Damping in Vibration Transfer through Deep-Groove Ball Bearings

Abstract

Damping characteristics in vibration transfer through deep-groove ball bearings are precisely measured using single-bearing structure (equivalent to the 6200 type) and compliance transfer function resulting from impulse hammering the bearing. To eliminate unnecessary effects caused by bearing setting and preloading, the single-bearing is specially fabricated to unite its inner ring and a shaft in one body, and also its outer ring and a rotor. This structure enables to be preloaded by an externally pressurized air bearing. Experimental damping ratios are found to range from 2-4%, and damping coefficients from 0.15-0.35 Ns/mm. Damping is found to decrease with increasing preload, and to be larger for larger clearance and for larger ball number. Decreases in damping owing to superimpose of the inclined mode and owing to increase in clearance lead to the fact that ball rolling motion rather than sliding motion is apt to decrease damping. Also, bearing rotational effect is found to be small, and grease hardly provides damping function during rotation.