Orientador: Amauri Hassui / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T13:19:17Z (GMT). No. of bitstreams: 1 Menezes_LucianodeJesus_M.pdf: 3153404 bytes, checksum: 2d45745d89221fa761d7b0111aaf819a (MD5) Previous issue date: 2014 / Resumo: A evolução dos sistemas CAD/CAM, das máquinas-ferramenta CNC e das geometrias e materiais das ferramentas de corte tem tornado possível desenvolver processos de fabricação de moldes e matrizes mais eficazes. Normalmente, a quantidade de horas necessárias para a usinagem dos componentes dessas ferramentas é elevada e, mesmo assim, muitos dos perfis complexos não são possíveis de serem usinados por completo em centro de usinagem 3 eixos, necessitando a utilização de outras máquinas e processos, como a eletro-erosão (EDM), retificadoras e polimento manual. A utilização do fresamento com máquinas de usinagem 5 eixos tem sido um dos caminhos para a usinagem dos componentes complexos de moldes e matrizes, de modo a minimizar o uso de máquinas e processos adicionais. Com a finalidade de contribuir para melhorar a eficiência da fabricação de moldes e matrizes, este trabalho tem como objetivo estudar as condições dimensionais e as forças geradas no fresamento do Aço AISI D6 endurecido a 58HRC, usinado em um centro de usinagem 5 eixos com fresa de topo esférica. A condição dimensional estudada está relacionada com o perfil geométrico do corpo de prova, composto por raio e superfície plana. O estudo foi realizado utilizando 10 estratégias de usinagem, variando-se o ponto de contato da ferramenta com o corpo de prova, o sentido de usinagem e a velocidade de corte. As análises práticas realizadas mostraram que existe relação entre a tolerância geométrica, o desgaste da ferramenta e as estratégias de corte adotadas. Além disso, as condições, máquinas e equipamentos utilizados nos ensaios de usinagens descendentes 3 eixos obtiveram melhores resultados de tempo de vida da ferramenta e condição dimensional do corpo de prova / Abstract: The development of CAD / CAM systems, CNC machine tools and materials and geometries of cutting tools has become possible to develop more efficient manufacturing processes of molds and dies. Usually the amount of hours required for machining of the components of these tools is high. Also, many of the complex profiles are not possible to be completely machined in 3-axis machine center, requiring the use of other machines and processes, such as electro-erosion (EDM), grinding and hand polishing. The use of milling machines with 5-axis machining has been one of the paths for machining complex components from molds and dies, so as to minimize the use of additional machines and processes. In order to contribute to improve the efficiency of manufacturing molds and dies, this work aims to study the dimensional requirements and the forces generated when milling Steel AISI D6 hardened to 58HRC, machined in a machining center with 5-axis milling spherical top. The dimensional condition studied is related to the geometric profile of the specimen, consisting of ray and flat surface. The study was conducted using 10 machining strategies, varying the tool point of contact with the specimen, the machining direction and the cutting speed. The practical analyzes showed that there is a relationship between the geometric tolerance, tool wear and cutting strategies adopted. In addition, the conditions, machinery and equipment used in the machining tests descendants 3 axes obtained better lifetime results tool and dimensional condition of the specimen / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Cette thèse traite de la modélisation, conception, optimisation ainsi que de la validation expérimentale d'une machine à reluctance variable à double alimentation (BDFRM-Brushless Doubly-Fed Reluctance Machine) destinée aux éoliennes. La BDFRM est notamment considérée comme une alternative viable à la Machine Asynchrone à Double Alimentation (MASDA) dans les systèmes éoliens à vitesse variable. Elle maintient les avantages de coût de la MASDA tout en permettant l'utilisation d'un convertisseur de puissance réduit ainsi que la diminution des coûts d'entretien en raison de son fonctionnement sans balais. Une revue de la littérature fait apparaitre un manque de recherches concernant la définition de procédures de conception pour rendre cette machine plus populaire en général, et dans l'éolien en particulier. L'objectif principal de cette thèse est de contribuer à la maîtrise du processus de conception optimale de la BDFRM en proposant une approche méthodologique basée sur différents niveaux de modélisation et sur l'optimisation. Elle examine comment l'optimisation pourrait être appliquée à toutes les étapes de développement avec des objectifs distincts à évaluer. Plus précisément, elle se focalise sur la définition du problème d'optimisation sous contraintes et sur sa solution itérative en utilisant un algorithme déterministe couplé à des modèles semi-analytiques de différents niveaux. Les activités effectuées au cours de cette thèse peuvent être divisées en cinq parties principales. La première se réfère à l'étude de la BDFRM et de son principe de fonctionnement dans le contexte de l'énergie éolienne. La seconde partie examine les aspects de modélisation électromagnétique de la BDFRM en utilisant différentes approches. Deux modèles orientés pour l'optimisation ont été développés: le Modèle Semi-Analytique (SAM-Semi Analytical Model ) et le modèle multistatique de réseau de reluctances (MSRN-Multi-Static Reluctance Network). La mise en œuvre des modèles axés sur l'optimisation déterministe et leurs vérifications par des simulations utilisant la méthode des éléments finis (MEF) constituent la troisième partie. Il est possible de conclure qu'à partir des résultats de simulation que le SAM a un niveau de précision limité et qu'il est alors recommandé de l'utiliser dans les étapes de prédimensionnement, où le concepteur est plus intéressé par l'acquisition de résultats avec des temps de calcul rapides que par l'obtention d'une plus grande précision. Le MSRN, au contraire, présente des résultats d'une précision remarquable par rapport à la MEF, ce qui donne un compromis très intéressant entre précision et temps de calcul. Cette thèse a permis aussi de spécifier et réaliser un prototype de BDFRM en utilisant une approche d'optimisation présenté en quatrième partie. Ensuite, les données expérimentales obtenues à partir du prototype ont été confrontées aux résultats de la simulation pour valider les modèles, mettant l'accent sur le processus de modulation de flux par le rotor à réluctance, en particulier l'inductance mutuelle entre les enroulements. Bien que les résultats soient dans un sens satisfaisant pour la validation des modèles, il y a des différences qui ont exigés un examen plus approfondie. Une discussion sur les hypothèses les plus probables a donc été effectuée, celle-ci a souligné le rôle important du processus de fabrication de la machine sur ses performances. La cinquième partie explore à travers une étude de cas l'utilisation de la procédure de conception de la BDFRM proposée dans cette thèse pour les éoliennes. En conclusion générale, on peut affirmer que la BDFRM est potentiellement une bonne candidate pour être utilisée dans les systèmes éoliens. Toutefois, les aspects techniques et économiques sur ce choix doivent être encore évalués, en analysant et en comparant la solution globale du système dans le même cadre de recherche avec d'autres solutions alternatives. / This thesis addresses the modeling, design and optimization with experimental validation of the Brushless Doubly-Fed Reluctance Machine (BDFRM) for wind power systems. The BDFRM is being considered as a viable alternative to the Doubly Fed Induction Machine (DFIG) in variable speed wind energy conversion systems. It keeps the cost advantages of the DFIG by allowing the use of a fractionally rated power converter and it has the advantage of reduced maintenance costs due to its brushless operation. A literature review shows that there is still a lack of researches to define a design procedure to make this machine widely used in general and in such application in particular. The main goal of this thesis is to contribute on mastering the BDFRM optimized design by proposing a methodological approach based on different modeling levels and on optimization. It discusses how optimization could be applied in all development stages with distinct objectives to be assessed. More precisely, it draws its attention on setting the optimization problem and on the iterative solution of a constrained inputs/outputs problem by using a deterministic algorithm coupled to analytical-based modeling levels. The activities performed during this thesis can be divided in five main topics. The first refers to the study of the BDFRM and its operating principles in the context of wind power. The second discusses the BDFRM electromagnetic modeling aspects using different approaches. Two optimization-oriented models have been developed: the Semi-Analytical Model (SAM) and the Multi-Static Reluctance Network model (MSRN). The implementation of the models focusing on deterministic optimization and their verification through simulations using Finite Element Analysis (FEA) are considered the third topic. It can be concluded from the simulation results that the SAM has a limited accuracy level and it is recommended to be used in early design stages, where the designer is most interested in fast computation times to test many design variation than in obtaining the results with the highest possible accuracy. The MSRN, on the contrary, presents remarkably precise results when compared to FEA, yielding a very interesting trade-off among accuracy and computation time. This thesis has also allowed to specify and realize a BDFRM prototype using an optimization approach, presented in the fourth part. Then, the experimental data obtained from the prototype has been confronted to the simulation results to validate the models, focusing on the investigation of the flux modulation process by the reluctance rotor, especially the mutual inductance among the windings. Although the results were in a sense satisfactory to validate the models, there have been differences that demanded further investigation. A discussion on the most likely hypothesis for that has been performed, indicating the significant role of the manufacturing process on machine performance. The fifth topic explores through a case study the use of the proposed BDFRM design procedure for wind power applications. As a general conclusion, it can be stated that the BDFRM is potentially a good candidate to be used in wind power systems. However, the technical and economic aspects on this choice must be still assessed, analyzing and comparing the overall system solution of distinct topologies within the same framework. / Esta tese aborda a modelagem, o projeto e a otimização, com validaçãoexperimental, de máquinas de relutância duplamente alimentadas sem escovas (BDFRM)para sistemas de geração de energia eólica.A BDFRM é considerada como uma alternativa viável para o gerador de indução duplamentealimentado (DFIG) em sistemas de geração de energia eólica com variação develocidade. Ela mantém as vantagens de custo da solução com o DFIG, permitindo autilização de um conversor de frequência de potência nominal reduzida, e tem a vantagemadicional de custos de manutenção mais baixos devido a sua operação sem escovas. Umarevisão da literatura evidencia que ainda há uma necessidade de pesquisas na área parade_nir um procedimento de projeto desta máquina para torná-la amplamente utilizada emaplicações em geral e, em particular, para geração eólica.O objetivo principal desta tese é de contribuir para o domínio de técnicas de projetootimizado para a BDFRM através da proposição de uma metodologia baseada em diferentesníveis de modelagem e em otimização. Discute-se como técnicas de otimização podem seraplicadas em todas as fases de desenvolvimento com objetivos distintos. Especi_camente,a metodologia proposta se concentra na de_nição e na solução iterativa de problemas deotimização com restrições nas saídas utilizando um algoritmo determinístico acoplado amodelos semi-analíticos de diferentes níveis.As atividades realizadas durante esta tese podem ser divididas em cinco tópicos principais.O primeiro refere-se ao estudo da BDFRM e seu princípio de funcionamento no contextode geração de energia eólica. O segundo trata dos aspectos de modelagem eletromagnética da BDFRM utilizando diferentes abordagens. Dois modelos orientados à otimizaçãoforam desenvolvidos: o modelo semi-analítico (SAM) e o modelo multi-estático de redes derelutâncias (MSRN). A implementação dos modelos com foco na otimização e a veri_caçãodeles através de simulações com o método de elementos _nitos (FEA) são consideradas aterceira parte. Pode-se concluir, a partir dos resultados de simulação, que o SAM tem umaprecisão limitada e é recomendado para ser utilizado em estágios iniciais de projeto, emque o projetista está mais interessado em cálculos rápidos para testar diversas variações deprojeto do que na obtenção de resultados com a maior precisão possível. O MSRN, ao contrário, apresenta resultados precisos quando comparado aos obtidos com o FEA, resultandonum interessante custo-benefício entre precisão e tempo de cálculo. Nesta tese, fabricou-setambém um protótipo da BDFRM, o qual foi especi_cado utilizando-se otimização e osdetalhes sobre ele são introduzidos na quarta parte. Os dados experimentais obtidos com oprotótipo foram confrontados com os resultados de simulação para validação dos modelos,focando-se na investigação do processo de modulação de _uxo pelo rotor relutância, especialmentea indutância mútua entre os enrolamentos. Embora os resultados obtidos sejamsatisfatórios para validar os modelos, encontraram-se diferenças que exigiram uma investigação mais detalhada. As hipóteses mais prováveis foram investigadas e as conclusõesindicam o papel determinante do processo de fabricação no desempenho da máquina. Oquinto tópico explora através de um estudo de caso a utilização do procedimento de projetoproposto da BDFRM para aplicações de geração de energia eólica.Como conclusão geral, pode-se a_rmar que a BDFRM é potencialmente uma boa candidatapara ser utilizada em sistemas de geração de energia eólica. Contudo, aspectostécnicos e econômicos sobre essa escolha devem ainda ser avaliados, comparando-se asdiferentes topologias existentes sob o mesmo enfoque metodológico.

>Magister Scientiae - MSc / IP multicast is an efficient mechanism for simultaneously transmitting bulk data to multiple receivers. Many applications can benefit from multicast, such as audio and videoconferencing, multi-player games, multimedia broadcasting, distance education, and data replication. For either technical or policy reasons, IP multicast still has not yet been deployed in today’s Internet. Congestion is one of the most important issues impeding the development and deployment of IP multicast and multicast applications.

Orientador: João Sinézio de Carvalho Campos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-27T19:06:13Z (GMT). No. of bitstreams: 1 Conceicao_RafaelNovaesda_M.pdf: 10111957 bytes, checksum: 9168b5514bd29d6ead99888af5052aab (MD5) Previous issue date: 2015 / Resumo: É bem conhecida a necessidade de energia elétrica para o bem estar e desenvolvimento tecnológico da população em nosso planeta. Ao lado dos avanços científicos de novas tecnologias para geração, existem interesses na melhoria do transporte da energia. Dentre estes se encontram materiais para isolação elétrica de barras estatóricas, quer sejam para melhorar a isolação ou mesmo para reduzir custos. Assim, o presente trabalho visa apresentar resultados da aplicação de uma nova resina epóxi bisfenólica (DGEBF) (RN) à base de nanopartículas de sílica e comparar suas propriedades com a resina epóxi bisfenólica (DGEBA) (RE), atualmente utilizada para a isolação de hidrogeradores. Neste sentido, fabricaram-se protótipos de barras estatóricas, destinadas a hidrogeradores, sendo as resinas impregnadas em sistema VPI (Vácuo-Pressão-Impregnação) e avaliaram-se as propriedades físico-químicas pelas técnicas de viscosimetria, TGA, DSC, MEV e EDS. As propriedades elétricas foram avaliadas pelas técnicas de fator de dissipação (tan delta), descargas parciais, envelhecimento acelerado (VET) e tensão de ruptura. Dentre os resultados das propriedades físico-químicas pode-se comprovar um aumento inicial de três vezes o valor de viscosidade para resina RN em comparação com RE. Entretanto, não houve detrimento das características dielétricas em função da viscosidade, o que foi comprovado através dos resultados de tan delta e VET. Obteve-se um valor de Tg de 116°C e 145°C para RN e RE, respectivamente, o que limitaria a aplicação da resina em geradores por estar abaixo da temperatura de operação. Dentre os resultados dos testes elétricos para as resinas observou-se que: (i) o fator de dissipação e de envelhecimento são praticamente os mesmos para ambas as resinas; (ii) o valor de tip-up resultaram em 0,014 % para RE e 0,020 % para a resina RN, sendo que a norma EN 50209 exige que seja inferior a 0,25% e (iii) a estimativa do tempo de vida útil obtida foi de cerca de 40 anos para os dois tipos de resina, o que é aplicável para maioria dos enrolamentos em operação. Neste sentido sugere-se que a resina RN pode ser uma boa alternativa a resina RE, com um desempenho elétrico equivalente, desde que ajustadas suas condições de processamento e temperatura de aplicação / Abstract: It is well know the demand of electrical energy for the wellbeing and technological development of the population in our planet. Among the scientific development of new technologies for generation, are interests to optimize the energy transport. Among them are materials for electrical insulation of stator bars, whether for improving the insulation or even to reduce the costs. Therefore, the present work aim to present the results of the employment of a new bisphenolic epoxy resin (DGEBF) (RN) containing silica nanoparticles and compare its properties with the bisphenolic epoxy resin (DGEBA) (RE) currently used for the insulation of hydrogenerators. In this context, it was manufactured prototype stator bars, designed for hydrogenerators, being the resins impregnated through VPI (Vacuum-Pressure-Impregnation) system and their physicochemical properties evaluated with the technics of viscosimetry, TGA, DSC, MEV and EDS. The electrical properties were evaluated with the tests of dissipation factor (tan delta), partial discharges, voltage endurance test (VET) and breakdown. Among the results of the physicochemical properties it was possible to verify an initial increase of three times the value of viscosity for RN resin compared to RE. However there was no detriment of the dielectric characteristics depending on the viscosity, what was proven with the results of dissipation factor and VET. It was obtained a value of Tg of 116°C and 145°C for RN and RE respectively, what could limit its employment for hydrogenerators as being below the operational temperature. Among the results of electrical tests for the resins it was observed that: (i) the dissipation factor and VET are practically the same for both resins; (ii) the tip-up value resulted in 0,014% for RE and 0,020% for RN, being required lower than 0,25% according to the norm EN 50209 and (iii) the estimating lifecycle was approximately 40 years for both types of resin, what is applicable for most windings under operation. In this context it is suggested that the RN resin can be a good alternative for RE resin with an equivalent performance once the process conditions and employment temperature are adjusted / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

No description available.

Reliability Centred Maintenance (RCM) started a new chapter in the history of preventive maintenance strategy setting. It was now possible to develop a scientifically based, highly successful maintenance program for complex systems. It developed as a result of the reliability problems and cost of maintenance of aircraft during the late 50’s and early 60’s. The result was a methodology called MSG-1, followed by the improved MSG-2. When MSG-2 was used contractually for the United States Department of Defence, it led to the present definition of RCM. In academic circles there developed a growing dissatisfaction with the technique [Pintelon et al (1999], of which part stems from watering down its scientific basis to make RCM more marketable [Moubray (2000)], while at least part is based on perceived inherent scientific weaknesses in the methodology itself. This thesis, in setting out to solve these limitations, makes several important contributions to the RCM methodology. The first of these is a method of concentrating the RCM analysis effort on the most important failure modes encountered by the organisation. Secondly, it introduces a Quality Improvement task in the RCM task selection tree, based on a limitation identified by Harris (1985). The third contribution is the addition of a formal task packaging methodology, following Gits (1984). The thesisalso combines the use of RCM for the most important failure modes with conventional maintenance tasks for the remaining failure modes, to form a total methodology for the typical industrial concern. It furthermore introduces the application of sound management principles in the implementation of RCM and lastly, blends concepts from different RCM authors, together with the innovations listed above, into one logical whole. In summary, the proposed revised methodology can play a very important part to achieve the goal of World Class manufacturing standards, including ensuring that the organisation’s maintenance effort is as proactive as possible. D13/4/90 / Thesis (PhD (Industrial Engineering))--University of Pretoria, 2002. / Industrial and Systems Engineering / unrestricted

During the past three years, a research project has been carried out in the Department of Mechanical Engineering at UCT, directed at developing a system to accurately reproduce three-dimensional (3D), sculptured surfaces on a three axis computer numerically controlled (CNC) milling machine. Sculptured surfaces are surfaces that cannot easily be represented mathematically. The project was divided into two parts: the development of an automatic noncontact 3D measuring system, and the development of a milling system capable of machining 30 sculptured surfaces (Back, 1988). The immediate need for such a system exists for the manufacture of medical prostheses. The writer undertook to investigate the measurement system, .with the objective to develop a non-contact measuring system that can be used to 'map' a sculptured surface so that it can be represented by a set of XYZ coordinates in the form required by the milling system developed by Back (1988). This thesis describes the development of a PC-based near-realtime photogrammetry system (PHOENICS) for surf ace capture. The topic is introduced by describing photogrammetric principles as used for non-contact measurements of objects. A number of different algorithms for image target detection, centering and matching is investigated. The approach to image matching adopted was the projection of a regular grid onto the surface with subsequent matching of conjugate grid intersections. A general algorithm which automatically detects crosses on a line and finds their accurate centres was developed. This algorithm was then extended from finding the crosses on a line, to finding all the intersection points of a grid. The algorithms were programmed in TRUE BASIC and specifically adapted for use with PHOENICS as an object point matching tool. The non-contact surface measuring technique which was developed was used in conjunction with the milling system developed by Back (1988) to replicate a test object. This test proved that the combined system is suitable for the manufacture of sculptured surf aces. The accuracy requirements for the manufacture of medical prostheses can be achieved with the combined measuring and milling system. At an object-to-camera distance of 0.5 m, points on a surface can be measured with an accuracy of approximately 0.3 mm at an interval of 5 mm. This corresponds to a relative accuracy of 1:1600. Back (1988) reported an average undercutting error of 0.46 mm for the milling system. This combines to an uncertainty of 0.55 mm. Finally, the limitations of PHOENICS at its prototype stage as a surface measuring tool are discussed, in particular the factors influencing the system's accuracy. PHOENICS is an ongoing project and the thesis is concluded by some recommendations for further research work.

The purpose of master’s thesis is to project virtualization solution together with replication of the servers. Thesis is divided into the three parts and that it theoretical, analytical and projection part. In analytical part there are basic information about virtualization technologies, in analytical part there is analysis of the present status of the company and mainly about status of the IT infrastructure and in the end projection part there is realization of the virtualization solution from choosing the right type of cluster to choosing hardware solution.

This master thesis focuses on the issue of tangible fixed assets management in the company HP spol. s r.o. which manufactures plastic bags and various technical parts. This thesis is based on the current state of the company and with attention to key areas such as care of the tangible fixed assets, organization and operation maintenance. The aim of the company analysis is to identify weaknesses and their resulting opportunities. In the next section are presented solutions to problems which were identified by analysis. Economic evaluation of the proposals with their benefits and timetable is carried out in conclusion of the thesis.

This study is concerned with the design of vehicle structures through the use of Fatigue Equivalent Static Loads (FESL). A large percentage of failures of mechanical structures can be attributed to fatigue. Furthermore, it is also generally accepted that defective structural design is mostly caused by insufficient knowledge of the input loading. The fatigue loads experienced by vehicle structures are especially difficult to quantify. In the current competitive markets, it is essential to use a pro-active, timely and cost effective process to solve fatigue related problems. The heart of the FESL methodology is the ability to condense a large amount of input load data into a single fatigue load. This is achieved by calculating the damage of the measurements and converting it to an equivalent stress, through the use of a calibration matrix obtained from a unit-load finite element analysis. A Fatigue Equivalent Static Load can now be determined, and the vehicle structure can be evaluated for durability. / Dissertation (M Eng (Mechanical Engineering))--University of Pretoria, 2003. / Mechanical and Aeronautical Engineering / unrestricted