On the modeling of levitation force for ultrasonic journal bearings actuated by piezoelectric transducers

Different from conventional hydrostatic or hydrodynamic journal bearings, an ultrasonic journal bearing provides carrying force by air squeeze film generated by high-frequency vibration of bearing bush surfaces. Detailed investigation indicates that studies on levitating force modeling based on fluid dynamics for ultrasonic journal bearings are rarely conducted, and the existing theoretical models generally neglect some significant contributors to levitating force such as gas inertia, surface topography, rarefaction effect, or boundary effect. A modified Reynolds-type equation considering these factors is put forward in this study to predict the ultrasonic journal bearing’s carrying capacity. The numerical solving results can interpret the experimental data well. The proposed model will provide theoretical reference for the design of ultrasonic journal bearings.