Simulation method and system for temperature field and stress field of short pulse laser irradiation material

Abstract

The invention belongs to the technical field of laser and substance interaction, and relates to a simulation method and system for a temperature field and a stress field of a short-pulse laser irradiation material. The simulation method comprises the following steps: determining simulation parameters including short pulse laser irradiation parameters and material attribute parameters; constructing a thermal-mechanical coupling transient model of the material, and determining boundary conditions of a heat transfer physical field and a solid mechanics physical field of the model; meshing division is carried out on the thermal coupling transient model, and solver parameters are configured; the method specifically comprises the following steps: inputting a short pulse laser pulse width and a short pulse laser frequency into a pre-trained linear neural network model, and calculating to obtain solver parameters; and solving the thermal coupling transient model by applying a solver to obtain temperature field and stress field distribution conditions of the material at different irradiation moments. According to the simulation method, the complex transient physical process of the material under the action of the short pulse laser can be comprehensively and accurately captured.

Description

Technical Field

[0001] The present invention relates to the technical field of laser-matter interaction, and in particular to a method and system for simulating temperature field and stress field of a material irradiated by a short-pulse laser. Background Art

[0002] In the technical field of laser-matter interaction, short-pulse laser irradiation can achieve effective ablation of materials due to its high power density. Therefore, short-pulse laser is widely used in laser processing, laser damage and other aspects.

[0003] Generally, by controlling laser parameters such as pulse width, spot radius, laser energy and other parameters, effective control of material ablation effects, such as ablation depth, ablation quality, ablation area, etc., can be achieved. Temperature field and stress field are two key physical quantities that can reflect the specific conditions of laser ablation of materials. By monitoring the temperature field and stress field conditions, a basis can be provided for optimizing the design of laser irradiation ablation parameters, thereby achieving the purpose of controlling the ablation effect.

[0004] However, in high-energy short-pulse lasers (energy density ≥ In the numerical simulation of irradiated materials (with pulse width ≤ 500ns), conventional finite element simulation methods face significant technical bottlenecks. magnitude) and extreme thermomechanical coupling effects (temperature gradients > , strain rate> ), using the default COMSOL solver parameters will lead to the following problems: First, the adaptive time step control strategy is based on the conventional thermodynamic process design, which is prone to produce too large a time step in the transient response stage and cannot accurately capture the precise changes in physical properties; second, a smaller time step strategy is prone to lead to a huge amount of calculation; how to balance the fine physical characteristics of the transient response stage while reducing the amount of calculation in the subsequent relaxation stage requires optimizing the solver parameters so as to better obtain the temperature field and stress field results of the short-pulse laser irradiated material. Summary of the invention

[0005] The purpose of the present invention is to optimize the laser parameter design to accurately obtain the laser irradiation material effect under various working conditions. A simulation method and system for the temperature field and stress field of short-pulse laser irradiated materials are proposed. The complex physical processes such as heat conduction inside the material, convection heat transfer between the surface and the environment, and thermal expansion of the material under the action of short-pulse laser are analyzed to obtain the temperature field and stress field distribution of the material under short-pulse laser irradiation.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: In a first aspect, the present invention provides a method for simulating the temperature field and stress field of a material irradiated by a short pulse laser, the simulation method comprising the following steps: Determine simulation parameters, including short pulse laser irradiation parameters and material property parameters; Construct a thermal-mechanical coupling transient model of the material and determine the boundary conditions of the heat transfer physics field and solid mechanics physics field of the thermal-mechanical coupling transient model; The thermomechanical coupling transient model is meshed based on the heat transfer physics field and the solid mechanics physics field, and the solver parameters are configured; the solver parameters include the initial step size, the maximum step size constraint, and the time step for storing a calculation result; the solver parameters are determined by using a pre-trained linear neural network model, specifically: the short pulse laser pulse width and short pulse laser frequency are input into the pre-trained linear neural network model, and the calculation expression of the pre-trained linear neural network model is used to calculate and obtain the solver parameters; The solver is used to solve the thermal-mechanical coupling transient model to obtain the temperature field and stress field distribution of the material at different irradiation times.

[0007] As a possible implementation method, the pre-trained linear neural network model includes an input layer and an output layer; wherein the parameters of the input layer include a short pulse laser pulse width node and a short pulse laser frequency node; the parameters of the output layer include an initial step node, a maximum step constraint node, and a time step node for storing a calculation result.

[0008] As a possible implementation method, the computational expression of the pre-trained linear neural network model is: ; in, is the weight matrix, ; is the bias vector, ; is the initial step length; The time step for storing a calculation result; is the maximum step length constraint; is the short pulse laser pulse width; is the short pulse laser frequency.

[0009] As a possible implementation method, the parameters of the input layer and the parameters of the output layer are normalized, and the normalization range is [0, 1]; the normalized expression is: ; in, is the normalized result of the corresponding parameter value in the training data set; is the corresponding parameter value in the training data set; and are the minimum and maximum values ​​of the corresponding parameters in the training data set, respectively.

[0010] As a possible implementation, The parameters must satisfy physical constraints: ; If the prediction results do not meet the above constraints, they should be corrected in the following ways: .

[0011] As a possible implementation, the total calculation step of the solver is the short pulse laser pulse width 20-50 times of.

[0012] As a possible implementation method, meshing adopts free triangle partitioning, and the mesh unit size is predefined as ultra-fine.

[0013] As a possible implementation, the pulse width of the short pulse laser is in the range of 100ps-500ns.

[0014] In a second aspect, the present invention provides a simulation system for temperature field and stress field of a material irradiated by a short pulse laser, specifically comprising: A simulation parameter configuration unit, used to configure simulation parameters, the simulation parameters including short pulse laser irradiation parameters and material property parameters; A thermal-mechanical coupling transient model building unit for materials is used to build a thermal-mechanical coupling transient model for materials and determine the boundary conditions of the heat transfer physical field and the solid mechanics physical field of the thermal-mechanical coupling transient model; Meshing unit, which meshes the thermal-mechanical coupling transient model based on the heat transfer physics and solid mechanics physics; A solver parameter configuration unit is used to configure solver parameters, including an initial step size, a maximum step size constraint, and a time step for storing a calculation result. The solver parameters are determined by using a pre-trained linear neural network model, specifically: the short pulse laser pulse width and the short pulse laser frequency are input into the pre-trained linear neural network model, and the calculation expression of the pre-trained linear neural network model is applied to calculate and obtain the solver parameters. The temperature field and stress field distribution of the material are determined by the unit, and the thermal-mechanical coupling transient model is solved by the solver to obtain the temperature field and stress field distribution of the material at different irradiation times.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention proposes a method for simulating the temperature field and stress field of a material irradiated by a short pulse laser. The method can analyze complex physical processes such as heat conduction inside the material, convection heat transfer between the surface and the environment, and thermal expansion of the material under the action of a short pulse laser for different short pulse laser parameters and different materials, and obtain the temperature field and stress field distribution of the material under short pulse laser irradiation.

[0016] 2. The present invention proposes a method for simulating the temperature field and stress field of a material irradiated by a short pulse laser, which can analyze the distribution of the temperature field and stress field at different irradiation moments, thereby reducing the experimental cost and shortening the experimental cycle.

[0017] 3. The present invention proposes a method for simulating the temperature field and stress field of a short-pulse laser irradiated material, which obtains the effects of laser irradiation on the material under various working conditions and provides a technical means for the optimization design of laser parameters.

[0018] 4. The solver parameter optimization setting method proposed in the present invention can capture the fine physical characteristics of the transient response stage during short-pulse laser irradiation, reduce the amount of calculation in the laser non-action relaxation stage, and better calculate the temperature field and stress field results of the short-pulse laser irradiated material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 The flowchart of the simulation method of the temperature field and stress field of the material irradiated by short pulse laser; Figure 2 This is a schematic diagram of a laser switch function in an embodiment of the present invention; Figure 3 A schematic diagram of grid division in an embodiment of the present invention; Figure 4 The temperature variation curves at four different coordinate positions ((0 mm, 0 mm), (0.5 mm, 0.5 mm), (1 mm, 1 mm), (2 mm, 2 mm)) on the upper surface of the metal in an embodiment of the present invention; Figure 5 The three irradiation times in the embodiment of the present invention (t1=0s, t2=3.6×10 -7 s, t3=6.7×10 -7 s) Temperature field distribution of materials; Figure 6 The three irradiation times in the embodiment of the present invention (t1=0s, t2=2.5×10 -6 s,t3=5×10 -6s) Thermal expansion displacement distribution of aluminum metal materials; Figure 7 The three irradiation times in the embodiment of the present invention (t1=0s, t2=5×10 -7 s,t3=5×10 -6 s) Thermal stress distribution of metallic aluminum materials. DETAILED DESCRIPTION

[0020] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0021] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0022] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. The following at least one item (items) or similar expressions thereof refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, at least one item (items) of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0023] The embodiment of the present invention aims to provide a method and system for simulating the temperature field and stress field of a material irradiated by a short pulse laser, and by optimizing the design of solver parameters, the complex transient physical phenomena of the laser irradiated material at different times can be fully and accurately captured. The specific implementation methods are as follows: In a first aspect, an embodiment of the present invention provides a method for simulating the temperature field and stress field of a material irradiated by a short pulse laser. Figure 1 , the simulation method comprises the following steps: Determine simulation parameters, including short pulse laser irradiation parameters and material property parameters; As a possible implementation, the pulse width of the short pulse laser is in the range of 100ps-500ns.

[0024] Exemplarily, the laser irradiation center and laser related parameters are shown in Table 1 below; Table 1 Laser irradiation center and laser related parameters Exemplarily, the material property parameters include the melting point, latent heat of fusion, thermal conductivity, density, heat capacity at constant pressure, Young's modulus, absorption coefficient of laser, Poisson's ratio, and thermal expansion coefficient of the material.

[0025] Exemplarily, the materials include metals such as aluminum, iron, copper, zinc, and semiconductor materials such as silicon and germanium.

[0026] Taking aluminum metal as an example, the geometric length L, width W and height H of the aluminum sheet are set to 15 mm, 15 mm and 0.3 mm respectively.

[0027] For example, the aluminum sheet related parameters are shown in Table 2 below; Table 2 Aluminum sheet related parameters Construct a thermal-mechanical coupling transient model of the material and determine the boundary conditions of the heat transfer physics field and solid mechanics physics field of the thermal-mechanical coupling transient model; Exemplarily, a thermal-mechanical coupled transient model of the material is constructed based on COMSOL Multiphysics software.

[0028] Exemplarily, the thermal-mechanical coupling transient model is a three-dimensional multi-physics field model, which is obtained by creating solid heat transfer and solid mechanics modules and performing a thermal-mechanical coupling multi-physics field simulation of laser irradiated materials.

[0029] For example, in the solid heat transfer module, the expression is: ; in, is the density of the material; is the mass heat capacity; Heating rate; is the temperature gradient; is the thermal conductivity of the material; is the internal heat source term.

[0030] For example, in the solid mechanics module, the expression is: ; in, is the material density of the material; is the acceleration term, is the displacement, t is the time; is the internal stress, and its expression is: , C is the fourth-order elastic matrix, is the displacement strain, and its expression is .

[0031] For example, the laser deposits energy on the surface of the material, and the expression is: ; ; in, is the absorption coefficient of the material to the laser; is the spot radius; is the position of any point on the upper surface of the material; is the center position of laser irradiation; t is the time; is the laser switch function, which is used to control the change of the laser on a time scale. This function is a Gaussian pulse function with a peak value of 1 and a standard deviation of the laser pulse width, such as Figure 2 As shown; is the average power of a single laser pulse; E is the energy of a single laser pulse; is the laser pulse width.

[0032] For example, the relationship between the thermal expansion strain of a material and the temperature change is: ; in, is the thermal expansion strain of the material; is the thermal expansion coefficient of the material; is temperature; is the volume reference temperature.

[0033] For example, the surface boundary heat flux for the laser irradiated material is expressed as , satisfying the expression: ; in, is the boundary normal vector; is the laser heat flux; is the heat flux of convective heat transfer between the laser irradiated surface and the environment.

[0034] For the surface boundary heat flux not irradiated by laser All meet the following requirements: The convective heat transfer between the material surface and the environment is: ; Where h is the convective heat transfer coefficient; is the ambient temperature; For temperature.

[0035] The thermomechanical coupling transient model is meshed based on the heat transfer physics and solid mechanics physics, such as Figure 3 As shown; As a possible implementation method, meshing is performed using free triangles, and the mesh unit size is predefined as ultra-fine. When the material shape is a rectangular parallelepiped, sweeping can be used for meshing.

[0036] Configure the solver parameters, including the initial step size, the maximum step size constraint, and the time step for storing a calculation result; the solver parameters are determined by using a pre-trained linear neural network model; specifically, the short pulse laser pulse width and the short pulse laser frequency are input into the pre-trained linear neural network model, and the calculation expression of the pre-trained linear neural network model is applied to calculate and obtain the solver parameters; As a possible implementation method, the pre-trained linear neural network model includes an input layer and an output layer; wherein the parameters of the input layer include a short pulse laser pulse width node and a short pulse laser frequency node; the parameters of the output layer include an initial step node, a maximum step constraint node, and a time step node for storing a calculation result.

[0037] As a possible implementation method, the computational expression of the pre-trained linear neural network model is: ; in, is the weight matrix, ; is the bias vector, ; is the initial step length; The time step for storing a calculation result; is the maximum step length constraint; is the short pulse laser pulse width; is the short pulse laser frequency.

[0038] As a possible implementation method, the parameters of the input layer and the parameters of the output layer are normalized, and the normalization range is [0, 1]; the normalized expression is: ; in, is the normalized result of the corresponding parameter value in the training data set; is the corresponding parameter value in the training data set; and are the minimum and maximum values ​​of the corresponding parameters in the training data set, respectively.

[0039] As a possible implementation, The parameters must satisfy physical constraints: ; If the prediction results do not meet the above constraints, they should be corrected in the following ways: .

[0040] As a possible implementation, the total calculation step of the solver is the short pulse laser pulse width 20-50 times of.

[0041] The solver is used to solve the thermal-mechanical coupling transient model to obtain the temperature field and stress field distribution of the material at different irradiation times.

[0042] During the specific implementation, the initial step size, maximum step size constraint and time step for storing a calculation result in the solver parameters are set according to the pre-trained linear neural network model; for example, in the output time step column of the transient solver study settings, enter range(0, Pulse_Width / 30, Pulse_Width*50), enter Pulse_Width / 5 in the initial step size column of the transient solver, enter Pulse_Width / 20 in the maximum step size constraint column, and the time step for storing a calculation result is Pulse_Width / 30.

[0043] For example, add a probe at the location that needs to be detected, or add a cut point, cut line or cross section to the post-processed data set to obtain the real-time change of temperature at a certain location; when the model is solved, add a drawing group and call the corresponding data set to explore the results.

[0044] like Figure 4 As shown, in this embodiment, the upper surface is selected, and the coordinates of the corresponding two-dimensional intercept points are added as (0 mm, 0 mm), (0.5 mm, 0.5 mm), (1 mm, 1 mm) and (2 mm, 2 mm), and its temperature change curve is plotted in the one-dimensional plot group. In this embodiment, a three-dimensional plot group is added, such as Figure 5 , 6 As shown in Figure 7, the temperature field distribution diagram, thermal expansion displacement distribution diagram and thermal stress distribution diagram of the aluminum sheet are drawn. Figure 5-7 The simulation results can obtain the temperature field distribution, thermal expansion displacement distribution and thermal stress distribution calculation results of the material at different transient moments under short-pulse laser irradiation, and the corresponding physical field parameters can be obtained in real time.

[0045] In a second aspect, the present invention provides a simulation system for temperature field and stress field of a material irradiated by a short pulse laser, specifically comprising: A simulation parameter configuration unit, used to configure simulation parameters, the simulation parameters including short pulse laser irradiation parameters and material property parameters; A thermal-mechanical coupling transient model building unit for materials is used to build a thermal-mechanical coupling transient model for materials and determine the boundary conditions of the heat transfer physical field and the solid mechanics physical field of the thermal-mechanical coupling transient model; Meshing unit, which meshes the thermal-mechanical coupling transient model based on the heat transfer physics and solid mechanics physics; A solver parameter configuration unit is used to configure solver parameters, including an initial step size, a maximum step size constraint, and a time step for storing a calculation result. The solver parameters are determined by using a pre-trained linear neural network model, specifically: the short pulse laser pulse width and the short pulse laser frequency are input into the pre-trained linear neural network model, and the calculation expression of the pre-trained linear neural network model is applied to calculate and obtain the solver parameters. The temperature field and stress field distribution of the material are determined by the unit, and the thermal-mechanical coupling transient model is solved by the solver to obtain the temperature field and stress field distribution of the material at different irradiation times.

[0046] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the illustrations of the drawings. In the specification, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit can implement several functions listed in the specification. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0047] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the present invention and its equivalents.

Claims

1. A method for simulating temperature field and stress field of a material irradiated by a short pulse laser, characterized in that: The simulation method comprises the following steps: Determining simulation parameters, wherein the simulation parameters include short pulse laser irradiation parameters and material property parameters; Construct a thermal-mechanical coupling transient model of the material and determine the boundary conditions of the heat transfer physics field and solid mechanics physics field of the thermal-mechanical coupling transient model; The thermomechanical coupling transient model is meshed based on the heat transfer physics field and the solid mechanics physics field, and the solver parameters are configured; the solver parameters include an initial step size, a maximum step size constraint, and a time step for storing a calculation result; the solver parameters are determined by using a pre-trained linear neural network model, specifically: a short pulse laser pulse width and a short pulse laser frequency are input into the pre-trained linear neural network model, and the calculation expression of the pre-trained linear neural network model is applied to calculate and obtain the solver parameters; The solver is used to solve the thermal-mechanical coupling transient model to obtain the temperature field and stress field distribution of the material at different irradiation times.

2. The method for simulating temperature field and stress field of a material irradiated by a short pulse laser according to claim 1, characterized in that: The pre-trained linear neural network model includes an input layer and an output layer; wherein the parameters of the input layer include a short pulse laser pulse width node and a short pulse laser frequency node; the parameters of the output layer include an initial step node, a maximum step constraint node, and a time step node for storing a calculation result.

3. The method for simulating temperature field and stress field of a material irradiated by short pulse laser according to claim 1, characterized in that: The computational expression of the pre-trained linear neural network model is: ； in, is the weight matrix, ; is the bias vector, ; is the initial step length; The time step for storing a calculation result; is the maximum step length constraint; is the short pulse laser pulse width; is the short pulse laser frequency.

4. The method for simulating temperature field and stress field of a material irradiated by short pulse laser according to claim 2, characterized in that: The parameters of the input layer and the output layer are normalized, and the normalization range is [0, 1]. The normalized expression is: ； in, is the normalized result of the corresponding parameter value in the training data set; is the corresponding parameter value in the training data set; and are the minimum and maximum values ​​of the corresponding parameters in the training data set, respectively.

5. The method for simulating temperature field and stress field of a material irradiated by short pulse laser according to claim 3, characterized in that: The parameters must satisfy physical constraints: ; If the prediction results do not meet the above constraints, they should be corrected in the following ways: .

6. The method for simulating temperature field and stress field of a material irradiated by short pulse laser according to claim 1, characterized in that: The total calculation step length of the solver is the short pulse laser pulse width 20~50 times of.

7. The method for simulating temperature field and stress field of a material irradiated by short pulse laser according to claim 1, characterized in that: The meshing division adopts free triangle division, and the mesh unit size is predefined as ultra-fine.

8. The method for simulating temperature field and stress field of a material irradiated by short pulse laser according to claim 1, characterized in that: The pulse width of the short pulse laser ranges from 100ps to 500ns.

9. A simulation system for temperature field and stress field of short pulse laser irradiated materials, characterized in that: include: A simulation parameter configuration unit, used to configure simulation parameters, wherein the simulation parameters include short pulse laser irradiation parameters and material property parameters; A thermal-mechanical coupling transient model building unit for materials is used to build a thermal-mechanical coupling transient model for materials and determine the boundary conditions of the heat transfer physical field and the solid mechanics physical field of the thermal-mechanical coupling transient model; Meshing unit, which meshes the thermal-mechanical coupling transient model based on the heat transfer physics and solid mechanics physics; A solver parameter configuration unit is used to configure solver parameters, wherein the solver parameters include an initial step size, a maximum step size constraint, and a time step for storing a calculation result; the solver parameters are determined by applying a pre-trained linear neural network model, specifically: a short pulse laser pulse width and a short pulse laser frequency are input into the pre-trained linear neural network model, and a calculation expression of the pre-trained linear neural network model is applied to calculate and obtain the solver parameters; The temperature field and stress field distribution of the material are determined by the unit, and the thermal-mechanical coupling transient model is solved by the solver to obtain the temperature field and stress field distribution of the material at different irradiation times.

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