JPH10208079A - Method and device for generating analytical mesh - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device for generating analytical mesh which unites hexahedron mesh and tetrahedron mesh without making free sides by using a quadrangular pyramid-shaped mesh at a connecting part of hexahedron mesh and tetrahedron mesh and improves accuracy without increasing calculation quantity. SOLUTION: An inputting means 3 inputs data about a shape model, and an analyzing processor 1 generates analyzing mesh in which hexahedron mesh and tetrahedron mesh coexist based on the inputted data. The processor 1 creates a shape model for an analysis object, retrieves a shape model inputting part 11 for designating a generation area of the hexahedron mesh and generating hexahedron mesh and the hexahedron mesh adjacent to a tetrahedron, arranges quadrangular pyramid mesh on the surface and furthermore, has an automatic mesh generating part 12 for generating tetrahedron mesh in an area in contact with the quadrangular pyramid mesh.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for generating mesh data required for finite element analysis in a numerical analysis simulation of a structure or the like, and particularly to a hexahedral mesh for analyzing a structure having a complicated shape. TECHNICAL FIELD The present invention relates to a method and an apparatus for generating an analysis mesh for generating mesh data in which the mesh data is mixed with a tetrahedral mesh.

[0002]

2. Description of the Related Art For example, when the strength of a structure is calculated by a finite element method using a computer, the analysis is performed by expressing a three-dimensional region to be analyzed as a collection of hexahedral or tetrahedral finite elements. Done. The vertices of the finite element are connected to points called nodes, and adjacent elements are connected via the nodes. A set of elements and nodes is called a mesh, and data representing this mesh is called mesh data. The mesh generation includes a method of generating a hexahedral mesh suitable for handling a simple shape and a method of generating a tetrahedral mesh suitable for generating a mesh in a region having a complicated shape. Conventionally, mesh generation has been performed using only one of a hexahedral mesh and a tetrahedral mesh generation method. In other words, if the accuracy of analysis is prioritized, a hexahedral mesh must be used even if a great deal of effort is spent. To automatically generate a mesh, a tetrahedral mesh must be used even at the expense of analysis accuracy. Was.

If it is possible to generate a mesh in a state where a hexahedral mesh and a tetrahedral mesh are mixed, mesh data with high analysis accuracy can be generated with a small amount of labor. To realize this, Japanese Patent Application Laid-Open No. 8-166 is used.
No. 29, there is a "method and apparatus for creating a mesh for analysis". In the mesh creation method shown here, after dividing the whole into a plurality of partial regions, a hexahedral mesh is created for each partial region, and a tetrahedral mesh is created for a portion where the hexahedral mesh could not be created. And 6
In a region where the tetrahedral mesh and the tetrahedral mesh are adjacent to each other, two tetrahedral meshes facing each other along one diagonal line of the hexahedral mesh are arranged on the surface of the hexahedral mesh.

In addition, a quadratic hexahedral mesh and a quadratic tetrahedral mesh (each having a node at the center of the mesh ridge line) are used, and any of the hexahedral meshes is provided at the joint surface with the hexahedral mesh. Nodes on the sides of the tetrahedral mesh that are not shared with the sides are represented by MPC (Multi-Point Constrai
nts: multipoint constraint = constrain the motion of a certain node by the motion of another node). Donald Dewhirst, Sreedhar Vangavolu, Har
`` The Combination of Hexahedral by ley Wattrick
and Tetrahedral Meshing Algorithm '' (SANDIA REPOR
T, SAND95-2130, p.291-p.304, Sandia National L
aboratories).

[0005]

However, in the prior art for generating a mesh in a state in which the hexahedral mesh and the tetrahedral mesh are mixed, any one of the hexahedral meshes is provided at the joint surface with the hexahedral mesh. There is a side (free side) of the tetrahedral mesh that is not shared with the side. For this reason, when analyzing, there is a problem that a gap or mesh interference occurs on the joint surface. Further, as described above, in the method of constraining the free side using MPC, the constraint on the displacement of the follower point is obtained by approximating the displacement of the main node group using the shape function, thereby increasing the amount of calculation. Further, depending on the degree of deformation of the mesh, there is a possibility that the joint is unnecessarily restricted, and the analysis result may be inaccurate.

An object of the present invention is to increase the amount of calculation by joining a hexahedral mesh and a tetrahedral mesh without forming free sides by using a quadrangular pyramid-shaped mesh at the joint between the hexahedral mesh and the tetrahedral mesh. An object of the present invention is to provide a method and an apparatus for generating a mesh for analysis which can improve the accuracy without performing.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a hexahedral mesh having a surface constituted by six tetragonal faces and a four-sided mesh having a surface constituted by four triangular faces. A quadrangular pyramid mesh having one surface as a quadrilateral surface and the other four surfaces as a triangular surface is arranged at a connection portion with the face mesh.
Disclosed is a method of generating a mesh for analysis in which a tetragonal surface of a pyramid mesh is connected to a tetragonal surface of the hexahedral mesh, and a triangular surface of the tetrahedral mesh is connected to a triangular surface of the tetrahedral mesh. According to this method, the hexahedral mesh and the tetrahedral mesh can be joined while maintaining the consistency of the nodes by disposing the tetragonal pyramid mesh at the connecting portion between the hexahedral mesh and the tetrahedral mesh. If the quadrangular pyramid mesh has the same phase structure as the hexahedral mesh, analysis using an analysis program that does not support the quadrangular pyramid mesh becomes possible.

Further, in order to achieve the above object, the present invention provides a region capable of generating a hexahedral mesh having a surface constituted by six tetragonal surfaces and a surface constituted by four triangular surfaces. A method for generating a mesh for analysis in which a region capable of generating a tetrahedral mesh is connected, wherein a hexahedral mesh is generated in a region capable of generating a hexahedral mesh,
A tetragonal pyramid mesh in which one surface is a quadrilateral and the other four surfaces are triangular is arranged on the surface of the hexahedral mesh adjacent to the tetrahedral mesh, and then a tetrahedral mesh is placed on the triangular surface of the tetrahedral mesh. A method for generating a mesh for analysis that generates a tetrahedral mesh in an area where the tetrahedral mesh can be generated after the arrangement is disclosed. According to this method, after generating a hexahedral mesh, a tetragonal pyramid mesh is connected to this surface,
Thereafter, a tetrahedral mesh is generated in a region where a tetrahedral mesh is to be generated. In this way, by automatically generating a hexahedral mesh and then arranging a quadrangular pyramid mesh as an intermediate product, it becomes possible to automate the generation of the mesh.

Further, in order to achieve the above object, the present invention is an analysis mesh generation apparatus for generating mesh data for finite element analysis based on a three-dimensional geometric model to be analyzed. Input means for inputting data relating to the model, shape model creating means for creating the model, area setting means for designating an area for generating a hexahedral mesh, and hexahedral mesh generating means for generating a hexahedral mesh A tetrahedral mesh generating means for retrieving a hexahedral mesh adjacent to the tetrahedral region and arranging the tetrahedral mesh on the surface of the hexahedral mesh; and a tetrahedral mesh for generating a tetrahedral mesh in a region in contact with the tetrahedral mesh An analysis mesh generation apparatus including a mesh generation unit is disclosed. According to this configuration, the input means enables input of a shape model in an interactive format. Thereafter, the three-dimensional geometric model is automatically generated and the hexahedral mesh is automatically generated by the shape model generating means, the area setting means, and the hexahedral mesh generating means. Further, the hexahedral mesh adjacent to the tetrahedral mesh generation area is searched by the tetrahedral mesh generation means, and the tetrahedral mesh is automatically generated on the surface thereof, and thereafter the tetrahedral mesh is automatically generated. . The hexahedral mesh having no free sides and the tetrahedral mesh can be connected by the quadrangular pyramid mesh generation means, and the stability in analysis is improved. Further, the analysis processing using the finite element method can be automated.

[0010]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an analysis mesh generation apparatus according to the present invention. The analysis mesh generation apparatus according to the present invention is mainly configured by the analysis processor 1 and includes a shape model input unit 11 and an automatic mesh generation unit 12. A model database 2 is connected to the analysis processor 1. The model database 2 includes a shape model data 21 for storing a shape model and a mesh model 22 for storing a mesh model.
To provide data to the analysis processor 1 and store the data. The shape model data 21 is connected to the shape model input unit 11, and the mesh model 22 is connected to the automatic mesh generation unit 12. The shape input / display device 3 is connected to the shape model input unit 11. A keyboard 4 and a mouse 5 for inputting a shape model are connected to the shape input / display device 3. A CRT as a display is installed on the front of the shape input / display device body. The above shape model input unit 11
Then, processing is performed while interactively creating a shape model to be analyzed, setting a hexahedral mesh region, setting the number of mesh divisions, setting a standard mesh size, and the like. In addition, the automatic mesh generation unit 12 automatically and continuously executes processes such as hexahedral mesh generation, tetrahedral mesh generation for hexahedron / 4-tetrahedral mesh joining, and tetrahedral mesh generation. Hereinafter, these operations will be described.

FIG. 2 is a flowchart showing a mesh generation process by the analysis processor 1. First, the operator operates the keyboard 4 and the mouse 5 attached to the shape input / display device 3 to input a shape model to be analyzed (step S201), and creates a shape model (step S20).
2). Then, an area for generating a hexahedral mesh is designated,
The number of divisions of the hexahedral mesh generation area and the standard mesh dimension value are set (steps S203, S204, S20).
5). The processing of steps S203 to S205 described above is processing executed by the shape model input unit 11. here,
The designation of the hexahedral mesh area is performed in consideration of the following points. That is, the hexahedral mesh is generally used when regularity is required for the node coordinate values when evaluating the analysis result. Further, in an analysis including a contact problem, there is a case where a hexahedral mesh is arranged at the contact portion to improve the convergence of the analysis.
However, since it is difficult to automatically divide the entire complex shape model with a hexahedral mesh, such a portion is left as a region for generating a tetrahedral mesh highly adaptable to a complex shape model, and a hexahedral mesh is left. It is not a mesh area.

The following processing is executed by the automatic mesh generation unit 12. The first is hexahedral mesh generation. (Step S206). The partial area for generating the hexahedral mesh is one of a plurality of partial areas constituting the shape model, and has a hexahedral shape having six quadrilateral faces with boundaries. However, since the quadrilateral surface of the boundary may be a curved surface, 6
The partial area for generating the face mesh is not necessarily a rectangular parallelepiped. In the partial area where the quadrilateral surface of the boundary is a curved surface, an internal grid is generated using the mapping method. In this mapping method, a partial area for generating a hexahedral mesh is regarded as a rectangular parallelepiped, and meshes are generated on the surface and inside of the rectangular parallelepiped based on information such as the number of mesh divisions input by a user, and then the original is formed using a shape function. This is a method of mapping a mesh onto a shape, and is generally used in generating a hexahedral mesh. When there are a plurality of hexahedral mesh regions, a hexahedral mesh generation process is performed on all of them.

When the generation of the hexahedral mesh is completed, the remaining area is divided into meshes by the tetrahedron. However, if the tetrahedral mesh is directly pasted on the hexahedral mesh as described above, mesh mismatch occurs. . That is, since the hexahedral mesh and the tetrahedral mesh have different surface shapes (one is a quadrangle and the other is a triangle), the consistency of nodes and elements is maintained, and there is little problem in analysis. It is desirable to connect by a method. In order to satisfy this problem, in the present invention, a quadrangular pyramid mesh is sandwiched only between the hexahedral mesh region and the tetrahedral mesh region (step S207), and the joining of the two types of meshes is realized while maintaining the consistency of the nodes. ing. By making this quadrangular pyramid mesh the same topological structure as the hexahedral mesh (generated by degenerating one surface of the hexahedral mesh into one point), even when an analysis program that does not support the quadrangular pyramid mesh is used. Analysis becomes possible. The degeneracy described here is a process in which the identification numbers of the nodes belonging to one surface of the hexahedron are all set to the same value, and apparently a quadrangular pyramid-shaped mesh is formed. In generating this tetragonal pyramid mesh, first, a hexahedral mesh region having a joining surface is searched, that is, a hexahedral mesh region adjacent to the tetrahedral mesh region is searched, and a tetrahedral mesh having the joining surface portion as a bottom surface is searched. Generate The coordinate values of the vertices facing the bottom surface of the quadrangular pyramid mesh are determined based on geometric information such as the node coordinate values of the hexahedral mesh and the standard mesh dimension values.

When the generation of the quadrangular pyramid mesh for the necessary portion is completed, a tetrahedral mesh is generated. (Step S
208). As a method for generating a tetrahedral mesh, there are four methods.
An advancing front method or the like is used in which a triangular mesh at the boundary surface excluding the junction with the hexahedral mesh in the hexahedral mesh area is generated, and a tetrahedral mesh is sequentially generated while generating nodes toward the inside of the area. At this time, the mesh size follows the standard mesh size (average size of the generated mesh) set in the shape model input unit. Also, at the junction with the hexahedral mesh area,
Since a quadrangular pyramid mesh is arranged in advance and all the boundaries are triangular, a triangular mesh is not generated in this portion.

Note that, in terms of graphic processing, when a hexahedron and a tetrahedron are joined, in addition to a quadrangular pyramid or a triangular prism,
Any one of the square faces of the three-dimensional face having both the square face and the solid face is joined to the hexahedron, and any one of the three-
Two types of mesh can be joined by joining to a face body. However, such a method requires a great deal of time for automatic processing because the amount of calculation is large. On the other hand, according to the above-described embodiment, as an integrated process of automatically generating a mesh in which a hexahedral mesh and a tetrahedral mesh are mixed, a hexahedral mesh as an intermediate product is always generated after the hexahedral mesh is generated. Since the mesh is regularly arranged on the surface of the hexahedral mesh, the amount of calculation can be reduced,
Automatic processing becomes easy.

The features of the present invention among the above-described processes will be described in more detail. FIG.
FIG. 6 is a diagram illustrating a quadrangular pyramid-shaped mesh generated by degenerating a face mesh. The structure of the data representation 301 on the computer and the data representation 302 of the quadrangular pyramid mesh when handling the hexahedral mesh are common to the hexahedral mesh and the quadrangular pyramid mesh, so that each of the shape meshes has 8 columns (column “column”). 1 "to" 8 "). In the case of the quadrangular pyramid mesh, the node identification number is set to column “1”,
Duplication in “2”, “3”, and “4” (columns “1” to
The node identification number “1” is duplicated at four nodes for “4”. As described above, although it is apparently a tetragonal pyramid mesh, the structure is the same as that of the hexahedral mesh by using a mesh having the same phase as the hexahedral mesh (both are composed of 8 columns). By means of 4
Analytical calculation of the pyramid mesh can be performed. That is,
Generally, the element types that the finite element analysis program can handle are:
Although a hexahedral mesh and a tetrahedral mesh can be processed as a hexahedral mesh while using a tetragonal pyramid mesh, a conventional finite element analysis program can be used without any change.

FIG. 4 shows the node identification numbers and data representations of the mesh when there is also a node at the center of the side of the mesh. The node identification numbers "9" to "20" of the data representation 401 representing the hexahedron are shown. Corresponds to a node at the center of the side of the mesh (this is called a quadratic element). The data representation 402 representing the quadrangular pyramid mesh generated by degenerating this is
The column configuration is the same, and the identification numbers of the nodes that have been reduced to one point are all expressions reduced to “1”. As described above, in the quadrilateral pyramid mesh generation processing, when the hexahedral mesh to which the hexahedron mesh is connected is the type shown in FIG. In the case of a quadratic element type hexahedral mesh as shown in FIG. 4, a quadratic pyramid mesh of a quadratic element type is generated for connection.

FIG. 5 shows an example of a shape model to be subjected to finite element analysis. A process for generating a mesh model in which a hexahedral mesh and a tetrahedral mesh are mixed using this shape model will be described. Portions 501 and 502 shown by hatching in FIG. 5 are regions where a hexahedral mesh is generated. These areas are defined by intentionally dividing the model to be analyzed. In this example, the area where the upper and lower structures contact each other is considered to be an important area for analysis.
Place a face mesh region. The remaining white portions 503 and 504 are regions for generating a tetrahedral mesh. In addition, since the area for generating the hexahedral mesh is meshed by the mapping method, the area itself is also a hexahedron,
The shape of the region for generating the tetrahedral mesh is arbitrary. This is related to the good regularity of the hexahedral mesh and the high applicability to the complex shape of the tetrahedral mesh. By taking advantage of each mesh, it is possible to improve the efficiency of mesh generation. Making it possible.

FIG. 6 shows the hexahedral mesh area 50 of FIG.
The number of mesh divisions is set for each side of 1, 502, and a hexahedral mesh is generated by using a mapping method. The number of mesh divisions is set by interactively instructing a ridge line in the vertical, horizontal, and height directions of the hexahedral mesh generation area in the shape model input unit 11 and inputting an integer value representing the number of divisions into the ridge line. In this example, the region 501 in FIG.
Is represented by a mesh of (length, width, height) = (3, 3, 5), and a region 502 in FIG. 5 is represented by a mesh of (3, 3, 3). In this example, the intervals between the nodes of the mesh are uniform in each region. However, if the mesh division ratio is input as the mesh division information in addition to the number of mesh divisions, the mesh can be locally concentrated. Since the algorithm of the mapping method itself is known, the description is omitted here. Hatched portions 601, 6 in FIG.
02 is a hexahedral mesh adjacent to the tetrahedral mesh region in the hexahedral mesh generated as described above. The hexahedral meshes 601 and 602 can be easily extracted by searching for a shared plane between the regions based on the boundary expression structure of each region of the shape model (such as the identification number of a surface group constituting the region).

FIG. 7 is an explanatory diagram showing a method of determining the coordinates of the vertices (nodes facing the bottom surface) of the quadrangular pyramid mesh. In FIG. 7, reference numerals N1 to N8 are nodes of the hexahedral mesh, reference numeral Np is the center of gravity of the surface <N1, N2, N3, N4>, and reference numeral Nq is the center of gravity of the surface <N5, N6, N7, N8>. It is. Further, the coordinate value of the center of gravity point Np is represented by (Xp, Yp,
Zp), and the coordinate value of the center of gravity point Nq is (Xq, Yq, Zq). Further, the distance between the nodes N1 and N2 is D1 and the node N2
D2 is the distance between N3 and N3, and D is the distance between nodes N3 and N4.
3. The distance between nodes N4 to N1 is D4, the average of D1 and D3 is Dd, the average of D2 and D4 is Dw, and the center of gravity Np and N
The distance of q is Dh. Here, Dd, Dw, and Dh are:
This roughly corresponds to the width, depth and height of the hexahedral mesh. When the standard mesh size is MS, the height Ht of the quadrangular pyramid mesh is expressed by the following equation based on the MS and the above defined values.

Ht = min (Dd / 2, Dw / 2, Dh /
2, MS / 5) Here, min is a function that returns the minimum value of the argument. Further, the vertex coordinate values (Xc, Yc, Zc) of the quadrangular pyramid mesh
Is determined by the following equation.

Xc = Xp + (Xp−Xq) / Dh × Ht Yc = Yp + (Yp−Yq) / Dh × Ht Zc = Zp + (Zp−Zq) / Dh × Ht The above equation is the center of gravity of the surface of the hexahedral mesh. This means that a vector in the vertex direction of the tetrahedral mesh is obtained from the points Np and Nq, and the height of the tetrahedral mesh is determined based on the dimensions of the hexahedral mesh. A quadrangular pyramid mesh is generated from the vertices obtained by the above equation and the nodes (N1, N2, N3, N4) of the corresponding hexahedral mesh. Note that this example is an example of a primary element, but in the case of a secondary element, N1 is used without considering intermediate nodes.
It is obtained in the same manner as in the case of the primary element using the coordinate values of eight nodes from N to N8.

FIG. 8 is a diagram showing a state after generating the quadrangular pyramid meshes 801 and 802 in all necessary portions on the hexahedral mesh of FIG. A quadrangular pyramid mesh is not generated in a portion not adjacent to the tetrahedral mesh region. As shown in the tetrahedral mesh vertex coordinate determination method (FIG. 7),
The dimensions of the tetrahedral mesh are dependent on the dimensions of the hexahedral mesh, and the vertices of the tetrahedral mesh are determined from the eight vertices that make up the hexahedral mesh, so each vertex is not uniform.

FIG. 9 is a diagram showing a state in which a hexahedral mesh and a tetrahedral mesh are connected using a tetragonal pyramid mesh. In FIG. 9, the quadrangular pyramid mesh is indicated by hatching. A hexahedral mesh 901 is bonded to the lower surface of the quadrangular pyramid mesh, and tetrahedral meshes 902 and 9 are attached to the remaining four surfaces, respectively.
03, 904 and 905 are combined. Here, for convenience, only four tetrahedral meshes at the joint are shown, but these are a part of the tetrahedral mesh located at the boundary between the hexahedral mesh region and the tetrahedral mesh region.
By connecting another tetrahedral mesh to the tetrahedral mesh, a mesh is generated in the entire region of the tetrahedral mesh generation target.

FIG. 10 shows a tetrahedral mesh 1 in the state of FIG.
It is a mesh model of a final form with respect to the model of FIG. 5 completed by adding 001 and 1002. In the case of tetrahedral automatic mesh generation for an arbitrary shape, the regularity of the mesh is inferior to that of a hexahedral mesh, but the applicability of automatic mesh generation is high. The algorithm for generating the tetrahedral mesh is known, and therefore detailed description is omitted. For example, a Delaunay method, an advancing front method, or the like can be used.

[0024]

As described above, according to the method for generating a mesh for analysis of the present invention, a quadrangular pyramid mesh in which one surface is a quadrilateral surface and the other four surfaces are a triangular surface is converted into a hexahedral mesh and a four-sided mesh.
Since the tetrahedral mesh was connected to the tetrahedral mesh, the tetragonal surface of the tetrahedral mesh was connected to the tetragonal surface of the hexahedral mesh, and the triangular surface of the tetrahedral mesh was connected to the triangular surface of the tetrahedral mesh. It is possible to join two kinds of meshes without generating free sides while maintaining the consistency of the meshes.
Furthermore, by making the quadrangular pyramid mesh the same topological structure as the hexahedral mesh, analysis using an analysis program that does not support the quadrangular pyramid mesh becomes possible.

According to the method for generating a mesh for analysis of the present invention, a hexahedral mesh is first generated, and then a quadrangular pyramid mesh is arranged on the surface of the hexahedral mesh adjacent to the tetrahedral mesh. After arranging the tetrahedral mesh on the triangular surface of the quadrilateral pyramid mesh, the tetrahedral mesh is generated in the area where the tetrahedral mesh can be generated. Becomes possible. Further, since the hexahedral mesh and the tetrahedral mesh are joined without using the MPC, the amount of calculation can be reduced as compared with the case where the MPC is used, so that the processing time can be reduced.

Further, according to the analysis mesh generating apparatus of the present invention, an input means for inputting a shape model in an interactive format, a method for automatically creating a three-dimensional geometric shape model, and
Shape model creating means for generating a face mesh, area setting means, and hexahedral mesh generating means, tetrahedral mesh generating means for generating a tetrahedral mesh at a connecting portion between tetrahedral mesh and hexahedral mesh, and tetrahedral mesh Is provided with a tetrahedral mesh generating means that automatically generates a hexahedral mesh having no free side and a tetrahedral mesh, thereby improving analysis stability. Further, the analysis processing using the finite element method can be automated. Further, since the hexahedral mesh and the tetrahedral mesh are joined without using the MPC, the amount of calculation can be reduced as compared with the case where the MPC is used.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an analysis mesh generation device according to the present invention.

FIG. 2 is a flowchart illustrating a mesh generation process.

FIG. 3 shows a hexahedral mesh and its degenerated 4
FIG. 4 is a diagram showing a data representation of a pyramid mesh.

FIG. 4 is a diagram showing a data representation of a hexahedral mesh having a node also at the center of a side of the mesh and a quadrangular pyramid mesh generated by degenerating the mesh.

FIG. 5 is a shape diagram showing an example of a shape model to be subjected to finite element analysis.

6 is an explanatory diagram in which a mesh division number is set for each side of the mesh region in FIG. 5 and a hexahedral mesh is generated using a mapping method.

FIG. 7 is an explanatory diagram illustrating a method of determining coordinates of vertices of a quadrangular pyramid mesh.

FIG. 8 is a diagram showing a state after generating a quadrangular pyramid mesh for all necessary portions on a hexahedral mesh.

FIG. 9 is a diagram showing a state in which a hexahedral mesh and a tetrahedral mesh are connected using a tetragonal pyramid mesh.

FIG. 10 is a mesh model of a final form completed by adding a tetrahedral mesh to the state of FIG. 8;

[Explanation of symbols]

Reference Signs List 1 analysis processor 2 model database 3 shape input / display device 11 shape model input unit 12 mesh automatic generation unit 21 shape model data 22 mesh model 501, 502 hexahedral mesh region 503, 504 tetrahedral mesh region 601, 602 tetrahedral mesh Hexahedral mesh adjacent to the area 901 Hexahedral mesh 902-905 Tetrahedral mesh

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naoto Saito 502, Kachimachi, Tsuchiura-shi, Ibaraki Pref.

Claims (6)

[Claims] 1. A surface having a surface formed by six square faces.
One surface is made into a quadrilateral surface at the connection between the tetrahedral mesh and the tetrahedral mesh whose surface is made up of four triangular surfaces, and the other four
A tetragonal pyramid mesh whose surface is a triangular surface is arranged, a tetragonal surface of the tetragonal pyramid mesh is connected to a tetragonal surface of the hexahedral mesh, and a triangular surface of the tetragonal pyramid mesh is connected to a triangle of the tetrahedral mesh. A method for generating an analysis mesh, characterized by connecting to a surface. 2. A surface having a surface formed by six square faces.
A method for generating an analysis mesh in which a region capable of generating a tetrahedral mesh and a region capable of generating a tetrahedral mesh whose surface is formed by four triangular faces are connected, wherein
After generating a hexahedral mesh in an area where a tetrahedral mesh can be generated, a tetragonal pyramid mesh in which one surface is a quadrangle and the other four surfaces are a triangle is arranged on the surface of the hexahedral mesh adjacent to the tetrahedral mesh And then 3
A method for generating a mesh for analysis, comprising: arranging a tetrahedral mesh on a rectangular surface, and then generating a tetrahedral mesh in an area where the tetrahedral mesh can be generated. 3. The tetragonal pyramid mesh is generated such that all the identification numbers of nodes belonging to one surface of a hexahedron have the same value and have the same topological structure as the hexahedron mesh. A method for generating an analysis mesh according to claim 2. 4. The quadrangular pyramid mesh includes the generated 6 pyramid mesh.
3. The analysis according to claim 2, wherein the positions of vertices shared by the four triangular faces are determined based on the dimensions of the face mesh, and are generated based on the vertices and the nodes of the corresponding hexahedral mesh. For generating meshes for 5. The method according to claim 1, wherein the position of the vertex is calculated based on coordinates of a center of gravity of a bottom surface and a top surface of the hexahedral mesh, a height of the hexahedral mesh, and a height of the quadrangular pyramid mesh. The method for generating an analysis mesh according to claim 4, characterized in that: 6. An analysis mesh generation device for generating mesh data for finite element analysis based on a model of a three-dimensional geometric shape to be analyzed, an input means for inputting data related to the model, Searching for a hexahedral mesh adjacent to the tetrahedral area, a shape model creating means for creating a hexahedral mesh, an area setting means for designating an area for creating a hexahedral mesh, a hexahedral mesh generating means for creating a hexahedral mesh, A mesh for analysis, comprising: a quadrangular pyramid mesh generating means for arranging a quadrangular pyramid mesh on the surface of the hexahedral mesh; and a tetrahedral mesh generating means for generating a tetrahedral mesh in an area in contact with the quadrangular pyramid mesh. Generator.