Capes; Fundação Araucária / Mancais de deslizamento são elementos de máquinas que detém considerável importância, pois são empregados em diversos ramos da indústria. Estes componentes operam pela interação entre ligas de metal patente, depositadas na sua superfície interior, com o eixo de rotação. Ligas de metal patente são basicamente ligas a base de estanho, que oferecem vantagens pelo baixo coeficiente de atrito, alta ductilidade e boa tenacidade, que ao longo da operação, absorvem a energia gerada pelo rolamento do eixo, atribuindo ao sistema maior vida útil e confiabilidade. Neste trabalho foram avaliadas as alterações microestruturais e propriedades mecânicas de uma liga de metal patente depositada por diferentes processos de aspersão térmica, em relação aos revestimentos de metal patente depositados por métodos convencionais. O objetivo desta pesquisa foi de avaliar as modificações microestruturais, propriedades mecânicas e tribológicas de revestimentos depositados por diferentes processos de deposição por aspersão térmica. As deposições, por aspersão térmica, foram realizadas por dois processos distintos, sendo estes: arco elétrico, Arc Spray Process – ASP e aspersão a chama, Flame Spray – FS. Analisou-se a influência do processo de deposição sobre a microestrutura, formação de poros, morfologia, microdureza, aderência do revestimento, bem como o comportamento tribológico dos revestimentos. Os processos de aspersão promoveram revestimentos com maior teor de poros, entretanto ainda aceitáveis por norma. Observou-se que os processos de aspersão térmica originaram revestimentos com menor formação de precipitados que os métodos convencionais, todavia com maior formação de precipitados CuSn, em função da temperatura e das taxas de resfriamento alcançadas, o que eleva a tenacidade da liga, sem alterar significativamente sua dureza. O comportamento tribológico dos revestimentos obtidos por aspersão térmica indicaram níveis de desgastes inferiores, porém com maior coeficiente de atrito. Observou-se uma maior estabilidade do coeficiente de atrito e menor dispersão ao longo do ensaio tribológico, o que garante maior estabilidade dinâmica do revestimento frente ao deslizamento. / Sliding bearings are mechanical elements which hold considerably large importance, for their use on many branches of industry. These elements operate via interaction between Babbitt metals, deposited on the inner surface, with the rotating axle. Babbitt metals are basically tin or lead-based alloys, which convey the applicational advantages of low friction coefficient, high ductility, and good toughness, that during the operation, absorb the energy generated by the axle bearing, as well as the shock waves resultant of the system fluctuations, giving the system longer lifespan and reliability. This work will make the characterization of a Babbitt metal alloy deposited by different thermal spray processes, comparing the same alloy deposited by conventional methods, with the goal of evaluating how the resulting microstructure and mechanical properties of the deposition processes will be affected by the different thermal spraying methods. The chemical composition of the coatings and the micro hardness will also be evaluated. Additionally, factors such as adherence and tribological behavior of the coatings will be analyzed. Thus allowing us to compare the microstructures, mechanical and tribological properties with the conventional coatings methods. It was observed that the thermal spray processes resulted in coatings with lower precipitate formation than conventional methods, however with a higher formation of CuSn precipitates, as a function of the temperature and the cooling rates achieved, which increases the bond strength without changing hardness. The tribological behavior of the coatings obtained by thermal spraying showed lower wear level, but the coefficient of friction observed is higher, compared with the Babbit alloy deposited by conventional process. It was observed that coefficient of friction was more stable and less dispersion throughout the tribological test, which greater dynamic stability to the coating for sleeve.

The objective of this research is to develop a bearing fault detection scheme for electric machines via stator current. A new method, called the stator current noise cancellation method, is proposed to separate bearing fault-related components in the stator current. This method is based on the concept of viewing all bearing-unrelated components as noise and defining the bearing detection problem as a low signal-to-noise ratio (SNR) problem. In this method, a noise cancellation algorithm based on Wiener filtering is employed to solve the problem. Furthermore, a statistical method is proposed to process the data of noise-cancelled stator current, which enables bearing conditions to be evaluated solely based on stator current measurements. A detailed theoretical analysis of the proposed methods is presented. Several online tests are also performed in this research to validate the proposed methods. It is shown in this work that a bearing fault can be detected by measuring the variation of the RMS of noise-cancelled stator current by using statistical methods such as the Statistical Process Control. In contrast to most existing current monitoring techniques, the detection methods proposed in this research are designed to detect generalized-roughness bearing faults. In addition, the information about machine parameters and bearing dimensions are not required in the implementation.

Orientador: Marco Lúcio Bittencourt / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-24T09:08:40Z (GMT). No. of bitstreams: 1 LimaeSilva_RafaelAugustode_M.pdf: 10555723 bytes, checksum: 1d037ebafbabc24e214c06ad76c5f54a (MD5) Previous issue date: 2013 / Resumo: O trabalho descreve o projeto mecânico convencional de uma biela automotiva de motor de combustão interna e apresenta uma metodologia alternativa baseada em métodos de otimização estrutural com o objetivo de reduzir a massa do componente. Para tal, é feita a descrição de todos os parâmetros de projeto assim como a definição de critérios de projeto. Em virtude da criticidade da aplicação selecionada, motor de ciclo Diesel utilizado em caminhões de trabalho pesado com picos de pressão de combustão de até 240 bar, a biela foi projetada sem bucha utilizando-se extensivamente os métodos numéricos. O Método dos Elementos Finitos foi aplicado para cálculo de tensões, deslocamentos, pressões de contato, flambagem, fadiga e para a síntese modal de componentes utilizados na análise dinâmica de multicorpos com mancais elasto-hidrodinâmicos. Dois modelos de fadiga dos materiais foram estudados: o modelo americano baseado no diagrama de Goodman e tensões principais e o modelo alemão baseado no diagrama de Haigh e efeito do gradiente de tensões multiaxiais; dos quais concluiu-se que o modelo americano é suficiente para o projeto da biela ao passo que o modelo alemão traz oportunidades adicionais de redução de massa. A otimização topológica, otimização de forma e análise de sensibilidade permitiram a obtenção de uma biela 210g (3\%) mais leve e com melhor desempenho dos mancais hidrodinâmicos. Finalmente, concluiu-se que o Método da Otimização Topológica apresenta oportunidades interessantes aos projetistas na fase de conceituação de produtos como alternativa aos desenhos convencionais, no entanto, demanda esforço adicional para o atendimento de todos os critérios de projeto do componente / Abstract: The present work consists of the conventional mechanical design description of an internal combustion engine connecting rod and also the proposal of an alternative methodology based on optimization methods with the objective of reducing the component mass. Therefore, it is performed a detailed view of all design parameters as well as the definition of design criteria. Because of the critical application selected, Diesel engine of heavy duty truck with combustion pressure reaching up to 240bar, the connecting rod was designed without bushing and with extensive use of numerical methods. The Finite Element Method was applied to assess stresses, displacements, contact pressures, buckling, fatigue and to perform the Component Modal Synthesis for multi-body dynamics simulation with elasto-hydrodynamic bearings. Two fatigue models were studied: the American model based on Goodman's diagram and principal stresses and the German model based on Haigh's diagram and multiaxial stress gradient effect; from which it was concluded that the American model is enough to design the connecting rod, while the German model presents additional weight reduction opportunities. The topology optimization, shape optimization and sensitivity analysis enabled a 210g (3\%) lighter connecting rod with improved bearings performance. Finally, it was concluded that the Topology Optimization Method presents good opportunities for the design engineers in the conceptual phases of product development with alternatives to the conventional designs. However, additional effort is necessary to fit the concept into all design criteria / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Indiana University-Purdue University Indianapolis (IUPUI) / This thesis concentrates on the study of hybrid gas journal bearings (bearings with externally pressurized mass addition). It differs from most work in that it goes back to “basics” to explore the hydrodynamic phenomena in the bearing gap. The thesis compares geometrically identical bearings with 2 configurations of external pressurization, porous liners where mass-addition compensation is varied by varying the liner’s permeability, and bushings with 2 rows of 6 feedholes where the mass-addition compensation is varied by the feedhole diameter. Experimentally, prototype bearings with mass-addition compensation that spans 2 orders of magnitude with differing clearances are built and their aerostatic properties and mass addition characteristics are thoroughly tested. The fundamental equations for compressible, laminar, Poiseuille flow are used to suggest how the mass flow “compensation” should be mathematically modeled. This is back-checked against the experimental mass flow measurements and is used to determine a mass-addition compensation parameter (called Kmeas) for each prototype bushing. In so doing, the methodology of modeling and measuring the mass addition in a hybrid gas bearing is re-examined and an innovative, practical, and simple method is found that makes it possible to make an “apples-to-apples” comparison between different configurations of external pressurization. This mass addition model is used in conjunction with the Reynolds equation to perform theory-based numerical analysis of virtual hybrid gas journal bearings (CFD experiments). The first CFD experiments performed use virtual bearings modeled to be identical to the experimental prototypes and replicate the experimental work. The results are compared and the CFD model is validated. The ontological significance of appropriate dimensionless similitude parameters is re-examined and a, previously lacking, complete set of similitude factors is found for hybrid bearings. A new practical method is developed to study in unprecedented detail the aerostatic component of the hybrid bearings. It is used to definitively compare the feedhole bearings to the porous liner bearings. The hydrostatic bearing efficiency (HBE) is defined and it is determined that the maximum achievable hydrostatic bearing efficiency (MAHBE) is determined solely by the bearing’s mass addition configuration. The MAHBE of the porous liner bearings is determined to be over 5 times that of the feedhole bearings. The method also presents a means to tune the Kmeas to the clearance to achieve the MAHBE as well as giving a complete mapping of the hitherto misunderstood complex shapes of aerostatic load versus radial deflection curves. This method also rediscovers the obscure phenomenon of static instability which is called in this thesis the “near surface effect” and appears to be the first work to present a practical method to predict the range of static instability and quantify its resultant stiffness fall-off. It determines that porous liner type bearings are not subject to the phenomenon which appears for feedhole type bearings when the clearance exceeds a critical value relative to its mass-addition compensation. The standing pressure waves of hydrostatic and hybrid bearings with the 2 configurations of external pressurization as well as a geometrically identical hydrodynamic bearing are studied in detail under the methodology of the “CFD microscope”. This method is used to characterize and identify the development, growth, and movement of the pressure wave extrema with increased hydrodynamic action (either increasing speed or increasing eccentricity). This method is also used to determine the “cause” of the “near surface effect”. A gedanken experiment is performed based on these results which indicates that a bearing with a “stronger aerostatic strength” component should be more stable than one with a low aerostatic strength component. Numerical instability “speed limits” are found that are also related to the hydrostatic strength of the bearing. The local conditions in the standing waves are characterized in terms of their local Mach number, Knudsen number, Reynolds number, and Taylor Number. It is concluded that low eccentricity bearing whirl can be attributed to the off load-line orientation of the bearing load force caused by the overlay of the hydrodynamic bearing standing wave onto the hydrostatic bearing wave of the hybrid bearing, whereas it is hypothesized that aperiodic and random self-excited vibration which occurs at high eccentricity, as reported in the literature, is probably due to shock waves, turbulence, near surface effect, and slip at local areas of the standing wave.