Preparation And Study On Mechanical Properties Of MR Damping Materials Based On Graphene Oxide Coated Iron Particles

Magnetorheological(MR)fluid is a kind of suspension liquid formed by micro or nano iron particles scattered in the base fluid,which contains iron particles,carrier fluid and additives.In the absence of external magnetic field effect,it shows certain liquid state,it can transform rapidly from the liquid state into solid state in milliseconds under the action of magnetic field.MR fluid possesses the advantages of not only special magnetorheological effect,but also extensive using temperature range,safe and reliable,green environmental protection and so on.There are various MR devices made by MR fluids such as dampers,brakes,clutches,and hydraulic valves,etc.However,some problems have been exposed,such as undesirable sedimentation stability,narrow adjustable range,and imprecise mathematical model of MRF and so on.And the wide applications of MR fluids are seriously hindered by these problems in actual.Starting with the analysis of the components of MRF,the new composite iron particle-graphene oxide(GO)coated iron particles are prepared and the dosages of various additives are confirmed using control variable method.Samples with different contents of components are prepared and their main performances are tested,and then MR fluid samples with excellent performances are selected according to the results of test.In the aspect of theory,corrected coupling field mathematical model of the MRF shear yield stress is established,and the calculated results are compared with the test results to verify the correctness of the mathematical model.The researches of this paper mainly manifest as in the following aspects:1)Nanoscale MR fluids based on oleic acid coated Fe3O4 nanoparticles are prepared,and their performance are explored.The results show that the sedimentation stabilities of nanoscale MR fluids prepared are not ideal and remain to be further improved.2)Iron particles coated by graphene oxide are prepared,and the preparation plan is optimized by observing the SEM photos and sedimentation ratios of MR fluids.For the iron particles coated by surfactants,test conditions such as the ultrasonic intensity is optimized,which improving the coating effect.3)Various MRF samples with different content of components are prepared using control variable method,six series of samples named A-F,respectively.The influences of the dosage proportion of two kinds of composite iron particles,volume fraction of iron particles,the dosage of liquid paraffin on the performance of MR fluid are investigated through stability,viscosity and shear yield stress test.In addition,sedimentation stability and viscosity are compared between iron particles coated by graphene oxide and iron particles coated by carbon nanotubes.The results show that the effect on improving sedimentation stability of MRF using graphene oxide as the coating material is slightly less than that of carbon nanotubes,but the effect on reducing viscosity is significantly better than that of carbon nanotubes.4)Based on the theory of magnetic charge method and the coupling field,corrected coupling magnetic field mathematical model of the MRF shear yield stress is established,and the calculated results are compared with the test results to verify the correctness mathematical model.The innovations of this paper lay in:1)Iron particles coated by graphene oxide are prepared and mixed with iron particles coated by surfacants for the preparation of MRF.The preparation plan is optimized by testing sedimentation stability,viscosity and shear yield stress of MR fluid,and MR fluid samples with excellent properties are obtained finally.2)The corrected coupling field micromechanics model of the MRF shear yield stress is established,and the calculated results are compared with the test results to verify the correctness mathematical model.