Welding deformation prediction method for welded structure based on equivalent load

Abstract

The application discloses a welding deformation prediction method for a welded structure based on equivalent load. The welding deformation prediction method comprises the following steps: for a target welded structure, a finite element model of a small-size welded structure is constructed as a research object; for the finite element model of the research object, thermal elastic-plastic simulation is carried out to extract inherent strain data of a cross section of a weld steady-state region in the finite element model of the research object; the transverse equivalent distribution bending moment and the longitudinal equivalent concentrated bending moment of the weld are calculated; the transverse equivalent distribution bending moment and the longitudinal equivalent concentrated bending moment are applied to the target welded structure, and a model control equation and boundary conditions for the target welded structure are established based on the plate deformation theory. In the welding deformation prediction method, the transverse equivalent distribution bending moment and the longitudinal equivalent concentrated bending moment of the weld region of the target welded structure are obtained according to the thermal elastic-plastic simulation of the small-size welded structure, the analytical solution of the welding deformation is realized, and therefore the welding deformation prediction efficiency of the welded structure is greatly improved.

Description

Technical Field

[0001] The present invention relates to a welding deformation prediction method, in particular to a welding deformation prediction method for a welded structure based on equivalent load. Background Art

[0002] Aerospace structural components are large and difficult to manufacture in a single step, so they are often assembled using welding. Large welded structures have weak rigidity, and localized thermal contraction during welding directly leads to complex deformations such as bending and warping in the overall structure, severely impacting the dimensional accuracy and service life of aerospace products. Therefore, rapid and accurate prediction of welding deformation is crucial for efficient and high-precision manufacturing of large welded assemblies.

[0003] Relevant technologies for predicting welding deformation already exist in the existing technology. For example, the Chinese patent (application number: 202310192522.5) "A method for predicting deformation of plate butt welding based on inherent strain method" simulates the welding process of plates of different thicknesses and establishes a correlation between plate thickness and welding inherent strain, thereby realizing rapid prediction of welding deformation.

[0004] The current problem is:

[0005] Traditional thermoelastic-plastic simulation methods are computationally intensive, exponentially increasing the simulation time cost for large structures. This hinders the efficient prediction and precise control of welding deformation. For example, the previously mentioned "A Method for Predicting Deformation in Plate Butt Welding Based on the Intrinsic Strain Method" requires a large amount of pre-trained simulation data and fails to consider the impact of welding process parameters on the inherent strain, limiting its application scenarios. Summary of the Invention

[0006] The object of the present invention is to provide a method for predicting welding deformation of a welded structure based on equivalent load, which realizes efficient prediction of welding deformation of a welded structure.

[0007] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] A method for predicting welding deformation of a welded structure based on equivalent load, the method comprising:

[0009] S1, for the target welded structure, a finite element model of a small-sized welded structure is constructed as the research target finite element model;

[0010] S2, conduct thermo-elastoplastic simulation on the finite element model of the research object to extract the inherent strain data of the cross section of the weld steady-state area in the finite element model of the research object;

[0011] S3, calculating the transverse equivalent distributed bending moment and the longitudinal equivalent concentrated bending moment of the weld based on the inherent strain data;

[0012] S4, applying a transverse equivalent distributed bending moment and a longitudinal equivalent concentrated bending moment to the target welded structure, and then establishing a model control equation and boundary conditions for the target welded structure based on plate deformation theory;

[0013] S5, based on the generalized work reciprocity theorem and through the deformation solution of the virtual plate model, the deformation solution of the object welded structure is derived.

[0014] Furthermore, the length of the small-size welding structure is set to be more than 20 times the thickness of the small-size welding structure, and the width of the small-size welding structure is set to be more than 15 times the thickness of the small-size welding structure.

[0015] Furthermore, the establishment of the finite element model of the research object includes finite element meshing, material property setting, boundary condition setting, analysis step setting and heat source model application;

[0016] The finite element meshing adopts three-dimensional solid elements, adopts a smaller encrypted mesh near the weld area, and adopts a larger sparse mesh away from the weld area;

[0017] The material properties include mechanical performance parameters and thermophysical performance parameters;

[0018] The mechanical performance parameters include elastic modulus, Poisson's ratio and yield stress;

[0019] The thermophysical performance parameters include thermal conductivity, thermal expansion coefficient, density and specific heat;

[0020] The boundary conditions are displacement constraints on the bottom surface of the finite element model along three directions;

[0021] The analysis step is a temperature-displacement coupling analysis step;

[0022] The heat source model adopts a heat source model that matches the actual welding method.

[0023] Furthermore, the inherent strain data of the cross section of the weld steady-state region remains stable and does not fluctuate significantly with time or welding direction coordinates; the distance between the weld steady-state region and the weld starting point, and the distance between the weld steady-state region and the weld ending point, are both at least 100 mm;

[0024] The inherent strain data includes a transverse inherent strain component and a longitudinal inherent strain component, wherein,

[0025] The transverse inherent strain component is parallel to the workpiece surface and perpendicular to the direction of the weld.

[0026] The longitudinal inherent strain component is in a direction parallel to the weld.

[0027] Furthermore, the transverse equivalent distributed bending moment is obtained by integrating the transverse inherent strain component, and the longitudinal equivalent concentrated bending moment is obtained by integrating the longitudinal inherent strain component;

[0028] The calculation formula of the transverse equivalent distributed bending moment is:

[0029]

[0030] Where m x is the equivalent distributed bending moment in the transverse direction, E is the elastic modulus, is the transverse inherent strain component, z is the spatial coordinate perpendicular to the workpiece surface, h is the workpiece thickness, and A is the cross-sectional area of ​​the weld;

[0031] The calculation formula of the longitudinal equivalent concentrated bending moment is:

[0032]

[0033] Among them, M y is the longitudinal equivalent concentrated bending moment, is the longitudinal inherent strain component.

[0034] Furthermore, the plate deformation theory adopts Kirchhoff thin plate deformation theory;

[0035] The expression of the control equation of the model is:

[0036]

[0037] Where w is the deformation solution of the target weld structure, x is the transverse coordinate, y is the longitudinal coordinate, ν is the Poisson's ratio, and D = Eh 3 / 12(1-ν) is the bending stiffness, δ x1 , δ x2 , δ y1 , δ y2 is the Dirac function that characterizes the position of the equivalent load;

[0038] The boundary condition expression is:

[0039]

[0040] Where a is the width of the target weld structure, and b is the length of the target weld structure.

[0041] Furthermore, the virtual plate model is a Kirchhoff plate model subject to simple loads and simple constraints, and its geometric dimensions and material parameters are the same as those of the object welding structure;

[0042] The simple loads include unit force loads and uniform pressure loads, and the simple constraints include four-side fixed constraints and four-side simply supported constraints.

[0043] Furthermore, the target welded structure is a large welded structure with a length-to-thickness ratio or a width-to-thickness ratio greater than 10.

[0044] Compared with the prior art, the welding deformation prediction method of the present invention has the following advantages:

[0045] Taking advantage of the fact that the inherent strain of the cross section of the steady-state area of ​​the small-sized welded structure is the same as that of the target welded structure, the transverse equivalent distributed bending moment and the longitudinal equivalent concentrated bending moment of the weld area of ​​the target welded structure are obtained according to the thermo-elastoplastic simulation of the small-sized welded structure, and the analytical solution of the welding deformation is realized, thereby greatly improving the welding deformation prediction efficiency of the welded structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the flow of the method for predicting welding deformation of a welded structure based on equivalent load of the present invention;

[0047] Figure 2 Schematic diagram of calculation of equivalent lateral distributed bending moment in an embodiment of the present invention;

[0048] Figure 3 Schematic diagram of calculation of longitudinal equivalent concentrated bending moment in an embodiment of the present invention;

[0049] Figure 4 This is a schematic diagram of a large welded structural plate model in an embodiment of the present invention;

[0050] Figure 5 is a schematic diagram of a virtual board model in an embodiment of the present invention;

[0051] Figure 6 This is a deformation cloud diagram of a large-scale welded structure solved in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The present invention will be further described below with specific embodiments:

[0053] This embodiment provides a welding deformation prediction method for a welded structure based on equivalent load. The welding deformation prediction method can realize the welding deformation prediction of the welded structure, especially for large welded structures, and can effectively improve the welding deformation prediction efficiency.

[0054] It should be noted that the term "large welded structure" refers to a welded structure with a length or width exceeding 1 meter. Such large welded structures are typically used as load-bearing structural components in aerospace products, such as fuselage structures and rocket fuel tanks. The welding deformation prediction method of this embodiment is particularly suitable for large welded structures with a length-to-thickness ratio or a width-to-thickness ratio greater than 10.

[0055] For the convenience of accurate description, in this article, the “welded structure as the target of the welding deformation prediction method” is referred to as the “target welded structure”.

[0056] In this embodiment, the target welded structure is constructed by friction stir welding.

[0057] See also Figure 1 The welding deformation prediction method of this embodiment includes steps S1 to S5.

[0058] S1, for the target welded structure, a finite element model of a small-sized welded structure is constructed.

[0059] Specifically, the finite element model is established according to the geometric dimensions and welding process parameters of the target welding structure.

[0060] It should be noted that the small-sized welded structure refers to a welded structure that is identical to a small portion of the target welded structure. It is representative to a certain extent and can represent the overall welding performance of the target welded structure.

[0061] In this embodiment, the thickness of the small-sized welding structure is consistent with that of the target welding structure, and the length and width of the small-sized welding structure are determined according to the thickness of the small-sized welding structure.

[0062] Specifically,

[0063] The "length of the small-size welded structure" is set to be at least 20 times the "thickness of the small-size welded structure". In other words, the "thickness of the small-size welded structure" is "less than 1 / 20 of the length of the small-size welded structure";

[0064] The “width of the small-size welded structure” is set to be more than 15 times the “thickness of the small-size welded structure”, that is, the “thickness of the small-size welded structure” is “less than 1 / 15 of the width of the small-size welded structure”.

[0065] It should be noted that the establishment of the finite element model includes finite element mesh division, material property setting, boundary condition setting, analysis step setting and heat source model application.

[0066] More specifically,

[0067] The finite element mesh adopts three-dimensional solid elements; a smaller encrypted mesh is used near the weld area, and a larger sparse mesh is used far away from the weld area;

[0068] The material properties include mechanical performance parameters and thermophysical performance parameters,

[0069] The mechanical performance parameters include elastic modulus, Poisson's ratio and yield stress,

[0070] The thermophysical performance parameters include thermal conductivity, thermal expansion coefficient, density and specific heat;

[0071] The boundary conditions are displacement constraints on the bottom surface of the finite element model along three directions;

[0072] The analysis step is a temperature-displacement coupling analysis step;

[0073] The heat source model adopts a heat source model that matches the actual welding method.

[0074] For the convenience of description, the constructed “finite element model of small-size welded structure” is referred to as the “finite element model of the research object”.

[0075] It should be noted that

[0076] The “geometric dimensions of the subject welded structure” mentioned above include the length, width and thickness of the subject welded structure;

[0077] The aforementioned “welding process parameters of the target weld structure” include welding method, welding heat input, welding feed speed and welding rotation speed.

[0078] S2, performing a thermo-elasto-plastic simulation on the finite element model of the research object constructed in step S1 to extract inherent strain data of a cross section of a weld in a steady-state region in the finite element model of the research object.

[0079] In this embodiment, the inherent strain data of the cross-section of the steady-state region of the weld remains stable, that is, it does not fluctuate significantly with time or welding direction coordinates; "the distance between the steady-state region of the weld and the starting point of the weld" and "the distance between the steady-state region of the weld and the ending point of the weld" are both at least 100 mm.

[0080] The inherent strain data includes a transverse inherent strain component and a longitudinal inherent strain component, wherein,

[0081] The transverse inherent strain component is in the direction parallel to the workpiece surface and perpendicular to the direction of the weld.

[0082] The longitudinal inherent strain component is in the direction parallel to the weld seam.

[0083] S3, based on the "inherent strain data of the cross section of the weld in the steady-state region in the finite element model of the research object" obtained in step S2, calculate the transverse equivalent distributed bending moment and the longitudinal equivalent concentrated bending moment of the weld.

[0084] The transverse equivalent distributed bending moment is obtained by integrating the transverse inherent strain component, and the longitudinal equivalent concentrated bending moment is obtained by integrating the longitudinal inherent strain component.

[0085] Specifically,

[0086] The calculation formula of the transverse equivalent distributed bending moment is:

[0087]

[0088] Where m x is the equivalent distributed bending moment in the transverse direction, E is the elastic modulus, is the transverse inherent strain component, z is the spatial coordinate perpendicular to the workpiece surface, h is the workpiece thickness, and A is the cross-sectional area of ​​the weld.

[0089] The calculation formula of the longitudinal equivalent concentrated bending moment is:

[0090]

[0091] Among them, M y is the longitudinal equivalent concentrated bending moment, is the longitudinal inherent strain component.

[0092] It should be noted that

[0093] The transverse equivalent distributed bending moment comprises a pair of distributed bending moments of equal value and opposite direction, acting at the boundary of the weld width;

[0094] The longitudinal equivalent concentrated bending moment includes a pair of concentrated bending moments of equal value and opposite direction, which act at the starting point and the ending point of the weld.

[0095] S4, applying the transverse equivalent distributed bending moment and the longitudinal equivalent concentrated bending moment obtained in step S3 to the target welded structure, and then establishing a model control equation and boundary conditions for the target welded structure based on plate deformation theory.

[0096] In this embodiment,

[0097] The plate deformation theory adopted is Kirchhoff thin plate deformation theory;

[0098] The expression of the control equation of the model is:

[0099]

[0100] Where w is the deformation solution of the target weld structure, x is the transverse coordinate, y is the longitudinal coordinate, ν is the Poisson's ratio, and D = Eh 3 / 12(1-ν) is the bending stiffness, δ x1 , δ x2 , δ y1 , δ y2 is the Dirac function that characterizes the position of the equivalent load;

[0101] The boundary condition expression is:

[0102]

[0103] Wherein, a is the width of the target weld structure, and b is the length of the target weld structure.

[0104] S5, based on the generalized work reciprocity theorem, the deformation solution of the object welded structure is indirectly derived through the deformation solution of the virtual plate model.

[0105] It should be noted that

[0106] The virtual plate model is a Kirchhoff plate model subject to simple loads and simple constraints, and its geometric dimensions and material parameters are the same as those of the object welding structure;

[0107] The simple loads include unit force loads and uniform pressure loads;

[0108] The simple constraints include four-side fixed constraints and four-side simply supported constraints.

[0109] It should be noted that

[0110] The generalized reciprocal work theorem is applicable to two different linear elastic bodies with different loads, different static boundary conditions, and different displacement boundary conditions;

[0111] For the two different linear elastic bodies, by applying the generalized work equivalence theorem between the former and the latter, the deformation solution of the latter can be indirectly derived based on the deformation solution of the former.

[0112] Based on the generalized work reciprocity theorem, the deformation solution of the target welded structure can be derived from the deformation solution of the virtual plate model, and its expression is:

[0113]

[0114] Among them, w0 is the deformation solution of the virtual plate model.

[0115] The main advantages of the welding deformation prediction method of this embodiment are:

[0116] In the welding deformation prediction method of this embodiment, the characteristic that the small-sized welding structure and the object welding structure have the same inherent strain in the cross section of the steady-state area is utilized. According to the thermo-elastoplastic simulation of the small-sized welding structure, the transverse equivalent distributed bending moment and the longitudinal equivalent concentrated bending moment of the weld area of ​​the object welding structure are obtained, and the analytical solution of the welding deformation is realized, which greatly improves the welding deformation prediction efficiency of the welding structure.

[0117] Specifically, in the welding deformation prediction method of this embodiment, the inherent strain data of the target welding structure is indirectly obtained through the thermo-elastoplastic simulation of the small-scale welding structure, which simplifies the method of obtaining the inherent strain and ensures the calculation accuracy of the inherent strain; the inherent strain component is equivalent to the corresponding bending moment load, and the complex welding deformation problem is converted into a plate deformation problem with a mechanical theory solution; using the generalized work equivalence theorem, by establishing a virtual plate model with simple loads and simple constraints, the complex deformation solution of the target welding structure is indirectly derived, thereby realizing rapid and accurate prediction of welding deformation, which is particularly significant for the efficiency improvement of large-scale welding structures.

[0118] A practical example is provided below. In this example, the welding deformation prediction method of the present invention is used to predict the welding deformation of a large welded structure.

[0119] See also Figures 1 to 6 ,

[0120] (Corresponding to step S1) establishing a finite element model of the small-sized welded structure (i.e., the research object finite element model) based on the geometric dimensions and welding process parameters of the large-sized welded structure (i.e., the research object finite element model);

[0121] The large welded structures were constructed from 2024-T351 aluminum alloy, with dimensions of 1000 × 150 × 18 mm, 1000 × 450 × 18 mm, and 1000 × 600 × 18 mm (length × width × thickness). Friction stir welding was used, with a 32 mm diameter stir head, a 10 mm diameter spindle, and a 17.5 mm length. The welding feed rate was 100 mm / min, and the rotational speed was 300 rpm.

[0122] A finite element model of a small-scale welded structure was created in Abaqus. The material was aluminum alloy 2024-T351, with geometric dimensions of 400 × 150 × 18 mm. The heat source for friction stir welding was defined by the user subroutine DFLUX and included a surface heat source and a cylindrical heat source.

[0123] The finite element model of the small-scale welded structure (i.e., the finite element model of the research object) was meshed using the eight-node three-dimensional solid element C3D8T. The element size in the center of the weld was small, while the element size in areas away from the weld was appropriately increased. Mechanical and thermophysical properties were assigned to the finite element model of the small-scale welded structure, including elastic modulus, Poisson's ratio, yield stress, thermal conductivity, thermal expansion coefficient, density, and specific heat. Displacement constraints were applied to the bottom surface of the model in three directions to simulate the constraints of the backing plate and fixture.

[0124] (Corresponding to step S2) performing a thermo-elastic-plastic simulation of a finite element model of a small-scale welded structure to extract inherent strain data of a cross section of a weld in a steady-state region;

[0125] A thermoelastic-plastic analysis of a small-scale welded structure finite element model was performed using a temperature-displacement coupled analysis step, encompassing both the welding and cooling stages. After the cooling stage, the transverse and longitudinal inherent strain components were extracted from the central cross-section of the small-scale welded structure finite element model.

[0126] (Corresponding to step S3) calculating the transverse equivalent distributed bending moment and the longitudinal equivalent concentrated bending moment of the weld based on the inherent strain of the finite element model of the small-scale welded structure;

[0127] The transverse equivalent distributed bending moment is calculated by integrating the transverse natural strain component on the central cross section:

[0128]

[0129] Among them, m x is the equivalent distributed bending moment in the transverse direction, E is the elastic modulus, is the transverse inherent strain component, z is the spatial coordinate perpendicular to the workpiece surface, h is the workpiece thickness, and A is the cross-sectional area of ​​the weld.

[0130] Integrate the longitudinal natural strain component on the central cross section to calculate the longitudinal equivalent concentrated bending moment:

[0131]

[0132] Among them, M y is the longitudinal equivalent distributed bending moment, is the longitudinal inherent strain component.

[0133] See also Figure 2 and Figure 3 The transverse equivalent distributed bending moment includes a pair of distributed bending moments with equal values ​​and opposite directions, acting at the width boundary of the weld. The longitudinal equivalent concentrated bending moment includes a pair of concentrated bending moments with equal values ​​and opposite directions, acting at the starting and ending points of the weld.

[0134] (Corresponding to step S4) applying an equivalent bending moment to the large welded structure, and establishing the model control equations and boundary conditions based on plate deformation theory;

[0135] See also Figure 4 The large welded structure is equivalent to a Kirchhoff plate model subjected to transverse distributed bending moment and longitudinal concentrated bending moment. In order to minimize the influence of boundary constraints on the deformation results, the boundary conditions of simply supported four corner points are adopted.

[0136] The expressions of the simply supported boundary conditions at the four corner points are:

[0137]

[0138] Where w is the deformation solution of the large welded structure, x is the horizontal coordinate, y is the vertical coordinate, a and b are the width and length of the large welded structure respectively, D = Eh 3 / 12(1-ν) is the bending stiffness, and ν is the Poisson's ratio.

[0139] (Corresponding to step S5) Based on the generalized work reciprocity theorem, the deformation solution of the large welded structure is indirectly derived through the deformation solution of the virtual plate model.

[0140] The generalized reciprocity of work theorem states that for two linear elastic bodies with different loads, different static boundary conditions, and different displacement boundary conditions, the work done by the former load on the latter displacement is equal to the work done by the latter load on the former displacement.

[0141] Based on the generalized work reciprocity theorem, the deformation solution of large welded structures can be indirectly derived from the deformation solution of the virtual plate model. Figure 5 ,The virtual plate model adopts the Kirchhoff plate model subject to unit force load and four simply supported ,sides. Its geometric dimensions and material parameters are the same as the ,large welded structure.

[0142] The governing equations of the virtual plate model are:

[0143]

[0144] Where w0 is the deformation solution of the virtual plate model, δ is the Dirac function, and ξ and η are the position coordinates of the unit force load.

[0145] The boundary conditions of the virtual plate model are:

[0146]

[0147] By expanding the Dirac function and the deformation solution into a double trigonometric series and substituting it into the governing equations and boundary equations of the virtual plate model, the deformation solution of the virtual plate model can be obtained:

[0148]

[0149] in, α m =mπ / a,β n =nπ / b.

[0150] By applying the generalized work reciprocity theorem between the large welded structure and the virtual plate model, the deformation solution of the large welded structure can be obtained, which is expressed as:

[0151]

[0152] Among them, Q x and Q y is the shear force on the virtual plate model at the boundary, which can be calculated by the following formula:

[0153]

[0154] See also Figure 6 , the figure shows the deformation solution of the large welded structure obtained.

[0155] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for predicting welding deformation of welded structures based on equivalent load, characterized by: The welding deformation prediction method comprises: S1, for the target welded structure, a finite element model of a small-sized welded structure is constructed as the research target finite element model; S2, conduct thermo-elastoplastic simulation on the finite element model of the research object to extract the inherent strain data of the cross section of the weld steady-state area in the finite element model of the research object; S3, calculating the transverse equivalent distributed bending moment and the longitudinal equivalent concentrated bending moment of the weld based on the inherent strain data; S4, applying a transverse equivalent distributed bending moment and a longitudinal equivalent concentrated bending moment to the target welded structure, and then establishing a model control equation and boundary conditions for the target welded structure based on plate deformation theory; S5, based on the generalized work reciprocity theorem and through the deformation solution of the virtual plate model, the deformation solution of the object welded structure is derived; The inherent strain data of the cross section of the weld steady-state region remains stable and does not fluctuate significantly with time or welding direction coordinates; the distance between the weld steady-state region and the weld starting point, and the distance between the weld steady-state region and the weld ending point, are both at least 100 mm; The inherent strain data includes a transverse inherent strain component and a longitudinal inherent strain component, wherein, The transverse inherent strain component is parallel to the workpiece surface and perpendicular to the direction of the weld. The longitudinal inherent strain component is in a direction parallel to the weld; The transverse equivalent distributed bending moment is obtained by integrating the transverse inherent strain component, and the longitudinal equivalent concentrated bending moment is obtained by integrating the longitudinal inherent strain component; The calculation formula of the transverse equivalent distributed bending moment is: Where m x is the equivalent distributed bending moment in the transverse direction, E is the elastic modulus, is the transverse inherent strain component, z is the spatial coordinate perpendicular to the workpiece surface, h is the workpiece thickness, and A is the cross-sectional area of ​​the weld; The calculation formula of the longitudinal equivalent concentrated bending moment is: Among them, M y is the longitudinal equivalent concentrated bending moment, is the longitudinal inherent strain component; The plate deformation theory adopts Kirchhoff thin plate deformation theory; The expression of the control equation of the model is: Where w is the deformation solution of the target weld structure, x is the transverse coordinate, y is the longitudinal coordinate, ν is the Poisson's ratio, and D = Eh 3 / 12(1-ν) is the bending stiffness, δ x1 , δ x2 , δ y1 , δ y2 is the Dirac function that characterizes the position of the equivalent load; The boundary condition expression is: (In) x＝0,y＝0 =(in) x＝a,y＝0 =(in) x＝0,y＝b =(in) x＝a,y＝b =0 Where a is the width of the target weld structure, and b is the length of the target weld structure.

2. The method for predicting welding deformation of a welded structure based on equivalent load according to claim 1, characterized in that: The length of the small-size welding structure is set to be more than 20 times the thickness of the small-size welding structure, and the width of the small-size welding structure is set to be more than 15 times the thickness of the small-size welding structure.

3. The method for predicting welding deformation of a welded structure based on equivalent load according to claim 1, characterized in that: The establishment of the finite element model of the research object includes finite element mesh division, material property setting, boundary condition setting, analysis step setting and heat source model application; The finite element meshing adopts three-dimensional solid elements, adopts a smaller encrypted mesh near the weld area, and adopts a larger sparse mesh away from the weld area; The material properties include mechanical performance parameters and thermophysical performance parameters; The mechanical performance parameters include elastic modulus, Poisson's ratio and yield stress; The thermophysical performance parameters include thermal conductivity, thermal expansion coefficient, density and specific heat; The boundary conditions are displacement constraints on the bottom surface of the finite element model along three directions; The analysis step is a temperature-displacement coupling analysis step; The heat source model adopts a heat source model that matches the actual welding method.

4. The method for predicting welding deformation of a welded structure based on equivalent load according to claim 1, characterized in that: The virtual plate model is a Kirchhoff plate model subject to simple loads and simple constraints, and its geometric dimensions and material parameters are the same as those of the object welding structure; The simple loads include unit force loads and uniform pressure loads, and the simple constraints include four-side fixed constraints and four-side simply supported constraints.

5. The method for predicting welding deformation of a welded structure based on equivalent load according to claim 1, characterized in that: The target welded structure is a large welded structure with a length-to-thickness ratio or a width-to-thickness ratio greater than 10.

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