CN114547799A - High-stability finite element mesh dividing method for hot chamber die casting - Google Patents
High-stability finite element mesh dividing method for hot chamber die casting Download PDFInfo
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Abstract
The invention provides a high-stability finite element mesh subdivision method for a hot chamber die casting, which comprises the following steps of: step S1, reading the model file and setting parameters; step S2, judging whether the grid size is suitable, if so, executing step S3, otherwise, ending; step S3, dividing cubic grids; step S4, dividing a face grid; step S5, sticking the surface mesh to the surface of the model by adopting a body-sticking algorithm; step S6, generating a tetrahedral mesh by using the triangular mesh; and step S7, outputting the grid file.
Description
Technical Field
The invention relates to the technical field of industrial design, in particular to a high-stability finite element mesh subdivision method for a hot chamber die casting.
Background
In the calculation of the finite element, the meshing quality of the part has obvious influence on the solving precision of the finite element, so that the good meshing has important significance in the finite element analysis process. The hot chamber die casting has the advantages of large wall thickness variation range of the casting, complex parts and more detail characteristics, and provides higher requirements for a finite element mesh subdivision method. At present, a finite element meshing method is divided based on geometric files, and the method has poor stability for complex geometric files; the grid size of the thin-wall parts is difficult to control; if the division is carried out manually, the efficiency is often lower, and meanwhile, higher requirements are given to operators, so that the popularization is difficult.
Disclosure of Invention
The object of the present invention is to solve at least one of the technical drawbacks mentioned.
Therefore, the invention aims to provide a high-stability finite element mesh subdivision method for a hot-chamber die casting, so as to solve the problems mentioned in the background technology and overcome the defects in the prior art.
In order to achieve the above object, an embodiment of the present invention provides a high-stability finite element mesh partitioning method for hot-chamber die casting, comprising the steps of:
step S1, reading the model file and setting parameters;
step S2, judging whether the grid size is suitable, if so, executing step S3, otherwise, ending;
step S3, dividing cubic grids;
step S4, dividing a face grid;
step S5, sticking the surface mesh to the surface of the model by adopting a body-sticking algorithm;
step S6, generating a tetrahedral mesh by using the triangular mesh;
and step S7, outputting the grid file.
Preferably, in any of the above schemes, in step S1, a configuration file and model information are imported, wherein the configuration file includes: the method comprises the following steps of (1) carrying out surface mesh size and maximum volume mesh size, wherein the surface mesh size is used for representing the size of a 2D mesh of a part, and the maximum volume mesh size is used for representing the size of a maximum 3D mesh; the model information is a model file.
In any of the above embodiments, in step S3, the part is divided into cubic meshes by a threading method according to the STL model of the part, and the mesh size is the face mesh file size set in the configuration file.
Preferably, in step S2, the average thickness t of the part is set to V/a, where V is the volume of the part and a is the surface area of the part, and if the mesh size is larger than the average thickness t, the mesh size is considered to be too large and not suitable, otherwise, the mesh size is considered to be suitable.
Preferably, in any of the above schemes, the STL file is composed of a series of triangular patches, and the closed space composed of the triangular patches is the geometric body of the part; a series of ray clusters are generated by adopting a threading method, intersection points of rays and triangular patches in the STL are solved, and cubic grids are generated among the intersection points.
Preferably, in step S4, the Marching Cube algorithm is used to divide the surface mesh, wherein the vertices of all cubes are divided into two groups, one group is inside the STL and the other group is outside the STL; and then generating a corresponding face mesh according to the rules of the Marching Cube algorithm and the combination of vertexes of different types of cubes.
Preferably, in step S7, a tetrahedral mesh is generated through a triangular mesh by using a 3DDelaunay algorithm according to the generated face mesh, and a maximum tetrahedral mesh size is specified in a configuration file, so as to obtain a final mesh.
The invention provides an automatic, efficient and stable finite element mesh subdivision method for a hot chamber die-casting part, which has the following beneficial effects:
(1) the size of the grid can be freely controlled, and the fine structure of the part can be automatically filtered;
(2) the robustness is strong, and a finite element grid with high quality can be generated for any complex part;
(3) the method is simple and efficient, and the finite element mesh can be generated quickly only by specifying the mesh size.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a flow chart of a high stability finite element mesh partitioning method for hot-chamber die castings according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a cassette model according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a part volume mesh partitioning according to an embodiment of the present invention;
FIG. 4 is a schematic illustration of a face mesh repartitioning according to an embodiment of the present invention;
FIG. 5 is a schematic view of a face grid skin in accordance with an embodiment of the present invention;
FIG. 6 is a schematic diagram of volume mesh generation according to an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
Different from the traditional finite element division algorithm, the method adopts the generation process of the volume mesh-surface mesh-volume mesh, and develops a finite element mesh division algorithm with strong robustness, simple technical route, high efficiency and controllability. The method mainly solves the problems that the prior finite element mesh generation depends on manpower and has lower efficiency, and effectively helps a finite element application technician to obtain the finite element mesh of the geometric body as simply as possible.
As shown in FIG. 1, the method for subdividing the high-stability finite element mesh for the hot-chamber die casting of the embodiment of the invention comprises the following steps:
step S1, reading the model file and setting parameters.
Specifically, a configuration file and model information are imported, an initial surface mesh size and a maximum volume mesh generation size are specified in the configuration file, and an STL file needing to subdivide a finite element mesh is read in at the same time.
The configuration file mainly comprises two parameters: the two parameters respectively describe the size of the 2D grid and the size of the maximum 3D grid of the part.
Further, the model information is a model file, and here, an STL file is selected. As shown in fig. 2, a die-cast part of a case has a thin wall portion and a thick wall portion, and it is very difficult to actually divide a mesh.
The process from the STL model to the final finite element mesh generation will be described below, taking the part as an example. First, it is necessary to check whether the parameters are reasonable. In the meshing, the mesh size of the surface is not larger than the minimum wall thickness of the part. Once above the minimum wall thickness, the thinnest wall may suffer from hole defects, causing severe damage to the part geometry. If this occurs, the calculation is stopped and the parameters are reset.
And step S2, judging whether the grid size is proper, if so, executing step S3, and if not, ending.
Specifically, assuming that the average thickness t of the part is equal to V/a, where V is the volume of the part and a is the surface area of the part, if the mesh size is larger than the average thickness t, the mesh size is considered to be too large and not suitable, otherwise, the mesh size is considered to be suitable.
Step S3, a cubic grid is divided.
Specifically, according to the STL model of the part, the size of the set grid is set, the part is divided into cubic grids by adopting a threading method, and a series of cubic grids are obtained, wherein the grid size is the size of a face grid file set in the configuration file. Fig. 3 is a schematic diagram of volume meshing, and the STL file is composed of a series of triangular patches, and the closed space formed by the triangular patches is the geometric volume of the part. In order to reduce the space of the model file, the size of the triangular patch in the STL file is very uneven, and the lattice cannot be directly generated by the STL triangular patch. A series of ray clusters are generated by using a threading method, intersection points of rays and triangular patches in the STL are obtained, and cubic grids are generated between the intersection points, as shown in fig. 3.
And step S4, dividing the surface grid.
And (3) intersecting the obtained square grid array with an STL model to obtain uniform and fine triangular patches and generate fine and smooth surface grids.
Specifically, the Marching Cube algorithm is adopted to calculate the interface between the volume mesh and the STL file to obtain a fine volume mesh, as shown in fig. 4. All the cube vertices were grouped into two groups, one inside the STL and one outside the STL. And then generating a corresponding face mesh according to the rules of the Marching Cube algorithm and the combination of vertexes of different types of cubes. The new face grid surface is sufficiently detailed to have a better description of some geometric features.
And step S5, sticking the surface mesh to the surface of the model by adopting a body sticking algorithm.
Specifically, a triangular patch is subjected to skin treatment, and a step effect caused by square mesh division is eliminated.
For the newly generated surface mesh, the step features of the volume mesh still remain on some planes, so the positions of the mesh points need to be corrected to ensure that all the surface mesh points are on the model provided by the source STL.
During the calculation, each point (a 'and B') is found, for example, the point A, B, which is closest to the STL model, and then the points a and B are moved to the corresponding points a 'and B'. As shown in fig. 5, the surface mesh has obvious steps before correction, and the steps of the surface mesh disappear after correction, so that the whole surface mesh is smoother, and a foundation is laid for generation of a high-quality three-dimensional mesh.
And step S6, generating a tetrahedral body mesh by using the triangular surface mesh.
And step S7, outputting the grid file.
Specifically, according to the generated face mesh, a tetrahedral body mesh is generated through a triangular face mesh by using a 3D Delaunay algorithm, and the maximum tetrahedral body mesh size is specified in a configuration file, so as to obtain a final lifting mesh, as shown in fig. 6. In the thin plate and the thick place, the finite element mesh can be generated with high quality, and the mesh is preserved, namely the mesh can be used for finite element calculation.
The invention provides an automatic, efficient and stable finite element mesh division method for hot-chamber die-casting parts, which has the advantages of high mesh quality, suitability for finite element calculation, strong robustness, suitability for finite element mesh division of various STL mesh files, and especially more obvious robustness advantage of division for die-casting parts. In conclusion, the invention has the following beneficial effects:
(1) the size of the grid can be freely controlled, and the fine structure of the part can be automatically filtered;
(2) the robustness is strong, and a finite element grid with high quality can be generated for any complex part;
(3) the method is simple and efficient, and the finite element mesh can be generated quickly only by specifying the mesh size.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
It will be understood by those skilled in the art that the present invention includes any combination of the summary and detailed description of the invention described above and those illustrated in the accompanying drawings, which is not intended to be limited to the details and which, for the sake of brevity of this description, does not describe every aspect which may be formed by such combination. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (7)
1. A method for subdividing a high-stability finite element mesh for a hot-chamber die casting is characterized by comprising the following steps of:
step S1, reading the model file and setting parameters;
step S2, judging whether the grid size is suitable, if so, executing step S3, otherwise, ending;
step S3, dividing cubic grids;
step S4, dividing a face grid;
step S5, sticking the surface mesh to the surface of the model by adopting a body-sticking algorithm;
step S6, generating a tetrahedral mesh by using the triangular mesh;
and step S7, outputting the grid file.
2. The method of high stability finite element meshing for hot-chamber die castings according to claim 1, wherein in step S1, configuration files and model information are imported, wherein the configuration files comprise: the method comprises the following steps of (1) carrying out surface mesh size and maximum volume mesh size, wherein the surface mesh size is used for representing the size of a 2D mesh of a part, and the maximum volume mesh size is used for representing the size of a maximum 3D mesh; the model information is a model file.
3. The method of claim 1, wherein in step S2, the average thickness t of the part is set to V/a, where V is the volume of the part and a is the surface area of the part, and if the mesh size is larger than the average thickness t, the mesh size is deemed to be too large and not suitable, otherwise the mesh size is deemed to be suitable.
4. The high-stability finite element mesh division method for a hot-chamber die casting according to claim 1, wherein in said step S3, the part is divided into cubic meshes by a wire method according to the STL model of the part, and the mesh size is the face mesh file size set in the configuration file.
5. The method of high stability finite element meshing for hot-chamber die castings according to claim 4, wherein the STL file is comprised of a series of triangular patches, the enclosed space comprised of triangular patches being the geometry of the part; a series of ray clusters are generated by adopting a threading method, intersection points of rays and triangular patches in the STL are solved, and cubic grids are generated among the intersection points.
6. The high stability finite element mesh partitioning method for hot-chamber die castings according to claim 1, wherein in said step S4, a Marching Cube algorithm is used to partition the face mesh, wherein vertices of all cubes are divided into two groups, one group inside the STL and one group outside the STL; and then generating a corresponding face mesh according to the rules of the Marching Cube algorithm and the combination of vertexes of different types of cubes.
7. The method of subdividing a high stability finite element mesh for a hot-chamber die casting as claimed in claim 1, wherein in said step S7, a tetrahedral mesh is generated by using a 3D Delaunay algorithm through a triangular mesh based on said generated face mesh, and a maximum tetrahedral mesh size is specified in a configuration file to obtain a final mesh.
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| CN116011151A (en) * | 2023-03-27 | 2023-04-25 | 北京适创科技有限公司 | Casting thickness cloud picture determination method, device, equipment and medium |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116011151A (en) * | 2023-03-27 | 2023-04-25 | 北京适创科技有限公司 | Casting thickness cloud picture determination method, device, equipment and medium |
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