R

pp. 48-71

A mathematical model was developed for plane aerostatic bearings with porous deboosters; this model allows to determine the main performance characteristics such as damping stiffness of load capacity in linear and angular directions and a consumable air flow. Experimental determination of permeability inhomogeneity for porous graphite deboosters was conducted. Influence of permeability variation on characteristics of an aerostatic bearing was evaluated by means of calculations with maximum and minimum values of the permeability index. This influence appeared to be smaller with a constant aerostatic gap than with constant load. On the basis of the obtained results, recommendations on manufacturing plane aerostatic bearings were given.

The authors present a model for calculation of a spherical aerostatic bearing with porous boost limiters based on the Reynolds equation of gas lubrication with all fixed summands. The problem is solved in the program Comsol 3.5a by the finite element method. The state of the spindle was determined by the displacement vector, translational and angular velocity. Pressure distribution, support forces and moments, as well as air flow are also calculated. The presented model is used to estimate simplified solutions obtained under different assumptions at designing precision spindles.

The authors proposed a simplified segment-model of spherical aerostatic bearings which allows to determine static and dynamic behaviour of bearings. The model is based on two physical assumptions: the number of estimated segments is considered large, and the speed of tangential bearing surfaces is considered negligibly small. Bearing reactions are estimated on the basis of a series of preliminary calculations of air pressure in a separate segment field. The pressure field estimation is performed with the finite-element method in MATLAB program in a nonlinear formulation. The proposed model was tested on spherical aerostatic bearings with porous boost limiters developed for the high-precision nonferrous metal-turning work spindle. The segments number influence on accuracy of load characteristics is estimated.