Research On The Compression Mechanical Property Of Magnetorheological Fluids

As a kind of new intelligent material, magnetorheological fluids (MRF) are composedof micron and nanon magnetic particles with a size of about10nm in diameter, carrierliquid and dispersants. When an external magnetic field is applied, MRF would turn theoriginal liquid state to solid-like state, the apparent viscosity will increase a few orders ofmagnitude and this kind of change is rapid, reversible and controllable to the appliedmagnetic field. Due to the well rheological properties, MRF have an advantage indeveloping prospects and engineering applications such as in aeronautics, astronautics,automobile industry, seal, precision finishing, biotechnology, medical treatment, etc. Inorder to uncover the compression mechanical property of MRF and seek the method howto improve the shear yield stress of MRF, the mechanism analysis of MRF undercompression was carried out. The compression mechanical property of MRF test-bed wasalso designed and the related experiment was carried out. The main work in this paper areas follows:The force bearing status of MRF particles under applied magnetic field wasinvestigated. Aim at the three forms of particles chain, the compressive modulus of MRFparticles chain based on magnetic dipole theory under axial compression was analyzed indetail and the mechanism of compression strengthening was explored. The relatedexperiment on the axial compression mechanical property of MRF test-bed was carried out.The results show that the shear yield stress of MRF increases significantly under impressedpressure and the braking torque reaches nearly2.8times when the impressed pressure is2MPa.The radial compression mechanical property test-bed of MRF was designed. Thebasic parameter of test-bed was confirmed and the test-bed’s torque was analyzed. Themagnetic circuit was design based on magnetic ohm’s law and ampere’s law in detail. Themagnetic circuit was simulated based on related magnetic circuit analysis software(Infolytica Magnet Software).The radial compression mechanical property of MRF test-bed was set up. Thecharacteristics of excitation current-magnetic induction density, excitation current-shearyield stress and extrusion pressure-shear yield stress were carried out. Experimental resultsshow that the excitation current-magnetic induction density characteristic complies withthe design requirement. When the applied excitation current is3A and the radial pressureincreases from0to2.2MPa, the shear yield stress of MRF increases from37.89KPa to 120.24KPa and the increasing amplitude is82.35KPa. When the radial pressure is between1.2MPa and2.0MPa, the increase of MRF’s shear yield stress is evidently mostly.