Le verre feuilleté est constitué de deux ou plusieurs feuilles de verre assemblées par une ou plusieurs couches de polymères viscoélastiques intermédiaires qui sont à l’origine des interactions entre les mécanismes de cisaillement, de flexion locale et de flexion globale qui régissent le comportement d’ensemble du verre feuilleté. Dans ces travaux, nous proposons un modèle de plaques dites "fortement contrastées" intégrant ces différents mécanismes et leur couplage. Dès lors qu’il existe une séparation d’échelle entre l’épaisseur de la plaque et la taille caractéristique des variations des champs cinématiques, la méthode des développements asymptotiques est applicable pour l’étude des stratifiées. Le comportement effectif de la plaque est dérivé de la loi de comportement 3D des matériaux, associée à une formulation de développements asymptotiques et à une mise à l’échelle appropriée du contraste de rigidité entre les couches raides de verre et des couches souples de polymère viscoélastique. Le procédé fournit une formulation explicite et cohérente, intégrant les efforts duaux des descripteurs macroscopiques (équations constitutives), les équations d’équilibres hors-plan et dans le plan et les différentes lois de comportements du stratifié. Le modèle est d’abord construit dans le cas d’une plaque de verre feuilleté à 2 couches raides puis différents cas de chargements statiques et dynamiques sont appliqués. Il est ensuite étendu aux plaques à 3 couches raides puis généralisé aux plaques à N couches raides. Des campagnes expérimentales sont mises en place pour valider les modèles obtenus. Enfin un cas d’étude de dimensionnement de plancher en verre feuilleté est proposé. / Widely used in recent years, the glass material makes it possible to erect light, aesthetic and resistant structures, in particular with glass lamination method, which consists in assembling two or more sheets of glass by one or more intermediate viscoelastic polymers layer. These viscoelastic interface layers are the source of interactions between the shear, the local bending and the global bending mechanisms that govern the overall behavior of laminated glass. For an optimal dimensioning and an accurate determination of the different fields, we propose a "highlycontrasted" plates model encapsulating these different mechanisms and their coupling. As long as a scale separation between the plate thickness and the caracteristic size of kinematics field variations exists, the asymptotic expansion method can be applied for the study of laminates. The effective plate behaviour is derived from the 3D constitutive law of the materials combined with an asymptotic expansion formulation and an appropriate scaling the tiffness contrast between stiff glass layers and soft viscoelastic polymer layers. The method provides a synthetic and consistent formulation, integrating the dual efforts of the macroscopic descriptors, in-plane and out-of-plane balance equations and the constitutive laws of the laminate. First the model is developped for a 2 stiff layers laminated glass plates, then different static and dynamic loading cases are applied. It is then extended to plates with 3 stiff layers and then generalized to plates with N stiff layers. Experimental campaigns are set up in order to validate the models. Finally, a case study of laminated glass floor design is proposed.

Orientador: Janito Vaqueiro Ferreira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica / Made available in DSpace on 2018-08-04T09:11:42Z (GMT). No. of bitstreams: 1 Mariano_SilvioLuiz_M.pdf: 10538477 bytes, checksum: b5e594a3783a5571c8face1a74dae202 (MD5) Previous issue date: 2005 / Resumo: Este trabalho apresenta a análise numérica e experimental do índice de vibro-impacto em alavancas de transmissão mecânica. Foram desenvolvidos modelos de alavanca que consideram não-linearidades na estrutura. Métodos para quantificação do vibro-impacto foram obtidos na literatura e implementados para o levantamento de curvas, as quais indicam a variação do índice de Vibro-impacto com relação à variação dos parâmetros dos modelos desenvolvidos. A técnica da Transformada de Hilbert também foi implementada para levantamento das forças não-lineares atuantes nos modelos. Foram utilizadas três bancadas para identificação das forças não-lineares atuantes e validação da técnica salientada, que utiliza sinais de força, deslocamento, velocidade e aceleração. As curvas de rigidez não-Hnear foram identificadas coerentemente, as quais tiveram validação pelo levantamento da rigidez das mesmas bancadas por medições estáticas. Dois modelos numéricos de alavanca, utilizando massas concentradas, foram estudados. Nestes identificaram-se curvas de força não-Hnear e levantaram-se curvas de sensibilidade do índice de Vibro-impacto à variação dos parâmetros dos modelos. Mostrou-se que a técnica da Transformada de Hilbert pode ser utilizada para a identificação de sistemas não-lineares e que o estudo de sensibilidade em modelos de vibro-impacto pode ser obtido sem muita dificuldade / Abstract: This work presents a study about a numerical and experimental vibro-impact level analisys in mechanical gearshift levers. It was developed gearshift lever models which consider nonlinearities in the structure. Methods to vibro-impact quantification were obtained in the available literature and were implemented to obtain curves which show the vibro-impact level change with the modification of the parameters of the developed models. Hubert Transform techniques were also implemented to obtain nonlinear forces implemented on the models. To verify the efficiency of these techniques, three test rigs with nonlinearities were developed and the nonlinear forces were identified. The techniques need the displacement, velocity and acceleration signals to calculate the forces. The nonlinear forces curves were identified and validated with the static forces measured. Two models of gearshift levers were developed, using lumped masses. In these models the nonlinear forces curves and the sensibility to the vibro-impact level with modifications in the model parameters were obtained. It was showed that the Hubert Transform techniques are reliable to identify nonlinear systems and that the sensibility study in vibro-impact can be obtained easily / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

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L’hydrogène liquide est un ergol utilisé en complément de l’oxygène liquide pour la propulsion de nombreux lanceurs en particulier ceux de la famille Ariane. Cependant, sa dangerosité interdit la réalisation d’essais, en particulier vibratoires, sur des réservoirs remplis. Cette thèse explore une piste d’étude permettant de réaliser ces essais vibratoires sur le réservoir rempli d’un matériau de substitution : un ensemble de billes pré-contraintes. L’objectif est d’obtenir un comportement modal similaire en termes de modes et de fréquences propres à celui du réservoir rempli d’hydrogène liquide pour l’étude des premiers modes. Pour répondre à cet objectif, cette étude est développée en deux parties. Dans la première partie, une approche analytique basée sur une méthode par équivalences fréquentielles est détaillée. Après avoir présenté les grandes lignes de la méthodologie utilisée et l’ensemble des modèles développés, la méthodologie est appliquée au cas étudié expérimentalement de manière à mettre en évidence l’influence des différents paramètres et de proposer une première méthode pour choisir un jeu de billes adapté. La seconde partie, traite principalement des aspects expérimentaux et numériques. Après avoir détaillé la caractérisation des billes utilisées, le montage expérimental conçu et réalisé pour effectuer des essais vibratoires sur un réservoir rempli de billes pré-contraintes est présenté. Les différents résultats obtenus avec ce montage sont étudiés au regard de l’approche analytique, mais aussi de modèles numériques utilisant des éléments-discrets et des éléments-finis. / Liquid hydrogen is a propellant alternatively used with liquid oxygen for the propulsion of many launchers, especially those of the Ariane family. However, its dangerousness prohibits vibration tests on filled tank. The aim of this PHD is to explore the possibility to carry out such vibration tests by filling these tanks with a substitute material : a set of pre-stressed balls. As further argued and developed in the report, the objective is to obtain a modal behavior similar in term of mode shapes and natural frequencies to those of the tank filled with liquid hydrogen for the first modes. In the first part, an analytical approach based on a method using frequency equivalences is detailed. After presenting the outlines of the methodology used and all the models developed, the methodology is applied to the experimentally studied case in order to highlight the influence of the different parameters as well as then to propose a first method to choose a set of well adapted balls. The second part deals mainly with experimental and numerical aspects. Firstly, the balls used in the thesis are characterized. Then, the experimental set-up designed and realized to carry out vibration tests on a tank filled with pre-stressed balls is presented. The different results obtained are compared with both analytical results and numerical based on discrete-elements and finite-elements results.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This work presents the development of a novel digital acceleration controller for sinusoidal vibration tests using switching-mode AC power source (ACPS) fed electrodynamic vibration machines. The proposed scheme is based on the interaction of two control loops: one for the shaker's acceleration regulation and another for the ACPS output voltage control. A robust model reference adaptive algorithm (RMRAC) is used in the voltage control loop. To reduce the effects caused by the plant's parameters variations as well harmonic vibrations and resonances of the test specimen, the acceleration feedback controller is augmented with a feedforward and a robust controller. Experimental results show that the proposed system is capable to achieve excellent acceleration reference tracking performance and robustness in the closed loop control from 20 Hz to 200 Hz. Investigations shall be performed to evaluate the response of this scheme when controlling vibrations as fast as 2000 Hz. A specific instrumentation system has been developed to feedback the electrodynamic vibration machine's acceleration. The proposed solution employs piezoelectric accelerometers, voltage mode preamplifiers, circuit for signal conditioning, analog to digital conversion and filtering. A study concerning the commonly used vibration measurement techniques and the design procedure, simulation, implementation and experimental results are described in detail. / Esse trabalho apresenta o desenvolvimento de um novo tipo de controlador digital de aceleração para ensaios com vibrações senoidais em máquinas de vibra ção eletrodinâmicas supridas por fontes de potência CA com comutação. O esquema proposto é baseado na interação entre duas malhas de controle: uma para regulação de aceleração da máquina de vibração e outra para ajuste da tensão de saída da fonte de potência CA. Um algoritmo adaptativo robusto por modelo de referência (RMRAC) é utilizado na malha de controle de tensão. Os efeitos de variações paramétricas existentes na planta bem como de vibrações harmônicas e ressonâncias do objeto ensaiado são minimizados com o uso de um controlador feedforward e um controlador feedforward robusto na malha de aceleração. Resultados experimentais demonstram que o sistema proposto é capaz de garantir excelente rastreamento da aceleração de referência e robustez em malha fechada entre 20 Hz e 200 Hz, necessitando ainda de investigação para controle de vibrações tão rápidas quanto 2000 Hz. A realimentação da aceleração da máquina é realizada com o desenvolvimento de uma instrumentação adequada a esse fim. A solução proposta utiliza acelerômetros piezoelétricos, pré-amplificadores modo tensão, circuito para condicionamento de sinais, conversão analógico-digital e filtragem. Um estudo sobre as principais técnicas utilizadas em medições de vibrações bem como a metodologia de projeto, simulação, implementação e testes experimentais são descritos detalhadamente.