ELASTOHYDRODYNAMIC LUBRICATION AT PURE SQUEEZE MOTION

Experimental and theoretical studies of elastohydrodynamically lubrica ted contacts normally assume static or quasi-static conditions. Non-st eady conditions are, however, common. In this paper the case of a ball impacting a flat lubricated surface is investigated theoretically. Th is case implies transient conditions and the lubricating effect is due to pure squeeze action. Pressure and film thickness distributions are computed during impact and rebound. The results of the analysis show the effects of ball mass, initial impact velocity, lubricant propertie s and the thickness of the applied lubricant layer on the minimum film thickness. Increased impact velocity increases the minimum value of f ilm thickness achieved during the bounce. The damping capacity of the lubricating film is very high at low impact velocity and small ball ma ss. In fact, the damping is so high that no rebound occurs if the velo city or the ball mass are smaller than certain critical values. The th ickness of the lubricant layer has no influence on the results if it i s greater than a certain value. If the pressure-viscosity coefficient is increased, the him becomes thicker.