High-precision bolt internal force extraction method and device based on finite element large deformation solution

Abstract

The present invention provides a high-precision bolt internal force extraction method and device based on finite element large deformation solution. This scheme simulates the bolt by using a solid model to maximize the reflection of the real stiffness of the bolt joint. When extracting the cross-sectional internal force, a finite element model of the bolt joint is established to perform a large deformation solution to obtain a calculation result. The calculation result is used to compensate for the spatial displacement of the center of the target cross-section of the bolt, and the bolt cross-section bending moment is extracted with this position as the moment center, thereby ensuring the accuracy of the internal force.

Description

Technical Field

[0001] The invention relates to the technical field of wind power generation, and in particular to a method and a device for extracting internal force of a bolt based on high-precision finite element large deformation solution. Background Art

[0002] During the design and development of large wind turbines, simulation design of key components of the unit is required, and the accuracy of the simulation directly affects the design quality of the components. In recent years, with the rapid development of computer technology, finite element numerical analysis methods (FEA, Finite Element Analysis) have been increasingly used in the design and development of wind turbines. Bolt connection is one of the main connection methods between key components of wind turbines, and its design quality directly determines the overall reliability of wind turbines. The design calculation of bolt connections must be based on the cross-sectional internal forces of bolts under complex working conditions. In the industry, the cross-sectional internal forces of bolts under complex working conditions are mainly extracted based on finite element simulation analysis.

[0003] (1) When performing bolt joint simulation analysis, if a solid model is used to simulate the bolt, due to technical bottlenecks, the finite element software cannot compensate for the spatial displacement of the moment center (i.e., the center of the bolt section) under the action of external loads when extracting the bolt section bending moment, resulting in an error in the force arm when calculating the bending moment, and the inability to extract the correct bolt section bending moment;

[0004] (2) Although the modeling method using beam elements does not have the above-mentioned technical bottlenecks, the modeling method of beam elements will cause the stiffness distribution of the various components of the bolt joint in the simulation analysis model to be significantly different from the actual situation, resulting in a large error in the internal force of the bolt section obtained by simulation analysis, which in turn affects the design quality of the bolt joint. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a high-precision bolt internal force extraction method and device based on finite element large deformation solution to solve the technical problem in the prior art that it is impossible to obtain the accurate moment center and thus it is difficult to obtain the correct bolt section bending moment.

[0006] A high-precision bolt internal force extraction method based on finite element large deformation solution, comprising: establishing a solid model according to the geometric dimensions of the bolt, imprinting the position of a target section in the solid model, obtaining the center of the target section as the initial section center, and cutting the imprinted circular line into four equal parts; arranging nodes at the center of the initial section and at the four-equal-section cut respectively, and meshing the solid model; establishing a finite element model of a bolt joint according to the discretized solid model, performing large deformation solution on the finite element model, and obtaining a calculation result; extracting the displacement of the initial section center based on the calculation result, using the displacement to correct the center position of the target section, and calculating the section bending moment of the bolt to obtain the bolt internal force.

[0007] In one of the embodiments, the target cross section in the solid model is a horizontal cross section that moves a preset distance from the boundary of the thread engagement section along the axial direction toward the middle of the bolt.

[0008] In one of the embodiments, before the step of mesh discretizing the solid model, the method further includes: randomly arranging a plurality of nodes at positions other than the center and the quarter-section cutting positions in the initial cross section.

[0009] In one embodiment, the step of performing large deformation solution on the finite element model to obtain calculation results includes: performing multi-step loading processing on the finite element model to obtain the moment corresponding to each loading step, the spatial displacement of each node, and the calculation results of the large deformation solution at the corresponding moment.

[0010] In one of the embodiments, the multi-step loading is divided into preload loading and external load loading, wherein the external load loading is divided into a plurality of load sub-steps.

[0011] In one of the embodiments, the step of extracting the displacement of the center of the initial section based on the calculation result to correct the center position of the target section, and calculating the section bending moment of the bolt to obtain the internal force of the bolt includes: selecting the node at the center of the target section and any two adjacent nodes at the quarter-section cut as the target nodes, and obtaining the spatial coordinates of the target nodes; selecting the moment of any loading step as the target moment, and obtaining the corresponding calculation result and the spatial displacement corresponding to the target node; calculating the target spatial coordinates of the target node at the target moment according to the spatial coordinates of the target node and the corresponding spatial displacement, and obtaining the target center coordinates corresponding to the node at the center of the target section, as well as the first target coordinates and the second target coordinates corresponding to the nodes at the two adjacent quarter-section cuts; taking the target center coordinates as the origin, taking the first target coordinates and the second target coordinates as the positive directions of the x-axis and the y-axis respectively, and creating a three-dimensional rectangular coordinate system as a reference coordinate system; based on the target center coordinates and the reference coordinate system, calculating the section bending moment of the bolt to obtain the internal force of the bolt.

[0012] A high-precision bolt internal force extraction device based on finite element large deformation solution, including a section acquisition module, a grid discretization module, a finite element modeling module and an internal force extraction module, wherein: the section acquisition module is used to establish a solid model according to the geometric dimensions of the bolt, imprint the position of the target section in the solid model, obtain the center of the target section as the initial section center, and cut the imprinted circular line into four equal parts. The grid discretization module is used to arrange nodes at the center of the initial section and the four-section cut respectively, and perform grid discretization on the solid model. The finite element modeling module is used to establish a finite element model of the bolt joint according to the discretized solid model, perform large deformation solution on the finite element model, and obtain calculation results; the internal force extraction module is used to extract the displacement of the center of the initial section based on the calculation results, use the displacement to correct the center position of the target section, and calculate the section bending moment of the bolt to obtain the internal force of the bolt.

[0013] In one embodiment, the internal force extraction module includes a coordinate acquisition unit, a displacement acquisition unit, a coordinate updating unit, a coordinate establishing unit and an internal force calculation unit, wherein: the coordinate acquisition unit is used to select the node at the center of the target section and any two adjacent nodes at the quarter-cutting as the target nodes, and obtain the spatial coordinates of the target nodes; the displacement acquisition unit is used to select the moment of any step of loading as the target moment, and obtain the corresponding calculation result and the spatial displacement corresponding to the target node; the coordinate updating unit is used to calculate the target spatial coordinates of the target node at the target moment according to the spatial coordinates of the target node and the corresponding spatial displacement, and obtain the target center coordinates corresponding to the node at the center of the target section, and the first target coordinates and the second target coordinates corresponding to the nodes at the two adjacent quarter-cuttings; the coordinate establishing unit is used to take the target center coordinates as the origin, and take the first target coordinates and the second target coordinates as the positive directions of the x-axis and the y-axis respectively, to create a three-dimensional rectangular coordinate system as a reference coordinate system; the internal force calculation unit is used to calculate the section bending moment of the bolt based on the target center coordinates and the reference coordinate system to obtain the bolt internal force.

[0014] It can be seen from the above technical solution that the beneficial technical effects of the present invention are as follows:

[0015] 1. Using a solid model for bolt modeling can simulate the stiffness distribution of the bolt joint with high precision, and the extracted internal force of the bolt section is more realistic.

[0016] 2. By establishing a finite element model of the bolt joint to solve the large deformation, the calculation results are obtained. The calculation results are used to compensate for the spatial displacement of the center of the target section of the bolt, and the bolt section bending moment is extracted with this position as the moment center, so that the accuracy of the internal force can be guaranteed.

[0017] 3. By providing a reference coordinate system as a reference, the reference direction of the extracted bolt section bending moment is clear, which facilitates further analysis of the bearing characteristics of the bolt joint based on the extracted cross-sectional internal force data. This can solve the technical problem that when beam units are used for modeling in the prior art, the cross-sectional direction control process of the beam unit is complicated and error-prone, and the cross-sectional direction of the beam unit cannot be intuitively judged, which is not conducive to the subsequent in-depth analysis of the bearing characteristics of the bolt joint. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the prior art description. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0019] Figure 1 A schematic diagram of a process of extracting a high-precision bolt internal force based on a finite element large deformation solution in one embodiment;

[0020] Figure 2 is a schematic diagram of the position of a target cross section in one embodiment;

[0021] Figure 3 is a comparison diagram of the center position of a target cross section in a bolt finite element model in one embodiment;

[0022] Figure 4 A comparison diagram of the center position on the target cross section in one embodiment;

[0023] Figure 5 It is a structural block diagram of a high-precision bolt internal force extraction device based on finite element large deformation solution in one embodiment;

[0024] Figure 6 4 is a structural block diagram of an internal force extraction module in one embodiment. DETAILED DESCRIPTION

[0025] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0026] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0027] In one embodiment, Figure 1 As shown, a high-precision bolt internal force extraction method based on finite element large deformation solution is provided, including:

[0028] S110 establishes a solid model according to the geometric dimensions of the bolt, marks the position of the target section in the solid model, obtains the center of the target section as the initial section center, and cuts the marked circumference into four equal parts.

[0029] In one embodiment, the target cross section in step S110 is a horizontal cross section in the solid model that is moved from the boundary of the thread engagement section along the axial direction to the middle of the bolt by a preset distance.

[0030] Specifically, in step S110, when establishing a solid model according to the geometric dimensions of the bolt, threads and small fillets are not considered. Figure 2 As shown in the figure, generally, the cross section is obtained by moving 5 to 6 mm from the boundary of the threaded engagement section to the middle of the bolt in the axial direction. The center of the target cross section is the center of the initial cross section, as shown in the figure. Figure 3 and Figure 4 As shown in Figure 1, the center of the target section is when the bolt model is not subjected to external load, that is, when the deformation is 0.

[0031] S120 arranges nodes at the center of the initial section and at the quarter-section cuts to discretize the solid model.

[0032] In one embodiment, before the step of meshing the solid model in step S120, the method further includes: randomly arranging a plurality of nodes at positions other than the center and the quarter-section cutting positions in the initial cross section.

[0033] Specifically, the five points at the center of the initial section and the four-division cut are where nodes must be arranged, and multiple nodes are arranged at other subsequent positions to facilitate mesh discretization of the solid model.

[0034] S130 establishes a finite element model of the bolt joint according to the discretized solid model, performs large deformation solution on the finite element model, and obtains calculation results.

[0035] In one embodiment, in step S130, the finite element model is solved for large deformation to obtain calculation results, including: performing multi-step loading processing on the finite element model to obtain the time corresponding to each loading step, the spatial displacement of each node, and the calculation results of the large deformation solution at the corresponding time.

[0036] In one embodiment, the multi-step loading is divided into preload loading and external load loading, wherein the external load loading is divided into multiple load sub-steps.

[0037] Specifically, in step S130, the multi-step loading process is to load the load, and the loading here is often divided into two load steps. The first load step only loads the preload, and the loading process is 0s to 1s. After the loading is completed, the model displacement is locked; the second load step only loads the external load, which is divided into multiple load sub-steps. The loading process is 1s to 2s, and the time corresponding to each sub-step is the focus time. Taking 5 load sub-steps for loading as an example, the focus time is 1.2s, 1.4s, 1.6s, 1.8s, and 2s. This step is performed in the simulation software. After the load is loaded, the corresponding displacement of each node at the corresponding time and the corresponding large deformation calculation results can be obtained.

[0038] S140 extracts the displacement of the center of the initial section based on the calculation results, uses the displacement to correct the center position of the target section, and calculates the section bending moment of the bolt to obtain the internal force of the bolt.

[0039] In one embodiment, step S140 includes: selecting a node at the center of a target section and any two adjacent nodes at four-equal-section cuts as target nodes, and obtaining the spatial coordinates of the target nodes; selecting the moment of any loading step as the target moment, and obtaining the corresponding calculation result and the spatial displacement corresponding to the target node; calculating the target spatial coordinates of the target node at the target moment according to the spatial coordinates of the target node and the corresponding spatial displacement, and obtaining the target center coordinates corresponding to the node at the center of the target section, and the first target coordinates and the second target coordinates corresponding to the nodes at the two adjacent four-equal-section cuts; taking the target center coordinates as the origin, and taking the first target coordinates and the second target coordinates as the positive directions of the x-axis and the y-axis, respectively, to create a three-dimensional rectangular coordinate system as a reference coordinate system; based on the target center coordinates and the reference coordinate system, calculating the section bending moment of the bolt, and obtaining the internal force of the bolt.

[0040] Specifically, in the simulation software, first, enter the post-processor to read the result data at any time in the result file. Here, the focus time mentioned in the specific description of the above step 130 is read. The any time is the time corresponding to any sub-step of loading the external load; then, extract the initial spatial coordinates of the center position node of the bolt section and any two adjacent mark line equally divided cutting position nodes. The initial spatial coordinates are the coordinates when the deformation is 0. The center position node of the bolt section here is the coordinate of the center of the initial section in step S110; then, read the result data at the focus time, and extract the spatial displacement of the above three nodes after loading at that time, and then, as Figure 3 and Figure 4 As shown, based on the initial spatial coordinates of the three nodes and the spatial displacement after loading, the spatial coordinates of the three nodes after loading deformation at this moment are calculated, that is, the target center coordinates corresponding to the nodes at the center of the target section (i.e. Figure 3 and Figure 4), and the first target coordinates and the second target coordinates corresponding to the nodes at the two adjacent quarter-section cuts; then, taking the target center coordinates as the origin, and taking the first target coordinates and the second target coordinates as the positive directions of the x-axis and the y-axis respectively, a three-dimensional rectangular coordinate system is created for reference in the extraction of the internal forces of the bolt section. Finally, the result data of the focus moment in the result file is read again, and the three-dimensional rectangular coordinate system is used as a reference, and the origin of the coordinate system is used as the centroid (the center of the bolt section) to extract the bending moment of the bolt section. The calculation of the bending moment is based on a focus moment (target moment), so specifically, the force arm is calculated according to the external load force loaded at the focus moment in step S130, and the bending moment of the bolt target section is further calculated according to the force arm and the centroid. The section bending moment is also a kind of internal force of the bolt section, so calculating the bolt section bending moment is to extract the internal force of the bolt section. When extracting the bolt section bending moment at a certain focus moment (i.e., the target moment), the first layer of units on either side of the target section are selected for extraction, which can ensure the accuracy of the internal force extraction. The first layer of units such as Figure 2 As shown in the dotted box in , the layer of mesh closest to the upper and lower sides of the target section is the first unit.

[0041] In the above embodiment, a high-precision bolt internal force extraction method based on finite element large deformation solution is provided, which uses a solid model to simulate the bolt to maximize the reflection of the real stiffness of the bolt joint. When extracting the cross-sectional internal force, post-processing means are used to determine the exact spatial position of the cross-sectional center node after loading, and the bolt cross-sectional bending moment is extracted with this position as the moment center, so that the accuracy of the internal force is guaranteed. In addition, by specifying the cross-sectional internal force extraction reference coordinate system, the direction of the extracted bolt cross-sectional bending moment can be intuitively judged, which provides the possibility for further analysis of the bearing characteristics of the bolt joint.

[0042] In one embodiment, Figure 5 As shown, a high-precision bolt internal force extraction device based on finite element large deformation solution is provided, the device includes a cross-section acquisition module 210, a mesh discretization module 220, a finite element modeling module 230 and an internal force extraction module 240, wherein:

[0043] The section acquisition module 210 is used to establish a solid model according to the geometric dimensions of the bolt, mark the position of the target section in the solid model, obtain the center of the target section as the initial section center, and cut the marked circumference into four equal parts.

[0044] The mesh discretization module 220 is used to arrange nodes at the center of the initial section and at the quarter-section cuts to perform mesh discretization on the solid model.

[0045] The finite element modeling module 230 is used to establish a finite element model of the bolt joint according to the discretized solid model, perform large deformation solution on the finite element model, and obtain calculation results;

[0046] The internal force extraction module 240 is used to extract the displacement of the center of the initial section based on the calculation results, use the displacement to correct the center position of the target section, and calculate the section bending moment of the bolt to obtain the internal force of the bolt.

[0047] In one embodiment, Figure 6 As shown, the internal force extraction module 240 includes a coordinate acquisition unit 241, a displacement acquisition unit 242, a coordinate updating unit 243, a coordinate establishing unit 244 and an internal force calculation unit 245, wherein: the coordinate acquisition unit 241 is used to select the node at the center of the target section and any two adjacent nodes at the quarter-section cutting as the target node, and obtain the spatial coordinates of the target node; the displacement acquisition unit 242 is used to select the moment of any step loading as the target moment, and obtain the corresponding calculation result and the spatial displacement corresponding to the target node; the coordinate updating unit 243 is used to calculate the target spatial coordinates of the target node at the target moment according to the spatial coordinates of the target node and the corresponding spatial displacement, and obtain the target center coordinates corresponding to the node at the center of the target section, and the first target coordinates and the second target coordinates corresponding to the nodes at the two adjacent quarter-section cuttings; the coordinate establishing unit 244 is used to take the target center coordinates as the origin, and take the first target coordinates and the second target coordinates as the positive directions of the x-axis and the y-axis respectively, to create a three-dimensional rectangular coordinate system as a reference coordinate system; the internal force calculation unit 245 is used to calculate the section bending moment of the bolt based on the target center coordinates and the reference coordinate system, and obtain the internal force of the bolt.

[0048] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A high-precision bolt internal force extraction method based on finite element large deformation solution, characterized in that: include: A solid model is established according to the geometric dimensions of the bolt, the position of the target section is imprinted in the solid model, the center of the target section is obtained as the initial section center, and the imprinted circumference is cut into four equal parts; Arranging nodes at the center of the initial section and at the quarter-section cuts respectively, and performing mesh discretization on the solid model; According to the discretized solid model, a finite element model of the bolt joint is established, and a large deformation solution is performed on the finite element model to obtain a calculation result; Based on the calculation results, the displacement of the center of the initial section is extracted, the center position of the target section is corrected using the displacement, and the section bending moment of the bolt is calculated to obtain the internal force of the bolt. The step of extracting the displacement of the center of the initial section based on the calculation result to correct the center position of the target section, and calculating the section bending moment of the bolt to obtain the internal force of the bolt includes: Selecting a node at the center of the target section and any two adjacent nodes at the quarter-cutting positions as target nodes, and obtaining the spatial coordinates of the target nodes; Selecting the moment of any loading step as the target moment, and obtaining the corresponding calculation result and the spatial displacement corresponding to the target node; According to the spatial coordinates of the target node and the corresponding spatial displacement, the target spatial coordinates of the target node at the target time are calculated to obtain the target center coordinates corresponding to the node at the center of the target section, and the first target coordinates and the second target coordinates corresponding to the nodes at two adjacent quarter-cuts; Taking the target center coordinates as the origin, taking the first target coordinates and the second target coordinates as the positive directions of the x-axis and y-axis respectively, a three-dimensional rectangular coordinate system is created as a reference coordinate system; Based on the target center coordinates and the reference coordinate system, the cross-sectional bending moment of the bolt is calculated to obtain the bolt internal force.

2. The method according to claim 1, characterized in that The target cross section in the solid model is a horizontal cross section that moves a preset distance from the boundary of the thread engagement section along the axial direction toward the middle of the bolt.

3. The method according to claim 1, characterized in that Before the mesh discretization step is performed on the solid model, the method further includes: A plurality of nodes are randomly arranged at positions other than the center and the quarter-cut positions in the initial cross section.

4. The method according to claim 1, characterized in that: The steps of performing large deformation solution on the finite element model to obtain calculation results include: The finite element model is subjected to multi-step loading processing to obtain the time corresponding to each step of loading, the spatial displacement of each node, and the calculation result of the large deformation solution at the corresponding time.

5. The method according to claim 4, characterized in that The multi-step loading is divided into preload loading and external load loading, wherein the external load loading is divided into a plurality of load sub-steps.

6. A high-precision bolt internal force extraction device based on finite element large deformation solution, characterized in that: It includes section acquisition module, mesh discretization module, finite element modeling module and internal force extraction module, among which: The cross-section acquisition module is used to establish a solid model according to the geometric dimensions of the bolt, mark the position of the target cross-section in the solid model, obtain the center of the target cross-section as the initial cross-section center, and cut the marked circumference into four equal parts; The grid discretization module is used to arrange nodes at the center of the initial section and at the quarter-section cut respectively, and perform grid discretization on the solid model; The finite element modeling module is used to establish a finite element model of the bolt joint according to the discretized solid model, perform large deformation solution on the finite element model, and obtain calculation results; The internal force extraction module is used to extract the displacement of the center of the initial section based on the calculation result, use the displacement to correct the center position of the target section, and calculate the section bending moment of the bolt to obtain the internal force of the bolt. The internal force extraction module includes a coordinate acquisition unit, a displacement acquisition unit, a coordinate update unit, a coordinate establishment unit and an internal force calculation unit, wherein: The coordinate acquisition unit is used to select the node at the center of the target section and any two adjacent nodes at the quarter-cutting positions as the target node, and acquire the spatial coordinates of the target node; The displacement acquisition unit is used to select the moment of any loading step as the target moment, and obtain the corresponding calculation result and the spatial displacement corresponding to the target node; The coordinate updating unit is used to calculate the target spatial coordinates of the target node at the target time according to the spatial coordinates of the target node and the corresponding spatial displacement, and obtain the target center coordinates corresponding to the node at the center of the target section, and the first target coordinates and the second target coordinates corresponding to the nodes at two adjacent quarter-cuts; The coordinate establishing unit is used to create a three-dimensional rectangular coordinate system as a reference coordinate system, taking the target center coordinate as the origin and the first target coordinate and the second target coordinate as the positive directions of the x-axis and the y-axis respectively; The internal force calculation unit is used to calculate the cross-sectional bending moment of the bolt based on the target center coordinates and the reference coordinate system to obtain the bolt internal force.

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