Full and partial boundary slippage effect on squeeze film bearings

Simple experiments were carried out to illustrate the effect of the boundary slippage on the load capacity of a squeeze film. The surface energy of the bearing surface was modified using laser excimer (UV laser). It was found that the load capacity can be reduced if the surfaces are modified to be hydrophobic. The boundary slippage effect on squeeze film was further studied theoretically to get more insight. The paper presents a mathematical model with a critical shear-stress criterion of slippage to describe the squeeze film effect. Three types of slippage, i.e. single zone partial slippage, single zone full slippage, and double zone partial slippage, are modeled. The analytical solution shows that the pressure distribution is a piecewise parabolic curve, where the pressure gradient can be discontinuous at the border of the slip and no-slip regions. Parametric studies illustrate the variations of the pressure and the boundary slippage under different conditions. It is demonstrated that with the increase of the length of the hydrophobic region, the maximum pressure does not increase continuously. Similar to the classical squeeze film bearing, the pressure decreases with the increase in the film thickness or the decrease in the approach velocity. The influences of the critical shear stress are also explored, and are found to significantly affect the squeeze behavior.