Intergranular fatigue crack initiation prediction method and system coupled with welding residual stress

Abstract

The present invention discloses a method and system for predicting the initiation of intergranular fatigue cracks coupled with welding residual stress, which belongs to the field of fatigue numerical simulation technology, including: based on a constructed crystal plastic crack propagation finite element model of a welded joint, defining a welding heat source function, simulating the temperature field of welding and cooling processes; based on the temperature field, according to the thermodynamic parameters of the material, obtaining the welding residual stress field, and predicting the initiation of intergranular fatigue cracks of the material by embedding the net slip damage parameter. The present invention can predict the initiation of fatigue intergranular cracks from a microscopic perspective, that is, it can accurately consider the influence of the welding residual stress field, and incorporate micromechanical information such as local stress concentration, crystal orientation, different microscopic regions, etc.

Description

Technical Field

[0001] The invention relates to the technical field of fatigue numerical simulation, and in particular to a method and system for predicting intergranular fatigue crack initiation coupled with welding residual stress. Background Art

[0002] Welding is a common connection method in mechanical manufacturing and structural engineering, and is widely used in bridges, buildings, ships, pipelines, pressure vessels and other fields. However, due to local heating and rapid cooling during welding, residual stress will be generated in the welding area. Fatigue crack initiation of welded joints refers to the gradual formation and expansion of tiny cracks in the material under repeated cyclic loads, which eventually leads to material or structural failure. Fatigue crack initiation has an important impact on the safety and service life of the structure. Therefore, studying the fatigue crack initiation of welded joints has important engineering practical significance and scientific value.

[0003] However, it is difficult to reveal the influence of welding residual stress on fatigue crack initiation by numerical simulation. At present, the commonly used simulation method is to divide the calculation of welding residual stress field and fatigue crack initiation into two separate parts, and introduce the calculation results of residual stress strain as a predefined field into the subsequent fatigue analysis. However, due to deformation coordination, once the strain field is introduced, part of the deformation will be released, and the real welding residual stress strain field cannot be represented. Since the existence of residual stress will affect the stress distribution and stress concentration area, if the welding residual stress is not considered, the most likely crack initiation position will be changed. Therefore, overcoming the shortcomings of simulation technology and introducing accurate welding residual stress strain field before fatigue crack initiation simulation analysis can make the simulated fatigue life closer to the real situation, provide more reliable life prediction, and avoid premature or late failure; on the other hand, it can accurately predict the possible crack initiation position, thereby improving the effectiveness of crack detection and monitoring. Therefore, it can more realistically reflect the high-risk areas of the welded joint and guide design improvements and structural optimization. Summary of the invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide an intergranular fatigue crack initiation prediction technology coupled with welding residual stress to overcome the difficulties existing in the existing simulation technology.

[0005] In order to achieve the above technical objectives, the present application provides a method for predicting intergranular fatigue crack initiation coupled with welding residual stress, comprising the following steps:

[0006] Based on the constructed crystal plastic crack propagation finite element model of the welded joint, the welding heat source function is defined to simulate the temperature field of the welding and cooling processes;

[0007] Based on the temperature field and the thermodynamic parameters of the material, the welding residual stress field is obtained, and the initiation of intergranular fatigue cracks in the material is predicted by embedding the net slip damage parameter.

[0008] Preferably, in the process of constructing the crystal plastic crack propagation finite element model, a polycrystalline finite element model of the weld joint is constructed according to the microstructure diagram of the weld joint of the base material, the weld material and the heat-affected zone and the random orientation of each grain, and the grid is divided as the crystal plastic crack propagation finite element model.

[0009] Preferably, in the process of acquiring the temperature field, the temperature field calculation process includes:

[0010] S21, create thermal analysis steps, namely welding process and cooling process;

[0011] S22. Define material thermal properties: density, specific heat and thermal conductivity;

[0012] S23, define the mesh attribute as heat transfer unit type DC3D8;

[0013] S24. Define boundary conditions: boundary heat exchange and thermal radiation;

[0014] S25. Apply body heat flux and calculate the temperature field.

[0015] Preferably, in the process of defining the welding heat source function, the welding heat source function is expressed as:

[0016]

[0017] Where q(r) is the heat flux density at a radius r from the heat source, U and I are the welding current and voltage, η is the arc efficiency, r0 is the arc radius, and r is the radius of the heat source at a certain point.

[0018] Preferably, in the process of obtaining the welding residual stress field, based on the calculation process of the temperature field, the material thermodynamic parameters are defined: elastic parameters, plastic parameters and thermal expansion coefficient; the thermal analysis step is changed to a static analysis step, and the analysis step duration is the same as the thermal analysis step; the unit type is changed to C3D8; the temperature field calculation result of step S25 is imported as a predefined temperature field, and after defining the boundary conditions, the welding residual stress field is calculated.

[0019] Preferably, in the process of calculating the welding residual stress field, based on the calculation process of the temperature field, the welding residual stress field is calculated by constructing an ideal thermoelastic-plastic constitutive model of the material, wherein the ideal thermoelastic-plastic constitutive model is expressed as:

[0020] {dε}={dε} e +{dε} T +{dε} p

[0021] Where {dε} represents the total strain increment, {dε} e represents the elastic strain increment, {dε} p represents the plastic strain increment, {dε} T represents the thermal strain increment.

[0022] Preferably, in the process of predicting the initiation, based on the welding residual stress field and according to the crystal plasticity constitutive model of the material, the net slip damage parameter is embedded, the net slip damage indicator factor is obtained, and the extended finite element crack growth criterion based on the net slip damage factor is generated to characterize the crack growth.

[0023] Preferably, in the process of constructing the crystal plasticity constitutive model, the crystal plasticity constitutive model is expressed as:

[0024]

[0025] Among them, L p is the plastic deformation rate gradient, is the plastic deformation gradient rate, is the inverse of the plastic deformation gradient, S α is the unit vector in the slip direction of the αth slip system, n α is the unit vector in the slip normal direction of the αth slip system, is the shear rate on the αth slip system.

[0026] The present invention also discloses an intergranular fatigue crack initiation prediction system coupled with welding residual stress, which is used to implement an intergranular fatigue crack initiation prediction method, comprising:

[0027] Temperature field calculation module, which is used to define welding heat source function and simulate the temperature field of welding and cooling process based on the constructed crystal plastic crack propagation finite element model of welding joint;

[0028] The initiation prediction module is used to obtain the welding residual stress field based on the temperature field and the thermodynamic parameters of the material, and predict the initiation of intergranular fatigue cracks of the material by embedding the net slip damage parameter.

[0029] Preferably, the temperature field measurement module is also used to construct a polycrystalline finite element model of the weld joint based on the microstructure diagram of the weld joint of the base material, the weld material and the heat-affected zone and the random orientation of each grain, and divide the grid as a crystal plastic crack extension finite element model.

[0030] The present invention discloses the following technical effects:

[0031] This paper couples the thermoelastic-plastic constitutive model for calculating welding residual stress and the crystal plastic constitutive model required for subsequent fatigue crack initiation analysis into one UMAT subroutine. The residual stress calculation and subsequent fatigue crack initiation analysis can be completed in one simulation operation, thus avoiding the introduction of an external pre-strain field that provides an unrealistic residual stress-strain field for subsequent fatigue analysis.

[0032] The present invention can predict the initiation of fatigue intergranular cracks from a microscopic perspective, that is, it can accurately consider the influence of welding residual stress field and incorporate micromechanical information such as local stress concentration, crystal orientation, different microscopic regions, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A flowchart of an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of a finite element model for heat conduction analysis according to an embodiment of the present invention;

[0036] Figure 3 This is a schematic diagram of the temperature field distribution after the heat source according to an embodiment of the present invention is heated for 60 seconds;

[0037] Figure 4 Schematic diagram of the temperature field and welding residual stress field distribution after welding cooling according to the embodiment of the present invention, wherein (a) is a schematic diagram of the temperature field distribution; (b) is a schematic diagram of the distribution of Mises stress in the residual stress field;

[0038] Figure 5 A schematic diagram of the intergranular fatigue crack initiation position and time predicted with and without considering welding residual stress according to an embodiment of the present invention;

[0039] Figure 6 It is a schematic diagram of the method flow of the present invention. DETAILED DESCRIPTION

[0040] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0041] like Figure 1-6 As shown, the present invention provides a method for predicting intergranular fatigue crack initiation coupled with welding residual stress, comprising the following steps:

[0042] Based on the constructed crystal plastic crack propagation finite element model of the welded joint, the welding heat source function is defined to simulate the temperature field of the welding and cooling processes;

[0043] Based on the temperature field and the thermodynamic parameters of the material, the welding residual stress field is obtained, and the initiation of intergranular fatigue cracks in the material is predicted by embedding the net slip damage parameter.

[0044] Further preferably, in the intergranular fatigue crack initiation prediction method provided by the present invention, in the process of constructing a finite element model of crystal plastic crack propagation, a polycrystalline finite element model of the weld joint is constructed according to the microstructure diagram of the weld joint of the base material, weld material and heat-affected zone and the random orientation of each grain, and the grid is divided as a finite element model of crystal plastic crack propagation.

[0045] Further preferably, in the method for predicting intergranular fatigue crack initiation provided by the present invention, in the process of obtaining the temperature field, the calculation process of the temperature field includes:

[0046] S21, create thermal analysis steps, namely welding process and cooling process;

[0047] S22. Define material thermal properties: density, specific heat and thermal conductivity;

[0048] S23, define the mesh attribute as heat transfer unit type DC3D8;

[0049] S24. Define boundary conditions: boundary heat exchange and thermal radiation;

[0050] S25. Apply body heat flux and calculate the temperature field.

[0051] Further preferably, in the intergranular fatigue crack initiation prediction method provided by the present invention, in the process of defining the welding heat source function, the welding heat source function is expressed as:

[0052]

[0053] Where q(r) is the heat flux density at a radius r from the heat source, U and I are the welding current and voltage, η is the arc efficiency, r0 is the arc radius, and r is the radius of the heat source at a certain point.

[0054] Further preferably, in the intergranular fatigue crack initiation prediction method provided by the present invention, in the process of obtaining the welding residual stress field, based on the calculation process of the temperature field, the material thermodynamic parameters are defined: elastic parameters, plastic parameters and thermal expansion coefficient; the thermal analysis step is changed to a static analysis step, and the analysis step duration is the same as the thermal analysis step; the unit type is changed to C3D8; the temperature field calculation result of step S25 is imported as a predefined temperature field, and after defining the boundary conditions, the welding residual stress field is calculated.

[0055] Further preferably, the intergranular fatigue crack initiation prediction method provided by the present invention calculates the welding residual stress field by constructing an ideal thermoelastic-plastic constitutive model of the material based on the calculation process of the temperature field during the calculation of the welding residual stress field, wherein the ideal thermoelastic-plastic constitutive model is expressed as:

[0056] {dε}={dε} e +{dε} T +{dε} p

[0057] Where {dε} represents the total strain increment, {dε} e represents the elastic strain increment, {dε} p represents the plastic strain increment, {dε} T represents the thermal strain increment.

[0058] Further preferably, the intergranular fatigue crack initiation prediction method provided by the present invention, in the process of predicting the initiation, based on the welding residual stress field and according to the crystal plasticity constitutive model of the material, embeds the net slip damage parameter, obtains the net slip damage indicator factor, generates an extended finite element crack propagation criterion based on the net slip damage factor, and characterizes the crack propagation.

[0059] Further preferably, in the method for predicting intergranular fatigue crack initiation provided by the present invention, in the process of constructing a crystal plasticity constitutive model, the crystal plasticity constitutive model is expressed as:

[0060]

[0061] Among them, L pis the plastic deformation rate gradient, is the plastic deformation gradient rate, is the inverse of the plastic deformation gradient, S α is the unit vector in the slip direction of the αth slip system, n α is the unit vector in the slip normal direction of the αth slip system, is the shear rate on the αth slip system.

[0062] The present invention also discloses an intergranular fatigue crack initiation prediction system coupled with welding residual stress, which is used to implement an intergranular fatigue crack initiation prediction method, comprising:

[0063] Temperature field calculation module, which is used to define welding heat source function and simulate the temperature field of welding and cooling process based on the constructed crystal plastic crack propagation finite element model of welding joint;

[0064] The initiation prediction module is used to obtain the welding residual stress field based on the temperature field and the thermodynamic parameters of the material, and predict the initiation of intergranular fatigue cracks of the material by embedding the net slip damage parameter.

[0065] Embodiment: The present invention provides a method for predicting intergranular fatigue crack initiation coupled with welding residual stress, comprising the following steps:

[0066] S1. Establish the crystal plasticity extended finite element model of the welded joint based on ABAQUS software. The specific steps are as follows:

[0067] S11, compile the PYTHON program to generate a microstructure diagram of the welded joint including the base material, the welding material and the heat-affected zone and the random orientation of each grain;

[0068] S12, importing the above microscopic model information into ABAQUS through a PYTHON script, generating a polycrystalline finite element model of the welded joint, and dividing the mesh;

[0069] S2. Compile the DFLUX subroutine to define the welding heat source function and simulate the temperature field of the welding and cooling process. The specific steps are as follows:

[0070] S21, create thermal analysis steps, namely welding process and cooling process;

[0071] S22. Define material thermal properties: density, specific heat and thermal conductivity;

[0072] S23, define the mesh attribute as heat transfer unit type DC3D8;

[0073] S24. Define boundary conditions: boundary heat exchange and thermal radiation, such as Figure 2 As shown;

[0074] S25, applying body heat flux, heating time is 60 seconds, and the temperature field is as follows Figure 3 As shown, the cooling time is 1800 seconds, and the temperature field after cooling is as follows Figure 4 (a)

[0075] S3. Compile the ideal thermoelastic-plastic constitutive model in the UMAT subroutine and calculate the welding residual stress field. The specific steps are as follows:

[0076] S31. Copy the temperature field calculation model and define the material thermodynamic parameters: elastic parameters, plastic parameters and thermal expansion coefficient;

[0077] S32, change the thermal analysis step to a static analysis step, and the analysis step duration is the same as the thermal analysis step;

[0078] S33, change the unit type to C3D8;

[0079] S34, import the temperature field calculation result of step S25 as a predefined temperature field, define boundary conditions, and calculate the welding residual stress field, such as Figure 4 (b)

[0080] S4, write the UMAT crystal plasticity constitutive model, embed the net slip damage parameter, add an analysis step after the analysis step in step S3, and apply fatigue load for calculation;

[0081] S5. Define the extended finite element crack growth criterion based on the net slip damage factor in the UDMGINI subroutine. The specific steps are as follows:

[0082] S51, call UMAT to calculate the net slip S, when the net slip S of the crack tip unit and the critical value S critical The ratio is less than 1, that is The crack does not expand; when the ratio is greater than or equal to 1, that is, Composite cracking criterion at the crack tip, the crack propagates forward;

[0083] S52, the extension direction is parallel to the slip system direction with the maximum net slip damage value;

[0084] The heat source function q(r) of step S2 is:

[0085]

[0086] Where q(r) is the heat flux density at a radius r from the heat source, U and I are the welding current and voltage, η is the arc efficiency, r0 is the arc radius, and r is the radius of the receiving heat source at a certain point and is defined by the following equation:

[0087] r 2 =x 2 +y 2

[0088] Where x and y are the coordinates of any point in the model.

[0089] The ideal thermoelastic-plastic constitutive equation in step S3 is:

[0090] {dε}={dε] e +{dε} T +{dε} p

[0091] The total strain increment {dε} can be divided into the elastic strain increment {dε} e , plastic strain increment {dε} p and thermal strain increment {dε} T ; In the elastic zone there are:

[0092] (dσ)=[D] e (dε)-[C] e dT

[0093]

[0094] Where {dσ} is the stress increment, {α′} is the thermal expansion coefficient, [D] e is the elastic stiffness matrix, T is the temperature; in the plastic zone:

[0095]

[0096] in, is the Mises stress, is the yield stress function related to the equivalent plastic strain and temperature.

[0097] The crystal plasticity constitutive equation of step S4 is:

[0098]

[0099] Among them, L p is the plastic deformation rate gradient, is the plastic deformation gradient rate, is the inverse of the plastic deformation gradient, S α is the unit vector in the slip direction of the αth slip system, n α is the unit vector in the slip normal direction of the αth slip system, is the shear rate on the αth slip system, which can be expressed as:

[0100]

[0101] in, is the reference shear rate on the αth slip system, τ αis the analytical shear stress on the αth slip system, X α is the back stress on the αth slip system, n is the flow rate index, g α is the slip resistance on the αth slip system, and its evolution equation is:

[0102]

[0103] in, is the slip resistance increment on the αth slip system, h αα is the self-hardening modulus on the same slip system, h αβ is the potential hardening modulus between different slip systems, h0 is the initial hardening modulus, γ is the accumulated shear strain on all slip systems, τ s is the saturated slip resistance, τ0 is the initial critical analytical shear stress, q is the material constant, is the shear rate on the β slip system.

[0104] The net slip damage factor S of step S4 is:

[0105]

[0106] Among them, m, is the material parameter, τ α0 is the force required for the dislocation to move at unit speed on the α slip system, S α is the distance of dislocation movement in the α slip system.

[0107] The correct welding residual stress field is introduced into the calculation of the fatigue crack initiation model by the above method. The fatigue crack initiation position and time predicted by considering and not considering the welding residual stress are as follows: Figure 5 shown.

[0108] This paper couples the thermoelastic-plastic constitutive model for calculating welding residual stress and the crystal plastic constitutive model required for subsequent fatigue crack initiation analysis into one UMAT subroutine. The residual stress calculation and subsequent fatigue crack initiation analysis can be completed in one simulation operation, thus avoiding the introduction of an external pre-strain field that provides an unrealistic residual stress-strain field for subsequent fatigue analysis.

[0109] The present invention can predict the initiation of fatigue intergranular cracks from a microscopic perspective, that is, it can accurately consider the influence of welding residual stress field and incorporate micromechanical information such as local stress concentration, crystal orientation, different microscopic regions, etc.

[0110] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0111] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0112] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for predicting intergranular fatigue crack initiation coupled with welding residual stress, characterized in that: The following steps are involved: Based on the constructed crystal plastic crack propagation finite element model of the welded joint, the welding heat source function is defined to simulate the temperature field of the welding and cooling processes; Based on the temperature field and the thermodynamic parameters of the material, the welding residual stress field is obtained, and the initiation of intergranular fatigue cracks of the material is predicted by embedding the net slip damage parameter; In the process of constructing the crystal plastic crack propagation finite element model, a polycrystalline finite element model of the welded joint is constructed according to the microstructure diagram of the welded joint of the base material, the weld material and the heat-affected zone and the random orientation of each grain, and a mesh is divided to serve as the crystal plastic crack propagation finite element model; In the process of acquiring the temperature field, the calculation process of the temperature field includes: S21, create thermal analysis steps, namely welding process and cooling process; S22. Define material thermal properties: density, specific heat and thermal conductivity; S23, define the mesh attribute as heat transfer unit type DC3D8; S24. Define boundary conditions: boundary heat exchange and thermal radiation; S25, applying body heat flux to calculate the temperature field; In the process of defining the welding heat source function, the welding heat source function is expressed as: Where q(r) is the heat flux density at a radius r from the heat source, U and I are the welding current and voltage, η is the arc efficiency, r0 is the arc radius, and r is the radius of the heat source at a certain point; In the process of obtaining the welding residual stress field, based on the calculation process of the temperature field, define the material thermodynamic parameters: elastic parameters, plastic parameters and thermal expansion coefficient; change the thermal analysis step to a static analysis step, and the analysis step duration is the same as the thermal analysis step; change the unit type to C3D8; import the temperature field calculation result of step S25 as a predefined temperature field, and after defining the boundary conditions, calculate the welding residual stress field; In the process of calculating the welding residual stress field, based on the calculation process of the temperature field, the welding residual stress field is calculated by constructing an ideal thermoelastic-plastic constitutive model of the material, wherein the ideal thermoelastic-plastic constitutive model is expressed as: {dε}={dε} e +{dε} T +{dε} p Where {dε} represents the total strain increment, {dε} e represents the elastic strain increment, {dε} p represents the plastic strain increment, {dε} T represents the thermal strain increment; In the process of predicting the initiation, based on the welding residual stress field and according to the crystal plasticity constitutive model of the material, a net slip damage parameter is embedded, a net slip damage indicator factor is obtained, an extended finite element crack growth criterion based on the net slip damage factor is generated, and crack growth is characterized; In the process of constructing the crystal plasticity constitutive model, the crystal plasticity constitutive model is expressed as: Among them, L p is the plastic deformation rate gradient, is the plastic deformation gradient rate, is the inverse of the plastic deformation gradient, S α is the unit vector in the slip direction of the αth slip system, n α is the unit vector in the slip normal direction of the αth slip system, is the shear rate on the αth slip system.

2. Intergranular fatigue crack initiation prediction system coupled with welding residual stress, characterized by: include: Temperature field calculation module, which is used to define welding heat source function and simulate the temperature field of welding and cooling process based on the constructed crystal plastic crack propagation finite element model of welding joint; The initiation prediction module is used to obtain the welding residual stress field based on the temperature field and the thermodynamic parameters of the material, and predict the initiation of intergranular fatigue cracks of the material by embedding the net slip damage parameter; the temperature field measurement module is also used to construct a polycrystalline finite element model of the welded joint according to the microstructure diagram of the welded joint of the parent material, the weld material and the heat-affected zone and the random orientation of each grain, and divide the grid as the crystal plastic crack propagation finite element model; In the process of acquiring the temperature field, the calculation process of the temperature field includes: S21, create thermal analysis steps, namely welding process and cooling process; S22. Define material thermal properties: density, specific heat and thermal conductivity; S23, define the mesh attribute as heat transfer unit type DC3D8; S24. Define boundary conditions: boundary heat exchange and thermal radiation; S25, applying body heat flux to calculate the temperature field; In the process of defining the welding heat source function, the welding heat source function is expressed as: Where q(r) is the heat flux density at a radius r from the heat source, U and I are the welding current and voltage, η is the arc efficiency, r0 is the arc radius, and r is the radius of the heat source at a certain point; In the process of obtaining the welding residual stress field, based on the calculation process of the temperature field, define the material thermodynamic parameters: elastic parameters, plastic parameters and thermal expansion coefficient; change the thermal analysis step to a static analysis step, and the analysis step duration is the same as the thermal analysis step; change the unit type to C3D8; import the temperature field calculation result of step S25 as a predefined temperature field, and after defining the boundary conditions, calculate the welding residual stress field; In the process of calculating the welding residual stress field, based on the calculation process of the temperature field, the welding residual stress field is calculated by constructing an ideal thermoelastic-plastic constitutive model of the material, wherein the ideal thermoelastic-plastic constitutive model is expressed as: {dε}={dε} e +{dε} T +{dε} p Where {dε} represents the total strain increment, {dε} e represents the elastic strain increment, {dε} p represents the plastic strain increment, {dε} T represents the thermal strain increment; In the process of predicting the initiation, based on the welding residual stress field and according to the crystal plasticity constitutive model of the material, a net slip damage parameter is embedded, a net slip damage indicator factor is obtained, an extended finite element crack growth criterion based on the net slip damage factor is generated, and crack growth is characterized; In the process of constructing the crystal plasticity constitutive model, the crystal plasticity constitutive model is expressed as: Among them, L p is the plastic deformation rate gradient, is the plastic deformation gradient rate, is the inverse of the plastic deformation gradient, S α is the unit vector in the slip direction of the αth slip system, n α is the unit vector in the slip normal direction of the αth slip system, is the shear rate on the αth slip system.

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