A method for predicting welding temperature field and deformation of T-shaped sheet part corner joint welding

Abstract

The application discloses a kind of T-shaped sheet piece angle joint welding's welding temperature field and deformation prediction method, it is related to welding temperature field and deformation simulation prediction technical field, method steps include obtaining T-shaped sheet piece angle joint welding's temperature field theoretical solution;T-shaped sheet piece grid division and heat source setting are carried out;Solving the temperature field of T-shaped sheet piece angle joint welding, and comparing and analyzing iterative finite element analysis setting with the temperature field theoretical solution obtained;Obtain the welding deformation and stress field of T-shaped sheet piece.The application solves the temperature field of T-shaped sheet piece angle joint welding by using finite element analysis method, and compares and analyzes iterative finite element analysis setting with the temperature field theoretical solution, improve the precision of finite element solution.

Description

Technical Field

[0001] This invention belongs to the field of welding temperature field and deformation simulation prediction technology, and in particular relates to a method for predicting the welding temperature field and deformation of T-shaped thin plate fillet welds. Background Technology

[0002] In recent years, industrial robots have been widely used in welding. However, their operation mainly relies on online teaching, resulting in low levels of intelligence and insufficient adaptability and fault tolerance to meet actual operational needs. This problem is particularly pronounced when welding thin plates using robots. First, thin plates have small pre-reserved gaps, requiring high welding precision and quality. Errors during workpiece processing and assembly can cause changes in the position and size of these gaps. Second, during welding, the stress and deformation caused by localized heating in thin plates are more significant compared to larger workpieces. Actively controlling welding deformation is a bottleneck in automated welding technology for thin plates. Exploring the deformation mechanism during welding heat transfer and establishing a welding deformation prediction model are key to overcoming these bottlenecks.

[0003] Currently, the main method for predicting the welding process of T-shaped thin plates is a combination of numerical simulation and experimentation. However, the experimental method is not only cumbersome, but also costly due to the large welding deformation of thin plates, which greatly affects the efficiency of simulation prediction. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by providing a method for predicting the welding temperature field and deformation of fillet welds on T-shaped thin plates.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for predicting the welding temperature field and deformation of fillet welds on T-shaped thin plates includes the following steps:

[0007] Step S1: Obtain the theoretical solution of the temperature field for the fillet weld of the T-shaped thin plate;

[0008] Step S2: Perform mesh generation and heat source setting for the T-shaped thin plate;

[0009] Step S3: Solve the temperature field of the fillet weld of the T-shaped thin plate, record the temperature history curve of specific points and compare it with the theoretical solution of the temperature field, and then improve the finite element analysis settings (boundary conditions, analysis time step, heat source model, etc.) to improve the accuracy of the finite element solution; among them, points within 10-20cm around the weld can be used as specific points, but the temperature curves of some points are more accurate or easier to compare. Therefore, the temperature curves of points in the heat-affected zone of the weld are selected for comparison.

[0010] Step S4: Based on the high-precision temperature field results, the stress field of the T-shaped thin plate during the welding process is obtained using the thermo-elastic-plastic method, and then the deformation result of the final thin plate is obtained.

[0011] Based on the above technical solution, further, the process of obtaining the theoretical solution in step S1 includes the following steps:

[0012] Step S11: The temperature field of the fillet weld of the T-shaped thin plate is theoretically derived based on the law of heat conduction, and assumptions are made about the base material and heat source parameters before the derivation.

[0013] Step S12: Combine the law of conservation of energy with Fourier's law to derive the differential equation of heat conduction in Cartesian coordinates;

[0014] Step S13: Combine the differential equation of heat conduction with the initial condition T0 of the base temperature field to obtain the instantaneous point heat source welding temperature field;

[0015] Step S14: Superimpose the instantaneous point heat source welding temperature field obtained in step S13 in the weld direction in the time domain to obtain the theoretical solution of the temperature field for single-pass continuous welding.

[0016] Based on the above technical solution, further, the collective material and heat source parameters assumed in step S11 include:

[0017] 1. The shape of the substrate is idealized as a 90° angle weld between two infinitely large flat plates;

[0018] 2. The material's thermophysical properties are isotropic, and the parameters do not change with temperature;

[0019] 3. The base material does not undergo a phase transformation during the welding process;

[0020] 4. The shape of the heat source model does not change when it moves on the substrate;

[0021] 5. Neglecting convective and radiative heat transfer between the substrate and the surrounding environment, the substrate is placed in an adiabatic state.

[0022] Based on the above technical solution, the differential equation for heat conduction in step S12 is further as follows:

[0023]

[0024] In the formula, ρ represents the instantaneous temperature change at a given location in the coordinate system; ρ represents the density of the matrix material, in kg / m³. 3 ; c represents the specific heat capacity of the matrix material, in J / (kg·℃); λ represents the thermal conductivity of the matrix, in W / (m·℃).

[0025] Based on the above technical solution, further, the formula for the welding temperature field of the heat source in step S13 is:

[0026]

[0027] In the formula, the initial conditions of the substrate temperature field are assumed to be:

[0028] T(x,y,z,t=0)=T0(x,y,z), Thermal diffusivity, in meters (m). 2 / s.

[0029] Based on the above technical solution, further, in step S2, the Ansys transient thermal analysis module is used for mesh generation and heat source setting, including the following steps:

[0030] Step S21: Create a T-shaped thin plate fillet weld model in Solidworks;

[0031] Step S22: Mesh the model from step S21 in Ansys-workbench;

[0032] Step S23: Use the function editor in Ansys to set the parameters of the moving heat source.

[0033] Based on the above technical solution, further, step S3 includes the following steps:

[0034] Step S31: Set the ambient temperature, heat convection conditions, matrix material properties, and temperature in Ansys-workbench;

[0035] Step S32: In the Ansys-workbench transient thermal analysis module, set up analysis steps for the welding stage and the cooling stage respectively, and use the finite element method to calculate the temperature field of the substrate during welding and cooling.

[0036] Step S33: Based on the finite element solution of the temperature field obtained in step S32, derive the temperature probe data at a given location during the welding-cooling process, and perform error analysis on the temperature data curve at the same location in Matlab.

[0037] Based on the above technical solution, further, step S4 includes the following steps:

[0038] Step S41: Import the temperature field results obtained in step S33 into the transient structure analysis module in Ansys-workbench, and use its mesh model and analysis step settings.

[0039] Step S42: Set the force and displacement boundary conditions, as well as the loading method and values, in Ansys-workbench;

[0040] Step S43: Based on the high-precision temperature field results, the stress field of the T-shaped thin plate during the welding process is obtained in Ansys-workbench using the thermo-elastic-plastic method, and then the deformation result of the final thin plate is obtained.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention solves the temperature field of a fillet weld on a T-shaped thin plate using the finite element method. It obtains the stress field of the T-shaped thin plate during welding using the thermo-elastic-plastic method, thereby predicting the deformation of the thin plate. Furthermore, it derives the theoretical solution of the temperature field during the welding process of the T-shaped thin plate using analytical methods, improving the finite element analysis process and increasing the accuracy of welding deformation prediction. Simultaneously, this method, combining theoretical solutions with the finite element method, significantly improves the efficiency of welding deformation prediction while maintaining low analysis costs, providing a new approach to tracking weld deformation during automated welding. Attached Figure Description

[0043] Figure 1 This is a schematic diagram illustrating the theoretical derivation of the numerical solution for the fillet weld temperature field of the T-shaped thin plate component described in this invention.

[0044] Figure 2 This is a schematic diagram of the double ellipsoidal heat source model described in this invention;

[0045] Figure 3 This is a schematic diagram of the fillet weld model of the T-shaped thin plate part described in this invention;

[0046] Figure 4 This is a schematic diagram of the T-shaped thin plate corner weld mesh model described in this invention;

[0047] Figure 5 This is a schematic diagram of the cooling temperature field at the end of the fillet weld of a single-pass T-shaped thin plate as described in this invention.

[0048] Figure 6 This is a schematic diagram comparing the theoretical solution and the finite element solution for the given point temperature of the single-pass T-shaped thin plate fillet weld described in this invention. Detailed Implementation

[0049] To make the objectives and technical solutions of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments.

[0050] Example 1

[0051] Combination Figure 1A method for predicting the welding temperature field and deformation of fillet welds on T-shaped thin plates includes the following steps:

[0052] Step S1: Obtain the theoretical solution of the temperature field for the fillet weld of the T-shaped thin plate;

[0053] Specifically, step S11: The temperature field of the T-shaped thin plate fillet weld is theoretically derived based on the law of heat conduction. Before the derivation, assumptions are made regarding the base material and heat source parameters. These assumptions may include: the base material's shape is idealized as a 90° corner weld between two infinitely large plates; the material's thermophysical properties are isotropic and their parameters do not change with temperature; the base material does not undergo a phase change during welding; the heat source model's shape does not change as it moves across the base material; and convective and radiative heat transfer between the base material and its surroundings is ignored, ensuring the base material is in an adiabatic state. Because the base material is Q235 steel, its thermal conductivity is much higher than that of air, and the influence of heat conduction on the base material's temperature field during welding is much greater than that of heat convection and radiation. Therefore, the welding process can be simplified to an adiabatic corner weld between two infinitely large plates.

[0054] Step S12: Combine the law of conservation of energy with Fourier's law to derive the differential equation of heat conduction in Cartesian coordinates;

[0055] Specifically, Fourier's law states that in the process of heat conduction, the amount of heat passing through a given cross-section per unit time is directly proportional to the rate of temperature change perpendicular to that cross-section and the cross-sectional area, that is:

[0056] In the formula, λ represents the thermal conductivity of the matrix, with units of W / (m·℃), and the negative sign in the formula indicates that energy is transferred along the direction of decreasing temperature.

[0057] Therefore, the differential equation for heat conduction can be obtained as follows: In the formula, ρ represents the instantaneous temperature change at a given location in the coordinate system; ρ represents the density of the matrix material, in kg / m³. 3 ; c represents the specific heat capacity of the matrix material, in units of J / (kg·℃); λ also represents the thermal conductivity coefficient of the matrix, in units of W / (m·℃).

[0058] Step S13: Combine the differential equation of heat conduction with the initial condition T0 of the base temperature field to obtain the instantaneous point heat source welding temperature field;

[0059] Specifically, let the initial conditions of the matrix temperature field be:

[0060] T(x,y,z,t=0)=T0(x,y,z), Thermal diffusivity, in meters (m).2 / s.

[0061] The formula for obtaining the welding temperature field of the heat source is:

[0062]

[0063] Step S14: Superimpose the instantaneous point heat source welding temperature field obtained in step S13 in the weld direction in the time domain to obtain the theoretical solution of the temperature field for single-pass continuous welding.

[0064] Specifically, by Figure 3 The image shows the position of the weld seam where it contacts the flange on the web. A right-angled system (X, Y, Z) is established at the starting point of the base weld. The OX axis is along the direction of heat source movement, OY is along the web direction, and OZ is along the flange direction. The length of the weld seam along the OX direction is l (m), and the speed of the heat source movement is v (m / s). Let there exist a time infinitesimal element dt′, with an initial time t′ and an ending time t (t>t′≥0). The temperature increment dT produced by the point heat source at point (x0, y0, z0) during the time interval dt′ is:

[0065] Formula 1:

[0066] Integrating Equation 1 over the time domain from the initial time to the welding end time t, we obtain the temperature field during the fillet welding process of the T-shaped thin plate:

[0067]

[0068] The weld cooling process after welding can be simulated by introducing a negative heat source with the same energy as the original heat source, and its movement speed is the same. Therefore, the temperature field for the cooling process after welding can be obtained as follows:

[0069]

[0070] In summary, the instantaneous point heat source welding temperature field is obtained as follows:

[0071]

[0072] Taking the double ellipsoidal heat source model as an example, it is known that since its inception in the 1980s, the double ellipsoidal heat source model has become the mainstream heat source model used in welding simulation research. Compared with Gaussian heat sources and spherical heat source models, it can more accurately simulate the changes in the shape of the heat source during its movement. Most other heat source models are based on these models but with optimizations to the three-dimensional shape of the heat source. Therefore, the welding temperature field obtained using the double ellipsoidal model is more accurate than that obtained using a point heat source. The double ellipsoidal heat source model can be divided into two parts along the direction of heat source movement: a steeper section at the beginning and a gentler section at the end. Both parts are roughly 1 / 4 ellipsoidal. A schematic diagram of the double ellipsoidal heat source model is shown below. Figure 2 As shown, its heat flux density distribution is given by Formula 2:

[0073]

[0074] In the formula, a′, b′, c f c r All are heat source shape parameters, with units of meters (m); Q represents the heat source input power, with units of watts (W).

[0075] f f f r All are represented as thermal input parameters, and f f +f r =2.

[0076] The double ellipsoidal heat source can be considered as an infinite number of point heat source elements ds = dxdydz, whose thermal power is dQ = q(x,y,z)dxdydzdt. Substituting dQ into the formula for the welding temperature field of the heat source in step S13, we get Formula 3:

[0077]

[0078] In the formula, R 2 =(x0-x) 2 +(y0-y) 2 +(z0-z) 2 .

[0079] Combining formulas two and three, we obtain formula four as follows:

[0080]

[0081] Formula 4 reveals the instantaneous temperature change of each point within the double ellipsoidal heat source micro-element. Given in step S11, the instantaneous temperature field at a given point (x0, y0, z0) under the influence of the double ellipsoidal heat source can be obtained using the principle of spatial superposition, as shown in Formula 5 below:

[0082]

[0083]

[0084]

[0085] Equation 5 can be simplified using the substitution method to obtain:

[0086]

[0087] Similar to the superposition method in the time domain of the point heat source in step S14, the temperature increment dT generated by the double ellipsoidal heat source in the base coordinate system (X,Y,Z) at point (x0,y0,z0) during time dt′ is expressed by the following formula:

[0088]

[0089] Integrating Formula 6 over the time interval [0, t] yields Formula 7 as follows:

[0090]

[0091] Formula 7 represents the temperature field during the single-pass welding stage with a double ellipsoidal heat source. Solving for the temperature field during the cooling stage is done using the same method as in step S14, i.e., applying the same negative heat source.

[0092]

[0093]

[0094]

[0095]

[0096]

[0097]

[0098] In summary, the temperature field for welding with a single-channel double ellipsoidal heat source is solved as follows:

[0099]

[0100] Step S2: Perform mesh generation and heat source setting for the T-shaped thin plate;

[0101] The specific process includes the following steps:

[0102] Step S21: Create a T-shaped thin plate fillet weld model in Solidworks; for example... Figure 3 As shown, its dimensions are: web 200*80*1mm, wing 200*80*10mm;

[0103] Step S22: Mesh the model from Step S21 in Ansys-workbench. The overall mesh model is generated using a hexahedral mesh model, such as... Figure 4 As shown, the specific dimensions of the T-shaped thin plate fillet weld mesh model are adjusted as follows: 0.7mm mesh near the weld end of the flange; 7mm mesh far from the weld end of the flange; 0.5mm mesh near the weld end of the web; and 5mm mesh far from the weld end of the web. In the thickness direction, the flange mesh is 2mm and the web mesh is 0.5mm.

[0104] Step S23: In Ansys, use the function editor to set the parameters of the moving heat source. This method uses a Gaussian heat source model to simulate the welding heat source, and its heat source distribution function is as follows:

[0105]

[0106] In the formula, η represents the heat source efficiency; Q1 represents the heat source power in W; and R represents the effective heat source radius in m.

[0107] The APDL code for the heat source model can be automatically generated in the function editor. Importing it into Ansys-workbench will then simulate the movement of the heat source during the welding process.

[0108] Step S3: Solve the temperature field of the fillet weld of the T-shaped thin plate, record the temperature history curve of specific points and compare it with the theoretical solution of the temperature field to obtain new finite element analysis settings. Among them, points within 10-20cm around the weld can be used as specific points. However, the temperature curves of some points are more accurate or easier to compare. Therefore, the temperature curves of points in the heat-affected zone of the weld are selected for comparison.

[0109] The specific process includes the following steps:

[0110] Step S31: Set the ambient temperature, heat convection conditions, matrix material properties, and temperature in Ansys-workbench;

[0111] Step S32: In the Ansys-workbench transient thermal analysis module, set up analysis steps for the welding and cooling stages respectively, and use the finite element method to calculate the temperature field of the substrate during welding and cooling; the schematic diagram of the temperature field at the end of cooling of a single-pass T-shaped thin plate fillet weld is shown below. Figure 5As shown. At the end of welding, the highest workpiece temperature reached 5262.9℃, higher than the actual laser heat source temperature, located at the end of the weld near the web. Analysis showed that this location was the center of the heat source, and the front part of the weld had a preheating effect on the rear part, reducing heat dissipation from the rear part, hence the higher temperature at this location. At the end of the cooling phase, the highest temperature dropped to 284.54℃, located at the end of the web, about 30mm from the weld. There are several reasons for the phenomenon that the highest temperature point is far away from the weld. The main reason is that the flange thickness is greater than the web, and the heat flow is fastest in the flange direction, causing the highest temperature point to move away from the flange. Other reasons include the preheating of the front and rear welds and spatial heat convection.

[0112] Step S33: Based on the finite element solution of the temperature field obtained in step S32, derive the temperature probe data at the given position during the welding to cooling process. Perform error analysis on the temperature data curve at the same position in Matlab, comparing it with the analytical solution. Based on the error analysis results, adjust the parameters of the Gaussian heat source, such as heat source radius, heat source efficiency, and heat source power, and reduce the mesh size of the mesh model until the overall error between the temperature field simulation result and the theoretical solution of the temperature field obtained in step S14 does not exceed 10%. Determine the peak temperature distribution of the melting zone, over-aging zone, and heat-affected zone in the joint. That is, determine that the peak temperature distribution of the theoretical solution and the finite element solution are basically consistent, thus confirming that the accuracy of the finite element solution is sufficient. A schematic diagram comparing the theoretical solution and the finite element solution for the given point temperature of a single-pass T-shaped thin plate fillet weld is shown below. Figure 6 As shown.

[0113] Step S4: Obtain the welding deformation and stress field of the T-shaped thin plate.

[0114] The specific process includes the following steps:

[0115] Step S41: Import the temperature field results obtained in step S33 into the transient structure analysis module in Ansys-workbench, and use its mesh model and analysis step settings.

[0116] Step S42: Set the force and displacement boundary conditions, as well as the loading method and values, in Ansys-workbench;

[0117] Step S43: Use the thermo-elastic-plastic method in Ansys-workbench to calculate the stress field, total strain, and deformation of the T-shaped thin plate fillet welding process.

[0118] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for predicting the welding temperature field and deformation of fillet welds on T-shaped thin plates, characterized in that, Includes the following steps: Step S1: Obtain the theoretical solution of the temperature field for the fillet weld of the T-shaped thin plate; Step S1, which involves obtaining the theoretical solution, includes the following steps: Step S11: The temperature field of the fillet weld of the T-shaped thin plate is theoretically derived based on the law of heat conduction. Before the derivation, assumptions are made about the base material and heat source parameters of the T-shaped thin plate. Step S12: Combine the law of conservation of energy with Fourier's law to derive the differential equation of heat conduction in Cartesian coordinates; Step S13: Solve the simultaneous differential equation of heat conduction and the assumed initial temperature field condition T0 to obtain the instantaneous point heat source welding temperature field; Step S14: Superimpose the instantaneous point heat source welding temperature field obtained in step S13 in the weld direction in the time domain to obtain the theoretical solution of the temperature field for single-pass continuous welding. The matrix material and heat source parameters assumed in step S11 include: (1) The shape of the substrate is idealized as a 90° angle weld between two infinitely large flat plates; (2) The thermophysical properties of the material are isotropic and the parameters do not change with temperature; (3) The base material does not undergo a phase transformation during the welding process; (4) The shape of the heat source model does not change when it moves on the substrate; (5) Ignore the convective and radiative heat transfer between the substrate and the surrounding environment, so that the substrate is in an adiabatic state. The differential equation for heat conduction in step S12 is: In the formula, This represents the instantaneous temperature change at a given location in the coordinate system; The density of the matrix material is expressed in kg / m³. 3 ; Expressed as the specific heat capacity of the matrix material, with units of J / (kg·℃); It is expressed as the thermal conductivity coefficient of the matrix, with units of W / (m·℃); The formula for the welding temperature field of the heat source in step S13 is: ； In the formula, the initial conditions of the substrate temperature field are assumed to be: , is the thermal diffusivity with the unit of m 2 / s; represents the heat source input power with the unit of W; Step S2: Perform mesh generation and heat source setting for the T-shaped thin plate; Step S3: Solve the temperature field of the fillet weld of the T-shaped thin plate, record the temperature history curves of some points around the weld and compare them with the theoretical solution of the temperature field to obtain new finite element analysis settings parameters; Step S4: Based on the high-precision temperature field results, the stress field of the T-shaped thin plate during the welding process is obtained using the thermo-elastic-plastic method, and then the deformation result of the final thin plate is obtained.

2. The method of predicting a welding temperature field and deformation of a T-shaped sheet member corner joint according to claim 1, characterized by, In step S2, the Ansys transient thermal analysis module is used to perform mesh generation and heat source setting, including the following steps: Step S21: Create a T-shaped thin plate fillet weld model in Solidworks; Step S22: Mesh the model from step S21 in Ansys-workbench; Step S23: Use the function editor in Ansys to set the parameters of the moving heat source.

3. The method of claim 1, wherein the T-shaped sheet member is a T-shaped sheet member having a thickness of 1.5 mm or less. Step S3 includes the following steps: Step S31: Set the ambient temperature, heat convection conditions, matrix material properties, and temperature in Ansys-workbench; Step S32: In the Ansys-workbench transient thermal analysis module, set up analysis steps for the welding stage and the cooling stage respectively, and use the finite element method to calculate the temperature field of the substrate during welding and cooling. Step S33: Based on the finite element solution of the temperature field obtained in step S32, derive the temperature probe data at a given position during the welding to cooling process, and perform error analysis on the temperature data curve at the same position in Matlab.

4. The method according to claim 3, wherein Step S4 includes the following steps: Step S41: Import the temperature field results obtained in step S33 into the transient structure analysis module in Ansys-workbench, and use its mesh model and analysis step settings. Step S42: Set the force and displacement boundary conditions, as well as the loading method and values, in Ansys-workbench; Step S43: Based on the high-precision temperature field results, the stress field of the T-shaped thin plate during the welding process is obtained in Ansys-workbench using the thermo-elastic-plastic method, and then the deformation result of the final thin plate is obtained.

5. The method of predicting the welding temperature field and deformation of a T-shaped sheet member corner joint according to claim 4, characterized by, In step S33, based on the error analysis results, the parameters of the Gaussian heat source and the mesh size of the mesh model are adjusted until the overall error between the temperature field simulation results and the theoretical solution of the temperature field obtained in step S14 does not exceed 10%, and the comparison between the peak temperature distribution of the theoretical solution and the finite element solution is determined.

6. The method for predicting the welding temperature field and deformation of a T-shaped thin plate fillet weld according to claim 1, characterized in that, The finite element analysis settings in step S3 include at least boundary conditions, analysis time step, and heat source model.

Images