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The highly efficient exudation of lubricant in porous self-lubricating materials significantly influences the formation of self-lubricating films. In this paper, micropores with inner spiral bulge structures are considered, and their influence on the capillary behaviors of the lubricant is discussed to reveal the capillary rising mechanism. The results show that the Taylor capillary lift phenomenon is produced in the spiral bulge structure of the micropore, and the capillary lift force is enhanced. The spiral structure decreases the effective diameter of micropores. The magnitudes of the pressure and velocity in the spiral structure pores are larger than those in smooth pores. The liquid in the upper part of the micropores forms a velocity vortex during its upward rotation along the spiral channel, which promotes the capillary rising behavior. For smaller pitches, the velocity vortex increases, and the rising speed of the lubricant grows. The inner spiral bulge structure gives the micropores an excellent capillary rising ability. The quantitative characterization and mechanism reveal that the capillary rising behavior can be used to guide the bionic designs of pores in self-lubricating materials. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]