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CN-121997681-A - Full-stage creep life prediction method for coupling residual stress and creep damage

CN121997681ACN 121997681 ACN121997681 ACN 121997681ACN-121997681-A

Abstract

The invention 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 steps of establishing a finite element model of a welding workpiece and performing welding process simulation to obtain welding residual stress distribution data, establishing a creep constitutive model in the heat treatment process, performing post-welding heat treatment stress release damage simulation on the welding workpiece on the basis of the welding residual stress distribution data to obtain stress and strain distribution data after heat treatment as historical parameters of service of the subsequent welding workpiece, performing creep damage simulation on the welding workpiece in the service process on the basis of the stress and strain distribution data after heat treatment to obtain creep damage in the service process, setting a judgment basis for creep failure of the welding workpiece, and determining the creep life of the welding workpiece. The invention can realize the physical continuity of the internal state evolution of the material from welding manufacture to service, and accurately simulate creep damage in the service process.

Inventors

  • YANG BIN
  • GUO ZHIWEI
  • JIANG WENCHUN

Assignees

  • 中国石油大学(华东)

Dates

Publication Date
20260508
Application Date
20260410

Claims (9)

  1. 1. A full-stage creep life prediction method for coupling residual stress and creep damage is characterized by comprising the following steps: S1, establishing a finite element model based on structural parameters and material parameters of a welding workpiece in finite element simulation software, applying a welding mobile heat source model and boundary conditions, and performing welding process simulation to obtain welding residual stress distribution data; S2, establishing a creep constitutive model of the heat treatment process by considering the influences of variable temperature and variable stress in the heat treatment process on creep damage of the welding workpiece, performing post-welding heat treatment stress release damage simulation on the welding workpiece on the basis of the welding residual stress distribution data obtained in the step S1, and obtaining stress and strain distribution data after heat treatment as historical parameters of service of the subsequent welding workpiece; S3, establishing a creep deformation constitutive model of the service process by considering the influence of the load in the service process on the creep damage of the welded workpiece, and performing creep damage simulation on the service process of the welded workpiece on the basis of the stress and strain distribution data obtained in the step S2 after the heat treatment to obtain the creep damage in the service process; s4, setting a judgment basis for creep failure of the welding workpiece, and comparing and analyzing the accumulated creep damage amount in the service process obtained in the step S3 with the creep failure judgment basis to determine the creep life of the welding workpiece.
  2. 2. The method for predicting the creep life of a full-stage coupling between residual stress and creep damage according to claim 1, wherein the welding moving heat source model in the step S1 is one of a Rosonthal analytic heat source model, a gaussian heat source model, a hemispherical heat source model, an ellipsoidal heat source model or a double-ellipsoid heat source model.
  3. 3. The method for predicting the creep life of a full-stage coupling between residual stress and creep damage according to claim 1, wherein the creep constitutive model of the heat treatment process established in the step S2 is: (2-1); in the formula, In order to achieve a creep strain rate, In order for the stress to be equivalent to, In order for the deformation to be activated, Is a gas constant which is a general purpose gas constant, In order to be able to determine the temperature, The temperature is set to be the absolute temperature, 、 、 Is a material related parameter.
  4. 4. The method for predicting creep life in all stages coupling residual stress and creep damage according to claim 3, wherein the parameters in step S2 are as follows 、 The method is characterized by comprising the following steps of: (1) Creep the heat treatment process established in the step S2 into the constitutive model The expansion is as follows according to the Taylor series: (2-2); at low stress levels, will Approximately as The relation among strain rate, temperature and stress is described in the form of a power law equation, and the creep constitutive model in the heat treatment process is converted into: (2-3); at high stress levels, will Approximately as Describing the relation among the strain rate, the temperature and the stress in the form of an exponential equation, and converting the creep constitutive model in the heat treatment process into: (2-4); in the formula, At a low stress level , At a high stress level , , , , To obtain an equivalent stress index using a power law equation or an exponential equation approximation, Is a natural number of the Chinese characters, ; (2) Taking the logarithm of the two sides of the formulas (2-1), (2-3) and (2-4) to obtain the following components: (2-5); (2-6); (2-7); (3) Testing at least three groups of creep curves under different stress at the same temperature, and respectively drawing 、 、 Respectively performing linear fitting, and obtaining according to the slope of the fitting curve 、 、 And according to Obtaining 。
  5. 5. The method for predicting creep life in all stages coupling residual stress and creep damage according to claim 4, wherein the parameters in step S2 are as follows 、 The method is characterized by comprising the following steps of: Obtaining parameters by fitting 、 Based on this, the formula (2-5) is changed to And (3) with Is the relation of (a), namely: (2-8); Then testing at least three groups of creep curves at different temperatures under the same creep strain rate, and drawing Performing linear fitting, obtaining according to slope and intercept of fitting curve 、 。
  6. 6. The method for predicting the creep life in all stages coupling residual stress and creep damage according to claim 1, wherein the service process creep constitutive model established in the step S3 is: (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, In order to achieve a creep strain rate, To provide an initial creep strain rate based on stress and temperature after heat treatment, To accumulate creep damage; In order to achieve a creep damage rate, ~ And ~ To weld the creep damage coefficients of the workpiece material, 、 、 、 、 、 Parameters were calculated for the Omega creep damage model process, Is an input parameter of the Omega creep damage model, In order for the stress to be equivalent to, 、 、 Is the three-dimensional principal stress, In order to be able to take time, Is the temperature.
  7. 7. The method for predicting the creep life in all stages of coupling residual stress and creep damage according to claim 1, wherein when the creep damage simulation is performed on the service process of the welded workpiece in the step S3, the initial creep stress in the service process is the sum of the stress after load application and the stress after heat treatment, and the initial creep strain in the service process is the accumulated creep strain amount in the heat treatment process.
  8. 8. The method for predicting creep life at all stages of coupling residual stress and creep damage according to claim 1, wherein the determining basis of creep failure in step S4 is as follows: When the accumulated creep damage amount of a certain point or a certain section on the welding workpiece at a certain moment reaches a creep damage critical value, judging that the welding workpiece has creep failure, wherein the corresponding time at the moment is the creep life of the welding workpiece; Or when the service time reaches 100 ten thousand hours and the accumulated creep damage amount of the welding workpiece is still smaller than the creep damage critical value, taking 100 ten thousand hours as the creep life of the welding workpiece.
  9. 9. The method for predicting the creep life at all stages, which is coupled with residual stress and creep damage according to any one of claims 1 to 8, wherein the creep constitutive model in the heat treatment process in the step S2 and the creep constitutive model in the service process in the step S3 are written through CREEP and USDFLD subprograms respectively, and the subprograms CREEP and USDFLD respectively comprise a subprogram interface and a script interface, so as to realize the switching of the creep constitutive models in the heat treatment process and the service process and the transfer of each parameter, and the subprograms CREEP and USDFLD are embedded into finite element software for secondary development to obtain the welding-heat treatment-service integrated finite element simulation model.

Description

Full-stage creep life prediction method for coupling residual stress and creep damage Technical Field The invention relates to the technical field of creep life prediction, in particular to a full-stage creep life prediction method for coupling residual stress and creep damage. Background Creep life prediction is important in the design and safety assessment of high temperature components of pressure vessels. Conventional creep life prediction methods are typically based on load and material data during service, while ignoring residual stresses generated during the manufacturing process (e.g., heat treatment, welding, forging) of the component and its evolution prior to service. In order to improve the accuracy of creep life prediction, a learner also researches the influence of residual stress on creep life at present, but the existing method for considering the influence of residual stress on creep life has the following limitations: (1) The empirical coefficient method is to simply equivalent residual stress to a safety coefficient or an influence factor, lacks a physical mechanism, and has low prediction precision and conservation; (2) The static initial condition method is to only take the static residual stress field after the heat treatment as the initial stress state of the service creep analysis, and the method ignores the dynamic relaxation history of the residual stress in the heat treatment process and key state variables such as accumulated creep strain and the like accompanied by the history; (3) And the equivalent initial rate method is to equivalent residual stress to initial creep rate, and break the continuity of damage development in the manufacturing stage and the service stage. The calculation and analysis process of the existing method is discontinuous, historical information is broken, and a complete damage evolution chain from manufacturing to service cannot be established, so that the actual influence of residual stress on creep life cannot be accurately represented, and the accuracy of life creep life prediction is affected. Disclosure of Invention In order to solve the technical problems in the prior art, the invention provides a full-stage creep life prediction method for coupling residual stress and creep damage. The invention adopts the technical scheme that: A full-stage creep life prediction method for coupling residual stress and creep damage comprises the following steps: S1, establishing a finite element model based on structural parameters and material parameters of a welding workpiece in finite element simulation software, applying a welding mobile heat source model and boundary conditions, and performing welding process simulation to obtain welding residual stress distribution data; S2, establishing a creep constitutive model of the heat treatment process by considering the influences of variable temperature and variable stress in the heat treatment process on creep damage of the welding workpiece, performing post-welding heat treatment stress release damage simulation on the welding workpiece on the basis of the welding residual stress distribution data obtained in the step S1, and obtaining stress and strain distribution data after heat treatment as historical parameters of service of the subsequent welding workpiece; S3, establishing a creep deformation constitutive model of the service process by considering the influence of the load in the service process on the creep damage of the welded workpiece, and performing creep damage simulation on the service process of the welded workpiece on the basis of the stress and strain distribution data obtained in the step S2 after the heat treatment to obtain the creep damage in the service process; s4, setting a judgment basis for creep failure of the welding workpiece, and comparing and analyzing the accumulated creep damage amount in the service process obtained in the step S3 with the creep failure judgment basis to determine the creep life of the welding workpiece. Further, in the step S1, the welding mobile heat source model adopts one of Rosonthal analytic heat source model, gaussian heat source model, hemispherical heat source model, ellipsoidal heat source model or double ellipsoidal heat source model. Further, the creep constitutive model of the heat treatment process established in the step S2 is as follows: (2-1); in the formula, In order to achieve a creep strain rate,In order for the stress to be equivalent to,In order for the deformation to be activated,Is a gas constant which is a general purpose gas constant,In order to be able to determine the temperature,The temperature is set to be the absolute temperature,、、Is a material related parameter. Further, the parameters in the step S2、The method is characterized by comprising the following steps of: (1) Creep the heat treatment process established in the step S2 into the constitutive model The expansion is as follows according to the Taylor series: (2-2); at low s