Researches On The Hole-wedge Effect Of Micro-circulating And Self-compensating Lubrication Of Ferrofluid And Its Application

The structure design of friction pairs based on the principle of bionics for realizing self-compensating lubrication is helpful to develop new tribological functional components.Based on the research on the hole-wedge effect and the micro-circulating theory of multiphase lubricant colloid in porous materials, the structural characteristics of pores and the necessity conditions of flow are discussed, the rheological model is established and its effect of wall-slip phenomenon is also analyzed,in this paper. The results show that the pressure difference existing at the two ends is the necessity condition of lubricant flowing in micro hole, and that the radius of hole is smaller, the resistance to flow is greater, and that a wall-slip layer occurs in lubricant and its wall-slip effect can help to improve flowing characteristics of lubricant through the holes.In order to improve the working stability of lubricant colloid, a two-phase wedge-sliding model is established and its computing method is given accordingly. Researches show that, the Drift-restraining Angle and Lateral Expansion-restraining Angle can effectively represent the phase-drift changing trend, and the optimal ratio of composing ingredients can be used to guide the optimization design of multiphase lubricant colloid.In order to realize the process controllability of ferrofluid, the revised Bernoulli Equation and Reynolds Equation in cylindrical coordinate system are established, the corresponding static and dynamic behaviors are also carried. The researches show that the static lifting height of ferrofluid in micro holes is mainly decided by the external magnetic field and the micro hole itself, however irrelevant to the content of magnetic particles in ferrofluid, a top heat source may restrain the flow of ferrofluid in micro holes, while such problem can be improved by reducing the environmental temperature gradient and increasing the strength of external magnetic field, the microcirculation of ferrofluid flowing in the hole-wedge coupled friction pair is proved and its existence can improve the self-compensating capability and the resistance to load fluctuation of ferrofluid lubrication film.Based on the theoretical researches above, the ferrofluid colloid by adding micro/nano magnetic particales and a ferrofluid lubrication porous thrust bearing are designed, and a series of tribological contrast experiments are carried. The researches show that the adaptive compensation ability of ferrofluid lubricating film is relative to the height of reversed cone of friction pair, the thickness of ferrofluid lubrication film can be adaptive adjusted along with the variation of load, and the existence of external magnetic field can improve its bearing capacity, the friction coefficient when non-ferrofluid lubrication increases however decreases when ferrofluid lubrication along with the increase of circumferential shear velocity. This thrust bearing is more suitable for high speed and heavy load occasions, and with the bigger load and higher circumferential shear velocity, the antifriction effect is more notable.