Made available in DSpace on 2014-06-11T19:32:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-10Bitstream added on 2014-06-13T19:22:34Z : No. of bitstreams: 1 souza_cn_dr_guara.pdf: 5417862 bytes, checksum: 45f7392a335fde8b9a67ef7d60be0ce9 (MD5) / Este trabalho tem como objetivo avaliar a influência dos tempos de fotopolimerização nas resinas odontológicas, onde quatro resinas compostas foram utilizadas, sendo três micro híbridas e uma nanoparticulada. Esses compósitos foram submetidos ao desgaste abrasivo de esfera rotativa pelo método de ball cratering. Para tal ação foi projetado e construído um dispositivo de desgaste por micro abrasão de esfera rotativa livre de três corpos. Os corpos de prova foram confeccionados e embutidos em uma matriz de alumínio, com uma profundidade de 2mm. Usam-se o aparelho LED RADII, com os tempos de exposição de 20, 30 e 40 segundos e uma esfera com 15 mm de diâmetro de aço temperada, retificada e revenida. A lama abrasiva utilizada nesse estudo foi uma solução composta por 20% de talco (USP/200) e 80% de soro fisiológico, na quantidade de 3 gotas por segundo. Para comprovação dos resultados obtidos, utilizaram-se os testes de: Espectroscopia por Dispersão de Energia (EDS), Infravermelho por Transformada de Fourier (FT-IR), Análise Termogravimétrica (TGA), micro dureza Vickers, ensaio de desgaste de micro abrasão por esfera rotativa pelo método de ball cratering e a análise da superfície desgastada por Microscopia Eletrônica de Varredura (MEV). Esta análise foi realizada para verificar o real mecanismo de desgaste ocorrido. Os resultados obtidos comprovam que o tempo recomendado pelos fabricantes, tem a capacidade suficiente de fotopolimerizar toda a matriz orgânica, comprovaram também que a resina nanoparticulada obteve em todos os ensaios os melhores resultados em relação às resinas híbridas, e que a cultura do acréscimo de até 20s além do recomendado não tem influência direta em relação ao desgaste abrasivo. / This work has as an objective to evaluate the influence of photopolymerization in odontological resins, where composed four resins were used, being three of them micro hybrid and one nanoparticulated. These composites were submitted to abrasive wear and tear of rotative sphere by the method ball cratering. For such action a device of micro abrasion of rotative sphere was designed and built free of three bodies. The bodies of proof were produced and put in a matrix of aluminum with a depth of 2mm. The device used was a LED RADII, with exposition time of 20, 30 and 40 seconds and a sphere of 15mm diameter made of tempered steel, rectified and soften, the abrasive lama used in this study was a solution composed by 20% of powder (USP/200) and 80% of physiological serum released at 3 drops per second. For verification of the results obtained the tests of Energy Dispersion Spectrograph (EDS) was used, transformed Infra red of Fourier (FT-IR), Thermogravimetric Analysis (TGA) Vickers micro hardness, wear and tear of micro abrasion by rotative sphere by the method ball cratering and the analysis of worn superficies by Sweeping Electronic Microscopy (SEM). This analysis was carried out to verify the real mechanism of the worn occurred. The results obtained prove that the time recommended by the manufacturer has enough capacity to photopolymerized all the organic matrix, it also proved that the resin nanoparticulated obtained in all the essays the best results in what concerns to the hybrid resins. And the culture of the addition of 20 seconds besides what is recommended has no direct influence in relation to the abrasive wear and tear.

O objetivo deste trabalho é o desenvolvimento de um sistema de monitoramento capaz de identificar em processo o mecanismo de desgaste ao qual o rebolo está sendo submetido durante a retificação. Assim, inicialmente foram pesquisados os meios físicos, os tipos de sensores e estratégias utilizadas nos sistemas de monitoramento, o estágio atual de desenvolvimento e suas aplicações. Para que este sistema seja confiável e eficiente foi necessário estudar detalhadamente a fenomenologia dos mecanismos de desgaste do rebolo. Este estudo permite definir parâmetros para identificação do tipo de desgaste que está ocorrendo, baseado em indicações fornecidas pelo monitoramento de variáveis cujo comportamento é conhecido, como potência consumida pelo motor do rebolo e vibração ou ainda por medições metrológicas. Dois sistemas ópticos de mapeamento da superfície do rebolo são apresentados e estes sistemas serviram como base para o desenvolvimento de um novo sistema de mapeamento da Distribuição da Energia Acústica de Retificação no rebolo, DEAR. Realizaram-se experimentos com o novo sistema, monitorando simultaneamente outros meios físicos. Procurou-se desta forma relacionar o padrão gráfico do mapa gerado pelo novo sistema com o tipo de desgaste que estava ocorrendo, baseado nas informações obtidas no estudo dos mecanismos de desgaste. A análise dos resultados mostraram que o mapa DEAR pode ser utilizado para identificar o tipo de mecanismo de desgaste predominante que está ocorrendo no rebolo, em processo. Esta informação é muito útil na escolha de ações corretivas para problemas da retificação. / The objective of this work is the development of a monitoring system able to identify in process the grinding wheel wear mechanism. Thus, initially the physical quantities, sensors types and monitoring systems strategies, developing status and their applications were researched. To get a reliable and efficient system was necessary a detailed study of the grinding wheel wear mechanism phenomenology. This study allows to define parameters in order to identify which type of wear is occurring, using indication obtained by the monitoring variables whose behavior is known, such as grinding power, vibration or metrological measurement. Two grinding wheel surface optical mapping systems are presented, those systems were utilized as base to developing a new mapping system of Grinding Acoustic Energy Distribution (DEAR). Experiments have been done with the new system, monitoring simultaneously other physical quantities, looking for a way to link the mapping graphic patterns generates by the new system with the wear type which was occurring, based on information obtained from the wear mechanism study. The results and analysis have shown that the DEAR map can be used to identify the predominant wear mechanism type which is occurring on a grinding wheel, in process. This information is very useful in the corrective actions when facing a grinding problem.

Le procédé de rodage par pierres abrasives est actuellement utilisé pour produire en grande série des chemises de carter cylindre avec des propriétés fonctionnelles spécifiques. La qualité de forme, la rugosité et l'aspect des surfaces ainsi rodées déterminent grandement les performances mécaniques et écologiques des moteurs. Le processus de rodage, mécaniquement complexe, fait intervenir des machines complètement dédiées et optimisées pour les rodages classiques. Après une étude détaillée des machines de production actuelles, de leurs performances et de leurs limites, l'objectif de recherche de flexibilité du procédé pour l'industriel Renault s'est traduit par deux développements : une modélisation de l'abrasion avec une simulation du procédé pour mieux le comprendre et la conception d'un prototype de machine de rodage à hautes performances pour tester d'autres méthodes de rodage.La simulation est basée sur la double discrétisation de l'espace-et du temps et sur un modèle de coupe original. La discrétisation de l'espace permet de représenter à une échelle macroscopique le rodoir et la pièce à usiner et de tenir compte des contacts locaux entre eux. Les propriétés microscopiques et mésoscopiques de la surface rodée sont étudiées à cette échelle. La discrétisation temporelle autorise la prise en compte de la cinématique de la machine. Le modèle de coupe repose sur l'interaction des courbes de portance du rodoir et de la chemise. Son exploitation au niveau macroscopique permet de prédire l'enlèvement de matière, la force de contact locale ainsi que l'aspect de la surface rodée et leurs évolutions au cours du rodage. Cette simulation est validée par de nombreuses expériences.Ce document présente la conception, la réalisation et la mise au point d'un prototype de machine de rodage avec des actionneurs électriques à performances dynamiques élevées. Une commande numérique permet le pilotage synchronisé de la rotation et du battement et autorise l'interpolation de trajectoires. L'expansion radiale peut être pilotée en position ou en force. Nous avons proposé de nouvelles trajectoires originales dans l'objectif d'augmenter la productivité du procédé et dans le but de générer de nouvelles textures. / The honing process with abrasive stones is currently used to mass produce the liners cylinder block with specific functional properties. The quality of shape, the roughness and the textural appearance of honed surface determine the mechanical performance and ecological engines. The honing process is mechanically complex and involves machines completely dedicated and optimized for classical honing operations. After a detailed study of current production machines, their performance and their limitations, the research goal of flexible process for industrial Renault has led to two developments: a model of the abrasion with a process simulation to better understand and design of a prototype machine with high performance to test other methods of honing.The simulation is based on a space-time discretization and an original model of stock cutting. The space discretization is used to represent a macroscopic scale the honing tool and the workpiece and to take into account local contacts between them. Microscopic and mesoscopic properties of the honed surface are studied at this level. Time discretization allows taking into account the kinematics of the machine. The cutting model is based on the interaction of the bearing area ratio curves of the honing tool and the liner. Operation at the macroscopic level predicts the removal of material, the contact force and the local aspect of the honed surface and their changes during the operation. This simulation is validated by numerous experiments.This paper presents the design, the implementation and the development of a prototype machine with electric actuators for high dynamic performance. A digital controller allows the synchronized control of the rotation and stroke to allow trajectories interpolation. The radial expansion can be controlled in position or force. We proposed new original trajectories in the objective of increasing the productivity of the process and to generate new surface textures.

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<p>The objective of this research was to work with industrial partners to develop and apply innovative and intelligent improvement to their production processes in order to achieve a higher level of productivity and quality while lowering cost.</p> <p>Two projects were completed and are discussed in this work. The first project was focused on improving tooling in a milling process of high value parts by varying coatings and geometries of the tooling. The second project involved implementing statistical process control (SPC) using control charts and process capability metrics through customized software.</p> <p>In the first project, the industrial partner was experiencing rapid wear of tools when milling NiCrMoV steel. A detailed material characterisation study revealed the likely cause was the presence of un-tempered martensite having high hardness. Cutting tools were then chosen to compare the performance of tools with varying rake angle and coating; where all other geometry/features were identical. It was found that the best performing tooling had a relatively more aggressive rake angle at 16º, and a PVD coating consisting of TiAlN + Al₂O₃+ ZrN; showing a tool life 300% greater than the baseline tooling. Inspection of the worn tools by SEM, EDX, and Raman spectroscopy revealed that the Al₂O₃ and ZrN coating layers detached long before the failure.</p> <p>In the second project, software was developed collaboratively with an industrial partner for a CNC turning process. The process was semi-automated, and used 100% inspection of parts. Part measurement data was recorded by the software, allowing for SPC to be applied to identify common-cause sources of variation. The software was then able to make offset recommendations in real-time to correct for variation. Providing process history for quality assurance (QA) also allowed for identifying of several areas for improvement in the process which were corrected, considerably reducing variability.</p> / Master of Applied Science (MASc)

<p>Abrasive waterjet (AWJ) machining is a complex, non-conventional machining process involving numerous input parameters including hydraulic, abrasive, mixing and cutting that must be accurately manipulated to guarantee precise cutting and quality. Currently, available models are empirical or require continuous calibration, or extensive experimental work. To reduce the calibration and experimental time required for accurate prediction of AWJ cutting, computational fluid dynamics (CFD) is being utilized to model the nozzle flow interaction; high pressure water is pushed through the orifice into the mixing chamber, pulling the abrasive into the flow and cohering in the focus tube. Initial research worked towards understanding the effect that input parameters - such as pressure, particle size and shape, focus tube length and volume fraction of air in fluid mixture - have on the velocity profile through the nozzle and upon exit to the atmosphere. Once understood, the CFD model can be utilized to vary mass-inlet, mixing head, orifice and focus tube dimensions to optimize velocity profile of abrasive material including magnitude and jet coherency. Primarily focused on pump pressure, which is limited by technology - an optimized AWJ nozzle will increase material removal rate and/or enhance cut quality without making changes to any other AWJM components.</p> <p>Utilizing the velocity output information from the CFD model, a depth of penetration erosion prediction model was generated. Based on methodology from Finnie, and modified by Hashish and ElTobgy, a multi-particle erosion model of an impacted work piece is developed. With an updated formulation for the specific cutting resistance of a work piece, dependent on particle velocity and nozzle traverse speed, the erosion prediction over the sixty-five different setups modelled and tested experimentally, reduced error on average 41.8%. Moreover, the development of this model created multi-layered surface plots, illustrating for quick reference, the erosion of a work piece for a given set of parameters albeit mass flow rate, pump pressure and traverse rate.</p> <p>Further, a database of quick reference guides, including variable input settings, nozzle types, garnet types and work piece materials can easily be developed. Finally, a new methodology for the leading edge of the waterjet is described and can be incorporated into the erosion simulation by making use of the ``top-hat`` profile generated in the CFD model. This would reduce reliance on model constants to account for secondary cutting, or when particles do not contribute to cutting but are simply entrained in the fluid flow.</p> <p>Both models demonstrated good correlation with experiments or literature. The use of these models will increase understanding of the complex abrasive waterjet process and reduce the need for costly experiments moving forward.</p> / Master of Applied Science (MASc)

<p>Changes to the surface condition of a grinding wheel caused by excessive wear can result in geometric inaccuracy and severe thermal damage to a workpiece. As a precision metal removal process, grinding is typically a finishing operation and such errors are costly in both materials and lost time. Unfortunately grinding wheel performance is difficult to predict, and workpiece damage is commonly prevented by frequent dressing of the wheel surface. However, such over dressing is also costly in unnecessary machine down time and consumption of the grinding wheel. Monitoring systems have been developed in an effort to prevent damage to the workpiece and unnecessary dressing, but various difficulties have prevented any single system from achieving widespread application.</p> <p>The following body of research focuses on the investigation and development of a pneumatic sensor for monitoring the surface condition of a grinding wheel. These sensors are relatively simple, robust and inexpensive, and well suited to in situ applications. While these sensors are traditionally used to measure displacement of static or quasi-static surfaces, research into dynamic applications has shown they can detect the features or topography of a moving surface. Inspired by these developments, a monitoring method employing both the static and dynamic measurement capabilities of the sensor is proposed with applications to both metal-bonded and vitrified grinding wheels.</p> / Master of Applied Science (MASc)