Research On Constitutive Relation And Modeling Method Of Magnetorheological Polishing Fluids Based On Close-packed Hexagon Structure

With the development of science and technology,the requirement of surface precision is much higher in modern society.High-precision surface processing technology of materials,especially high-precision aspheric surface processing technology,has always been a research hotspot.Magnetorheological polishing,as a new micro-nano polishing technology,overcomes many shortcomings of traditional polishing technology,so it has been widely used in optical processing,semiconductor manufacturing,mechanical processing and other fields.Magnetorheological polishing fluids as the basis and core of magnetorheological polishing technology,its characteristics directly affects the polishing effect.Therefore,it is necessary to conduct a systematic,comprehensive and in-depth analysis of Magnetorheological polishing fluids.Magnetorheological polishing fluids are developed from magnetorheological fluids,which have the similar rheological properties to magnetorheological fluids.It presents as Newtonian fluids in the absence of magnetic field,and when under the action of external magnetic field,it rapidly changes to viscoplastic Bingham medium.In this paper,the microstructure of magnetorheological fluids are analyzed from the micro point of view and the constitutive model are established as well.On this basis,the constitutive model of magnetorheological polishing fluids are further established and the influencing factors are also analyzed.In this paper,the following studies are carried out centering on magnetorheological polishing fluids.The content of the paper mainly includes:(1)Referring to the relevant literature,the composition of magnetorheological polishing fluid are analyzed.Then the suitable materials and preparation technology are selected to compound the magnetorheological fluids,and the effect of composition change on material performance is analyzed by experiment.(2)Based on the force analysis of carbonyl iron powders in magnetorheological fluids under magnetic field,the dynamic model of carbonyl iron powder particles is established,and the effects of volume fraction of carbonyl iron powders on the microstructure of magnetorheological fluids are simulated.Referring to the simulation results and previous studies,a close-packed hexagon structure model is proposed for the microstructure of high concentration magnetorheological fluids under external magnetic field.(3)Based on the close-packed hexagon structure and dipole theory,the interaction force of carbonyl iron powders in magnetorheological fluids is deduced and calculated,and the formula of shear yield stress affected by adjacent chains is obtained.Finally,the constitutive model of high concentration magnetorheological fluids is established and verified by experiments.Then the effects of simulation and experiment on the rheological properties of magnetorheological fluids are analyzed.(4)Considering the effect of polishing particles on the microstructure of magnetorheological polishing fluids,the constitutive model of magnetorheological polishing fluids is derived from the constitutive model of magnetorheological fluids and verified by experiments.Based on the constitutive model,the influencing factors on the properties of magnetorheological polishing fluids are analyzed,which provides a theoretical reference for the preparation of MR polishing fluids.