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COB453 CARREGAMENTO DINÂMICO DE MANCAIS RADIAIS COM CAVITAÇÃO DO FILME DE ÓLEO / DYNAMIC LOADING OF JOURNAL BEARINGS WITH OIL FILM CAVITATION

Evandro de Souza Santos

Schulz S. A. - Pesquisa e Desenvolvimento, Rua Dona Francisca 6901 - Distrito Industrial

89219-000 Joinville, SC - E-mail: schulz@netville.com.br

Alvaro Toubes Prata

Departamento de Engenharia Mecânica, Universidade Federal de Santa Catarina

88040-900 Florianópolis, SC - E-mail: prata@nrva.ufsc.br

Hydrodynamic lubrication of journal bearing is governed by the Reynolds equation. The main difficulty in using Reynolds equation resides in the precise determination of the edge or the angular position after which the oil cavitates and starts to flow into a series of streamers. One of the objectives of the present work is to revise and compare some of the numerical algorithms encountered in the open literature to deal with the cavitation phenomena. Emphasis is also placed on selection of the coordinates system used to analyze the problem. Usually the hydrodynamic lubrication problems have been studied based on Reynolds equation referred to a rotating coordinates system where one of the coordinates is coincident with the centerline of the journal bearing. Here, the integration of Reynolds equation is performed with respect to an inertial coordinates system, and this is a novelty. The numerical results were obtained from both static and dynamic loading under conservative and non conservative boundary condition applied to the cavitation front. The Reynolds equation in fixed coordinates system performed well, and the Elrod Algorithm proved to be the most effective method for dynamic loading calculations.

Keywords: Cavitation in bearings, lubrication, dynamic loading, Reynolds equation in fixed coordinates system.

Cavitação, lubrificação, carregamento dinâmico, equação de Reynolds em sistema de coordenadas fixo.

COB477 APLICAÇÃO DE FERRAMENTAS COMPUTACIONAIS NO DESENVOLVIMENTO DE PROGRAMAS DIDÁTICOS PARA PROJETO DE EIXOS/ APLICATION OF COMPUTATIONAL METHODS TO THE DEVELOPMENT OF DIDACTIC PROGRAMS FOR SHAFT DESIGN

Fabio T. Peggau Jacon & Katia Lucchesi Cavalca

Departamento de Projeto Mecânico - Faculdade de Engenharia Mecânica - UNICAMP

Caixa postal 6051 - CEP 13083-970 - Campinas, SP, Brasil - E-mail: katia@fem.unicamp.br

The main purpose of this work is to modernize the project of rotating machineryng, by the development of a computational code including the calculation procedures adopted in the design of these components, considering, however, its dynamical behaviour as a fundamental part of a rotating machine.

Keywords: Funções de Singularidade, Concentração de Tensões, Resistência à Fadiga, Projeto de Eixos, Deflexões, Velocidades Críticas. / Singularity Functions, Stress Concentration, Fatigue Resistance, Shaft Design, Deflection, Critical Speeds

COB1209 MANCAL RADIAL DE DESLIZAMENTO: DETERMINAÇÃO DE RAMOS DE SOLUÇÕES PERIÓDICAS E PONTOS DE BIFURCAÇÃO COMPLEXOS/RADIAL JOURNAL BEARING: PERIODIC BRANCHING AND HOPF BIFURCATION POINTS DETERMINATION

Mário César Ricci e Petrônio Noronha de Souza

Divisão de Mecânica Espacial e Controle, DMC/INPE CEP 12201-970 - São José dos Campos, Brasil - E-mail: mcr@dem.inpe.br

In the mechanical engineering moving system’s field the radial journal bearing is one of the great interest. It consists of a circular inner cylinder (the rotor) that turns inside a hollow cylinder of slightly larger radius (the stator). The cavity between the cylinders is filled with a lubricant and any load carried by the rotor must be supported by the fluid forces exerted by the lubricant on the rotor. The system can be described by a set of four first order’s nonlinear ordinary differential equations which the fluid forces are approximate solution of partial differential equations and shows a great richness of behavior same at the simplest case of cavitation model, autonomous, unforced and balanced-mass rotor system. Rigorous geometrical constraints are impose on the moving of the rotor’s center about stator’s center to avoid the contact between them. Otherwise, the contact could well result in bearing failure. Starting from the Reynolds approximation for the long bearing the paper uses numerical methods for bifurcation problems to calculate Hopf bifurcation points and numerical methods of continuation to obtain branching of periodic orbits that emanate from stationary solutions. The paper also shows the amplitude and frequency of periodic solutions as a function of rotor’s angular velocity for the low, medium and high loads.

Keywords: Numerical methods; Hopf bifurcation; radial journal bearing; mancal radial hidrodinâmico; bifurcação.

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