Effects of Geometric Defects in Journals on Bearing Performance

With increased engine output and lower fuel consumption, the operating conditions for engine bearings are becoming more rigorous. With this trend, bearing damage caused by geometric defects in journals occurs. In this paper, the hourglass, barrel and double-barrel shaped journals have been investigated as representative defects in axial geometry. Employing calculations based on the hydrodynamic lubrication theory and experiment, the effects of these axial geometries on bearing performance have been investigated. It was found that the deterioration of precision of these journals invites reduction of oil film thickness and a rise in oil film pressure, and seriously affects seizure and fatigue resistance.