Stepwise grinding-polishing method based on shear rheological effect of non-Newtonian fluid

Abstract

A step-by-step grinding and polishing method based on the shear rheological effect of a non-Newtonian fluid comprises the following steps: (1) mixing abrasives and additives into a non-Newtonian fluid base liquid with a shear rheological effect, stirring evenly, preparing a shear rheological grinding and polishing liquid, and adding the liquid to a machine tool grinding station; (2) in the fine grinding stage after completing conventional rough grinding and semi-fine grinding, providing a shear rheological grinding and polishing liquid to the grinding zone from the cutting end of the grinding wheel along the direction of the grinding wheel linear velocity; (3) setting the grinding depth to be greater than zero to achieve low-damage grinding of the workpiece surface; (4) setting the grinding depth to be equal to zero, and performing a grinding and polishing composite process on the grinding surface; (5) setting the grinding wheel and the workpiece to a non-contact state, performing shear rheological polishing on the grinding surface, and controlling the material removal rate of each point on the surface during the polishing process by adjusting the rheological properties of the grinding and polishing liquid, the grinding wheel linear velocity, the workpiece feed speed, and the grinding wheel-workpiece gap. The invention is easy to implement, has high processing efficiency, high precision, and strong practicality.

Description

Technical Field

[0001] The invention belongs to precision and ultra-precision machining technology, and relates to a step-by-step machining method capable of realizing low-damage grinding and in-situ flexible polishing of hard and brittle materials. Background Art

[0002] Grinding and polishing are two important links in the optical manufacturing process chain and are important technical means to achieve precision and ultra-precision processing of hard and brittle materials. The traditional grinding method of hard and brittle materials inevitably leaves a surface damage layer. The deeper grinding damage layer not only increases the subsequent polishing time, but is also extremely unfavorable to the surface shape control during the polishing process.

[0003] In order to reduce the surface damage of hard and brittle materials during grinding, domestic and foreign scholars have used a variety of methods to inhibit the initiation and expansion of cracks in hard and brittle materials during grinding, such as ELID grinding, ultrasonic vibration assisted grinding, chemical mechanical grinding, semi-fixed abrasive grinding, etc. ELID grinding technology reduces the damage of the machined surface by optimizing the grinding performance of the abrasive tool. This technology solves the wear and passivation problems of fine / ultrafine abrasive metal-based diamond grinding wheels during the grinding of hard and brittle materials, and realizes ultra-precision grinding of a series of hard and brittle materials such as glass and ceramics. The use of two-dimensional ultrasonic vibration method can reduce the damage of the grinding surface by improving the wear state of the grinding wheel, reducing the grinding force, and increasing the critical cutting depth. However, when ELID grinding is used for grinding the inner surface with a large aspect ratio, it is difficult to avoid interference between the electrode and the inner surface of the workpiece; ultrasonic vibration assisted grinding requires an additional vibration unit for the machine tool, the grinding speed is limited by the vibration period, and the vibration direction is complicated to control the deflection of the normal line of the grinding point during curved surface grinding. Chemical mechanical grinding technology uses the solid phase reaction between fixed abrasives and the processed material, combined with the mechanical removal of abrasives to achieve damage-free surface processing. Semi-fixed abrasive grinding has solved the problems of low processing efficiency of free abrasives and large surface damage caused by fixed abrasives to a certain extent. At present, it has achieved good results in the processing of materials such as single crystal silicon and sapphire. However, the material removal rate of chemical mechanical grinding and semi-fixed abrasive grinding is still low, about 1 to 3 μm / h, which is difficult to meet the requirements of precision grinding.

[0004] Among the flexible polishing methods that have good applicability to both flat and curved surfaces, the most studied ones are airbag polishing, abrasive jet polishing, magnetorheological polishing, and shear thickening polishing. The flexible polishing head of airbag polishing can automatically adapt to the curved surface shape of the workpiece, and the polishing efficiency can be controlled by adjusting the internal pressure of the airbag. Abrasive jet polishing uses the high-speed collision and shearing effect of abrasive particles on the workpiece surface to polish the workpiece surface by controlling parameters such as injection pressure, angle, and time. Magnetorheological polishing uses an external magnetic field to control the magnetorheological fluid to produce a flexible "polishing die" that matches the machined surface in the polishing area to remove materials. The shear thickening polishing process does not require an external auxiliary field, and has low requirements on the shape and material of the polishing tool. It can even achieve ultra-precision machining of complex curved surfaces through fluid dynamic pressure and friction without polishing tools. The above polishing methods can achieve controllable changes in the flexibility of the "polishing die" through air pressure, magnetic field, flow field, shear rate, etc., but shear thickening polishing does not require complex equipment and accessories, and the preparation cost of the polishing liquid is low, which is more conducive to achieving in-situ flexible polishing after low-damage grinding.

[0005] In the traditional manufacturing process, grinding and polishing are carried out on special machine tools respectively. The grinding machine tool achieves material removal by controlling the grinding depth, while the material removal in the polishing process is based on pressure control. Realizing the motion and material removal rate control of the polishing process on the grinding machine tool, completing the combination of low-damage grinding and in-situ flexible polishing, can reduce the clamping time and eliminate the secondary clamping error, which is a key problem that needs to be solved to further improve the overall processing efficiency of grinding and polishing. From various research reports at home and abroad, there are no reports on the use of non-Newtonian fluid shear rheological effect to assist in suppressing grinding surface damage and achieving in-situ flexible polishing. The low-damage grinding and in-situ flexible polishing involved in the present invention are feasible methods to improve the overall processing efficiency of grinding and polishing. Summary of the invention

[0006] In order to overcome the disadvantages of the prior art that the grinding surface of hard and brittle materials is severely damaged, resulting in a long subsequent polishing time, the present invention provides a step-by-step grinding-polishing method based on the shear rheological effect of non-Newtonian fluids.

[0007] The above-mentioned invention object is achieved through the following technical solutions:

[0008] A progressive grinding-polishing method based on the shear rheological effect of a non-Newtonian fluid, the method comprising the following steps:

[0009] (1) Abrasives and additives are mixed into a non-Newtonian fluid base liquid with a shear rheological effect, stirred evenly, to prepare a shear rheological polishing fluid, and added to a machine tool grinding fluid station;

[0010] (2) In the fine grinding stage after completing the conventional rough grinding and semi-fine grinding, a shear rheological polishing fluid is provided to the grinding zone along the linear speed direction of the grinding wheel from the cutting end of the grinding wheel to replace the conventional grinding fluid;

[0011] (3) The grinding depth is set to be greater than zero in the CNC program, and the grinding wheel linear speed is set according to the shear rheological curve of the polishing fluid to control the shear rheological effect of the polishing fluid, thereby increasing the fluid dynamic pressure field intensity in the wedge-shaped grinding zone and achieving low-damage grinding of the workpiece surface;

[0012] (4) The grinding depth is set to zero in the numerical control program, the grinding wheel linear speed is set according to the rheological curve of the shear rheological grinding and polishing fluid and the grinding process parameter range of the workpiece material, the shear rheological effect of the grinding and polishing fluid is controlled, and the grinding surface is subjected to a grinding-polishing composite process;

[0013] (5) The grinding wheel and the workpiece are set to a non-contact state in the CNC program, and the shear rheological polishing is performed on the grinding surface. The material removal rate at each point on the surface during the polishing process is controlled by adjusting the rheological properties of the polishing fluid, the grinding wheel linear speed, the workpiece feed speed, and the grinding wheel-workpiece gap.

[0014] Furthermore, during the step-by-step grinding and polishing process of step (3), step (4) and step (5), the shear rheological polishing fluid enters the wedge-shaped grinding zone from the cutting end of the grinding wheel along the linear velocity direction of the grinding wheel, and forms a fluid dynamic pressure field in the wedge-shaped grinding zone; the polishing fluid undergoes rheological effects under the shearing action of the grinding wheel, including shear thickening, shear solidification or shear expansion.

[0015] Furthermore, during the low-damage grinding process of step (3), the grinding wheel and the workpiece being ground are in contact, that is, the grinding depth is greater than zero and is 0 to 10 μm.

[0016] Preferably, low-damage grinding is achieved through the following three aspects:

[0017] 3.1) The rheological effect of shear rheology polishing fluid strengthens the fluid dynamic pressure field intensity in the wedge-shaped grinding zone, thereby increasing the hydrostatic pressure in the direction perpendicular to the shear plane of material removal during the grinding process, promoting the removal of the plastic domain of hard and brittle materials;

[0018] 3.2) The shear rheological polishing fluid flexibly holds the free abrasive particles, removes the grinding wheel binder material, and realizes online sharpening of the grinding wheel;

[0019] 3.3) The shear rheological polishing fluid flexibly holds the free abrasive particles and polishes the damaged layer on the grinding surface.

[0020] Furthermore, in step (4), the grinding depth is set to zero during the composite grinding and polishing process, the grinding wheel and the workpiece are in a quasi-contact state, and the actual grinding depth is equal to the residual height after the previous grinding.

[0021] Preferably, material removal during the composite grinding and polishing process is achieved through the following two aspects:

[0022] 4.1) Polishing, material removal is due to elastic deformation of the workpiece-tool system;

[0023] 4.2) The shear rheological polishing fluid flexibly holds the free abrasive particles and polishes the damaged layer on the grinding surface.

[0024] Furthermore, in step (5), the grinding wheel and the workpiece are in a non-contact state, and the distance between the grinding wheel and the workpiece is greater than zero and is 0 to 5 mm.

[0025] Preferably, material removal is achieved in the following manner: the shear rheological polishing fluid flexibly holds the free abrasive particles and polishes the grinding surface in the fluid dynamic pressure field.

[0026] Preferably, the non-Newtonian fluid base liquid having shear rheological effect is one of the following: a non-Newtonian fluid composed of polyethylene glycol and silicon dioxide particles, a non-Newtonian fluid composed of a polyhydroxy polymer and water, and a non-Newtonian fluid composed of polymethyl methacrylate and glycerol.

[0027] The non-Newtonian fluid base liquid accounts for 50% to 95% of the mass fraction of the polishing fluid.

[0028] The abrasive is one of the following or a mixture of two or more thereof: diamond, cubic boron nitride, silicon nitride, silicon carbide, boron carbide, aluminum oxide, silicon oxide, zirconium oxide, cerium oxide, chromium oxide, iron oxide, and magnesium oxide.

[0029] The particle size of the abrasive is in the range of 0.5-10 μm, accounting for 5% to 50% of the mass fraction of the polishing liquid.

[0030] The additives include one or more of the following: dispersants, surfactants, pH regulators, and chemical active agents.

[0031] The content of the additive in the shear rheological polishing fluid is less than 5%.

[0032] The technical concept of the present invention is to replace the traditional grinding fluid with a non-Newtonian fluid grinding and polishing fluid, control the step-by-step change of the "contact-quasi-contact-non-contact" state between the grinding wheel and the workpiece, and use the shear rheological effect of the grinding and polishing fluid to sequentially realize "low-damage grinding-compound grinding and polishing-in-situ flexible polishing" to efficiently obtain a nearly damage-free surface.

[0033] The beneficial effects of the present invention are mainly manifested in: based on the shear rheological effect of non-Newtonian fluid, low-damage grinding and polishing of hard and brittle materials are achieved in a step-by-step manner, with simple process, low cost and easy use. The present invention can be used for precision and ultra-precision machining of optical surfaces of hard and brittle materials. The purpose of the present invention is to provide a step-by-step grinding and polishing method based on the shear rheological effect of non-Newtonian fluid. The technical core of the present invention is to replace the traditional grinding fluid with a non-Newtonian fluid grinding and polishing fluid, control the step-by-step change of the "contact-quasi-contact-non-contact" state between the grinding wheel and the workpiece, and use the shear rheological effect of the grinding and polishing fluid to sequentially achieve "low-damage grinding-compound grinding and polishing-in-situ flexible polishing" to efficiently obtain a nearly damage-free surface. The present invention is easy to implement, has high machining efficiency, high precision and strong practicality. The method can obtain an optical surface of a hard and brittle material with high surface accuracy and high surface integrity. The advantages of the present invention are:

[0034] 1) The three processes of "low-damage grinding-compound grinding and polishing-in-situ flexible polishing" are completed in a single clamping step-by-step manner, which is beneficial to improving the overall processing efficiency and eliminating the processing surface errors caused by multiple clamping.

[0035] 2) It has good applicability to grinding and polishing of various complex surfaces;

[0036] 3) The cost of technological transformation is low and suitable for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the positions of the grinding wheel, workpiece and polishing fluid nozzle in the method of the present invention: 1 is the grinding wheel, 2 is the shear rheological polishing fluid, 3 is the workpiece, and 24 is the polishing fluid nozzle;

[0038] Figure 2 Schematic diagram of the low-damage grinding process proposed in the method of the present invention: 1 is a grinding wheel, 11 is a grinding wheel binder, 12 is a grinding wheel fixed abrasive; 2 is a shear rheological polishing fluid, 21 is a non-Newtonian fluid base fluid, 22 is a free abrasive in the polishing fluid, 23 is the hydrostatic pressure generated by the dynamic pressure field of the polishing fluid on the shear surface; 3 is a workpiece, and 31 is a microcrack on the grinding surface;

[0039] Figure 3 Schematic diagram of the composite grinding and polishing process proposed in the method of the present invention: 1 is a grinding wheel, 11 is a grinding wheel binder, 12 is a grinding wheel fixed abrasive grains; 2 is a shear rheological polishing fluid, 21 is a non-Newtonian fluid base fluid, 22 is a free abrasive in the polishing fluid; 3 is a workpiece;

[0040] Figure 4 Schematic diagram of the in-situ polishing process proposed in the method of the present invention: 1 is a grinding wheel, 11 is a grinding wheel binder, 12 is a grinding wheel fixed abrasive grains; 2 is a shear rheological polishing fluid, 21 is a non-Newtonian fluid base fluid, 22 is a free abrasive in the polishing fluid; 3 is a workpiece;

[0041] Figure 5 The following is a rheological curve of a shear rheological polishing fluid configured with three typical abrasives in a specific embodiment. The non-Newtonian fluid base liquid is a non-Newtonian fluid composed of a polyhydroxy polymer and water, with a concentration of 52.5wt%; the abrasives are aluminum oxide, silicon oxide and diamond, with a particle size of 3000# and an abrasive concentration of 10wt%. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings.

[0043] Reference Figure 1 to Figure 5 , a progressive grinding-polishing method based on the shear rheological effect of a non-Newtonian fluid, comprising the following steps:

[0044] (1) mixing abrasive 22 and additives into a non-Newtonian fluid base liquid 21 having a shear rheological effect, stirring evenly to prepare a shear rheological polishing liquid 2, and adding the prepared polishing liquid 2 into a machine tool grinding fluid station;

[0045] (2) After completing the traditional rough grinding and semi-fine grinding, refer to Figure 1 , adjusting the position of the polishing fluid nozzle 24, providing the shear rheological polishing fluid 2 to the grinding zone from the cutting end of the grinding wheel 1 along the grinding wheel linear speed direction, replacing the traditional grinding fluid; the grinding wheel 1 is a 1A1 type disc-shaped grinding wheel, the surface of the workpiece 3 is a flat surface or a curved surface, and the grinding fluid is provided by pouring or high-pressure injection;

[0046] (3) Write the CNC program and set the grinding depth to be greater than zero. Figure 5 The shear rheology curve of the polishing fluid and the grinding process parameter range of the workpiece 3 material are shown to set the linear speed of the grinding wheel 1, control the shear rheology effect of the polishing fluid 2, and then improve the fluid dynamic pressure field intensity in the wedge-shaped grinding zone to achieve low-damage grinding of the workpiece 3 surface;

[0047] (4) Set the grinding depth to zero in the CNC program. Figure 5 The shear rheology curve of the polishing fluid and the grinding process parameter range of the workpiece 3 material are shown to set the linear speed of the grinding wheel 1, control the shear rheology effect of the polishing fluid 2, and perform a grinding-polishing composite process on the grinding surface;

[0048] (5) The grinding wheel 1 and the workpiece 3 are set to a non-contact state in the CNC program, and the shear rheological polishing is performed on the grinding surface. The material removal rate at each point on the surface during the polishing process is controlled by adjusting the rheological properties of the polishing fluid 2, the linear speed of the grinding wheel 1, the feed speed of the workpiece 3, and the gap between the grinding wheel 1 and the workpiece 3.

[0049] Furthermore, in the step (3), step (4), and step (5), during the step-by-step grinding-polishing process, after the shear rheological polishing fluid 2 enters the wedge-shaped grinding zone from the cutting end of the grinding wheel 1 along the grinding wheel linear velocity direction, a fluid dynamic pressure field is formed in the grinding zone; the distribution of the fluid dynamic pressure along the grinding wheel linear velocity direction (set as the x direction) is:

[0050]

[0051] Where η is the viscosity of the shear rheological polishing fluid, u is the flow velocity of the shear rheological polishing fluid along the x-axis, and p is the fluid dynamic pressure field intensity in the wedge-shaped grinding zone.

[0052] Shear rheology in the grinding zone The polishing fluid 2 undergoes rheological effects under the shearing action of the grinding wheel 1, including shear thickening, shear solidification or shear expansion. The closer the shear rheological effect of the polishing fluid 2 is to the grinding zone, the closer its rheological properties are to a stable state, and its viscosity can increase by dozens or even hundreds of times. Figure 5 According to formula (1), the shear rheological effect greatly increases the intensity of the fluid dynamic pressure field in the grinding zone.

[0053] Furthermore, in the step (3), during the low-damage grinding process, the grinding wheel 1 and the workpiece 3 being ground are in contact, that is, the grinding depth is greater than zero and is 0 to 10 μm.

[0054] Reference Figure 2 , low damage grinding is achieved through the following three aspects:

[0055] 3.1) The rheological effect of shear rheology polishing fluid 2 strengthens the fluid dynamic pressure field intensity in the wedge-shaped grinding zone, thereby increasing the hydrostatic pressure 23 in the direction of the shear plane perpendicular to the material removal during the grinding process, promoting the removal of the plastic domain of hard and brittle materials;

[0056] 3.2) The shear rheological polishing fluid 2 flexibly holds the free abrasive particles 22, removes the grinding wheel binder material 11, and realizes online sharpening of the grinding wheel 1;

[0057] 3.3) The shear rheological polishing fluid 2 flexibly holds the free abrasive particles 22 to polish the damaged layer on the grinding surface.

[0058] In the low-damage grinding process, the material removal is mainly based on the grinding effect of the fixed abrasive particles 13 on the surface of the grinding wheel 1; the polishing material removal rate of the grinding surface by the free abrasives 22 in the shear rheological polishing fluid 2 is auxiliary; the online sharpening of the grinding wheel 1 by the free abrasives 22 in the shear rheological polishing fluid 2 can maintain the grinding performance of the grinding wheel, thereby improving the grinding surface quality.

[0059] Further, refer to Figure 3In step (4), during the composite grinding and polishing process, the program sets the grinding depth to zero, the grinding wheel 1 and the workpiece 3 are in a quasi-contact state, and the actual grinding depth is equal to the residual height after the previous grinding.

[0060] Furthermore, material removal during the composite grinding and polishing process is achieved through the following two aspects:

[0061] 4.1) Polishing, material removal is due to elastic deformation of the workpiece-tool system;

[0062] 4.2) The shear rheological polishing fluid flexibly holds the free abrasive particles and polishes the damaged layer on the grinding surface.

[0063] In the step (5), the grinding wheel and the workpiece are in a non-contact state, and the distance between the grinding wheel and the workpiece is greater than zero and is 0 to 5 mm.

[0064] Material removal is achieved in the following way: the shear rheological polishing fluid flexibly holds the free abrasive particles and polishes the grinding surface in the fluid dynamic pressure field.

[0065] The non-Newtonian fluid base liquid with shear rheological effect is one of the following: a non-Newtonian fluid composed of polyethylene glycol and silicon dioxide particles, a non-Newtonian fluid composed of polyhydroxy polymer and water, and a non-Newtonian fluid composed of polymethyl methacrylate and glycerol.

[0066] The non-Newtonian fluid base liquid accounts for 50% to 95% of the mass fraction of the polishing fluid.

[0067] The abrasive is one or a mixture of two or more of the following: diamond, cubic boron nitride, silicon nitride, silicon carbide, boron carbide, aluminum oxide, silicon oxide, zirconium oxide, cerium oxide, chromium oxide, iron oxide, magnesium oxide. The particle size of the abrasive is in the range of 0.5-10 μm, accounting for 5% to 50% of the mass fraction of the polishing liquid. The additive includes one or more of the following: dispersant, surfactant, pH regulator, chemical activator. As an optimization, the content of the additive in the shear rheological polishing liquid is less than 5%.

Claims

1. A progressive grinding-polishing method based on the shear rheological effect of non-Newtonian fluid, characterized in that: The processing method comprises the following steps: (1) Abrasives and additives are mixed into a non-Newtonian fluid base liquid having a shear rheological effect, stirred evenly, to prepare a shear rheological polishing fluid, and added to a machine tool grinding fluid station; (2) In the fine grinding stage after completing the conventional rough grinding and semi-fine grinding, a shear rheological polishing fluid is provided to the grinding zone along the linear speed direction of the grinding wheel from the cutting end of the grinding wheel to replace the conventional grinding fluid; (3) The grinding depth is set to be greater than zero in the CNC program, and the grinding wheel linear speed is set according to the shear rheological curve of the polishing fluid to control the shear rheological effect of the polishing fluid, thereby increasing the fluid dynamic pressure field intensity in the wedge-shaped grinding zone and achieving low-damage grinding of the workpiece surface; (4) The grinding depth is set to zero in the numerical control program, the grinding wheel linear speed is set according to the rheological curve of the shear rheological grinding and polishing fluid and the grinding process parameter range of the workpiece material, the shear rheological effect of the grinding and polishing fluid is controlled, and the grinding surface is subjected to a grinding-polishing composite process; (5) The grinding wheel and the workpiece are set to a non-contact state in the CNC program, and the grinding surface is subjected to shear rheological polishing. The material removal rate at each point on the surface during the polishing process is controlled by adjusting the rheological properties of the polishing fluid, the linear speed of the grinding wheel, the feed speed of the workpiece, and the gap between the grinding wheel and the workpiece; During the stepwise grinding and polishing process of step (3), the shear rheological polishing fluid enters the wedge-shaped grinding zone from the cutting end of the grinding wheel along the linear velocity direction of the grinding wheel, and forms a fluid dynamic pressure field in the wedge-shaped grinding zone; the polishing fluid undergoes rheological effects under the shearing action of the grinding wheel, including shear thickening, shear solidification or shear expansion; low-damage grinding is achieved through the following three aspects: 3.1) The rheological effect of shear rheology polishing fluid strengthens the fluid dynamic pressure field intensity in the wedge-shaped grinding zone, thereby increasing the hydrostatic pressure in the direction perpendicular to the shear plane of material removal during the grinding process, promoting the removal of the plastic domain of hard and brittle materials; 3.2) The shear rheological polishing fluid flexibly holds the free abrasive particles, removes the grinding wheel binder material, and realizes online sharpening of the grinding wheel; 3.3) The shear rheological polishing fluid flexibly holds the free abrasive particles and polishes the damaged layer on the grinding surface.

2. The progressive grinding-polishing method based on the shear rheological effect of non-Newtonian fluid according to claim 1, characterized in that: During the step-by-step grinding and polishing process of step (4) and step (5), the shear rheological polishing fluid enters the wedge-shaped grinding zone from the cutting end of the grinding wheel along the linear velocity direction of the grinding wheel, and forms a fluid dynamic pressure field in the wedge-shaped grinding zone; the polishing fluid undergoes rheological effects under the shearing action of the grinding wheel, including shear thickening, shear solidification or shear expansion.

3. The progressive grinding-polishing method based on the shear rheological effect of non-Newtonian fluid according to claim 1 or 2, characterized in that: During the low-damage grinding process of step (3), the grinding wheel and the workpiece being ground are in contact, that is, the grinding depth is greater than zero and is 0 to 10 μm.

4. The progressive grinding-polishing method based on the shear rheological effect of non-Newtonian fluid according to claim 1 or 2, characterized in that: In the step (4), the grinding depth is set to zero during the composite grinding and polishing process, the grinding wheel and the workpiece are in a quasi-contact state, and the actual grinding depth is equal to the residual height after the previous grinding.

5. The progressive grinding-polishing method based on the shear rheological effect of non-Newtonian fluid according to claim 4, characterized in that: Material removal during composite grinding and polishing is achieved through the following two aspects: 4.1) Polishing, material removal is due to elastic deformation of the workpiece-tool system; 4.2) The shear rheological polishing fluid flexibly holds the free abrasive particles and polishes the damaged layer on the grinding surface.

6. The progressive grinding-polishing method based on the shear rheological effect of non-Newtonian fluid according to claim 1 or 2, characterized in that: In the step (5), the grinding wheel and the workpiece are in a non-contact state, and the distance between the grinding wheel and the workpiece is greater than zero and is 0 to 5 mm.

7. The stepwise grinding-polishing method based on the shear rheological effect of non-Newtonian fluid according to claim 1 or 2, characterized in that: Material removal is achieved in the following way: the shear rheological polishing fluid flexibly holds the free abrasive particles and polishes the grinding surface in the fluid dynamic pressure field.

8. The stepwise grinding-polishing method based on the shear rheological effect of non-Newtonian fluid according to claim 1 or 2, characterized in that: The non-Newtonian fluid base liquid with shear rheological effect is one of the following: a non-Newtonian fluid composed of polyethylene glycol and silicon dioxide particles, a non-Newtonian fluid composed of a polyhydroxy polymer and water, and a non-Newtonian fluid composed of polymethyl methacrylate and glycerol; The non-Newtonian fluid base liquid accounts for 50% to 95% of the mass fraction of the polishing fluid.

9. The progressive grinding-polishing method based on the shear rheological effect of non-Newtonian fluid according to claim 1 or 2, characterized in that: The abrasive is one or a mixture of two or more of the following: diamond, cubic boron nitride, silicon nitride, silicon carbide, boron carbide, aluminum oxide, silicon oxide, zirconium oxide, cerium oxide, chromium oxide, iron oxide, magnesium oxide; The abrasive has a particle size range of 0.5-10 μm, accounting for 5% to 50% of the mass fraction of the polishing liquid; The additives include one or more of the following: dispersants, surfactants, pH regulators, chemical active agents; The content of the additive in the shear rheological polishing fluid is less than 5%.

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