A full-stage creep life prediction method coupling residual stress and creep damage

Abstract

The application discloses a full-stage creep life prediction method for coupling residual stress and creep damage, and belongs to the technical field of creep life prediction. The prediction method comprises the following steps: a finite element model of a welded workpiece is established, a welding process simulation is performed, and welding residual stress distribution data are obtained; a creep constitutive model of a heat treatment process is established, a post-welding heat treatment stress release damage simulation is performed on the welded workpiece on the basis of the welding residual stress distribution data, and stress and strain distribution data after heat treatment are obtained as historical parameters of subsequent service of the welded workpiece; a service process of the welded workpiece is simulated on the basis of the stress and strain distribution data after heat treatment, and creep damage in the service process is obtained; and a judgment basis for creep failure of the welded workpiece is set, and the creep life of the welded workpiece is determined. The application can realize physical continuity of internal state evolution of a material from welding manufacturing to a service process, and accurately simulate creep damage in the service process.

Description

Technical Field

[0001] This invention relates to the field of creep life prediction technology, and specifically to a method for predicting creep life across all stages by coupling residual stress and creep damage. Background Technology

[0002] Creep life prediction is crucial in the design and safety assessment of high-temperature components of pressure vessels. Traditional creep life prediction methods typically rely on load and material data during service life, neglecting residual stresses generated during manufacturing processes (such as heat treatment, welding, and forging) and their evolution before service. To improve the accuracy of creep life prediction, some researchers have studied the impact of residual stress on creep life; however, existing methods considering the influence of residual stress on creep life have the following limitations:

[0003] (1) Empirical coefficient method: The residual stress is simply equivalent to a safety factor or influence factor. It lacks a physical mechanism and has low prediction accuracy and is conservative.

[0004] (2) Static initial condition method: Only the "static" residual stress field after heat treatment is used as the initial stress state for service creep analysis. This method ignores the dynamic relaxation history of residual stress during heat treatment, as well as key state variables such as cumulative creep strain that accompany this history.

[0005] (3) Equivalent initial rate method: The residual stress is equivalent to the initial creep rate, which breaks the continuity of damage development between the manufacturing stage and the service stage.

[0006] In other words, the calculation and analysis process of existing methods is discontinuous and historical information is broken, failing to establish a complete damage evolution chain from manufacturing to service. This makes it impossible to accurately characterize the actual impact of residual stress on creep life, thus affecting the accuracy of creep life prediction. Summary of the Invention

[0007] To address the technical problems existing in the prior art, this invention provides a method for predicting creep life across all stages by coupling residual stress and creep damage.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for predicting creep life across all stages by coupling residual stress and creep damage includes the following steps:

[0010] S1. In the finite element simulation software, a finite element model is established based on the structural and material parameters of the welded workpiece. The welding moving heat source model and boundary conditions are applied to simulate the welding process and obtain the welding residual stress distribution data.

[0011] S2. Considering the influence of varying temperature and stress on creep damage of welded workpieces during heat treatment, establish a creep constitutive model for the heat treatment process. Based on the welding residual stress distribution data obtained in step S1, simulate the stress release damage of the welded workpiece after post-weld heat treatment and obtain the stress and strain distribution data after heat treatment as historical parameters for subsequent service of the welded workpiece.

[0012] S3. Considering the influence of load on creep damage of welded workpiece during service, establish a creep constitutive model for service process, and simulate creep damage of welded workpiece during service process based on the stress and strain distribution data after heat treatment obtained in step S2, and obtain creep damage during service process.

[0013] S4. Set the criteria for judging creep failure of the welded workpiece, and compare and analyze the cumulative creep damage obtained in step S3 during service with the criteria for judging creep failure to determine the creep life of the welded workpiece.

[0014] Furthermore, in step S1, the welding moving heat source model adopts one of the following: Rosonthal analytical heat source model, Gaussian heat source model, hemispherical heat source model, ellipsoidal heat source model, or double ellipsoidal heat source model.

[0015] Furthermore, the creep constitutive model for the heat treatment process established in step S2 is as follows:

[0016] (2-1);

[0017] In the formula, For creep strain rate, For equivalent stress, Deformation activation energy, This is the universal gas constant. For temperature, Absolute temperature , , These are parameters related to the material.

[0018] Furthermore, the parameters in step S2 , The data was obtained through a fitting method, and the fitting process is as follows:

[0019] (1) The creep constitutive model of the heat treatment process established in step S2 Expanded using Taylor series:

[0020] (2-2);

[0021] At low stress levels, Approximately The relationship between strain rate, temperature, and stress is described by a power-law equation, transforming the creep constitutive model of the heat treatment process into:

[0022] (2-3);

[0023] Under high stress levels, Approximately The relationship between strain rate, temperature, and stress is described by an exponential equation, transforming the creep constitutive model of the heat treatment process into:

[0024] (2-4);

[0025] In the formula, Refers to low stress level , High stress level , , , , The equivalent stress index is obtained by approximating it using a power-law equation or an exponential equation. For natural numbers, ;

[0026] (2) Taking the logarithm of both sides of formulas (2-1), (2-3), and (2-4), we get:

[0027] (2-5);

[0028] (2-6);

[0029] (2-7);

[0030] (3) Test at least three sets of creep curves under different stresses at the same temperature, and plot them respectively. , , The scatter plots were generated, and linear fitting was performed on each plot. Based on the slope of the fitted curves, the following can be obtained: , , and according to get .

[0031] Furthermore, the parameters in step S2 , The data was obtained through a fitting method, and the fitting process is as follows:

[0032] After fitting the parameters , Based on this, formula (2-5) is transformed into and The relation is:

[0033] (2-8);

[0034] Then, at least three sets of creep curves were tested at different temperatures under the same creep strain rate, and plotted. The scatter plot was obtained, and a linear fit was performed. The slope and intercept of the fitted curve were then used to obtain... , .

[0035] Furthermore, the service process creep constitutive model established in step S3 is as follows:

[0036] (3-1);

[0037] (3-2);

[0038] ;

[0039] (3-3);

[0040] (3-4);

[0041] (3-5);

[0042] (3-6);

[0043] (3-7);

[0044] (3-8);

[0045] (3-9);

[0046] (3-10);

[0047] (3-11);

[0048] In the formula, For creep strain rate, The initial creep strain rate is based on the stress and temperature after heat treatment. This represents the cumulative amount of creep damage. For creep damage rate, ~ and ~ The creep damage coefficient of the welded workpiece material. , , , , , Parameters were calculated for the Omega creep damage model process. These are the input parameters for the Omega creep damage model. For equivalent stress, , , It is a triaxial principal stress. For time, For temperature.

[0049] Furthermore, in step S3, when simulating creep damage during the service process of the welded workpiece, the initial creep stress during the service process is the sum of the stress after the load is applied and the stress after heat treatment, and the initial creep strain during the service process is the cumulative creep strain during the heat treatment process.

[0050] Furthermore, the criteria for determining creep failure in step S4 are as follows:

[0051] When the cumulative creep damage at a certain point or section on a welded workpiece reaches the creep damage critical value at a certain moment, the welded workpiece is determined to have creep failure, and the corresponding time is the creep life of the welded workpiece.

[0052] Alternatively, if the service life reaches 1 million hours but the cumulative creep damage of the welded workpiece is still less than the creep damage critical value, then 1 million hours shall be taken as the creep life of the welded workpiece.

[0053] Furthermore, the creep constitutive model of the heat treatment process in step S2 and the creep constitutive model of the service process in step S3 are respectively written using CREEP and USDFLD subroutines. Both CREEP and USDFLD subroutines include subroutine interfaces and script interfaces to realize the switching of creep constitutive models of the heat treatment process and the service process, as well as the transmission of various parameters. The CREEP and USDFLD subroutines are embedded into the finite element software for secondary development to obtain an integrated finite element simulation model of welding-heat treatment-service.

[0054] The beneficial effects of this invention are as follows:

[0055] This invention provides a full-stage creep life prediction method that couples residual stress and creep damage. Through a unified finite element platform and custom subroutines, an integrated finite element simulation model of welding-heat treatment-service is established, realizing automatic connection between each stage. Historical parameters such as residual stress and cumulative creep strain after heat treatment are transferred to the service state, ensuring the physical continuity of the material's internal state evolution from welding and manufacturing to service, thereby accurately simulating creep damage during service. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a flowchart of the prediction method of the present invention;

[0058] Figure 2 This is the uniaxial creep tensile curve of Embodiment 1 of the present invention under different stresses at the same temperature;

[0059] Figure 3 The drawing is shown in Embodiment 1 of the present invention. , , Fitted curve, where (a) is The fitted curve, (b) is The fitted curve, (c) is Fitted curve;

[0060] Figure 4 The figures for Embodiment 1 of the present invention are uniaxial creep tensile curves at different temperatures and the same strain rate.

[0061] Figure 5 Drawing for Embodiment 1 of the present invention Fitted curve;

[0062] Figure 6 This is a creep damage cloud map obtained from simulation in Embodiment 1 of the present invention;

[0063] Figure 7 This is a creep damage cloud map obtained from simulation in Comparative Example 1 of the present invention;

[0064] Figure 8 This is a creep damage cloud map obtained from simulation in Comparative Example 2 of the present invention. Detailed Implementation

[0065] This invention provides a method for predicting creep life across all stages by coupling residual stress and creep damage. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0066] Reference Figure 1 This embodiment provides a method for predicting creep life across all stages by coupling residual stress and creep damage. The specific steps are as follows:

[0067] S1. In Abaqus finite element simulation software, a finite element model is established based on the structural and material parameters of the welded workpiece. The welding moving heat source model and boundary conditions are applied to simulate the welding process. During the welding process simulation, the temperature field is first obtained, and then the temperature field data is used as a predefined field to calculate the stress and obtain the welding residual stress distribution data.

[0068] S2. Considering the influence of varying temperature and stress on creep damage of welded workpieces during heat treatment, establish a creep constitutive model for the heat treatment process. Based on the welding residual stress distribution data obtained in step S1, simulate the stress release damage of the welded workpiece after post-weld heat treatment and obtain the stress and strain distribution data after heat treatment as historical parameters for subsequent service of the welded workpiece.

[0069] S3. Considering the influence of load on creep damage of welded workpiece during service, establish a creep constitutive model for service process, and simulate creep damage of welded workpiece during service process based on the stress and strain distribution data after heat treatment obtained in step S2, and obtain creep damage during service process.

[0070] S4. Set the criteria for judging creep failure of the welded workpiece, and compare and analyze the cumulative creep damage obtained in step S3 during the service process with the criteria for judging creep failure to determine the creep life of the welded workpiece.

[0071] The creep constitutive models for the heat treatment process in step S2 and the service process in step S3 are written using CREEP and USDFLD subroutines, respectively. Both CREEP and USDFLD subroutines include subroutine interfaces and script interfaces. The subroutine interfaces are based on the Fortran language and are used to directly embed the creep constitutive models for the heat treatment and service processes during the solution process, realizing the gradual update of creep strain evolution, equivalent stress response, and internal state variables, thus ensuring the numerical stability and convergence of the calculation. The script interfaces are based on the Python language and are mainly used in the preprocessing and postprocessing stages (heat treatment stage and service stage), uniformly scheduling creep parameters, temperature, and stress field variables, and supporting rapid calculation and result extraction for multiple working conditions and multiple parameter combinations. By embedding the CREEP and USDFLD subroutines into the Abaqus finite element software for secondary development, an integrated finite element simulation model of welding-heat treatment-service is obtained, realizing the transfer of residual stress and creep strain history parameters throughout the entire process. In the subsequent simulation of creep damage during the service process of welded workpieces, the initial creep stress during the service process is the superposition of the stress after the load is applied and the stress after heat treatment, and the initial creep strain during the service process is the cumulative creep strain during the heat treatment process.

[0072] Specifically, in step S1 above, the welding moving heat source model adopts one of the following: Rosonthal analytical heat source model, Gaussian heat source model, hemispherical heat source model, ellipsoidal heat source model, or double ellipsoidal heat source model. Among them, the double ellipsoidal heat source model is considered to be the most ideal model for tungsten inert gas welding.

[0073] In step S2 above, to more accurately describe the stress relaxation behavior at different temperatures, a hyperbolic sine model is used to establish a creep constitutive model for the heat treatment process, which is:

[0074] (2-1);

[0075] In the formula, For creep strain rate, For equivalent stress, Deformation activation energy, This is the universal gas constant. For temperature, Absolute temperature , , These are material-related parameters, and Specifically, it refers to the stress index related to the material. Specifically, it refers to the power-law exponent related to materials. Specifically, it refers to the hyperbolic sine multiplier related to materials.

[0076] The above-mentioned creep constitutive model for the heat treatment process takes into account the physical characteristics of varying temperature and stress during the heat treatment process, and is suitable for numerical simulation of post-weld stress relief heat treatment.

[0077] The parameters in formula (2-1) above are obtained through fitting, and the specific process is as follows:

[0078] (1) The creep constitutive model of the heat treatment process established in step S2 Expanded using Taylor series:

[0079] (2-2);

[0080] At low stress levels ( Under ) can Approximately The relationship between strain rate, temperature, and stress is described by a power-law equation, transforming the creep constitutive model of the heat treatment process into:

[0081] (2-3);

[0082] At high stress levels ( Under ) can Approximately The relationship between strain rate, temperature, and stress is described by an exponential equation, transforming the creep constitutive model of the heat treatment process into:

[0083] (2-4);

[0084] In the formula, Refers to low stress level , High stress level , , , , The equivalent stress index is obtained by approximating it using a power-law equation or an exponential equation. For natural numbers, ;

[0085] (2) Taking the logarithm of both sides of formulas (2-1), (2-3), and (2-4), we get:

[0086] (2-5);

[0087] (2-6);

[0088] (2-7);

[0089] Assuming the deformation activation energy is a temperature-independent variable, the following equations (2-5), (2-6), and (2-7) are analyzed respectively. Seeking information about , , The first derivative of is given by the following expression:

[0090] (2-9);

[0091] (2-10);

[0092] (2-11);

[0093] From the above formulas (2-6) and (2-7), it can be seen that when the temperature is constant, It is a constant value at the corresponding temperature. , It is a constant value. At this point, the curve is solved. , and The linear slope can be used to obtain the result. , The value;

[0094] (3) Test at least three sets of creep curves under different stresses at the same temperature, and plot them respectively. , , The scatter plots were generated, and linear fitting was performed on each plot. Based on the slope of the fitted curves, the following can be obtained: , , and according to get ;

[0095] (4) After fitting the parameters , Based on this, formula (2-5) is transformed into and The relation is:

[0096] (2-8);

[0097] Then, at least three sets of creep curves were tested at different temperatures under the same creep strain rate, and plotted. The scatter plot was obtained, and a linear fit was performed. The slope and intercept of the fitted curve were then used to obtain... , .

[0098] In addition, for ease of understanding, the formulas above are explained below. and The differences will be explained in the overall heat treatment process creep constitutive model (2-1). These are global parameters obtained from regression across the entire stress range, reflecting the overall deformation mechanism characteristics of the material over a wide stress range; while It is the apparent index obtained by local linearization within the low / high stress region, that is, the equivalent stress index obtained after approximating the low / high stress region using a power-law / exponential equation. When using a global model to predict the stress behavior of a certain interval, It does not require and The numerical values ​​are equal; it is sufficient to ensure that the predicted strain rate in the stress zone is consistent with the experimental results.

[0099] The service process creep constitutive model established in step S3 above is as follows:

[0100] (3-1);

[0101] (3-2);

[0102] ;

[0103] (3-3);

[0104] (3-4);

[0105] (3-5);

[0106] (3-6);

[0107] (3-7);

[0108] (3-8);

[0109] (3-9);

[0110] (3-10);

[0111] (3-11);

[0112] In the formula, For creep strain rate, The initial creep strain rate is based on the stress and temperature after heat treatment. This represents the cumulative amount of creep damage. For creep damage rate, ~ and ~ The creep damage coefficient of the welded workpiece material. , , , , , Parameters were calculated for the Omega creep damage model process. These are the input parameters for the Omega creep damage model. For equivalent stress, , , It is a triaxial principal stress. For time, For temperature.

[0113] The above-mentioned service process creep constitutive model adopts the existing Omega creep damage model, specifically the ASME standard case ASME2605-4. Its parameters can be selected from the standard according to the material properties of the welded workpiece, without the need for further creep testing.

[0114] The criteria for determining creep failure in step S4 above are as follows:

[0115] When the cumulative creep damage at a certain point or section on a welded workpiece reaches the creep damage critical value at a certain moment, the welded workpiece is determined to have creep failure, and the corresponding time is the creep life of the welded workpiece.

[0116] Alternatively, if the service life reaches 1 million hours but the cumulative creep damage of the welded workpiece is still less than the creep damage critical value, then 1 million hours shall be taken as the creep life of the welded workpiece.

[0117] When using creep damage threshold as the criterion, different thresholds need to be set for different locations. For the conventional base metal area, the threshold is 0.95~1.0; for the base metal area near the weldment and all welded joints, the threshold is less than 0.5 within 25mm of the weld groove, thus ensuring the structural safety at the weld.

[0118] Example 1

[0119] This embodiment uses a narrow-gap welded joint in the cylinder of a hydrogenation reactor as an example to illustrate the implementation process of the above prediction method.

[0120] In this embodiment, the material of the narrow gap welded joint of the hydrogenation reactor shell is 2.25Cr1MoV. The welding process parameters are: welding voltage 22V, current 160A, and speed 20cm / min; the heat treatment process parameters are: first, heat up to 400℃ at a rate of 100℃ / h, then heat up to the heat treatment holding temperature at a rate of 55℃ / h, hold at 705℃ for 5h, then cool with the furnace, and then air cool naturally to room temperature after the temperature drops to 400℃; the service conditions are: service load internal pressure 18.9MPa, service temperature is: heat up to 474℃ at a rate of 100℃ / h, and then maintain a stable temperature of 474℃.

[0121] To ensure the smooth progress of creep life prediction for narrow-gap welded joints in hydrogenation reactor shells, it is necessary to predetermine the parameters in the creep constitutive model during heat treatment and the parameters in the creep constitutive model during service.

[0122] For the parameters in the creep constitutive model of the heat treatment process , Three groups of 2.25Cr1MoV alloy samples were taken and uniaxial creep tests were conducted at 520℃ under three different stresses (260MPa, 270MPa, and 280MPa) to obtain creep-tensile curves, as shown below. Figure 2 As shown; then, the experimental data was imported using Origin software, processed, and the steady-state creep strain rate of three different stress-creep curves was plotted. , , A scatter plot was generated, and a linear fit was performed on the three factors. The fitted curve is shown below. Figure 3 As shown, based on the slope of the fitted curve, we can obtain... 11.5783 13.9583 It is 0.0614, and according to get It is 0.004399.

[0123] For the parameters in the creep constitutive model of the heat treatment process , Three groups of 2.25Cr1MoV alloy samples were taken and subjected to steady-state strain rates of 7×10⁻⁶ at 600℃, 650℃, and 690℃. -5 s -1 To obtain creep-tension curves through uniaxial creep experiments, such as... Figure 4 As shown; then, the experimental data was imported using Origin software, processed, and the steady-state creep strain rate of three different stress-creep curves was plotted. The scatter plot was generated, and a linear fit was performed. The fitted curve is shown below. Figure 5 As shown, the slope and intercept of the fitted curve are obtained. The value is 289982.2. 3.46×10 11 .

[0124] The parameters in the service process creep constitutive model are set with reference to the Omega creep damage parameters for hydrogenation reactors in standard ASME Code 2605, as shown in Table 1 below.

[0125] Table 1. Parameters of the creep constitutive model during service.

[0126]

[0127] Based on the parameters determined in the creep constitutive models for the heat treatment process and the service process, this embodiment first establishes a finite element model in Abaqus finite element simulation software based on the structural and material parameters of the welded joint workpiece. Then, according to the welding process parameters, a moving welding heat source is applied using a double ellipsoidal heat source model. Creep constitutive models for the heat treatment process and the service process are written using the CREEP and USDFLD subroutines. These subroutines are embedded into the Abaqus finite element software for secondary development. Simultaneously, relevant process parameters and boundary conditions for heat treatment and service simulations are set in the finite element software to obtain an integrated welding-heat treatment-service finite element simulation model. Simulations are performed using this integrated model, with a service stress of 18.9 MPa and a service temperature of 474°C, ending after 1 million hours of service. The simulation results are as follows: Figure 6 As shown, the maximum Mises stress is 174 MPa, the cumulative creep strain is 1.728%, and the maximum creep damage is 0.63.

[0128] The criteria for judging creep failure of the narrow gap welded joint of the hydrogenation reactor shell in this embodiment are as follows: when the cumulative creep damage at the dangerous location of the welded joint reaches the creep damage critical value (0.5 in this embodiment), creep failure is judged to have occurred, and the corresponding service time is the creep life; if the service time reaches 1 million hours and the cumulative creep damage has not reached the above critical value, then 1 million hours is taken as the creep life of the welded joint.

[0129] In the simulation results above, under the stated service conditions, the cumulative creep damage at the welded joint increases over time. When the service time reaches 897,000 hours, the creep damage reaches the critical value of 0.5, indicating creep failure. Continuing service to 1 million hours, the creep damage increases to 0.63. Therefore, the creep life of this welded joint is determined to be 897,000 hours.

[0130] Comparative Example 1

[0131] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 uses the Omega creep constitutive model when simulating creep damage during heat treatment and service.

[0132] Simulation calculations show that when the creep life reaches 505,000 hours, the creep damage reaches a critical value of 0.5, indicating creep failure. Simulation results for a continued service life of 1 million hours are as follows... Figure 7 As shown, its creep damage increased to 0.81. In this comparative example, the predicted creep life of the welded joint was determined to be 505,000 hours.

[0133] Comparative Example 2

[0134] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 adopts the static initial condition method, that is, the welding and heat treatment process is simulated first, and then the "static" residual stress field after the heat treatment is completed is used as the initial stress state for the creep damage simulation during service.

[0135] Simulation results obtained after 1 million hours of service life are as follows: Figure 8 As shown, the creep damage obtained in this comparative example is 0.49, and the creep life prediction value of the welded joint in this comparative example is 1 million hours.

[0136] Comparing the simulation results of Example 1, Comparative Example 1, and Comparative Example 2 above, compared with Example 1, the creep damage value of Comparative Example 1 is larger, and the creep damage value of Comparative Example 2 is smaller.

[0137] In addition, creep damage simulations under high temperature (450℃) and high stress (300MPa, 400MPa, 500MPa) were conducted using the methods of Example 1, Comparative Example 1, and Comparative Example 2, respectively. The time when the cumulative creep damage of the welded joint reached 0.5 was used as the predicted creep life of the joint. Simultaneously, uniaxial creep tensile tests were conducted on welded joint samples under high temperature (450℃) and high stress (300MPa, 400MPa, 500MPa) to obtain the experimental creep life values. The predicted and experimental results are shown in Table 2 below.

[0138] Table 2. Results of creep damage simulation and creep experiment

[0139]

[0140] As can be seen from Table 2 above, the error between the predicted creep life value and the experimental value in Example 1 is about 5%, which is small and the prediction accuracy is high. However, in Comparative Example 1, the Omega creep constitutive model was used to simulate the heat treatment process, which is not accurate in characterizing the evolution of residual stress during the heat treatment stage and lacks consideration of the first and second stages of creep. Therefore, the predicted life is smaller than the actual value by more than 20%. In Comparative Example 2, although the residual stress after actual heat treatment was considered, the influence of other historical parameters (such as creep strain) was ignored, resulting in a predicted life that is larger than the actual value by more than 10%. These comparison results also verify the accuracy of the prediction method of this invention.

[0141] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0142] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for predicting creep life across all stages by coupling residual stress and creep damage, characterized in that, Including the following steps: S1. In the finite element simulation software, a finite element model is established based on the structural and material parameters of the welded workpiece. The welding moving heat source model and boundary conditions are applied to simulate the welding process and obtain the welding residual stress distribution data. S2. Considering the influence of varying temperature and stress on creep damage of welded workpieces during heat treatment, establish a creep constitutive model for the heat treatment process. Based on the welding residual stress distribution data obtained in step S1, simulate the stress release damage of the welded workpiece after post-weld heat treatment and obtain the stress and strain distribution data after heat treatment as historical parameters for subsequent service of the welded workpiece. S3. Considering the influence of load on creep damage of welded workpiece during service, establish a creep constitutive model for service process, and simulate creep damage of welded workpiece during service process based on the stress and strain distribution data after heat treatment obtained in step S2, and obtain creep damage during service process. S4. Set the criteria for judging creep failure of the welded workpiece, and compare and analyze the cumulative creep damage obtained in step S3 during the service process with the criteria for judging creep failure to determine the creep life of the welded workpiece. The service process creep constitutive model established in step S3 is as follows: （3-1）； （3-2）； ； （3-3）； （3-4）； （3-5）； （3-6）； （3-7）； （3-8）； （3-9）； （3-10）； （3-11）； In the formula, For creep strain rate, The initial creep strain rate is based on the stress and temperature after heat treatment. This represents the cumulative amount of creep damage. For creep damage rate, ~ and ~ The creep damage coefficient of the welded workpiece material. , , , , , Parameters were calculated for the Omega creep damage model process. These are the input parameters for the Omega creep damage model. For equivalent stress, , , It is a triaxial principal stress. For time, For temperature; In step S3, when simulating creep damage during the service process of the welded workpiece, the initial creep stress during the service process is the sum of the stress after the load is applied and the stress after heat treatment, and the initial creep strain during the service process is the cumulative creep strain during the heat treatment process.

2. The method for predicting the full-stage creep life by coupling residual stress and creep damage according to claim 1, characterized in that, In step S1, the welding moving heat source model adopts one of the following: Rosonthal analytical heat source model, Gaussian heat source model, hemispherical heat source model, ellipsoidal heat source model, or double ellipsoidal heat source model.

3. The method for predicting the full-stage creep life by coupling residual stress and creep damage according to claim 1, characterized in that, The creep constitutive model for the heat treatment process established in step S2 is as follows: （2-1）； In the formula, For creep strain rate, For equivalent stress, Deformation activation energy, This is the universal gas constant. For temperature, Absolute temperature , , These are parameters related to the material.

4. The method for predicting the full-stage creep life by coupling residual stress and creep damage according to claim 3, characterized in that, The parameters in step S2 , The data was obtained through a fitting method, and the fitting process is as follows: (1) The creep constitutive model of the heat treatment process established in step S2 Expanded using Taylor series: （2-2）； At low stress levels, Approximately The relationship between strain rate, temperature, and stress is described by a power-law equation, transforming the creep constitutive model of the heat treatment process into: （2-3）； Under high stress levels, Approximately The relationship between strain rate, temperature, and stress is described by an exponential equation, transforming the creep constitutive model of the heat treatment process into: （2-4）； In the formula, Refers to low stress level , High stress level , , , , The equivalent stress index is obtained by approximating it using a power-law equation or an exponential equation. For natural numbers, ; (2) Taking the logarithm of both sides of formulas (2-1), (2-3), and (2-4), we get: （2-5）； （2-6）； （2-7）； (3) Test at least three sets of creep curves under different stresses at the same temperature, and plot them respectively. , , The scatter plots were generated, and linear fitting was performed on each plot. Based on the slope of the fitted curves, the following can be obtained: , , and according to get .

5. The method for predicting the full-stage creep life by coupling residual stress and creep damage according to claim 1, characterized in that, The criteria for determining creep failure in step S4 are as follows: When the cumulative creep damage at a certain point or section on a welded workpiece reaches the creep damage critical value at a certain moment, the welded workpiece is determined to have creep failure, and the corresponding time is the creep life of the welded workpiece. Alternatively, if the service life reaches 1 million hours but the cumulative creep damage of the welded workpiece is still less than the creep damage critical value, then 1 million hours shall be taken as the creep life of the welded workpiece.

6. A method for predicting the full-stage creep life by coupling residual stress and creep damage according to any one of claims 1-5, characterized in that, The creep constitutive models for the heat treatment process in step S2 and the service process in step S3 are written using CREEP and USDFLD subroutines, respectively. Both CREEP and USDFLD subroutines include subroutine interfaces and script interfaces to enable the switching of creep constitutive models for the heat treatment and service processes and the transfer of various parameters. The CREEP and USDFLD subroutines are then embedded into finite element software for secondary development to obtain an integrated finite element simulation model for welding-heat treatment-service.

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