The effects of surface roughness on the transient characteristics of hydrodynamic cylindrical bearings during startup

The effect of surface roughness on the transient characteristics of the hydrodynamic cylindrical bearing during startup is studied. A mixed lubrication model considering both asperity contact and hydrodynamic fluid flow is solved. The asperity contact pressure is obtained by the Greenwood-Williamson (GW) contact model. The hydrodynamic pressure is calculated by modified average Reynolds equation with finite element method (FEM). The transient movement of the journal center, the transient average film thickness, the hydrodynamic pressure and the contact pressure are presented for different surface roughnesses. The contact time and contact zone in different types of surface roughness are obtained. The influences of the standard deviation of asperity height (a) and rough surface patterns on these parameters are analyzed. The results show that the surface roughness has an important influence on the transient characteristics of the bearing during the initial period of startup.