Magnetic fluid jet flow shearing and polishing device and method based on CFD simulation

Abstract

The invention discloses a CFD (computational fluid dynamics) simulation-based magnetofluid jet shear polishing device and method. The device comprises an industrial five-axis machine tool, a fluid circulation system, a jet polishing module and a CNC (computer numerical control) system. The jet flow polishing module and the machined workpiece 8 are installed on a workbench and a tool installation base of the industrial five-axis machine tool respectively, and five-axis polishing machining can be achieved under the control of a CNC numerical control system. The jet flow polishing module comprises a jet flow tool head and a rotating magnetic field generating device. The rotating magnetic field is applied to the jet flow outlet of the jet flow tool head, ferroferric oxide particles in the polishing solution are driven to be arranged in the magnetic line direction to form a chain structure, the viscosity of the polishing solution is remarkably improved, and the polishing solution is endowed with the high-speed self-rotating motion characteristic. High-speed rotation and enhanced viscosity of the liquid column generate stronger shearing force, so that efficient material removal on the surface of a workpiece is realized.

Description

Technical Field

[0001] The 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 link in improving the performance and appearance quality of parts, especially in high-tech fields such as optical components, aerospace parts and complex mold manufacturing, where the demand for efficient and high-precision surface processing technology is particularly urgent. However, traditional polishing methods are gradually showing their shortcomings in terms of efficiency and precision, especially when processing complex curved surfaces and surfaces with high precision requirements, it is difficult to balance material removal efficiency and surface quality.

[0003] Traditional mechanical polishing removes material by applying pressure to the workpiece surface with rigid abrasive tools. Although the method is mature, it is easy to introduce surface scratches, local over-processing and thermal damage, and has poor adaptability to complex geometric shapes. Although chemical mechanical polishing (CMP) performs well in material removal at the microscopic level, it is inefficient and has poor adaptability to hard material processing. At the same time, it requires the use of chemical polishing fluid, which brings about environmental pollution problems.

[0004] In recent years, jet polishing technology has gradually attracted attention due to its non-contact processing characteristics. By acting on the workpiece surface with a high-speed liquid column, it not only avoids the potential damage to the surface caused by rigid tool contact, but also improves the adaptability to complex curved surfaces. However, the existing jet polishing technology still has many problems, such as low material removal efficiency, poor stability of the jet liquid column, and uneven removal distribution. This is mainly because the viscosity of traditional jet polishing fluid is low, and it is difficult to maintain the integrity of the liquid column in high-speed flow. At the same time, 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 prior art, 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] In the first aspect, a magnetic fluid jet shear polishing device based on CFD simulation includes 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 to be processed are respectively installed 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.

[0008] The jet polishing module includes a jet tool head, a rotating magnetic field generating device and an air compressor. The jet tool head includes an outer mounting sleeve and an inner jet nozzle. The polishing liquid is sprayed onto the workpiece through the jet nozzle. A gas spray chamber is provided between the mounting sleeve and the jet nozzle, which can form a stable airflow around the polishing liquid sprayed by the jet nozzle in cooperation with the air compressor. 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.

[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 on the jet tool head and is located below the jet outlet in the jet nozzle to prevent the high-speed rotating high-viscosity polishing liquid from wearing the inner wall surface of the jet outlet. There are multiple groups of coils on the electromagnet. Each group of coils is evenly distributed along the circumferential direction of the electromagnet axis. Each group of coils is energized through the circuit connector. The 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.

[0011] Furthermore, the fluid circulation system includes a mixing and stirring module and a circulation conveying module. A discharge port is provided at the bottom of the processing chamber. The input end of the mixing and stirring module is connected to the discharge port of the processing chamber through 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.

[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 liquid is prepared, wherein the magnetic fluid polishing liquid is mixed with 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.

[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 of the jet polishing module. Adjust 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, 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.

[0017] 4) Start the supply metering pump in the fluid circulation system, and deliver the polishing liquid from the stirring tank to the jet tool head after stabilizing the pressure through the damper and back pressure valve, and form a linear jet through the jet nozzle of the jet tool head and spray it onto the inner wall of the workpiece. The polishing liquid then flows to the collection area at the bottom of the workpiece, and is recovered into the stirring tank through the recovery metering pump.

[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 adopts 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:

[0020] S1: A model of the polishing condition is established by using SolidWorks modeling software, and the simulation model of the polishing condition is imported 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 discrete phase model DPM to perform transient three-dimensional simulation of abrasive particles and predict the motion trajectory of 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 magnetic field.

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

[0029] Furthermore, in the turbulence model setting, a shear stress transport SST model based on the k-ω turbulence model is used to represent the turbulent flow with a large Reynolds number 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 liquid viscosity measured by a viscometer under a fixed magnetic field strength is used for setting calculations.

[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, one-way coupling is used between the liquid phase and the solid phase. The particle turbulence diffusion model adopts a random walk model. 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:

[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 in 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 velocity. The specific calculation is shown in Formula 3:

[0035]

[0036] Where d p is the abrasive particle diameter, C D is the drag 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 erosion Oka model is set up. 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 particles and samples and the impact conditions, the erosion damage at different angles E(δ can be expressed by formulas as shown in Formulas 5-8.

[0042]

[0043] In the formula is the erosion rate when the particle impacts at a vertical angle, which represents the unit volume of material lost per unit mass of the particle (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 the particle impacting at an angle of δ, and g(δ) is the impact angle function when the particle impacts at an angle of δ; n 1 , n 2 An index 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, the sliding grid 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 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 over 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. 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 form a chain structure along the direction of the magnetic lines of force, significantly improve the viscosity of the polishing liquid and give it self-rotating motion characteristics. The high-speed rotation and enhanced viscosity of the liquid column produce a stronger shear force, enabling efficient material removal on the workpiece surface. At the same time, by combining CFD simulation technology to optimize the flow field behavior and shear force distribution of the jet liquid column, the processing efficiency and accuracy are further improved.

[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 introduced with 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 It is a structural schematic diagram 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. rotation 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 is necessary to understand 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, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0056] The present invention will be further described below in conjunction with 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 the 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 component 601, a Y-axis displacement component 602, a rotary drive component 604, a lifting and adjusting component 603, and an angle adjustment component 605. Among them, the X-axis displacement component 601 and the Y-axis displacement component 602 are both installed on the frame, and are used to drive the processed workpiece 8 to move in both directions along the horizontal direction. The rotary drive component 604 is installed on the moving end of the Y-axis displacement component 602, and is used to drive the processed workpiece 8 to rotate. A workpiece clamp 9 is provided at the center of the rotary drive component 604, which can clamp and fix the processed workpiece 8 to avoid the position of the processed workpiece 8 from shifting during the processing. The lifting and adjusting component 603 is arranged on the top of the frame, and is used to drive the jet polishing module to be lifted and adjusted. The angle adjustment component 605 is installed on the moving end of the lifting and adjusting component 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 is 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 provided between the mounting sleeve and the jet nozzle 701. An air intake pipe connected to the gas spray chamber 702 is provided on the mounting sleeve. The outer end of the air intake pipe is connected to the air compressor 15 through an air pipe.

[0060] When working, the air compressor 15 compresses air and outputs it from the output port of the air compressor 15. The output gas is introduced into the gas spray chamber 702 through the air pipe and the air inlet pipe, and is ejected from the gas nozzle at the bottom of the gas spray chamber 702, forming a stable high-pressure airflow 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 spray chamber 702 is an annular structure. The airflow direction in the gas spray chamber 702 is consistent with the jet direction, and the airflow speed can be adjusted to match the flow rate of the liquid jet. By introducing a stable airflow, the internal jet is stabilized to prevent the jet from having a jet breakup point too early, and by forming a protective layer to reduce the impact of external disturbances on the liquid column, the stability of the jet is improved. The pressure of the magnetic fluid polishing liquid sprayed by the jet nozzle 701 is 0-15bar.

[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 comprises a mounting bracket, a circuit connector 704 and an electromagnet 703. The electromagnet 703 is fixed on the mounting sleeve of the fluidic tool head 7 through the mounting bracket.

[0063] In this embodiment, the electromagnet 703 is located below the jet outlet in the jet nozzle 701, which can prevent the magnetic fluid polishing liquid from forming shear polishing inside the jet nozzle 701 under the influence of the rotating magnetic field, thereby damaging the jet outlet of the jet nozzle 701. There are 6 groups of coils on the electromagnet 703. Each group of coils is evenly distributed along the circumferential direction of the axial direction of the electromagnet 703, and each group of coils is evenly spaced 60°.

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

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

[0066] η m =η 0 ·(1+Φ·μ r ·B 2 ) (1)

[0067] Where η m is the viscosity under the action of magnetic field (unit: mPa·s); η 0 is the basic viscosity in the absence of a 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 opened 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. A water outlet pipe is arranged at the output end of the recovery metering pump 11. 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, thereby causing the concentration of the magnetic fluid polishing liquid to be reduced, affecting the polishing efficiency and causing the problem of pipeline blockage.

[0070] The circulation and conveying module includes a supply metering pump 1, a liquid inlet pipeline and a pipeline protection component. Among them, a return pipeline 16 is provided between the output end of the stirring tank and the input end of the supply metering pump 1. The output end of the supply metering pump 1 is connected to the jet tool head 7 through the liquid inlet pipeline. The pipeline protection component is installed on the liquid inlet pipeline to protect the liquid inlet pipeline and prevent the liquid inlet pipeline from being damaged due to excessive hydraulic pressure in the liquid inlet pipeline.

[0071] The pipeline protection component includes a damper 2, a back pressure valve 3, a pressure gauge 4 and a pressure regulating valve 5 connected in sequence. Among them, the input end of the damper 2 is connected to the output end of the supply metering pump 1; the output end is connected to the liquid inlet pipeline, and can form a magnetic fluid polishing liquid jet with stable pressure in the liquid inlet pipeline with the cooperation of the back pressure valve 3. The pressure gauge 4 is used to monitor the pressure of the magnetic fluid polishing liquid jet in the liquid inlet pipeline in real time. The pressure regulating valve 5 can controllably adjust the pressure of the magnetic fluid polishing liquid jet in the liquid inlet pipeline, so that the pressure regulation of the magnetic fluid polishing liquid jet can achieve a closed loop.

[0072] When in use, the magnetic fluid polishing liquid output from the stirring tank is received by the supply metering pump 1, and is delivered to one side of the liquid inlet pipe. The magnetic fluid polishing liquid flows through the damper 2, back pressure valve 3, pressure gauge 4 and pressure regulating valve 5 on the liquid inlet pipe, reaches the set pressure, and is sprayed onto the polished workpiece through the jet tool head 7 to polish the polished workpiece. The magnetic fluid polishing liquid that flows to the bottom of the processing chamber is discharged from the drain port 10 of the processing chamber, and flows back to the stirring tank through the water supply pipe and the recovery metering pump 11.

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

[0074] In this embodiment, the computer numerical control system includes an electric control cabinet 13 and a controller 14. The electric control cabinet 13 uses a PLC with strong anti-interference as the main control element, as well as circuit protection devices such as circuit breakers, power switches, integrated single-chip microcomputers, and motor drivers. The use of a movable controller 14 can facilitate timely adjustment of equipment parameters during the observation experiment, thereby improving the convenience of the experiment.

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

[0076] 1) A magnetic fluid polishing liquid is prepared, which is composed of 10% silicon carbide (SiC) abrasive particles with a particle size of 10 microns, 4% ferrosoferric oxide (Fe 3 O 4 ) magnetic particles, 0.2% polyacrylate, 2% ethylene glycol and deionized water are mixed and poured into the mixing and stirring module in the fluid circulation system for stirring.

[0077] 2) Fix the workpiece to be polished on the fixture of the five-axis machine tool, and adjust the position of the jet tool head by 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 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 (50-200mT) and frequency (10-100Hz) 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 double-layer nozzle structure. The inner nozzle forms a jet liquid column, and the outer nozzle is fed with compressed air.

[0079] 4) Start the supply metering pump in the fluid circulation system, and deliver the polishing liquid from the stirring tank to the jet tool head after stabilizing the pressure through the damper and back pressure valve, and form a linear jet through the jet nozzle of the jet tool head and spray it onto the inner wall of the workpiece. The polishing liquid then flows to the collection area at the bottom of the workpiece, and is recovered into the stirring tank through the recovery metering pump.

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

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

[0082] S1: A model of the polishing condition is established by using SolidWorks modeling software, and the simulation model of the polishing condition is imported 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 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 liquid viscosity measured by the viscometer under a fixed magnetic field strength is used for setting calculations to improve the calculation speed and accuracy; avoid introducing magnetic field simulation to affect the accuracy and efficiency of the result calculation.

[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 discrete phase model DPM to perform transient three-dimensional simulation of abrasive particles and predict the motion trajectory of 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 particle trajectories. The resistance experienced by the particles dominates the formula. Other forces such as gravity, Brownian force, and Saffman lift are much smaller than the resistance experienced by the particles, so they can be ignored during the simulation. 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 in 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 velocity. The specific calculation is shown in Formula 3:

[0094]

[0095] Where dp is the abrasive particle diameter, C D is the drag 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.

[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 erosion Oka model is set up. 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 particles and samples and the impact conditions, the erosion damage at different angles E(δ can be expressed by formulas as shown in Formulas 5-8.

[0101]

[0102] In the formula is the erosion rate when the particle impacts at a vertical angle, which represents the unit volume of material lost per unit mass of the particle (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 the particle impacting at an angle of δ, and g(δ) is the impact angle function when the particle impacts at an angle of δ; n 1 , n 2 An index 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 different abrasive particles have different indices.

[0103] S3.5 sets the sliding grid to simulate the rotating magnetic fluid under the action of 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 liquid self-rotation speed is consistent with the magnetic field rotation speed, 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 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:

[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, the polishing effect of traditional jet polishing and rotating magnetic field magnetic fluid 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 magnetic fluid 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, magnetic fluid shear polishing is introduced on the basis of jet polishing to remove materials. Therefore, the rotating magnetic field magnetic fluid 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 magnetic fluid 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, which is particularly suitable for optics, aerospace and mold manufacturing and other fields.

[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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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 magnetic fluid jet shear polishing device based on CFD simulation, comprising 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 the workpiece (8) to be processed are respectively installed 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 characteristics are: 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 a workpiece (8) through the jet nozzle (701); a gas spray chamber (702) is provided between the mounting sleeve and the jet nozzle (701), and a stable airflow can be formed 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, thereby forming a circulation process of the polishing liquid.

2. The magnetic fluid jet shearing and 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 a jet tool head (7) and is located below a jet outlet in a jet nozzle (701); a plurality of coils are provided on the electromagnet (703); each group of coils is uniformly distributed along the axial circumference of the electromagnet (703); each group of coils is energized via the circuit connector; and magnetic particles in the polishing liquid can be arranged along magnetic lines of force under the action of a magnetic field to form a chain-like or columnar structure.

3. The magnetic fluid jet shearing and polishing device based on CFD simulation according to claim 2 is 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 magnetic fluid jet shearing and 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 supply 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 jet polishing module for output, thereby realizing the circulation 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: The specific steps are as follows: 1) preparing a magnetic fluid polishing liquid, wherein the magnetic fluid polishing liquid is prepared by mixing 10% of silicon carbide abrasive particles with a particle size of 10 microns, 4% of ferroferric oxide magnetic particles, 0.2% of polyacrylate, 2% of 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 intensity and frequency of the rotating magnetic field 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 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 introduced with compressed air flow; 4) starting a fluid circulation system, which recycles the polishing liquid after the jet is completed, and outputs the recovered polishing liquid to the jet tool head, and performs a cyclic polishing process through the jet tool head; 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.

6. The polishing method of the magnetic fluid jet shear polishing device based on CFD simulation according to claim 5 is characterized in that: The CFD simulation technology adopts 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: A model of the polishing condition is established by using SolidWorks modeling software, and the simulation model of the polishing condition is imported 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 continuous multiphase fluid using multiphase flow VOF model; S3.3 uses discrete phase model DPM to perform transient three-dimensional simulation of abrasive particles and predict the movement trajectory of particles; S3.4 uses the erosion model to perform erosion calculation on the simulation model; S3.5 sets the sliding grid to simulate the self-rotating magnetic fluid under the action of magnetic field; S4: Use the post-processing software Tecplot to analyze the simulation results.

7. The polishing method of the magnetic fluid jet shear polishing device based on CFD simulation according to claim 6 is characterized in that: In the turbulence model setting, a shear stress transport SST model based on the k-ω turbulence model is used to represent the turbulent flow with a large Reynolds number occurring 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.

8. The polishing method of a magnetic fluid jet shear polishing device based on CFD simulation according to claim 6, 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.

9. The polishing method of a magnetic fluid jet shear polishing device based on CFD simulation according to claim 6, 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 a random walk model; 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 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 in 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 velocity. The specific calculation is shown in Formula 3: Where d p is the abrasive particle diameter, C D is the drag 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 in 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 uses the erosion model to perform erosion calculation 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 can be expressed by formulas as shown in Formulas 5-8; In the formula is the erosion rate when particles impact at a vertical angle, which indicates 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 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.

10. The polishing method of a magnetic fluid jet shear polishing device based on CFD simulation according to claim 6, 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 movement 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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