Quasi-continuous laser ring cutting carbon-carbon composite material simulation method considering multiple reflections

Abstract

The invention discloses a quasi-continuous laser ring cutting carbon-carbon composite material simulation method considering multiple reflections, belongs to the field of material processing numerical simulation, and relates to a quasi-continuous laser ring cutting carbon-carbon composite material simulation method considering multiple reflections. According to the method, on the basis of COMSOL Multiphysics software, a ray tracing method is adopted to carry out accurate simulation on multiple reflections of laser. Firstly, a carbon-carbon composite material macroscopic homogeneous model is created, and then a quasi-continuous laser girdling heat source model is constructed. Laser multiple reflections are simulated based on a ray tracing method, a control equation is constructed, and boundary conditions are set. A continuous laser heat source is reasonably simplified, and the solving difficulty of the model is effectively reduced. And finally, solving the model to obtain the ablation morphology of the quasi-continuous laser ring cutting carbon-carbon composite material. The method has relatively high solving efficiency, the prediction accuracy of the model on the ablation morphology is remarkably improved, and a reliable theoretical basis and an analysis basis are provided for deeply revealing a laser processing forming mechanism of the carbon-carbon composite material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of numerical simulation of material processing, and relates to a simulation method for quasi-continuous laser ring cutting of carbon-carbon composite materials considering multiple reflections. BACKGROUND

[0002] Carbon-carbon composite materials have high specific strength and specific modulus, low thermal expansion coefficient, high temperature resistance and wear resistance, and resistance to thermal ablation and thermal shock, and are widely used as key component materials in the aerospace industry. However, carbon-carbon composite materials are typical difficult-to-machine materials, and their inherent high hardness, high brittleness and strong anisotropy make them prone to cracks, delamination, burrs and other machining defects during machining. Laser drilling technology, as a highly efficient, high-precision and highly flexible non-contact machining method, has become one of the most promising machining methods for carbon-carbon composite material drilling.

[0003] However, there are still problems such as large hole taper and poor surface quality in quasi-continuous laser ring cutting of carbon-carbon composite materials, which seriously restricts the large-scale application of this technology in high-end fields with high precision and reliability requirements. The core reason for the long-term difficulty in solving the above machining quality problems is that the ablation morphology forming mechanism of laser machining of carbon-carbon composite materials has not been clearly revealed. Due to the small laser processing area, local high temperature and extremely short time span, it is difficult to directly observe the internal physical process through experimental means. Therefore, finite element simulation method is used to study the ablation morphology forming mechanism of laser machining of carbon-carbon composite materials. When constructing the finite element model, accurately introducing key influencing factors is the key to improving the prediction accuracy of the model.

[0004] Prior art document 1: Huang Yizhou et al. patent CN119026415A "Multi-field coupling near-field dynamics simulation method for surface ablation morphology simulation", which comprehensively considers the effects of structural heat transfer and thermal chemical reaction ablation, and couples the above two physical fields to make a more accurate simulation of the surface ablation morphology of carbon-carbon composite materials. Prior art document 2: QI Lehua et al. patent CN119517242A "Ablation morphology prediction method for C / C composite materials considering complex microstructure", which considers the influence of material microstructure on ablation morphology to improve the prediction accuracy of the model.

[0005] Multiple reflections of laser on the ablation surface are the core factors to determine the final hole shape. With the continuous evolution of the ablation surface, the laser incidence angle will change dynamically, which will affect the laser absorption rate of the material. However, the existing research model rarely considers the influence of multiple reflections on the ablation morphology of carbon-carbon composite materials, resulting in inaccurate prediction of the ablation morphology. Therefore, it is urgent to develop a quasi-continuous laser ring cutting carbon-carbon composite material simulation method considering multiple reflections to improve the prediction accuracy of the ablation morphology of the quasi-continuous laser ring cutting carbon-carbon composite material model, and provide reliable theoretical support for in-depth understanding of the laser processing forming mechanism of carbon-carbon composite materials. SUMMARY

[0006] The present application aims to improve the prediction accuracy of the ablation morphology of the quasi-continuous laser ring cutting carbon-carbon composite material model. In view of the multiple reflection effect of laser in the ablation hole during processing, a quasi-continuous laser ring cutting carbon-carbon composite material simulation method considering multiple reflections is proposed. Based on COMSOL Multiphysics software, the geometric optics and solid heat transfer physical field are coupled, and the core factor of laser multiple reflections is included in the prediction model. First, the quasi-continuous laser heat source is reasonably simplified to reduce the difficulty of solving the model. Then, the ray tracing method is used to simulate the multiple reflections of laser to improve the accuracy of the model in predicting the ablation morphology. This method not only can accurately predict the ablation morphology, but also has high solving efficiency, which is of great significance to reveal the laser processing forming mechanism of carbon-carbon composite materials.

[0007] The technical scheme adopted by the present application is a quasi-continuous laser ring cutting carbon-carbon composite material simulation method considering multiple reflections, characterized by constructing a heat source model that can dynamically simulate the multiple reflection process of laser on the ablation surface through the ray tracing method, which significantly improves the prediction accuracy of the model for the ablation morphology.

[0008] The specific method adopted by the present application includes the following steps:

[0009] Step 1: Create a macro-homogeneous model of carbon-carbon composite material.

[0010] First, a macro-homogeneous geometric model of carbon-carbon composite material is established in the finite element software COMSOL Multiphysics: enter the main interface of the software, select "Model Wizard", select "Two-dimensional" for spatial dimension, and establish a rectangle with length l and width b as the geometric model.

[0011] The anisotropy of carbon fiber leads to the macroscopic anisotropy of carbon-carbon composite material, which is specifically manifested in the significant difference in physical properties of the material in the parallel fiber direction and the vertical fiber direction. Therefore, when defining the material property parameters, the arrangement direction of the fiber should be considered. Correspondingly, the material thermal conductivity matrix is rotated to define the arrangement direction of different fibers.

[0012] Next, boundary mesh nodes are generated on the laser-affected surface, so that the laser-irradiated area is discretized into k mesh nodes. r Each sub-region is then divided into meshes using free triangular meshes.

[0013] Step 2: Construct a quasi-continuous laser circumferential heat source model.

[0014] Quasi-continuous lasers are a type of pulsed laser, which outputs periodic pulses. The duration and interruption of these pulses can be represented by a switching quantity Q(t).

[0015]

[0016] Where t is time, τ is pulse width, and T p This is the pulse period.

[0017] The quasi-continuous laser circumferential cutting process of carbon-carbon composite materials is as follows: The laser moves relative to the carbon-carbon composite material along a designated circular trajectory. The material absorbs the laser energy and sublimates, eventually causing material to detach from the area enclosed by the circular trajectory, forming a through-hole. For ease of description, a three-dimensional Cartesian coordinate system is established as follows: the center of the circular trajectory is the origin, the direction of the surface fiber is the x-axis, the direction perpendicular to the surface fiber is the y-axis, and the material thickness direction is the z-axis. The three axes satisfy the right-hand rule, and the positive direction of the z-axis is defined as being away from the interior of the material.

[0018] This model defines the xoz plane as the analysis plane, used to characterize the kerf morphology of laser-cut carbon-carbon composites. When the distance between the laser spot center and the analysis plane is equal to the laser spot radius r... s At that time, the laser heat source begins to irradiate the analysis plane; when the center of the laser spot passes through the analysis plane and reaches a distance r again... s At this point, the laser heat source irradiation ends. Within this range, the laser directly irradiates the analysis plane, significantly affecting it; when the laser irradiation position exceeds this range, only a small amount of heat acts on the analysis plane through thermal conduction, and its effect is negligible. Therefore, this invention constructs a laser heat source for directly irradiating the xoz plane.

[0019] The laser's moving velocity v can be decomposed along both the x-axis and y-axis. The movement along the x-axis changes the coordinates of the heat source center x0, while the movement along the y-axis changes the peak power density I(y0) of the laser in the xoz plane. Therefore, the two-dimensional quasi-continuous laser heat source model can be expressed as:

[0020]

[0021] The variables can be represented by the following formula:

[0022]

[0023] Where x represents the spatial coordinates of the two-dimensional model, y represents the equivalent action scale of the y-axis in the three-dimensional rectangular coordinate system, I(y0) is the peak power density of the laser in the xoz plane, (x0, y0) are the coordinates of the laser heat source center, and r s R0 is the laser spot radius, θ is the central angle corresponding to the laser movement path, R0 is the laser circumference radius, v is the laser movement speed, P is the laser power, and N is a non-negative integer (N=0,1,2,3…).

[0024] Step 3: Simulate multiple laser reflections based on ray tracing methods.

[0025] Based on the principles of geometric optics, the propagation path of a laser beam can be represented as:

[0026]

[0027] in, These represent the incident direction, reflection direction, and unit normal vector of the laser beam at the laser ablation boundary, respectively.

[0028] During multiple reflections, each reflection is accompanied by Fresnel energy absorption. The Fresnel absorptivity α is a function of the incident angle of the laser beam and can be expressed as:

[0029]

[0030] The incident angle θ1 of the laser beam can be expressed as:

[0031]

[0032] The laser beam refraction angle θ2 can be calculated using the following formula:

[0033]

[0034] Where n1 and n2 are the refractive index of air and the complex refractive index of the material, respectively.

[0035] According to the law of conservation of energy, the total power of a single laser beam propagating in an ideal medium remains constant. However, due to the continuous evolution of the material surface morphology, the area affected by the laser beam changes constantly, leading to a change in the laser power density acting on the material surface. Since the laser irradiation area on the material surface is discretized into multiple sub-regions by mesh nodes, for the i-th sub-region (i=1,2…k)... r ), whose side length on the material surface is l(x) i If ,t), then the laser power density absorbed by the material is q(x). i ,t) can be represented as:

[0036]

[0037] Where, q 0j (x i ,t),a j (x i ,t) represent the power density of the j-th laser beam acting on the sub-region and the absorption rate of the material in the region, respectively, j=1,2…m, where m is the number of laser beams acting on the sub-region.

[0038] Step 4: Construct the governing equations and set the boundary conditions.

[0039] Quasi-continuous lasers are long-pulse lasers. In the processing of carbon-carbon composite materials using long-pulse lasers, the internal heat conduction of the material is dominated by phonons. Therefore, the internal heat conduction of the material can be described using the Fourier heat transfer equation:

[0040]

[0041] Where ρ is the material density, c is the material specific heat capacity, T is the material temperature, and k is the material thermal conductivity.

[0042] For a two-dimensional Cartesian system, the governing equations can be rewritten as:

[0043]

[0044] Where z represents the spatial coordinates of the two-dimensional model, and k x k z denoted as the thermal conductivity of the material in the x and z directions.

[0045] The laser heat source is applied to the laser-irradiated boundary in the form of heat flux. This boundary is simultaneously affected by the convective heat transfer of the auxiliary gas and absorbs the latent heat of phase transition during the phase transition of the material. Therefore, the thermal boundary condition of the laser-irradiated surface can be expressed as:

[0046]

[0047] The variables can be represented by the following formula:

[0048]

[0049] Where, q v The energy loss is caused by material sublimation, h1 is the forced convection heat transfer coefficient between the material surface and the auxiliary gas, and T0 is the ambient temperature. L is the material sublimation mass flow rate per unit area. v P represents the latent heat of sublimation of the material, β represents the mass reflux rate during the sublimation process, and P represents the mass reflux rate during the sublimation process. v Where is the saturated vapor pressure, M is the relative molecular mass of the gaseous products formed by the sublimation of the material, R is the ideal gas constant, P0 is the local atmospheric pressure, and T is the saturated vapor pressure. vThe sublimation temperature of the material.

[0050] Furthermore, phase transitions not only lead to energy loss in the system but also to a loss of material mass. This mass loss can be described by the material removal rate. According to the law of conservation of mass, the lost mass equals the sublimated mass, therefore the material removal rate v... n It can be represented as:

[0051]

[0052] For surfaces not exposed to laser radiation, only affected by environmental convection, their boundary conditions can be expressed as follows:

[0053]

[0054] Where h2 is the natural convection heat transfer coefficient between the material surface and the ambient air.

[0055] Step 5: Solve the model.

[0056] Input laser processing parameters: laser power P, pulse width τ, pulse period T p And the laser moving speed v. Solve the model to finally obtain the ablation morphology of laser-cut carbon-carbon composite materials under a specific combination of processing parameters.

[0057] The beneficial effects of this invention are as follows: A quasi-continuous laser circumferential cutting simulation method for carbon-carbon composites, considering the multiple reflection effect within the ablation hole during laser processing, is proposed. This method establishes a two-dimensional quasi-continuous laser circumferential cutting heat source model through reasonable simplification, transforming the three-dimensional heat source into a two-dimensional model, significantly reducing the numerical solution difficulty. Simultaneously, the ray tracing method is used to accurately simulate the laser multiple reflection effect, improving the model's accuracy in predicting ablation morphology. The dynamic influence of multiple reflections on energy absorption from the material surface is fully considered, thus achieving accurate prediction of ablation morphology. Furthermore, the quasi-continuous laser heat source model is reasonably simplified, reducing the model's solution difficulty. This method introduces the key influencing factor of laser multiple reflection effect into the model, significantly improving the model's accuracy in predicting ablation morphology, and providing a reliable theoretical basis and analytical foundation for further revealing the laser processing forming mechanism of carbon-carbon composite materials. Attached Figure Description

[0058] Figure 1 This is a flowchart of a simulation method for quasi-continuous laser circumferential cutting of carbon-carbon composite materials that considers multiple reflections.

[0059] Figure 2 Simulation and experimental results of quasi-continuous laser circumferential cutting of carbon-carbon composite materials under the conditions of laser power of 450W, pulse width of 0.2ms, pulse period of 2ms, and laser moving speed of 10mm / s are presented. Figure 2a) is the model without considering multiple reflections, b) is the model considering multiple reflections, and c) is the ablation morphology obtained from the experiment. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below in conjunction with the technical solutions and accompanying drawings.

[0061] Appendix Figure 1 This is a flowchart of a finite element simulation method for laser-cut carbon-carbon composite materials considering multiple reflections. This invention introduces multiple laser reflections into the model, making the prediction of ablation morphology more accurate. This method addresses the problem that existing finite element simulation models for laser processing of carbon-carbon composite materials do not consider multiple laser reflections on the ablation surface, leading to inaccurate predictions of ablation morphology. Based on COMSOL Multiphysics software, a two-dimensional quasi-continuous laser-cutting heat source model is established through reasonable simplification, effectively reducing the model's solution difficulty. Simultaneously, ray tracing is used to accurately simulate multiple laser reflections. The quasi-continuous laser heat source is reasonably simplified, effectively reducing the model's solution difficulty. Finally, the model is solved, obtaining the ablation morphology of the quasi-continuous laser-cut carbon-carbon composite material. This method not only accurately predicts the ablation morphology but also has high solution efficiency, which is of great value for in-depth research into the laser processing forming mechanism of carbon-carbon composite materials.

[0062] This embodiment uses a quasi-continuous laser circumferential cutting of a hole with a radius of 0.5 mm as an example to illustrate the simulation process of this method in detail.

[0063] The specific steps of this method are as follows:

[0064] Step 1: Create a macroscopic homogeneous model of carbon-carbon composite materials.

[0065] First, a macroscopic homogeneous geometric model of carbon-carbon composite material is established in the finite element software COMSOL Multiphysics: Enter the main interface of the software, select "Model Wizard", select "2D" for the spatial dimension, and establish a rectangle with a length l of 1mm and a width b of 4mm as the geometric model.

[0066] The anisotropy of carbon fibers leads to macroscopic anisotropy in carbon-carbon composites, specifically manifested as significant differences in physical properties along the fiber-parallel and fiber-perpendicular directions. Therefore, the fiber orientation must be considered when defining material properties. Accordingly, different fiber orientations are defined by rotating the material's thermal conductivity matrix. This embodiment uses a carbon-carbon composite laminate with an orientation of [0° / 60° / -60°], where the thermal conductivity along the fiber-parallel direction is... for Thermal conductivity perpendicular to the fiber direction for Therefore, from the top layer to the bottom layer, the rotation angles of the material thermal conductivity matrix are 0°, 60°, -60°, and -60°, respectively.

[0067] Next, boundary mesh nodes are generated on the laser-affected surface, so that the laser-irradiated area is discretized into k mesh nodes. r There are several sub-regions, here we take k. r The value is 20. Then, a free triangular mesh is used to mesh the geometric model, with the mesh cell size set to "ultra-fine".

[0068] Step 2: Construct a quasi-continuous laser circumferential heat source model.

[0069] Quasi-continuous lasers are pulsed lasers, which output periodic pulses. The duration and interruption of the pulses can be represented by formula (1):

[0070]

[0071] The quasi-continuous laser circumferential cutting process of carbon-carbon composite materials is as follows: The laser moves relative to the carbon-carbon composite material along a designated circular trajectory. The material absorbs the laser energy and sublimates, eventually causing material to detach from the area enclosed by the circular trajectory, forming a through-hole. For ease of description, a three-dimensional Cartesian coordinate system is established as follows: the center of the circular trajectory is the origin, the direction of the surface fiber is the x-axis, the direction perpendicular to the surface fiber is the y-axis, and the material thickness direction is the z-axis. The three axes satisfy the right-hand rule, and the positive direction of the z-axis is defined as being away from the interior of the material.

[0072] This model defines the xoz plane as the analysis plane, used to characterize the kerf morphology of laser-cut carbon-carbon composites. When the distance between the laser spot center and the analysis plane is equal to the laser spot radius r... s At that time, the laser heat source begins to irradiate the analysis plane; when the center of the laser spot passes through the analysis plane and reaches a distance r again... s At this point, the laser heat source irradiation ends. Within this range, the laser directly irradiates the analysis plane, significantly affecting it; when the laser irradiation position exceeds this range, only a small amount of heat acts on the analysis plane through thermal conduction, and its effect is negligible. Therefore, this invention constructs a laser heat source for directly irradiating the xoz plane.

[0073] The laser's moving velocity v can be decomposed along both the x-axis and y-axis. The movement along the x-axis changes the coordinates of the heat source center x0, while the movement along the y-axis changes the peak power density I(y0) of the laser in the xoz plane. Therefore, the two-dimensional quasi-continuous laser heat source model can be expressed by formula (2):

[0074]

[0075] Each variable can be represented by formula (3):

[0076]

[0077] Wherein, the laser spot radius r s The diameter is 36.8 μm, the laser circumferential cutting radius R0 is 0.5 mm, and N = 0, 1, 2, 3….

[0078] Step 3: Simulate multiple laser reflections based on ray tracing methods.

[0079] Based on the principles of geometric optics, the propagation path of laser light can be determined using formula (4). This indicates that during multiple reflections, each reflection is accompanied by Fresnel energy absorption. The Fresnel absorptivity α is a function of the incident angle of the laser beam and can be expressed by formula (5):

[0080]

[0081] Wherein, the refractive index of air n1 is 1, the complex refractive index of carbon-carbon composite material n2 = 1.62 + 0.75j, and the incident angle θ1 of the laser beam is calculated using formula (6). This indicates that the laser beam refraction angle θ2 is calculated according to formula (7). calculate.

[0082] According to the law of conservation of energy, the total power of a single laser beam propagating in an ideal medium remains constant. However, due to the continuous evolution of the material surface morphology, the area affected by the laser beam changes constantly, leading to a change in the laser power density acting on the material surface. Since the mesh nodes divide the laser irradiation area into 20 sub-regions, for the i-th sub-region (i=1,2…20), the laser power density absorbed by the material is q(x). i ,t) can be expressed by formula (8):

[0083]

[0084] Step 4: Construct the governing equations and set the boundary conditions.

[0085] Quasi-continuous lasers belong to long-pulse lasers. In the process of long-pulse laser processing of carbon-carbon composite materials, the internal heat conduction of the material is dominated by phonons. Therefore, the internal heat conduction of the material can be described by the Fourier heat transfer equation. For a two-dimensional Cartesian system, the governing equation can be expressed by formula (10):

[0086]

[0087] The material density ρ is 1.65 g / cm³. 3The specific heat capacity of the material is c. .

[0088] The laser heat source is applied to the laser irradiation boundary in the form of heat flux. This boundary is simultaneously affected by the convective heat transfer of the auxiliary gas and absorbs the latent heat of phase change when the material undergoes a phase change. Therefore, the thermal boundary condition of the laser irradiation surface can be expressed by formula (11):

[0089]

[0090] Each variable can be represented by formula (12):

[0091]

[0092] The forced convection heat transfer coefficient h1 between the material surface and the auxiliary gas is 30 W / m. 2 The ambient temperature T0 is 293.15 K, the mass reflux rate β during the material sublimation process is 0.18, the relative molecular mass M of the gaseous product (C2) formed by the material sublimation is 24 g / mol, the ideal gas constant R is 8.314 J / (K·mol), the local atmospheric pressure P0 is 0.1 MPa, and the material sublimation temperature T is [missing value]. v It is 3958K.

[0093] Furthermore, phase transitions not only lead to energy loss in the system but also to a loss of material mass. This mass loss can be described by the material removal rate. According to the law of conservation of mass, the lost mass equals the sublimated mass, therefore the material removal rate v... n It can be expressed using formula (13):

[0094]

[0095] The non-laser-irradiated surface is only affected by environmental convection, and its boundary conditions can be expressed by formula (14):

[0096]

[0097] The natural convection heat transfer coefficient h2 between the material surface and the ambient air is 10 W / m. 2 / K.

[0098] Step 5: Solve the model.

[0099] Input laser processing parameters: laser power P = 450W, pulse width τ = 0.2ms, pulse period T = 0.2ms. p The laser traverse time is 2ms and the laser moving speed v is 10mm / s. The model is solved to obtain the ablation morphology of laser-cut carbon-carbon composite material under a specific combination of processing parameters. Figure 2This presents the simulation and experimental results of the kerf morphology of quasi-continuous laser circumferential cutting of carbon-carbon composite materials under this parameter combination. Among them, Figure 2 (a) is the model without considering multiple reflections, (b) is the model considering multiple reflections, and (c) is the ablation morphology obtained from the experiment.

[0100] The results show that the model without considering multiple reflections has a large deviation in predicting the ablation morphology, while the model considering multiple reflections is consistent with the experimental ablation morphology, proving that the introduction of multiple reflections improves the accuracy of the model in predicting the ablation morphology.

Claims

1. A quasi-continuous laser circumferential cutting carbon-carbon composite material simulation method considering multiple reflections, characterized in that, By the light ray tracing method, a heat source model capable of dynamically simulating the multiple reflection process of laser on the ablation surface is constructed, and the prediction accuracy of the model for the ablation morphology is improved; the specific steps of the method are as follows: Step 1: Create a macro-homogeneous model of carbon-carbon composite material; Firstly, a macro-homogeneous geometric model of carbon-carbon composite material is established in the finite element software COMSOL Multiphysics: enter the software main interface, select "Model Wizard", select "Two-dimensional" for spatial dimension, and establish a rectangle with a length of l and a width of b as the geometric model; The anisotropy of carbon fiber itself leads to the macroscopic anisotropy of carbon-carbon composite material, which is manifested as the significant difference in physical properties of the material in the parallel fiber direction and the vertical fiber direction; Therefore, the arrangement direction of the fibers should be considered when defining the material physical property parameters; accordingly, the arrangement direction of different fibers is defined by rotating the thermal conductivity matrix of the material; first, the boundary grid nodes are generated on the laser action surface, so that the laser irradiation area is discretized into k r sub-areas by the grid nodes; then, the free triangular grid is used to divide the geometric model into grids. Step 2: Build quasi-continuous laser ring cutting heat source model; Quasi-continuous laser belongs to pulsed laser, which outputs in the form of periodic pulses, and the duration and off of the pulse is represented by the switch quantity Q(t): where t is time, τ is pulse width, T p is the pulse period; The process of quasi-continuous laser ring cutting carbon-carbon composite material is as follows: the laser moves along the specified circular trajectory relative to the carbon-carbon composite material, the material absorbs laser energy and sublimates, and finally the material in the region contained by the circular trajectory falls off to form a through hole; a three-dimensional rectangular coordinate system is established, taking the center of the circular trajectory as the coordinate origin, the fiber direction of the material surface layer as the x-axis, the direction perpendicular to the fiber direction of the material surface layer as the y-axis, and the material thickness direction as the z-axis, which satisfy the right-hand rule, and it is specified that the positive direction of the z-axis is away from the material interior; This model defines the xoz plane as the analysis plane, used to characterize the kerf morphology of laser-cut carbon-carbon composite materials; when the distance between the laser spot center and the analysis plane is the laser spot radius r... s At that time, the laser heat source begins to irradiate the analysis plane; when the center of the laser spot passes through the analysis plane and reaches a distance r again... s When the laser heat source irradiation ends, the laser directly irradiates the analysis plane within this range, significantly affecting the analysis plane. When the laser irradiation position exceeds this range, only a small amount of heat acts on the analysis plane through heat conduction, and its effect is negligible. Therefore, this invention constructs a laser heat source that directly irradiates the xoz plane. The laser moving speed v is decomposed along the x-axis and y-axis directions; among them, the movement in the x-axis direction changes the heat source center coordinate x0, and the movement in the y-axis direction changes the peak power density I(y0) of the laser in the xoz plane; therefore, the two-dimensional quasi-continuous laser heat source model is represented as: Wherein, each variable can be represented by the following formula: wherein x is a spatial coordinate of the two-dimensional model, y is an equivalent action scale of the y-axis in a three-dimensional rectangular coordinate system, I(y0) is a peak power density of the laser in the xoz plane, (x0, y0) is a center coordinate of the laser heat source, r s is a laser spot radius, theta is a central angle corresponding to the laser movement path, R0 is a laser circumcircle radius, v is a laser movement speed, P is a laser power, and N is a non-negative integer (N=0, 1, 2, 3…). Step 3: Simulate multiple reflections of laser based on light ray tracing method; Based on the principle of geometric optics, the propagation path of laser light is represented as: wherein respectively the direction of incidence, the direction of reflection and the unit normal vector of the laser ablation boundary of the laser light ray; In the process of multiple reflections, each reflection is accompanied by Fresnel energy absorption; the Fresnel absorption rate a is a function of the incidence angle of the laser beam, and is represented as: Wherein, the incidence angle of the laser light θ1 can be represented as: The refraction angle of the laser light θ2 is calculated by the following formula: Wherein, n1 and n2 are the refractive index of air and the complex refractive index of the material, respectively; According to the law of conservation of energy, the total power of a single laser light propagating in an ideal medium remains constant; but due to the continuous evolution of the material surface morphology, the action area of the laser light changes constantly, resulting in changes in the laser power density acting on the material surface; due to the fact that the laser irradiation area of the material surface is discretized into multiple sub-areas by grid nodes, for the ith sub-area (i = 1, 2…k r ), whose side length is l(x i ,t) on the material surface, the laser power density absorbed by the material q(x i ,t) is expressed as: wherein q 0j (x i ,t), a j (x i ,t) are the power density of the jth laser light acting on the sub-region and the absorption rate of the material in the interval, respectively, j = 1, 2, …, m, and m is the number of laser lights acting on the sub-region. Step 4: Build control equation and set boundary conditions; Quasi-continuous laser belongs to long pulse laser, and in the process of long pulse laser machining carbon-carbon composite material, the heat conduction in the material is dominated by phonons; therefore, the heat conduction in the material is described by the Fourier heat conduction equation: Wherein, p is the material density, c is the specific heat capacity of the material, T is the material temperature, and k is the thermal conductivity of the material; For a two-dimensional Cartesian system, the control equation is rewritten as: where z is the spatial coordinate of the two-dimensional model, k x , k z are the thermal conductivity coefficients of the material in the x, z directions; The laser heat source is applied on the laser irradiation boundary in the form of heat flux, which is affected by the convection heat transfer of the auxiliary gas at the same time, and absorbs the latent heat of phase change when the material undergoes phase change, so the thermal boundary condition of the laser irradiation surface is expressed as: Wherein, each variable is expressed by the following formula: wherein q v is the energy loss caused by material sublimation, h1 is the forced convection heat transfer coefficient between the material surface and the auxiliary gas, T0 is the ambient temperature, is the mass flow rate of material sublimation per unit area, L v is the latent heat of material sublimation, β is the mass reflux rate in the material sublimation process, P v is the saturated vapor pressure, M is the relative molecular mass of the gaseous product formed by material sublimation, R is the ideal gas constant, P0 is the local atmospheric pressure, T v is the material sublimation temperature; In addition, the phase transition not only causes the loss of system energy, but also causes the loss of material mass itself; the loss of material mass can be described by the material removal rate; according to the law of conservation of mass, the lost material mass is equal to the sublimation mass, so the material removal rate v n is represented as: The non-laser irradiation surface is only affected by the environment convection, and its boundary condition is expressed as: Wherein, h2 is the natural convection heat transfer coefficient between the material surface and the environment air; Step 5: model solving; Input laser processing parameters: laser power P, pulse width τ, pulse period T p and laser moving speed v; solve the model, and finally obtain the ablation morphology of laser ring cutting carbon / carbon composite materials under a specific combination of processing parameters.

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