A method for determining the rake surface temperature of a zirconia ceramic turning tool

Abstract

The present invention provides a method for determining the temperature of the front face of a zirconia ceramic turning tool, which belongs to the field of temperature measurement technology, and includes: determining the heat source that generates cutting heat based on the removal mechanism of zirconia ceramics; establishing a theoretical model of an impact heat source, and calculating the heat flux intensity of the impact heat source; establishing a theoretical model of a friction heat source, and calculating the heat flux intensity of the friction heat source; and establishing a theoretical model of the temperature distribution on the front face of a tool based on the heat source method theory, and calculating the temperature of the front face of a zirconia ceramic cutting tool. The present invention can determine that the cutting heat of zirconia ceramics is composed of an impact heat source and a friction heat source during the turning process of zirconia ceramics, determine the cutting heat source of the front face of the tool using a thermodynamic state equation, determine the cutting temperature of the front face of the tool when cutting zirconia ceramics, formulate and optimize cutting process parameters to improve the wear resistance of the tool, and provide a reference for selecting suitable cutting tools for industrial cutting of hard and brittle materials, setting reasonable cutting parameters, and exerting the extreme cutting performance of the tool.

Description

Technical Field

[0001] The invention relates to the technical field of temperature measurement, and in particular to a method for determining the temperature of a rake face of a zirconia ceramic turning tool. Background Art

[0002] Zirconia ceramics have extremely strong wear resistance, corrosion resistance and high hardness, and are widely used in defense, electronics, medical and other fields. In order to improve the processing efficiency of zirconia ceramics, turning can greatly improve the processing efficiency of zirconia ceramics. However, when processing zirconia ceramics, which are extremely hard and brittle materials, the tool wear rate is prone to be fast, which reduces the service life of the tool. Cutting temperature and distribution are one of the key factors affecting tool strength and wear rate. However, the generation mechanism and temperature distribution of cutting heat in zirconia ceramics are still unclear. At the same time, due to the small cutting area and the turning characteristics of zirconia ceramics, both the direct measurement of cutting zone temperature and the theoretical analysis of cutting heat face great challenges. Therefore, clarifying the generation mechanism of zirconia ceramic cutting heat and establishing a theoretical model of tool surface temperature distribution are of great significance to improving the service life of the tool.

[0003] At present, the research on zirconia ceramic cutting mainly focuses on the analysis of material removal mechanism and experimental cutting phenomenon. Zirconia ceramics achieve material removal by crack formation and expansion, and frequent cutting force fluctuations occur during cutting. The tool wear mechanism and wear phenomenon were experimentally analyzed. Tool wear is mainly due to the high temperature in the cutting zone and the high hardness of zirconia ceramics, which accelerates tool wear. Although it is determined that tool wear has a direct relationship with cutting temperature, the cutting zone temperature cannot be accurately obtained due to the small cutting area, sufficient tool strength must be ensured during the cutting of zirconia ceramics, and the chips are granular. It is also impossible to use the metal shear heat method to establish a theoretical model of the cutting temperature of zirconia ceramics. This also leads to the current belief that the cutting heat of zirconia ceramics mainly comes from the friction heat generated by the contact between the back face and the workpiece surface, but even when cutting with a new tool, a very high cutting temperature will be generated. Therefore, the cutting heat of zirconia ceramics is not only derived from friction heat. Therefore, the generation mechanism of zirconia ceramic cutting heat should be analyzed based on the mechanisms of brittle fracture, granular chips, and cutting force fluctuations during zirconia ceramic cutting, and then the cutting temperature should be determined. Summary of the invention

[0004] According to the technical problems raised above, a method for determining the temperature of the front face of a zirconia ceramic turning tool is provided. The method of the invention can determine that the cutting heat of zirconia ceramics is composed of impact heat source and friction heat source during the turning process of zirconia ceramics, and use the thermodynamic state equation to determine the cutting heat source of the front face of the tool, and then determine the cutting temperature of the front face of the tool when cutting zirconia ceramics, formulate and optimize the cutting process parameters to improve the wear resistance of the tool.

[0005] The technical means adopted by the present invention are as follows:

[0006] A method for determining the rake face temperature of a zirconia ceramic turning tool, comprising:

[0007] S1. Based on the removal mechanism of zirconia ceramics, analyze the source of cutting heat and determine the heat source that generates cutting heat;

[0008] S2. Establish a theoretical model of shock heat source and calculate the heat flux intensity of shock heat source;

[0009] S3. Establish a theoretical model of friction heat source and calculate the heat flux intensity of friction heat source;

[0010] S4. Based on the heat source method theory, a theoretical model of the temperature distribution on the front face of the tool is established to calculate the temperature of the front face of the zirconia ceramic turning tool.

[0011] Furthermore, step S1 specifically includes:

[0012] S11. The brittle material cutting process is divided into two stages. The first stage is the pressure growth stage, in which strong compressive stress accumulates at the edge of the tool. The second stage is the pressure release stage, in which strong compressive stress causes tensile stress, forming cracks and producing discontinuous chips to achieve material removal. The crack path is divided into the crack formation, crack propagation and crack upward extension stages. Due to the formation of discontinuous chips and surface feature pits, when the chips fall, a vacancy is formed between the tool and the workpiece. When the tool and the workpiece come into contact again, the tool and the workpiece have impact contact, causing obvious fluctuations in the cutting force. Therefore, it is necessary to consider the influence of the tool and the workpiece during the cutting process. The impact contact of the workpiece causes large stress in the cutting layer due to the small area of ​​the cutting layer. From the perspective of thermodynamics, the dynamic stress-strain relationship at high strain rate caused by the impact contact is close to an adiabatic process, which is a thermo-mechanical coupling process accompanied by temperature changes. The corresponding force-strain curve is an adiabatic curve. When the solid is subjected to impact loading, compressibility must be considered; under impact load, the high-pressure solid state equation with internal energy, volume and pressure as parameters is used to describe it, reflecting the relationship between volume deformation work and solid internal energy; in the repeated cutting process, the impact heat source generated by the impact contact between the tool rake face and the workpiece is regarded as the source of cutting heat;

[0013] S12. In actual cutting of brittle materials, due to the elastic deformation of the workpiece and the tool, under the influence of the elastic recovery of the machined surface of the workpiece, friction contact occurs between the back face of the tool and the workpiece, thereby generating a friction heat source.

[0014] Further, step S2 specifically includes:

[0015] S21. The impact force has the characteristic of maximum value during impact contact. The maximum cutting force theoretical model is established through brittle solid fracture mechanics to calculate the impact normal stress when the tool rake face and the workpiece are in impact contact. , the calculation formula is as follows:

[0016] ;

[0017] in, represents the bulk compression modulus of the tool material, Indicates the fracture toughness of the workpiece material. Indicates the cutting line speed, represents the crack angle, represents the tool rake angle, represents 1 / 2 crack length, represents the acceleration due to gravity, represents the crack deflection angle, , represents the horizontal deflection angle of the crack, Indicates the angle between the cutting force direction of the rake face and the crack, the crack deflection angle The angle between the cutting force direction of the rake face and the crack The relationship is as follows:

[0018] ;

[0019] S22. The front cutting edge of the tool is compressed after being subjected to impact load. The high-pressure solid state equation with internal energy, volume and pressure as parameters is used to describe the relationship between volume deformation work and solid internal energy. The density of the tool is determined by the solid state equation. , internal energy and the pressure The relationship between them is as follows:

[0020] ;

[0021] S23. Calculate the change in internal energy of the tool rake face after impact based on the mass and momentum conservation equations at the impact position. , the calculation formula is as follows:

[0022] ;

[0023] in, represents the initial internal energy of the tool; It represents the internal energy of the tool after impact; Indicates the impact pressure, ; Indicates the initial pressure on the tool rake face; represents the initial specific volume of the tool; It indicates the specific volume of the tool after impact compression;

[0024] S24. Calculate the compressive strain generated when the front cutting edge of the tool is subjected to impact load. , the calculation formula is as follows:

[0025] ;

[0026] S25, calculate the height of the tool rake face after compressive strain , the calculation formula is as follows:

[0027] ;

[0028] in, It represents the unit height of the tool rake face before compressive strain;

[0029] S26. According to the law of conservation of mass, the mass of an object remains unchanged before and after impact. According to the formula After the tool rake face and the workpiece are in impact contact, calculate the tool density per unit volume , the calculation formula is as follows:

[0030] ;

[0031] Due to the initial pressure on the tool rake face With impact pressure The initial pressure on the front face of the tool is very small. Can be omitted; density of the material Initial volume ratio with tool They are inversely related to each other;

[0032] S27, assuming that the impact heat source is evenly distributed, calculate the change in internal energy per unit area of ​​the tool rake face during the impact process according to the formula in step S23. , the calculation formula is as follows:

[0033] ;

[0034] S28. Calculate the number of impacts between the tool rake face and the workpiece per unit time based on the characteristics of the processed surface pits. , the calculation formula is as follows:

[0035] ;

[0036] in, Indicates the characteristic pit opening width; Indicates the time interval between the impact of the tool rake face and the workpiece; Indicates the depth of the pits on the workpiece surface;

[0037] S29: Based on step S27 and step S38, calculate the heat flux intensity of the impact heat source formed on the front face of the tool , the calculation formula is as follows:

[0038] .

[0039] Furthermore, step S3 specifically includes:

[0040] S31. The tool flank is affected by the elastic recovery of the machined surface of the workpiece. The tool flank and the workpiece are in frictional contact. Calculate the tangential friction between the flank and the machined surface. , the calculation formula is as follows:

[0041] ;

[0042] in, It represents the friction coefficient of the flank-workpiece contact interface; , All represent constants; Indicates the hardness of the workpiece material; Indicates the elastic modulus of the workpiece; Indicates the radius of the cutting edge; Indicates the tool back angle; Indicates cutting depth; Indicates the tool main deflection angle;

[0043] S32, calculate the friction heat generated by the friction between the back face of the tool and the machined surface of the workpiece per unit time , the calculation formula is as follows:

[0044] ;

[0045] S33, Calculate the thickness of the cutting layer during turning and cutting layer width , the calculation formula is as follows:

[0046] ;

[0047] ;

[0048] in, Indicates cutting feed speed;

[0049] S34, according to the contact relationship between the back face of the tool and the machined surface of the workpiece, the length is , width The rectangle is considered as the shape of the friction heat source, and the calculation , the calculation formula is as follows:

[0050] ;

[0051] in, It indicates the elastic contact length between the machined surface of the workpiece and the back face of the tool;

[0052] S35. Assuming that the friction heat source is evenly distributed on the contact interface, calculate the proportion of friction heat source transferred to the tool , the calculation formula is as follows:

[0053] ;

[0054] in, represents the thermal conductivity of the workpiece material, Indicates the thermal conductivity of the tool material; represents the thermal diffusivity of the workpiece material, Indicates the thermal diffusivity of the tool material;

[0055] S36. Calculate the heat flux intensity on the back face of the tool , the calculation formula is as follows:

[0056] .

[0057] Further, step S4 specifically includes:

[0058] S41, calculating the temperature rise of the front cutting edge of the tool caused by the impact heat source according to the calculated heat flux intensity of the impact heat source;

[0059] S42, calculating the temperature rise of the front cutting edge of the tool caused by the friction heat source according to the calculated heat flux intensity of the friction heat source;

[0060] S43. During the cutting process of zirconia ceramics, calculate the temperature of a point on the front cutting edge of the tool.

[0061] Further, step S41 specifically includes:

[0062] S411, Assume that the interface of the impact heat source is the same as the cutting layer, and the length is the width of the cutting layer , width is the thickness of the cutting layer A fixed rectangular heat source;

[0063] S412. Considering that all the heat generated by the impact heat source is absorbed by the tool, the interface boundary is adiabatic. The solution adopted should be applicable to semi-infinite media. Since the adiabatic boundary at the cutting edge is prone to heat accumulation, a mirror image virtual heat source is added at the cutting edge. The heat release intensity of the virtual heat source is the same as that of the impact heat source.

[0064] S413, establish a coordinate system on the front face of the tool xyz , calculate any point on the tool rake face Temperature rise caused by the entire fixed rectangular impingement heat source , the calculation formula is as follows:

[0065] ;

[0066] in, Indicates the thermal conductivity of the tool material; express h D The differential length in ; The differential heat source in the shock heat source is M ( x , y , z ) point; ; Represents the differential heat source in the mirror virtual heat source to M ( x , y , z ) point; ; express b D The differential length in .

[0067] Further, step S42 specifically includes:

[0068] S421. Assuming that the boundary of the friction heat source interface is also adiabatic, the adopted solution should be applicable to semi-infinite media. In order to eliminate the influence of heat accumulation at the adiabatic boundary, a mirror image virtual heat source is added at the cutting edge. The heat release intensity of the virtual heat source is the same as that of the friction heat source.

[0069] S422, in the same coordinate system as the tool rake face, calculate any point on the tool rake face Temperature rise caused by the entire fixed rectangular friction heat source , the calculation formula is as follows:

[0070] ;

[0071] in, express r β + L r The differential length in ; The differential heat source in the friction heat source is M ( x , y , z ) point; Represents the differential heat source in the mirror virtual heat source to M ( x , y, z ) point; .

[0072] Further, step S43 specifically includes:

[0073] S431, assuming that the cutting process is carried out at room temperature and the initial temperature is 25°C;

[0074] S432, calculate the tool rake face during zirconia ceramic cutting Temperature of point , the calculation formula is as follows:

[0075] .

[0076] Compared with the prior art, the present invention has the following advantages:

[0077] 1. The present invention provides a method for determining the temperature of the front cutting edge of a zirconia ceramic turning tool, which determines that the cutting heat of zirconia ceramics is mainly generated by the impact heat source generated by the front cutting edge and the workpiece and the friction heat source between the back cutting edge of the tool and the processed surface of the workpiece. The cutting heat does not completely come from the friction heat between the back cutting edge and the workpiece surface. The impact heat source between the front cutting edge and the workpiece is also the main source of cutting heat. The impact heat source is determined using the thermodynamic state equation, taking into account the cutting surface characteristics of brittle materials, the thermal properties of tool materials, and the performance of workpiece materials.

[0078] 2. The present invention provides a method for determining the temperature of the front cutting edge of a zirconia ceramic turning tool, which realizes the calculation of the surface temperature distribution of cutting tools for hard and brittle materials such as zirconia ceramics, and provides a reference for selecting suitable cutting tools for industrial cutting of hard and brittle materials, setting reasonable cutting parameters and exerting the ultimate cutting performance of the tool.

[0079] Based on the above reasons, the present invention can be widely promoted in the field of analyzing the relationship between tool thermal damage, thermal properties and tool wear when cutting hard and brittle materials such as zirconia ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0081] Figure 1 The figure is a flow chart of the method of the present invention.

[0082] Figure 2 A schematic diagram of the impact phenomenon generated during the cutting process of zirconia ceramics provided in an embodiment of the present invention.

[0083] Figure 3 The zirconia ceramic cutting principle and cutting heat source diagram provided by the embodiment of the present invention.

[0084] Figure 4 A schematic diagram of heat transfer on the front face of a tool when considering a fixed rectangular heat source problem provided in an embodiment of the present invention.

[0085] Figure 5 A diagram of an experimental device provided for an embodiment of the present invention.

[0086] Figure 6 The temperature prediction result on the cutting edge of the front cutting edge at a distance from the tool tip provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0087] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0088] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0089] like Figure 1 As shown, the present invention provides a method for determining the rake surface temperature of a zirconia ceramic turning tool, comprising:

[0090] S1. Based on the removal mechanism of zirconia ceramics, analyze the source of cutting heat and determine the heat source that generates cutting heat;

[0091] S2. Establish a theoretical model of shock heat source and calculate the heat flux intensity of shock heat source;

[0092] S3. Establish a theoretical model of friction heat source and calculate the heat flux intensity of friction heat source;

[0093] S4. Based on the heat source method theory, a theoretical model of the temperature distribution on the front face of the tool is established to calculate the temperature of the front face of the zirconia ceramic turning tool.

[0094] In specific implementation, as a preferred embodiment of the present invention, step S1 specifically includes:

[0095] S11. The brittle material cutting process is divided into two stages. The first stage is the pressure growth stage, in which strong compressive stress accumulates at the edge of the tool. The second stage is the pressure release stage, in which strong compressive stress causes tensile stress, forming cracks and producing discontinuous chips to achieve material removal. The crack path is divided into the crack formation, crack propagation and crack upward extension stages. Due to the formation of discontinuous chips and surface feature pits, when the chips fall, a vacancy is formed between the tool and the workpiece. When the tool and the workpiece come into contact again, the tool and the workpiece have impact contact, causing obvious fluctuations in the cutting force. Therefore, it is necessary to consider the influence of the tool and the workpiece during the cutting process. The impact contact of the workpiece causes large stress in the cutting layer due to the small area of ​​the cutting layer. From the perspective of thermodynamics, the dynamic stress-strain relationship at high strain rate caused by the impact contact is close to an adiabatic process, which is a thermo-mechanical coupling process accompanied by temperature changes. The corresponding force-strain curve is an adiabatic curve. When the solid is subjected to impact loading, compressibility must be considered; under impact load, the high-pressure solid state equation with internal energy, volume and pressure as parameters is used to describe it, reflecting the relationship between volume deformation work and solid internal energy; in the repeated cutting process, the impact heat source generated by the impact contact between the tool rake face and the workpiece is regarded as the source of cutting heat;

[0096] S12. In actual cutting of brittle materials, due to the elastic deformation of the workpiece and the tool, under the influence of the elastic recovery of the machined surface of the workpiece, friction contact occurs between the back face of the tool and the workpiece, thereby generating a friction heat source.

[0097] Therefore, in this embodiment, it is determined that the heat source generating cutting heat is mainly composed of two parts: one part is the impact heat source generated by the impact contact between the front cutting edge of the tool and the workpiece; the other part is the friction heat source generated by the back cutting edge of the tool and the machined surface of the workpiece.

[0098] In specific implementation, as a preferred embodiment of the present invention, step S2 specifically includes:

[0099] S21. The impact force has the characteristic of maximum value during impact contact. The maximum cutting force theoretical model is established through brittle solid fracture mechanics to calculate the impact normal stress when the tool rake face and the workpiece are in impact contact. , the calculation formula is as follows:

[0100] ;

[0101] in, represents the bulk compression modulus of the tool material, Indicates the fracture toughness of the workpiece material. Indicates the cutting line speed, represents the crack angle, represents the tool rake angle, represents 1 / 2 crack length, represents the acceleration due to gravity, represents the crack deflection angle, , represents the horizontal deflection angle of the crack, Indicates the angle between the cutting force direction of the rake face and the crack, the crack deflection angle The angle between the cutting force direction of the rake face and the crack The relationship is as follows:

[0102] ;

[0103] S22. The front cutting edge of the tool is compressed after being subjected to impact load. The high-pressure solid state equation with internal energy, volume and pressure as parameters is used to describe the relationship between volume deformation work and solid internal energy. The density of the tool is determined by the solid state equation. , internal energy and the pressure The relationship between them is as follows:

[0104] ;

[0105] S23. Calculate the change in internal energy of the tool rake face after impact based on the mass and momentum conservation equations at the impact position. , the calculation formula is as follows:

[0106] ;

[0107] in, represents the initial internal energy of the tool; It represents the internal energy of the tool after impact; Indicates the impact pressure, ; Indicates the initial pressure on the tool rake face; represents the initial specific volume of the tool; It indicates the specific volume of the tool after impact compression;

[0108] S24. Calculate the compressive strain generated when the front cutting edge of the tool is subjected to impact load. , the calculation formula is as follows:

[0109] ;

[0110] S25, calculate the height of the tool rake face after compressive strain , the calculation formula is as follows:

[0111] ;

[0112] in, It represents the unit height of the tool rake face before compressive strain;

[0113] S26. According to the law of conservation of mass, the mass of an object remains unchanged before and after impact. According to the formula After the tool rake face and the workpiece are in impact contact, calculate the tool density per unit volume , the calculation formula is as follows:

[0114] ;

[0115] Due to the initial pressure on the tool rake face With impact pressure The initial pressure on the front face of the tool is very small. Can be omitted; density of the material Initial volume ratio with tool They are inversely related to each other;

[0116] S27, assuming that the impact heat source is evenly distributed, calculate the change in internal energy per unit area of ​​the tool rake face during the impact process according to the formula in step S23. , the calculation formula is as follows:

[0117] ;

[0118] S28. Calculate the number of impacts between the tool rake face and the workpiece per unit time based on the characteristics of the processed surface pits. , the calculation formula is as follows:

[0119] ;

[0120] in, Indicates the characteristic pit opening width; Indicates the time interval between the impact of the tool rake face and the workpiece; Indicates the depth of the pits on the workpiece surface;

[0121] S29: Based on step S27 and step S38, calculate the heat flux intensity of the impact heat source formed on the front face of the tool , the calculation formula is as follows:

[0122] .

[0123] like Figure 2 FIG. 1 is a schematic diagram of the impact phenomenon generated during the cutting process of zirconia ceramics provided in this embodiment.

[0124] In specific implementation, as a preferred embodiment of the present invention, step S3 specifically includes:

[0125] S31. The tool flank is affected by the elastic recovery of the machined surface of the workpiece. The tool flank and the workpiece are in frictional contact. Calculate the tangential friction between the flank and the machined surface. , the calculation formula is as follows:

[0126] ;

[0127] in, It represents the friction coefficient of the flank-workpiece contact interface; , All represent constants; Indicates the hardness of the workpiece material; Indicates the elastic modulus of the workpiece; Indicates the radius of the cutting edge; Indicates the tool back angle; Indicates cutting depth; Indicates the tool main deflection angle;

[0128] S32, calculate the friction heat generated by the friction between the back face of the tool and the machined surface of the workpiece per unit time , the calculation formula is as follows:

[0129] ;

[0130] S33, Calculate the thickness of the cutting layer during turning and cutting layer width , the calculation formula is as follows:

[0131] ;

[0132] ;

[0133] in, Indicates cutting feed speed;

[0134] S34, according to the contact relationship between the back face of the tool and the machined surface of the workpiece, the length is , width The rectangle is considered as the shape of the friction heat source, and the calculation , the calculation formula is as follows:

[0135] ;

[0136] in, It indicates the elastic contact length between the machined surface of the workpiece and the back face of the tool;

[0137] S35. Assuming that the friction heat source is evenly distributed on the contact interface, calculate the proportion of friction heat source transferred to the tool , the calculation formula is as follows:

[0138] ;

[0139] in, represents the thermal conductivity of the workpiece material, Indicates the thermal conductivity of the tool material; represents the thermal diffusivity of the workpiece material, Indicates the thermal diffusivity of the tool material;

[0140] S36. Calculate the heat flux intensity on the back face of the tool , the calculation formula is as follows:

[0141] .

[0142] like Figure 3 As shown, it is the zirconia ceramic cutting principle and cutting heat source diagram provided in this embodiment.

[0143] In specific implementation, as a preferred embodiment of the present invention, step S4 specifically includes:

[0144] S41, calculating the temperature rise of the front cutting edge of the tool caused by the impact heat source according to the calculated heat flux intensity of the impact heat source;

[0145] S42, calculating the temperature rise of the front cutting edge of the tool caused by the friction heat source according to the calculated heat flux intensity of the friction heat source;

[0146] S43. During the cutting process of zirconia ceramics, calculate the temperature of a point on the front cutting edge of the tool.

[0147] In specific implementation, as a preferred embodiment of the present invention, step S41 specifically includes:

[0148] S411, Assume that the interface of the impact heat source is the same as the cutting layer, and the length is the width of the cutting layer , width is the thickness of the cutting layer A fixed rectangular heat source;

[0149] S412. Considering that all the heat generated by the impact heat source is absorbed by the tool, the interface boundary is adiabatic. The solution adopted should be applicable to semi-infinite media. Since the adiabatic boundary at the cutting edge is prone to heat accumulation, a mirror image virtual heat source is added at the cutting edge. The heat release intensity of the virtual heat source is the same as that of the impact heat source.

[0150] S413, establish a coordinate system on the front face of the tool xyz , calculate any point on the tool rake face Temperature rise caused by the entire fixed rectangular impingement heat source (including the mirror image virtual heat source) , the calculation formula is as follows:

[0151] ;

[0152] in, Indicates the thermal conductivity of the tool material; express h D The differential length in ; The differential heat source in the shock heat source is M ( x , y , z ) point; ; Represents the differential heat source in the mirror virtual heat source to M ( x , y , z ) point; ; express b D The differential length in .

[0153] In specific implementation, as a preferred embodiment of the present invention, step S42 specifically includes:

[0154] S421. Assuming that the boundary of the friction heat source interface is also adiabatic, the adopted solution should be applicable to semi-infinite media. In order to eliminate the influence of heat accumulation at the adiabatic boundary, a mirror image virtual heat source is added at the cutting edge. The heat release intensity of the virtual heat source is the same as that of the friction heat source.

[0155] S422, in the same coordinate system as the tool rake face, calculate any point on the tool rake face Temperature rise caused by the entire fixed rectangular friction heat source (including the mirror image virtual heat source) , the calculation formula is as follows:

[0156] ;

[0157] in, express r β + L r The differential length in ; The differential heat source in the friction heat source is M ( x , y , z ) point; Represents the differential heat source in the mirror virtual heat source to M (x , y , z ) point; .

[0158] In specific implementation, as a preferred embodiment of the present invention, step S43 specifically includes:

[0159] S431, assuming that the cutting process is carried out at room temperature and the initial temperature is 25°C;

[0160] S432, calculate the tool rake face during zirconia ceramic cutting Temperature of point , the calculation formula is as follows:

[0161] .

[0162] like Figure 4 As shown, it is a schematic diagram of heat transfer on the front face of the tool when considering the problem of a fixed rectangular heat source provided in this embodiment.

[0163] Example

[0164] 1. Selection of workpiece materials:

[0165] The workpiece material selected in this embodiment is fully sintered zirconia ceramic with diameters of 22.3 mm , 22.5 mm , 23.27 mm , the length is 90 mm ; Elastic modulus 210 Gpa ; Fracture toughness For 10 · ;hardness For 12 Gpa ;density 6050 kg / m ³; specific heat capacity 469J kg -1 ℃ -1 Thermal conductivity λ w 2.8 Wm -1 ℃ -1 .

[0166] 2. Selection of cutting tools:

[0167] The tool brand selected in this example is Cavallo, and the material is cubic boron nitride (CBN). 3480 kg / m³; specific heat capacity 850 Jkg -1 ℃ -1 Thermal conductivity 110 Wm -1 ℃ -1 ; Tool rake angle 0°; clearance angle 10°; main deflection angle 45°; cutting edge radius For 2 μm .

[0168] 3. Selection of experimental equipment:

[0169] In this embodiment, the turning experiment was carried out on a CAK5085 CNC lathe. Kistler 5080 A The six-component cutting force test system measures cutting forces using Optris LT 15 Infrared thermometer for temperature measurement, the temperature range is -50℃-975℃; the spectral response range is 8-14 μm ; The measurement accuracy is 0.1℃; The response time is 1 ms . Experimental equipment such as Figure 5 shown.

[0170] 4. Selection of temperature measurement points:

[0171] During the cutting process of zirconia ceramics, it was observed that granular chips were formed at the cutting layer, and then these granular chips were dispersed into the air, resulting in less chip residue on the front cutting edge. M (-1, -2, 0) points are used as temperature measurement points, and the temperature of the tool rake face is measured under a microscope. M The position of (-1,-2,0) is marked. M (-1, -2, 0) not only avoids the influence of chip accumulation on temperature measurement, but also meets the temperature measurement technical requirements of infrared thermometer. The temperature measurement results are shown in Table 1.

[0172] Table 1 Cutting parameters and results

[0173]

[0174] 5. Prediction of tool rake face temperature distribution:

[0175] The cutting temperature theoretical model established by the present invention is used to predict the cutting edge temperature. On the basis of verifying the accuracy of the prediction model, the temperature distribution at the cutting edge is further predicted. The temperature results on the cutting edge of the front cutting face at a distance from the tool tip are as follows: Figure 6As shown. Therefore, the temperature distribution of the cutting area on the rake face of the tool during the turning process of zirconia ceramics can be obtained, which solves the problem of being unable to measure the temperature in the cutting layer area on the rake face of the tool during the turning process of zirconia ceramics.

[0176] 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 method for determining the rake face temperature of a zirconia ceramic turning tool, characterized in that: include: S1. Based on the removal mechanism of zirconia ceramics, analyze the source of cutting heat and determine the heat source that generates cutting heat; S2. Establish a theoretical model of shock heat source and calculate the heat flux intensity of shock heat source; Step S2 specifically includes: S21. The impact force has the characteristic of maximum value during impact contact. The maximum cutting force theoretical model is established through brittle solid fracture mechanics to calculate the impact normal stress when the tool rake face and the workpiece are in impact contact. , the calculation formula is as follows: ； in, represents the bulk compression modulus of the tool material, Indicates the fracture toughness of the workpiece material. Indicates the cutting line speed, represents the crack angle, represents the tool rake angle, Represents 1 / 2 crack length, represents the acceleration due to gravity, represents the crack deflection angle, , represents the horizontal deflection angle of the crack, Indicates the angle between the cutting force direction of the rake face and the crack, the crack deflection angle The angle between the cutting force direction of the rake face and the crack The relationship is as follows: ； S22. The front cutting edge of the tool is compressed after being subjected to impact load. The high-pressure solid state equation with internal energy, volume and pressure as parameters is used to describe the relationship between volume deformation work and solid internal energy. The density of the tool is determined by the solid state equation. , internal energy and the pressure The relationship between them is as follows: ； S23. Calculate the change in internal energy of the tool rake face after impact based on the mass and momentum conservation equations at the impact position. , the calculation formula is as follows: ； in, represents the initial internal energy of the tool; It represents the internal energy of the tool after impact; Indicates the impact pressure, ; Indicates the initial pressure on the tool rake face; represents the initial specific volume of the tool; It indicates the specific volume of the tool after impact compression; S24. Calculate the compressive strain generated when the front cutting edge of the tool is subjected to impact load. , the calculation formula is as follows: ； S25, calculate the height of the tool rake face after compressive strain , the calculation formula is as follows: ； in, It represents the unit height of the tool rake face before compressive strain; S26. According to the law of conservation of mass, the mass of an object remains unchanged before and after impact. According to the formula After the tool rake face and the workpiece are in impact contact, calculate the tool density per unit volume , the calculation formula is as follows: ； Due to the initial pressure on the tool rake face With impact pressure The initial pressure on the front face of the tool is very small. Can be omitted; density of the material Initial volume ratio with tool They are inversely related to each other; S27, assuming that the impact heat source is evenly distributed, calculate the change in internal energy per unit area of ​​the tool rake face during the impact process according to the formula in step S23. , the calculation formula is as follows: ； S28. Calculate the number of impacts between the tool rake face and the workpiece per unit time based on the characteristics of the processed surface pits. , the calculation formula is as follows: ； in, Indicates the characteristic pit opening width; Indicates the time interval between the impact of the tool rake face and the workpiece; Indicates the depth of the pits on the workpiece surface; S29: Based on step S27 and step S28, calculate the heat flux intensity of the impact heat source formed on the front face of the tool , the calculation formula is as follows: ； S3. Establish a theoretical model of friction heat source and calculate the heat flux intensity of friction heat source; Step S3 specifically includes: S31. The tool flank is affected by the elastic recovery of the machined surface of the workpiece. The tool flank and the workpiece are in frictional contact. Calculate the tangential friction between the flank and the machined surface. , the calculation formula is as follows: ； in, It represents the friction coefficient of the flank-workpiece contact interface; , All represent constants; Indicates the hardness of the workpiece material; Indicates the elastic modulus of the workpiece; Indicates the radius of the cutting edge; Indicates the tool back angle; Indicates cutting depth; Indicates the tool main deflection angle; S32, calculate the friction heat generated by the friction between the back face of the tool and the machined surface of the workpiece per unit time , the calculation formula is as follows: ； S33, Calculate the thickness of the cutting layer during turning and cutting layer width , the calculation formula is as follows: ； ； in, Indicates cutting feed speed; S34, according to the contact relationship between the back face of the tool and the machined surface of the workpiece, the length is , width The rectangle is considered as the shape of the friction heat source, and the calculation , the calculation formula is as follows: ； in, It indicates the elastic contact length between the machined surface of the workpiece and the back face of the tool; S35. Assuming that the friction heat source is evenly distributed on the contact interface, calculate the proportion of friction heat source transferred to the tool , the calculation formula is as follows: ； in, represents the thermal conductivity of the workpiece material, Indicates the thermal conductivity of the tool material; represents the thermal diffusivity of the workpiece material, Indicates the thermal diffusivity of the tool material; S36. Calculate the heat flux intensity on the back face of the tool , the calculation formula is as follows: ； S4. Based on the heat source method theory, a theoretical model of the temperature distribution on the front face of the tool is established to calculate the temperature of the front face of the zirconia ceramic turning tool.

2. The method for determining the rake surface temperature of a zirconia ceramic turning tool according to claim 1, characterized in that: Step S1 specifically includes: S11. The brittle material cutting process is divided into two stages. The first stage is the pressure growth stage, in which strong compressive stress accumulates at the edge of the tool. The second stage is the pressure release stage, in which strong compressive stress causes tensile stress, forming cracks and producing discontinuous chips to achieve material removal. The crack path is divided into the crack formation, crack propagation and crack upward extension stages. Due to the formation of discontinuous chips and surface feature pits, when the chips fall, a vacancy is formed between the tool and the workpiece. When the tool and the workpiece come into contact again, the tool and the workpiece have impact contact, causing obvious fluctuations in the cutting force. Therefore, it is necessary to consider the influence of the tool and the workpiece during the cutting process. The impact contact of the workpiece causes large stress in the cutting layer due to the small area of ​​the cutting layer. From the perspective of thermodynamics, the dynamic stress-strain relationship at high strain rate caused by the impact contact is close to an adiabatic process, which is a thermo-mechanical coupling process accompanied by temperature changes. The corresponding force-strain curve is an adiabatic curve. When the solid is subjected to impact loading, compressibility must be considered; under impact load, the high-pressure solid state equation with internal energy, volume and pressure as parameters is used to describe it, reflecting the relationship between volume deformation work and solid internal energy; in the repeated cutting process, the impact heat source generated by the impact contact between the tool rake face and the workpiece is regarded as the source of cutting heat; S12. In actual cutting of brittle materials, due to the elastic deformation of the workpiece and the tool, under the influence of the elastic recovery of the machined surface of the workpiece, friction contact occurs between the back face of the tool and the workpiece, thereby generating a friction heat source.

3. The method for determining the rake surface temperature of a zirconia ceramic turning tool according to claim 1, characterized in that: Step S4 specifically includes: S41, calculating the temperature rise of the front cutting edge of the tool caused by the impact heat source according to the calculated heat flux intensity of the impact heat source; S42, calculating the temperature rise of the front cutting edge of the tool caused by the friction heat source according to the calculated heat flux intensity of the friction heat source; S43. During the cutting process of zirconia ceramics, calculate the temperature of a point on the front cutting edge of the tool.

4. A method for determining the rake surface temperature of a zirconia ceramic turning tool according to claim 3, characterized in that: Step S41 specifically includes: S411, Assume that the interface of the impact heat source is the same as the cutting layer, and the length is the width of the cutting layer , width is the thickness of the cutting layer A fixed rectangular heat source; S412. Considering that all the heat generated by the impact heat source is absorbed by the tool, the interface boundary is adiabatic. The solution adopted should be applicable to semi-infinite media. Since the adiabatic boundary at the cutting edge is prone to heat accumulation, a mirror image virtual heat source is added at the cutting edge. The heat release intensity of the virtual heat source is the same as that of the impact heat source. S413, establish a coordinate system on the front face of the tool xyz , calculate any point on the tool rake face Temperature rise caused by the entire fixed rectangular impingement heat source , the calculation formula is as follows: ； in, Indicates the thermal conductivity of the tool material; express h D The differential length in ; The differential heat source in the shock heat source is M ( x , y , z ) point; ; Represents the differential heat source in the mirror virtual heat source to M ( x , y , z ) point; ; express b D The differential length in .

5. The method for determining the rake surface temperature of a zirconia ceramic turning tool according to claim 3, characterized in that: Step S42 specifically includes: S421. Assuming that the boundary of the friction heat source interface is also adiabatic, the adopted solution should be applicable to semi-infinite media. In order to eliminate the influence of heat accumulation at the adiabatic boundary, a mirror image virtual heat source is added at the cutting edge. The heat release intensity of the virtual heat source is the same as that of the friction heat source. S422, in the same coordinate system as the tool rake face, calculate any point on the tool rake face Temperature rise caused by the entire fixed rectangular friction heat source , the calculation formula is as follows: ； in, express r β + L r The differential length in ; The differential heat source in the friction heat source is M ( x , y , z ) point; Represents the differential heat source in the mirror virtual heat source to M ( x , y , z ) point; .

6. The method for determining the rake surface temperature of a zirconia ceramic turning tool according to claim 3, characterized in that: Step S43 specifically includes: S431, assuming that the cutting process is carried out at room temperature and the initial temperature is 25°C; S432, calculate the tool rake face during zirconia ceramic cutting Temperature of point , the calculation formula is as follows: 。

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