Signature Analysis of Roller Bearing Vibrations: Lubrication Effects

Abstract

This study investigates the vibration signature of roller bearings, induced by the surface irregularities of components, under various lubricating conditions. The bearing vibration is modelled as the output of the bearing assembly which is subjected to the excitations of surface irregularities through the oil-film. The oil-film acts as a spring between the roller and race. The stiffness of oil-film under different lubricating conditions is studied from the empirical equation of minimum oil-film thickness. It is shown that the vibration spectra of a normal roller bearing may have a pattern of equal frequency spacing distribution (EFSD) whose frequency information is similar to that of a damaged bearing. Under large loading and low running speed, the vibration energy is low if the lubricant viscosity is high. On the other hand, at high running speed, the vibration energy is high with high lubricant viscosity.