A magnetic fluid jet shear polishing device and method based on CFD simulation

Abstract

The present invention discloses a magnetic fluid jet shear polishing device and method based on CFD simulation, wherein the device comprises an industrial five-axis machine tool, a fluid circulation system, a jet polishing module and a computer CNC numerical control system. The jet polishing module and the workpiece 8 to be processed are respectively mounted on the workbench and the tool mounting seat of the industrial five-axis machine tool, and can realize five-axis polishing processing under the control of the computer CNC numerical control system. The jet polishing module comprises a jet tool head and a rotating magnetic field generating device. The present invention applies a rotating magnetic field at the jet outlet of the jet tool head to drive the ferroferric oxide particles in the polishing liquid to arrange in a chain structure along the direction of the magnetic lines of force, thereby significantly improving the viscosity of the polishing liquid and giving it high-speed self-rotating motion characteristics. The high-speed rotation of the liquid column and the enhanced viscosity generate a stronger shear force, which enables efficient material removal on the workpiece surface.

Description

Technical Field

[0001] The present invention belongs to the technical field of polishing technology, and in particular relates to a magnetic fluid jet shearing polishing device and method based on CFD simulation. Background Art

[0002] In modern manufacturing, precision surface polishing is a key step in improving component performance and appearance quality. This is especially true in high-tech fields such as optical components, aerospace components, and complex mold manufacturing, where the demand for efficient and high-precision surface processing technologies is particularly urgent. However, traditional polishing methods are gradually becoming inadequate in terms of efficiency and accuracy, especially when processing complex curved surfaces and high-precision surfaces, making it difficult to achieve a balanced balance between material removal efficiency and surface quality.

[0003] Traditional mechanical polishing removes material by applying pressure to the workpiece surface using rigid abrasive tools. Although this method is mature, it is prone to surface scratches, local over-processing, and thermal damage, and has poor adaptability to complex geometries. Although chemical mechanical polishing (CMP) performs well in removing material at the microscopic level, it is inefficient and has poor adaptability to hard material processing. It also requires the use of chemical polishing fluid, which brings about environmental pollution problems.

[0004] In recent years, jet polishing technology has gained increasing attention due to its non-contact processing capabilities. By applying a high-speed liquid column to the workpiece surface, it not only avoids potential surface damage caused by contact with a rigid tool but also improves its adaptability to complex curved surfaces. However, existing jet polishing technology still faces numerous challenges, such as low material removal efficiency, poor jet column stability, and uneven removal distribution. This is primarily due to the low viscosity of conventional jet polishing fluids, which makes it difficult to maintain the integrity of the liquid column during high-speed flow. Furthermore, the liquid column is easily broken by external disturbances, resulting in uneven removal. Summary of the Invention

[0005] In order to make up for the shortcomings of the existing technology, the present invention provides a magnetic fluid jet shear polishing device and method based on CFD simulation to solve technical problems such as low material removal efficiency, poor liquid column stability and difficult to control shear force distribution in traditional jet polishing.

[0006] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0007] First, a CFD-based magnetic fluid jet shear polishing device includes an industrial five-axis machine tool, a fluid circulation system, a jet polishing module, and a computer numerical control (CNC) system. The jet polishing module and the workpiece to be machined are mounted on the worktable and tool mounting base of the five-axis machine tool, respectively, enabling five-axis polishing under the control of the CNC system.

[0008] The jet polishing module includes a jet tool head, a rotating magnetic field generator, and an air compressor. The jet tool head comprises an outer mounting sleeve and an inner jet nozzle. The polishing liquid is sprayed onto the workpiece through the jet nozzle. A gas injection chamber is provided between the mounting sleeve and the jet nozzle. This chamber, in conjunction with the air compressor, creates a stable airflow around the polishing liquid ejected from the jet nozzle. The rotating magnetic field generator is used to adjust the rotation speed of the magnetic particles in the sprayed polishing liquid and to alter its viscosity.

[0009] The fluid circulation system is used to provide polishing liquid to the jet polishing module, and to recover the polishing liquid after the jet is completed, and output the recovered polishing liquid to the jet polishing module, thereby forming a circulation process of the polishing liquid.

[0010] Furthermore, the rotating magnetic field generating device includes a circuit connector and an electromagnet. The electromagnet is fixed to the jet tool head and is located below the jet outlet in the jet nozzle to prevent high-speed rotating high-viscosity polishing liquid from abrading the inner wall surface of the jet outlet. The electromagnet is provided with multiple groups of coils. Each group of coils is evenly distributed along the circumference of the electromagnet axis. Each group of coils is energized through the circuit connector. Under the action of the magnetic field, the magnetic particles in the polishing liquid can be arranged along the magnetic lines of force to form a chain or columnar structure.

[0011] Furthermore, the fluid circulation system includes a mixing and stirring module and a circulation transport module. A drainage port is provided at the bottom of the processing chamber. The input of the mixing and stirring module is connected to the drainage port of the processing chamber via a water pipe, thereby stirring the output polishing liquid. The input of the circulation transport module is connected to the output of the mixing and stirring module, capable of transporting the stirred and mixed polishing liquid to the jet polishing module output, thereby realizing the recycling of the polishing liquid.

[0012] Furthermore, the magnetic particles in the polishing liquid can rotate at a speed of 10-100 revolutions per second under the action of a magnetic field, and the viscosity is 5-200 mPa·s.

[0013] In the second aspect, a polishing method of a magnetic fluid jet shear polishing device based on CFD simulation, the specific steps are as follows:

[0014] 1) A magnetic fluid polishing slurry was prepared, wherein the magnetic fluid polishing slurry was prepared by mixing 10% silicon carbide abrasive particles with a particle size of 10 μm, 4% ferroferric oxide magnetic particles, 0.2% polyacrylate, 2% ethylene glycol and deionized water.

[0015] 2) Fix the workpiece to be processed on the fixture of the five-axis machine tool, and adjust the position of the output port of the jet polishing module through the computer CNC numerical control system so that the surface of the workpiece to be processed is accurately aligned with the polishing range of the output jet liquid column.

[0016] 3) Set the jet pressure, jet time, and polishing path for the jet polishing module. Adjust the rotating magnetic field strength and frequency to control the liquid column viscosity and the rotation speed of the magnetic particles in the polishing liquid. Start the air compressor to spray the magnetic fluid polishing liquid through the jet tool head. The inner jet nozzle forms a jet liquid column, and the outer layer is fed with compressed air.

[0017] 4) The supply metering pump in the fluid circulation system is activated to deliver the polishing fluid from the mixing tank to the jet tool head after stabilizing the pressure through the damper and back-pressure valve. The polishing fluid then forms a linear jet through the jet nozzle of the jet tool head and is sprayed onto the inner wall of the workpiece. The polishing fluid then flows to a collection area at the bottom of the workpiece and is recovered by the recovery metering pump and returned to the mixing tank.

[0018] 5) Analyze the flow field distribution and material removal profile of the jet liquid column through CFD simulation technology, and adjust the magnetic field intensity, jet pressure and magnetic field rotation speed.

[0019] Furthermore, the CFD simulation technology uses a multi-model coupling simulation. The multiphase flow VOF model, discrete phase DPM model, erosion Oka model, and viscosity model are coupled and optimized. The specific optimization steps are as follows:

[0020] S1: Use SolidWorks modeling software to build a model of the polishing condition, and import the polishing condition simulation model into the SpaceClaim module in Ansys-Workbench to obtain a simulation model of the fluid domain;

[0021] S2: Use Meshing in Ansys Workbench to perform tetrahedral meshing on the simulation model of the fluid domain;

[0022] S3: Use Fluent in Ansys Workbench to perform computational fluid dynamics calculations on the simulation model of the fluid domain;

[0023] S3.1 sets the turbulence model of the simulated fluid and sets the viscosity of the magnetic fluid under the action of the magnetic field in the viscosity model.

[0024] S3.2 uses the multiphase flow VOF model to model continuous multiphase fluid.

[0025] S3.3 uses the discrete phase model DPM to perform transient three-dimensional simulation of abrasive particles and predict the motion trajectory of the particles.

[0026] S3.4 uses the erosion model to perform erosion calculations on the simulation model.

[0027] S3.5 sets the sliding grid to simulate the rotating magnetic fluid under the action of a magnetic field.

[0028] S4: Use the post-processing software Tecplot to analyze the simulation results.

[0029] Furthermore, the turbulence model settings employ a shear stress transport (SST) model based on the k-ω turbulence model to represent the high Reynolds number turbulent flow occurring within and outside the inner boundary layer during the jet process. The viscosity model uses the liquid viscosity measured by a viscometer at a fixed magnetic field strength for calculation.

[0030] Furthermore, in the multiphase flow VOF model, two items of water and air are set, the liquid phase is used to simulate the polishing liquid, and the gas phase is used to simulate the protective gas ejected from the outside of the jet tool head with a double-layer nozzle structure.

[0031] Furthermore, in the discrete phase DPM model setting, a one-way coupling is used between the liquid and solid phase motions. The particle turbulence diffusion model uses a random walk model. When calculating the discrete phase model, the motion trajectory of the particle during the jet process is obtained by integrating the formula with the discrete phase time step number. The specific calculation is shown in Formula 2:

[0032]

[0033] Where v p is the particle velocity, t is the time, v is the fluid velocity, ρ p is the particle density, ρ is the fluid density, F D is the resistance per unit particle mass during the jet process, g is the acceleration due to gravity, and F is the additional acceleration per unit particle mass.

[0034] The resistance force F on the particle D The value of depends on the Reynolds number of the fluid flow and the difference between the fluid flow and particle velocities. The specific calculation is shown in Formula 3:

[0035]

[0036] Where d p is the abrasive particle diameter, C D is the resistance coefficient, μ is the fluid dynamic viscosity, R e is the relative Reynolds number, ρ p is the particle density. D is the resistance per unit particle mass during the jet process.

[0037] The calculation of the relative Reynolds number Re during the jet process is shown in Formula 4:

[0038]

[0039] Where d p is the abrasive particle diameter, μ is the fluid dynamic viscosity, ρp is the particle density, v p is the particle velocity and v is the fluid velocity.

[0040] S3.4 uses the erosion model to perform erosion calculations on the simulation model.

[0041] The Oka erosion model is set up. Based on the discrete phase model (DPM), the computational erosion model is enabled. The Oka erosion model is used to calculate the material removal rate and predict deterministic surface shape control. Erosion damage at different angles (E(δ)) can be expressed using the formulas shown in Equations 5-8, taking into account the material properties of the particles and sample, as well as the impact conditions.

[0042]

[0043] In the formula is the erosion rate when particles impact at a vertical angle, which represents the unit volume of material lost per unit mass of particles (mm3 / kg) impacting the surface; it is composed of two trigonometric functions and the initial hardness of the material; E(δ) is the erosion caused by particles impacting at an angle of δ, and g(δ) is the impact angle function when impacting at an angle of δ; n1 and n2 are exponents determined by the impact velocity and other impact conditions; Hv is the initial Vickers hardness of the workpiece. m is the particle movement speed; d m is the abrasive particle diameter; v ref ,d ref represent the reference speed and reference diameter respectively; k i Represents the particle property factor.

[0044] Furthermore, in the sliding grid setting, a sliding grid is used to simulate the self-rotation of the liquid under the action of a magnetic field. Under the action of a rotating magnetic field, the self-rotation speed of the liquid is consistent with the rotation speed of the magnetic field, that is, the magnetic field rotation speed is used for setting to simulate the self-rotation of the liquid under the action of a magnetic field. The motion of any point in the domain is defined by the rate of change of the position vector with time. to describe, and in the rigid body rotation of the grid, the velocity is constant; the rate of change The calculation of is shown in formula 9:

[0045]

[0046] In the formula is the rate of change of the position vector over time; To describe the rotation speed of the grid; is the position of any point in the domain; is the velocity field, representing the velocity of each point in the moving mesh.

[0047] Compared with the prior art, the present invention has the following advantages:

[0048] 1. This invention applies a rotating magnetic field at the jet outlet of the fluidic tool head, driving the ferroferric oxide particles in the polishing fluid to align along the magnetic field lines, forming a chain-like structure. This significantly increases the viscosity of the polishing fluid and imparts self-rotating motion. The high-speed rotation and enhanced viscosity of the fluid column generate stronger shear forces, enabling efficient material removal from the workpiece surface. Furthermore, by incorporating CFD simulation technology to optimize the flow field behavior and shear force distribution of the fluid column, machining efficiency and precision are further enhanced.

[0049] 2. The present invention adopts a jet tool head with a double-layer nozzle structure, in which the inner nozzle is used to spray high-viscosity magnetic fluid polishing liquid, and the outer nozzle is used to let in compressed air to form an airflow protection layer, thereby reducing the impact of external interference on the liquid column and delaying the occurrence of the breakage point, thereby ensuring the stability of the polishing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0051] Figure 2 Schematic diagram of the structure of the rotating magnetic field generating device and the jet tool head in the present invention;

[0052] Figure 3 This is a flow chart of the CFD simulation optimization module in the present invention;

[0053] Figure 4 This is a comparison chart of the polishing effects of traditional jet polishing and rotating magnetic field magnetofluid jet shear polishing.

[0054] Figure numerals: 1. Supply metering pump; 2. Damper; 3. Back pressure valve; 4. Pressure gauge; 5. Pressure regulating valve; 6. Industrial five-axis machine tool; 601. X-axis displacement assembly; 602. Y-axis displacement assembly; 603. Lifting and lowering adjustment assembly; 604. Rotary drive assembly; 605. Angle adjustment assembly; 7. Jet tool head; 701. Jet nozzle; 702. Gas spray chamber; 703. Electromagnet; 704. Circuit connector; 8. Workpiece to be processed; 9. Workpiece fixture; 10. Drain port; 11. Recovery metering pump; 12. Stirring blade; 13. Electric control cabinet; 14. Controller; 15. Air compressor; 16. Return pipe. DETAILED DESCRIPTION

[0055] In the description of the present invention, it should be understood that the terms "one end", "the other end", "outside", "upper", "inside", "horizontal", "coaxial", "center", "end", "length", "outer end" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be understood as limiting the present invention.

[0056] The present invention will be further described below with reference to the accompanying drawings.

[0057] A stepless and adjustable rotary abrasive water jet polishing device comprises an industrial five-axis machine tool 6, a fluid circulation system, a jet polishing module and a computer CNC numerical control system. The inner cavity of the industrial five-axis machine tool 6 constitutes a closed processing chamber. The jet polishing module and the workpiece 8 to be processed are respectively mounted on the workbench and tool mounting seat of the industrial five-axis machine tool 6, and can realize five-axis polishing processing under the control of the computer CNC numerical control system. The fluid circulation system is used to provide a magnetic fluid polishing liquid to the jet polishing module, which is sprayed onto the workpiece 8 to be processed through the jet polishing module for polishing processing. At the same time, the fluid circulation system can recover the magnetic fluid polishing liquid after the jet is completed and output it to the jet polishing module, forming a circulation processing of the magnetic fluid polishing liquid.

[0058] In this embodiment, the industrial five-axis machine tool 6 includes a frame, an X-axis displacement assembly 601, a Y-axis displacement assembly 602, a rotary drive assembly 604, a lifting and adjusting assembly 603, and an angle adjustment assembly 605. Among them, the X-axis displacement assembly 601 and the Y-axis displacement assembly 602 are both installed on the frame, and are used to drive the workpiece 8 to move in both directions along the horizontal direction. The rotary drive assembly 604 is installed on the moving end of the Y-axis displacement assembly 602, and is used to drive the workpiece 8 to rotate. A workpiece clamp 9 is provided in the center of the rotary drive assembly 604, which can clamp and fix the workpiece 8 to prevent the position of the workpiece 8 from shifting during the machining process. The lifting and adjusting assembly 603 is arranged at the top of the frame, and is used to drive the jet polishing module to be lifted and lowered. The angle adjustment assembly 605 is installed on the moving end of the lifting and adjusting assembly 603, and is used to adjust the inclination angle of the jet outlet in the jet polishing module.

[0059] like Figure 1As shown, the jet polishing module includes a jet tool head 7 and an air compressor 15. The jet tool head 7 has a double-layer nozzle structure, including an outer mounting sleeve and an inner jet nozzle 701. The magnetic fluid polishing liquid is sprayed onto the workpiece 8 through the jet nozzle 701. A gas spray chamber 702 is defined between the mounting sleeve and the jet nozzle 701. The mounting sleeve is provided with an air intake duct connected to the gas spray chamber 702. The outer end of the air intake duct is connected to the air compressor 15 via an air pipe.

[0060] During operation, the air compressor 15 compresses air and outputs it from its outlet. The output gas is introduced into the gas spray chamber 702 through the air pipe and the air inlet pipe, and ejected from the gas nozzle at the bottom of the gas spray chamber 702. A stable high-pressure airflow is formed around the magnetic fluid polishing liquid ejected by the jet nozzle 701, thereby maintaining the stability of the liquid column.

[0061] In this embodiment, the gas chamber 702 is annular in structure. The direction of the gas flow in the chamber 702 is consistent with the direction of the jet, and the airflow velocity is adjustable to match the velocity of the liquid jet. By introducing a stable airflow, the internal jet is stabilized, preventing premature breakup of the jet. A protective layer is formed to reduce the impact of external disturbances on the liquid column, thereby improving jet stability. The pressure of the magnetic fluid polishing liquid ejected through the jet nozzle 701 is 0-15 bar.

[0062] Furthermore, a rotating magnetic field generating device is provided on the jet tool head 7 to adjust the self-rotation speed and viscosity distribution of the liquid column, thereby achieving the effect of shear polishing. Figure 2 As shown, the rotating magnetic field generating device includes a mounting bracket, a circuit connector 704 and an electromagnet 703. The electromagnet 703 is fixed to the mounting housing of the fluidic tool head 7 through the mounting bracket.

[0063] In this embodiment, the electromagnet 703 is located below the jet outlet of the jet nozzle 701. This prevents the magnetic fluid polishing fluid from shearing and polishing inside the jet nozzle 701 under the influence of the rotating magnetic field, thereby damaging the jet outlet of the jet nozzle 701. Six groups of coils are provided on the electromagnet 703. Each group of coils is evenly distributed along the circumference of the electromagnet 703, and each group of coils is evenly spaced 60 degrees apart.

[0064] Electromagnet 703 surrounds the center of the jet outlet. The inner diameter of the ring structure matches the outer diameter of the jet tool head 7, ensuring that the magnetic field is concentrated in the jet outlet area. Under this magnetic field, the internal magnetic fluid polishing fluid can rotate at a speed of 10-100 revolutions per second; and the viscosity of the magnetic fluid polishing fluid under this magnetic field is approximately 5-200 mPa·s.

[0065] Under the action of a magnetic field, magnetic particles (Fe3O4Fe_3O_4Fe3O4) are arranged along the magnetic lines of force, forming chain or columnar structures, which significantly increases the viscosity of the liquid. The viscosity change formula is shown in Formula 1:

[0066] η m =η0·(1+Φ·μ r ·B 2 ) (1)

[0067] Where η m is the viscosity under the action of magnetic field (unit: mPa·s); η0 is the basic viscosity in the absence of magnetic field (2 mPa·s); Φ is the volume fraction of magnetic particles (4%); μ r is the relative magnetic permeability of the magnetic particles; B is the magnetic field intensity (unit: T).

[0068] like Figure 1 As shown, the fluid circulation system includes a mixing and stirring module and a circulation conveying module. Among them, a drain port 10 is provided at the bottom of the processing chamber. The input end of the mixing and stirring module is connected to the drain port 10 of the processing chamber through a water pipe, which is used to stir the output magnetic fluid polishing liquid to avoid the abrasive particles used to configure the magnetic fluid polishing liquid from being deposited due to natural sedimentation, thereby causing the concentration of the magnetic fluid polishing liquid to decrease, affecting the polishing efficiency and causing pipeline blockage. The input end of the circulation conveying module is connected to the output end of the mixing and stirring module, and can transport the magnetic fluid polishing liquid that has been stirred and mixed to the output end of the jet polishing module, thereby realizing the recycling of the magnetic fluid polishing liquid.

[0069] like Figure 1 As shown, the mixing and stirring module includes a stirring tank, a recovery metering pump 11, a stirring blade 12 and a stirring drive motor. Among them, a water supply pipeline is arranged at the input end of the recovery metering pump 11 and the output end of the processing chamber. The output end of the recovery metering pump 11 is provided with a water outlet pipe. The magnetic fluid polishing liquid output from the processing chamber can be discharged into the stirring tank through the recovery metering pump 11 and the water outlet pipe. The stirring blade 12 is rotatably connected in the stirring tank and can be rotated under the drive of the stirring drive motor to achieve mixing and stirring of the input stirring liquid, thereby avoiding the abrasive particles used to configure the magnetic fluid polishing liquid from being deposited due to natural sedimentation, which in turn leads to a reduction in the concentration of the magnetic fluid polishing liquid, affecting the polishing efficiency and causing pipeline blockage.

[0070] The circulation and delivery module includes a supply metering pump 1, a liquid inlet pipe, and a pipe protection assembly. A return pipe 16 is provided between the output of the mixing tank and the input of the supply metering pump 1. The output of the supply metering pump 1 is connected to the fluidic tool head 7 via the liquid inlet pipe. The pipe protection assembly, installed on the liquid inlet pipe, protects the pipe from damage caused by excessive hydraulic pressure within the pipe.

[0071] The pipeline protection assembly includes a damper 2, a back-pressure valve 3, a pressure gauge 4, and a pressure regulating valve 5, which are connected in sequence. The input end of the damper 2 is connected to the output end of the metering pump 1; the output end is connected to the liquid inlet pipe. With the cooperation of the back-pressure valve 3, a magnetic fluid polishing liquid jet with stable pressure can be formed in the liquid inlet pipe. The pressure gauge 4 is used to monitor the pressure of the magnetic fluid polishing liquid jet in the liquid inlet pipe in real time. The pressure regulating valve 5 controls the pressure of the magnetic fluid polishing liquid jet in the liquid inlet pipe, so that the pressure regulation of the magnetic fluid polishing liquid jet is closed-loop.

[0072] During operation, the magnetic fluid polishing liquid is received by a metering pump 1 from the mixing tank and delivered to the inlet pipe. The liquid flows through a damper 2, backpressure valve 3, pressure gauge 4, and pressure regulating valve 5 on the inlet pipe, reaching the set pressure. The liquid is then sprayed onto the workpiece being polished by a jet tool head 7, polishing the workpiece. The liquid that reaches the bottom of the processing chamber is discharged from a drain port 10 and returned to the mixing tank via a water pipe and a recovery metering pump 11.

[0073] In this embodiment, the supply metering pump 1 is a single-port diaphragm metering pump with a maximum flow rate of 3380 L / h, a maximum power of 7.5 kW, and a standard operating pressure of 200 bar. The damper 2 is a diaphragm pulse damper 2 model RXMZ-L6.0 / 2.5. The back pressure valve 3 is a model RXBF-L / 1.0 back pressure valve 3; and the pressure gauge 4 is a model HC-Y810 digital electric contact pressure gauge 4.

[0074] In this embodiment, the CNC control system includes an electrical control cabinet 13 and a controller 14. The electrical control cabinet 13 uses a PLC (Programmable Logic Controller) with strong anti-interference capabilities as its primary control element, along with circuit breakers, power switches, an integrated single-chip microcomputer, and circuit protection devices such as motor drivers. The use of a removable controller 14 facilitates timely adjustment of equipment parameters during observation experiments, enhancing experimental convenience.

[0075] The polishing method of the rotating magnetic field magnetic fluid jet shear polishing device based on CFD simulation in the present invention has the following specific steps:

[0076] 1) Prepare a magnetic fluid polishing slurry consisting of 10% 10-micron silicon carbide (SiC) abrasive particles, 4% ferroferric oxide (Fe₃O₄) magnetic particles, 0.2% polyacrylate, 2% ethylene glycol, and deionized water. Pour the slurry into the mixing and stirring module of the fluid circulation system for stirring.

[0077] 2) Fix the workpiece to be polished on the fixture of the five-axis machine tool, and use the computer CNC numerical control system to adjust the position of the jet tool head so that the surface of the workpiece 8 is precisely aligned with the polishing range of the jet liquid column of the jet tool head.

[0078] 3) Set the jet pressure, jet time, and nozzle position. Adjust the rotating magnetic field strength (50-200 mT) and frequency (10-100 Hz) to control the liquid column viscosity and the rotation speed of the magnetic particles in the polishing fluid. Start the air compressor and spray the magnetic fluid polishing fluid through the double-layer nozzle structure. The inner nozzle forms the jet liquid column, and the outer nozzle introduces the compressed air flow.

[0079] 4) The supply metering pump in the fluid circulation system is activated to deliver the polishing fluid from the mixing tank to the jet tool head after stabilizing the pressure through the damper and back-pressure valve. The polishing fluid then forms a linear jet through the jet nozzle of the jet tool head and is sprayed onto the inner wall of the workpiece. The polishing fluid then flows to a collection area at the bottom of the workpiece and is recovered by the recovery metering pump and returned to the mixing tank.

[0080] 5) Analyze the flow field distribution and material removal profile of the jet liquid column through CFD simulation technology, and adjust the magnetic field intensity, jet pressure and magnetic field rotation speed to optimize the polishing accuracy and efficiency.

[0081] Among them, Figure 3 As shown, CFD simulation technology is a multi-model coupling simulation. It couples the multiphase flow VOF model, discrete phase DPM model, erosion Oka model, and viscosity model, and optimizes them to simplify the calculation complexity and improve the operation speed. The specific model optimization steps are as follows:

[0082] S1: Use SolidWorks modeling software to build a model of the polishing condition, and import the polishing condition simulation model into the SpaceClaim module in Ansys-Workbench to obtain a simulation model of the fluid domain;

[0083] S2: Use Meshing in Ansys Workbench to perform tetrahedral meshing on the simulation model of the fluid domain;

[0084] S3: Use Fluent in Ansys Workbench to perform computational fluid dynamics calculations on the simulation model of the fluid domain;

[0085] S3.1 sets the turbulence model of the simulated fluid and sets the viscosity of the magnetic fluid under the action of the magnetic field in the viscosity model.

[0086] In the turbulence model setup, a shear stress transport (SST) model based on the k-ω turbulence model was used to represent the high Reynolds number turbulent flow that occurs within the inner and outer regions of the inner boundary layer during the jet process. In the viscosity model, the liquid viscosity measured with a viscometer under a fixed magnetic field strength was used for calculations to improve calculation speed and accuracy while avoiding the introduction of magnetic field simulation, which would affect the accuracy and efficiency of the calculated results.

[0087] S3.2 uses the multiphase flow VOF model to model continuous multiphase fluid.

[0088] In the multiphase flow VOF model, two items of water and air are set. The liquid phase is used to simulate the polishing liquid, and the gas phase is used to simulate the protective gas ejected from the outside of the double-layer nozzle structure jet tool head.

[0089] S3.3 uses the discrete phase model DPM to perform transient three-dimensional simulation of abrasive particles and predict the motion trajectory of the particles.

[0090] In the discrete phase DPM model setting, the particle-particle interaction can be ignored, and a one-way coupling is used between the liquid and solid phase motions, considering only the effect of the fluid on the abrasive motion. The particle turbulence diffusion model requires the use of a random walk model to calculate the effect of turbulent velocity fluctuations on the particle trajectory. The resistance to the particles dominates the formula. Other forces such as gravity, Brownian force, and Saffman lift are much smaller than the resistance to the particles, so they can be ignored during the simulation process. When calculating the discrete phase model, the motion trajectory of the particle particles in the jet process is obtained by integrating the formula with the discrete phase time step. The specific calculation is shown in Formula 2:

[0091]

[0092] Where v p is the particle velocity, t is the time, v is the fluid velocity, ρ p is the particle density, ρ is the fluid density, F D is the resistance per unit particle mass during the jet process, g is the acceleration due to gravity, and F is the additional acceleration per unit particle mass.

[0093] The resistance force F on the particle D The value of depends on the Reynolds number of the fluid flow and the difference between the fluid flow and particle velocities. The specific calculation is shown in Formula 3:

[0094]

[0095] Where d p is the abrasive particle diameter, C D is the resistance coefficient, μ is the fluid dynamic viscosity, R e is the relative Reynolds number, ρp is the particle density. D is the resistance per unit particle mass during the jet process.

[0096] The calculation of the relative Reynolds number Re during the jet process is shown in Formula 4:

[0097]

[0098] Where d p is the abrasive particle diameter, μ is the fluid dynamic viscosity, ρ p is the particle density, v p is the particle velocity and v is the fluid velocity.

[0099] S3.4 uses the erosion model to perform erosion calculations on the simulation model.

[0100] The Oka erosion model is set up. Based on the discrete phase model (DPM), the computational erosion model is enabled. The Oka erosion model is used to calculate the material removal rate and predict deterministic surface shape control. Erosion damage at different angles (E(δ)) can be expressed using the formulas shown in Equations 5-8, taking into account the material properties of the particles and sample, as well as the impact conditions.

[0101]

[0102] In the formula is the erosion rate when particles impact at a vertical angle, which represents the unit volume of material lost per unit mass of particles (mm3 / kg) impacting the surface; it is composed of two trigonometric functions and the initial hardness of the material; E(δ) is the erosion caused by particles impacting at an angle of δ, and g(δ) is the impact angle function when the particles impact at an angle of δ; n1 and n2 are indices that can be determined by the impact velocity and other impact conditions (material properties, particle properties, etc.); Hv is the initial Vickers hardness of the workpiece. m is the particle movement speed; d m is the abrasive particle diameter; v ref ,d ref represent the reference speed and reference diameter respectively; k i Represents the particle property factor, and the index is different for different abrasive particles.

[0103] S3.5 sets the sliding grid to simulate the rotating magnetic fluid under the action of a magnetic field.

[0104] In the sliding mesh setting, the sliding mesh is used to simulate the self-rotation of the liquid under the action of the magnetic field. Under the action of the rotating magnetic field, the self-rotation speed of the liquid is consistent with the rotation speed of the magnetic field, that is, the magnetic field rotation speed is used to simulate the self-rotation of the liquid under the action of the magnetic field. The motion of any point in the domain is defined by the rate of change of the position vector with time. to describe, and in the rigid body rotation of the grid, the velocity is constant; the rate of change The calculation of is shown in formula 9:

[0105]

[0106] In the formula is the rate of change of the position vector over time; To describe the rotation speed of the grid; is the position of any point in the domain; is the velocity field, representing the velocity of each point in the moving mesh.

[0107] S4: Use the post-processing software Tecplot to analyze the simulation results.

[0108] like Figure 4 As shown in the figure, the polishing effect of traditional jet polishing and rotating magnetic field magnetofluid jet shear polishing is compared. Among them, 1 is the traditional jet polishing effect diagram, 2 is the polishing effect diagram of rotating magnetic field magnetofluid jet shear polishing, and 3 is the material removal profile diagram of polished curved surface parts. It can be seen from the CFD simulation that due to the addition of the rotating magnetic field, magnetofluid shear polishing is introduced on the basis of jet polishing to remove material, so the rotating magnetic field magnetofluid jet shear polishing has a higher material removal efficiency than the traditional jet polishing. In addition, due to the addition of the rotating magnetic field and the double-layer jet outlet, the stability of the liquid column can be improved, so the rotating magnetic field magnetofluid jet shear polishing has a more stable material removal profile. The present invention effectively solves the problems of low material removal efficiency, poor liquid column stability and difficult to control shear force distribution in traditional jet polishing, and at the same time achieves the goal of deterministic polishing, providing an innovative solution for the precision machining of complex curved surfaces and high-precision surfaces, and is particularly suitable for the fields of optics, aerospace and mold manufacturing.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polishing method for a magnetic fluid jet shear polishing device based on CFD simulation, wherein the device comprises an industrial five-axis machine tool (6), a fluid circulation system, a jet polishing module, and a computer CNC numerical control system; the jet polishing module and a workpiece (8) to be processed are respectively mounted on a workbench and a tool mounting seat of the industrial five-axis machine tool (6), and can realize five-axis polishing processing under the control of the computer CNC numerical control system; the method is characterized in that: The jet polishing module comprises a jet tool head (7), a rotating magnetic field generating device and an air compressor (15); the jet tool head (7) comprises an outer mounting sleeve and an inner jet nozzle (701); the polishing liquid is sprayed onto the workpiece (8) through the jet nozzle (701); a gas spray chamber (702) is provided between the mounting sleeve and the jet nozzle (701), and can form a stable airflow around the polishing liquid sprayed by the jet nozzle (701) in cooperation with the air compressor (15); The rotating magnetic field generating device is used to adjust the self-rotation speed of the magnetic particles in the sprayed polishing liquid and change the viscosity of the polishing liquid; The fluid circulation system is used to provide polishing liquid to the jet polishing module, and to recover the polishing liquid after the jet is completed, and output the recovered polishing liquid to the jet polishing module to form a circulation process of the polishing liquid; The specific steps of the polishing method of the device are as follows: 1) preparing a magnetic fluid polishing slurry, wherein the magnetic fluid polishing slurry is prepared by mixing 10% silicon carbide abrasive particles with a particle size of 10 microns, 4% ferroferric oxide magnetic particles, 0.2% polyacrylate, 2% ethylene glycol, and deionized water; 2) Fixing the workpiece (8) to be processed on the fixture of the five-axis machine tool, and adjusting the position of the output port of the jet polishing module through the computer CNC numerical control system so that the surface of the workpiece (8) to be processed is accurately aligned with the polishing range of the output jet liquid column; 3) Setting the jet pressure, jet time, and polishing path of the jet polishing module; adjusting the rotating magnetic field strength and frequency to control the viscosity of the liquid column and the self-rotation speed of the magnetic particles in the polishing liquid; Start the air compressor and spray the magnetic fluid polishing liquid through the jet tool head. The inner jet nozzle forms a jet liquid column, and the outer layer is introduced with compressed air flow. 4) starting a fluid circulation system, which recovers the polishing liquid after the jet is completed and outputs the recovered polishing liquid to the jet tool head, through which the cyclic polishing process is performed; 5) Analyze the flow field distribution and material removal profile of the jet liquid column through CFD simulation technology, and adjust the magnetic field intensity, jet pressure and magnetic field rotation speed; The CFD simulation technology uses a multi-model coupling simulation; the multiphase flow VOF model, the discrete phase DPM model, the erosion Oka model, and the viscosity model are coupled and optimized. The specific optimization steps are as follows: S1: Use SolidWorks modeling software to build a model of the polishing condition, and import the polishing condition simulation model into the SpaceClaim module in Ansys-Workbench to obtain a simulation model of the fluid domain; S2: Use Meshing in Ansys Workbench to perform tetrahedral meshing on the simulation model of the fluid domain; S3: Use Fluent in Ansys Workbench to perform computational fluid dynamics calculations on the simulation model of the fluid domain; S3.1 sets the turbulence model of the simulated fluid and sets the viscosity of the magnetic fluid under the action of the magnetic field in the viscosity model; S3.2 Modeling of continuous multiphase fluid using the multiphase VOF model; S3.3 uses the discrete phase model (DPM) to perform transient three-dimensional simulation of abrasive particles and predict the particle trajectory; S3.4 Use the erosion model to perform erosion calculations on the simulation model; S3.5 sets up a sliding grid for simulating the rotating magnetic fluid under the action of a magnetic field; S4: Use the post-processing software Tecplot to analyze the simulation results; In the turbulence model setting, the shear stress transport SST model based on the k-ω turbulence model is used to represent the turbulent flow with large Reynolds numbers that occurs in the inner region of the inner boundary layer and the outer region of the boundary layer during the jet process; In the viscosity model, the viscosity of the liquid measured by a viscometer under a fixed magnetic field strength is used for setting calculations.

2. The polishing method of a magnetic fluid jet shear polishing device based on CFD simulation according to claim 1, characterized in that: The rotating magnetic field generating device comprises a circuit connector (704) and an electromagnet (703); the electromagnet (703) is fixed on the jet tool head (7) and is located below the jet outlet in the jet nozzle (701); a plurality of coils are provided on the electromagnet (703); each coil group is uniformly distributed along the axial direction of the electromagnet (703); each coil group is energized through the circuit connector; and magnetic particles in the polishing liquid can be arranged along the magnetic lines of force under the action of the magnetic field to form a chain or columnar structure.

3. The polishing method of the magnetic fluid jet shear polishing device based on CFD simulation according to claim 2, characterized in that: The magnetic particles in the polishing liquid can rotate at a speed of 10-100 revolutions per second under the action of a magnetic field, and the viscosity is 5-200 mPa·s.

4. The polishing method of a magnetic fluid jet shear polishing device based on CFD simulation according to claim 1, characterized in that: The fluid circulation system comprises a mixing and stirring module and a circulation conveying module; a liquid discharge port (10) is provided at the bottom of the processing chamber; the input end of the mixing and stirring module is connected to the liquid discharge port (10) of the processing chamber via a water pipe, and is used to stir the output polishing liquid; the input end of the circulation conveying module is connected to the output end of the mixing and stirring module, and can convey the polishing liquid that has been stirred and mixed to the output of the jet polishing module, thereby realizing the recycling of the polishing liquid.

5. The polishing method of a magnetic fluid jet shear polishing device based on CFD simulation according to claim 1, characterized in that: In the multiphase flow VOF model, two items of water and air are set, the liquid phase is used to simulate the polishing liquid, and the gas phase is used to simulate the protective gas ejected from the outside of the jet tool head with a double-layer nozzle structure.

6. The polishing method of a magnetic fluid jet shear polishing device based on CFD simulation according to claim 1, characterized in that: In the discrete phase DPM model setting, one-way coupling is adopted between the liquid phase and the solid phase motion; the particle turbulence diffusion model adopts the random walk model; when calculating the discrete phase model, the motion trajectory of the particle in the jet process is obtained by integrating the formula with the discrete phase time step number. The specific calculation is shown in Formula 2: Where v p is the particle velocity, t is the time, v is the fluid velocity, ρ p is the particle density, ρ is the fluid density, F D is the resistance per unit particle mass during the jet process, g is the acceleration due to gravity, and F is the additional acceleration per unit particle mass; The resistance force F on the particle D The value of depends on the Reynolds number of the fluid flow and the difference between the fluid flow and particle velocities. The specific calculation is shown in Formula 3: Where d p is the abrasive particle diameter, C D is the resistance coefficient, μ is the fluid dynamic viscosity, R e is the relative Reynolds number, ρ p is the particle density; F D is the resistance per unit particle mass during the jet process; The calculation of the relative Reynolds number Re during the jet process is shown in Formula 4: Where d p is the abrasive particle diameter, μ is the fluid dynamic viscosity, ρ p is the particle density, v p is the particle velocity, v is the fluid velocity; S3.4 Use the erosion model to perform erosion calculations on the simulation model; Erosion Oka model setting: Based on the discrete phase model DPM, the calculation erosion model is opened and the Oka erosion model is used to calculate the material removal rate to achieve the prediction of deterministic surface control; Involving the material properties of the particles and samples as well as the impact conditions, the erosion damage at different angles E(δ) is expressed as shown in Formula 5-8; In the formula is the erosion rate when particles impact at a vertical angle, which represents the unit volume of material lost per unit mass of particles (mm3 / kg) impacting the surface; it is composed of two trigonometric functions and the initial hardness of the material; E(δ) is the erosion caused by particles impacting at an angle δ, and g(δ) is the impact angle function when the particles impact at an angle δ; n1 and n2 are exponents determined by the impact velocity and other impact conditions; Hv is the initial Vickers hardness of the workpiece; v m is the particle movement speed; d m is the abrasive particle diameter; v ref ,d ref represent the reference speed and reference diameter respectively; k i Represents the particle property factor.

7. The polishing method of a magnetic fluid jet shear polishing device based on CFD simulation according to claim 1, characterized in that: In the sliding grid setting, a sliding grid is used to simulate the self-rotation of the liquid under the action of the magnetic field; under the action of the magnetic field, the self-rotation speed of the liquid is consistent with the rotation speed of the magnetic field, that is, the magnetic field rotation speed is used for setting to simulate the self-rotation of the liquid under the action of the magnetic field; the motion of any point in the definition domain is determined by the rate of change of the position vector with time. to describe, and in the rigid body rotation of the grid, the velocity is constant; the rate of change The calculation of is shown in formula 9: In the formula is the rate of change of the position vector over time; To describe the rotation speed of the grid; is the position of any point in the domain; is the velocity field, representing the velocity of each point in the moving mesh.

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