# Simulation Study of a New Magnetorheological Polishing Fluid Collector Based on Air Seal
## 1 Introduction  
MR polishing is widely used in various fields, especially in the processing of precision components, such as aerospace, biological, and precision machinery [1; 2; 3]. MR fluid is mainly composed of base fluid, magnetically sensitive particles, polishing abrasive particles, and a small amount of additives [4]. Under the action of the gradient magnetic field, the magnetically sensitive particles (carbonyl iron powder) in the liquid are arranged sequentially along the direction of the magnetic field, and the MR fluid transiently becomes a non-Newtonian fluid [5]. After the magnetic field is removed, the MR fluid returns to a Newtonian fluid. The process can be completed within 0.1\(\sim\)1 ms [6; 7]. Unlike traditional polishing, MR polishing is a deterministic process characterized by efficiency, high precision, and good surface quality [8; 9]. After polishing, the MR fluid is usually recovered by a magnetically sealed type of recovery. Because the magnetic field strength of the collector at the magnetic seal is greater than the magnetic field strength of the polishing wheel surface, the abrasive polishing particles in the magnetic seal are wrapped by carbonyl iron powder on the surface of the polishing wheel. During long-term processing, the polished abrasive particles at the magnetic seal seriously wear the surface of the polishing wheel. The surface contour accuracy of the worn polishing wheel is reduced, and the grooves formed by wear affect the recovery of polishing liquid, interfering with the formation of subsequent regular polishing belts and introducing processing errors, mainly intermediate frequency errors [10; 11]. The oxides produced by wear also change the rheological properties of the MR fluid, reducing the cyclic service life of the MR fluid and seriously affecting the processing process. For the simulation of MR polishing fluid, the non-Newtonian fluid viscosity model or the built-in magnetohydrodynamic model (MHD) can usually be used in simulation software. [PERSON] et al. [12] used COMSOL multiphysics software to analyze the computational fluid dynamics of MR fluids in the two-dimensional computational domain. The influence of different process variables on the flow variables in the processing of gear components is explored. [PERSON] et al. [13] artificially optimized the surface microstructure of the polishing disc. Based on the rheological behavior measured by MR fluid in the rheometer, a simulation model of the machining process was established in COMSOL. [PERSON] et al. [14] used the Bingham model to simulate the two-dimensional dynamics of MR polishing fluid in a workpiece fixture. To calculate the stress generated in the polishing process, [PERSON] et al. [15] simulated the formation of a polishing pad and the size of polishing pressure in chemical mechanical magnetorheological polishing. The simulation results were consistent with the experimental results obtained for aluminum alloy. [PERSON] et al. [16] regarded MR polishing fluid as a Herschel-Bulkley fluid. The dynamic pressure on the workpiece surface and wall shear force at different machining clearances and velocities were calculated. [PERSON] et al. [17; 18] chose the Herschel-Bulkley fluid model to replace the Bingham fluid model when studying the effect of secondary fracture surface on the formation of a pressure field in the MR polishing ribbon. The fluid model was also used to study the formation of shear stress field in the polishing entrance area. [PERSON] [19] simulated the magnetic field in the Maxwell model and loaded the results into simulation software to realize the simulation of MR plane polishing. [PERSON] [20] imported a staggered arrangement of permanent magnet ferromagnetic induction intensity into simulation software. The two-phase flow characteristics of MR polishing liquid in the polishing process were simulated. Both simulation methods of MR polishing fluid have been widely used and verified. Therefore, it can be selected according to demand.