Efficient analytical algorithm for welding temperature field

Abstract

The invention discloses an efficient analytical algorithm for a welding temperature field, which is characterized by comprising the following steps of: S1, establishing a local geometric three-dimensional model of a welding seam; s2, a fusion welding heat source model of volume / area distribution heat flow is loaded; s3, obtaining a first evolution result of temperature field distribution; s4, the node temperature of the model is defined by analyzing the function of the heat source temperature field to solve the temperature field, and a second evolution result of temperature field distribution is obtained; s5, correcting the temperature gradient of the analytic temperature field; s6, temperature field solving is carried out according to boundary conditions of the function definition model node temperature for correcting and analyzing the heat source temperature field, and a third evolution result of temperature field distribution is obtained; s7, increasing the size of the grid, and repeating the step S6 to obtain a fourth evolution result of the temperature field distribution; s8, efficiently solving the welding temperature field by using the function definition model for correcting and analyzing the heat source temperature field; according to the scheme, the welding temperature field can be efficiently solved, and the calculation efficiency is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of welding temperature field analysis, and in particular to an efficient analysis algorithm for welding temperature field. Background Art

[0002] At present, there are mainly the following methods for solving the finite element temperature field of fusion welding:

[0003] 1. Transient heat transfer solution of mobile distributed heat source: In arc welding heat source, spatially distributed volume / area heat source is often used to solve the welding temperature field results, such as double ellipsoid volume heat source, Gaussian volume distribution heat source, Gaussian area distribution heat source, etc. By applying spatially distributed heat source, combined with the geometric model, initial temperature conditions, convection radiation heat transfer boundary conditions, etc. of the model set in the calculation software, ideal temperature field calculation results can usually be obtained, which are in good consistency with the actual temperature field test results.

[0004] However, when using spatially distributed heat sources to solve the welding temperature field, in order to ensure the mesh convergence of the calculation results, sufficient mesh density is required in the welding area. Usually, the mesh size needs to be less than 2mm and the number of meshes in the weld pool range needs to be greater than 12. Only in this way can the heat flux integral calculation requirements of nonlinear spatially distributed heat sources be met when solving transient heat transfer. Although this method has high accuracy in solving the welding temperature field, it is relatively expensive. Especially for the temperature field of large welded structures, the small mesh size and high nonlinear solution cost in transient heat transfer bring great difficulties to the temperature field solution. The mesh size is too large, the calculation solution cost increases, and it takes too long.

[0005] 2. Analytical temperature field solution method: usually used for ideal models of welding structures with simple geometric shapes (such as semi-infinite bodies, infinitely large thin plates, etc.), such as Figure 1 As shown in the figure, the solution formula for the analytical temperature field of a semi-infinite instantaneous point heat source moving along a straight line is as follows:

[0006]

[0007] Among them, q is, λ is the thermal conductivity of the material, a is the thermal diffusion coefficient of the material, v is the moving speed of the heat source, r is the distance from the current observation point to the center of the heat source, and x is the horizontal distance from the current observation point to the center of the heat source.

[0008] Since material nonlinearity and structural nonlinearity are ignored, and the model nodes are assigned boundaries by analyzing the temperature field, the calculation rate is significantly improved without solving the thermal differential equations of transient heat transfer of large equations. In addition, since the weld mesh density is not increased to solve the integral of the distributed heat flux, the mesh scale of the model can be further reduced, and the calculation cost is significantly reduced. This method has good application value in the temperature field calculation of large welded structures.

[0009] However, due to the simplification of the thermophysical properties of the material in the analytical calculation (the thermophysical properties that change nonlinearly with temperature are simplified to constants that do not change with temperature), and the neglect of the model's geometric size (the model is considered to be infinite), and the neglect of the convection and radiation exchange between the model and the surrounding air and other fluid media, there is a large deviation between the temperature field solved analytically and the actual temperature field distribution, and the solution results using spatially distributed volume / area heat sources. Summary of the invention

[0010] In view of the above-mentioned deficiencies in the prior art, the present invention provides an efficient analysis algorithm for the welding temperature field. Based on the moving point analysis of the heat source temperature field, the analysis temperature is corrected to obtain a high-precision temperature field result solution to solve the technical problems mentioned in the above background technology.

[0011] To achieve the above purpose, the technical solution adopted by the present invention is:

[0012] An efficient analysis algorithm for welding temperature field is provided, which is characterized by comprising the following steps:

[0013] S1: Establish a local geometric 3D model of the weld and input the material’s thermal physical properties parameters that vary with temperature;

[0014] S2: Melting welding heat source model with loading volume / area distribution heat flux;

[0015] S3: Calculate and solve the transient heat transfer temperature and obtain the first evolution result of the temperature field distribution;

[0016] S4: On the same local geometric three-dimensional model, only the temperature boundary conditions are loaded, and the model node temperatures are defined by the function of analyzing the heat source temperature field to solve the temperature field, and the second evolution result of the temperature field distribution is obtained;

[0017] S5: deriving the temperature distribution results of the first evolution result and the second evolution result of the temperature field respectively, and outputting the temperature distribution in the x direction, y direction and z direction respectively with the heat source of the quasi-steady-state temperature field as the center, and then correcting the temperature gradient in the x direction, y direction and z direction of the analytical temperature field respectively, wherein the x direction is the welding movement direction, the y direction is the heat source width direction, and the z direction is the heat source depth direction;

[0018] S6: On the same local geometric three-dimensional model, the boundary conditions of the model node temperature are defined by the function of the modified analytical heat source temperature field to solve the temperature field, and the third evolution result of the temperature field distribution is obtained;

[0019] S7: increasing the grid size and repeating step S6 to obtain the fourth evolution result of the temperature field distribution, and making the temperature gradient of the modified analytical heat source temperature field and the volume / area distribution heat source calculation result consistent;

[0020] S8: Apply the function definition model of the modified analytical heat source temperature field to efficiently solve the welding temperature field.

[0021] Furthermore, the thermophysical performance parameters in step S1 include density, thermal conductivity and specific heat capacity.

[0022] Furthermore, step S2 includes setting the initial temperature of the melting welding heat source model, the ambient temperature, and the convection radiation boundary conditions with the surrounding environment.

[0023] Furthermore, the calculation formula for analyzing the heat source temperature field in step S4 is:

[0024]

[0025] Among them, q is the welding line energy, λ is the thermal conductivity of the material, a is the thermal diffusion coefficient of the material, v is the moving speed of the heat source, r is the distance from the current observation point to the center of the heat source, and x is the horizontal distance from the current observation point to the center of the heat source.

[0026] Furthermore, in step S5, the temperature gradients in the x-direction, y-direction, and z-direction of the analytical temperature field are corrected using correction factors in three directions respectively. The calculation formula for correcting the analytical heat source temperature field is:

[0027]

[0028]

[0029] Among them, CV 1 、CV 2 、CV 3 are the correction factors in the x, y and z directions respectively; C 1 , C 2 , C 3 is the shape factor in the x direction, A 1 , A 2 , A 3 is the shape factor in the y direction, B 1 , B 2 , B 3 is the shape coefficient in the z direction; through these three groups of shape coefficients, the temperature gradient distribution in the three temperature transfer directions is adjusted respectively.

[0030] Furthermore, in step S7, the method for correcting the temperature gradient of the analytical heat source temperature field and maintaining consistency with the volume / area distribution heat source calculation results is that the error between the third evolution result and the fourth evolution result is less than the solution accuracy of the analytical temperature field.

[0031] Furthermore, the value range of the increased grid size in step S7 is 8 mm-15 mm.

[0032] The beneficial effects of the present invention are:

[0033] Based on the moving point analytical heat source temperature field, this scheme corrects the analytical temperature to obtain the corrected analytical heat source temperature field, and uses the function definition model of the corrected analytical heat source temperature field to efficiently solve the welding temperature field. On the basis of ensuring the accuracy of temperature solution, the calculation efficiency is significantly improved, and the dependence on grid density when calculating the welding temperature field is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the analytical heat source temperature field model with uniform motion.

[0035] Figure 2 This is a schematic diagram of the structure of aluminum alloy profile welding.

[0036] Figure 3 Schematic diagram of the first evolution result of the temperature field of the double ellipsoid heat source.

[0037] Figure 4 Schematic diagram of the second evolution result of the heat source temperature field.

[0038] Figure 5 Schematic diagram of the temperature field gradient distribution in the width direction of the heat source.

[0039] Figure 6 Schematic diagram of the temperature field gradient distribution in the depth direction of the heat source.

[0040] Figure 7 Schematic diagram of the third evolution result of the corrected analytical heat source temperature field.

[0041] Figure 8 Schematic diagram of the fourth evolution result after increasing the grid size. DETAILED DESCRIPTION

[0042] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0043] like Figure 2As shown, this scheme takes the aluminum alloy profile welding model as an application example. It has a large number of free surfaces for convective radiation heat exchange with the surrounding environment. When the moving point heat source analytical temperature field model is used to solve it, there is a large error with the volume / area distribution heat source calculation results. The application of the efficient analytical algorithm for the welding temperature field proposed in this scheme can significantly reduce the calculation cost and time.

[0044] The specific application steps of this solution are as follows:

[0045] S1: A three-dimensional model is established for the aluminum alloy thin-walled profile structure, using shell-solid coupling modeling: the weld area is solid, the mesh size is 2mm, the principle welding area is the shell, and the shell area mesh size is 4mm; the number of solid meshes is 80,000, and the number of shell meshes is 55,000. The mesh types are: shell (temperature field: DS4; stress field: S4R), solid (temperature field: DC3D8; stress field: C3D8R).

[0046] S2: Applied welding heat source: arc welding, double ellipsoid heat source.

[0047] The front ellipsoid and rear ellipsoid heat source models are:

[0048]

[0049] Where Q = μUI (μ is the effective coefficient, welding voltage U = 25V, welding current I = 220A), f f 、f r is the energy distribution coefficient of the front and rear ellipsoids (f f :f r =3:7), a, b f , b r , c are the shape parameters of the double ellipsoid heat source (a=c=5mm, b f =0.6a, b r =1.4a);

[0050] Welding speed: 20 mm / s; welding order: from left to right; the initial temperature of the model is 20 degrees Celsius, and convection and radiation heat exchange occurs between the free surface and the surrounding environment.

[0051] S3: Perform transient heat transfer temperature calculation and solve to obtain the first evolution result of temperature field distribution, such as Figure 3 shown.

[0052] S4: On the same local geometric three-dimensional model, only the temperature boundary conditions are loaded, and the temperature field is solved by defining the node temperature of the model with the analytical heat source temperature field function to obtain the second evolution result of the temperature field distribution; specifically, the calculation formula of the analytical heat source temperature field is:

[0053]

[0054] Where q = μUI / v, the second evolution result of the temperature field distribution is obtained by solving, such as Figure 4 As shown;

[0055] S5: derive the temperature distribution results of the first evolution result and the second evolution result of the temperature field respectively, and output the temperature distribution in the x direction, y direction and z direction respectively with the heat source of the quasi-steady-state temperature field as the center, and then use the correction factors in the three directions to correct the temperature gradients in the x direction, y direction and z direction of the analytical temperature field respectively, wherein the x direction is the welding movement direction, the y direction is the heat source width direction, and the z direction is the heat source depth direction;

[0056] The calculation formula for the corrected analytical heat source temperature field is:

[0057]

[0058] The correction factor for the welding movement direction is:

[0059]

[0060] The correction factors in the heat source width direction and heat source depth direction are:

[0061]

[0062] Among them, CV 1 、CV 2 、CV 3 are the correction factors in the x, y and z directions respectively; C 1 , C 2 , C 3 is the shape factor in the x direction, A 1 , A 2 , A 3 is the shape factor in the y direction, B 1 , B 2 , B 3 is the shape factor in the z direction.

[0063] By comparing the first evolution result with the second evolution result, the temperature gradient distribution in the three temperature transfer directions is adjusted respectively through the shape coefficients of these three groups. The correction results are as follows: Figure 5 and Figure 6 The correction coefficient is shown in the following table:

[0064]

[0065] S6: Apply the corrected analytical heat source to solve the temperature field and obtain the third evolution result of the temperature field distribution, such as Figure 7 shown.

[0066] S7: Increase the grid size (8 mm grid in the weld area), and repeat step S6 to obtain the fourth evolution result of the temperature field distribution, such as Figure 8 As shown; and the temperature gradient of the corrected analytical heat source temperature field is consistent with the volume / area distribution heat source calculation results, so that the reduction of the grid density has little effect on the solution accuracy of the analytical temperature field.

[0067] S8: Apply the function definition model of the modified analytical heat source temperature field to efficiently solve the welding temperature field. The calculation efficiency comparison is shown in the following table:

[0068]

[0069] In summary, this scheme significantly improves the calculation efficiency by applying the analytical algorithm of the modified analytical heat source temperature field. On the basis of ensuring the accuracy of temperature solution, the calculation efficiency is improved by about 16.4 times; at the same time, the dependence on mesh density in the calculation of welding temperature field is reduced.

Claims

1. An efficient analytical algorithm for welding temperature field, characterized in that: The following steps are involved: S1: Establish a local geometric 3D model of the weld and input the material’s thermal physical properties parameters that vary with temperature; S2: Melting welding heat source model with loading volume / area distribution heat flux; S3: Calculate and solve the transient heat transfer temperature and obtain the first evolution result of the temperature field distribution; S4: On the same local geometric three-dimensional model, only the temperature boundary conditions are loaded, and the model node temperatures are defined by the function of analyzing the heat source temperature field to solve the temperature field, and the second evolution result of the temperature field distribution is obtained; S5: deriving the temperature distribution results of the first evolution result and the second evolution result of the temperature field respectively, and outputting the temperature distribution in the x direction, y direction and z direction respectively with the heat source of the quasi-steady-state temperature field as the center, and then correcting the temperature gradient in the x direction, y direction and z direction of the analytical temperature field respectively, wherein the x direction is the welding movement direction, the y direction is the heat source width direction, and the z direction is the heat source depth direction; S6: On the same local geometric three-dimensional model, the boundary conditions of the model node temperature are defined by the function of the modified analytical heat source temperature field to solve the temperature field, and the third evolution result of the temperature field distribution is obtained; S7: increasing the grid size and repeating step S6 to obtain the fourth evolution result of the temperature field distribution, and making the temperature gradient of the modified analytical heat source temperature field and the volume / area distribution heat source calculation result consistent; S8: Apply the function definition model of the modified analytical heat source temperature field to efficiently solve the welding temperature field.

2. The efficient analytical algorithm for welding temperature field according to claim 1 is characterized in that: The thermophysical performance parameters in step S1 include density, thermal conductivity and specific heat capacity.

3. The efficient analytical algorithm for welding temperature field according to claim 1 is characterized in that: Step S2 includes setting the initial temperature of the melting welding heat source model, the ambient temperature, and the convection radiation boundary conditions with the surrounding environment.

4. The efficient analytical algorithm for welding temperature field according to claim 1 is characterized in that: The calculation formula for analyzing the heat source temperature field in step S4 is: Among them, q is the welding line energy, λ is the thermal conductivity of the material, a is the thermal diffusion coefficient of the material, v is the moving speed of the heat source, r is the distance from the current observation point to the center of the heat source, and x is the horizontal distance from the current observation point to the center of the heat source.

5. The efficient analytical algorithm for welding temperature field according to claim 4 is characterized in that: In step S5, the temperature gradients in the x-direction, y-direction, and z-direction of the analytical temperature field are corrected using correction factors in three directions respectively. The calculation formula for correcting the analytical heat source temperature field is: Among them, CV1, CV2, and CV3 are correction factors in the x-, y-, and z-directions, respectively; C1, C2, and C3 are shape coefficients in the x-direction, A1, A2, and A3 are shape coefficients in the y-direction, and B1, B2, and B3 are shape coefficients in the z-direction; through these three groups of shape coefficients, the temperature gradient distributions in the three temperature transfer directions are adjusted respectively.

6. The efficient analytical algorithm for welding temperature field according to claim 1 is characterized in that: The method for correcting the temperature gradient of the analytical heat source temperature field and the volume / area distribution heat source calculation results to be consistent in step S7 is that the error between the third evolution result and the fourth evolution result is less than the solution accuracy of the analytical temperature field.

7. The efficient analytical algorithm for welding temperature field according to claim 1 is characterized in that: The value range of the increased grid size in step S7 is 8 mm-15 mm.

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