A numerical simulation method suitable for evaluating high-cycle fatigue performance of dot matrix structure

Abstract

The application provides a numerical simulation method suitable for evaluating high-cycle fatigue performance of a lattice structure, and belongs to the technical field of numerical simulation. A specimen effective stiffness matrix is obtained by combining a specimen stiffness matrix with a progressive homogenization theory, and a specimen homogenization constitutive model is constructed; a corresponding stress-fatigue life model is constructed by applying a load to the specimen homogenization constitutive model; a specimen S-N curve is established based on the specimen stiffness matrix, and a specimen fatigue evaluation life is further obtained; unknown parameters of the corresponding stress-fatigue life model are solved based on the fatigue evaluation life, and are brought into a stress-fatigue life model of the lattice structure specimen to obtain a fatigue life prediction model; for a lattice structure to-be-measured specimen made of the same material as the lattice structure specimen, basic material properties and lattice structure parameters and loads of the to-be-measured specimen are input into the fatigue life prediction model to obtain a predicted fatigue life of the to-be-measured specimen. The problems of high cost and long time consumption in predicting the fatigue life in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of high-cycle fatigue assessment technology for lattice structures, and in particular to a numerical simulation method suitable for assessing the high-cycle fatigue performance of lattice structures. Background Technology

[0002] Lattice structures, due to their excellent specific strength and specific stiffness, are widely used in aerospace, automotive, and other fields. However, these applications make lattice structures susceptible to high-cycle fatigue damage during service, leading to a decline in structural performance. Therefore, effectively evaluating the fatigue performance of lattice structures is crucial to ensuring their reliability and safety; it also provides reliable data for structural optimization design, which is of great significance for improving the performance and safety of lattice structures in practical applications.

[0003] In existing technologies, fatigue performance is obtained by conducting high-cycle fatigue tests. However, due to the geometric diversity and structural inhomogeneity of lattice structures, conducting high-cycle fatigue tests is not only costly and time-consuming, but also makes it difficult to capture the distribution of field variables that cause violent oscillations at local locations.

[0004] Therefore, a numerical simulation method suitable for evaluating the high-cycle fatigue performance of lattice structures is needed. Summary of the Invention

[0005] In view of this, the present invention provides a numerical simulation method suitable for evaluating the high-cycle fatigue performance of lattice structures. It utilizes an asymptotic homogenization method to consider the severe oscillation characteristics of local field variables in lattice structures, equating the lattice structure with a homogenized structure. It also combines the classical Basquin equation to evaluate the high-cycle fatigue performance of lattice structures, thus solving the problems of high cost and time consumption in conducting high-cycle fatigue tests, and the difficulty in capturing the distribution of field variables with severe oscillations at local locations.

[0006] Therefore, the present invention provides the following technical solution:

[0007] A numerical simulation method suitable for evaluating the high-cycle fatigue performance of lattice structures includes:

[0008] The effective stiffness matrix of the lattice structure specimen was obtained by combining the stiffness matrix of the lattice structure specimen with the asymptotic homogenization theory.

[0009] Based on the effective stiffness matrix of the lattice structure specimen, a homogenized constitutive model of the lattice structure specimen and the SN curve of the lattice structure specimen are constructed.

[0010] A relative stress-fatigue life model is constructed by applying loads to the homogenized constitutive model of the lattice structure specimen.

[0011] The fatigue life of the lattice structure specimen was obtained by using the SN curve of the lattice structure specimen.

[0012] Based on the fatigue assessment life of the lattice structure specimen, the unknown parameters of the relative stress-fatigue life model are obtained.

[0013] By substituting the known model parameters into the stress-fatigue life model of the lattice structure specimen, a fatigue life prediction model is obtained.

[0014] For a lattice structure test piece made of the same material as the lattice structure specimen, input the basic material properties of the test piece, the lattice structure parameters, and the load into the fatigue life prediction model to obtain the predicted fatigue life of the test piece.

[0015] Furthermore, the method of obtaining the effective stiffness matrix of the lattice structure specimen using the stiffness matrix of the lattice structure specimen combined with the asymptotic homogenization theory includes:

[0016] The basic material properties of lattice structure specimens were obtained through static experiments.

[0017] The stiffness matrix of the lattice structure specimen is established using the basic material properties of the lattice structure specimen.

[0018] Determine the geometric parameters of the lattice structure specimen and establish a three-dimensional model of the lattice structure specimen;

[0019] The stiffness matrix of the lattice structure specimen is substituted into the three-dimensional model of the lattice structure specimen, and the lattice structure specimen is meshed to obtain the set of lattice structure specimen mesh elements.

[0020] By setting periodic boundary conditions based on the grid cell set of the lattice structure specimen, the micro-strain components of the grid cell of the lattice structure specimen are obtained.

[0021] The effective stiffness matrix of the lattice structure specimen is obtained by combining the set of micro-strain components of the grid element with the asymptotic homogenization theory.

[0022] Further, the step of obtaining a set of mesh elements for the lattice structure specimen by mesh generation includes:

[0023] The mesh cell type is C3D4;

[0024] The meshing method is to select free meshing and decrease the mesh cell size in descending order.

[0025] Furthermore, the periodic boundary conditions are as follows:

[0026]

[0027] in, For the macroscopic strain tensor, u i Let x be the displacement of the i-th node, x be the coordinate system component, L be the length of the unit cell of the lattice structure, and e be the displacement of the ith node.j It is a unit vector.

[0028] Furthermore, based on the lattice structure specimen mesh element set, periodic boundary conditions are set to obtain the micro-strain components of the lattice structure specimen mesh element, including:

[0029]

[0030] Where u and v are the nodal displacements in the x and y directions, respectively, and ε 11 ε 22 and ε 12 These are the components of the macroscopic strain tensor acting on the unit cell;

[0031] Establish a linear relationship between the macroscopic strain tensor and the microscopic strain tensor to obtain the microscopic strain components.

[0032] Furthermore, the effective stiffness matrix of the lattice structure specimen, obtained by combining the set of micro-strain components of the grid elements with the asymptotic homogenization theory, includes:

[0033] The effective stiffness matrix is ​​obtained by integrating the micro-stress of the unit cell of the lattice structure and dividing by the unit cell volume.

[0034] Furthermore, the process of applying loads to the homogenized constitutive model of the lattice structure specimen to construct a relative stress-fatigue life model includes:

[0035] Cyclic loads were applied to the homogenized constitutive model of the lattice structure specimen to obtain the relative stress range;

[0036] A relative stress-fatigue life model was constructed by combining the Basquin formula with the relative stress range.

[0037] Furthermore, the construction of the SN curve of the lattice structure specimen based on the stiffness matrix of the lattice structure specimen includes:

[0038] Based on the three-dimensional model of the lattice structure specimen, two analysis steps are defined to apply the peak and valley values ​​of the cyclic load to solve the internal stress state of a single cycle.

[0039] The SN curve is constructed by combining the basic material properties of the lattice structure specimen with the stress state solution results.

[0040] Furthermore, the step of obtaining the fatigue assessment life of the lattice structure specimen using the SN curve of the lattice structure specimen includes:

[0041] The simulated fatigue life of the lattice structure specimen was calculated using the SN curve of the lattice structure specimen.

[0042] High-cycle fatigue tests were conducted on lattice structure specimens to obtain their true fatigue life.

[0043] The simulated fatigue life is verified to be within the allowable error range using the actual fatigue life.

[0044] If the simulated fatigue life is within the allowable error range, then the simulated fatigue life is used as the fatigue evaluation life of the lattice structure specimen.

[0045] Furthermore, verifying whether the simulated fatigue life is within the allowable error range using the actual fatigue life also includes:

[0046] If the simulated fatigue life is not within the allowable error range, the simulated fatigue life of the lattice structure specimen is calculated iteratively until the simulated fatigue life is within the allowable error range.

[0047] Advantages and positive effects of the present invention:

[0048] The method of this invention is universal and applicable to lattice structures of various topological unit cells.

[0049] 1) This invention utilizes periodic boundary conditions and asymptotic homogenization methods, while simultaneously considering the periodic arrangement characteristics of the unit cells of the lattice structure and the local violent oscillation characteristics of the field variables, to transform the lattice structure into a homogenized structure, thereby realizing the parametric simulation of the homogenized material properties of the lattice structure and obtaining the equivalent constitutive model of the homogenized lattice structure.

[0050] 2) Based on the equivalent constitutive model after homogenization of the lattice structure, this invention combines the classic Basquin model to establish a simpler and more effective log-linear homogenized equivalent model to evaluate the high-cycle fatigue performance of the lattice structure. Attached Figure Description

[0051] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a flowchart of the method of the present invention;

[0053] Figure 2 This is a dimensional diagram of the lattice structure and unit cell in an embodiment of the present invention;

[0054] Figure 3 This is a unit cell cloud diagram of the lattice structure under periodic boundary conditions in the post-processing stage of Ansys APDL in an embodiment of the present invention.

[0055] Figure 4 These are the stress analysis cloud diagrams and fatigue life cloud diagrams of the lattice structure in the embodiments of the present invention;

[0056] Figure 5 This is a flowchart of the FDM metal 3D printing process in an embodiment of the present invention;

[0057] Figure 6 This is a diagram showing the dimensional parameters of the standard specimen for static testing in an embodiment of the present invention.

[0058] Figure 7 This is an analysis of the error band in the lifetime prediction of the homogenized equivalent model in the embodiments of the present invention;

[0059] Figure 8 This is a flowchart illustrating the steps of an embodiment of the present invention. Detailed Implementation

[0060] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0061] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0062] This invention provides a numerical simulation method suitable for evaluating the high-cycle fatigue performance of lattice structures. Based on the inherent periodic arrangement of unit cells and the non-uniform distribution of internal field variables in lattice structures, and combining asymptotic homogenization theory and classical fatigue evaluation models, the method considers the periodic and regular arrangement of unit cells by applying periodic boundary conditions, and uses the asymptotic homogenization method to account for the violent oscillations of local field variables in the lattice structure. This equates the lattice structure to a homogenized structure, and the high-cycle fatigue performance of the lattice structure is evaluated using the classical Basquin equation. This method effectively considers the local oscillations of field variables in the lattice structure while addressing the difficulties in fatigue testing caused by the diversity of lattice structures.

[0063] Combination Figure 1 The method of the present invention includes:

[0064] S1. Obtain the basic material properties of the target metal by static mechanical test of standard lattice structure specimen; material properties obtained by static mechanical test (9 engineering constants, including E11, E22, E33, G12, G13, G23, v12, v13, v23).

[0065] S2. Construct the material's flexibility matrix based on the material properties of S1, and then invert the matrix to obtain the material's stiffness matrix.

[0066] S3. Select the classic lattice structure and determine the geometric parameters; based on the geometric parameters of the lattice structure, construct the 3D model of the lattice structure unit cell and the overall 3D model of the lattice structure using Solidworks.

[0067] S4. Apply the material stiffness matrix to the three-dimensional model of the lattice structure unit cell;

[0068] S5. Select C3D4 mesh elements, use free mesh generation, conduct mesh convergence analysis, and obtain the mesh element numbers and coordinate sets;

[0069] S6. Considering the periodic arrangement characteristics of the unit cells of the lattice structure, apply periodic boundary conditions to the unit cells of the lattice structure to obtain the set of micro-strain components of the mesh element.

[0070] Periodic boundary conditions are expressed as follows:

[0071]

[0072] in, For the macroscopic strain tensor, u i Let x be the displacement of the i-th node, x be the coordinate system component, L be the length of the unit cell of the lattice structure, and e be the displacement of the ith node. j Let be a unit vector. Expanding this equation further, we get:

[0073]

[0074] Where u and v are the nodal displacements in the x and y directions, respectively, and ε 11 ,ε 22 , and ε 12 The component of the macroscopic strain tensor acting on the unit cell.

[0075] By combining the set of mesh elements, the element nodes at the edge of the lattice structure unit cell are selected. The formula is then applied to the mesh element nodes at the relative boundary of the lattice structure unit cell. A macroscopic unit strain tensor is applied as a periodic boundary condition and the solution is obtained to obtain the set of microscopic strain components of the mesh element.

[0076] S7. Based on the set of micro-strain components of the grid element, the effective stiffness matrix of the lattice structure is obtained using the asymptotic homogenization theory, and then the equivalent constitutive model expression of the homogenized lattice structure is obtained.

[0077] The inhomogeneity of lattice structures causes violent oscillations in internal field variables at local locations. Asymptotic homogeneity theory can address this problem by treating the lattice structure as an equivalent homogeneous structure. Considering the small deformation assumption and the elastic properties of the material, this can be addressed using the local structure tensor M. ijkl Establish macroscopic strain tensor With the micro-strain tensor ε ij The linear relationship between them is as follows:

[0078]

[0079] Under periodic boundary conditions, the microscopic strain tensor ε of each mesh element in the unit cell of the lattice structure is obtained. ij Combined, solve for the local structure tensor M at the centroid of each mesh cell. ijkl .

[0080] The effective stiffness matrix is ​​obtained by integrating the micro-stress of a unit cell of the lattice structure and dividing by the unit cell volume VRVE.

[0081]

[0082] Among them, the effective stiffness matrix Defined as:

[0083]

[0084] Furthermore, the constitutive model of the lattice structure simplifies to the constitutive model of the homogeneous structure:

[0085]

[0086] S8. Determine the displacement history of the lattice structure under cyclic loading, calculate the relative strain range, and obtain the relative stress range by combining the equivalent constitutive model.

[0087] S9. Combining the classic Basquin formula, we obtain the logarithmic linear relationship between the relative stress and lifetime of the lattice structure and construct the Basquin logarithmic linear model.

[0088] S10. Based on the three-dimensional model of the unit cell of the lattice structure and the overall three-dimensional model of the lattice structure, apply the corresponding cyclic load conditions, define two analysis steps, and solve for the peak and valley values ​​under the cyclic loading conditions respectively.

[0089] S11. Use the solution results from S10 to simulate and solve the fatigue life of the lattice structure; and conduct some fatigue tests to verify the effectiveness of the simulation results.

[0090] The SN curve of the lattice structure is approximated by using the results of static tests (elastic modulus and tensile strength). The stress value corresponding to the last incremental step of the two analysis steps in S10 is used as the maximum and minimum values ​​of cyclic loading to simulate and solve the fatigue life of the lattice structure.

[0091] S12. Using the fatigue life of the lattice structure solved in S11 as the basis for parameter identification of the Basquin log-linear model, the model parameters a and b are obtained.

[0092] Combination Figure 8 The method of the present invention will be further illustrated by specific embodiments:

[0093] Step 1): In this embodiment, a universal testing machine is used to conduct static tests on a standard lattice structure specimen; simultaneously, real-time DIC strain field measurements are performed to determine the basic material properties of the target metal, including elastic modulus, shear modulus, Poisson's ratio, and tensile strength; specifically, nine engineering constants, including E... 11 E 22 E 33 G 12 G 13 G 23 v 12 v 13 v 23 ;

[0094] Step 2): Based on the material properties obtained from the static test in step (1), construct the material's compliance matrix, and then invert the matrix to obtain the material's stiffness matrix;

[0095] Step 3): In this embodiment, based on the geometric parameters of the lattice structure, Solidworks is used to create 3D models of the lattice structure unit cell and the overall lattice structure, and the established models are saved as .step files.

[0096] Step 4): Combining Matlab code and Ansys APDL command flow, use the fprint(*) function to call the .step file of the lattice structure unit cell as the 3D model of Ansys APDL, and enter the Ansys APDL preprocessing stage (code "fprintf(Ansys_file, ' / PREP7\n');").

[0097] Step 5): Using the Matlab function “fprint(*)” and the Ansys APDL command stream “MPDATA,Lab,MAT,SLOC,C1,C2,C3,C4,C5,C6”, the experimentally obtained material properties are assigned to the imported lattice structure unit cell.

[0098] Step 6): In this embodiment, the C3D4 mesh element type is selected (command flow "MSHAPE, KEY, Dimension", setting KEY=1, Dimension=3D). Combining Matlab programming and ANSYS APDL command flow, the free mesh generation method is selected (command flow "MSHKEY, KEY", setting KEY=0). The mesh element size is sequentially reduced from largest to smallest, and the mesh is generated (command flow "VMESH, all") until the simulation solution tends to stabilize and the mesh convergence condition is met. The numbers and coordinates of all mesh elements are stored in a .log file.

[0099] Step 7): Since the lattice structure is composed of periodically arranged unit cells, the periodic boundary conditions are satisfied at the unit cell boundaries, as follows:

[0100] u i (x+L)=u i (x)+ε ij Le j

[0101] Where, ε ij For the macroscopic strain tensor, u i Let x be the displacement of the i-th node, x be the coordinate system component, L be the length of the unit cell of the lattice structure, and e be the displacement of the ith node. j Let be a unit vector. Expanding this equation further, we get:

[0102]

[0103] Where u and v are the nodal displacements in the x and y directions, respectively, and ε 11 ε 22 and ε 12The components of the macroscopic strain tensor acting on the unit cell are used. By programming with MATLAB, the .log file stored in step (6) is called to filter the unit nodes at the edge of the lattice structure unit cell. The expansion is applied to the mesh unit nodes at the relative boundary of the lattice structure unit cell. The macroscopic unit strain tensor is applied as a periodic boundary condition and solved. The solution is then entered into the Ansys APDL post-processing stage.

[0104] Step 8): Combine Matlab programming and Ansys APDL command flow to store the micro-strain components ε of all mesh elements. ij Using the asymptotic homogenization theory, the effective stiffness matrix of the lattice structure is obtained. To further obtain the equivalent constitutive expression of the homogenized lattice structure, specifically including:

[0105] The inhomogeneity of lattice structures causes violent oscillations in internal field variables at local locations. Asymptotic homogeneity theory can address this problem by treating the lattice structure as an equivalent homogeneous structure. Considering the small deformation assumption and the elastic properties of the material, this can be addressed using the local structure tensor M. ijkl Establish macroscopic strain tensor With the micro-strain tensor ε ij The linear relationship between them is as follows:

[0106]

[0107] Under the periodic boundary conditions in step (7), the micro-strain tensor ε of each mesh element in the lattice structure unit cell can be obtained. ij Combined with macroscopic strain tensor With the micro-strain tensor ε ij The linear relationship between them is used to solve for the local structure tensor M at the centroid of each mesh element. ijkl Furthermore, this can be achieved by integrating the microscopic stress of the unit cell of the lattice structure and dividing by the unit cell volume V. RVE Obtain the effective stiffness matrix as follows:

[0108]

[0109] Among them, the effective stiffness matrix Defined as:

[0110]

[0111] The constitutive model of a lattice structure can be simplified to the constitutive model of a homogeneous structure:

[0112]

[0113] Step 9): Taking uniaxial loading as an example, determine the displacement history of the lattice structure under uniaxial cyclic loading, calculate the relative strain range, and obtain the relative stress range by combining the equivalent constitutive model:

[0114]

[0115] in, Represents the relative stress tensor. This represents the relative strain tensor.

[0116] Step 10): Using the classic Basquin formula, a logarithmic linear homogenized equivalent model of the relative stress and lifetime of the lattice structure is obtained:

[0117]

[0118] in, This represents the Mises equivalent stress, where a and b are parameters related to the material, stress ratio, and loading method.

[0119] Step 11): Import the .step file of the lattice structure into Abaqus, define two analysis steps, corresponding to the peak and valley values ​​under the cyclic loading condition, solve them, and save the post-processing results as a .odb file;

[0120] Step 12): Import the .odb file of the lattice structure into the Fe-safe software, input the static test results (elastic modulus and tensile strength) to approximate the SN curve of the lattice structure, and call the stress values ​​corresponding to the last increment step of the two analysis steps in step (11) as the maximum and minimum values ​​of cyclic loading to simulate and solve the fatigue life of the lattice structure. Conduct a small number of high-cycle fatigue tests on the lattice structure to verify the accuracy of the simulation results;

[0121] Step 13): Using the fatigue life simulation solution of the Fe-safe plug-in as the basis for parameter identification of the model established in step (10), material parameters a and b are obtained;

[0122] To verify the accuracy of the method of this invention, a verification experiment was conducted using the above method: FDM metal 3D printing technology was used to print 17-4PH stainless steel standard dog bone samples, which were then subjected to degreasing and sintering heat treatment, as follows: Figure 5 As shown.

[0123] 1. Static tests were conducted on 17-4PH stainless steel dog bone specimens, and the stiffness matrix of the material was established.

[0124] 2. Construct a Basquin log-linear model for 17-4PH stainless steel standard dog bone specimens;

[0125] 3. ABAQUS simulations were conducted using material property parameters obtained from static tests. The simulation results were then imported into Fe-safe for fatigue life assessment. Simultaneously, high-cycle fatigue tests were performed on standard dog bone specimens. The test results were compared with the simulation results to verify the reliability of the numerical simulation results. Standard specimen dimensions are shown below. Figure 6 Table 1 shows a comparison between the fatigue test results and the numerical simulation results of the lattice structure.

[0126] Table 1

[0127]

[0128] 4. The fatigue life numerical simulation results from Fe-safe software were used as the basis for model parameter identification. The parameter identification results are shown in Table 2. Model evaluation error analysis was then conducted. Figure 7 As shown, the method of the present invention has good prediction accuracy. The numerical simulation results and fatigue test results are within 1.5 times the error band. The prediction results of the established homogenized equivalent model are also all within 1.5 times the error band.

[0129] Table 2

[0130]

[0131] This embodiment utilizes Solidworks to build a 3D model, employs Matlab programming and Ansys APDL command flow to conduct parametric numerical simulations of the lattice structure, achieving homogenization of the lattice structure. The fatigue life datasets of lattice structures from Abaqus and Fe-safe are used as the basis for parameter identification in the established fatigue assessment model. This numerical simulation framework is applicable to various types of lattice structures and has significant engineering practical value.

[0132] Based on the method of this invention, the most suitable fatigue life assessment model can be selected according to the material properties and the actual load conditions of the component. Simultaneously, various types of topology optimization can be performed on the lattice structure. That is, the method of obtaining homogenized material properties and equivalent constitutive models of the lattice structure in this invention is applicable to the replaced high-cycle fatigue assessment model and the optimized topological lattice structure. Therefore, this invention has a certain degree of universality in the high-cycle fatigue performance assessment of lattice structures.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 numerical simulation method suitable for evaluating the high-cycle fatigue performance of lattice structures, characterized in that, include: The effective stiffness matrix of the lattice structure specimen is obtained by combining the stiffness matrix of the lattice structure specimen with the asymptotic homogenization theory, including: The basic material properties of lattice structure specimens were obtained through static experiments. The stiffness matrix of the lattice structure specimen is established using the basic material properties of the lattice structure specimen. Determine the geometric parameters of the lattice structure specimen and establish a three-dimensional model of the lattice structure specimen; The stiffness matrix of the lattice structure specimen is substituted into the three-dimensional model of the lattice structure specimen, and the lattice structure specimen is meshed to obtain the set of lattice structure specimen mesh elements. The microscopic strain components of the lattice structure specimen mesh elements are obtained by setting periodic boundary conditions based on the lattice structure specimen mesh element set; the periodic boundary conditions are as follows: in, For macroscopic strain tensor, Let x be the displacement of the i-th node, x be the coordinate system component, and L be the length of the unit cell of the lattice structure. It is a unit vector; The effective stiffness matrix of the lattice structure specimen is obtained by combining the set of micro-strain components of the grid element of the lattice structure specimen with the asymptotic homogenization theory. Based on the effective stiffness matrix of the lattice structure specimen, a homogenized constitutive model of the lattice structure specimen and the SN curve of the lattice structure specimen are constructed. A relative stress-fatigue life model is constructed by applying loads to the homogenized constitutive model of the lattice structure specimen. The fatigue life of the lattice structure specimen was obtained by using the SN curve of the lattice structure specimen. Based on the fatigue assessment life of the lattice structure specimen, the unknown parameters of the relative stress-fatigue life model are obtained. The obtained values ​​of unknown parameters are substituted into the stress-fatigue life model of the lattice structure specimen to obtain the fatigue life prediction model. For a lattice structure test piece made of the same material as the lattice structure specimen, input the basic material properties of the test piece, the lattice structure parameters, and the load into the fatigue life prediction model to obtain the predicted fatigue life of the test piece.

2. The numerical simulation method for evaluating the high-cycle fatigue performance of lattice structures according to claim 1, characterized in that, The process of meshing the lattice structure specimen to obtain a set of lattice structure specimen mesh elements includes: The mesh cell type is C3D4; The meshing method is to select free meshing and decrease the mesh cell size in descending order.

3. The numerical simulation method for evaluating the high-cycle fatigue performance of lattice structures according to claim 1, characterized in that, By setting periodic boundary conditions based on the mesh element set of the lattice structure specimen, the micro-strain components of the mesh element of the lattice structure specimen are obtained, including: Where u and v are the nodal displacements in the x and y directions, respectively. , as well as These are the components of the macroscopic strain tensor acting on the unit cell; Establish a linear relationship between the macroscopic strain tensor and the microscopic strain tensor to obtain the microscopic strain components.

4. The numerical simulation method for evaluating the high-cycle fatigue performance of lattice structures according to claim 3, characterized in that, The effective stiffness matrix of the lattice structure specimen is obtained by combining the set of micro-strain components of the grid elements with the asymptotic homogenization theory, including: The effective stiffness matrix is ​​obtained by integrating the micro-stress of the unit cell of the lattice structure and dividing by the unit cell volume.

5. The numerical simulation method for evaluating the high-cycle fatigue performance of lattice structures according to claim 1, characterized in that, The process of applying loads to the homogenized constitutive model of the lattice structure specimen to construct a relative stress-fatigue life model includes: Cyclic loads were applied to the homogenized constitutive model of the lattice structure specimen to obtain the relative stress range; A relative stress-fatigue life model was constructed by combining the Basquin formula with the relative stress range.

6. The numerical simulation method for evaluating the high-cycle fatigue performance of lattice structures according to claim 1, characterized in that, The construction of the SN curve of the lattice structure specimen based on the stiffness matrix of the lattice structure specimen includes: Based on the three-dimensional model of the lattice structure specimen, two analysis steps are defined to solve the stress state of a single cycle by applying the peak and valley values ​​of the cyclic load respectively. The SN curve is constructed by combining the basic material properties of the lattice structure specimen with the stress state solution results.

7. The numerical simulation method for evaluating the high-cycle fatigue performance of lattice structures according to claim 6, characterized in that, The method of obtaining the fatigue assessment life of a lattice structure specimen using the SN curve includes: The simulated fatigue life of the lattice structure specimen was calculated using the SN curve of the lattice structure specimen. High-cycle fatigue tests were conducted on lattice structure specimens to obtain their true fatigue life. The simulated fatigue life is verified to be within the allowable error range using the actual fatigue life. If the simulated fatigue life is within the allowable error range, then the simulated fatigue life is used as the fatigue evaluation life of the lattice structure specimen.

8. The numerical simulation method for evaluating the high-cycle fatigue performance of lattice structures according to claim 7, characterized in that, Verifying whether the simulated fatigue life is within the allowable error range using the actual fatigue life also includes: If the simulated fatigue life is not within the allowable error range, the simulated fatigue life of the lattice structure specimen is calculated iteratively until the simulated fatigue life is within the allowable error range.

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