| Microcirculation lubrication is the microcirculation of the lubrication fluid in thesurface of tribological mate, which can improve the stress distribution of theinterfacial film and its lubrication characteristics. Based on the functioncharacteristics of the oriented aggregation and motion of magnetic particle dipolarityin the magnetic fluids under the magnetic field and the structure characteristics ofporous material, the theory of microcirculation lubrication controlling of magneticfluid and the characteristics of magnetic film are studied. The research is supportedby the National Natural Science Foundation.Based on the structure mechanism of permanent micro-magnets and thepore-surface effect of magnetic fluid under the magnetic field, a mechanism model ofmagnetic flow circulation lubrication is established in the paper. With this model, thestructure design of the magnetic field and its distribution are studied. Based on this,the effects of the magnetic fluid viscosity (μ), magnetic particle content (m),magnetic fluid saturation magnetization (Mg) and the intensity of external magneticfield (Hm) and its distribution (▽Hm) on the lubrication properties (such as loadcapacity (W), friction force (Fs) and friction coefficient (Cf)) are studied.Both the porous output model of magnetic fluid and the mathematical model foroptimization design of micro-magnets are established to analyze the influence of theporous structure parameters in the tribological system on the output was analyzed.The optimized micro-magnets structure can enhance the output capability of magneticflow. Experiments are conducted to study the coupling effects between the saturationmagnetization, the liquid viscosity and the structure parameters of the micro-magnets.The effect of pores on the microcirculation lubrication control of magnetic flow andits magnetic film characteristics are also investigated.In order to build the controllable micro-system in the tribological micro-system,The controllability of the interaction between the magnetic-pole (S-S, N-N and N-S)and the friction surface is studied experimentally and theoretically. The results showthat the influence of magnetic-pole effect on the magnetic flow microcirculation isstudied experimentally and theoretically. The result also show that the reasonabledistribution of magnetic-pole can improve the magnetic intensity and its gradient controllability on the annular working surface, which can improve the lubricationperformance of magnetic flow microcirculation and its lubrication controllability.Based on the generalized microcirculation lubrication model, studies are conductto match the external magnetic field volume (number) and magnetic distance(achieving by adjusting the volume of magnetic isolation brone ring or its quantity) inboth the simulation analysis and the tribological experiment. The results show that thestrength of the magnetic field on the working surface with permanent micro-magnetsincreases as the increasing of the external magnetic field volume and as thedecreasing of the magnetic distance; the reasonable magnetic field and its magneticgradient distribution on the working surface can be achieved by the optimization ofthe external micro-magnets volume and the magnetic distance, which can be in morestable lubrication state. The results also show that the magnetic flield compabilitydesign can get the tribological system with good lubrication properties.The paper also discusses the lubrication characteristics of the magnetic flowmicrocirculation in the engineering application with the examples of porous materialand sliding bearing, and its engineering value had been proved effectively accordingto the two following factors.(1) A microcirculation lubrication model of magnetic flow in the low elasticModulus porous material is established. With this model, the effects of the materialand working condition parameters on its lubrication properties are studied. The resultsshow that the model can improve obviously the boundary and mixed lubrication ofporous material. With this, a design atlas for porous elastic bearing is achieved. Theresults also widen the application of classical Stribeck curve.(2) Based on the research of the lubrication characteristics of magnetic flow inthe high-speed journal bearing, it reveals the couple mechanism between the gradientmagnetic field and the cohesive force of magnetic fluid. The research shows that themagnetic lubrication can obviously improve lubrication performance of the magneticbearings with the considerations of the coupling effect between the rotating item ofbearing and its squeezing item. |
PDF Full Text Request