Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-10-18T20:27:50Z No. of bitstreams: 1 JosianeMariaDeMacedoFernandes_TESE.pdf: 1245335 bytes, checksum: 5135bc4fc7856839af432f3c4f427beb (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-10-23T22:17:47Z (GMT) No. of bitstreams: 1 JosianeMariaDeMacedoFernandes_TESE.pdf: 1245335 bytes, checksum: 5135bc4fc7856839af432f3c4f427beb (MD5) / Made available in DSpace on 2017-10-23T22:17:47Z (GMT). No. of bitstreams: 1 JosianeMariaDeMacedoFernandes_TESE.pdf: 1245335 bytes, checksum: 5135bc4fc7856839af432f3c4f427beb (MD5) Previous issue date: 2017-06-28 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Neste trabalho ? desenvolvida uma estrat?gia de controle n?o linear baseada no controle por modos deslizantes com compensa??o neural para estabiliza??o de sistemas subatuados sujeitos a vibra??es torcionais. No intuito de analisar o desempenho da abordagem proposta, a lei de controle foi implementada em uma coluna de perfura??o. As colunas de perfura??o s?o discretizadas em n partes. A atua??o ? dada no top drive, ou na mesa rotativa na extremidade superior da coluna, e todo o restante da coluna n?o recebe atua??o. As vibra??es torcionais abordadas neste trabalho s?o do tipo stick-slip, que ? o caso mais cr?tico desse tipo de vibra??o, cuja n?o linearidade ? geralmente causada pelo atrito entre a coluna e a forma??o, podendo ocorrer em qualquer ponto ao longo da coluna e deve ser levado em considera??o na modelagem. O controle por modos deslizantes apresenta robustez frente a incertezas param?tricas e perturba??es. A estrat?gia adotada n?o requer o conhecimento pr?vio de incertezas e n?o linearidades do sistema. No entanto, a fun??o descont?nua utilizada na lei de controle pode gerar o fen?meno de chattering, que em atuadores mec?nicos ? indesej?vel. Para atenuar o chattering, uma fun??o suave ? utilizada no lugar da descont?nua, sendo essa abordagem ocasionadora de diminui??o no desempenho do controlador. Nesse ponto, t?cnicas de intelig?ncia artificial podem contribuir na lei de controle para devolver o desempenho ou parte dele ao sistema. Duas arquiteturas de rede s?o empregadas para estimar a compensa??o, uma rede do tipo perceptron de m?ltiplas camadas e uma rede de fun??es de base radial. As superf?cies de controle s?o definidas como uma combina??o linear dos erros dos estados do sistema e uma rede neural ? adicionada para compensar a forma??o de ciclos limites, comumente apresentados ap?s a perda de efic?cia. Resultados s?o apresentados para demonstrar a performance do sistema de controle proposto. / In the present work, a nonlinear control strategy based on sliding mode method and artificial neural networks is presented. This approach can be applied to stabilize nonlinear under actuated systems subjected to torsional vibrations. In order to evaluate the proposed approach, the control law was implemented in a drill string. Drill strings are addressed due to their nonlinear and underactuated dynamics. The drill strings are discretized in n parts. The control output is given at the top drive whereas the other string parts are not directly actuated. Torsional vibrations employed in this work are stick-slip, which is the more critic way of torsional vibrations. Stick-slip is a nonlinearity usually caused by friction between the drill string and rock formations and can occurs at any point along its length. Sliding mode control is a very robust technique even with parametric uncertainties and external perturbations. There is no need of previous knowledge of uncertainties and nonlinearities. The discontinuous function adopted at the control law can lead to the undesired chattering effect. The discontinuous function can be replaced by a smooth function to avoid chattering, but this also implies on decrement of the system performance. In order to attenuate this effect, a compensation is added to the control law. Two different artificial neural network architectures are investigated: multilayer perceptrons and radial basis functions. The sliding surfaces are defined as a linear combination of tracking errors. The neural network is employed to mitigate the generated limit cycle. Numerical results are presented in order to demonstrate the performance of the control system.

A falta de controle e planejamento dos espaços públicos, entre eles, as calçadas, gera problemas como a falta de segurança e de acesso aos equipamentos urbanos e até impede a livre circulação das pessoas. As calçadas são uma pequena, mas importante parte da complexa infraestrutura urbana. O provimento de calçadas adequadas é um meio de incentivo ao deslocamento a pé e ao uso de transporte coletivo. A calçada não deveria oferecer nenhum risco aos pedestres, porém, grande parte das calçadas existentes no Brasil é imprópria para a circulação, seja pela existência de obstáculos, seja pela precariedade ou inadequação dos materiais utilizados em sua construção. Essa falta de qualidade das calçadas é a causa de muitos acidentes. Os pedestres em geral e, além dos idosos, principalmente as crianças e as pessoas portadoras de necessidades especiais, podem ser considerados usuários vulneráveis. No presente trabalho, as exigências dos usuários, no que se refere à segurança em uso, de acordo com a abordagem de desempenho, foram identificadas como sendo segurança ao risco de quedas, segurança ao risco de atropelamentos, segurança ao risco de lesões por choque e acessibilidade. As exigências dos usuários foram traduzidas em requisitos de desempenho a serem cumpridos em calçadas seguras e, após, foram identificados os respectivos critérios, níveis de atendimento e métodos de avaliação, com base na legislação e bibliografia. Com isso, foi elaborado um instrumento de avaliação de segurança em calçadas. Um estudo de caso em um trecho da Av. Independência, em Porto Alegre, foi realizado para testar o instrumento elaborado, com aplicação experimental em 17 calçadas. O instrumento mostrou-se eficiente na aquisição, processamento e registro de dados. Para a validação definitiva do instrumento, é necessário que se amplie os testes. Além disso, foi realizada pesquisa exploratória com aplicação do ensaio com o Pêndulo Britânico, para avaliação da resistência ao escorregamento. Todas as calçadas foram aprovadas quanto a este critério. O método de avaliação se mostrou adequado, porém limitado a calçadas com pequena inclinação. Adicionalmente, as diversas falhas relativas à segurança encontradas nas calçadas avaliadas foram analisadas. Nenhuma calçada do estudo de caso foi aprovada e considerada segura. A calçada com pior desempenho atendeu a apenas 38,88% dos critérios. Já o melhor resultado foi de uma calçada com taxa de atendimento aos critérios de 68,42%. Os critérios menos atendidos foram o desnível em relação à via, o rebaixo para acesso de veículos adequado, rampa nos pontos de travessia e a sinalização tátil no piso. Diante da grande quantidade de falhas encontradas no estudo de caso, aponta-se a ausência de um técnico no processo de construção de uma calçada, como uma das principais causas das não conformidades, junto à falta de um documento, preferencialmente uma Norma Técnica, que reúna as informações necessárias para o projeto de calçadas. Desta forma, este trabalho visa contribuir para o tema desempenho de calçadas, com foco nos requisitos relativos à segurança dos usuários. / The absence of control and planning of public spaces, including sidewalks, creates problems such as lack of security and access to urban equipment and even prevents the free movement of people. The sidewalks are a small but important part of the complex urban infrastructure. Providing adequate sidewalks is a means of encouraging walking and the use of public transport. The sidewalk should not pose any risk to pedestrians, but most of the existing sidewalks in Brazil are unfit for circulation, either by the existence of obstacles, or by the precariousness or inadequacy of the materials used in their construction. This lack of quality in sidewalks is the cause of many accidents. Pedestrians in general and, in addition to the elderly, especially children and people with special needs, can be considered vulnerable users. In this work, users' requirements regarding safety in use, according to the performance approach, have been identified as safety for the risk of falls, safety for the risk of pedestrian crashes, safety for the risk of shock injuries and accessibility. The users’ requirements were translated into performance requirements to be met on safe sidewalks and, afterwards, the respective criteria, suitable levels and evaluation methods were identified, based on legislation and bibliography. And therewith, a safety assessment instrument for sidewalks was developed. A case study on an excerpt from Av. Independência, in Porto Alegre, was carried out to test the instrument, with experimental application on 17 sidewalks. The instrument was efficient in data acquisition, processing and recording. For definitive validation of the instrument, it is necessary to expand the tests. In addition, an exploratory study was carried out with the application of the British Pendulum test to evaluate the slip resistance. All sidewalks were approved for this criterion. The method of evaluation was adequate, but limited to sidewalks with a small slope. In addition, the various safety flaws found on the evaluated sidewalks were analyzed. No sidewalk from the case study was approved and considered safe. The sidewalk with the poorest performance met only 38.88% of the criteria. The best result was a sidewalk with a rate of meeting the criteria of 68.42%. The least attended criteria were the height in relation to the roadway, adequate vehicle access ramp, ramp at crossing points and tactile signage on the ground. Considering the large number of flaws found in the case study, it is pointed out that the absence of a technician in the process of building a sidewalk is one of the main causes of nonconformities, due to the lack of a document, preferably a Technical Standard, that gathers the necessary information for sidewalk projects. Thus, this work aims to contribute to the theme of performance of sidewalks, focusing on requirements regarding user safety.

Southern Vancouver Island lies on the forearc of the Cascadia subduction zone, north of a concave bend in the plate boundary centred around the Olympic Mountains. The bend in the margin coincides with a significant decrease in northward-directed trench-parallel forearc migration, and a network of active crustal faults in the Puget Lowland east of the Olympic Mountains accommodates permanent north-south shortening and transpression. The nature of forearc deformation on southern Vancouver Island is less well constrained, due in part to the unknown extent and kinematics of active crustal faulting. Recent work has shown that a brittle fault zone associated with the Eocene terrane-bounding Leech River fault has produced at least two surface-rupturing earthquakes in the late Quaternary. I use LiDAR-derived topographic data, slip-sense indicator analysis of slickenlines on fault planes, electrical resistivity tomography (ERT), and ground-penetrating radar (GPR) to investigate the geometry, kinematics, and Quaternary activity along the eastern half of the active, brittle Leech River fault zone. My mapping reveals a complex, near-vertical zone up to 1 km wide and 25 km long that exhibits many characteristics of a strike-slip fault. Displaced Quaternary deposits are observed directly at two sites in the western 8 km of the study area, and inferred through geophysical imagery, topographic data, and liquefaction features to extend to the eastern terrestrial extent of the fault zone towards previously mapped active faults in the Juan de Fuca Strait and the Darrington-Devil’s Mountain fault zone in western Washington. I use fault kinematics and geometry to show that the eastern Leech River fault zone has been reactivated as a right-lateral strike-slip fault that accommodates forearc deformation within the modern stress field north of the Olympic Mountains. / Graduate / 2018-12-01

Neste trabalho apresenta-se um modelo numérico para a análise de problemas tridimensionais envolvendo a interação mecânica estaca-solo, acoplando-se o Método dos Elementos de Contorno (MEC) ao Método dos Elementos Finitos (MEF). O solo é modelado com o MEC utilizando-se as soluções fundamentais de Mindlin, assumindo um meio semi-infinito, homogêneo, isotrópico e elástico-linear. As estacas, modeladas com o MEF, consistem em um elemento único, com quatro nós e 14 parâmetros nodais (três deslocamentos em cada nó e mais duas rotações no topo da estaca). Cada uma das estacas é levada em consideração no MEC como uma linha de carga. Considera-se o escorregamento das estacas em relação ao maciço, empregando modelos de aderência para a definição da evolução das tensões tangenciais ao longo do comprimento das estacas. São empregados, como funções de forma, polinômios do quarto grau para os deslocamentos horizontais, cúbicos para os deslocamentos verticais e tensões horizontais ao longo do fuste e quadráticos para as tensões verticais do fuste e escorregamento. A reação da ponta da estaca é calculada assumindo tensão constante na base. / This work presents a method for tri-dimensional pile-soil interaction problems, by coupling the Boundary Element Method (BEM) to the Finite Element Method (FEM). The soil is modeled with BEM, using the Mindlins fundamental solutions, supposing a semi-infinite, homogeneous, isotropic, elastic and linear space. Piles are modeled with FEM and are represented by one element with four nodes and 14 nodal parameters (three displacements in each node and two rotations at the top node). Each pile is represented in BEM as a line load. The pile slip is considered using adherence models to evaluate the evolution of shaft tractions. There are employed fourth grade polynomial shape functions for horizontal displacements, cubic polynomial functions for vertical displacements and horizontal tractions along shaft and quadratic polynomial functions for vertical tractions and slip. Tip reaction is calculated supposing constant traction at the base.

O presente trabalho propõe o entendimento do comportamento no estado fresco de argamassas colantes, com base na caracterização reológica e físico-química de diferentes composições comerciais, servindo de base para analisar o fenômeno de deslizamento, a partir do ensaio estabelecido na norma brasileira. Para isso, foi utilizado o ensaio “Squeeze flow” (escoamento por compressão axial), empregado na caracterização de argamassas de revestimento no laboratório de microestrutura do CPqDCC da EPUSP, como ferramenta de análise do comportamento de argamassas colantes. Neste ensaio, o escoamento do material decorre da aplicação de uma carga de compressão sobre a amostra no estado fresco, a qual ocasiona deslocamentos no seu interior devido a esforços de cisalhamento radiais originados durante o fluxo. O critério de seleção das argamassas colantes comerciais (tipo AC-I) se baseou nos resultados do ensaio de deslizamento, escolhendo-se duas com resultado muito abaixo do limite especificado, duas com resultado próximo do limite e outras duas com resultado acima do mesmo. A composição química e física foi caracterizada com o objetivo de embasar a análise dos resultados obtidos no “Squeeze flow”. A separação da fração fina das argamassas na peneira no.200 contribuiu para o conhecimento da viscosidade da pasta e da sua influência no comportamento reológico das argamassas. Foi observado que as argamassas estudadas apresentam diferenças de composição físico-química e de comportamento reológico. As diferenças de comportamento reológico das argamassas decorrem, provavelmente, de ação sinérgica de alguns parâmetros da composição, com destaque para a distribuição granulométrica. O “Squeeze flow” mostrou-se uma ferramenta adequada na caracterização das argamassas colantes e contribuiu para explicar o deslizamento estabelecido na norma brasileira, pela proposição de modelos hipotéticos de comportamento. / Present thesis proposes the study of plastic-state behaviour of dry-set mortars based on the rheological and physicochemical characterization of different commercially available dry-set mortar compositions. Such characterization served as basis for the analysis of dry-set mortar slip phenomena using the tests recommended by brazilian standards (NBR). The Squeeze Flow test (slip by axial compression) originally used for coating mortars characterization by the EPUSP CPqDDC Microstructure Laboratory was adopted as a test tool for analysing the dry-set mortar behaviour. In the mentioned test the material slip is obtained by compressing the sample in its plastic state which caused internal displacements due to radial shearing tensions originated during the mentioned slip. The dry-se mortars (all of them AC-I type) used in the study were selected based in the slip tests results against brazilian standards specified limits resulting in the selection of two dry-set mortars below the specified limit, two dry-set mortars close to the specified limit and dry-set mortars above the specified limit. Chemical and physical compositions were characterized in order to serve as basis for Squeeze Flow results analysis. Fine fraction segregation, using number 200 sieve contributed to understanding of plastic-state mortar viscosity and its influence in mortar rheological behaviour. It was observed diverse physicochemical and rheological behaviour among the studied dry-set mortars. The rheological behaviour diversity of dry-set mortars were due to the synergy among some composition parameters, specially the granular distribution. The Squeeze Flow was considered a suitable tool for the characterization of dry-set mortars and contributed to develop hypotetical behaviour models that allowed to explain the slip as stated by brazilian standards.

Par rapport à un fluide Newtonien, les suspensions denses de particules présentent des propriétés rhéologiques différentes. Des comportements rhéofluidifiants ou rhéoépaississants liés à des phénomènes de migration de particules peuvent apparaitre. Pour des suspensions, le taux de cisaillement, la concentration et la taille des particules ont une grande influence sur ce comportement rhéologique (Denn et Morris 2014). Pour observer l'influence de ces facteurs, l'un des meilleurs moyens est de disposer d’un système simple dans lequel tous les facteurs mentionnés ci-dessus sont bien contrôlés. Ceci peut être réalisé par le développement d'une plate-forme expérimentale, sur laquelle les comportements d'écoulement de suspension (profil de vitesse et concentration locale de particules) à des vitesses de cisaillement et des concentrations de particules bien contrôlées peuvent être étudiés. Dans l'étude actuelle, 4 tâches ont été réalisées :1) Le développement d'une nouvelle formulation pour la préparation d’une suspension adaptée en indice de réfraction et en densité basée sur des particules de PMMA. 2) Le développement d'un dispositif expérimental consacré à l'étude des flux de suspension dense sous une large gamme de taux de cisaillement constant. 3) La caractérisation des profils de vitesse des flux de suspension dense sous un dispositif cône-plan utilisant des techniques de micro-PIV. 4) Une mesure préliminaire de la concentration locale de particules de la suspension sous écoulement cône-plan en utilisant des méthodes de traitement d'image. / Compared to general Newtonian fluids, highly concentrated mixtures of particles and fluid, so called dense suspensions, have different rheological properties and fluid dynamic behaviors. Such as, shear-thinning or shear-thickening effect, and apparent slip and particle migration behaviors under certain shear flow conditions. These properties are related to the application of suspension flow in real systems, for example, the blood.For suspensions, shear rate, particle concentration and particle size have a big influence of on their rheological behaviors (Denn and Morris 2014). To observe the influence of these factors, one of the best ways is to start the research from a simple case in which all the above mentioned factors are well controlled. This can be realized by developing such an experimental platform, on which the suspension flow behaviors (velocity profile and local particle concentration) at different shear rates and particle concentrations can be investigated.In the current study, 4 tasks were achieved:1) The development of a new recipe for the preparation of density and refractive index matched suspension with PMMA particles. 2) The development of an experimental set-up devoted to the investigation of dense suspension flow under a large range of constant shear rate. 3) The characterization of the velocity profiles of dense suspension flows under a cone-plate device by using micro-PIV techniques.4) A preliminary measurement of the local particle concentration of the suspension flow by using image processing techniques.

En raison du développement croissant des MEMS (Micro Electro Mechanical Systems), l'étude des écoulements de liquide ou de gaz et des transferts thermiques dans des conduites, chauffées ou non, dont le diamètre hydraulique est de l'ordre de quelques microns, a suscité un nombre considérable de travaux au cours des vingt dernières années. À cette échelle, le nombre de Knudsen peut être important (Kn>0,01), ce qui donne naissance à des phénomènes de glissement, de saut de température et de pompage thermique qui s'ajoutent aux effets de compressibilité, telles que la puissance due aux forces de pression et à la puissance des contraintes visqueuses et aux variations des propriétés du fluide avec la température. Dans les modélisations de la littérature, ces phénomènes sont rarement pris en compte simultanément et sont souvent partiellement négligés, sans justification. Notre démarche consiste à proposer une modélisation des micro-écoulements gazeux se rapprochant au mieux de la réalité en prenant en compte tous les phénomènes et à étudier les effets de chacun d'entre eux. L'étude est, en premier lieu, menée en utilisant un code commercial, résolvant les équations de conservation par la méthode des volumes finis et adapté par le biais de sous-programmes développés au cours de cette thèse. Des validations ont été effectuées pour des problèmes allant des plus simples (incompressibles, non glissants) aux plus complexes (compressibles, glissants). Cette étude a permis de mettre en évidence les problèmes liés à la modélisation quand les nombres de Péclet des écoulements sont inférieurs à l'unité (Pe < 1). Dans ce cas, les effets de diffusion inverse sont dominants et l'utilisation d'extensions à l'amont de la conduite devient incontournable. Les effets de compressibilité qui se traduisent par des détentes du gaz près de la sortie de la conduite (accélération + refroidissement) ont été analysés. Enfin, des comparaisons ont été effectuées avec des solutions analytiques d'écoulements compressibles et glissants, supposés isothermes en imposant de faibles variations de pression. Nous avons pu montrer que ces solutions restent valables, même lorsque les variations de pression sont importantes parce que les détentes ne sont localisées que près de la sortie de la conduite et n'influencent donc pas les propriétés globales de l'écoulement. La suite du travail a été réalisée à l'aide d'un code de calcul développé au laboratoire et validé pour les écoulements à grandes échelles. Des conditions aux limites de glissement ont été introduites afin de l'adapter à la problématique de ce travail de thèse. Compte-tenu de ses performances (précision et rapidité des calculs en particulier), ce code a permis de réaliser une étude paramétrique sur une large gamme de pressions d'entrée et de sortie, de telle sorte à balayer tous les types d'écoulements : de peu à très compressibles et de peu à très glissants. Les résultats sont d'abord présentés pour des écoulements quasi-isothermes puis comparés aux solutions analytiques afin de tester ces dernières sur une plus large gamme de pression. Enfin, de nouveaux résultats ont été obtenus pour des écoulements chauffés. Des corrélations, en fonction des paramètres adimensionnels caractéristiques de ces écoulements, ont été obtenues pour les modèles complets à l'aide d'un logiciel de statistiques et de plans d'expériences. Des comparaisons à des modèles simplifiés ont été effectuées pour évaluer les erreurs commises lorsque certains termes sont négligés / These phenomena are rarely taken into account all at once, at least one of them is neglected and often without justification. Our approach is to get as close as possible to reality by taking into account all the phenomena that appear at once and then to study the effect of the phenomena most often overlooked. First, the study is conducted using a commercial code for solving the conservation equations by the finite volume method. Validations were performed for problems ranging from the simplest (incompressible, non-slip flow) to the more complex (compressible, slip flow). This study highlighted the problems associated with simulations when the flows Peclet numbers are less than unity (Pe <1). In this case, the inverse diffusion effects are dominant and the use of extensions at the upstream becomes unavoidable. In addition, compressibility effects were identified; they have resulted in expansions of the gas near the exit of the pipe (acceleration + cooling). Finally, comparisons were made with analytical solutions of compressible slip flows assumed isothermal by imposing small variations of pressure. We showed that these solutions remain valid even if the pressure variations are important because the detents are located only near the exit of the pipe. In this case, they do not affect the properties of the flow. Further works were carried out using an in-house computer code, previously developed and validated in the laboratory for flows with large scales and for which slipping limits conditions have been added so that it can properly resolve slip flows. In view of its accuracy and performances in terms of CPU-time, the code allowed us to achieve a parametric study on a wide range of input and output pressures, so as to sweep all runoff from few to very compressible and few to very slip flow. The results were first presented for quasi-isothermal flow, which subsequently were compared to analytical solutions to test these ones on a wider range of pressure. Finally, the results were made for heated flows. Correlations have been obtained for a complete model using a statistical based software and design of experiments. Comparisons to simplified models were performed to assess the inaccuracies linked to the omission of terms often overlooked in the literature

L’objectif de cette thèse est d’approfondir la connaissance sur la génération et la propagation des ondes à travers l’interface de contact afin de contrôler leurs effets sur le frottement, contrôler les instabilités et réduire les phénomènes d'usure. Le travail est organisé en deux parties principales. La première partie est axée sur une analyse non-linéaire par éléments finis en grandes transformations; la rupture dynamique à l’interface de contact avec frottement, qui sépare deux corps (isotropes et élastiques) en condition de pré-charge statique, est simulée. On définit comme étant une rupture une zone, initialement en adhérence, qui change son état en devenant glissante. Les propriétés des ruptures sont analysées pour une surface plane entre deux matériaux différents en fonction de l’énergie de nucléation; l’effet de la rugosité de surface est ensuite analysée. En outre, la rupture "cumulatives" dans les aspérités et les conditions pour le couplage ou le non-couplage entre les ondes qui se propagent dans les deux corps sont étudiées. Dans la deuxième partie, l'amorçage du glissement entre deux corps en contact constitués de matériaux différents et séparés par une interface avec frottement, est simulée. L’évolution, en fonction du temps, des forces globales (normale et tangentielle) a été mise en relation avec les phénomènes locaux qui se déroulent à l’interface. L'analyse montre comment les micro-slips à l'interface, en agissant comme ruptures localisées, déclenchent les macro-slips entre les deux corps. L'interaction entre les dynamiques locale du contact et globale du système a été aussi étudiée. Enfin, une analyse paramétrique est menée en fonction de plusieurs paramètres (loi de contact, coefficient de frottement, amortissement matériau, charge normale, etc.). Les résultats mettent en avant le rôle-clé des micro-slips et des précurseurs (propagations d'ondes détectables qui ont lieu pour des valeurs de la force tangentielle globale inférieures à la valeur prévue par la loi de frottement) dans l'amorçage du macro-slip entre les deux corps. En fonction de leur distribution et de leur intensité, l'évolution des forces de contact change en passant d'un comportement de type stick-slip à un glissement continu. La dynamique locale au contact (propagation des ondes et ruptures) a été reliée au comportement global du système (stick-slip, glissement continu, vibrations induites); l'effet des paramètres du contact et du système sur le transfert d'énergie vibrationnelle entre le contact glissant et le système a également été examinée: en fonction de leurs valeurs, on peut avoir différentes modalités d'excitation du système (par une distribution de micro-slips ou par des macro-slips) et différentes processus de propagation et dissipation d'énergie. Les résultats numériques obtenus dans les deux parties de la thèse sont cohérents avec les résultats expérimentaux de la littérature. / This thesis is addressed to the understanding of the mechanisms at the origin of the contact wave fields at frictional interfaces and its relationship with the local characteristics of the surfaces in contact, as well as with the global dynamics and macroscopic frictional behaviour of the system. The aim of this work is to provide insights on the generation and propagation of the waves through the contact both to avoid instabilities and to control their effect on friction. The work is organized in two main parts. The first part presents the development of a non-linear finite element analysis in large transformations of the dynamic rupture at the interface with contact friction separating two bodies (isotropic and elastic) without relative motion. A rupture is considered when an initially sticking zone shifts in sliding state. The properties of the obtained ruptures are analyzed for a flat interface between dissimilar materials in function of the nucleation energy; then the effect of the interface roughness is analyzed. The differentiated rupture inside the asperities and the conditions for coupling and uncoupling between the waves radiating in the two bodies have been also investigated. In the second part, the analysis deals with the sliding onset between two bodies in contact. The sliding between two bodies made of different isotropic elastic materials and separated by a frictional interface is simulated. The evolution along the time of the global normal and tangential forces is analyzed, relating it to the local phenomena occurring at the interface. This part tries to investigate how micro-slips at the interface, acting as distributed ruptures, trigger the macro-slips between the two bodies. The interaction between local and global dynamics is also studied. Finally a numerical parameter space study is carried out, as a function of several system parameters (contact law, friction coefficient, material damping, normal load, translational velocity and regularization time). The results show the key role of the micro-slips and precursors (detectable wave propagations that occur at tangential global force well below the critical value expected by the friction law) in triggering the macro-slip between the two bodies. Depending on their distribution and magnitude the evolution of the contact forces passes from stick-slip-like behaviour to continuous sliding. The local dynamics at the contact (wave and rupture propagation) is linked to the global behaviour of the system (stick-slip, continuous sliding, induced vibrations); the effect of the contact and system parameters on the transfer of vibrational energy between the sliding contact and the system is investigated. The numerical results obtained by the two parts of the work show a good agreement with experimental results in literature.

Ce travail porte sur le développement d’une nouvelle technique expérimentale dédiée à l’étude de la rhéologie mise en jeux lors du glissement d’une pointe rigide sur une surface de polymère. Ce travail s'est déroulé progressivement de l'échelle mésoscopique vers l'échelle nanométrique. Pour cette dernière, la zone ciblée est la zone interfaciale confinée et cisaillée.Pour mettre en évidence les comportements de la zone cohésive, nous avons étudié un système de réseaux interpénétrés de polymères (RIPs) CR39-PMMA. Grâce à leurs propriétés ajustables, nous pourrons utiliser les RIPs sont utilisés comme substrat pour étudier la zone interfaciale en variant facilement les paramètres rhéologiques.Pour étudier les propriétés de la zone interfaciale, des couches phospholipidiques de DSPC ont été choisies comme matériau modèle. Leurs structures ont été étudiées par la réflectivité spéculaire de neutron. Nous montrons que la structure des couches supportées de DSPC est robuste, et le taux d’humidité́ relative joue un rôle important sur la structure. Les essais de glissement sur des couches de DSPC ont permis de relever les influences des paramètres mécaniques et environnementaux sur la contrainte de cisaillement Le développement du NanoTribo-FRAPP permet de caractériser le cisaillement des couches de DSPC sur une lame de verre, tout en mesurant la vitesse d’écoulement locale des couches moléculaires nanométriques. Nous pouvons ainsi estimer les plans de glissement en fonction de la vitesse. / This work deals with the development of a new experimental technique and its application to study the rheology of a highly confined and sheared interfacial zone involved in the sliding of a rigid tip on a polymer suface. This tribological work has been conducted gradually from the mesoscopic scale to the nanoscale.To highlight the behavior of the cohesive zone, we studied an interpenetrating polymer network system (INPs) CR39-PMMA. Thanks to their adjustable properties, we may use the INPs as a substrate to study the interfacial zone by easily varying the rheological parameters.To study the rheological properties in the interfacial zone, the phospholipid layers of DSPC have been chosen as model material. The structures have been studied by the neutron reflectivity experiments. We show that the structure of supported layers of DSPC is robust, and the relative humidity plays a key role on it. Sliding tests on the DSPC layers reveals the influences of mechanical and environmental parameters on the shear stress. The development of NanoTribo-FRAPP allows to characterize the shear conditions of DSPC layers, with the measurements of local velocity of these of nanoscale molecular layers. This gives us access to estimate the slip planes as a function of imposed velocity.

Nous présentons dans cette thèse une adaptation de la technique de vélocimétrie par marquage moléculaire (MTV) aux micro-écoulements gazeux. Les effets de luminescence de l’acétone gazeuse excitée par un rayonnement UV, mis en jeu dans la MTV, ont été analysés en vue d’une application en vélocimétrie à basse pression. La phosphorescence de l’acétone diminue fortement avec la pression, pour devenir non détectable à des pressions de l’ordre du kPa. En revanche, la fluorescence reste détectable à des pressions de l’ordre de la dizaine de Pa. L’analyse des déplacements de molécules luminescentes au sein de l’écoulement porteur a montré que les effets de la diffusion moléculaire sont importants et augmentent avec la raréfaction du gaz. Une méthode de reconstruction, basée sur l’équation d’advection diffusion, a été développée. Elle permet d’extraire le profil de vitesse à partir de l’analyse du déplacement et de la déformation de la zone marquée, en prenant en compte la diffusion des molécules luminescentes. L’analyse d’un écoulement de Poiseuille dans un canal de section rectangulaire et de dimensions millimétriques, sous des pressions de l’ordre de 100 kPa, a montré la capacité de la MTV à extraire avec précision la vitesse locale en écoulements confinés, lorsque la méthode de reconstruction est appliquée. Une feuille de route pour l’analyse future par MTV des écoulements raréfiés, notamment dans le régime glissant, est finalement proposée. / In the present thesis we present an adaptation of Molecular Tagging Velocimetry (MTV) to gas microflows. The photo-luminescence effects of gaseous acetone excited by UV light, implemented in MTV, have been analyzed in various pressure conditions. The acetone phosphorescence shows a drastic decrease with pressure and becomes non measurable for pressures lower than 1 kPa. On the other hand, fluorescence shows a slower decrease and remains clearly detectible at pressures as low as 10 Pa. The motion of tracer molecules within the carrier flow has been studied. The analysis of the displacement of the tagged molecules has shown the strong influence of molecular diffusion, this influence being increased with the gas rarefaction. A reconstruction method based on the advection-diffusion equation has been developed. It allows to extract the velocity profile from the analysis of the displacement and deformation of the tagged region, taking into account the diffusion of tracer molecules. This reconstruction method has been successfully implemented to analyse a Poiseuille flow in a rectangular millimetric channel, under atmospheric pressure conditions, and the capability of MTV to accurately extract the local velocity in confined gas flows has been demonstrated. Finally, some short term perspectives have been proposed with the aim to help achieving rarefied flows analysis by MTV.