JP2006318275A - Apparatus and method for preparing numerical analysis mesh - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a numerical analysis mesh preparation apparatus capable of forming solid elements having nodes on optional inner points in a model. <P>SOLUTION: The numerical analysis mesh preparation apparatus for dividing a model having a three-dimensional shape into meshes by solid elements is provided with a function for preparing a partition surface including an optional inner point A1 on the model in the model, a function for dividing the partition surface into a plurality of shell elements so that the shell elements respectively have the optional inner point A1 on the partition surface as nodes and a function for dividing space in the model partitioned by the partition surface into meshes by solid elements on the basis of the shell elements within the partition surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a numerical analysis mesh creation apparatus and method for creating an analysis model used for numerical analysis by FEM or the like.

Conventionally, a method for generating a neutral plane model based on shape data representing a shape of an article having a thickness, the step of dividing at least a part of a surface defined by the shape data into a plurality of surface elements Setting a movement vector for moving each node toward the interior of the article for each node constituting the surface element, and moving each node based on the set movement vector; Determining a contact between each moved node and another surface element, fixing a node determined to be in contact, and modeling a neutral plane based on the fixed point. A method of generating a characteristic neutral plane model is known (see, for example, Patent Document 1).
JP 2002-207777 A

  By the way, existing software for creating meshes such as IDEAS can automatically divide a model with a closed three-dimensional space into solid mesh elements by simply giving the element size and the number of divisions as input parameters. It has. However, current existing software does not have a function that automatically meshes the mesh so that a solid element having a node at an arbitrary internal point in the model can be formed. Therefore, if you want to create a solid element that has a node at a desired internal point in the model for the convenience of analysis, change the input parameters such as the element size many times until such a solid element is obtained by chance. It is necessary to recut or change the obtained mesh model in a local range, which is inconvenient and problematic from the viewpoint of analysis accuracy.

  Therefore, an object of the present invention is to provide a numerical analysis mesh creation device capable of creating a solid element having nodes at arbitrary internal points in a model.

In order to solve the above-described problem, according to one aspect of the present invention, in a numerical analysis mesh creating apparatus for dividing a model having a three-dimensional shape into meshes by solid elements,
The ability to create a partition surface in the model that includes any interior point in the model;
A function of dividing the partition plane by a plurality of shell elements so that a shell element having a node at the arbitrary internal point in the partition plane is formed;
And a function of dividing a space in the model partitioned by the partition plane into meshes by solid elements with reference to the shell elements in the partition plane. The

  In this aspect, the inclination of the partition surface may be arbitrarily set by the user. In addition, each solid element created on both sides of the partition plane shares the node of the shell element in the partition plane and also shares an element plane according to the mesh pattern of the shell element in the partition plane. It may be.

According to another aspect of the present invention, in the numerical analysis mesh creating method for dividing a model having a three-dimensional shape into meshes by solid elements,
Creating a partition surface containing any internal points in the model;
Dividing the partition plane by shell elements such that a shell element having a node at the arbitrary interior point in the partition plane is formed;
Partitioning a space in the model partitioned by the partition plane with a solid element based on the shell element in the partition plane; and
And a step of deleting the shell element after dividing the mesh by the solid element. A method for creating a mesh for numerical analysis is provided.

  According to the present invention, it is possible to obtain a numerical analysis mesh creating apparatus capable of creating a solid element having a node at an arbitrary internal point in a model.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  The numerical analysis mesh creation device is a computer in which software for realizing the following functions (numerical analysis mesh creation method) is incorporated. This software may be developed as completely new software, but can be created without major modifications based on existing software (eg, PATRAN, IDEAS, Hyper-Mesh (both are registered trademarks), etc.) . The numerical analysis mesh creation apparatus has, for example, a mouse and a keyboard as a user interface, and is connected to a display for displaying a model or the like to be generated.

  FIG. 1 is a flowchart showing an overall outline of a numerical analysis mesh creation method according to the present invention.

  First, in step 100, an operation of providing input data to the numerical analysis mesh creation device is performed. As shown in FIG. 2, the input data includes 3D-CAD data of a three-dimensional object created by the 3D-CAD apparatus and node information for defining an anchor point A1 (and partition plane) described in detail below. .

  In this example, as shown in FIG. 2, when the information (0.0, 0.0, -2.8, ID5001) serving as the coordinates of the anchor point A1 and the ID (element ID number) is given as the node information. To do. The 3D-CAD data may include only data necessary for mesh division, such as lines, surfaces, and surfaces.

  Here, the anchor point A1 is a point that should exist as a node in the final analysis model, and is a point that is necessary for the convenience of analysis. For example, the anchor point A1 can be a center of gravity of a three-dimensional object to be analyzed or a point of interest of an analysis result (for example, a point in which stress is desired in the case of stress analysis). When the center of gravity of the three-dimensional object is used as the anchor point A1, an instruction to set the center of gravity as the anchor point A1 may be given as input data. In this case, the coordinates of the barycentric point are calculated based on the three-dimensional shape data that is input data inside the numerical analysis mesh creation device (that is, by software).

  In step 110, as shown in FIG. 3A, an anchor point A1 is created in the model of the three-dimensional object according to the coordinate information of the anchor point A1.

  In step 120, as shown in FIG. 3B, a plane including the anchor point A1 is created. In the example shown in FIG. 3B, this plane is created on a horizontal plane (xy plane), but the inclination of this plane can be arbitrarily set by the user. Alternatively, the inclination of the plane is determined by software calculation so that shell elements generated in the partition plane described later have as little negative effect as possible on the mesh quality of the final mesh data generated accordingly. May be. For example, the inclination of the plane may be determined so that the area of the three-dimensional object cut by the plane is minimized (that is, the area of the partition surface is minimized).

  In step 130, as shown in FIG. 3C, the surface of the three-dimensional object model is divided by the plane created in step 120, and the space in the three-dimensional object model is divided into two. Hereinafter, a plane that divides a space in a model of a three-dimensional object (in the drawing, highlighted by a shadow) is referred to as a “partition plane”. When the partition plane (see FIG. 3D) including the anchor point A1 is defined and set in the model of the three-dimensional object in this way, the process proceeds to the mesh creation phase after step 140.

  In step 140, as shown in FIG. 4A, the partition plane is mesh-divided by the shell element so that a node (node) of the shell mesh (shell element) is formed at the anchor point A1. In this example, since a tetra mesh (tetrahedral element) is created as a solid element, a triangular element is used as a shell element. If there is a specification for mesh size etc., follow it.

  The processing of this step 140, that is, it is possible to create a shell mesh by specifying an arbitrary point in the plane as a node (that is, specifying an anchor point) by existing software, This can be realized by using the shell mesh automatic creation function of the software. As shown in FIG. 4B as a contrast, when the shell mesh is automatically created on the partition surface without setting the anchor point A1, no node can be accidentally formed at the anchor point A1.

  In step 150, as shown in FIG. 5, each surface (surface) of the three-dimensional object is divided by shell elements. It should be noted that if there is a designation for the mesh size or the like, follow that. Thereby, two closed spaces (closed spaces surrounded by the shell elements) defined by the shell elements in the partition plane and the shell elements in each surface of the three-dimensional object can be formed across the partition plane.

  In step 160, the two closed spaces defined by the shell elements in the model are meshed with the solid elements based on the shell elements in the partition plane. That is, an internal mesh is generated in two closed spaces with reference to a shell element in the partition plane.

  Specifically, there is a closed space in the model above the partition plane (indicated by area A in the figure) and a closed space in the model below the partition plane (indicated by area B in the figure). , Each is automatically meshed according to an appropriate internal mesh generation algorithm. At this time, automatic mesh division of each space is executed by giving a constraint so that a solid element having an element surface corresponding to a shell element in the partition surface (a connection surface between elements and one surface of a tetrahedron) can be formed. . That is, the solid elements created on both sides of the partition plane share the shell element nodes (including the node of the anchor point A1) in the partition plane, and follow the mesh pattern of the shell elements in the partition plane. Each space is divided into meshes so as to share the element surfaces. It should be noted that the automatic mesh division with such constraints can be realized by existing solid mesh creation software (for example, a function “delaunay” in IDEAS). That is, in existing software, a surface element corresponding to a shell element is generated on each surface of a closed space, and then an internal mesh is sequentially generated based on the surface element. As above, the shell element in the partition plane may be used.

  As a result, solid elements generated separately from each other above and below the partition surface in the model are connected and integrated through the partition surface. In this way, a solid mesh model including a solid element having a node at the anchor point A1 is completed.

  In the subsequent step 170, the shell element generated in the above step 140 and step 150 finishes its role and is deleted. This is because, as can be seen from the above, the shell element is generated intermediately to generate a solid element (internal mesh) having a node at the anchor point A1.

  In step 180, when the input data has an ID designation, the designated ID is given to the node corresponding to the anchor point A1 instead of the ID automatically given at the time of mesh generation.

  In step 190, the completed mesh data is output (eg, a file is generated with the display). This mesh data is used for analysis as an analysis model. For example, the user can perform analysis by setting desired constraint conditions, load conditions, and the like using analysis software such as NASTRAN (registered trademark) using the mesh data. When the analysis is completed, the analysis result (for example, stress value) of the node (identifiable by ID) corresponding to the anchor point A1 can be verified.

  As described above, according to this embodiment, a partition plane including a desired point as the anchor point A1 is defined, and the partition plane is mesh-divided so that a shell element having a node at the anchor point A1 can be formed. By dividing the model of the three-dimensional object by the solid element using the element as a reference, mesh model data of the three-dimensional object including the solid element having a node at the anchor point A1 can be obtained.

  In addition, since the mesh creation method for numerical analysis according to this embodiment can be realized by using the basic part of the automatic mesh creation function of the existing software, the high quality of the automatic mesh creation function of the existing software is maintained. However, it is possible to meet the needs of the analyst who wants to create a node at any point as described above.

  In the above-described embodiment, all of the processing of steps 110 to 180 may be executed collectively by software. In this case, for example, when the user inputs input data (such as the coordinates of the anchor point) and operates the mesh creation button, the software is activated, and a mesh model including a solid element having the anchor point as a node is generated. Output as output data.

  However, a part or all of the processing in steps 110 to 180 may be sequentially executed by software through an interaction. In this case, the user can obtain a final mesh model while confirming the processing result of each step (for example, confirming the state of the shell element generated in step 140).

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the embodiment described above, there is one anchor point A1, but it is also possible to set two or more similar anchor points. In this case, if necessary, a partition surface that includes two or more anchor points in common may be defined, or a plurality of partition surfaces may be defined.

  In the above-described embodiment, the coordinates of the anchor point are given by specifying a point that can be calculated such as input or the center of gravity. It is also possible to input 3D-CAD data including the data of the point as input data.

It is a flowchart which shows the general outline | summary of the mesh creation method for numerical analysis by this invention. It is a figure which shows input data. It is a figure which shows the production | generation process of the anchor point A1 and a partition surface. FIG. 4A shows a state in which a shell element having a node at the anchor point A1 is formed by mesh division on the partition surface, and FIG. 4B shows a shell having a node at the anchor point A1 by mesh division on the partition surface. It is a figure which shows the state which cannot do an element in contrast. It is a figure which shows the state by which the partition surface and the surface were mesh-divided by the shell element.

Explanation of symbols

  A1 anchor point

Claims (5)

In the numerical mesh generator for numerical analysis that divides a model with a 3D shape into solid mesh elements,
The ability to create a partition surface in the model that includes any interior point in the model;
A function of dividing the partition plane by a plurality of shell elements so that a shell element having a node at the arbitrary internal point in the partition plane is formed;
A numerical analysis mesh creating apparatus, comprising: a function of dividing a space in a model partitioned by the partition plane by a solid element with reference to the shell element in the partition plane.   The mesh creation device for numerical analysis according to claim 1, wherein the inclination of the partition surface can be arbitrarily set by a user.   Each solid element created on both sides of the partition plane shares a node of the shell element in the partition plane and shares an element plane according to the mesh pattern of the shell element in the partition plane. The mesh creation apparatus for numerical analysis according to claim 1. In the mesh creation method for numerical analysis in which a model having a 3D shape is divided into meshes by solid elements
Creating a partition surface containing any internal points in the model;
Dividing the partition plane by shell elements such that a shell element having a node at the arbitrary interior point in the partition plane is formed;
Partitioning a space in the model partitioned by the partition plane with a solid element based on the shell element in the partition plane; and
And a step of deleting the shell element after the mesh is divided by the solid element.   A computer-readable program for causing a computer to function as the numerical analysis mesh creation device according to claim 1.

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