Cementitious Porous Material Applied to Precision Aerostatics Bearings

Abstract

The use of porous materials as restrictor in aerostatic bearings provides many advantages over conventional restrictors, such as small variation of temperature, high damping, high operational speeds, limited wear and capacity to support radial, axial, and combined loads, being considered important features for precision machines and instruments. This work evaluates the load carrying capacity for different air gaps and pressures of thrust porous bearing made with cementitious composites. The cementitious composites consisted of Portland cement and monomodal silica particles (44 μm) were fabricated via uniaxial cold-pressing (10 MPa). The load capacity was determined for different air pressures, such as 3, 4, 5 and 6 bar. The air gap was measured using pneumatic transducers. A pneumatic instability was observed when the air pressure level increased from 3 to 6 bar. A similar loading capacity, for bearing gaps between 7 and 30 μm, was achieved in comparison to hot-pressed porous alumina found in the literature. In addition, the cementitious porous bearing provided a superior loading capacity for gaps higher than 10 μm when compared to graphite porous bearing found in the literature. The results revealed the cementitious composites are promising materials for porous restrictor in aerostatic thrust bearings.