Method for converting geometric model into finite element model

Abstract

The invention provides a method for converting a geometric model into a finite element model. The method comprises the following steps: obtaining an IGS format file of a geometric model, importing the IGS format file into finite element preprocessing software, repairing the geometric model to form a preprocessing model, carrying out grid division on the preprocessing model, and outputting a grid finite element file, the grid finite element text file comprises a finite element file of a curved surface structure and a finite element file of a curve structure, performing batch processing on the finite element file of the curved surface structure and the finite element file of the curve structure to form a model file, and importing the model file into the finite element analysis software to form a finite element model. According to the method, the deviation between the finite element model and the original geometric model caused by the contradiction between the irregularity of the geometric features of the spatial free-form surface geometric model and the regularity of the finite element grid can be reduced, the precision of the finite element model is improved, and a basis is provided for mechanical calculation and structural safety evaluation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of civil engineering, and particularly relates to a method for converting a geometric model into a finite element model. BACKGROUND

[0002] Finite element analysis is a simulation method based on mathematics and computer technology, which is used to simulate and analyze the structure and behavior of objects. It divides the actual object into many small finite element units, establishes a mathematical model, and uses computer algorithms for simulation and analysis to predict and evaluate the strength, deformation and other performance of the object. Finite element analysis is widely used in engineering field, and has important significance and role. Finite element model is a model established by using finite element analysis method, and finite element model is a digital tool for converting continuous physical problems into calculable algebraic equation groups through discrete approximation.

[0003] With the rapid development of domestic economy, a large number of space special-shaped structures have emerged in various places in China. How to convert the geometric model of such space free-form surface into a finite element model is the basis for realizing mechanical calculation and structural safety evaluation. SUMMARY The technical problem to be solved by the present application is to provide a method for converting a geometric model into a finite element model, which provides a basis for realizing mechanical calculation and structural safety evaluation.

[0004] In order to solve the above problems, the present application provides a method for converting a geometric model into a finite element model, comprising: obtaining an IGS format file of a geometric model and importing it into a finite element preprocessing software, wherein the IGS format file comprises a curved surface structure file and a curved line structure file; repairing the geometric model based on the finite element preprocessing software to form a preprocessing model, and the repairing contents include connection area repair of T-shaped surface of curved line structure and curved surface structure, compression feature angle repair, distance control of repeated surface and cutting distance control; performing mesh division on the preprocessing model based on the finite element preprocessing software and outputting a mesh finite element file, wherein the mesh finite element file comprises a finite element file of curved surface structure and a finite element file of curved line structure; batch processing the finite element file of curved surface structure and the finite element file of curved line structure to form a model file, wherein the model file comprises a frame file, a node file and a shell file; and importing the model file into a finite element analysis software to form a finite element model.

[0005] In some embodiments, the step of meshing the pretreatment model and outputting a mesh finite element file further comprises: meshing the pretreatment model to form a mesh model, the mesh model comprising nodes and elements; performing mesh cleaning on the mesh model; checking the mesh quality of the mesh model after mesh cleaning, and outputting the mesh model as a mesh finite element file when the mesh quality of the mesh model meets preset conditions.

[0006] In some embodiments, the mesh cleaning of the mesh model specifically comprises: setting a node distance threshold, and merging nodes with a distance less than the node distance threshold; setting an element size threshold, and deleting elements with a size less than the element size threshold in the common node operation.

[0007] In some embodiments, during mesh cleaning, a column top node distance threshold and a beam common node distance threshold are set respectively, nodes of the mesh model with a distance less than the column top node distance threshold are merged, and nodes in the beam common nodes of the mesh model with a distance less than the beam common node distance threshold are merged.

[0008] In some embodiments, in the step of checking the mesh quality of the mesh model after mesh cleaning, when the mesh quality of the mesh model does not meet the preset conditions, the following steps are performed: re-meshing the pretreatment model to form a new mesh model; performing mesh cleaning on the new mesh model; checking the mesh quality of the new mesh model after mesh cleaning, and outputting the new mesh model as a mesh finite element file when the mesh quality of the new mesh model meets preset conditions.

[0009] In some embodiments, the IGS format file of the geometric model is obtained by using AutoCAD software or Rhino software.

[0010] In some embodiments, the finite element pretreatment software is HyperMesh software, and the finite element analysis software is SAP2000.

[0011] In some embodiments, the extension name of the mesh finite element file is.inp.

[0012] In some embodiments, based on an AutoLISP language program, the finite element files of the curved surface structure and the finite element files of the curved line structure are batch processed by using an HMTOSAP plug-in.

[0013] In some embodiments, the model file is in EXCEL format. The technical scheme is characterized in that: an IGS format file of a geometric model is acquired and imported into finite element preprocessing software, the geometric model is repaired to form a preprocessing model, the preprocessing model is meshed and a mesh finite element file is output, the mesh finite element file includes a finite element file of a curved surface structure and a finite element file of a curved line structure, the finite element file of the curved surface structure and the finite element file of the curved line structure are batch processed to form a model file, and the model file is imported into the finite element analysis software to form a finite element model.

[0014] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can be used without detail here, but where appropriate, such techniques, methods, and apparatus should be considered as part of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those of ordinary skill in the art without creative effort based on these drawings.

[0016] Figure 1 is a flow chart of a method for converting a geometric model into a finite element model provided by an embodiment of the present application; Figure 2 is a display diagram of an IGS format file of a geometric model imported into finite element preprocessing software according to an embodiment of the present application; Figure 3 is a display diagram of a step of meshing a preprocessing model in the finite element preprocessing software according to an embodiment of the present application; Figure 4 is a display diagram of a step of mesh cleaning of a mesh model in the finite element preprocessing software according to an embodiment of the present application; Figure 5 is a display diagram of a step of outputting a mesh model as a mesh finite element file in the finite element preprocessing software according to an embodiment of the present application. DETAILED DESCRIPTION

[0017] Clearly, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0018] Please refer to Figures 1-5 , Figure 1 is a flow chart of a method for converting a geometric model into a finite element model provided by an embodiment of the present application; Figure 2 is a display diagram of an IGS format file of a geometric model imported into a finite element preprocessing software provided by an embodiment of the present application; Figure 3 is a display diagram of a step of meshing a preprocessing model in the finite element preprocessing software provided by an embodiment of the present application; Figure 4 is a display diagram of a step of mesh cleaning a mesh model in the finite element preprocessing software provided by an embodiment of the present application; Figure 5 is a display diagram of a step of outputting a mesh model into a mesh finite element file in the finite element preprocessing software provided by an embodiment of the present application.

[0019] As shown in Figure 1 , the method for converting a geometric model into a finite element model comprises the following steps.

[0020] Step S11, an IGS format file of a geometric model is acquired and imported into a finite element preprocessing software, and the IGS format file contains a curved surface structure file and a curved line structure file.

[0021] The initial graphics exchange specification (IGES) format file is a three-dimensional data exchange format based on the IGES standard, and is mainly used for model transmission between different computer aided design (CAD) software. The IGS format file is not constrained by specific CAD software, and thus can support cross-platform transmission (such as AutoCAD, SolidWorks, CATIA, Rhino, etc.). The extension name of the IGS format file is.igs or.iges.

[0022] The present embodiment is mainly used for converting a spatial free curved surface geometric structure model into a finite element model. Correspondingly, in the present step, the AutoCAD software or the Rhino software is used to acquire the IGS format file of the geometric model. In the IGS format file, the curved surface structure file contains curved surface structure geometric elements, which are two-dimensional elements; and the curved line structure file contains curved line structure geometric elements, which are one-dimensional elements.

[0023] In this step, the finite element preprocessing software is HyperMesh software. The HyperMesh software has functions of geometry processing and meshing, and supports custom scripts. As shown in Figure 2 In the HyperMesh software, the geometric model is displayed in the form of surfaces and curves.

[0024] In step S12, the geometric model is repaired to form a preprocessing model based on the finite element preprocessing software. The repair content includes connection area modification of T-shaped surfaces of curve structure and surface structure, repair of compression feature angle, distance control of repeated surfaces, and cutting distance control.

[0025] In step S11, the geometric model has been imported into the finite element preprocessing software by importing the IGS format file. In this step, the geometric model is repaired based on the Geometry Fix function of the HyperMesh software.

[0026] The T-shaped surface of the curve structure and the surface structure refers to the surface formed when the curve member (such as a beam, a rod, a curve frame, etc.) and the surface member (such as a shell, a thin plate, a curved wall, etc.) intersect in the form of a “T” letter; the compression feature angle refers to an angle less than which an intersecting surface is divided into a unit as a surface.

[0027] The preprocessing model formed after the repair of the geometric model is checked to ensure that the preprocessing model has no errors, for example, the preprocessing model is checked to ensure that the preprocessing model is geometrically continuous.

[0028] In step S13, the preprocessing model is meshed based on the finite element preprocessing software, and a mesh finite element file is output. The mesh finite element file includes a finite element file of the surface structure and a finite element file of the curve structure.

[0029] This step is performed by the finite element preprocessing software. This step further includes: step S131, meshing the preprocessing model to form a mesh model, the mesh model including nodes and elements; step S132, mesh cleaning the mesh model; step S133, checking the mesh quality of the mesh model after mesh cleaning, and outputting the mesh model as a mesh finite element file when the mesh quality of the mesh model meets a preset condition.

[0030] Step S131 further includes setting parameters such as the size of the element and the type of the element in a specific interface of the finite element preprocessing software, and automatically generating a mesh by the finite element preprocessing software after selecting a specific surface.

[0031] As shown in Figure 3As shown in the figure, the shape of the mesh after meshing in the HyperMesh software is the same for different regions.

[0032] Step S132 specifically includes: (1) setting a node distance threshold, and merging nodes with a distance less than the node distance threshold; (2) setting a cell size threshold, and deleting cells with a size less than the cell size threshold in the common node operation.

[0033] The node distance threshold can be set for different regions. In this embodiment, a column top node distance threshold and a beam common node distance threshold are set respectively, and nodes of the grid model with a distance less than the column top node distance threshold are merged, and nodes in the beam common node of the grid model with a distance less than the beam common node distance threshold are merged.

[0034] In this embodiment, the finite element preprocessing software is HyperMesh software, and a cell size threshold is input in a related setting interface when the common node operation is performed in the HyperMesh software. The software automatically detects cells in the model, and identifies cells with a size less than the set threshold. When the common node operation is performed, these cells less than the threshold are deleted as cells that do not meet the requirements. Further, it is ensured that different elements or cells can be correctly connected, and the grid quality and calculation efficiency are optimized. As shown in the figure, the shape of the grid model after mesh cleaning in the HyperMesh software is shown. In the topology display mode, the surface shape is distinguished by different colors, and the modification effect is intuitively reflected. Figure 4

[0035] In step S133, the grid quality of the grid model is checked by Mesh Clean. The preset conditions include the geometric shape quality, type, connection logic and consistency with the geometric model of the cell.

[0036] The grid finite element file includes a finite element file of a curved surface structure and a finite element file of a curved line structure. The extension name of the grid finite element file is.inp. The.inp format file is a general format of finite element analysis, which can be supported by multiple finite element software, and the.inp format file is a pure text file, which can be opened and modified by multiple text editors, and is suitable for rapid modification of model parameters. In this embodiment, the grid finite element text file includes a finite element file shell.inp of a curved surface structure and a finite element file T1D.inp of a curved line structure.

[0037] ​The T1D unit is a tracking unit, which is divided into grid units for two parts of in-plane and out-of-plane lines (One-D_elements_InShell and One-D_elements_OutOfShell), and the part is used as a one-dimensional unit template for later executable program to delete useless units.

[0038] When the grid quality of the grid model does not satisfy the preset condition, the following steps are performed: 1) re-meshing the pretreatment model to form a new grid model; 2) performing grid cleaning on the new grid model; 3) checking the grid quality of the new grid model after grid cleaning, and when the grid quality of the new grid model satisfies the preset condition, outputting the new grid model as a grid finite element file. That is, steps S131-S133 are iteratively performed until the grid quality of the new grid model satisfies the preset condition, and the new grid model is output as a grid finite element file.

[0039] As shown in FIG. 1, Figure 5 Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 In the HyperMesh software, when the Output Mesh function is used to generate a finite element file, geometric elements such as surfaces, curves and free points are displayed in different colors, and finally the finite element file shell.inp of the surface structure and the finite element file T1D.inp of the curve structure are exported.

[0040] In step S14, the finite element file of the surface structure and the finite element file of the curve structure are batch processed to form a model file, and the model file includes a frame file, a node file and a shell file.

[0041] In this step, based on the AutoLISP language program, the finite element file of the surface structure and the finite element file of the curve structure are batch processed by using the HMTOSAP plug-in.

[0042] The model file formed is in EXCEL format, specifically, the extension of the model file is.xls or.xlsx. The frame file is used to store frame unit information, the node file is used to store node information, and the shell file is used to store shell unit information. In this embodiment, the model file formed includes a frame file frame.xls, a node file node.xls and a shell file shell.xls. The format of the model file can be used for finite element analysis software.

[0043] In this step, the finite element analysis software is SAP2000. Correspondingly, the AutoLISP language program is used to convert the inp format file generated in step S13 into a file in.xls or other EXCEL format which can be directly read by the SAP2000 software, and the HMTOSAP plug-in is used to realize batch processing.

[0044] Step S15, importing the model file into the finite element analysis software to form a finite element model. Importing the frame file, the node file and the shell file into the finite element analysis software, i.e. realizing the conversion of the geometric model into the finite element model. The generated finite element model file has an extension of.sdb.

[0045] The technical solution described above, by obtaining an IGS format file of a geometric model and importing it into a finite element preprocessing software, repairing the geometric model to form a preprocessing model, performing meshing on the preprocessing model and outputting a mesh finite element file, the mesh finite element file including a finite element file of a curved surface structure and a finite element file of a curved line structure, batch processing the finite element file of the curved surface structure and the finite element file of the curved line structure to form a model file, and importing the model file into the finite element analysis software to form a finite element model. The method described above can reduce the deviation between the finite element model and the original geometric model caused by the contradiction between the irregularity of the geometric features of the spatial free-form surface geometric model and the regularity of the finite element mesh, and improve the accuracy of the finite element model, thereby providing a basis for mechanical calculation and structural safety evaluation.

[0046] It should be noted that, in this document, relational terms such as“first” and“second”, and the like, are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between or among entities or actions. Moreover, the terms“comprises”,“comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process or method. Embodiments of the present application are described herein with reference to the accompanying drawings, which are used to illustrate specific embodiments of the application. In the drawings, like reference numerals refer to like elements throughout the various drawings. Embodiments of the present application will be described with reference to the accompanying drawings, in which:

[0047] The above description is merely preferred embodiments of the present application, and is not intended to limit the protection scope of the present application. It should be noted that, for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method of converting a geometric model into a finite element model, characterized by, The method comprises the following steps: acquiring an IGS format file of a geometric model and importing the IGS format file into finite element preprocessing software, wherein the IGS format file comprises a curved surface structure file and a curved line structure file; repairing the geometric model based on the finite element preprocessing software to form a pretreatment model, wherein the repairing comprises repairing a connection area of a T-shaped surface of the curved surface structure and the curved line structure, repairing a feature angle, distance control of a repeated surface and cutting distance control; dividing the pretreatment model into meshes based on the finite element preprocessing software and outputting a mesh finite element file, wherein the mesh finite element file comprises a finite element file of the curved surface structure and a finite element file of the curved line structure; batch processing the finite element file of the curved surface structure and the finite element file of the curved line structure to form a model file, wherein the model file comprises a frame file, a node file and a shell file; and importing the model file into finite element analysis software to form a finite element model.

2. The method of claim 1, wherein, The step of dividing the pretreatment model into meshes and outputting a mesh finite element file further comprises: dividing the pretreatment model into meshes to form a mesh model, wherein the mesh model comprises nodes and elements; performing mesh cleaning on the mesh model; checking the mesh quality of the mesh model after the mesh cleaning; and outputting the mesh model as a mesh finite element file when the mesh quality of the mesh model meets preset conditions.

3. The method of claim 2, wherein, The mesh cleaning on the mesh model specifically comprises: setting a node distance threshold value and merging nodes with a distance less than the node distance threshold value; and setting an element size threshold value and deleting elements with a size less than the element size threshold value in a common node operation.

4. The method of claim 3, wherein, In the mesh cleaning, a column top node distance threshold value and a beam common node distance threshold value are respectively set, nodes of the mesh model with a distance less than the column top node distance threshold value are merged, and nodes in the beam common nodes of the mesh model with a distance less than the beam common node distance threshold value are merged.

5. The method of claim 2, wherein, In the step of checking the mesh quality of the mesh model after the mesh cleaning, when the mesh quality of the mesh model does not meet preset conditions, the following steps are performed: re-dividing the pretreatment model into meshes to form a new mesh model; performing mesh cleaning on the new mesh model; checking the mesh quality of the new mesh model after the mesh cleaning; and outputting the new mesh model as a mesh finite element file when the mesh quality of the new mesh model meets preset conditions.

6. The method of claim 1, wherein, The IGS format file of the geometric model is acquired by using AutoCAD software or Rhino software.

7. The method of claim 1, wherein, The finite element preprocessing software is HyperMesh software, and the finite element analysis software is SAP2000.

8. The method of claim 1, wherein, The extension name of the mesh finite element file is.inp.

9. The method of claim 1, wherein, The finite element file of the curved surface structure and the finite element file of the curved line structure are batch processed by using an HMTOSAP plug-in based on an AutoLISP language program.

10. The method of claim 1, wherein, The model file is in an EXCEL format.

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