A method for optimizing process parameters for efficient grinding of hard and brittle materials

Abstract

The present invention discloses a method for optimizing process parameters of high-efficient grinding of brittle materials, comprising the following steps: determining the critical speed of the tool; conducting grinding tests on the brittle materials; obtaining the surface roughness under different grinding parameters; calculating the remaining strength of the grinding surface; establishing a fitting formula for the relationship between the remaining strength of the grinding surface, the grinding force and the surface roughness; calculating the remaining strength of the grinding surface under all grinding parameters; respectively establishing fitting formulas for the relationships between the remaining strength σ of the grinding surface, the grinding force F and the grinding depth a p , the grinding feed rate v w ; and establishing an optimization model for selecting grinding parameters. The present invention greatly reduces the demand for test samples; can significantly reduce the sample size of damage detection, and the grinding force can indirectly reflect the influence of the grinding wheel state and the spindle vibration on the damage; and realizes the maximization of efficiency with the remaining strength of the surface of the part after grinding and the safety of the part during the grinding process as constraints.

Description

Technical Field

[0001] The invention relates to the technical field of grinding processing of hard and brittle materials, and in particular to a method for optimizing process parameters of high-efficiency grinding processing of hard and brittle materials. Background Art

[0002] At present, with the rapid development of electronic technology, semiconductor technology, micro-nano technology and optical technology, the scientific and technological level in various fields has been rapidly improved. This kind of high-tech has special requirements for the electrical, optical, thermal, corrosion and wear resistance of devices. Hard and brittle materials, due to their excellent properties such as corrosion resistance, high temperature resistance and wear resistance, are used as basic materials in many fields such as semiconductors, aerospace, and national defense. They play an increasingly wide role and occupy an increasingly important position. This kind of material is a typical difficult-to-process material due to its mechanical properties of high hardness and low fracture toughness. Grinding is the main process method for forming this kind of material. During the processing, a large amount of damage is generated on the surface and subsurface of the material, including surface crushing and subsurface cracks. These damages will expand macroscopically under continuous mechanical action, and may cause the destruction of hard and brittle material parts in severe cases. This is because the stress generated by the grinding force during the grinding process exceeds the residual strength of the material containing grinding damage. Improper selection of grinding process parameters not only inhibits the grinding efficiency, but also may cause the fracture of the entire material. Therefore, how to optimize the grinding process parameters is of great significance to achieve efficient grinding of hard and brittle materials.

[0003] At present, domestic and foreign scholars have done a lot of research on the optimization of process parameters for efficient grinding of hard and brittle materials. In Zhao Lingling's doctoral thesis "Research on Efficient and Precision Grinding Technology of Optical Glass Based on Large Abrasive Diamond Wheel" published in 2013, a large number of experiments were conducted to determine the optimized process parameters. In Li Ping's doctoral thesis "Research on Mechanism, Process and Engineering Application of Efficient, Precise and Low Damage Grinding of Brittle Optical Materials" published in 2016, it was found that the increase in the linear speed of the grinding wheel reduced the subsurface damage depth of the material; the increase in the grinding depth and the workpiece feed speed increased the subsurface damage depth of the material. However, the final optimization of grinding parameters still depends on a large number of test samples, and the grinding efficiency cannot be maximized. In the article "Prediction Model and Experimental Study on Subsurface Damage Depth of K9 Glass Grinding" published in China Mechanical Engineering Vol. 27, No. 18 in 2016, Zhang Feihu et al. obtained an empirical formula based on a large amount of experimental data using the multivariate linear regression fitting method, and then determined the optimization parameters. Due to the complexity of damage detection of hard and brittle materials, in order to improve the overall grinding process optimization efficiency, some scholars have established a relationship model between grinding surface roughness and damage depth, but under the influence of different grinding conditions, the existing model is not universal. Wang Y et al. published the article "Wheel Wear Related Instability in Grinding of Quartz Glass" in the journal "The International Journal of Advanced Manufacturing Technology" in 2021, Vol. 119, No. 1-2, pp. 233-245, which confirmed that there is no good correspondence between grinding surface roughness and damage depth, and it is affected by the grinding state of the grinding wheel. In addition, based on the optimization results of the existing grinding process parameters, the grinding machine speed is conducive to the suppression of damage. Chen Jiang et al. published "Study on Subsurface Crack Depth of K9 Optical Glass Plane Grinding Based on Grinding Speed" in Diamond and Abrasives Engineering, Vol. 36, No. 4, pp. 13-17 in 2016, which confirmed this phenomenon. However, with the increase of the grinding machine speed, the vibration problem is prominent. Especially in ultrasonic-assisted vibration grinding, even if the vibration process is stable, the ultrasonic effect will weaken as the rotation speed increases.

[0004] Based on the above research status, it is found that the problems existing in the optimization of existing grinding process parameters mainly include reliance on a large amount of experimental data; the damage test process of large sample specimens is cumbersome and time-consuming, and is affected by the grinding wheel state and the spindle state, and the damage depth cannot be converted using roughness. In addition, the residual strength of the ground surface of the part is related to the bearing capacity of the part in service and is an important design indicator. The structural safety of the part during grinding requires strict control of the grinding force. However, the existing methods all maximize efficiency with damage or surface roughness as constraints, rather than maximizing efficiency with the residual strength of the ground surface of the part and the safety of the part during grinding. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for optimizing process parameters for efficient grinding of hard and brittle materials, which can maximize the efficiency constrained by the residual strength of the surface of the part after grinding and the safety of the part during the grinding process.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A method for optimizing process parameters for efficient grinding of hard and brittle materials, comprising the following steps:

[0007] Step 1: Determine the critical speed of the tool

[0008] The tool speed v s As variables, the grinding force F and surface roughness Sa are used as the basis for judgment. The corresponding speed is taken as the tool critical speed v according to the position where the grinding force and surface roughness change from decreasing to increasing with the increase of speed. sc .

[0009] Step 2: Grinding test on hard and brittle materials

[0010] The tool speed v s Fixed to critical speed v sc , the grinding depth a p and workpiece feed speed v w As a variable, the variable value of the same variable is selected at more than 3 levels, and the grinding test of hard and brittle materials is carried out. The force signal F is monitored during the grinding process.

[0011] Step 3: Get the surface roughness under different grinding parameters

[0012] The surface roughness of the hard and brittle material samples after grinding was measured using a microscopic morphology detection instrument to obtain the surface roughness Sa under different grinding parameters.

[0013] Step 4: Calculate the residual strength of the ground surface

[0014] More than 5 hard and brittle material samples after grinding were selected for grinding damage test. The damage depth c of the samples was observed. The residual strength σ of the grinding surface was calculated based on the relationship between the damage depth c and the residual strength σ of the grinding surface. The relationship between the damage depth c and the residual strength σ of the grinding surface is:

[0015]

[0016] Among them, K IC is the fracture toughness, and α is the correction factor.

[0017] Step 5: Establish a fitting formula for the relationship between the residual strength of the grinding surface and the grinding force and surface roughness

[0018] The grinding force F, surface roughness Sa, and residual strength σ of the grinding surface obtained from step 2 to step 4 were subjected to regression analysis to establish a fitting formula for the relationship between the residual strength of the grinding surface and the grinding force and surface roughness:

[0019] σ=ASa+BF+C

[0020] Among them, coefficients A, B, and C are fitted through specific test data.

[0021] Step 6: Calculate the residual strength of the ground surface under all grinding parameters

[0022] Based on the fitting formula obtained by the regression analysis in step 5, the residual strength of the grinding surface corresponding to all grinding parameters is calculated. The grinding parameters include tool rotation speed, grinding depth and workpiece feed speed.

[0023] Step 7: Establish the residual strength σ of the grinding surface, the grinding force F and the grinding depth a respectively p , grinding feed speed v w The fitting formula of the relationship

[0024] Based on the residual strength of the grinding surface and the grinding force obtained under all grinding parameters, the relationship between the residual strength σ of the grinding surface and the grinding depth a is established. p , grinding feed speed v w The fitting formula of the relationship is used to establish the relationship between grinding force F and grinding depth a p , grinding feed speed v w The fitting formula of the relationship. The residual strength σ of the grinding surface and the grinding force F are the grinding depth a p and grinding feed speed v w Function of two arguments:

[0025] σ=σ r (a p ,v w )

[0026] F=Fg (a p ,v w )

[0027] The above functions respectively plot the contour diagrams of the residual strength of the grinding surface and the grinding force of the grinding depth and the workpiece feed speed through the process test data, and determine the specific functional relationship.

[0028] Step 8: Establish an optimization model for grinding parameter selection

[0029] The following optimization model is established:

[0030]

[0031] Constraint: σ r (a p ,v w )≥σ rc ,

[0032] F g (a p ,v w )≤F gc .

[0033] Where mrr is the material removal rate, σ rc is the critical residual strength, F gc is the critical grinding force.

[0034] Furthermore, the fitting formula of the residual strength σ of the grinding surface in step 7 is:

[0035]

[0036] Among them, D0, D1, D2, D3, k1, and k2 are all fitting parameters, which are fitted according to specific experimental data.

[0037] The grinding force F fitting formula is:

[0038]

[0039] Among them, E0, E1, E2, E3, β1, and β2 are all fitting parameters, which are fitted according to specific experimental data.

[0040] Furthermore, the fitting formula of the residual strength σ of the grinding surface in step 7 is:

[0041]

[0042] Among them, b1 and b2 are functions determined by material properties and grinding conditions, and a g is the grinding depth a p , grinding feed speed v wThe maximum undeformed cutting depth of the associated abrasive.

[0043] The grinding force F fitting formula is:

[0044]

[0045] Among them, λ, μ1, μ2, and μ3 are all fitting parameters, which are fitted according to specific test data. s is the tool speed.

[0046] Furthermore, the hard and brittle material includes single crystal silicon, optical glass or ceramics.

[0047] Furthermore, the microscopic morphology detection instrument described in step three includes a laser confocal microscope, an ultra-depth-of-field microscope, an optical microscope or a scanning electron microscope.

[0048] Furthermore, the grinding damage test in step 4 includes a surface polishing method, a layer-by-layer polishing method, a cross-sectional polishing method, an angle polishing method or a HF etching method.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] 1. The influence of tool speed on the quality of ground surface generally follows the rule that it first improves and then deteriorates. The present invention determines the critical speed through a single factor test of the influence of tool speed on the surface roughness after grinding, reduces the variables of process optimization, and greatly reduces the demand for test samples.

[0051] 2. The present invention adopts the regression analysis method to establish a fitting formula for the relationship between the residual strength of the grinding surface and the grinding force and the grinding surface roughness. This method can greatly reduce the sample size of damage detection. The grinding force can indirectly reflect the influence of the grinding wheel state and the spindle vibration on the damage.

[0052] 3. The present invention establishes fitting formulas for the relationship between the residual strength of the grinding surface, the grinding force and the grinding depth, and the grinding feed speed. An optimization model for the selection of grinding parameters is established through the fitting formula, thereby achieving efficiency maximization with the residual strength of the part surface after grinding and the safety of the part during the grinding process as constraints. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 A schematic diagram of the optimization process of the high-efficiency grinding process of hard and brittle materials involved in the present invention;

[0054] Figure 2 It is a schematic diagram of the grinding process optimization result in the present invention. Specific implementation plan

[0055] The present invention is described in detail below with reference to the accompanying drawings and specific implementation schemes.

[0056] according to Figure 1 The grinding parameter selection optimization model established by the process shown in the figure is as follows Figure 2 As shown in the figure, the fitting formulas between the residual strength of the grinding surface, the grinding force, the grinding depth, and the feed speed have an intersection area. To ensure the safety of the parts and the efficiency of the grinding process, the material removal rate curve should be between the two fitting curves. These two curves are the residual strength constraint of the grinding surface and the grinding force constraint. When the parameter is selected as the intersection of the two curves, this position is the current optimal solution, which can not only ensure the safety of the parts, but also maximize the processing efficiency.

[0057] Therefore, the optimization model selected according to the above grinding parameters reduces the dependence on a large amount of experimental data and achieves efficiency maximization with the residual strength of the part surface after grinding and the safety of the part during the grinding process as constraints.

[0058] The present invention is not limited to this embodiment, and any equivalent concepts or changes within the technical scope disclosed by the present invention are included in the protection scope of the present invention.

Claims

1. A method for optimizing process parameters for efficient grinding of hard and brittle materials, characterized by: The following steps are involved: Step 1: Determine the critical speed of the tool The tool speed v s As variables, the grinding force F and surface roughness Sa are used as the basis for judgment. The corresponding speed is taken as the tool critical speed v according to the position where the grinding force and surface roughness change from decreasing to increasing with the increase of speed. sc ; Step 2: Grinding test on hard and brittle materials The tool speed v s Fixed to critical speed v sc , the grinding depth a p and workpiece feed speed v w As a variable, the variable value of the same variable is selected at more than 3 levels, and the grinding test of hard and brittle materials is carried out. The force signal F is monitored during the grinding process; Step 3: Get the surface roughness under different grinding parameters The surface roughness of the hard and brittle material samples after grinding was measured using a microscopic topography detection instrument to obtain the surface roughness Sa under different grinding parameters; Step 4: Calculate the residual strength of the ground surface More than 5 hard and brittle material specimens after grinding were selected for grinding damage test. The damage depth c of the specimens was observed. The residual strength σ of the grinding surface was calculated based on the relationship between the damage depth c and the residual strength σ of the grinding surface. The relationship between the damage depth c and the residual strength σ of the grinding surface is: Among them, K IC is the fracture toughness, α is the correction factor; Step 5: Establish a fitting formula for the relationship between the residual strength of the grinding surface and the grinding force and surface roughness The grinding force F, surface roughness Sa, and residual strength σ of the grinding surface obtained from step 2 to step 4 were subjected to regression analysis to establish a fitting formula for the relationship between the residual strength of the grinding surface and the grinding force and surface roughness: σ=ASa+BF+C Among them, coefficients A, B, and C are fitted through specific test data; Step 6: Calculate the residual strength of the ground surface under all grinding parameters Based on the fitting formula obtained by the regression analysis in step five, the residual strength of the grinding surface corresponding to all grinding parameters is calculated; the grinding parameters include tool speed, grinding depth and workpiece feed speed; Step 7: Establish the residual strength σ of the grinding surface, the grinding force F and the grinding depth a respectively p , grinding feed speed v w The fitting formula of the relationship Based on the residual strength of the grinding surface and the grinding force obtained under all grinding parameters, the relationship between the residual strength σ of the grinding surface and the grinding depth a is established. p , grinding feed speed v w The fitting formula of the relationship is used to establish the relationship between grinding force F and grinding depth a p , grinding feed speed v w The fitting formula of the relationship; the residual strength σ of the grinding surface, the grinding force F is the grinding depth a p and grinding feed speed v w Function of two arguments: s = s r (a p ,v w ) F=F g (a p ,v w ) The above functions are used to draw contour diagrams of the residual strength of the grinding surface and the grinding force at the grinding depth and the workpiece feed speed respectively through process test data, and determine the specific functional relationship; Step 8: Build an optimization model The following optimization model is established: Constraint: σ r (a p ,v w )≥σ rc , F g (a p ,v w )≤F gc . Where mrr is the material removal rate, σ rc is the critical residual strength, F gc is the critical grinding force.

2. According to claim 1, a method for optimizing process parameters for high-efficiency grinding of hard and brittle materials is characterized by: The fitting formula of the residual strength σ of the grinding surface in step 7 is: Among them, D0, D1, D2, D3, k1, and k2 are all fitting parameters, which are fitted according to specific experimental data; The grinding force F fitting formula is: Among them, E0, E1, E2, E3, β1, and β2 are all fitting parameters, which are fitted according to specific experimental data.

3. The method for optimizing process parameters for high-efficiency grinding of hard and brittle materials according to claim 1, characterized in that: The fitting formula of the residual strength σ of the grinding surface in step 7 is: Among them, b1 and b2 are functions determined by material properties and grinding conditions, and a g is the grinding depth a p , grinding feed speed v w The associated maximum undeformed cutting depth of the abrasive grain; The grinding force F fitting formula is: Among them, λ, μ1, μ2, and μ3 are all fitting parameters, which are fitted according to specific test data. s is the tool speed.

4. The method for optimizing process parameters for high-efficiency grinding of hard and brittle materials according to claim 1, characterized in that: The hard and brittle material includes single crystal silicon, optical glass or ceramics.

5. The method for optimizing process parameters for high-efficiency grinding of hard and brittle materials according to claim 1, characterized in that: The microscopic morphology detection instrument described in step three includes a laser confocal microscope, an ultra-depth-of-field microscope, an optical microscope or a scanning electron microscope.

6. The method for optimizing process parameters for high-efficiency grinding of hard and brittle materials according to claim 1, characterized in that: The grinding damage test in step 4 includes a surface polishing method, a layer-by-layer polishing method, a cross-sectional polishing method, an angle polishing method or a HF etching method.

Images