ELASTOHYDROSTATIC LUBRICATION OF JOURNAL BEARING OPERATING WITH NON-NEWTONIAN LUBRICANTS

Abstract

Hydrostatic journal bearings are successfully used in several applications involving heavy loads, zero or low speeds and low eccentricity ratios. These bearings are extensively used in the machine tools owing to their excellent characteristics in respect of high fluid film stiffness, low friction, good vibration damping characteristics and smooth relative motion even at low rotational speeds. The literature available in this area is abundant for the case of Newtonian lubricants. In order to meet the specific requirements of many engineering applications, lubricants are mixed with additives and this results into non-Newtonian behaviour. The literature concerning the hydrostatic/hybrid journal bearings operating with non-Newtonian lubricants is scant and therefore, the need is felt to study the performance characteristics of compensated journal bearing with non-Newtonian lubricants. The polymer-thickened oils behave as pseudoplastic or dilatant fluids. The viscosity of such lubricants loaded with additives is not constant and usually has some non-linear relations between shear stress and shear strain rates. This can be represented by different non-Newtonian models. Most of the non-Newtonian lubricants follow the Cubic Shear Stress Law and Shear Strain Power Law models. The prime objective of this investigation is to study the effects of non-linear behaviour df non-Newtonian lubricants on the performance of recessed / non-recessed hydrostatic/hybrid journal bearing systems using different flow control devices such as capillary, orifice, constant flow valve and slot-entry restrictors. The performance characteristics of the journal bearing system operating with non-Newtonian lubricants are evaluated in more realistic conditions envisaging deformation of the bearing liner. The computed characteristics of the flexible bearing supported on non-Newtonian film are compared with those obtained for a rigid bearing supported on Newtonian lubricant film.