A prediction method for temperature distribution in right-angle cutting of carbon fiber composites

Abstract

The present invention belongs to the technical field of composite material processing, and in particular, relates to a prediction method for the temperature distribution of right-angle cutting of carbon fiber composite materials. The prediction method determines the heat transfer mechanism inside the workpiece and between the tool and the tool, as well as the law of the change of the mechanical properties of the material with temperature, and realizes the prediction of the distribution of the right-angle cutting temperature of carbon fiber reinforced composite materials. A prediction method for the temperature distribution of right-angle cutting of carbon fiber composite materials, including: constructing a three-dimensional geometric model of the workpiece and the tool; meshing the three-dimensional geometric model of the workpiece and the tool; determining the mechanical behavior of the workpiece and the tool and its mechanical properties that change with temperature; forming a three-dimensional cutting model; setting the type of analysis step, determining the variable value of each parameter in the analysis step; determining the contact effect of the workpiece and the tool and the thermal behavior of the two; defining the boundary conditions of the three-dimensional cutting model; and calculating the prediction result of the temperature distribution of right-angle cutting of carbon fiber composite materials.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material processing, and in particular relates to a method for predicting temperature distribution of right-angle cutting of carbon fiber composite materials. Background Art

[0002] Carbon fiber reinforced composite materials (CFRP) are widely used in many technical fields such as aerospace due to their high specific strength, specific modulus, fatigue resistance and excellent corrosion resistance. Further research found that CFRP is composed of carbon fiber and resin at the microscopic level. The performance of the resin is easily affected by temperature. Its elastic modulus and strength will decrease with the increase of temperature, especially when the temperature exceeds its glass transition temperature (170-200°C), the mechanical properties of the resin will drop sharply. In addition, the thermal conductivity and specific heat capacity of CFRP are small, and the heat generated by cutting is not easy to diffuse, resulting in a high temperature in the cutting zone, which is easy to exceed the glass transition temperature of the resin. This will have an adverse effect on the manufacturing and processing of CFRP parts. The accumulated heat will not only cause the cracking of the resin, but also significantly affect the support of the resin to the fiber, making it difficult to effectively cut the fiber, and finally causing fiber pull-out, delamination, burrs and tearing. Therefore, it is necessary to predict the temperature distribution under different processing parameters during CFRP cutting, analyze its temperature change law and control the temperature of the cutting zone, so as to suppress the influence of the cutting process (due to temperature change) on the performance of damaged CFRP.

[0003] Technicians have made many technical attempts to solve the above technical problems. For example, they have carried out a large number of experiments for experimental analysis and theoretical analysis of the temperature distribution and change law during CFRP cutting. In addition, domestic and foreign scholars have also conducted a lot of research on the prediction of temperature distribution in right-angle cutting of CFRP. In 2019, Qi Zhenchao et al. published a paper titled "Research on the Mechanism of Right-Angle Cutting of CFRP Based on Thermal-Mechanical Coupling Simulation" in the journal "Tool Technology". The paper used the 2D Hashin failure criterion to define the failure initiation of the material, considered the distribution ratio of friction work converted into heat during the cutting process, and established a right-angle cutting model with fiber cutting angles of 0°, 45°, 90°, and 135°. The temperature distribution of different fiber cutting angles and the trend of cutting peak temperature changes were studied. In addition, in 2023, Ni et al. published "Research on Multiscale Modeling and Experiment of CFRP Milling" in the journal "Materials", which characterized the progressive damage of CFRP based on the 3D Hashin failure criterion, simulated the heat generation and heat transfer of two forms of heat sources, tool-workpiece friction and workpiece cracking during the cutting process, and found that the heat mainly diffused along the fiber direction, and the temperature distribution was closely related to the fiber orientation.

[0004] However, further research revealed that the experimental method for measuring temperature distribution has a long cycle and high cost. At the same time, it is difficult for existing equipment to accurately characterize the temperature distribution and change law during CFRP cutting. The model required for theoretical analysis is extremely complex, and it is difficult to accurately solve the temperature distribution during continuous cutting. This ultimately leads to a certain error between the temperature distribution simulation (prediction) results and the actual processing (test) results. Summary of the invention

[0005] The present invention provides a prediction method for the temperature distribution of right-angle cutting of carbon fiber composite materials. The prediction method overcomes the technical defects existing in the prior art, analyzes two heat generation modes of tool-chip friction and tool-workpiece friction, determines the heat transfer mechanism inside the workpiece and between the tool and the workpiece, determines the law of change of material mechanical properties with temperature, establishes a three-dimensional macroscopic thermal-mechanical coupling simulation model of right-angle cutting of carbon fiber reinforced composite materials, and realizes the prediction of the distribution of temperature of right-angle cutting of carbon fiber reinforced composite materials.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for predicting temperature distribution of right-angle cutting of carbon fiber composite materials comprises the following steps:

[0008] Step 1: Construct a 3D geometric model of the carbon fiber composite workpiece and tool;

[0009] Step 2: Mesh the three-dimensional geometric model of the carbon fiber composite material workpiece and the tool to obtain a hexahedral mesh of the carbon fiber composite material workpiece and the tool;

[0010] Step 3: Determine the mechanical behavior of the carbon fiber composite workpiece and its mechanical properties that vary with temperature;

[0011] Step 4: According to the actual cutting depth of machining, the positions between the three-dimensional geometric models of the carbon fiber composite material workpiece and the tool are adjusted to form a three-dimensional cutting model;

[0012] Step 5: Set the type of analysis step and determine the variable values ​​of each parameter in the analysis step;

[0013] Step 6: Determine the contact between the carbon fiber composite workpiece and the tool and their thermal behavior;

[0014] Step 7: Define the boundary conditions of the 3D cutting model;

[0015] Step 8: Based on the above steps 1-7, the predicted results of the temperature distribution of right-angle cutting of carbon fiber composite materials are calculated.

[0016] Preferably, the process of meshing the three-dimensional geometric model of the tool in step 2 can be specifically described as follows:

[0017] The non-cutting area in the three-dimensional geometric model of the tool is divided in a way that the grid density gradually decreases from the side close to the cutting area to the side far away from the cutting area;

[0018] The cutting area in the three-dimensional geometric model of the tool is divided in a manner of uniform grid distribution, and the grid size of the cutting area is not greater than the grid size of the non-cutting area.

[0019] Preferably, the process of determining the mechanical behavior of the carbon fiber composite material workpiece and its mechanical properties varying with temperature in step 3 can be specifically described as follows:

[0020] The linear elastic constitutive model is used to characterize the mechanical behavior of carbon fiber composite workpieces before damage occurs.

[0021] The linear damage evolution criterion is used to evolve the mechanical behavior of carbon fiber composite workpiece after damage occurs.

[0022] According to the mechanical properties of carbon fiber composite material workpieces at different temperatures, the curves of elastic modulus and strength changing with temperature were fitted.

[0023] Preferably, a linear elastic constitutive model is used to characterize the mechanical behavior of the carbon fiber composite material workpiece before damage occurs, which can be specifically described as follows:

[0024] Based on the Hashin-Puck failure criterion, the failure initiation of the four failure modes of carbon fiber composite workpieces is judged; among which, the failure criteria of the four failure modes meet the following requirements:

[0025] when ≥0, that is, when the fiber fails in tension:

[0026] (1);

[0027] when <0, that is, when the fiber fails in compression direction:

[0028] (2);

[0029] when ≥0, that is, when the tensile failure is perpendicular to the fiber direction:

[0030] (3);

[0031] when <0, that is, when the compression fails perpendicular to the fiber direction:

[0032] (4);

[0033] In formulas (1) to (4), the superscript , denote tensile and compressive failure, respectively. , Denote fiber and matrix respectively, and the subscript numbers 1, 2, and 3 denote along the fiber direction, perpendicular to the fiber direction, and the thickness direction of the workpiece respectively. , denote the effective normal stress and shear stress respectively, , Respectively represent the strength along the fiber direction and perpendicular to the fiber direction, is the shear strength of the composite material;

[0034] , , It is the stress component that forms the fracture plane when the fiber fails in compression perpendicular to the fiber direction. Its relationship with the effective stress component satisfies:

[0035] (5);

[0036] In formula (5), is the angle of the fracture surface of the carbon fiber composite material workpiece;

[0037] is the shear strength perpendicular to the fiber direction on the fracture surface, satisfying:

[0038] (6);

[0039] , is the friction coefficient, which is calculated from the material parameters and the angle of the fracture surface:

[0040] (7).

[0041] Preferably, the linear damage evolution criterion is used, and the process of evolving the mechanical behavior of the carbon fiber composite material workpiece after damage occurs inside can be specifically described as:

[0042] The damage factors d in different material directions satisfy:

[0043] (8);

[0044] In formula (8), , , is the strain at the onset of failure, , , is the strain at final fracture;

[0045] in, , , , , , Respectively meet:

[0046] (9);

[0047] In formula (9), is the elastic modulus, , , It is the fracture energy under tensile load along the fiber direction, the fracture energy under compressive load along the fiber direction, and the fracture energy under tensile load perpendicular to the fiber direction; represents the characteristic length of the unit;

[0048] The damage factor in the transverse compression failure mode is calculated based on the strain on the fracture surface and satisfies:

[0049] (10);

[0050] in, satisfy: , calculated from the strain components on the fracture surface:

[0051] (11);

[0052] In formula (11), is the strain at the onset of failure, and the strain when the failure factor reaches 1 is extracted The value of is obtained; represents the strain at final fracture, satisfying:

[0053] (12);

[0054] In formula (12), is the fracture energy, is the stress at the onset of failure and is determined by the stress components on the fracture surface.

[0055] Preferably, step 6 can be specifically described as:

[0056] Without considering radiation heat dissipation and convection heat dissipation, the heat generated during the machining process consists of the following two parts: one is the heat generated by the friction between the front face of the tool and the chips, and the other is the friction heat generated by the relative movement between the back face of the tool and the carbon fiber composite workpiece;

[0057] Among them, the heat generated by the friction between the tool rake face and the chips, and the friction heat generated by the relative movement between the tool flank face and the carbon fiber composite material workpiece meet the following requirements:

[0058] (18);

[0059] In formula (18), is the coefficient that expresses the dissipation of frictional energy as heat, is the heat coefficient transferred to the tool rake face and tool flank face, is the effective stress between the tool back face and the carbon fiber composite workpiece, It indicates the slip rate between the tool rake face and the chip, and between the tool flank face and the carbon fiber composite workpiece;

[0060] According to the law of conservation of energy, the heat flow balance equation of any unit of a carbon fiber composite workpiece satisfies:

[0061] (19);

[0062] In formula (19), represents the total heat flow of the unit, , , They are the density, specific heat capacity and thermal conductivity of carbon fiber composite workpieces. is the unit temperature, Any direction of any unit of the carbon fiber composite material workpiece;

[0063] By discretizing time through formula (19), we can obtain the The temperature at which:

[0064] (20);

[0065] In addition, when there is a temperature difference between the tool back face and the two contact surfaces of the carbon fiber composite workpiece, heat will also be transferred to meet:

[0066] (twenty one);

[0067] , They are the heat flow on the carbon fiber composite workpiece side and the tool back face side. represents the heat flow along the interface caused by friction sliding, is the proportional coefficient of heat transferred to the carbon fiber composite workpiece, is the thermal contact conductivity between the tool back face and the carbon fiber composite workpiece, satisfying: ;in, , are the thermal conductivity of carbon fiber composite workpiece and tool respectively. , is the temperature of carbon fiber composite workpiece and tool.

[0068] The invention provides a prediction method for right-angle cutting temperature distribution of carbon fiber composite materials. The prediction method for right-angle cutting temperature distribution of carbon fiber composite materials comprises the following steps: step 1: constructing a three-dimensional geometric model of a carbon fiber composite material workpiece and a tool; step 2: gridding the three-dimensional geometric model of the carbon fiber composite material workpiece and the tool to obtain a hexahedral grid of the carbon fiber composite material workpiece and the tool; step 3: determining the mechanical behavior of the carbon fiber composite material workpiece and its mechanical properties varying with temperature; step 4: adjusting the position between the three-dimensional geometric models of the carbon fiber composite material workpiece and the tool according to the actual cutting depth of processing to form a three-dimensional cutting model; step 5: setting the type of analysis step and determining the variable value of each parameter in the analysis step; step 6: determining the contact effect of the carbon fiber composite material workpiece and the tool and the thermal behavior of the two; step 7: defining the boundary conditions of the three-dimensional cutting model; step 8: based on the above steps 1-7, calculating and obtaining the prediction result of the right-angle cutting temperature distribution of the carbon fiber composite material.

[0069] A method for predicting the temperature distribution of right-angle cutting of carbon fiber composite materials having the above steps has at least the following technical advantages compared with the prior art:

[0070] (1) The present invention provides a method for predicting the temperature distribution of right-angle cutting of carbon fiber composite materials. The method fully considers the problem of tool-work heat transfer during right-angle cutting of carbon fiber composite materials and the change of material mechanical properties of carbon fiber composite materials with temperature, and establishes a three-dimensional macroscopic thermal-mechanical coupling simulation model of right-angle cutting of carbon fiber composite materials. The constructed model analyzes the heat generation mode during the cutting process, determines the heat transfer mechanism, and defines the law of material mechanical properties changing with temperature.

[0071] (2) The present invention provides a prediction method for the temperature distribution of carbon fiber composite materials during right-angle cutting, which simulates the heat generation and heat transfer during the right-angle cutting of carbon fiber composite materials and obtains the temperature distribution during the cutting process. Through this prediction method, the temperature distribution during the right-angle cutting of carbon fiber composite materials can be predicted, thereby providing technical support for the control of the cutting temperature of carbon fiber composite materials and the suppression of processing damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the following drawings:

[0073] Figure 1 A schematic flow chart of a method for predicting temperature distribution of right-angle cutting of carbon fiber composite materials provided by the present invention;

[0074] Figure 2 A schematic diagram of a three-dimensional simulation model for right-angle cutting of a carbon fiber composite workpiece;

[0075] Figure 3 Schematic diagram of the material mechanical behavior of a carbon fiber composite material workpiece in any direction;

[0076] Figure 4 Schematic diagram of the temperature distribution of carbon fiber composite workpiece during right-angle cutting at a fiber cutting angle of 0°. DETAILED DESCRIPTION

[0077] The present invention provides a prediction method for the temperature distribution of right-angle cutting of carbon fiber composite materials. The prediction method overcomes the technical defects existing in the prior art, analyzes two heat generation modes of tool-chip friction and tool-workpiece friction, determines the heat transfer mechanism inside the workpiece and between the tool and the workpiece, determines the law of change of material mechanical properties with temperature, establishes a three-dimensional macroscopic thermal-mechanical coupling simulation model of right-angle cutting of carbon fiber reinforced composite materials, and realizes the prediction of the distribution of temperature of right-angle cutting of carbon fiber reinforced composite materials.

[0078] The present invention provides a method for predicting the temperature distribution of carbon fiber composite materials at right angles. Figure 1 As shown, the following steps are included:

[0079] Step 1: Construct a 3D geometric model of the carbon fiber composite workpiece and tool.

[0080] Specifically, ABAQUS finite element simulation software is used as an example to construct three-dimensional geometric models of carbon fiber composite workpieces and cutting tools. Figure 2 As shown. This embodiment simulates the cutting process of a unidirectional laminate of carbon fiber composite material with a fiber direction of 0°. The size of the carbon fiber composite workpiece is 1.2mm×1mm×0.1mm (L×H×W). The tool rake angle is 25°, the back angle is 5°, and the blade radius is 10μm.

[0081] Step 2: Mesh the three-dimensional geometric model of the carbon fiber composite workpiece and the tool to obtain the hexahedral mesh of the carbon fiber composite workpiece and the tool.

[0082] On the basis of completing step 1, the three-dimensional geometric model of the carbon fiber composite material workpiece and the tool is further meshed. Specifically, the three-dimensional geometric model of the carbon fiber composite material workpiece and the tool is meshed into a hexahedral mesh by sweeping. Among them, the unit type of the carbon fiber composite material workpiece is defined as an eight-node thermal coupling hexahedral unit, and unit deletion and hourglass control are set. The unit type of the tool is defined as an eight-node thermal coupling hexahedral unit, and unit deletion is not set; and according to the non-cutting area / cutting area, the three-dimensional geometric model of the tool is meshed as follows: the non-cutting area in the three-dimensional geometric model of the tool is divided in a way that the grid density gradually decreases from the side close to the cutting area to the side away from the cutting area (preferably single-precision offset is selected, and the eccentricity is 5); the cutting area in the three-dimensional geometric model of the tool is divided in a way that the grid is evenly distributed, and the grid size of the cutting area obtained by division is not larger than the grid size of the non-cutting area obtained by division.

[0083] As an optional implementation method, in order to improve the computing efficiency, the mesh division of the three-dimensional geometric model of the tool can be referred to as follows: the cutting area size is 0.6mm×0.3mm (L×H), the grid is evenly distributed, and the unit size is 10μm; the grid size of the non-cutting area gradually increases from 10μm close to the cutting area to 40μm away from the cutting area.

[0084] Step 3: Determine the mechanical behavior of the carbon fiber composite workpiece and its mechanical properties as a function of temperature.

[0085] On the basis of completing step 2, the mechanical behavior of the carbon fiber composite workpiece and its mechanical properties that change with temperature are further determined. It is worth noting that due to the large difference in the material properties of the tool and the carbon fiber composite workpiece, and the low degree of tool wear during the shorter cutting process (negligible). Therefore, in this embodiment, the failure and damage of the tool are not considered, and only the performance parameters such as density, Young's modulus, Poisson's ratio, thermal conductivity and specific heat capacity are defined for it, and its heat generation and transfer mechanism is determined, without defining the initiation of its failure and the evolution of damage. Among them, the material parameters of the tool can be referred to as shown in the following table:

[0086] On the other hand, the mechanical behavior of the carbon fiber composite workpiece and its mechanical properties changing with temperature are determined. Specifically, the mechanical behavior of the carbon fiber composite workpiece can be referred to as follows Figure 3 As shown, the horizontal axis Represents strain, the left ordinate Represents stress, the vertical axis on the right It represents the damage factor, the AB segment is the material constitutive structure of the carbon fiber composite workpiece before failure, and the BC segment is the damage evolution. The material parameters of the carbon fiber composite workpiece can be referred to as shown in the following table:

[0087] Since carbon fiber composite materials are orthogonal anisotropy in the macroscopic sense, the material behaviors of carbon fiber composite workpieces along the fiber direction, perpendicular to the fiber direction and in the thickness direction are different to a certain extent, so it is necessary to define the material mechanical properties according to different material directions. As a more preferred embodiment of the present invention, the process of determining the mechanical behavior of a carbon fiber composite workpiece and its mechanical properties that change with temperature can be specifically described as follows: using a linear elastic constitutive model to characterize the mechanical behavior of the carbon fiber composite workpiece before damage occurs; using a linear damage evolution criterion to evolve the mechanical behavior of the carbon fiber composite workpiece after damage occurs; according to the mechanical properties of the carbon fiber composite workpiece at different temperatures, the curves of the elastic modulus and strength of the material changing with temperature are fitted.

[0088] The above steps are further explained as follows: Among them, the process of using the linear elastic constitutive model to characterize the mechanical behavior of the carbon fiber composite material workpiece before damage occurs can be specifically described as:

[0089] Based on the Hashin-Puck failure criterion, the failure initiation of the four failure modes of carbon fiber composite workpieces is judged; among which, the failure criteria of the four failure modes meet the following requirements:

[0090] when ≥0, that is, when the fiber fails in tension:

[0091] (1);

[0092] when <0, that is, when the fiber fails in compression direction:

[0093] (2);

[0094] when ≥0, that is, when the tensile failure is perpendicular to the fiber direction:

[0095] (3);

[0096] when <0, that is, when the compression fails perpendicular to the fiber direction:

[0097] (4);

[0098] In formulas (1) to (4), the superscript , denote tensile and compressive failure, respectively. , Denote fiber and matrix respectively, and the subscript numbers 1, 2, and 3 denote along the fiber direction, perpendicular to the fiber direction, and the thickness direction of the workpiece respectively. , denote the effective normal stress and shear stress respectively, , Respectively represent the strength along the fiber direction and perpendicular to the fiber direction, is the shear strength of the composite material;

[0099] , , It is the stress component that forms the fracture plane when the fiber fails in compression perpendicular to the fiber direction. Its relationship with the effective stress component satisfies:

[0100] (5);

[0101] In formula (5), is the angle of the fracture surface of the carbon fiber composite material workpiece;

[0102] is the shear strength perpendicular to the fiber direction on the fracture surface, satisfying:

[0103] (6);

[0104] , is the friction coefficient, which is calculated from the material parameters and the angle of the fracture surface:

[0105] (7).

[0106] Using the linear damage evolution criterion, the process of evolving the mechanical behavior of the carbon fiber composite workpiece after damage occurs can be specifically described as:

[0107] The damage factors d in different material directions satisfy:

[0108] (8);

[0109] In formula (8), , , is the strain at the onset of failure, , , is the strain at final fracture;

[0110] in, , , , , , Respectively meet:

[0111] (9);

[0112] In formula (9), is the elastic modulus, , , It is the fracture energy under tensile load along the fiber direction, the fracture energy under compressive load along the fiber direction, and the fracture energy under tensile load perpendicular to the fiber direction; represents the characteristic length of the unit;

[0113] The damage factor in the transverse compression failure mode is calculated based on the strain on the fracture surface and satisfies:

[0114] (10);

[0115] in, satisfy: , calculated from the strain components on the fracture surface:

[0116] (11);

[0117] In formula (11), is the strain at the onset of failure, and the strain when the failure factor reaches 1 is extracted The value of is obtained; represents the strain at final fracture, satisfying:

[0118] (12);

[0119] In formula (12), is the fracture energy, is the stress at the onset of failure and is determined by the stress components on the fracture surface.

[0120] According to the mechanical properties of the carbon fiber composite workpiece at different temperatures, the process of fitting the curves of the elastic modulus and strength of the material changing with temperature can be specifically described as follows: Since the mechanical properties of the carbon fiber composite workpiece at different temperatures are different, and will further affect the failure behavior and temperature distribution during the cutting process, it is necessary to consider the influence of temperature on the mechanical properties of the carbon fiber composite workpiece. The following temperature control fitting method is selected, for example: The temperature control equation of the elastic modulus along the fiber direction is shown in formula (13):

[0121] (13);

[0122] In the formula, the parameters with overline indicate the values ​​that vary with temperature. is the real-time temperature;

[0123] The elastic modulus in the direction perpendicular to the fiber and along the thickness of the workpiece is equal, that is, , whose value changing with temperature can be calculated by formula (14):

[0124] (14);

[0125] The shear moduli of the 1-2, 1-3 and 2-3 planes are determined by equation (15), where the 2-3 plane is an isotropic plane and the subscripts 2 and 3 can be interchanged, that is, :

[0126] (15);

[0127] The parameters of tensile strength and compressive strength along the fiber direction and perpendicular to the fiber direction can be calculated by the following formula (16):

[0128] (16);

[0129] The shear strength of the 1-2, 1-3 and 2-3 planes is shown in formula (17), where :

[0130] (17).

[0131] Through the above processing steps, technicians can determine the mechanical behavior of the carbon fiber composite material workpiece and its mechanical properties that change with temperature, and the mechanical behavior of the carbon fiber composite material workpiece and its mechanical properties that change with temperature can continue to be used for definition and assignment in subsequent steps.

[0132] Step 4: According to the actual cutting depth, adjust the position between the 3D geometric models of the carbon fiber composite material workpiece and the tool to form a 3D cutting model.

[0133] On the basis of completing step 3, the positions between the three-dimensional geometric models of the carbon fiber composite material workpiece and the tool are further adjusted. Figure 2 As shown, the position of the three-dimensional geometric model of the tool can be adjusted so that the three-dimensional geometric models of the carbon fiber composite material workpiece and the tool are as close as possible but do not invade each other. The cutting depth D is selected to be 50 μm.

[0134] Step 5: Set the type of analysis step and determine the variable values ​​of each parameter in the analysis step.

[0135] On the basis of completing step 4, the variable values ​​of each parameter in the analysis step are further set. Specifically, as a more preferred embodiment of the present invention, the type of the analysis step is set to dynamic, temperature-displacement explicit, the analysis time is selected to be 0.0005s, and the mass scaling factor is 10000. In the field output and historical output request, the number of outputs is set to 200, and the various variables required to be output are determined, such as reaction forces, element temperature, and solution dependent state variables.

[0136] Step 6: Determine the contact between the carbon fiber composite workpiece and the tool and their thermal behavior.

[0137] On the basis of completing step 5, the contact effect between the carbon fiber composite workpiece and the tool and the thermal behavior of the two are further analyzed.

[0138] First, define the contact between the carbon fiber composite workpiece and the tool. Specifically, the contact type between the carbon fiber composite workpiece and the tool is point-surface contact, and the tangential contact in the contact properties is defined as penalty contact. Therefore, the friction coefficient is set to f (where f=0.4) according to the fiber direction, and the normal contact is defined as hard contact.

[0139] Then, the thermal behaviors of the carbon fiber composite material workpiece and the tool are defined and analyzed. Specifically, as a preferred embodiment of the present invention, step 6 can be specifically described as:

[0140] Without considering radiation heat dissipation and convection heat dissipation (due to the fast cutting speed, it is assumed that the cutting process is adiabatic), the heat generated during the machining process consists of the following two parts: one is the heat generated by the friction between the front face of the tool and the chips, and the other is the friction heat generated by the relative movement between the back face of the tool and the carbon fiber composite workpiece.

[0141] Among them, the heat generated by the friction between the tool rake face and the chips, and the friction heat generated by the relative movement between the tool flank face and the carbon fiber composite material workpiece meet the following requirements:

[0142] (18);

[0143] In formula (18), The coefficient that represents the dissipation of frictional energy as heat (where =0.9), is the heat coefficient transferred to the tool rake face and tool flank face, is the effective stress between the tool back face and the carbon fiber composite workpiece, It indicates the slip rate between the tool rake face and the chip, and between the tool flank face and the carbon fiber composite workpiece.

[0144] According to the law of conservation of energy (i.e. the sum of the heat generated by friction during cutting is equal to the temperature rise of the material minus the cooling amount conducted to the surrounding units), the heat flow balance equation of any unit of the carbon fiber composite workpiece satisfies:

[0145] (19);

[0146] In formula (19), represents the total heat flow of the unit, , , They are the density, specific heat capacity and thermal conductivity of carbon fiber composite workpieces. is the unit temperature, Any direction of any unit of the carbon fiber composite material workpiece;

[0147] By discretizing time through formula (19), we can obtain the The temperature at which:

[0148] (20);

[0149] In addition, when there is a temperature difference between the tool back face and the two contact surfaces of the carbon fiber composite workpiece, heat will also be transferred to meet:

[0150] (twenty one);

[0151] , They are the heat flow on the carbon fiber composite workpiece side and the tool back face side. represents the heat flow along the interface caused by friction sliding (the ), is the heat proportional coefficient transferred to the carbon fiber composite workpiece ( =0.8), is the thermal contact conductivity between the tool back face and the carbon fiber composite workpiece, satisfying: ;in, , are the thermal conductivity of carbon fiber composite workpiece and tool respectively. , is the temperature of carbon fiber composite workpiece and tool.

[0152] In addition, some references involved in the thermal behavior of the carbon fiber composite workpiece and the tool are explained as follows: Specifically, in this process, assuming that the contact surface distance between the carbon fiber composite workpiece and the tool is less than 0.05 mm, the interface heat transfer contact thermal conductivity is defined as 12 mJ / mm·s·°C, the ratio of energy generated by friction converted into heat is defined as 1.0, and the distribution coefficient of the converted heat transferred to the workpiece is 0.80.

[0153] Step 7: Define the boundary conditions of the 3D cutting model.

[0154] On the basis of completing step 6, the boundary conditions of the three-dimensional cutting model are further defined as follows. Specifically, in order to facilitate the application of the displacement load of the tool and the constraint load of the carbon fiber composite workpiece during the cutting process, first set a point on the tool as the reference point RP-1, a point below the bottom of the carbon fiber composite workpiece as the reference point RP-2, and couple the tool node with the reference point RP-1, and couple the bottom node of the carbon fiber composite workpiece with the reference point RP-2. Then define the tool to feed along the X-axis direction at the reference point RP-1, and the cutting length is 0.5mm.

[0155] Secondly, considering that the bottom of the carbon fiber composite workpiece is fixed and clamped in the actual cutting experiment, a fully constrained boundary condition is introduced at the bottom of the carbon fiber composite workpiece in the numerical model. Finally, the initial temperatures of the carbon fiber composite workpiece and the tool are preset to 300K respectively.

[0156] Step 8: Based on the above steps 1-7, the predicted results of the temperature distribution of right-angle cutting of carbon fiber composite materials are calculated.

[0157] After completing the above steps, based on the various parameters (values) obtained in the above steps 1-7, the predicted results of the temperature distribution of right-angle cutting of carbon fiber composite materials are analyzed and calculated. The calculation results can be referred to as follows Figure 4 As shown in the figure, during the cutting process, the predicted average cutting temperature of the cutting zone is 314.9K, and the experimentally measured average cutting temperature is 316.2K, with an error of 8.02%. Based on this, it can be confirmed that the prediction method of the right-angle cutting temperature distribution of carbon fiber composite materials can be used to predict the temperature distribution during the right-angle cutting of carbon fiber composite materials. Based on this method, the analysis of the right-angle cutting temperature and the study of the temperature distribution of carbon fiber composite materials can be realized, thereby providing theoretical guidance for the control of cutting temperature and the suppression of processing damage.

[0158] The invention provides a method for predicting the temperature distribution of right-angle cutting of a carbon fiber composite material. The method comprises the following steps: step 1: constructing a three-dimensional geometric model of a carbon fiber composite material workpiece and a tool; step 2: meshing the three-dimensional geometric model of the carbon fiber composite material workpiece and the tool to obtain a hexahedral mesh of the carbon fiber composite material workpiece and the tool; step 3: determining the mechanical behavior of the carbon fiber composite material workpiece and its mechanical properties that vary with temperature; step 4: adjusting the position between the three-dimensional geometric models of the carbon fiber composite material workpiece and the tool according to the actual cutting depth of processing to form a three-dimensional cutting model; step 5: setting the type of analysis step and determining the variable value of each parameter in the analysis step; step 6: determining the contact effect of the carbon fiber composite material workpiece and the tool and the thermal behavior of the two; step 7: defining the boundary conditions of the three-dimensional cutting model; step 8: based on the above steps 1-7, calculating and obtaining the prediction result of the temperature distribution of the right-angle cutting of the carbon fiber composite material.

[0159] A method for predicting the temperature distribution of right-angle cutting of carbon fiber composite materials having the above steps has at least the following technical advantages compared with the prior art:

[0160] (1) The present invention provides a method for predicting the temperature distribution of right-angle cutting of carbon fiber composite materials. The method fully considers the problem of tool-work heat transfer during right-angle cutting of carbon fiber composite materials and the change of material mechanical properties of carbon fiber composite materials with temperature, and establishes a three-dimensional macroscopic thermal-mechanical coupling simulation model of right-angle cutting of carbon fiber composite materials. The constructed model analyzes the heat generation mode during the cutting process, determines the heat transfer mechanism, and defines the law of material mechanical properties changing with temperature.

[0161] (2) The present invention provides a prediction method for the temperature distribution of carbon fiber composite materials during right-angle cutting, which simulates the heat generation and heat transfer during the right-angle cutting of carbon fiber composite materials and obtains the temperature distribution during the cutting process. Through this prediction method, the temperature distribution during the right-angle cutting of carbon fiber composite materials can be predicted, thereby providing technical support for the control of the cutting temperature of carbon fiber composite materials and the suppression of processing damage.

[0162] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for predicting temperature distribution of right-angle cutting of carbon fiber composite materials, characterized in that: The steps include: Step 1: Construct a 3D geometric model of the carbon fiber composite workpiece and tool; Step 2: Mesh the three-dimensional geometric model of the carbon fiber composite material workpiece and the tool to obtain a hexahedral mesh of the carbon fiber composite material workpiece and the tool; Step 3: Determine the mechanical behavior of the carbon fiber composite workpiece and its mechanical properties as a function of temperature; Step 4: According to the actual cutting depth of machining, the positions between the three-dimensional geometric models of the carbon fiber composite material workpiece and the tool are adjusted to form a three-dimensional cutting model; Step 5: Set the type of analysis step and determine the variable values ​​of each parameter in the analysis step; Step 6: Determine the contact between the carbon fiber composite workpiece and the tool and their thermal behavior; Step 7: Define the boundary conditions of the 3D cutting model; Step 8: Based on the above steps 1-7, the predicted results of the temperature distribution of the carbon fiber composite material at right angles are calculated; The process of determining the mechanical behavior of the carbon fiber composite material workpiece and its mechanical properties varying with temperature in step 3 can be specifically described as follows: The linear elastic constitutive model is used to characterize the mechanical behavior of carbon fiber composite workpieces before damage occurs. The linear damage evolution criterion is used to evolve the mechanical behavior of carbon fiber composite workpiece after damage occurs. According to the mechanical properties of carbon fiber composite material workpieces at different temperatures, the curves of elastic modulus and strength of the material changing with temperature were fitted; Using the linear elastic constitutive model, the process of characterizing the mechanical behavior of the carbon fiber composite workpiece before damage occurs can be described as follows: Based on the Hashin-Puck failure criterion, the failure initiation of the four failure modes of carbon fiber composite workpieces is judged; among which, the failure criteria of the four failure modes meet the following requirements: when ≥0, that is, when the fiber fails in tension: （1）； when <0, that is, when the fiber fails in compression direction: （2）； when ≥0, that is, when the tensile failure is perpendicular to the fiber direction: （3）； when <0, that is, when the compression fails perpendicular to the fiber direction: （4）； In formulas (1) to (4), the superscript , denote tensile and compressive failure, respectively. , Denote fiber and matrix respectively, and the subscript numbers 1, 2, and 3 denote along the fiber direction, perpendicular to the fiber direction, and the thickness direction of the workpiece respectively. , denote the effective normal stress and shear stress respectively, , Respectively represent the strength along the fiber direction and perpendicular to the fiber direction, is the shear strength of the composite material; , , It is the stress component that forms the fracture plane when the fiber fails in compression perpendicular to the fiber direction. Its relationship with the effective stress component satisfies: （5）； In formula (5), is the angle of the fracture surface of the carbon fiber composite material workpiece; is the shear strength perpendicular to the fiber direction on the fracture surface, satisfying: （6）； , is the friction coefficient, which is calculated from the material parameters and the angle of the fracture surface: （7）； Using the linear damage evolution criterion, the process of evolving the mechanical behavior of the carbon fiber composite workpiece after damage occurs can be specifically described as: The damage factors d in different material directions satisfy: （8）； In formula (8), , , is the strain at the onset of failure, , , is the strain at final fracture; in, , , , , , Respectively meet: （9）； In formula (9), is the elastic modulus, , , It is the fracture energy under tensile load along the fiber direction, the fracture energy under compressive load along the fiber direction, and the fracture energy under tensile load perpendicular to the fiber direction; represents the characteristic length of the unit; The damage factor in the transverse compression failure mode is calculated based on the strain on the fracture surface and satisfies: （10）； in, satisfy: , calculated from the strain components on the fracture surface: （11）； In formula (11), is the strain at the onset of failure, and the strain when the failure factor reaches 1 is extracted The value of is obtained; represents the strain at final fracture, satisfying: （12）； In formula (12), is the fracture energy, is the stress at the onset of failure and is determined by the stress components on the fracture surface.

2. The method for predicting the temperature distribution of right-angle cutting of carbon fiber composite materials according to claim 1, characterized in that: The process of meshing the three-dimensional geometric model of the tool in step 2 can be specifically described as follows: The non-cutting area in the three-dimensional geometric model of the tool is divided in a way that the grid density gradually decreases from the side close to the cutting area to the side far away from the cutting area; The cutting area in the three-dimensional geometric model of the tool is divided in a manner of uniform grid distribution, and the grid size of the cutting area is not greater than the grid size of the non-cutting area.

3. The method for predicting temperature distribution of carbon fiber composite materials during right-angle cutting according to claim 1, characterized in that: The step 6 can be specifically described as: Without considering radiation heat dissipation and convection heat dissipation, the heat generated during the machining process consists of the following two parts: one is the heat generated by the friction between the front face of the tool and the chips, and the other is the friction heat generated by the relative movement between the back face of the tool and the carbon fiber composite workpiece; Among them, the heat generated by the friction between the tool rake face and the chips, and the friction heat generated by the relative movement between the tool flank face and the carbon fiber composite material workpiece meet the following requirements: （18）； In formula (18), is the coefficient that expresses the dissipation of frictional energy as heat, is the heat coefficient transferred to the tool rake face and tool flank face, is the effective stress between the tool back face and the carbon fiber composite workpiece, It indicates the slip rate between the tool rake face and the chip, and between the tool flank face and the carbon fiber composite workpiece; According to the law of conservation of energy, the heat flow balance equation of any unit of a carbon fiber composite workpiece satisfies: （19）； In formula (19), represents the total heat flow of the unit, , , They are the density, specific heat capacity and thermal conductivity of carbon fiber composite workpieces. is the unit temperature, Any direction of any unit of the carbon fiber composite material workpiece; By discretizing time through formula (19), we can obtain the The temperature at which: （20）； In addition, when there is a temperature difference between the tool back face and the two contact surfaces of the carbon fiber composite workpiece, heat will also be transferred to meet: （21）； , They are the heat flow on the carbon fiber composite workpiece side and the tool back face side. represents the heat flow along the interface caused by friction sliding, is the proportional coefficient of heat transferred to the carbon fiber composite workpiece, is the thermal contact conductivity between the tool back face and the carbon fiber composite workpiece, satisfying: ;in, , are the thermal conductivity of carbon fiber composite workpiece and tool respectively. , is the temperature of carbon fiber composite workpiece and tool.

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