Laser cutting thermal coupling simulation method
By constructing a laser cutting thermal-mechanical coupling finite element simulation model based on material melting judgment conditions and behavior description criteria, the problem of accurate description of laser cutting simulation in the existing technology is solved, high-precision simulation calculation of the laser cutting process is achieved, and the accuracy of laser cutting effect and deformation prediction is improved.
Patent Information
- Application Number
- CN202510940481.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-09
- Publication Date
- 2025-10-17
AI Technical Summary
Existing laser cutting simulation methods cannot accurately describe the complex physical process of laser cutting, especially the heating of the laser heat source, the heat dissipation of material melting, and the thermal elastic-plastic deformation of the parts after cutting. This makes simulation difficult and makes it impossible to accurately predict the cutting effect and deformation.
A laser cutting thermal-mechanical coupling finite element simulation model including material melting judgment conditions and behavior description criteria is constructed. The temperature and stress distribution during the laser cutting process is accurately described through time-stepping finite element solution.
High-precision simulation calculation of laser cutting is achieved, which accurately describes the process of laser heat source heating, material melting and heat dissipation, and thermal elastic-plastic deformation of parts, thus improving the accuracy and reliability of simulation calculation.
Smart Images
Figure CN120805588A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of laser cutting, and particularly relates to a laser cutting thermal coupling simulation method. BACKGROUND
[0002] The laser cutting process is controllable and clean, is suitable for rapid cutting of complex profiles of various precision parts, and can realize high-quality finishing of the parts. In order to improve the laser cutting machining quality and reduce the cutting deformation caused by heat input, laser cutting simulation is needed to reduce the experimental trial and error cost, but the simulation is difficult because it involves complex mechanisms such as laser heat source heating, material melting and heat dissipation, thermal elastic-plastic deformation, and change of the topological structure of the parts caused by cutting. The traditional finite element simulation method based on the surface Gaussian heat source cannot reflect the material removal caused by cutting and the change of the heat input caused by the laser irradiation on the newly generated surface after the material removal, and therefore, high-precision thermal coupling simulation analysis and research need to be carried out on the laser cutting. SUMMARY
[0003] The application aims at the defects that the existing laser cutting simulation method cannot accurately describe the complex physical process of the laser cutting, the modeling is difficult, and the cutting effect of the three-dimensional moving laser light source on the parts and the deformation condition after the cutting cannot be obtained in the actual laser cutting, and proposes a laser cutting thermal coupling simulation method, which can accurately describe the laser heat source heating, material melting and heat dissipation, material removal in the cutting process and the thermal elastic-plastic deformation process of the parts, effectively realizes the high-precision simulation calculation of the laser cutting, and has important engineering application value.
[0004] The application is realized by the following technical scheme:
[0005] The application relates to a laser cutting thermal coupling simulation method, which is constructed by constructing a laser cutting thermal coupling finite element simulation model including a material melting judgment condition and a material melting behavior description criterion, and obtaining an accurate temperature distribution field and an accurate stress strain field of a structure in a component in a laser cutting process through time step finite element solving.
[0006] The material melting judgment condition refers to that, for each three-dimensional grid element with a size of , , , a real-time temperature of the element reaches a melting point , and a total heat absorption amount of the element satisfies , wherein: is a melting heat.
[0007] The material melting behavior description criteria refer to: for mesh units that meet the material melting judgment conditions in finite element simulation, the unit material properties or boundary condition settings used to reflect their melting behavior in the simulation, including: thermodynamic description criteria, heat transfer description criteria and elastic-plastic mechanics description criteria.
[0008] The thermodynamic description criterion is: the specific heat capacity of the grid unit at constant pressure =1e-5× ,density =1e-5× , indicating that the grid unit no longer stores heat; the heat transfer description criterion is: the natural convection heat transfer coefficient of the grid unit =1e-5× , surface emissivity =1e-5× , the thermal conductivity is set to orthotropic thermal conductivity, and the thermal conductivity parallel to the laser incident direction is set to =1e5 W / (m·K), thermal conductivity perpendicular to the laser incident direction 0 W / (m·K) means that the grid unit no longer exchanges heat freely to the outside, and all the heat generated by laser irradiation is applied to the unmelted units below through the unit. The elastic-plastic mechanics description criterion is: the elastic modulus of the grid unit = 1e-5× , indicating that the surrounding unmelted elements are no longer subject to the loads and constraints of this element.
[0009] The laser cutting thermal-mechanical coupling finite element simulation model is constructed in the following way:
[0010] Step a) Based on the part geometric parameters in the laser cutting simulation input parameters, a geometric model of the cut part is established, and mesh units are divided for finite element calculation, and each mesh unit is assigned a serial number 1, 2, 3, ..., N, where N is the total number of mesh units, and the size of the mesh unit located on the laser cutting path in any direction does not exceed the laser focus radius ;
[0011] The laser cutting simulation input parameters include: laser heat input parameters, part geometry parameters, cutting material parameters and environmental parameters.
[0012] The laser heat input parameters include: cutting laser power , focal radius , cutting speed and thermal efficiency The geometric parameters of the parts include: geometric dimensions of the parts and the laser cutting path; the parameters of the cut material include: constant pressure specific heat capacity that changes with temperature density thermal conductivity natural convection heat transfer coefficient surface emissivity thermal expansion coefficient elastic modulus yield strength plastic deformation constitutive parameters, material melting point and heat of fusion wherein: temperature; the environmental parameters include: ambient temperature clamping and fixing conditions of the cut part.
[0013] Step b) according to the cut material parameters in the laser cutting simulation input parameters, the cut part is given various temperature-dependent material properties.
[0014] Step c) apply the heat transfer boundary conditions: establish the surface Gaussian heat source model of laser cutting, and apply the heat source on the original surface of laser incidence, specifically: wherein: , is the heating point of the laser heat source, which is a function of time, and R is the laser focal point radius;
[0015] Step d) sequentially apply natural convection boundary conditions on each surface of the cut part, apply radiation heat dissipation conditions , and according to the clamping and fixing conditions of the cut part, apply the corresponding displacement and velocity boundary conditions, wherein: is the convective heat flux, is the radiation heat flux, is the Boltzmann constant, is the ambient temperature, is the natural convection heat transfer coefficient, is the surface emissivity.
[0016] Step e) input the material melting behavior description criterion in the model.
[0017] The time-stepping finite element solution specifically includes:
[0018] Step 1) at the initial time of laser cutting, define the field variable Is_melt for each grid element, and define its initial value as 0, indicating that the grid element has not been melted, and define the initial temperature of each grid element as the ambient temperature , and in the zero stress-strain state;
[0019] Step 2) For any The moment at which the calculation time step occurs First, according to Temperature field distribution in time steps , obtain the material performance parameters corresponding to the temperature at this time step;
[0020] Step 3) The material performance parameters corresponding to the temperature at the time step are the current material performance parameters. Combined with the heat transfer boundary conditions, the heat transfer equation is used to calculate the Temperature distribution in each time step ;
[0021] Step 4) For the number For each grid cell from 1 to N, determine whether it meets the material melting judgment condition. If so, modify the field variable Is_melt of the grid cell to 1. At the same time, apply the material melting behavior description criteria to the grid cell, including thermodynamics, heat transfer, and elastic-plastic mechanics change criteria, and modify the material properties and boundary conditions of the grid cell.
[0022] Step 5) According to the first Temperature distribution in each time step , based on the previously calculated The stress and strain field of the time step is taken as the initial value. Based on the material properties and boundary conditions modified in step 4, the stress and strain field of the time step is calculated according to the thermoelastic-plastic deformation equation. The stress and strain field of each time step;
[0023] Step 6) Repeat steps 2 to 5 until the calculation time step reaches the completion time of laser cutting, and finally obtain the accurate temperature distribution field and structural stress and strain field in the component during the laser cutting process. Technical Effects
[0024] This invention constructs material melting judgment conditions and a description of material melting behavior, embeds a thermomechanically coupled finite element simulation model for laser cutting by varying material properties and boundary conditions, and performs computational calculations using a time-stepping method. Compared to existing technologies, this invention accurately describes the laser heat source heating, material melting and heat dissipation, material removal during cutting, and the thermal elastic-plastic deformation of parts during the laser cutting process, effectively achieving high-precision simulation calculations for laser cutting. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 Flowchart of the present invention;
[0026] Figure 2 A schematic diagram of a workpiece being laser cut and the laser cutting process in an embodiment;
[0027] Figure 3 Material parameters of the laser-cut plate for the example;
[0028] In the figure: 1 is a thermodynamic performance parameter, 2 is a heat transfer performance parameter, 3 is a mechanical performance parameter, and 4 is a plastic deformation constitutive parameter;
[0029] Figure 4 The model meshing diagram used in the finite element simulation calculation of the example;
[0030] Figure 5 The time step finite element solution method flowchart used in the laser cutting thermal coupling simulation calculation of the example;
[0031] Figure 6 The component temperature field distribution cloud diagram at t = 30 s in the simulation calculation process of the example laser cutting;
[0032] Figure 7 The component residual stress field (Mises equivalent stress) distribution cloud diagram after cutting is completed;
[0033] Figure 8 The component deformation displacement field distribution cloud diagram after cutting is completed;
[0034] Figure 9 The side view of the component laser cutting kerf morphology after cutting is completed;
[0035] Figure 10 The up and down width comparison diagram of the laser cutting kerf obtained by simulation and test. DETAILED DESCRIPTION
[0036] As shown in Figure 1 , the laser cutting thermal coupling simulation method involved in the example includes:
[0037] Step 1, according to the actual laser cutting process, the laser cutting simulation input parameters are obtained, specifically including:
[0038] 1.1 The selected laser cutting power , focal radius , cutting speed , thermal efficiency ;
[0039] 1.2 As shown in Figure 2 , the part is initially a thin plate with a size of 150mm×150mm×6mm, and the laser cutting path is to cut it into two thin plates with a size of 150mm×75mm×6mm along the symmetry axis.
[0040] 1.3 The cut material is AH36 high-strength steel, and the material parameters include: specific heat capacity at constant pressure varying with temperature , density , thermal conductivity , natural convection heat transfer coefficient , surface emissivity , thermal expansion coefficient , elastic modulus , initial yield strength , plastic deformation constitutive parameter, material melting point not varying with temperature =1600℃, heat of fusion =218 kJ / kg, is the temperature.
[0041] As shown in Figure 3 , the plastic deformation constitutive parameter adopts the Hockett-Sherby model, specifically: , wherein: is the steady-state flow stress, is the saturation coefficient, is the saturation index, is the post-hardening yield strength, is the plastic strain.
[0042] 1.4 The ambient temperature during cutting is ℃, and the part is fixed in a three-point simply supported manner to suppress its rigid body motion.
[0043] Step 2, according to the material parameters of the cut material, determine the material melting judgment condition, for each three-dimensional grid element with dimensions of , , , the real-time temperature =1600℃, and the total heat absorption of the element ×218 kJ / kg.
[0044] Step 3, according to the material parameters of the cut material, determine the material melting behavior description criterion, specifically including:
[0045] 3.1 Let the grid element specific heat capacity at constant pressure =1e-5× =0.00559 , density =1e-5× =0.788 .
[0046] 3.2 Let the grid element natural convection heat transfer coefficient =6e-5 , surface emissivity =6e-6, the thermal conductivity is set as the orthogonal anisotropic thermal conductivity, and the thermal conductivity parallel to the laser incidence direction is set as 1e5 W / (m·K), and the thermal conductivity perpendicular to the laser incidence direction is set as 0 W / (m·K). =6e-6, the thermal conductivity is set as the orthogonal anisotropic thermal conductivity, and the thermal conductivity parallel to the laser incidence direction is set as 1e5 W / (m·K), and the thermal conductivity perpendicular to the laser incidence direction is set as 0 W / (m·K). 0 W / (m·K).
[0047] 3.3 The elastic modulus of the grid unit is set as 1e-5 =1e-5 =1.88 MPa.
[0048] Step 4, a laser cutting thermal-mechanical coupling finite element simulation model considering material melting is established, specifically including:
[0049] 4.1 A geometric model of the cut part is established in the simulation software and is divided into 14400 grid units as shown in the figure, and each grid unit is given a serial number 1, 2, 3, …, 14400; Figure 4
[0050] The division is based on the principle that the size of the grid unit located on the laser cutting path in any direction does not exceed the laser focal point radius =0.2mm.
[0051] 4.2 The parameters of the cut material in step 1.3 are input into the finite element simulation model.
[0052] 4.3 A surface Gaussian heat source model of laser cutting is established , and the heat source is applied to the original surface of laser incidence, wherein: 、 is the heating point of the laser heat source, which is a function of time; natural convection boundary conditions are applied on each surface of the cut part , and radiation heat dissipation conditions are applied on each surface of the cut part , wherein: is the convection heat flux, is the radiation heat flux, is the Boltzmann constant; 4.4 Three-point displacement boundary conditions are applied to suppress the rigid body motion of the part.
[0053] 4.5 The material melting behavior description criterion determined in step 3 is set in the finite element simulation model, and the trigger condition is that the material of the grid unit meets the material melting judgment condition.
[0054] Step 5, as shown in the figure
[0055] Figure 5 The finite element simulation model established in step 4 is solved by using a time-stepping finite element solving method, and specifically includes:
[0056] 5.1 Define the field variable Is_melt=0, and initialize the temperature field, stress and strain field;
[0057] 5.2 For the time at which the first time step after the initial time is located , first obtain the material property parameters corresponding to the temperature at the first time step from step 1.3 according to the temperature field distribution at the first time step, and use the material property parameters as the material property parameter values at the first time step;
[0058] 5.3 Calculate the temperature distribution at the first time step by using the heat transfer equation, and for the grid elements numbered 1~14400, judge whether they satisfy the material melting judgment condition in sequence, if so, modify the field variable is_melt of the grid element to 1, and at the same time, apply the material melting behavior description criterion set in step 4.5 to the grid element in sequence, modify the material properties and boundary conditions of the grid element;
[0059] 5.4 According to the temperature distribution at the first time step calculated in step 5.3, take the stress and strain field at the first time step calculated before as the initial value, and on the basis of the material properties and boundary conditions modified in step 5.3, calculate the stress and strain field at the first time step according to the thermal elastic-plastic deformation equation;
[0060] Repeat steps 5.2-5.4 until the calculation time step reaches the completion time of the laser cutting, and finally obtain the calculation results of the temperature field and stress and strain field during the whole process of laser cutting.
[0061] To verify the accuracy of the simulation model, a laser cutting test is carried out, and the same laser cutting parameters as those set in step 1.1 are used, i.e. laser cutting power , focal radius , cutting speed , a laser cutting test was conducted on a thin plate component of the same size and shape as in step 1.2. During the test, the three corner points of the thin plate component were clamped and fixed using the same clamping method as in step 1.4, and actual laser cutting was carried out. Before cutting, a square grid with a size of 5mm×5mm was printed on the surface of the thin plate to facilitate deformation measurement after cutting. During the cutting process, the temperature of the plate was monitored by an infrared temperature sensor. After cutting, the slit width data of the top and bottom surfaces at the grid points were first measured in sequence along the length of the slit. The measurement sampling interval for the starting and ending sections of the cutting was 2mm, and the measurement sampling interval for the remaining areas was 5mm. The component was then placed on a flat surface and its concave and convex deformation was tested using a height gauge.
[0062] like Figure 6 As shown, the cutting process =10s. The maximum simulated temperature in the figure is 1620°C, which is consistent with the melting point of the material and the maximum temperature of 1632°C measured in the sample. Simultaneously, the simulated heat input is concentrated in the incision area and penetrates through the thickness of the plate, demonstrating that the laser cutting simulation method proposed in this invention can accurately describe the physical mechanism of laser heat source heating and material melting and heat dissipation during the laser cutting process. The heat generated by the laser irradiation is completely applied through the melted units to the unmelted units below, resulting in a highly reasonable and accurate temperature field.
[0063] like Figure 7 When cutting is completed =30s Mises equivalent stress field calculation results, the slit area in the figure does not participate in the elastic-plastic mechanics calculation, and the high stress area is located on both sides of the laser cutting slit, which is consistent with the actual situation, indicating that the stress distribution after laser cutting calculated by the present invention is relatively reasonable.
[0064] like Figure 8 When cutting is completed = 30s displacement field calculation results show that the maximum deformation of the plate is 0.187mm, which is relatively small and consistent with the experimentally measured maximum protrusion of 0.17mm at the end of the cut. The deformation at the starting point of laser cutting is lower than the deformation near the end point, which is consistent with the actual characteristics of laser cutting: the starting point of the cut is smaller, resulting in greater rigidity, while the end point of the cut is larger, resulting in weaker rigidity. This shows that the deformation of the part after laser cutting calculated by this method is highly reasonable and accurate.
[0065] like Figure 9As shown in FIG, this is a side view of the laser incision morphology obtained by cutting. The results show that the laser incision has the characteristics of being wide at the top and narrow at the bottom, that is, more material is removed from the upper surface due to direct laser irradiation and higher temperature, while the lower surface has less material removal because the upper material needs to be removed before it can be irradiated by the laser. This is in line with the actual situation of laser cutting, indicating that the laser incision width calculated by the present invention is reasonable.
[0066] like Figure 10 As shown in the figure, it is a comparison diagram of the laser cutting incision width obtained by simulation and the laser cutting incision width obtained by experiment. The laser cutting incision width data extracted from the simulation in the figure is consistent with the upper and lower width patterns of the incision at each measuring point measured in the experiment, and the values are close. They all reflect the process characteristics of a smaller incision at the starting point of cutting, a larger incision at the end point, and a wider incision at the top and narrower at the bottom as a whole, indicating that the part incision width calculated by the present invention has high accuracy.
[0067] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.
Claims
1. A laser cutting thermal-mechanical coupling simulation method, characterized in that: By constructing a thermal-mechanical coupled finite element simulation model for laser cutting that includes material melting judgment conditions and material melting behavior description criteria, the precise temperature distribution field and structural stress and strain field in the component during laser cutting are obtained through time-stepping finite element solution. The material melting judgment condition is: for each three-dimensional dimension in the finite element simulation 、 、 The grid cell, its real-time temperature Reach melting point And the total heat absorption of the unit satisfy ,in: is the heat of fusion; The material melting behavior description criteria refer to: for mesh units that meet the material melting judgment conditions in finite element simulation, the unit material properties or boundary condition settings used to reflect their melting behavior in the simulation, including: thermodynamic description criteria, heat transfer description criteria and elastic-plastic mechanics description criteria.
2. The laser cutting thermal-mechanical coupling simulation method according to claim 1, characterized in that: The thermodynamic description criterion is: the specific heat capacity of the grid unit at constant pressure =1e-5× ,density =1e-5× , indicating that the grid cell no longer stores heat; The heat transfer description criterion is: the natural convection heat transfer coefficient of the grid unit =1e-5× , surface emissivity =1e-5× , the thermal conductivity is set to orthotropic thermal conductivity, and the thermal conductivity parallel to the laser incident direction is set to =1e5 W / (m·K), thermal conductivity perpendicular to the laser incident direction 0 W / (m·K), indicating that the grid unit no longer freely exchanges heat with the outside, and all the heat generated by laser irradiation is applied through the unit to the unmelted units below; The elastic-plastic mechanics description criterion is: the elastic modulus of the grid unit = 1e-5× , indicating that the surrounding unmelted elements are no longer subject to the loads and constraints of this element.
3. The laser cutting thermal-mechanical coupling simulation method according to claim 1, characterized in that: The laser cutting thermal-mechanical coupling finite element simulation model is constructed in the following way: Step a) Based on the part geometric parameters in the laser cutting simulation input parameters, a geometric model of the cut part is established, and mesh units are divided for finite element calculation, and each mesh unit is assigned a serial number 1, 2, 3, ..., N, where N is the total number of mesh units, and the size of the mesh unit located on the laser cutting path in any direction does not exceed the laser focus radius ; The laser cutting simulation input parameters include: laser heat input parameters, part geometry parameters, cutting material parameters and environmental parameters; Step b) assigning various temperature-dependent material properties to the cut part according to the cut material parameters in the laser cutting simulation input parameters; Step c) applying heat transfer boundary conditions: establishing a Gaussian heat source model for the laser-cut surface and applying the heat source to the original surface where the laser is incident, specifically: ,in: 、 For the moment The heating point of the laser heat source is a function of time, and R is the laser focus radius; Step d) Applying natural convection boundary conditions on each surface of the cut part in turn , applying radiation heat dissipation conditions on each surface of the cut part , and then apply corresponding displacement and velocity boundary conditions according to the clamping and fixing conditions of the cut parts, where: is the convective heat flux, is the radiation heat flux, is the Boltzmann constant, is the ambient temperature, is the natural convection heat transfer coefficient, is the surface emissivity; Step e) inputting the material melting behavior description criteria into the model.
4. The laser cutting thermal-mechanical coupling simulation method according to claim 3, characterized in that: The laser heat input parameters include: cutting laser power , focal radius , cutting speed and thermal efficiency The geometric parameters of the parts include: geometric dimensions of the parts and the laser cutting path; the parameters of the cut material include: constant pressure specific heat capacity that changes with temperature ,density , thermal conductivity , natural convection heat transfer coefficient , surface emissivity , thermal expansion coefficient , elastic modulus , yield strength , plastic deformation constitutive parameters, material melting point and heat of fusion ,in: The environmental parameters include: ambient temperature , the clamping and fixing conditions of the cut parts.
5. The laser cutting thermal-mechanical coupling simulation method according to claim 1, characterized in that: The time-stepping finite element solution specifically includes: Step 1) At the initial moment of laser cutting, define the field variable Is_melt for each grid cell and define its initial value as 0, indicating that the grid cell has not melted yet, and define the initial temperature of each grid cell as the ambient temperature , and is in a state of zero stress and strain; Step 2) For any The moment at which the calculation time step occurs First, according to Temperature field distribution in each time step , obtain the material performance parameters corresponding to the temperature at this time step; Step 3) The material performance parameters corresponding to the temperature at the time step are the current material performance parameters. Combined with the heat transfer boundary conditions, the heat transfer equation is used to calculate the Temperature distribution in each time step ; Step 4) For the number For each grid cell from 1 to N, determine whether it meets the material melting judgment condition. If so, modify the field variable Is_melt of the grid cell to 1. At the same time, apply the material melting behavior description criteria to the grid cell, including thermodynamics, heat transfer, and elastic-plastic mechanics change criteria, and modify the material properties and boundary conditions of the grid cell. Step 5) According to the first Temperature distribution in each time step , based on the previously calculated The stress and strain field of the time step is taken as the initial value. Based on the material properties and boundary conditions modified in step 4, the stress and strain field of the time step is calculated according to the thermoelastic-plastic deformation equation. The stress and strain field of each time step; Step 6) Repeat steps 2 to 5 until the calculation time step reaches the completion time of laser cutting, and finally obtain the accurate temperature distribution field and structural stress and strain field in the component during the laser cutting process.