Crack propagation life analysis method of welded structures based on support vector machine model

Abstract

The present invention provides a method for analyzing the crack propagation life of a welded structure based on a support vector machine model. The method comprises the following steps: using hexahedral units to discretize a geometric model of a welded structure, generating a finite element model, and performing static simulation analysis; implanting an initial crack at the center of a weld, and re-dividing a sub-model grid containing the initial crack using tetrahedral units; obtaining a numerical solution of a stress intensity factor at a crack tip through finite element calculation under different values ​​of half-crack lengths, crack positions, and leading edge positions; obtaining an analytical solution using a stress intensity factor calculation formula, and calculating the difference between the numerical solution and the analytical solution; establishing a support vector machine regression model using the half-crack length, crack position, and leading edge position as inputs and the difference as output, and obtaining a stress intensity factor correction formula based on the stress intensity factor calculation formula; substituting the stress intensity factor correction formula into a Paris crack propagation formula to obtain a Paris correction formula, and predicting the fatigue life of the welded structure.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace computing, and in particular relates to a method for analyzing the crack propagation life of a welded structure based on a support vector machine model. Background Art

[0002] Fatigue is a significant factor affecting the service life of engineering components. During the manufacturing process, components inevitably develop initial defects, which are easily damaged when subjected to unstable loads, initiating initial cracks that, over time, can lead to component failure. Current spacecraft tank structures suffer from operational instability and complex service conditions. Research into structural life assessment technology is urgently needed to improve the design of my country's space transportation equipment and meet the demand for fatigue life prediction of tank structures in spacecraft during service.

[0003] Research on fracture mechanics began relatively late, focusing on components containing cracks. Fracture mechanics can quantitatively assess the fatigue life of components, providing theoretical guidance for engineering problems. Applying the principles of fracture mechanics to the analysis of fatigue crack growth and the estimation of component fatigue life is a key component of fracture mechanics research.

[0004] The classic formula used for fatigue crack growth is the Paris formula: In recent years, many methods for modifying the Paris formula have emerged. Most of the existing modifications to the Paris formula are aimed at modifying the formula expression, such as introducing the influence of component shape, considering closure effects, etc. These correction terms are added to the Paris formula in the form of multipliers or modifying the expression of the Paris formula. For example, Forman modified the Paris formula The fatigue crack growth formula is complex and variable, with limited applicability due to factors such as operating conditions and material properties. Finding a universal formula that can be widely applied across multiple scenarios is difficult. Furthermore, revising the Paris formula typically requires extensive physical testing to obtain crack growth data. However, physical testing of aerospace components is difficult, expensive, time-consuming, and prone to haphazardness. Using data from physical tests to refine the formula is costly and impractical. Therefore, developing an appropriate calculation model, combined with the Paris formula, to predict component fatigue life is of great academic and engineering value. Summary of the Invention

[0005] In view of the above problems, an embodiment of the present invention provides a method for analyzing the crack growth life of a welded structure based on a support vector machine model, which is used to improve the accuracy and efficiency of fatigue fracture life calculation of a welded structure.

[0006] An embodiment of the present invention provides a method for analyzing the crack growth life of a welded structure based on a support vector machine model, which includes the following steps:

[0007] Step 1: Use hexahedral elements to discretize the geometric model of the welded structure to obtain a finite element model, and perform static simulation analysis to obtain the node displacement and stress distribution calculation results;

[0008] Step 2: implanting an initial crack at the center of the weld of the finite element model, dividing the finite element model into a sub-model containing the initial crack and other partial models, re-discretizing the sub-model using tetrahedral elements, and performing encryption processing on the crack tip, while retaining hexahedral elements in the other partial models. The nodes of the contact surface between the sub-model and the other partial models are retained, and the node displacement of the contact surface is used as the boundary condition of the sub-model;

[0009] Step 3: Perform crack propagation finite element calculation on the sub-model to obtain the numerical solution K of the stress intensity factor at the crack tip under different values ​​of half crack length a, crack position d and front edge position λ. e ;

[0010] Step 4: Use the stress intensity factor calculation formula Calculate the analytical solution and calculate the numerical solution K e With the analytical solution K t The difference K * , K * =K e -K t ;

[0011] Step 5: Take the half crack length a, the crack position d and the leading edge position λ as input, and use the difference K * As the output, establish a support vector machine regression model And according to the stress intensity factor calculation formula Obtain the stress intensity factor correction formula

[0012] Step 6: Substitute the stress intensity factor correction formula K'(a, d, λ) into the Paris crack growth formula Get the Paris correction formula The structural residual strength criterion is selected as the criterion to obtain the fatigue life prediction value of the welded structure.

[0013] The method for analyzing the crack growth life of welded structures based on the support vector machine model provided by the embodiment of the present invention has the following advantages:

[0014] (1) In the embodiment of the present invention, a static analysis is performed on the overall finite element model of the structure to obtain the calculated results of its node displacement and stress distribution; a key area is selected, and the model of the area is cut to obtain a sub-model and other partial models; the node displacement at the intersection of the sub-model and the other partial models is extracted and used as boundary conditions for interpolation calculation; the aforementioned boundary conditions are applied to the sub-model, and finally the sub-model is solved. The above process uses a sub-model for local structural analysis. The overall finite element model of the structure is large in size and it is difficult to directly simulate small initial defects. It is often very limited when performing local analysis. The sub-model can realize refined analysis and boundary condition conversion between different units.

[0015] (2) The traditional crack propagation research method uses J-integral to calculate the numerical solution of the crack tip stress intensity factor. Compared with it, the embodiment of the present invention uses the interactive integration method, namely the M-integral method, to solve the stress intensity factor. The use of a symmetrical grid reduces the local discrete error, and the mutual integration method is independent of the path, which can bypass the crack tip singular area, thereby improving the accuracy of the stress intensity factor calculation and improving the accuracy of the crack propagation life study.

[0016] (3) The embodiment of the present invention modifies the calculation formula of the stress intensity factor of the crack tip of the welded structure, and the theoretical formula Based on this, a correction term is introduced Get the final stress intensity factor calculation formula This correction retains the original physical information of the theoretical formula and improves the accuracy of the stress intensity factor solution by introducing correction terms related to the half-crack length, crack position and leading edge position.

[0017] (4) The embodiment of the present invention uses a support vector machine regression model to perform regression analysis on the stress intensity factor correction term, and establishes the three parameters of half crack length, crack position and leading edge position and the stress intensity factor correction term K * The mapping relationship And into the stress intensity factor correction formula The support vector machine regression model can ensure more reliable calculation results under small sample and multi-dimensional parameter conditions. At the same time, it replaces the complex and time-consuming finite element simulation to obtain the solution of the correction term, thereby improving the efficiency of the calculation of the crack growth life of the welded structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a simplified flow chart of a method for analyzing crack growth life of a welded structure based on a support vector machine model according to an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of a three-dimensional flat plate welding structure model according to an embodiment of the present invention;

[0020] Figure 3 Schematic diagram of the division of the sub-model of the three-dimensional flat plate welding structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0022] This embodiment of the present invention uses a three-dimensional flat plate containing a welded structure as an example to specifically illustrate a method for analyzing the crack growth life of a welded structure. This method corrects the stress intensity factor of the welded structure. Furthermore, this method can be extended to analyze other components containing welded structures.

[0023] An embodiment of the present invention provides a method for analyzing the crack growth life of a welded structure based on a support vector machine model, which specifically includes the following steps:

[0024] Step 1: Use hexahedral elements to discretize the geometric model of the welded structure to obtain a finite element model, and perform static simulation analysis to obtain the node displacement and stress distribution calculation results.

[0025] In the embodiment of the present invention, the geometric model of the three-dimensional plate with a welded structure (hereinafter referred to as the plate) is as follows: Figure 2 In this geometric model, the plate consists of three regions: the base material region, the heat-affected zone, and the weld region. The weld region is a trapezoid with an upper surface width of 4 mm and a lower surface width of 6 mm; the heat-affected zone is a parallelepiped with an upper and lower surface width of 8 mm; the rest is the base material region. The overall thickness of the model is 2 mm, the total width is 40 mm, and the total height is 50 mm. The material properties are set as shown in Table 1:

[0026] Table 1 Parameter settings of flat plate material with welded structure

[0027]

[0028] The C3D8R eight-node linear hexahedron element is used to Figure 1The geometric model shown is discretized to obtain a 4000-element finite element model, which is the global model used for simulation. A clamped boundary condition is applied to the bottom surface of the geometric model, and a uniformly distributed tensile surface load of P = 1 MPa is applied to the top surface of the geometric model. Based on this, static finite element calculations are performed to obtain the corresponding static analysis results.

[0029] Step 2: Implant an initial crack at the center of the weld in the finite element model, divide the finite element model into a sub-model containing the initial crack and other partial models, re-discretize the sub-model using tetrahedral elements, and encrypt the crack tip. Retain hexahedral elements in other partial models, retain the nodes of the contact surface between the sub-model and other partial models, and use the node displacement of the contact surface as the boundary condition of the sub-model.

[0030] In the embodiment of the present invention, an initial crack is implanted in the weld center of the finite element model established in step 1 (i.e., the center of the weld area). The initial crack is, for example, an initial through-crack. The entire finite element model is divided into a sub-model containing the initial crack and other partial models. Figure 3 As shown, since the crack tip stress has r -0.5 To address singularities, the sub-model was re-meshed using tetrahedral elements, and the crack tip region was meshed more densely to accommodate the stress field at the crack tip. The rest of the model remained with hexahedral elements. The nodes (i.e., mesh nodes) at the interface between the sub-model and the rest of the model remained unchanged. The node displacements at these interface points, calculated using the finite element model in step 1, were used as boundary conditions for the crack growth analysis of the sub-model.

[0031] Step 3: Perform crack propagation finite element calculation on the sub-model to obtain the numerical solution K of the stress intensity factor at the crack tip under different values ​​of half crack length a, crack position d and front edge position λ. e .

[0032] In an embodiment of the present invention, three physical quantities that are strongly correlated with the stress intensity factor, namely, half-crack length a, crack position d, and front position λ, are used as key factors affecting the stress intensity factor at the crack tip for calculation. The initial through-crack implanted in the embodiment of the present invention is a middle through-crack, which has two fronts in the positive and negative directions along the normal of the weld. Here, the positive front edge is taken as the research object, that is, the crack front close to the load application surface is studied and calculated, and the numerical solution of the stress intensity factor at the crack tip is calculated. Specifically, when the half-crack length a, crack position d, and front position λ are {1.0mm, 1.5mm}, {0.0mm, ±5.0mm}, {0, 0.5, 1.0} respectively, the numerical solution K of the stress intensity factor at the crack tip is calculated. e , as shown in Table 2:

[0033] Table 2 Numerical solution of stress intensity factor K at crack tip of flat plate with welded structure e

[0034]

[0035] Step 4: Use the stress intensity factor calculation formula Calculate the analytical solution and calculate the numerical solution K e and the analytical solution K t The difference K * , K * =K e -K t .

[0036] Specifically, the stress intensity factor calculation formula is Given the half crack length a, crack position d and leading edge position λ in step 3, the corresponding stress intensity factor analytical solution K is calculated. t , In the embodiment of the present invention, the stress intensity factor calculation formula should be The corresponding calculation results are shown in Table 3:

[0037] Table 3 Analytical solution of stress intensity factor K at crack tip of plate with welded structure t

[0038]

[0039] According to the numerical solution of stress intensity factor shown in Table 2, the difference K between the two solutions is calculated. * =K e -K t , the difference is shown in Table 4:

[0040] Table 4 Difference K between numerical and analytical solutions of stress intensity factors at crack tip of flat plate with welded structure *

[0041]

[0042] Step 5: Take the half crack length a, crack position d and front edge position λ as input, and use the difference K * As the output, establish a support vector machine regression model And according to the stress intensity factor calculation formula Obtain the stress intensity factor correction formula

[0043] Specifically, the three key parameters of half crack length a, crack position d and leading edge position λ in step 3 are used as input, and the difference K in step 4 is used as input. *As the output, a support vector machine regression model is established. Since the fitting accuracy of the support vector machine regression model depends on the number of training sets, based on the specific values ​​of the half crack length a and crack position d in step three, the values ​​{2.0mm} and {±2.5mm} are added. The value of the leading edge position λ is given by the finite element calculation, and steps three and four are repeated to obtain the corresponding difference K. * , a total of 345 sample points.

[0044] The embodiment of the present invention selects the support vector machine regression model (SVR) as the proxy model to calculate the difference K * Fitting is performed to obtain the regression relationship between it and the three input variables: half crack length a, crack position d, and leading edge position λ. The detailed process is as follows:

[0045] How will the difference K be constructed? * The functional relationship between the half crack length a, crack position d and leading edge position λ is transformed into the problem of establishing the optimal hyperplane. is the regression prediction value of the stress intensity factor difference, which can be expressed by the following function:

[0046]

[0047] Among them, w represents the weight vector in the initial sample space, and b represents the offset.

[0048] According to the principle of structural risk minimization, in the embodiment of the present invention, the establishment of the optimal hyperplane is transformed into the following minimization problem:

[0049]

[0050] in, ] part represents the error accuracy, L represents the loss function, and the SVR model uses the ε-insensitive loss function ε represents the bandwidth of the ε-insensitive loss function interval. The error precision of samples within the bandwidth is recorded as zero; for samples outside the bandwidth, y i -f(x i )>ε, the error accuracy is recorded as y i -f(x i )<-ε, the error accuracy is recorded as ξ i . ||w|| 2 The part represents the confidence range, and the bandwidth of the ε-insensitive interval band is 2ε / (||w||) 2 , maximizing bandwidth is to minimize ||w||. K i * represents the true value, represents the predicted value of the support vector machine regression (SVR) model, and ||·|| represents the quadratic norm. The penalty coefficient C (C>0) is responsible for coordinating the balance between the error accuracy and confidence range of the SVR model.

[0051] Convert the problem of how to construct the optimal hyperplane into a minimization problem:

[0052]

[0053] The process of using the Lagrange multiplier method to solve the above minimization problem with inequality constraints is as follows:

[0054] Introducing Lagrange multipliers The above minimization problem with inequality constraints is transformed into the Lagrangian equation, using replace The same applies to the following:

[0055]

[0056] For variables Taking the derivative and simplifying we get:

[0057]

[0058] According to the Kuhn-Tucker condition (KKT), we get:

[0059]

[0060] Then, based on the Lagrange equation obtained by transforming the aforementioned minimization problem with inequality constraints, the problem of solving the SVR model is finally transformed into solving the quadratic programming problem shown in the following formula:

[0061]

[0062] φ(x i ) T φ(x j ) represents the inner product operation of two samples in the original space. For nonlinear regression problems, directly calculate φ(x i ) T φ(x j )The amount of calculation is too large, so the kernel function Kernal(x i ,x j )=φ(x i ) T φ(x j ), map the data to a high-dimensional feature space so that the data is approximately linearly separable in the high-dimensional feature space, and then perform linear regression.

[0063] In this embodiment of the present invention, a radial basis function (RBF) kernel is selected to perform the above transformation. The elements in the kernel matrix Kernal are:

[0064]

[0065] The width parameter γ is automatically selected to avoid the complexity of manual parameter adjustment and provide reasonable performance. The kernel matrix Kernal of the embodiment of the present invention is calculated as:

[0066]

[0067] To solve the Lagrange multiplier Use the quadratic programming method to solve the problem and convert it into a quadratic programming matrix form:

[0068]

[0069] Among them, the physical meaning of Lagrange multipliers is explained: when When the sample points are located in a strip area with a width of ε, referred to as the ε interval zone. Usually, most of the α i and The value of is zero; when Sometimes, there are At this time, the sample point is at the upper boundary of the ε interval band. Similarly, when When , the sample point is at the lower boundary of the ε-interval band; when When , the sample point is outside the upper boundary of the ε interval band. When , the sample point is outside the lower boundary of the ε interval band.

[0070] Each sample point can be considered as a vector. In the embodiment of the present invention, the half crack length a, crack position d and leading edge position λ of the sample point form a sample vector x=[ad λ]. and The vectors corresponding to samples that are not equal to 0 at the same time are used as support vectors. Support vectors are used to determine the key points of the decision boundary. They determine the position and shape of the decision boundary, thereby affecting the prediction performance of the support vector machine regression model.

[0071] In the embodiment of the present invention, the support vector corresponding to the sample that meets the conditions is:

[0072]

[0073] At the same time, the response value K corresponding to the sample point * for: [0.13856226 0.13929272 0.16590188 0.14313055 0.15501498 0.200413650.20290985]

[0075] Solving the above minimization problem, we get the Lagrange multiplier:

[0076] [-0.02023254 -0.05546061 0.05493472 -0.06356209 0.06610319 0.00103360.01718373]

[0077] Substitute the matrix form of the quadratic programming for the above problem of solving the Lagrange multiplier into the variable In the derived and simplified formula, the KKT conditions are combined to obtain the calculation formula for the offset b:

[0078]

[0079] The embodiment of the present invention solves and obtains the intercept, ie, the offset, b=0.1590.

[0080] Correspondingly, the regression function equation for the SVR model is:

[0081]

[0082] In the embodiment of the present invention:

[0083]

[0084] In the embodiment of the present invention, the RBF kernel is selected for calculation. For nonlinear SVR, the explicit regression formula will not be output, but the trained model, including support vectors, kernel function parameters and other data, can be saved and used to predict new data.

[0085] Mean square error (MSE) is one of the commonly used loss functions and evaluation indicators in regression problems. It represents the average of the squares of the differences between the model's predicted values ​​and the true values. The calculation formula is In the embodiment of the present invention, for the above 345 sample points and corresponding differences The mean square error of the fitted SVR model is calculated to be 0.002168, indicating that the difference between the model predicted value and the true value is very small, and the prediction performance of the SVR model in the embodiment of the present invention is relatively good.

[0086] Finally, the stress intensity factor calculation formula used in the embodiment of the present invention is and support vector machine regression equation Combined with the above, the final stress intensity factor correction formula is as follows:

[0087]

[0088] This stress intensity factor correction formula is oriented to welded structures and can be used in the next step of fatigue crack growth analysis and fatigue life analysis.

[0089] In the above steps, the correction of the crack growth rate of the welded structure is concentrated on the basic analytical formula of the stress intensity factor The correction is made by introducing K into the formula * As a correction term, the support vector machine model is selected to fit the correction term K*. The key parameters of half crack length, crack position and front position are used as input, and the stress intensity factor at the crack tip is used to numerically solve K e and analytical solution of stress intensity factor The difference between the two values ​​is used as the output, and a support vector machine model is established. Further combined with the analytical solution, a correction formula for calculating the stress intensity factor suitable for welded structures is obtained. This revised formula takes into account the influence of three key parameters on the stress intensity factor, improving the calculation accuracy of the stress intensity factor. At the same time, this revised formula can be used to solve the stress intensity factor involved in the fatigue crack growth life calculation, eliminating the need to repeat the tedious steps of finite element modeling calculations, thereby improving the computational efficiency of fatigue crack analysis.

[0090] Step 6: Substitute the stress intensity factor correction formula K'(a, d, λ) into the Paris crack growth formula Get the Paris correction formula The structural residual strength criterion is selected as the criterion to obtain the fatigue life prediction value of the welded structure.

[0091] Among them, the structural residual strength criterion is: under the action of typical alternating loads, the maximum stress intensity factor K at the crack tip is max Reach the fracture toughness K of the welding material at the crack tip c When the initial crack rapidly expands and forms a fracture, the number of load cycles N at this time is the predicted value of the fatigue life of the welded structure. The above typical alternating load refers to the sinusoidal cyclic load.

[0092] In the embodiment of the present invention, when fatigue crack growth analysis is performed, a sinusoidal cyclic load with a stress ratio R = 0.1 is applied, and the peak value is consistent with the aforementioned load P = 1 MPa. The load and stress intensity factor correction formula K' is substituted into Where C mater ,m ial is a constant related to the material, and its value here is C material =8*10 -12 ,m material =3, the Paris correction formula is:

[0093]

[0094] By shifting the terms and integrating the Paris correction formula, we can obtain:

[0095]

[0096] The number of load cycles N is an integer, and the stress intensity factor K' is updated once N increases by one step. Since the increase in half crack length a is extremely small when N increases by one step, that is, when the stress cycle is one time, K' is regarded as a constant in this process to calculate the crack growth rate. The integration process can be converted into a cumulative summation:

[0097]

[0098] Where a0 is the initial half crack length, when 2a0+∑da=a max When the crack length 2a0+∑da reaches the material fracture toughness K c The corresponding a max , output the corresponding number of load cycles N, which is the fatigue life prediction value of the welded structure.

[0099] In the embodiment of the present invention, a is set respectively 1max =1.000005mm,a 2max =1.500005mm, fatigue crack growth analysis and prediction are performed, and the results and relative errors are shown in Table 5:

[0100] Table 5 Fatigue crack growth analysis results and relative errors

[0101]

[0102] In this example, the model results are tested using parameter values ​​that are within the training set's maximum value range, but not within the training set. Similarly, when selecting the parameter range in step 3, choosing values ​​that include the target operating conditions or common operating conditions as the maximum value of the value interval can effectively improve subsequent fitting accuracy.

[0103] In summary, the method for analyzing the crack propagation life of welded structures based on the support vector machine model provided in the embodiment of the present invention is based on fracture mechanics and is aimed at special engineering structures (such as structures containing welded structures) to achieve rapid calculation of the stress intensity factor at the crack tip. According to the static analysis results of the global model, the boundary conditions of the sub-model are obtained, and the mesh of the sub-model is redrawn to obtain a mesh unit that adapts to the stress field at the crack tip. According to the static analysis results and the characteristics of the welded structure, an initial crack is implanted at the weld to simulate the stable expansion of cracks in real components. The numerical solution of the stress intensity factor is calculated using the finite element method, and the difference between the numerical solution and the analytical solution of the stress intensity factor is obtained under different half-crack lengths, crack positions and leading edge position parameters, and the support vector machine regression model is used to fit it. The stress intensity factor calculation formula and support vector machine regression model Combined with the above formula, the stress intensity factor correction formula is obtained. Based on the Paris formula and the stress intensity factor correction formula, a rapid prediction of crack growth life is achieved. This method considers the influence of different parameters on the stress intensity factor, and compared with theoretical calculation methods, the crack growth life calculation has higher accuracy. At the same time, the use of a support vector machine regression model instead of finite element simulation further improves the calculation efficiency of crack growth life.

[0104] Throughout this specification, references to "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" indicate that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, illustrative uses of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for analyzing crack growth life of welded structures based on a support vector machine model, characterized in that: include: Step 1: Use hexahedral elements to discretize the geometric model of the welded structure to obtain a finite element model, and perform static simulation analysis to obtain the node displacement and stress distribution calculation results; Step 2: implanting an initial crack at the center of the weld of the finite element model, dividing the finite element model into a sub-model containing the initial crack and other partial models, re-discretizing the sub-model using tetrahedral elements, and performing encryption processing on the crack tip, while retaining hexahedral elements in the other partial models. The nodes of the contact surface between the sub-model and the other partial models are retained, and the node displacement of the contact surface is used as the boundary condition of the sub-model; Step 3: Perform crack propagation finite element calculation on the sub-model to obtain the numerical solution K of the stress intensity factor at the crack tip under different values ​​of half crack length a, crack position d and front edge position λ. e ; Step 4: Use the stress intensity factor calculation formula Calculate the analytical solution and calculate the numerical solution K e With the analytical solution K t The difference K * , K * =K e -K t ; Step 5: Take the half crack length a, the crack position d and the leading edge position λ as input, and use the difference K * As the output, establish a support vector machine regression model And according to the stress intensity factor calculation formula Obtain the stress intensity factor correction formula Step 6: Substitute the stress intensity factor correction formula K'(a, d, λ) into the Paris crack growth formula Get the Paris correction formula The structural residual strength criterion is selected as the criterion to obtain the fatigue life prediction value of the welded structure.

2. The analysis method according to claim 1, characterized in that The tetrahedral unit is a tetrahedral singular grid.

3. The analysis method according to claim 1, characterized in that The structural residual strength criterion is: under the action of typical alternating loads, the maximum stress intensity factor K at the crack tip is max Reach the fracture toughness K of the weld material at the crack tip c When the initial crack rapidly expands and forms a fracture, the corresponding number of load cycles N is the fatigue life prediction value of the welded structure.

4. The analysis method according to claim 1, characterized in that The step five includes: According to the finite element calculation, increase the values ​​of the half crack length a, the crack position d and the leading edge position λ, and repeat the steps 3 and 4 to obtain the corresponding difference K * ; The half crack length a, the crack position d and the leading edge position λ are used as inputs, and the corresponding difference K * As output, the support vector machine regression model is established According to the support vector machine regression model And the stress intensity factor calculation formula Obtain the stress intensity factor calculation correction formula

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