés les effets négatifs des vibrations qui se produisent sur le système humain main-bras pendant l'exposition aux vibrations. La quatrième partie de cette thèse contient la base théorique des techniques optiques utilisées pour mesurer les vibrations. Le chapitre cinq présente la méthodologie d'expérimentation pour mesurer les vibrations. Les résultats des mesures sont indiqués dans le sixième chapitre de la thèse. Dans le chapitre sept on présente la modélisation mécanique et mathématique du système humain main-bras avec trois degrés de liberté et le dernier chapitre contient les conclusions finales.

A novel method of vibration modelling is proposed in this thesis. This method involves estimating the mode shapes of a general structure and describing these shapes in terms of fuzzy membership functions. These estimations or initial guesses are based on engineer's experience or physical insight into natural mode shapes assisted by end and boundary conditions and some rules. The guessed mode shapes were referred to as Mode Shape Forms (MSFs). MSFs are approximate mode shapes, therefore there are uncertainties involve with their values where this uncertainty is expressed by fuzzy sets. The deflection or displacement magnitude of the mode shape forms are described with Zero, Medium, and Large fuzzy linguistic terms and constructed using fuzzy membership functions and rules. Fuzzy rules are introduced for each MSF. In that respect fuzzy membership functions provides a means of dealing with uncertainty in measured data, it gives access to a large repertoire of tools available in fuzzy reasoning field. The second stage of the process addresses the issues of updating these curves by experimental data. This involves performing experimental modal analysis. The mode shapes derived from experimental FRFs collect a limited number of sampling points. When the fuzzy data is updated by experimental data, the method proposes that the points of the fuzzy data correspond to the sampling points of FRF are to be replaced by the experimental data. Doing this creates a new fuzzy curve which is the same as the previous one, except at those points. In another word a 'spiked' version of the original fuzzy curve is obtained. In the last stage of this process, neural network is used to 'learn' the spiked curve. By controlling the learning process (by preventing it from overtraining), an updated fuzzy curve is generated that is the final version of the mode shape. Examples are presented to demonstrate the application of the proposed method in modelling of beams, a plate and a structure (a three beams frame). The method is extended to evaluate the error where a wrong MSF is assumed for the mode shape. In this case the method finds the correct MSF among available guessed MSFs. A further extension of the method is proposed for cases where there is no guess available for the mode shape. In this situation the 'closest' MSF is selected among available MSFs. This MSF is modified by correcting the fuzzy rules that is used in constructing of the fuzzy MSF. Using engineering experience, heuristic knowledge and the developed MSF rules in this method are the capabilities that cannot be provided with any artificial intelligent system. This provides additional advantage relative to vibration modelling approaches that have been developed until now. Therefore this method includes all aspects of an effective analysis such as mixed artificial intelligence and experimental validation, plus human interface/intelligence. Another advantage is, MSF rules provide a novel approach in vibration modelling where enables the method to start and operate with unknown input parameters such as unknown material properties and imprecise structure dimensions. Hence the classical computational procedures of obtaining the vibration behaviour of the system, from these inputs, are not used in this approach. As a result, this method avoids the time consuming computational procedure that exhibit in existing vibration modelling methods. However, the validation procedure, using experimental tests (modal testing) is the same acceptable procedure that is used in any other available methods which proves the accuracy of the method.

A prototype low frequency, high amplitude, dual tine oscillating subsoiler was evaluated for deep loosening of compacted soil in Australian vineyards. The study determined the most efficient settings of frequency, amplitude and oscillation angle based on draft reduction, power saving and tractor vibrations.

Excitation of the low frequency vibrational modes of a submerged vessel can generate significant radiated noise levels. Vibrational modes of a submarine hull are excited from the transmission of fluctuating forces through the shaft and thrust bearings due to the propeller rotating in an unsteady fluid. The focus of this work is to investigate the structural and acoustic responses of a submarine hull under axial excitation. The submarine hull is modelled as a cylindrical shell with internal bulkheads and ring stiffeners. The cylindrical shell is closed by truncated conical shells, which in turn are closed at each end using circular plates. The entire structure is submerged in a heavy fluid medium. The structural responses of the submerged vessel are calculated by solving the cylindrical shell equations of motion using a wave approach and the conical shell equations with a power series solution. The displacement normal to the surface of the structure in contact with the fluid medium was calculated by assembling the boundary/continuity matrix. The far field radiated sound pressure was then calculated by means of the Helmholtz integral. Results from the analytical model are compared with computational results from a fully coupled finite element/boundary element model. The individual and combined effects of the various influencing factors, corresponding to the ring stiffeners, bulkheads, conical end closures and fluid loading, on the structural and acoustic responses are characterised by examining the contribution by the circumferential modes. It is shown that equally spaced internal bulkheads generate a periodic structure thus creating a grouping effect for the higher circumferential modes, but do not have strong influence on the sound radiation. Stiffeners are found to have an important effect on both the dynamic and acoustic responses of the hull. The contribution of the conical end closures on the radiated sound pressure for the lowest circumferential mode numbers is also clearly observed. This work shows the importance of the bending modes when evaluating the sound pressure radiated by a submarine under harmonic excitation from the propulsion system.

Excitation of the low frequency vibrational modes of a submerged vessel can generate significant radiated noise levels. Vibrational modes of a submarine hull are excited from the transmission of fluctuating forces through the shaft and thrust bearings due to the propeller rotating in an unsteady fluid. The focus of this work is to investigate the structural and acoustic responses of a submarine hull under axial excitation. The submarine hull is modelled as a cylindrical shell with internal bulkheads and ring stiffeners. The cylindrical shell is closed by truncated conical shells, which in turn are closed at each end using circular plates. The entire structure is submerged in a heavy fluid medium. The structural responses of the submerged vessel are calculated by solving the cylindrical shell equations of motion using a wave approach and the conical shell equations with a power series solution. The displacement normal to the surface of the structure in contact with the fluid medium was calculated by assembling the boundary/continuity matrix. The far field radiated sound pressure was then calculated by means of the Helmholtz integral. Results from the analytical model are compared with computational results from a fully coupled finite element/boundary element model. The individual and combined effects of the various influencing factors, corresponding to the ring stiffeners, bulkheads, conical end closures and fluid loading, on the structural and acoustic responses are characterised by examining the contribution by the circumferential modes. It is shown that equally spaced internal bulkheads generate a periodic structure thus creating a grouping effect for the higher circumferential modes, but do not have strong influence on the sound radiation. Stiffeners are found to have an important effect on both the dynamic and acoustic responses of the hull. The contribution of the conical end closures on the radiated sound pressure for the lowest circumferential mode numbers is also clearly observed. This work shows the importance of the bending modes when evaluating the sound pressure radiated by a submarine under harmonic excitation from the propulsion system.

Atualmente é bem conhecido que o uso de dispositivos passivos de dissipação de energia, tais como amortecedores por atrito, reduzem consideravelmente a resposta dinâmica de estruturas. Entretanto, os melhores parâmetros de cada amortecedor e também a melhor posição para instalá-los dentro da estrutura permanecem difíceis de serem estabelecidas. Assim, a otimização de amortecedores é uma área que vem sendo estudada de forma crescente nos últimos anos, tendo grande impacto no projeto ótimo de dispositivos para o controle de vibrações de estruturas, possibilitando obter soluções seguras e ao mesmo tempo econômicas. Contudo, apesar dos amortecedores de vibração por atrito possuírem algumas vantagens em relação a outros dispositivos passivos, poucos trabalhos são encontrados sobre a otimização de seus parâmetros ou sobre a sua melhor posição dentro de uma estrutura, devido à maior dificuldade de se calcular sistemas que envolvem atrito, por este ser não-linear. Entretanto, é interessante se levar em conta as incertezas presentes nas propriedades estruturais e/ou na excitação dinâmica no processo de otimização, o que leva a um problema de otimização sob incerteza, como otimização robusta e otimização baseada em confiabilidade. Assim, nesta Tese é proposta uma metodologia para a otimização simultânea dos parâmetros e das posições de amortecedores de vibração por atrito a serem instalados em edifícios submetidos à excitação sísmica levando em conta as incertezas presentes tanto nas propriedades estruturais quanto no carregamento sísmico, assim como nas forças de atrito dos amortecedores. A fim de ilustrar a metodologia, dois exemplos de aplicação são apresentados, sendo o primeiro sobre otimização robusta e o segundo sobre otimização baseada em confiabilidade. Os resultados mostraram, em ambos os exemplos, que o método proposto obteve sucesso, melhorando consideravelmente o comportamento dinâmico dos edifícios estudados, mesmo para um número limitado de dispositivos instalados. Portanto, acredita-se que a metodologia de otimização desenvolvida constitui uma ferramenta eficaz para o projeto ótimo de amortecedores por atrito. / Nowadays it is well known that the use of passive energy dissipation devices, such as friction dampers, considerably reduces the dynamic response of structures. However, the best parameters of each damper and also the best position to install them within the structure remain difficult to be determined. Thus, optimization of dampers is an area that has been increasingly studied in recent years, having a big impact in the optimal design of devices for the vibration control of structures, allowing to obtain safe and at the same time economic solutions. However, although friction dampers have some advantages over other passive devices, few contributions are found on optimization of their parameters or on their optimal position within a structure. This fact can be explained due to the greater difficulty in determining the response of systems involving friction, because their nonlinear behavior. In addition to the lack of studies on optimization of friction dampers, the few studies found in the literature consider the problem in a deterministic way. However, the uncertainties present in the structural properties and/or in the dynamic excitation can alter the optimal solution. Thus, it is important to take into account these uncertainties in the optimization process, which leads to an optimization problem under uncertainty, such as robust optimization and reliability-based optimization. Thus, in this Thesis, a methodology is proposed for the simultaneous optimization of parameters and positions of friction dampers to be installed in buildings subjected to seismic excitation taking into account uncertainties present in both the structural properties and the seismic load, as well as in the friction forces of the dampers. In order to illustrate the approach, two examples are presented, the first one on robust optimization and the second on reliabilitybased optimization. The results show, in both examples, that the proposed method considerably improves the dynamic behavior of the studied buildings, even for a limited number of installed devices. Therefore, it was shown that the proposed procedure is an effective tool for the optimum design of friction dampers.

Este trabalho tem como objetivos avaliar os níveis vibratórios a que os passageiros de ônibus rodoviários intermunicipais estão submetidos e realizar uma mudança projetual na carroceria/poltrona que atenue tais efeitos. A redução desses níveis é uma necessidade, porque os passageiros que utilizam ônibus como meio de transporte em viagens de longa distância podem ficar expostos a efeitos vibratórios que o chassi transmite para a carroceria, e também à vibração decorrente dos efeitos externos, que são gerados quando o ônibus transita em estradas. Esses efeitos podem gerar também riscos de quebra dos componentes estruturais da carroceria. Neste estudo foram realizadas medições das acelerações produzidas na direção vertical de acordo com a Norma ISO 2631, confrontadas com as curvas-limite de conforto, saúde e fadiga estabelecidas nesta norma. Há uma necessidade de se quantificar o nível de vibração a que o passageiro de ônibus está submetido estando sentado na poltrona e de quantificar quanto tempo ele pode utilizar o transporte sem que haja riscos à sua saúde. Também é necessário o conhecimento do comportamento da carroceria em relação aos efeitos vibratórios para dimensionar os componentes da estrutura de modo que resistam a esses efeitos. Para a modificação projetual foi desenvolvida uma metodologia de análise dinâmica, por meio do modelo numérico da carroceria, poltrona e chassi, aplicando ao modelo numérico a rugosidade de pavimentos asfálticos medidas experimentalmente, permitindo visualizar numericamente os efeitos vibratórios na estrutura da poltrona e, por consequência, gerar uma mudança projetual amenizando tais efeitos. / The purpose of this work is to evaluate the vibratory levels the ones that the passengers of inter-municipal road buses are submitted; and fulfill a changing project in body/seat that attenuates such effect. The reduction of these levels is a necessity, because the passengers who use buses as half of transport in trips of long distance can be exposed to the vibratory effect that the chassis transmits to the body, and also the consequential vibration of the external effect, which is generated when the bus transits on roads. These effects can also generate risks of the structural components braking of the body. In this study measurements of the accelerations produced in the vertical direction were fulfilled in accordance with Norma ISO 2631, collated with the curve-limit of comfort, established health and fatigue in this norm. There is a necessity to quantify the vibration level that the bus passenger is submitted being seated in the armchair and to quantify how long it can use the transport without risks to its health. It is also necessary the body's behavior knowledge related to the vibratory effect to measure the structure components in a way they can resist to these effects. For the project modification it was developed a methodology of dynamic analysis, through the numerical model of the body, armchair and chassis experimentally applied to the numerical model, the rugosity of measured asphalt floors, allowing visualizing numerically the vibratory effect in the structure of the armchair and, consequently, to generate a changing project tempering such effect.

Desmonte de rochas com explosivos em áreas próximas a residenciais têm ocorrido com frequência em várias localidades em todo o Brasil. Atividades relacionadas a mineração e em especial as detonações causam muitos problemas visto que geram incômodo às comunidades vizinhas resultante de níveis elevados de pressão acústica (ruído) na atmosfera e reclamações de rachaduras em paredes das residências associadas com a propagação de vibrações no terreno. A necessidade de se obter uma melhor compreensão de como estruturas típicas da construção civil nacional respondem as vibrações geradas pelas detonações se torna evidente, bem como uma avaliação conjunta da influência de outras forças, tais como, condições meteorológicas (variações diárias de temperatura e umidade relativa do ar) que começam a agir sobre os materiais constituintes das estruturas desde o momento da construção e durante toda sua vida útil. Nesse contexto, definiu-se como meta dessa pesquisa investigar a resposta deformacional de construções de alvenaria frente aos estímulos provocados por diferentes níveis de vibração e pressão acústica gerados pelo desmonte de rochas com explosivos em diferentes condições geológicas, comparando-as com os efeitos das variações climáticas de temperatura e umidade. Visando o atendimento desta demanda, a resposta de três estruturas, duas residenciais e uma comercial, a diferentes operações com desmonte de rochas (mineração de carvão e pedreira) foram avaliadas. A movimentação das paredes de estruturas de alvenaria, comumente encontradas no entorno de empreendimentos mineiros, foi registrada com sensores de velocidade instalados nas paredes e os resultados foram correlacionados com os níveis de vibração no terreno e pressão acústica (ruído) na atmosfera que provocaram esta movimentação. A partir dos resultados das medições da movimentação das estruturas, deformações induzidas nas paredes, geradas durante trações no plano e flexões fora do plano das paredes, foram computadas e comparadas com os limites de ruptura do material mais fraco que constitui as paredes das estruturas. Em conjunto com o monitoramento da movimentação das estruturas, variações na abertura de rachaduras existentes no reboco no interior ou exterior das estruturas induzidas por forças dinâmicas (detonações) e estática (variações climáticas) foram registradas por meio de sensores de deslocamento instalados em ambos lados das rachaduras. As respostas das estruturas apresentaram excelente acoplamento da fundação com o terreno e nenhuma movimentação livre (ressonância) das paredes das estruturas foi observada após a passagem das ondas sísmicas, indicando que as estruturas seguem muito perto as excitações provocadas pelas vibrações no terreno do terreno e param de movimentar junto com o mesmo. Devido às ondas sísmicas e acústicas atingirem quase que ao mesmo tempo as estruturas, foi difícil separar a influência de cada estímulo. As deformações calculadas foram inferiores as necessárias para induzir rachaduras na argamassa utilizada como reboco nas paredes, considerada como o material mais frágil dentre os constituintes das paredes das estruturas. A resposta deformacional das rachaduras frente às variações climáticas diárias de temperatura e humidade relativa do ar foi superior as variações resultantes da influência das vibrações geradas pelas detonações. / Blasting near residential areas has become frequent in many locations throughout Brazil. Activities related to mining and in especial blasting have become a problem as they generate a potential nuisance to nearby communities resulting from high air sound pressure levels and can result in claims of wall cracking associated with ground vibrations. It was deemed necessary to have a better understanding of how structures of typical national construction respond to blast vibrations and compare this response to other forces, such as, environmental forces that naturally act on these structures since the moment they are constructed and throughout the entire life of the structure. The response of three structures, two residential and one office building, to different blasting activities (coal and quarry blasting) were evaluated in this study. Whole structure motions and the movement of existing cracks were measured in masonry built structures commonly found near mining operations. Whole structure and mid-wall motions were measured at upper and lower corners and on mid-walls using single-axis velocity transducers and compared with ground motions and air sound pressure excitations, measured next to the structures using a tri-axial geophone and microphone. Dynamic (blast-induced) and static (weather-induced) changes in crack width of existing interior and exterior wall cracks in the cement grout, typically used as wall coverage, were recorded. Dynamic structure and crack motions during blasting were time-correlated with ground vibrations and air sound pressure levels. Wall strains generated during out-of plane bending and in-plane tensile strains were computed and compared with the failure strains for the weakest material comprising the wall construction. Long-term crack movement with variations in temperature and humidity were compared with blast-induce peak crack displacements. The structures response showed good coupling of the foundations with the ground and no free-response was observed after the cessations of the ground excitations, indicating the structures are rigid following very close the ground excitation. Because air sound pressure levels and ground motions arrived at the same time in the structures, it was difficult to separate the influence of each stimulus. Calculated strains were lower than the required to induce cracks in the cement grout and environmental-induced crack response, resultant from daily changes in temperature and humidity, were greater than the response caused by blast-induced ground motions and air sound pressure levels in crack aperture.