Este estudo apresenta uma investigação sobre a possibilidade de adotar o processo de solda por agitação e fricção, ou \"friction stir welding\" em substituição ao processo usual de fixação por rebitagem, na construção de um painel de fuselagem aeronáutica de dimensões compatíveis com uma aeronave regional com capacidade aproximada de cinqüenta assentos. A investigação avalia aspectos técnicos de engenharia, tais como capacidade de unir materiais heterogêneos, resistência mecânica, vida em fadiga da estrutura, aspectos de produtividade e custos associados. O processo de solda por agitação e fricção ocorre em estado sólido, não requer a introdução de um terceiro material ou qualquer tipo de arco elétrico ou atmosfera de gás inerte. Os materiais a serem unidos não atingem o ponto de fusão, mas são submetidos à severa deformação plástica, sendo misturados sem que haja fusão. As características mecânicas resultantes dos componentes soldados são equivalentes ou superiores às características dos componentes rebitados. Sob o ponto de vista econômico, existem ganhos em redução de custos de mão de obra e aumento na velocidade de produção, quando comparado ao processo de rebitagem. / This study presents an investigation about the possibility of use friction stir welding process to replace the usual riveting process to build an aeronautic fuselage panel which has its dimensions compatible to a fifty seats regional aircraft. The investigation evaluates engineering technical aspects as the capability to join dissimilar materials, the mechanical strength, structure\'s fatigue life, productivity aspects and associated costs. Friction stir welding is a solid state process where a third material deposition is not required, as well is not required any electric arc or inert gas atmosphere. The materials to be joined do not reach the fusion point, but are subjected to severe plastic deformation, being mixed without melting. The mechanical behavior of welded components is equivalent or better than the behavior of riveted components. From financial standpoint, there are benefits on labor costs reduction and increased production rate, when compared to the riveting process.

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Orientador: Paulo Vatavuk / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-19T08:44:36Z (GMT). No. of bitstreams: 1 Schroder_FranciscoCarlos_M.pdf: 3459488 bytes, checksum: a1a920f7c561f9c61836a4366dc4a636 (MD5) Previous issue date: 2011 / Resumo: O objetivo deste trabalho é pesquisar e esclarecer as divergências dos valores de rugosidade equivalente de tubos comerciais de diferentes materiais, notadamente os de aço e ferro, que são mais comuns em aplicações industriais e de saneamento, no transporte de líquidos. Como estes valores muitas vezes não são coincidentes, apesar de originarem de materiais e processos similares, geram dúvidas quando de sua escolha para formulação do fator de atrito, que é utilizado para o cálculo de perdas de carga distribuídas em sistemas de bombeamento. O trabalho propõe recomendações para melhorar a estimativa da rugosidade em tubos metálicos rugosos, baseado em casos reais de dimensionamento de perdas por atrito em projetos de bombeamento de água / Abstract: The objective of this study is to investigate and to clarify the differences in the values of equivalent roughness of commercial pipes of different materials especially the steel and iron pipes that are more common in industrial and sanitation applications for transport of liquids. Since these values do not coincide despite similar of materials and processes inaccuracy in the formulation of the friction factor can occur, they create doubts when comes the choice for the formulation of the friction factor, which is used to calculate pressure drops distributed in pumping systems. This work proposes recommendations for improving the estimate of roughness in metallic tubes based on real cases rough sizing of friction loss in water pumping projects / Mestrado / Recursos Hidricos, Energeticos e Ambientais / Mestre em Engenharia Civil

Orientador: Auteliano Antunes dos Santos Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia mecanica / Made available in DSpace on 2018-08-04T10:30:47Z (GMT). No. of bitstreams: 1 Santos_AliandroHenriqueCosta_M.pdf: 10616712 bytes, checksum: 57733fcc9ba5b442556901d87af2a403 (MD5) Previous issue date: 2005 / Resumo: Os freios utilizados para veículos são normalmente por atrito. A tendência internacional é no sentido de utilizar somente freios por atrito à disco, eliminando os atuais tambores empregados em rodas traseiras para automóveis de passageiros. O aumento do desempenho de veículos automotivos e a conseqüente alteração em suas características dinâmicas tem levado a criação de sistemas de freio mais eficientes. A expansão do mercado para pastilhas e a necessidade de redução de custos tem levado ao surgimento de materiais sem a qualidade necessária para o desempenho da frenagem. Os procedimentos de ensaio existentes hoje e que permitem avaliar a qualidade do material de atrito são complexos e normalmente fazem uso de dinamômetros com inércia, de custo muito elevado e não disponíveis nos centros e instituições de pesquisa brasileiras. Este trabalho teve como objetivo caracterizar o desempenho de materiais de atrito para pastilhas de freio através da criação de um procedimento de ensaio que englobe as principais variáveis que influenciam o processo de frenagem. Foi utilizado o Dispositivo de Ensaio de Amostras, dinamômetro de baixo custo disponível no Departamento de Projeto Mecânico da FEM-Unicamp. Um planejamento experimental ortogonal L9 permitiu o estudo da influência de variáveis envolvidas no processo de utilização de pastilhas, que são a marca, o fornecedor, a pressão específica, a velocidade e a temperatura, em dois níveis de desgaste. Os resultados mostram que o procedimento proposto pode ser utilizado na avaliação da qualidade do material de atrito de pastilhas, de forma rápida, eficiente e com baixo custo / Abstract: Automotive brake systems are mainly friction based. The world tendency is toward using disc brakes instead of drum brakes, which are usually installed in the rear wheels. The increase in the performance of automotive vehicles and the changes in the dynamic characteristics have conducted to more efficient brake systems. The expansion of the brake pads market has impacted the quality of the products. Low quality products have been found, specially were no control exists. The actual test procedures to evaluate the quality of rnction materials are compIex and most of them require a fuII scale inertial dynamometer. Those machines are very expensive and most of the Brazilian research and quality centers do not have them. This work aimed to deveIop a procedure to characterize the performance of brake pads and analyzing the main factors of influence. A Iow cost non-inertial dynamometer, called D.E.A. - Fixture to text sampIes of friction material, was used. It is instalIed in the Department of Mechanical Design - FEM of the State University of Campinas, in Brazil. An experimental orthogonal design L9 was used to take the factor of influences in account. They are identified and the main factors are: contact pressure, disc speed, temperature and pad manufacturer. The influences were evaluated in two leveI of pad wearing. The results show that the procedure can be used to evaluate the quality of the rnction material for brake pads, in a fast and not expensive way / Mestrado / Projeto Mecanico / Mestre em Engenharia Mecânica

This thesis involves the analysis of four classes of nonlinear oscillators. We investigate a damped planar pendulum subject to vertical sinusoidal displacement of appropriate amplitude and frequency, a Hamiltonian planar pendulum with support point oscillating in the vertical direction, a forced spherical pendulum as a constrained dynamical system and a spinning double pendulum with the two masses oscillating in transversal planes. The motivation for this research was to understand and determine the fundamental dynamical properties of the four model systems. For this purpose analytical and numerical tools have been employed. Linearization, phase portraits, Poincare sections, basins of attraction, KAM theory, Lyapunov exponents and normal form theory have been considered as examples. For the damped planar pendulum a rigorous analysis is presented in order to show that, in the presence of friction, the upward equilibrium position becomes asymptotically stable. Furthermore, using numerical tools, the dynamics of the system far from its equilibrium points is systematically investigated. For the undamped and parametrically perturbed planar pendulum, we use KAM type arguments to rigorously prove the stability of the equilibrium point corresponding to the upside-down position. For the spherical pendulum a numerical framework is developed, which allows orbits to explore the entire sphere. We show that the qualitative change in the Poincare sections from regular to chaotic behaviour is in excellent qualitative agreement with corresponding computations of the Lyapunov exponents. Finally we study the dynamics of the spinning double pendulum by using normal form theory. We have identified the regions in physical parameter space where a codimension-two singularity occurs. An algorithm for the Cushman-Sanders normal form is constructed and analyzed. A representative model for the truncated normal form is presented.

Cette thèse étudie de nouvelles approches pour contrôler le coefficient de frottement dans les contacts en lubrification elastohydrodynamique (EHL) grâce à l'utilisation de surfaces texturées. Par l'expérimentation et la simulation numérique, les phénomènes gouvernants le frottement en EHL sont tout d'abord identifiés, puis l'effet de différentes surfaces texturées (cavités, rainures, ripples) sur le coefficient de frottement est mis en évidence. Les résultats indiquent que le coefficient de frottement peut être contrôlé par l'ajustement adéquat de la géométrie des textures. / This thesis focuses on finding new ways to control the friction coefficient in elastohydrodynamically lubricated (EHL) contacts through the use of surface textures. Experiments and numerical simulations are employed to first identify the governing phenomena responsible for friction in EHL and then to assess the effect of different surface textures (dimples, grooves and ripples) on the friction coefficient. The findings indicate that the coefficient can be controlled by carefully adjusting the texture geometry.

No description available.

Les travaux accomplis dans le cadre de ce projet de recherche ont permis de réaliser un dispositif électromécanique fonctionnel pour l’actionnement d’embrayage. Le dispositif utilise une vis mère et un écrou pour transformer le mouvement rotatif d’un moteur électrique en mouvement linéaire. Le dispositif peut être placé n’importe où dans un véhicule grâce à un conduit hydraulique en circuit fermé qui assure le transfert de puissance mécanique vers l’embrayage. La performance et les composants clés ont été optimisés à l’aide de résultats de simulation. Un compromis est ainsi fait entre le coût, l’efficacité et la performance du système. Un contrôleur par compensation de friction ou par mode glissant permet de minimiser les effets néfastes de la friction dans le mécanisme de transfert sur la précision et le temps de réponse. Des essais sur véhicule démontrent la fonctionnalité du concept pour l’actionnement d’embrayage.

Dans l’industrie de la mise en forme des matériaux métalliques, le frottement joue un rôle très important. Cependant, il est difficile à contrôler totalement, notamment dans les procédés complexes où le taux de nouvelles surfaces générées lors de la déformation plastique est important. La thèse propose d’identifier par analyse inverse les propriétés tribologiques du matériau, directement à partir de la courbe donnant la force en fonction du déplacement pour un procédé d'extrusion directe. La conception d’une filière d’extrusion, avec des dimensions optimales pour maximiser l’influence du frottement a été faite à l’aide de calculs analytiques en se basant sur des critères particuliers tels que: la capacité maximale de la presse, la maximisation de la longueur de frottement, le rapport entre la puissance de frottement et la puissance de déformation et la limite du taux de réduction pour éviter l’endommagement du matériau. Comme dans le procédé d’extrusion il existe un certain couplage entre l’influence des paramètres rhéologiques et des paramètres tribologiques, des tests de compression d’éprouvettes «haltères» ont été réalisés dans une première étape afin d’identifier la loi de comportement rhéologique du matériau. La conception du test proposé a été validée par des simulations numériques avec FORGE2®. Les simulations numériques ont été également effectuées pour analyser la sensibilité des paramètres rhéologiques et tribologiques du matériau sur la force d’extrusion. L’influence de la géométrie de la filière sur la courbe de force a été examinée en détail. Une campagne d’essais a été réalisée pour l’alliage d’aluminium AA5083. La loi de comportement du matériau a été en conséquence identifiée par analyse inverse à partir de la courbe expérimentale donnant la force de compression des éprouvettes «haltères». Dans une deuxième étape, les propriétés tribologiques du matériau pour différents modèles de frottement ont été ensuite identifiées par analyse inverse à partir de la courbe donnant la force d’extrusion. La méthode d’identification par analyse inverse a été enfin validée par la simulation d’un procédé industriel d’extrusion. La campagne d’études expérimentales a été complétée par la caractérisation du matériau par des mesures de dureté, des mesures de diffraction des rayons X et des mesures de diffraction des électrons rétrodiffusés (EBSD) afin de mettre en évidence l’évolution de la surface des pièces après la déformation plastique. Les résultats indiquent que le frottement a une influence importante sur l’évolution des orientations cristallines de la surface du matériau extrudé. / In the industry of metal forming, friction plays a very important role. However, it is difficult to control completely this phenomenon, especially in the complex processes where the rate of the new surface generated during the plastic deformation is important. The thesis proposes to identify by inverse analysis the tribological properties of material, directly starting from the curve of the load versus the displacement of a direct extrusion process. The design of an extrusion die, with optimal dimensions to maximize the influence of friction, was carried out using analytical calculations based on particular criteria such as: the maximum capacity of the press, the maximization of the friction length and of the ratio between the friction power and the deformation power, the limit of the reduction rate to avoid damage of the material. Since in the extrusion process there is a certain coupling between the influence of the rheological parameters and the tribological parameters, compression tests using "dumbbells" specimens were carried out in a first stage in order to identify the rheological behavior law of the material. The design of the proposed test has been validated by numerical simulations using FORGE2®. The numerical simulations were also performed in order to analyze the sensitivity of rheological and tribological parameters of the material on the extrusion load. The influence of the geometry of the die on the extrusion load curve has been examined in detail. A campaign of tests was carried out for the AA5083 aluminum alloy. The behavior law of the material was consequently identified by inverse analysis starting from the experimental load curve of compression tests using "dumbbells" specimens. In a second step, the tribological properties of the material for different friction models were then identified by inverse analysis starting from the extrusion load curve. The method of identification by inverse analysis was finally validated by the simulation of an industrial extrusion process. The campaign of experimental studies has been completed by the characterization of the material by measurements of hardness, X-ray diffraction measurements and electron backscattered diffraction (EBSD) measurements in order to highlight the evolution of the surface of the extruded specimen after the plastic deformation. The results indicate that friction has an important influence on the evolution of crystal orientations of the surface of the extruded material.

Mechanical fasteners are used extensively in the joining of two or more metal plates or sheets. Riveted joints have been the joints of choice mainly for the Aerospace Industry. However for this research, Friction Hydro Pillar Processing has been used to develop and characterise a new riveting technique termed Friction Hydro Pillar Riveting (FHPR). Two overlapping 3.17 mm Ti-6Al-4V sheets were joined together using Ø6 mm rivet which was friction processed. This research has focussed on the initial development of Friction Hydro Pillar Riveting thereby establishing a basic understanding of the influences of main process parameters, rotational speed and axial force - and also joint configurations. The results showed that with a decrease in the bottom hole chamfer angle, there was resulting overall increase in the rivet joint pull off strength. From the best performing joint configuration in pull off tests, shear tests were conducted whilst a blind hole FHPR joint was also done and tested in pull off and shear strength. The shear test fracture surfaces exhibited ductile failure. The microstructure of the joints was thus evaluated. From parent material, heat affected zone and to weld zone there was a variation in the microstructure analysed. The hardness profiles showed increased hardness in the weld zone which partly explained the shear results. The hardness increase was mainly due to grain refinement in the weld zone by the Friction Hydro Pillar Riveting process.