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Stability and Resonant Behaviour of a Rotor in Slide Bearings with Bingham Fluid As a Lubricant

Perek A.

Machine Dynamics Research

2012

Vol. 36, No. 2

84-94

The paper is concerned with a dynamic analysis of a rigid rotor supported in hydrodynamic bearings with rheological properties of the lubricant controlled by an external magnetic field. A fluid viscosity is an adaptive parameter, which controlled by the applied magnetic field, actively influence the dynamics of the rotor. Such an active lubricant can be identified with a magnetic fluid. Magnetic fluid as a suspension of sufficiently small ferro-particles can be treated as a homogenous substance, and used as a lubricating medium (Berkovsky et al., 1993, Miszczak and Wierzcholski). Due to magnetic interactions, it shows a non-Newtonian behaviour, which, with an appropriate synthesis of liquid, can be described by the Bingham model. In the following two effects of a magnetic fluid as a bearing lubricant are applied - increase of viscosity with the magnetic field and drop with the angular speed of the rotor. Both can be used to modify rotor dynamics to supply faster uplift to contactless rotation and desired resonant properties. Numerical simulations of nonlinear equations of the rotor transverse vibrations excited by unbalance forces show considerable influence of the magnetically controlled viscosity on the magnitude and position of the resonant zone. Magnetic field and shear rate- dependent effective lubricant viscosity influence the critical rotation speed of the rotor.

Modern large bearings with low wear rates and power consumption for cement and heavy industry

Hagenhoff M., Polonczyk K., Rodermund H.

Tribologia

2002

nr 5

1387-1399

Large heavy loaded plain bearings with low speed are used in many industrial fields. For many decades it was normally accepted that these bearings must work in the range of mixed friction with corresponding high power losses and short life time caused by wear, in spite of plentiful lubrication. Due to optimal bearing construction and material choise as well as using new lubricants with best flowability in a wide range of temperature it is possible today to reach life time values over 10 years.

W artykule przedstawiono możliwość podwyższenia trwałości wielkogabarytowych łożysk ślizgowych pracujących w ciężkich warunkach przemysłu cementowego z równoczesnym zmniejszeniem zużycia energii - dzięki poprawie warunków smarowania. Na podstawie analizy możliwości podwyższenia nośności wynikającej z zależności teoretycznych uznano, że właściwym sposobem jest stosowanie olejów mineralnych lub syntetycznych o stabilnej lepkości. Przedstawione rozważania zilustrowano przykładem obliczenia zmian lepkości oleju w łożysku rolki podporowej pieca obrotowego.