Method for predicting temperature of fiber reinforced thermoplastic resin matrix composite during peripheral milling

Abstract

The application belongs to the field of cutting processing, and discloses a kind of fiber reinforced thermoplastic resin matrix composite peripheral milling temperature prediction method, three heat sources of plastic deformation heat source, rake face and chip friction heat source, friction heat source of relief surface and machined surface are fully considered, and the total heat production of cutting in peripheral milling process is determined accordingly;On this basis, the anisotropic characteristics of the composite material are fully considered, and the distribution ratio of the total heat production of cutting in the tool, the workpiece and the chip is solved;And finally, a thermoplastic composite peripheral milling temperature prediction method is formed, and the accuracy of the calculation method is verified by experiment.The method disclosed by the application is simple in form and practical in function, and can greatly improve the accuracy of thermoplastic composite peripheral milling temperature prediction, thereby helping to promote the development of high-quality milling of thermoplastic composite.

Description

Technical Field

[0001] This invention belongs to the field of machining and relates to a method for predicting the peripheral milling temperature of fiber-reinforced thermoplastic resin matrix composite materials. Background Technology

[0002] Fiber-reinforced thermoplastic resin matrix composites (referred to as "thermoplastic composites") are lightweight, high-strength, and possess excellent mechanical properties, making them highly promising for applications in the manufacturing of major equipment. Large components often require peripheral milling of their edges before assembly to ensure precision. However, thermoplastic composites are typically difficult to machine, prone to damage during processing. Furthermore, due to their high plasticity, thermoplastic composites are easily deformed during machining, leading to increased heat generation and higher cutting temperatures. Thermoplastic resins are extremely sensitive to temperature; exceeding their glass transition temperature causes a phase transition, which weakens the resin's constraint on the fibers, making them difficult to cut and resulting in burrs, flash, and other damage. It also makes the resin more likely to adhere to the tool surface, increasing friction and further raising the cutting temperature. To achieve high-quality peripheral milling of thermoplastic composites, it is essential to understand their peripheral milling temperature variation. Accurate prediction of the peripheral milling temperature of thermoplastic composites presents a critical challenge.

[0003] Accurate calculation of the peripheral milling temperature of thermoplastic composites is one of the essential foundations for achieving high-quality peripheral milling. For peripheral milling temperature calculation, accurately determining the heat generated during cutting and the heat distribution ratio among the tool, workpiece, and chips is a crucial step. The heat sources generally include heat generated by plastic deformation, heat generated by friction between the rake face and the chip, and heat generated by friction between the flank face and the machined surface. Thermoplastic composites are anisotropic materials, with different deformation patterns and thermal conductivity in each direction; therefore, the anisotropic characteristics must be considered when calculating the peripheral milling temperature. For traditional thermosetting composites, An Qinglong et al., in their 2018 invention patent "Modeling Method for Two-Dimensional Cutting Temperature of Carbon Fiber Reinforced Unidirectional Laminates" (patent number CN201610111307.8), proposed that because their plastic deformation is very small and the chips are mostly fragmented, the cutting heat source is often only considered as the single heat source of friction between the flank face and the machined surface. Thermoplastic composites, due to their high plasticity and the fact that their chips are mostly continuous long chips, have a composite heat source consisting of three heat sources during cutting. For metallic materials, Shucai Yang et al., in their 2018 paper titled "Investigation on the temperature field under the action of the blunt tooledge for precision cutting of titanium alloys" published in Volume 12 of the *International Journal on Interactive Design and Manufacturing*, pointed out that when calculating the cutting temperature of metals, these three heat sources need to be considered. However, since metals are isotropic materials, the anisotropic thermal conductivity issue does not need to be considered when calculating the heat distribution ratio. Therefore, the methods for calculating the peripheral milling temperature of thermosetting composites and metals are not entirely applicable to thermoplastic composites. Thus, to achieve accurate prediction of the peripheral milling temperature of thermoplastic composites, there is an urgent need to invent a peripheral milling temperature prediction method that considers multiple heat sources and anisotropic heat transfer characteristics. Summary of the Invention

[0004] This invention addresses the problem that existing methods cannot accurately predict the peripheral milling temperature of thermoplastic composites. First, it solves for the heat generated by three heat sources during thermoplastic composite cutting: the heat source from plastic deformation, the heat source from friction between the rake face and the chip, and the heat source from friction between the flank face and the machined surface, thus obtaining the total heat generated during cutting. Then, based on the anisotropic thermal conductivity of the composite, it solves for the distribution ratio of the total heat generated during cutting among the tool, workpiece, and chip. Finally, it combines the heat generation and heat distribution processes to construct a complete method for predicting the peripheral milling temperature of thermoplastic composites.

[0005] The technical solution of the present invention:

[0006] A method for predicting the temperature of peripheral milling of fiber-reinforced thermoplastic resin matrix composites is proposed. This method fully considers the heat generation from three major heat sources: the heat source of plastic deformation, the frictional heat source between the rake face and the chip, and the frictional heat source between the flank face and the machined surface, and solves for the total heat generation of cutting. Based on this, the method fully considers the anisotropic thermal conductivity characteristics of the composite material and solves for the distribution ratio of the total heat generation of cutting in the tool, workpiece, and chip. Finally, a method for predicting the temperature of peripheral milling of thermoplastic composites is proposed.

[0007] The specific steps are as follows:

[0008] Step 1: Calculate the total heat generated during cutting, taking into account plastic deformation and the heat source between the tool and chips.

[0009] When machining thermoplastic composites, the cutting heat mainly comes from the cutting work, which can be divided into three parts: the frictional work between the chip and the rake face, the plastic deformation work of the material, and the frictional work between the flank face and the machined surface. According to the law of conservation of energy, the total heat generated during machining is Q. total As shown in equation (1):

[0010] Q total =Q plastic +Q rake +Q flank (1)

[0011] In the formula, Q plastic Q represents the heat generated during plastic deformation. rake Q represents the heat generated by friction between the tool and the chip. flank This indicates that heat is generated by friction between the tool and the workpiece.

[0012] The total mechanical work done during the machining process can be expressed by the main cutting force F. c The total mechanical work W is calculated as shown in equation (2):

[0013] W = F c v (2)

[0014] In the formula, F c represents the main cutting force, and v represents the cutting speed.

[0015] Assuming that all the frictional and deformation work consumed in the three deformation zones is converted into heat, then we have equation (3).

[0016] Q total =W (3)

[0017] Step 2: Calculation of heat distribution ratio in the cutting zone considering anisotropic heat transfer behavior.

[0018] According to Fourier's law, the amount of heat transferred per unit time by heat conduction is directly proportional to the cross-sectional area perpendicular to the heat flow and directly proportional to the temperature gradient. The direction of heat conduction is opposite to the direction of the temperature gradient, as shown in equations (4) and (5):

[0019]

[0020]

[0021] In the formula, λ is the thermal conductivity, q is the heat flux density, Q is the heat flow rate, dT / dx is the temperature gradient, and A is the heat conduction area.

[0022] When cutting thermoplastic composites, the heat generated in the cutting zone is transferred to the chips, the tool, and the workpiece. Assuming that the heat transfer process to the chips, workpiece, and tool is not affected by time, the relationship is as shown in equation (6):

[0023] Q plastic +Q rake +Q flank =Q chip +Q tool +Q CFRTP (6)

[0024] In the formula, Q chip Q tool Q CFRTP These represent the heat flow rates to the chips, the cutting tool, and the thermoplastic composite workpiece, respectively. The heat distribution ratio in the cutting zone is determined by the ratio of the heat flow rates to the chips, the cutting tool, and the workpiece to the total heat in the cutting zone, as shown in equation (7):

[0025]

[0026] In the formula, R chip R tool R CFRTP These represent the heat distribution ratios of the incoming chips, cutting tools, and workpiece, respectively. Assuming that the heat transferred directly to the surrounding medium during machining is negligible, meaning all the generated heat is transferred out through the chips, cutting tools, and workpiece, the heat distribution ratios satisfy the relationship shown in equation (8):

[0027] R chip +R tool +R CFRTP =1 (8)

[0028] From the relationship between the above heat distribution ratios, it can be seen that knowing any two heat distribution ratios allows us to calculate the value of the third heat distribution ratio. This section aims to calculate the heat distribution ratio of the chips and tools during the machining of thermoplastic composites through theoretical calculations and experimental observations, and thus indirectly obtain the heat distribution ratio of the workpiece.

[0029] (1) Calculation of heat distribution ratio of incoming chips

[0030] This describes the heat transfer relationship during the machining of thermoplastic composites. Assume that heat from deformation zone I is transferred to the chips and workpiece, heat from deformation zone II is transferred to the chips and tool, and heat from deformation zone III is transferred to the tool and workpiece. Where R1 represents the proportion of heat transferred from plastic deformation to the chips, R2 represents the proportion of heat transferred from tool-chip friction to the chips, and R3 represents the proportion of heat transferred from tool-workpiece friction to the workpiece. That is, the heat flow rate Q transferred to the chips... chip It consists of two parts, as shown in equation (9):

[0031] Q chip =Q plastic R1+Q rake R2 (9)

[0032] The heat production Q will be calculated below. plastic and Q rake And the heat transfer ratios R1 and R2. First, during the chip deformation process, shear slip occurs along the shear plane, and the heat Q generated by plastic deformation... plastic As shown in equation (10):

[0033] Q plastic =τ y γa c a w v (10)

[0034] In the formula, τ y Let γ be the shear yield stress of the material, γ be the shear strain along the shear plane, and a be the shear yield stress. c For the depth of cut, a w Let γ be the cutting width. γ can be obtained from equation (11).

[0035]

[0036] In the formula, γ0 is the rake angle of the tool, and φ is the shear angle. Secondly, when the chip is discharged along the rake face, it is subjected to compression and friction from the rake face, generating heat Q through friction. rake As shown in equation (12):

[0037] Q rake =(F c cosγ0-F y sinγ0)μv·l c1 a w (12)

[0038] In the formula, F y The force is the back force, μ is the coefficient of friction between the chip and the rake face, μ = 0.15, l c1 The contact length between the chip and the rake face can be approximately obtained by equation (13).

[0039]

[0040] When the fiber cutting angle 0 < θ ≤ π / 2, the fiber fracture mode is shearing. Due to the low interlayer bonding strength of the composite material, during cutting, the removed material flows out along the rake face and undergoes shear yielding along the fiber direction, i.e., φ = θ. When the fiber cutting angle π / 2 < θ ≤ π, the main fiber fracture mode is bending. Assuming that the fiber fractures along a shear plane at a certain angle to the workpiece surface, the magnitude of the shear angle can be obtained by the minimum total potential energy method, and φ = θ / 2 can be obtained. In summary, the relationship between the shear angle and the fiber cutting angle is shown in equation (14):

[0041]

[0042] To calculate the heat transfer proportionality coefficient, the average temperature of the contact surface will be solved simultaneously below. Different equations, to eliminate Solve for R1 and R2. Since the solutions for R1 and R2 are similar, we will use R1 as an example to solve for the heat transfer ratio.

[0043] If R1q plastic For the heat flux density transferred to the chips due to heat generated during plastic deformation, then (1-R1)q plastic This represents the heat flux density transferred to the workpiece material. According to the Hahn inclined zone heat source model, the average temperature of the material near the shear plane is... As shown in equation (15),

[0044]

[0045] In the formula, q plastic Let be the shear heat flux density, c1 be the specific heat capacity of the thermoplastic composite, ρ be the density of the thermoplastic composite, t be the thickness of the chip, and θ0 be the initial temperature of the workpiece. The temperature θ at a specific instant is calculated using the JCJaeger line heat source theory. M As shown in equation (16):

[0046]

[0047] In the formula, Q is the heat flow rate, R is the proportion of heat transferred from the linear heat source to that point, a is the thermal diffusivity of the thermoplastic composite, and k is the equivalent thermal conductivity of the thermoplastic composite, which is calculated by formula (17):

[0048]

[0049] In the formula, k1, k2, and k3 are the thermal conductivity along the fiber direction, perpendicular to the fiber direction, and material thickness direction, respectively.

[0050] Based on this, assuming that when an insulator slides across a surface at a velocity v0, the average temperature rise of the surface is... As shown in equation (18):

[0051]

[0052] In the formula, q is the heat flux density, l is the length of the heat source in the direction of the moving speed, and L is a dimensionless parameter that is related to the cutting speed, the thermal conductivity, density, and specific heat capacity of the material, making its calculation relatively complex. Meanwhile, when formula (18) is used to calculate the average temperature of the shear surface, it can be transformed into formula (19). Average temperature of the shear surface As shown in equation (19):

[0053]

[0054] In the formula, L1 is the calculation coefficient. Equations (15) and (19) are combined to solve for R1, as shown in equation (20):

[0055]

[0056] In the formula, ξ is the deformation coefficient, which can be obtained from equation (21):

[0057]

[0058] R2 can also be obtained in the same way, as shown in equation (22):

[0059]

[0060] In the formula, q rake κ is the frictional heat flux density on the rake face. t Let θ be the thermal conductivity of the cutting tool, and θ′0 be the initial temperature of the cutting tool. The contact surface coefficient between the tool and the chip is denoted as . It can be obtained from equation (23):

[0061]

[0062] In the formula, b is the width of the heat source. Combining equations (2), (3), (7), (9) and (20), we can obtain equation (24):

[0063]

[0064] (2) Calculation of heat distribution ratio of the input tool

[0065] Based on the above assumptions, it can be seen that the heat sources during machining are all planar heat sources with uniform heat distribution, and the average temperature rise Δθ on the tool surface is... tool As shown in equation (25):

[0066]

[0067] In the formula, lc Let L be the total contact length of the cutting zone, k be the equivalent thermal conductivity of the thermoplastic composite, and L2 be the calculation coefficient, which is obtained by equations (26) and (27) respectively:

[0068] l c =l c1 +l c2 +l c3 (26)

[0069]

[0070] In the formula, l c1 , l c2 , l c3 These represent the contact length between the chip and the rake face, the contact length between the cutting edge blunt circle and the workpiece, and the contact length between the flank face and the machined surface, respectively. K2 is the thermal diffusivity of the tool material.

[0071] Substituting equation (27) into equation (25), we obtain equation (28):

[0072]

[0073] R has been calculated above. chip and R tool The value of R can be indirectly obtained from equation (8). CFRTP Value:

[0074] R CFRTP =1-R chip -R tool (29)

[0075] Step 3: Calculation of cutting zone temperature

[0076] The heat distribution ratio coefficient calculated from the model indicates that the average heat flux density q transferred to the workpiece material is... CFRTP As shown in equation (30):

[0077]

[0078] Substituting this into the milling heat transfer equation (31), the temperature value of a certain point on the workpiece during machining can be calculated:

[0079]

[0080] In the formula, T M This represents the temperature rise at a point in the workpiece with coordinates (X, Z). As shown in the figure below, this coordinate system is established with the origin O of the heat source, the X-axis direction of the cutting speed v, and the Z-axis direction of the cutting thickness.

[0081] The beneficial effects of this invention are that it proposes a precise method for predicting the peripheral milling temperature of thermoplastic composites. This method can accurately calculate the total heat generated during cutting and the heat distribution ratio under different cutting parameters, and can predict the peripheral milling temperature based on these quantities. Compared with existing methods, this invention introduces the heat generated by plastic deformation into the calculation of the peripheral milling temperature of thermoplastic composites for the first time. Considering the anisotropic thermal conductivity of thermoplastic composites, it also provides the heat distribution ratio of the total heat generated during cutting in the tool, workpiece, and chips. This fundamentally solves the problem of the single heat source in existing methods for predicting the peripheral milling temperature of composite materials. The method involved in this invention is simple in form and practical in function, and can significantly improve the accuracy of peripheral milling temperature prediction for thermoplastic composites, thereby contributing to the development of high-quality milling machining of thermoplastic composites. Attached Figure Description

[0082] Figure 1 This is a flowchart of the method for calculating the peripheral milling temperature of thermoplastic composites;

[0083] Figure 2 This is a schematic diagram of the heat transfer mechanism and peripheral milling heat transfer during the processing of thermoplastic composites. (a) is a schematic diagram of the overall heat transfer of the thermoplastic composite, (b) is a schematic diagram of the heat source entering the workpiece, tool and chips, (c) is a schematic diagram of the heat generation during cutting of the thermoplastic composite, and (d) is a schematic diagram of the heat transfer during peripheral milling of the thermoplastic composite. Detailed Implementation

[0084] The implementation methods of the peripheral milling temperature prediction method for thermoplastic composites involved in this invention will be described below with reference to the accompanying drawings and specific examples.

[0085] Taking the widely used T700 grade carbon fiber / PEEK resin-based thermoplastic composite as an example, the peripheral milling temperature under typical working conditions was calculated based on the derivations made in steps one through three above. The material property parameters used in the calculation are shown in Table 1.

[0086] Table 1. CFRTP Material Properties

[0087]

[0088] The thermal properties of the workpiece and tool materials, as well as the tool parameters used in the calculations, are shown in Table 2.

[0089] Table 2 Tool and Material Parameters

[0090]

[0091] The accuracy of the calculated theoretical temperature predictions was compared using experimental temperature values ​​as an indicator. The results of the accuracy comparison are shown in Table 3.

[0092] Table 3. Calculation results and relative errors of workpiece temperature

[0093]

[0094]

[0095] Note: T represents the experimental measurement; T M is the calculated value from the model; E is the relative error.

[0096] As shown in Table 3, the method for predicting the peripheral milling temperature of thermoplastic composites proposed in this invention can effectively predict the peripheral milling temperature of thermoplastic composites, with a maximum calculation error of 24.0% and an average calculation error of 11.5%.

Claims

1. A method for predicting the temperature of peripheral milling of fiber-reinforced thermoplastic resin matrix composites, which fully considers the heat generation from three major heat sources: the heat source of plastic deformation, the frictional heat source between the rake face and the chip, and the frictional heat source between the flank face and the machined surface, and solves for the total heat generation of cutting; based on this, it fully considers the anisotropic thermal conductivity characteristics of the composite material and solves for the distribution ratio of the total heat generation of cutting in the tool, workpiece, and chip; and finally forms a method for predicting the temperature of peripheral milling of thermoplastic composites; characterized in that, The specific steps are as follows: Step 1: Calculate the total heat generated during cutting, taking into account plastic deformation and the heat source between the tool and chips. When machining thermoplastic composites, the cutting heat mainly comes from the cutting work, which can be divided into three parts: the frictional work between the chip and the rake face, the work of plastic deformation of the material, and the frictional work between the flank face and the machined surface. According to the law of conservation of energy, the total heat generated during machining is Q. total As shown in equation (1): Q total =Q plastic +Q rake +Q flank (1) In the formula, Q plastic Q represents the heat generated during plastic deformation. rake Q represents the heat generated by friction between the tool and the chip. flank This indicates heat generated by friction between the cutting tool and the workpiece. The total mechanical work done during the machining process is transmitted through the main cutting force F. c The total mechanical work W is calculated as shown in equation (2): W=F c v (2) In the formula, F c represents the main cutting force, and v represents the cutting speed; Assuming that all the frictional and deformation work consumed in the three deformation zones is converted into heat, then we have equation (3). Q total =W (3) Step 2: Calculation of heat distribution ratio in the cutting zone considering anisotropic heat transfer behavior. According to Fourier's law, the amount of heat transferred per unit time by heat conduction is directly proportional to the cross-sectional area perpendicular to the heat flow and to the temperature gradient. The direction of heat conduction is opposite to the direction of the temperature gradient, as shown in equations (4) and (5): In the formula, λ is the thermal conductivity, q is the heat flux density, Q is the heat flow rate, dT / dx is the temperature gradient, and A is the heat conduction area. When cutting thermoplastic composites, the heat generated in the cutting zone is transferred to the chips, the tool, and the workpiece. Assuming that the heat transfer process to the chips, workpiece, and tool is not affected by time, the relationship is as shown in equation (6): Q plastic +Q rake +Q flank =Q chip +Q tool +Q CFRTP (6) In the formula, Q chip Q tool Q CFRTP These represent the heat flow rates of the incoming chips, cutting tools, and thermoplastic composite workpiece, respectively. The heat distribution ratio in the cutting zone is determined by the ratio of the heat flow rates of the incoming chips, cutting tools, and workpiece to the total heat in the cutting zone, as shown in equation (7). In the formula, R chip R tool R CFRTP Let represent the heat distribution ratios of the incoming chips, cutting tools, and workpiece, respectively; assuming that the heat transferred directly to the surrounding medium during machining is negligible, that is, all the heat generated is transferred out through the chips, cutting tools, and workpiece, the heat distribution ratios satisfy the relationship shown in equation (8): R chip +R tool +R CFRTP =1 (8) From the relationship between the above heat distribution ratios, it can be seen that if any two heat distribution ratios are known, the value of the third heat distribution ratio can be calculated. We intend to calculate the heat distribution ratio of the chips and tools in the processing of thermoplastic composites through theoretical calculations and experimental observations, and then indirectly obtain the heat distribution ratio of the part transmitted to the workpiece. (1) Calculation of heat distribution ratio of incoming chips This describes the heat transfer relationship during the machining of thermoplastic composites. It is assumed that heat from deformation zone I is transferred to the chips and workpiece, heat from deformation zone II to the chips and cutting tool, and heat from deformation zone III to the cutting tool and workpiece. Here, R1 represents the proportion of heat generated during plastic deformation transferred to the chips, R2 represents the proportion of heat generated during tool-chip friction transferred to the chips, and R3 represents the proportion of heat generated during tool-workpiece friction transferred to the workpiece; that is, the heat flow rate Q transferred to the chips. chip It consists of two parts, as shown in equation (9): Q chip =Q plastic R1+Q rake R2 (9) Calculate the heat production Q separately plastic and Q rake And the heat transfer ratios R1 and R2; First, during the chip deformation process, shear slip occurs along the shear plane, and the heat generated by plastic deformation is Q. plastic As shown in equation (10): Q plastic =t y for c a w (10) In the formula, τ y Let γ be the shear yield stress of the material, γ be the shear strain along the shear plane, and a be the shear yield stress. c For the depth of cut, a w Let be the cutting width; where γ is obtained from equation (11). In the formula, γ0 is the rake angle of the tool, and φ is the shear angle; secondly, when the chip is discharged along the rake face, it is squeezed and rubbed by the rake face, and the friction of the rake face generates heat Q. rake As shown in equation (12): Q rake (F c cosγ0-F y sinγ0)μv·l c1 a w (12) In the formula, F y The force is the back force, μ is the coefficient of friction between the chip and the rake face, μ = 0.15, l c1 The contact length between the chip and the rake face is approximately obtained from equation (13). When the fiber cutting angle 0 < θ ≤ π / 2, the fiber fracture mode is shearing. Due to the low interlayer bonding strength of the composite material, during cutting, the removed material flows out along the rake face and undergoes shear yielding along the fiber direction, i.e., φ = θ. When the fiber cutting angle π / 2 < θ ≤ π, the main fiber fracture mode is bending. Assuming that the fiber fractures along the shear plane at a certain angle to the workpiece surface, the magnitude of the shear angle is obtained by the minimum total potential energy method, and φ = θ / 2 is obtained. The relationship between the shear angle and the fiber cutting angle is shown in Equation (14): To calculate the heat transfer proportionality coefficient, the average temperature of the contact surface will be solved simultaneously. Different equations, to eliminate Solve for R1 and R2; If R1q plastic For the heat flux density transferred to the chips due to heat generated during plastic deformation, then (1-R1)q plastic The heat flux density of the workpiece material is given; according to the Hahn inclined zone heat source model, the average temperature of the material near the shear plane is... As shown in equation (15): In the formula, q plastic Let c1 be the shear heat flux density, c1 be the specific heat capacity of the thermoplastic composite, ρ1 be the density of the thermoplastic composite, t be the thickness of the chip, and θ0 be the initial temperature of the workpiece. The temperature θ at a certain instantaneous point is solved using the JCJaeger line heat source theory. M As shown in equation (16): In the formula, R is the proportion of heat transferred from the linear heat source to that point, a is the thermal diffusivity of the thermoplastic composite, and k is the equivalent thermal conductivity of the thermoplastic composite, which is calculated by formula (17): In the formula, k1, k2, and k3 are the thermal conductivity along the fiber direction, perpendicular to the fiber direction, and material thickness direction, respectively; Based on this, assuming that when an insulator slides across a surface at a velocity v0, the average temperature rise of the surface is... As shown in equation (18): In the formula, q is the heat flux density, l is the length of the heat source in the direction of the moving speed; L is a dimensionless parameter that is related to the cutting speed, the thermal conductivity, density, and specific heat capacity of the material; at the same time, when formula (18) is used to calculate the average temperature of the shear surface, it changes to formula (19); the average temperature of the shear surface As shown in equation (19): In the formula, L1 is the calculation coefficient; equations (15) and (19) are combined to solve for R1, as shown in equation (20): In the formula, ξ is the deformation coefficient, which can be obtained from equation (21): R2 is also obtained in the same way, as shown in equation (22): In the formula, q rake κ is the frictional heat flux density on the rake face. t Let θ be the thermal conductivity of the cutting tool, and θ′0 be the initial temperature of the cutting tool. The contact surface coefficient between the tool and the chip is denoted as . It can be obtained from equation (23): In the formula, b is the width of the heat source. Combining equations (2), (3), (7), (9) and (20), we get equation (24): (2) Calculation of heat distribution ratio of the input tool Based on the above assumptions, it can be seen that the heat sources during machining are all planar heat sources with uniform heat distribution, and the average temperature rise Δθ on the tool surface is... tool As shown in equation (25): In the formula, l c Let L be the total contact length of the cutting zone, k be the equivalent thermal conductivity of the thermoplastic composite, and L2 be the calculation coefficient, which is obtained by equations (26) and (27) respectively: l c ＝l c1 +l c2 +l c3 (26) In the formula, l c1 , l c2 , l c3 These are the contact lengths between the chip and the rake face, the contact length between the cutting edge blunt circle and the workpiece, and the contact length between the flank face and the machined surface, respectively; K2 is the thermal diffusivity of the tool material. Substituting equation (27) into equation (25), we obtain equation (28): R has been calculated above. chip and R tool The value of R can be indirectly obtained from equation (8). CFRTP Value: R CFRTP =1-R chip -R tool (29) Step 3: Calculation of cutting zone temperature The heat distribution ratio coefficient calculated from the model indicates that the average heat flux density q transferred to the workpiece material is... CFRTP As shown in equation (30): Substituting this into the milling heat transfer equation (31), the temperature value of a certain point on the workpiece during machining can be calculated: In the formula, T M This represents the temperature rise at a point in a workpiece with coordinates (X, Z). This coordinate system is established with the origin O of the heat source, the X-axis direction of the cutting speed v, and the Z-axis direction of the cutting thickness.

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