Identification of dynamic properties of radial air-foil bearings

Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost “top foil” layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. Air-foil bearings are currently used in many commercial applications, both terrestrial and aerospace. Air-foil bearings provide a means to eliminate the oil system leading to reduce weight and enhanced temperature capability. Regardless of the application of the air-foil bearings, the identification of the dynamic characteristics is important for successful design practice. In the present work, stiffness and damping of radial air-foil bearings are indentified in the light of experimental results. Due to the initial high torque requirement of the air-foil bearing, the experimental setup using single air-foil bearing is proposed instead of standard two-foil bearing setups. Experiments are carried out at maximum speed of 60,000 rpm. Sub-structuring approach is used for identification of stiffness and damping properties of the air-foil bearings. The results have shown that the developed experimental procedure is able to indentify the stiffness and damping properties of radial air-foil bearings accurately.