Simulation Of Microstructure And Mechanical Properties Of Magnetorheological Fluid

Magnetorheological fluid?MRF?is a kind of intelligent fluid with controllable structure and performance.It has excellent optical and mechanical properties.It has been widely used in electronic packaging,medical treatment,seismic damping and other engineering fields.Therefore,the theory and application of MRF have attracted extensive attention of researchers.in this paper,based on the traditional coarsening simulation method and the magnetic dipole model,the coarsening simulation model of MRF was established.The interaction potentials in MRF are described in detail.Based on the established coarsening model,the evolution process of the microstructure of MRF under uniform magnetic field was studied,as well as the changes of the microstructure and mechanical properties of MRF during compression and shear after its transformation into solid-like structure.The main contents and conclusions of this paper are as follows:Firstly,the evolution of the microstructure of MRF under magnetic field was studied in detail.Under the action of magnetic field,magnetic particles will produce dipole moments along the direction of magnetic field.Under the action of dipole moments,magnetic particles will aggregate along the direction of magnetic field to form chain and cluster structures.During the aggregation process,the potential energy of the system will gradually decrease and the stability of the system will gradually increase.At the same time,the aggregation behavior of magnetic particles is also affected by the magnetic field intensity and the volume fraction of magnetic particles.The increase of magnetic field intensity can accelerate the aggregation speed of magnetic particles and make the aggregation structure more compact and larger.Increasing the volume fraction of magnetic particles can also increase the aggregation structure of magnetic particles.Secondly,the compression performance of the solid-like structure after the aggregation of magnetic particles was simulated.For a MRF like solid structure,when the compression direction is along the direction of the magnetic field,the compressive stress is maximum,and during the compression process,as the compressive strain increases,the magnetic particles are more tightly bonded,and the magnetic interaction between the magnetic particles is mutual.The force is increased,and the anti-compression ability of the MRF is enhanced.The increase of the magnetic field strength and the increase of the magnetic particle volume fraction can enhance the resistance to compression and the compressive elastic modulus and the magnetoelastic modulus to some extent.In the cyclic shear process,the compressive stress varies with the number of cycles.The increase is gradually attenuated,and the amount of attenuation of the compressive stress increases as the magnetic field strength and the magnetic particle volume fraction increase.At the same time,the solid-like structure with magnetic particles aggregated is simulated under shear mode.For the solid structure of MRF,under shear action,the original ordered chain or cluster structure of magnetic particles undergoes the process of dislocation,reorganization and fracture.In addition,under the shear action,the magnetic particles will form lamellar and wall-like structures in the direction of shear field,and shear delamination will occur.The shear stress,shear elastic modulus and yield strength of MRF-like solid structures increase with the increase of magnetic field strength and volume fraction of magnetic particles.In a certain range of shear rate,the shear stress of magnetic particle solid structure increases with the increase of shear strength.When the shear deformation rate exceeds 0.05 ns^-1,excessive shear rate will lead to the decrease of shear stress.Under the cyclic shearing action,the lamellar structure formed by the magnetic particles in the first forward shearing in the system will move and aggregate along the shearing direction.The increase of the number of cycles makes the loopback area of the shear stress decrease,the shear resistance of the system decreases,and the stress gradually decreases during the shearing process.The increase of magnetic field strength and magnetic particle volume fraction gradually increases the stress loopback area in cyclic shear,and the shear resistance and shock absorption performance of MRF gradually increase.