Unsteady seepage behavior of lubricant on loaded porous surface

The seepage behavior of lubricant on a porous surface has a significant influence on its lubrication characteristics. This paper studied the unsteady seepage response of a lubricant on a loading porous surface. The exudation and supply behaviors of lubricant to the porous surface are discussed. The results show that the lubricant infiltration and exudation all exist on the porous surface. The normal seepage velocity of the lubricant can be divided into the primary velocity and secondary velocity at different positions of the whole surface. In most loading times, the primary velocity is greater than the secondary velocity. The change of the principal velocity shows that the infiltration and exudation of the lubricant arise in the contact area and its inlet, respectively. On both sides away from the entrance of the contact area, the secondary velocity goes through a diffusion, fluctuation, and stability process within the loading period. During the fluctuation of the velocity, the phenomena of infiltration and exudation alternate repeatedly. The secondary velocity occasionally exceeds the principal velocity. The normal pressure gradient is the internal cause that drives the diffusion and fluctuation of the secondary velocity. The velocity fluctuation can regulate lubricant quantity on the porous surface spontaneously, thereby forming a closed-loop adaptive lubrication system. The research can provide a theoretical basis for the lubricant supply behavior and the self-lubricating mechanism of the squeezed porous interface.