A simulation calculation method for temperature field and stress field of metal laser additive and subtractive hybrid manufacturing

Abstract

A method for simulating and calculating the temperature field and stress field of metal laser additive and subtractive hybrid manufacturing relates to the technical field of metal laser additive and subtractive hybrid manufacturing, and specifically to a method for simulating and calculating the temperature field and stress field of laser additive and subtractive hybrid manufacturing. In order to solve the problem of low test accuracy of residual stress in the existing metal laser additive and subtractive hybrid manufacturing. Method: three-dimensional model establishment, model import, parameter setting, mesh division, environment setting, additive analysis step setting, additive simulation, additive data extraction, subtractive analysis step setting, subtractive simulation after additive manufacturing. The present invention can realize the dynamic simulation of the temperature field and stress field of the whole process of the additive manufacturing process and the subtractive manufacturing process of metal materials in metal laser additive and subtractive hybrid manufacturing, and provide a powerful means for predicting the residual stress in the additive and subtractive preparation process of metal materials, thereby preparing workpieces with excellent performance and meeting service requirements.

Description

Technical Field

[0001] The invention relates to the technical field of metal laser additive and subtractive hybrid manufacturing, and in particular to a temperature field and stress field simulation calculation method for laser additive and subtractive hybrid manufacturing. Background Art

[0002] Traditional laser additive manufacturing has low precision and a significant step effect on the surface, requiring subsequent subtractive processing to meet service requirements. In addition, for components with internal cavities, holes, curvatures and other structures, additive manufacturing technology is difficult to form in one piece, and the preparation efficiency is low and the cost is high.

[0003] At present, the advent of additive and subtractive hybrid manufacturing technology has almost perfectly solved the integrated and efficient preparation of large components with complex structures. Combining the advantages of additive and subtractive manufacturing, additive and subtractive hybrid manufacturing technology can realize continuous laser deposition and milling processes on the same equipment, which greatly reduces resource waste and increases manufacturing efficiency. However, the problem of excessive thermal stress caused by fast cooling speed and steep temperature gradient in traditional additive manufacturing still exists, and subsequent subtractive processing makes the thermal / mechanical coupling of residual stress more complex and difficult to predict. Excessive residual stress seriously affects the performance of the workpiece, and even causes deformation and cracking of the workpiece, posing a great safety hazard. Existing residual stress testing methods include the pinhole method (Wang Jiangchao, Zhou Fangming. Pinhole method for measuring welding residual stress [J]. Electric Welding Machine, 2008, 38(2):3.), the X-ray method (Wang Hequan, Zhang Yancong, Liu Yuanyuan. Analysis of error influencing factors of residual stress detection by X-ray diffraction method [J]. Mechanical Strength, 2021, 43(1):5.), the neutron diffraction method (Sun Guangai, Chen Bo. Neutron diffraction residual stress analysis technology and its application [J]. Nuclear Technology, 2007, 30(4):4.), etc. These methods have low accuracy and high cost for residual stress testing. In order to quickly and effectively predict residual stress and then prepare workpieces with excellent performance and meet service requirements, a residual stress simulation method is urgently needed to simulate and calculate the temperature field and stress field of the entire preparation process. Summary of the invention

[0004] In order to solve the problem of low residual stress test accuracy in existing metal laser additive and subtractive material hybrid manufacturing, the present invention proposes a temperature field and stress field simulation calculation method for metal laser additive and subtractive material hybrid manufacturing;

[0005] The temperature field and stress field simulation calculation method of the metal laser additive and subtractive hybrid manufacturing of the present invention is carried out according to the following steps:

[0006] (1) 3D modeling: Use 3D modeling software to build 3D models of the shapes of samples produced by additive and subtractive manufacturing and the shapes of tools used in subtractive processing;

[0007] (2) Model import: Import the three-dimensional model established in step (1) into ABAQUS software;

[0008] (3) Parameter setting: setting the material parameters, absolute zero and Boltzmann constant of the sample model;

[0009] (4) Meshing: Divide the model meshes of the sample model and the tool model;

[0010] (5) Environment setting: In the ABAQUS finite element software, the actual machining environment is set as the contact environment of the sample model and the tool model;

[0011] (6) Additive analysis step setting: Set the additive manufacturing analysis step using the birth-death unit method and set the heat dissipation time;

[0012] (7) Additive manufacturing simulation: Using a double ellipsoid laser heat source, the three-dimensional transient heat conduction equation is used to simulate the temperature field and stress field of additive manufacturing to obtain temperature field data and stress field data;

[0013] The expression of the three-dimensional transient heat conduction control differential equation is:

[0014]

[0015] In the three-dimensional transient heat conduction control differential equation, ρ is the material density, kg / m 3 ; Cp is the material's specific heat capacity at constant pressure, J / (kg·℃); T is the temperature, ℃; t is the process running time (s); λ is the material's thermal conductivity (W / m / ℃); Q is the heat flux density of the heat source (W / m 2 );

[0016] (8) Additive material data extraction: extract the temperature field and stress field data after additive manufacturing obtained in step (7) and import them into the load module of ABAQUS finite element software as predefined temperature field data and stress field data for subtractive processing;

[0017] (9) Subtractive analysis step setting: Check Johnson-Cook damage and damage evolution in the material properties, and set the displacement analysis step of the subtractive tool; at the same time, set the tool displacement distance, rotation direction and speed;

[0018] (10) Subtractive simulation after additive manufacturing: Based on the Johnson-Cook constitutive equation, simulation calculations are performed to obtain the final temperature field and stress field distribution data of metal laser additive and subtractive hybrid manufacturing;

[0019] The Johnson-Cook constitutive equation is:

[0020]

[0021] In the Johnson-Cook constitutive equation, σ f is the equivalent flow stress, N; is the equivalent plastic strain, %; is the equivalent plastic strain rate, s -1 ; is the reference strain rate, s -1 ; T r is room temperature, ℃; T m is the melting point temperature, ℃; T is the initial temperature when the material is deformed, ℃; A is the initial yield stress of the material, N; B is the strain hardening coefficient of the material; C is the strain rate hardening coefficient of the material; n is the hardening index of the material; m is the thermal softening index of the material.

[0022] The present invention can realize dynamic simulation of temperature field and stress field of the whole process of additive manufacturing process and subtractive manufacturing process of metal laser additive and subtractive hybrid manufacturing of metal materials, and the additive and subtractive processes can be continuous without interruption; in each process, the changes of temperature and stress of the material over time in the whole preparation process can be output, which provides a powerful means for predicting residual stress in the additive and subtractive preparation process of metal materials, and then prepares workpieces with excellent performance and meeting service requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the material addition and subtraction model of the four-edge milling cutter and the 304 stainless steel block sample in Example 1;

[0024] Figure 2 Schematic diagram of mesh division of the 304 stainless steel block sample and the additive and subtractive material model of the four-edge milling cutter in Example 1;

[0025] Figure 3 Schematic diagram of the double ellipsoid laser heat source in Example 1;

[0026] Figure 4 The figure is a simulation calculation result diagram of the stress field of 304 stainless steel added and subtracted in Example 1;

[0027] Figure 5 This is a diagram showing the simulation calculation results of the temperature field of the added and subtracted material of 304 stainless steel in Example 1. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0029] Specific implementation method 1: The temperature field and stress field simulation calculation method of metal laser additive and subtractive hybrid manufacturing in this implementation method is carried out according to the following steps:

[0030] (1) 3D modeling: Use 3D modeling software to build 3D models of the shapes of samples produced by additive and subtractive manufacturing and the shapes of tools used in subtractive processing;

[0031] (2) Model import: Import the three-dimensional model established in step (1) into ABAQUS software;

[0032] (3) Parameter setting: setting the material parameters, absolute zero and Boltzmann constant of the sample model;

[0033] (4) Meshing: Divide the model meshes of the sample model and the tool model;

[0034] (5) Environment setting: In the ABAQUS finite element software, the actual machining environment is set as the contact environment of the sample model and the tool model;

[0035] (6) Additive analysis step setting: Set the additive manufacturing analysis step using the birth-death unit method and set the heat dissipation time;

[0036] (7) Additive manufacturing simulation: Using a double ellipsoid laser heat source, the three-dimensional transient heat conduction equation is used to simulate the temperature field and stress field of additive manufacturing to obtain temperature field data and stress field data;

[0037] The expression of the three-dimensional transient heat conduction control differential equation is:

[0038]

[0039] In the three-dimensional transient heat conduction control differential equation, ρ is the material density, kg / m 3 ; Cp is the material's specific heat capacity at constant pressure, J / (kg·℃); T is the temperature, ℃; t is the process running time (s); λ is the material's thermal conductivity (W / m / ℃); Q is the heat flux density of the heat source (W / m 2 );

[0040] (8) Additive material data extraction: extract the temperature field and stress field data after additive manufacturing obtained in step (7) and import them into the load module of ABAQUS finite element software as predefined temperature field data and stress field data for subtractive processing;

[0041] (9) Subtractive analysis step setting: Check Johnson-Cook damage and damage evolution in the material properties, and set the displacement analysis step of the subtractive tool; at the same time, set the tool displacement distance, rotation direction and speed;

[0042] (10) Subtractive simulation after additive manufacturing: Based on the Johnson-Cook constitutive equation, simulation calculations are performed to obtain the final temperature field and stress field distribution data of metal laser additive and subtractive hybrid manufacturing;

[0043] The Johnson-Cook constitutive equation is:

[0044]

[0045] In the Johnson-Cook constitutive equation, σ f is the equivalent flow stress, N; is the equivalent plastic strain, %; is the equivalent plastic strain rate, s -1 ; is the reference strain rate, s -1 ; T r is room temperature, ℃; T m is the melting point temperature, ℃; T is the initial temperature when the material is deformed, ℃; A is the initial yield stress of the material, N; B is the strain hardening coefficient of the material; C is the strain rate hardening coefficient of the material; n is the hardening index of the material; m is the thermal softening index of the material.

[0046] This implementation has the following beneficial effects:

[0047] The present invention can realize dynamic simulation of temperature field and stress field of the whole process of additive manufacturing process and subtractive manufacturing process of metal laser additive and subtractive hybrid manufacturing of metal materials, and the additive and subtractive processes can be continuous without interruption; in each process, the changes of temperature and stress of the material over time in the whole preparation process can be output, which provides a powerful means for predicting residual stress in the additive and subtractive preparation process of metal materials, and then prepares workpieces with excellent performance and meeting service requirements.

[0048] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that the three-dimensional modeling software in step (1) is the three-dimensional modeling software provided by ABAQUS, Unigraphics NX, Proe or 3DS MAX.

[0049] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the three-dimensional modeling in step (1) is established using meter units.

[0050] Specific implementation method four: This implementation method is different from any one of specific implementation methods one to three in that the file format of the three-dimensional model imported into ABAQUS in step (2) includes IGES (*.igs), STEP (*.stp) or SAT (*.sat) and Parasolid (*.x_t).

[0051] Specific implementation method five: This implementation method is different from any one of specific implementation methods one to four in that: the material parameters in step (3) include the density, Young's modulus, Poisson's ratio, specific heat capacity, thermal conductivity and thermal expansion coefficient of the material.

[0052] Specific implementation method 6: This implementation method is different from any one of specific implementation methods 1 to 5 in that: in step (4), the grid output type is assigned to be temperature and displacement related.

[0053] Specific implementation method seven: This implementation method is different from any one of specific implementation methods one to six in that: in step (4), when dividing the model grid, the grid seed unit shape is selected as a hexahedron, and the division method is sweeping.

[0054] Specific embodiment 8: This embodiment differs from any one of the specific embodiments 1 to 7 in that the contact environment in step (5) includes the ambient temperature (°C), the thermal radiation coefficient (W / m 2 ), and create a mechanical boundary condition in the Loads module to completely fix the bottom surface of the substrate.

[0055] Specific implementation method 9: This implementation method is different from any one of specific implementation methods 1 to 8 in that the heat dissipation time in step (6) is the conversion time between material addition and material subtraction under actual processing conditions.

[0056] Specific implementation method ten: The present implementation method is different from any one of specific implementation methods one to nine in that the displacement analysis step of the subtractive tool in step (9) is the displacement of the tool in actual subtractive machining.

[0057] Example 1

[0058] The temperature field and stress field simulation calculation method of metal laser additive and subtractive hybrid manufacturing in this embodiment is performed according to the following steps:

[0059] (1) 3D modeling: Use 3D modeling software to build 3D models of the shapes of samples produced by additive and subtractive manufacturing and the shapes of tools used in subtractive processing;

[0060] The three-dimensional modeling software is the three-dimensional modeling software that comes with ABAQUS;

[0061] The three-dimensional modeling in step (1) is established using meter units; Figure 1 Schematic diagram of the material addition and subtraction model of the four-edge milling cutter and the 304 stainless steel block sample in Example 1;

[0062] (2) Model import: Import the three-dimensional model established in step (1) into ABAQUS software;

[0063] The file formats of the 3D model imported into ABAQUS in step (2) include IGES (*.igs), STEP (*.stp) or SAT (*.sat) and Parasolid (*.x_t);

[0064] (3) Parameter setting: setting the material parameters, absolute zero and Boltzmann constant of the sample model;

[0065] The material parameters in step (3) include density, Young's modulus, Poisson's ratio, specific heat capacity, thermal conductivity and thermal expansion coefficient of the material, the absolute zero is set to -273.15°C, and the Boltzmann constant is set to 0.0000000567;

[0066] The material parameters of 304 stainless steel used in Example 1 are: density 7930kg / m 3 , Young's modulus 18700000000Pa, specific heat capacity 500J / (k·℃), thermal conductivity 15.1W / (m·℃), thermal expansion coefficient 0.00003289651 / ℃;

[0067] (4) Meshing: Divide the model meshes of the sample model and the tool model, and assign the mesh output type to be temperature and displacement related;

[0068] In step (4), when dividing the model grid, the grid seed unit shape is selected as a hexahedron, and the division method is sweeping;

[0069] Figure 2 Schematic diagram of mesh division of the 304 stainless steel block sample and the additive and subtractive material model of the four-edge milling cutter in Example 1;

[0070] (5) Environment setting: In the ABAQUS finite element software, the actual machining environment is set as the contact environment of the sample model and the tool model;

[0071] In step (5), the contact environment includes the ambient temperature (°C), the thermal radiation coefficient (W / m 2 ) and a fixing plane of the substrate;

[0072] The ambient temperature of the 304 stainless steel sample model in Example 1 is 20°C, and the thermal radiation coefficient is 0.8 W / m 2 , and create mechanical boundary conditions in the Loads module to completely fix the bottom surface of the substrate.

[0073] (6) Additive analysis step setting: Set the additive manufacturing analysis step using the birth-death unit method and set the heat dissipation time;

[0074] The heat dissipation time in step (6) is the conversion time between material addition and material subtraction under actual processing conditions;

[0075] In Example 1, a 40-second conversion time is required after additive processing before subtractive processing can begin, so a 40-second heat dissipation time is set in the last analysis step;

[0076] (7) Additive manufacturing simulation: Using a double ellipsoid laser heat source, the three-dimensional transient heat conduction equation is used to simulate the temperature field and stress field of additive manufacturing to obtain temperature field data and stress field data;

[0077] The expression of the three-dimensional transient heat conduction control differential equation is:

[0078]

[0079] In the three-dimensional transient heat conduction control differential equation, ρ is the material density, kg / m 3 ; Cp is the material's specific heat capacity at constant pressure, J / (kg·℃); T is the temperature, ℃; t is the process running time (s); λ is the material's thermal conductivity (W / m / ℃); Q is the heat flux density of the heat source (W / m 2 );

[0080] The double ellipsoid laser heat source in step (7) is as follows Figure 3 As shown;

[0081] (8) Additive material data extraction: extract the temperature field and stress field data after additive manufacturing obtained in step (7) and import them into the load module of ABAQUS finite element software as predefined temperature field data and stress field data for subtractive processing;

[0082] (9) Subtractive analysis step setting: Check Johnson-Cook damage and damage evolution in the material properties, and set the displacement analysis step of the subtractive tool, and also set the displacement distance, rotation direction and speed of the tool;

[0083] The displacement analysis step of the subtractive tool in step (9) is the displacement of the tool in the actual subtractive machining;

[0084] In Example 1, the tool displacement distance is 20 cm, and the tool rotates clockwise at a speed of 1200 r / min;

[0085] (10) Subtractive simulation after additive manufacturing: Based on the Johnson-Cook constitutive equation, simulation calculations are performed to obtain the final temperature field and stress field distribution data of metal laser additive and subtractive hybrid manufacturing;

[0086] The Johnson-Cook constitutive equation in step (10) is:

[0087]

[0088] In the Johnson-Cook constitutive equation, σ f is the equivalent flow stress, N; is the equivalent plastic strain, %; is the equivalent plastic strain rate, s -1 ; is the reference strain rate, s -1 ; T r is room temperature, ℃; T mis the melting point temperature, ℃; T is the initial temperature when the material is deformed, ℃; A is the initial yield stress of the material, N; B is the strain hardening coefficient of the material; C is the strain rate hardening coefficient of the material; n is the hardening index of the material; m is the thermal softening index of the material;

[0089] Figure 4 The figure is a simulation calculation result diagram of the stress field of 304 stainless steel added and subtracted in Example 1; Figure 5 The figure is a simulation calculation result of the temperature field of 304 stainless steel in Example 1. This embodiment can realize the dynamic simulation of the temperature field and stress field of the whole process of the additive manufacturing process and the subtractive manufacturing process of the metal laser additive and subtractive hybrid manufacturing of metal materials, and the additive and subtractive processes can be continuous without interruption; in each process, the temperature and stress of the material can be output over time during the whole preparation process, which provides a powerful means for predicting the residual stress in the additive and subtractive preparation process of metal materials, and then prepares workpieces with excellent performance and meeting service requirements.

Claims

1. A method for simulating and calculating the temperature field and stress field of metal laser additive and subtractive hybrid manufacturing, characterized in that: The simulation calculation method of temperature field and stress field of metal laser additive and subtractive hybrid manufacturing is carried out according to the following steps: (1) 3D modeling: Use 3D modeling software to build 3D models of the shapes of samples produced by additive and subtractive manufacturing and the shapes of tools used in subtractive processing; (2) Model import: Import the three-dimensional model established in step (1) into ABAQUS software; (3) Parameter setting: setting the material parameters, absolute zero and Boltzmann constant of the sample model; (4) Meshing: Divide the model meshes of the sample model and the tool model; (5) Environment setting: In the ABAQUS finite element software, the actual machining environment is set as the contact environment of the sample model and the tool model; (6) Additive analysis step setting: Set the additive manufacturing analysis step using the birth-death unit method and set the heat dissipation time; (7) Additive manufacturing simulation: Using a double ellipsoid laser heat source, the three-dimensional transient heat conduction equation is used to simulate the temperature field and stress field of additive manufacturing to obtain temperature field data and stress field data; The expression of the three-dimensional transient heat conduction control differential equation is: In the three-dimensional transient heat conduction control differential equation, ρ is the material density, kg / m 3 ; Cp is the material's specific heat capacity at constant pressure, J / (kg·℃); T is the temperature, ℃; t is the process running time (s); λ is the material's thermal conductivity (W / m / ℃); Q is the heat flux density of the heat source (W / m 2 ); (8) Additive material data extraction: extract the temperature field and stress field data after additive manufacturing obtained in step (7) and import them into the load module of ABAQUS finite element software as predefined temperature field data and stress field data for subtractive processing; (9) Subtractive analysis step setting: Check Johnson-Cook damage and damage evolution in the material properties, and set the displacement analysis step of the subtractive tool; at the same time, set the tool displacement distance, rotation direction and speed; (10) Subtractive simulation after additive manufacturing: Based on the Johnson-Cook constitutive equation, simulation calculations are performed to obtain the final temperature field and stress field distribution data of metal laser additive and subtractive hybrid manufacturing; The Johnson-Cook constitutive equation is: In the Johnson-Cook constitutive equation, σ f is the equivalent flow stress, N; is the equivalent plastic strain, %; is the equivalent plastic strain rate, s -1 ; is the reference strain rate, s -1 ; T r is room temperature, ℃; T m is the melting point temperature, ℃; T is the initial temperature when the material is deformed, ℃; A is the initial yield stress of the material, N; B is the strain hardening coefficient of the material; C is the strain rate hardening coefficient of the material; n is the hardening index of the material; m is the thermal softening index of the material.

2. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1 is characterized by: The three-dimensional modeling software in step (1) is ABAQUS built-in three-dimensional modeling software, Unigraphics NX, Proe or 3DS MAX.

3. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1 is characterized by: The three-dimensional modeling in step (1) is established using meter units.

4. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1 is characterized by: The file formats of the 3D model imported into ABAQUS in step (2) include IGES (*.igs), STEP (*.stp) or SAT (*.sat) and Parasolid (*.x_t).

5. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1 is characterized by: The material parameters in step (3) include density, Young's modulus, Poisson's ratio, specific heat capacity, thermal conductivity and thermal expansion coefficient of the material.

6. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1 is characterized by: In step (4), the mesh output type is assigned to be temperature and displacement related.

7. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1 is characterized by: When dividing the model grid in step (4), the grid seed unit shape is selected as a hexahedron, and the division method is sweeping.

8. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1 is characterized by: The contact environment in step (5) includes the ambient temperature (°C), thermal radiation coefficient (W / m 2 ), and create a mechanical boundary condition in the Loads module to completely fix the bottom surface of the substrate.

9. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1 is characterized by: The heat dissipation time in step (6) is the conversion time between additive and subtractive processing under actual processing conditions.

10. The temperature field and stress field simulation calculation method for metal laser additive and subtractive hybrid manufacturing according to claim 1, characterized in that: The displacement analysis step of the subtractive tool in step (9) is the displacement of the tool in actual subtractive machining.

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