Jung S., Lee J., Lee S., Ji H., Choi H.

Recently externally pressurized circular porous thrust air bearings have been widely used in many industrial applications because of their advantages. A lot of researches have been done in order to investigate the dynamic characteristics of those aerostatic porous bearing, most of them used analytical approaches and only a few used experimental approaches. However, in the most previous experimental approaches the aerostatic porous bearing has been fixed and only the mass supported by the bearing is allowed to move vertically. The dynamic stiffness obtained by those experimental setups may be different with the real case where the mass and the bearing move(vibrate) together in vertical direction. The reason that the dynamic stiffness for vertically moving aerostatic bearing may be different with the fixed bearing case is that the flow characteristics in the bearing clearance between these two cases may be different, and the dynamic stiffness of the aerostatic bearing can be determined by the flow characteristics in the clearance of the bearing. In this paper, the dynamic characteristics of the vertically moving aerostatic circular porous air bearings are investigated by the experimental approach. A special feature of the experimental apparatus that was designed for this study is that the mass supported by the aerostatic air bearing and the bearing itself can move vertically together, which is more realistic case in most industrial applications. In addition, three different guiding surface materials (granite, lapped steel, and ceramic) for air bearings are also used in order to investigate the effect of the guide materials on the bearing stiffness. The experimental results show that the vertically moving externally pressurized porous air bearing has less dynamic stiffness than the fixed bearing case, and it seems to be very important results for design engineers in industry.