The no-slip boundary condition is the foundation of traditional lubrication theory. It says that fluid adjacent to a solid boundary has zero velocity relative to that solid surface. For most practical applications the no-slip boundary condition is a good model for predicting fluid behavior. However, recent experimental research has found that for special engineered surfaces the no-slip boundary condition is not applicable. Measured velocity profiles suggest that slip is occurring at the interface. In the present study, it is found that judicious application of slip to a bearings surface can lead to improved bearing performance. The focus of this thesis is to analyze the effect an engineered slip/no-slip surface could have on hydrodynamic bearing performance. A heterogeneous pattern is applied to the bearing surface in which slip occurs in certain regions and is absent in others. Analysis is performed numerically for both plane pad slider bearings and journal bearings. The performance parameters evaluated for the bearings are load carrying capacity, side leakage rate and friction force. Fluid slip is assumed to occur according to the Navier relation and the effect of a critical value for slip onset is considered.

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Orientador: Katia Lucchesi Cavalca / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-06T20:31:32Z (GMT). No. of bitstreams: 1 GandaraNeto_Irineu_M.pdf: 5409150 bytes, checksum: 6e56e75e660311a97e894ef966472cd1 (MD5) Previous issue date: 2006 / Resumo: Neste trabalho foi desenvolvido um modelo matemático para mancais hidrodinâmicos com movimento oscilatório. Ao contrário dos mancais convencionais, o eixo não desenvolve um movimento completo de rotação dentro do mancal e passa a pertencer a uma nova classe definida como mancais hidrodinâmicos de movimento oscilatório. A motivação do trabalho veio da tribologia dos motores de combustão interna, na qual procurou-se estudar o problema de lubrificação do mancal que estabelece a conexão entre pistão e biela. Para análise do problema, assumiu-se o escoamento de um fluido viscoso com inércia desprezível dentro de uma folga inclinada formada pelas superfícies do eixo e mancal. A superfície interior é fixa enquanto a superfície exterior desenvolve um movimento oscilatório que resulta num escoamento combinado de Couette e Poiseuille. Usando a mesma abordagem da teoria da lubrificação de Reynolds e a solução na forma complexa conforme sugere o 2º problema de Stokes, as equações de conservação da massa e quantidade de movimento foram integradas analiticamente e forneceram os campos de velocidade, pressão e as forças hidrodinâmicas. Como resultado, pôde-se determinar a espessura do filme de óleo em função do tempo e da freqüência de oscilação que permitiu avaliar as condições de lubrificação do sistema / Abstract: In this work was developed a mathematical model for the hydrodynamic lubrication problem applied to bearings with oscillating motion. In contrast with common bearings, this type of bearing does not perform a complete rotation, belonging to a newly defined class: the bearings with oscillatory movement. The motivation lies in the tribology of internal combustion engines, specifically the lubrication problem at the bearing existing between the connecting rod and the piston pin. For the analysis of lubrication, a viscous fluid flow with negligible inertia inside a narrow gap formed by two surfaces was considered. The surfaces can be considered flat and are inclined to each other. The inner surface is fixed whereas the outer one performs an oscillating motion which generates a combined Couette-Poiseuille flow inside the gap. Using the same assumptions as in classical Reynolds' lubrication equation, the simplified mass and momentum conservation equations were analytically solved to determine the velocity and pressure distributions and hydrodynamic forces. As result it was possible to determine the oil film thickness as function of time and oscillating frequency that allowed to evaluate the lubrication conditions of the system / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Diploma thesis aims on mechanical design of new concept of Zetor UŘ III engine with displacement increase and solves calculations of main and pin hydrodynamic bearings of crankshaft. Creo 2 CAD software is used for preparing mechanical design of this new concept. For computation and analysis of hydrodynamic bearings multibody model of crankshaft mechanism is used with flexible FEM model of crankshaft for solving dynamics of mechanism and performing hydrodynamic analysis of bearings in FEV Virtual Engine. Results of this diploma thesis demonstrate the feasibility of new concept of engine and serve as a basis for next engineering tasks before realization of concept.