Analysis of the Oil Supply Behavior and Self-Lubrication Mechanism of the Oil-Bearing Surface

Oil-bearing is an important anti-friction and self-lubricating part in mechanical engineering field. The oil seepage characteristic in the pores of oil-bearing has an important influence on its lubrication performance. Although researchers have made a lot of efforts in this topic, however, the research on the self-lubrication mechanism of oil bearing is far from enough. And the mainstream research is mostly qualitative analysis from the perspective of tribological experiment. This method cannot accurately analyze the seepage flow and self-lubricating quality in the friction interface of the oil bearing. So It is necessary to further study the seepage characteristics and self-lubricating mechanism of the oil bearing. In this study, the coupled mechanical model of oil seepage in the porous matrix and the hydrodynamic lubrication in the bearing surface was established to study the seepage properties in the bearing system. The flow velocity of lubricating oil in the bearing system was analyzed. The relationship between the pressure field and velocity field of lubricating oil on the bearing surface was clarified. The influence of external load and rotating speed on the normal velocity of lubricating oil was revealed. The oil supply behavior and self-lubricating mechanism in the bearing surface were discussed. Results showed that there were circumferential rotating flow, radial telescopic flow and normal dialysis flow in the convergence zone of oil-bearing. The location of seepage velocity in all directions occurred in the convergence zone of friction interface. The flow condition in each direction was determined by the fluid pressure gradient in the same direction. Affected by the oil film pressure, the oil had obvious infiltration and precipitation phenomenon in the normal direction. The oil infiltrated into the porous matrix in the contact area and precipitated out to the porous surface at the inlet of the contact area, which constituted a closed-loop velocity streamline. The function of the velocity streamline was that when the oil infiltrated into the porous matrix in the contact area, the oil at the inlet of the contact area quickly filled the vacancy caused by the oil infiltration. A certain thickness of oil film can be maintained for a long time. So the streamline can enhance the pumping effect between the friction interfaces. The normal seepage velocity decreased with the increase of central film thickness and increased with the increase of rotating speed. The greater the seepage velocity, the more significant enhancement of the pumping effect. The high seepage velocity also made the oil precipitate faster to the inlet of the contact area. And the oil at the inlet was easier to enter the friction interface. The precipitation of lubricating oil can effectively compensate the penetration of oil film into porous matrix and ensure the good self-lubricating effect of bearing. The research results were of great significance to reveal the oil supply self-lubricating mechanism of oil-bearing.