Theoretical Analysis of Spherical Bearings Lubricated with Greases

Abstract

The paper presents theoretical researches concerning the spherical bearings lubricated with greases, in rheostatic conditions: high loads and low velocities. This type of bearing is very appropriate for modelling the human joints (hip, knee), spherical joints from automotive industry (pivots, connecting rods) or special joints from petroleum industry. Spherical bearings may be of the “fitted” type or the “clearance” type. The fitted type of nonflat bearing pad surface is lappedin to fit the runner. When it is operating, the fitted pad will have a varying film thickness across the pad sill, between the pad and the runner. Similarly, in the clearance type the film shape will be non-uniform across the pad sill. The variation in film thickness across the bearing pad, for nonflat pads, influences the resulting pressure distribution in the bearing pad and, hence, its load carrying capacity. In this paper, the pressure distribution and the load capacity are determined for “clearance” type bearings, for two different cases: complete spherical bearings and partial spherical bearings. It has been found that the eccentricity ratio influences the angular position of the maximum pressure, which becomes nearer to the minimum angle of the bearing, once with the increasing of the eccentricity ratio.