JPH10111957A - System and method for mesh generation and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily grasp a distribution of nodes at a stage wherein meshes are made small and large by setting a node roughness/closeness function showing the relation between the distance from a shape element selected out of a shape model for an object to be analyzed and the roughness and closeness of nodes, and finding and displaying a roughness distribution of nodes. SOLUTION: An analyzed object specifying part 11 of a process part 10 specifies a shape model for an object to be analyzed on the basis of data inputted through an input device 2 and a shape element selection part 12 selects an arbitrary shape element out of shape elements such as dots, lines, and planes constituting the shape model for the specified object to be analyzed. A roughness/closeness function setting part 13 sets a roughness/closeness function D(i) of nodes represented by the expression (where R is a specified ratio and (i) is a natural number) for the shape element (selected by the shape element selection part 12 to calculate a roughness/closeness distribution. A display part 14 finds a distribution of nodes of the shape model for the object to be analyzed on the basis of the set roughness/closeness function D(i) of the nodes and displays the distribution state on a display device 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mesh generation system for dividing an object to be analyzed into meshes in order to perform various analyzes of the object to be analyzed by using a finite element method, and a distribution of nodes in the mesh division. Regarding the designation method.

[0002]

[Prior Art] For various analyzes such as structural analysis and electromagnetic field analysis,
A finite element method for analyzing a shape model of an analysis target by dividing it into meshes is used.

[0003] In order to efficiently perform analysis by the finite element method, that is, to improve the analysis accuracy while suppressing the calculation cost, a region that is important in the analysis (for example, a portion where the stress changes rapidly, etc.). ) Mesh is small, and not important area (for example, a place where the stress change is gentle)
It is necessary to generate a mesh by accurately performing mesh coarsening such as enlarging the mesh. For this reason, conventionally, there has been used a mesh generation system that interactively performs mesh coarsening and automatically performs mesh division based on the roughening.

[0004] As this kind of mesh generation system,
The ones described in “Japanese Patent Application Laid-Open No. 7-129634” and those described in “Symposium on 3D Automatic Element Division by Fuzzy Knowledge Processing, Numerical Analysis in Structural Engineering, Volume 13, July 1989”, etc. Proposed.

In the former, the user inputs the distance from a certain shape element of the object to be analyzed and the distribution density of nodes,
A coarse / dense distribution of nodes for mesh generation is set in the shape element, nodes are generated based on the distribution, and a mesh is generated on the analysis object. In addition, when a plurality of shape elements of the analysis object have a coarse-density distribution of nodes set, for a portion where the coarse-density distribution overlaps, it is automatically determined which coarse-density distribution is to be adopted. It determines, and generates a node for the portion based on the determined density distribution to generate a mesh.

[0006] In the latter, a plurality of node patterns prepared for each shape element of an object to be analyzed are associated with a membership function used in fuzzy logic. Then, for the object to be analyzed, for a portion where a plurality of node patterns overlap, which node pattern is to be adopted is determined based on the membership function of each of these node patterns, and then, for the portion, the determined node pattern is determined. And generate a mesh based on.

[0007]

By the way, "Japanese Patent Laid-Open No.
In the mesh generation system described in "-129634", a graph representing the relationship between the distance from the shape element of the object to be analyzed and the distribution density of the nodes is displayed on the screen, so that the mesh is coarsely and densely arranged. I have. In the mesh generation system described in "3D automatic element division by fuzzy knowledge processing method, Symposium on Numerical Analysis in Structural Engineering, Vol. 13, July 1989", the nodes set to the shape elements of the analysis target are used. By displaying a graph representing the membership function of the pattern on the screen, the mesh density is interactively adjusted.

Therefore, in the above-described conventional mesh generation system, the user has to look at these graphs and imagine how the nodes are distributed on the object to be analyzed. For this reason, there is a problem that it is difficult to grasp what distribution of the nodes is generated in the step of coarsening and densifying the mesh.

The present invention has been made based on the above circumstances, and an object of the present invention is to explain how nodes for generating a mesh are distributed in a shape model of an object to be analyzed at a stage of mesh densification. Mesh generation system, mesh generation method,
And a recording medium.

[0010]

In order to solve the above problems, a mesh generation system according to the present invention generates a plurality of nodes in a shape model of an object to be analyzed, and generates the shape model based on the plurality of nodes. Is a mesh generation system that stores a shape model of an analysis target, and an arbitrary shape element from a plurality of shape elements constituting a shape model of the analysis target stored in the storage device. Selecting means for selecting, setting means for setting a node coarse density function representing a relationship between a distance from the shape element selected by the selecting means and coarse density of the node, and a node coarse density function set by the setting means Calculating means for obtaining a coarse density distribution of the nodes in the shape model of the object to be analyzed, and a shape model of the object to be analyzed showing the state of the coarse density distribution of the nodes calculated by the calculating means. Display means for displaying, characterized in that it includes a graphical user interface means for accepting the setting of the node density of function of the selection and the setting means in the form element in the selecting means.

Here, the calculating means obtains a coarse density of a node at a position of each of a plurality of representative points set in the shape model of the object to be analyzed in accordance with the nodal coarse density function set by the setting means. Wherein the display means ranks the shape model of the analysis target into a plurality of regions based on the coarse densities of the nodes at the positions of the plurality of representative points obtained by the calculation means, It is preferable to display a shape model of the object to be analyzed in which a coarse density distribution state of the node is shown.

A mesh generation method according to the present invention uses a computer system having at least a storage device storing a shape model of an object to be analyzed, a central processing unit, an input device, and a display device. A mesh generation method for generating a plurality of nodes in a shape model and dividing the shape model into meshes based on the plurality of nodes, wherein an analysis stored in the storage device is performed according to a command input to the input device. A selection step of selecting an arbitrary shape element from a plurality of shape elements constituting the shape model of the target object, and a distance and a node from the shape element selected in the selection step based on the data input to the input device. A setting step of setting a node coarse density function representing a relationship with the coarse density, and a node in the shape model of the object to be analyzed according to the node coarse density function set in the setting step A calculating step of obtaining a coarse density distribution, and a display step of displaying, on the display device, a shape model of the analysis object in which the coarse density distribution state of the node calculated in the calculating step is shown. Features.

According to the recording medium of the present invention, a plurality of nodes are generated in a shape model of an object to be analyzed by a computer system including a storage device, a central processing unit, an input device, and a display device. A recording medium in which a program for mesh-dividing the shape model based on the nodes is recorded, and according to a command input to the input device, a plurality of shapes forming a shape model of an analysis target stored in the storage device are stored. A selection procedure of selecting an arbitrary shape element from the shape element by the central processing unit, and, based on data input to the input device, a relationship between the distance from the selected shape element and a coarse density of a node. A setting procedure of setting the node coarse density function to be represented by the central processing unit; and setting the coarse density distribution of the nodes in the shape model of the object to be analyzed in accordance with the set node coarse density function. A calculation procedure obtained by a processing device, and a display procedure of displaying on the display device a shape model of the analysis object in which the calculated coarse density distribution state of the node is indicated are recorded. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of a mesh generation system according to an embodiment of the present invention.

The mesh generation system 1 according to the present embodiment
As shown in FIG. 1, it is configured to include an input device 2, a processing device 3, and a display device 4. Note that the mesh generation system 1 of the present embodiment can be realized by using a computer system such as a personal computer including at least a central processing unit, an input device, a storage device, and a display device.

The input device 2 specifies a shape of the object to be analyzed, selects a shape element of the object to be analyzed, or
This is a device for inputting information necessary for setting a coarse density function of a node. As the input device 2, for example, a keyboard, a mouse, or the like is used.

As the display device 4, for example, a CRT, an EL display, a liquid crystal display, or the like is used.

The processing device 3 comprises a processing unit 10 and a storage unit 20
And a user interface unit 30.

The processing section 10 includes an analysis object specifying section 11 and
It has a shape element selection unit 12, a coarse density function setting unit 13, a coarse density distribution calculation / display unit 14, and a mesh generation unit 15.

The analysis target specifying unit 11 specifies a shape model of the analysis target based on data input by the user via the input device 2.

The shape element selecting section 12 is provided by the user
Based on the data input via the input device 2, an arbitrary shape element can be selected from a plurality of shape elements such as points, lines, surfaces, and the like constituting the shape model of the analysis target specified by the analysis target specifying unit 11. Select

The coarse density function setting unit 13 sets a coarse density function of a node in the shape element selected by the shape element selection unit 12 based on data input by the user via the input device 2.

The coarse density distribution calculation / display unit 14 is configured to calculate the shape of the analysis object specified by the analysis object specifying unit 11 based on the coarse density function of at least one node set by the coarse density function setting unit 13. How the nodes are distributed in the model is determined, and the distribution state is displayed on the display device 4.

The mesh generation unit 15 determines an object to be analyzed based on the coarse density function of the nodes set by the coarse density function setting unit 13 and the coarse density distribution of the nodes obtained by the coarse density distribution calculation / display unit 14. Nodes are generated in the shape model of the analysis object specified in 11 to generate a mesh.

The storage unit 20 stores a shape model of the object to be analyzed,
It stores data, programs, and the like necessary for various processes in the processing unit 10, such as the selected shape element, the set coarse density function, and display data of the coarse density distribution. The storage unit 20 stores the RO
A storage device such as an M, a RAM, or a hard disk is used.

The user interface unit 30 is a graphical user interface that allows a user to work with the mesh generation system interactively. The user interface unit 30 displays predetermined information on the display device 4.
To be displayed. Then, based on the user's command sent via the input device 2, the analysis target specifying unit 11, the shape element selecting unit 12, the coarse density function setting unit 13, the coarse density distribution display unit 14, or the mesh generating unit 15 is started.

FIG. 2 shows an example of a screen displayed on the display device 4 by the user interface unit 30 in the process of setting the coarse density function of the nodes (mesh coarse / close). In the example shown in FIG. 2, the display screen includes a shape element type designation area 41.
A maximum density designation area 42, a ratio designation area 43, a drawing button 44, a registration button 45, a cancel button 46,
It comprises a display area 47 in which the shape model of the analysis target specified by the analysis target specifying unit 11 is displayed, and an end button 48.

The shape element type designation area 41 is an area for designating the type of the shape element that the user is going to select.

The maximum density designation area 42 is an area for designating the maximum value of the coarse density function of the node set in the designated shape element.

The ratio designation area 43 is an area for designating a ratio value when the coarse density function of the node is defined by a geometric progression.

The registration button 45 is a button for setting a node coarse density function. The cancel button 46 is a button for canceling the set node coarse density function.

The drawing button 44 is a button for displaying the coarse density distribution of the nodes in the shape model of the analysis object displayed in the display area 47.

The end button 48 is a button for ending the process of designating the nodal coarse density distribution in the shape model of the object to be analyzed, that is, the process of coarsely meshing the meshes.

The contents displayed on the screen (designation of the type of shape element, designation of various buttons, etc.) can be specified by using the pointing device such as a mouse as the input device 2 and clicking the corresponding portion. It is preferred to do so.

The screen displayed on the display device 4 by the user interface unit 30 is, for example, an X window system (trademark: Massachusetts Institute of Technology)
And OSF / Motif (trademark: Open Software Foudatio
n companies).

Next, the operation of the mesh generation system 1 of this embodiment will be described.

First, an outline of the operation will be described with reference to FIG.

FIG. 3 is a flowchart for explaining the outline of the operation of the present embodiment. This flow is performed by, for example, a computer system such as a personal computer executing a predetermined program recorded on a recording medium such as a hard disk or a CD-ROM.

First, a process of specifying the shape of the object to be analyzed is performed (step 101). The analysis target specifying unit 11 specifies a shape model of the analysis target based on the data input to the input device 2. The input data may be shape data created by commercially available CAD software.

Next, with respect to the shape model of the object to be analyzed specified in step 101, a coarse density distribution of the nodes is obtained based on a coarse density function of the nodes set in at least one shape element, and the mesh density is set. Perform processing (step 1
02). The mesh roughing process will be described later.

Next, a mesh generation process is performed (step 103). The mesh generation unit 15 generates the nodes in the shape model of the analysis target based on the density function and the coarse density distribution information of the nodes obtained in step 102, and connects the nodes using the Delaunay method or the like, thereby forming a mesh. Generate

Next, the roughening of the mesh, which is the processing in step 102 of FIG. 3, will be described.

FIG. 4 is a flow chart for explaining the roughening of the mesh.

First, a shape element selection process is performed (step 201). In this process, the user selects a shape element type using the shape element type designation area 41 in FIG. 2 and then designates an arbitrary shape element of the analysis target using the display area 47 in FIG. Then, the shape element selection unit 12 is activated and executed. When the shape element specified by the user using the display area 47 matches the type of the shape element specified by the user using the shape element type specification area 41, the shape element selection unit 12 selects the shape element. select.
It is preferable that the shape element of the analysis target is specified by using a pointing device such as a mouse as the input device 2 and clicking the shape element of the analysis target displayed in the display area 47.

Next, a coarse density function of a node is set for the shape element selected in step 201 (step 202).
In this process, the user specifies the maximum value of the coarse density function of the node and the ratio value when the function is defined by a geometric progression using the maximum density specification area 42 and the ratio specification area 43 of FIG. Thereafter, by specifying the registration button 45 in FIG. 2, the coarse density function setting unit 13 is activated and executed.

The coarse density function setting section 13 firstly sets the maximum value and the ratio value of the coarse density function of the node specified by the user,
As shown in FIG. 5, when defined by a geometric progression, a coarse density function of the node is obtained such that the density decreases as the distance from the position of the shape element increases. For example, if the unit distance is U, the specified ratio is R, and the specified maximum density is M, the coarse density function whose shortest distance from the shape element is longer than U × (i−1) and equal to or smaller than U × i D (i) can be represented by the following equation. Where i is a natural number and D (0) =
M, R ≦ 1.

D (i) = R × D (i−1) (Equation 1) Next, the obtained coarse density function of the node is calculated as the shortest distance from the selected shape element, for example, if the selected shape element is a point. The shape element is set based on the shortest distance from the point or, if it is a line, the shortest distance from the line.

Although a function defined by a geometric progression as a coarse density function is used here, instead of the geometric progression,
An inverse function of the shortest distance from the designated shape element, or a coarse density function defined by a logarithmic function or the like may be used.

Next, the coarse density distribution calculation / display unit 14 is activated, and based on the coarse density function of the nodes for at least one shape element set in step 202, the coarse density distribution of the nodes of the object to be analyzed is obtained. Ask for. Then, in accordance with the user's instruction, the obtained coarse density distribution of the nodes is displayed on the shape model of the analysis object displayed in the display area 47 of FIG. 2 (step 203). Calculation and display processing of the coarse density distribution of the nodes will be described later.

Next, it is determined whether or not the setting processing of the coarse density function of the node has been completed (step 204). When the end button 48 in FIG. 2 is designated, it is determined that the process has been completed, and this flow is terminated. On the other hand, if the end button 48 has not been designated, a process of selecting a new shape element (step 201), a process of setting a coarse density function of nodes for the selected shape element (step 202),
And calculation of the coarse density distribution of nodes for the analysis object
The display process (step 203) is repeatedly performed.

Next, the rough density distribution calculation / display processing which is the processing in step 203 of FIG. 4 will be described.

FIG. 6 is a flowchart for explaining the coarse density distribution calculation / display processing.

The coarse density distribution calculation / display unit 14 first sets a plurality of coarse density representative points, which are points for displaying the coarse density distribution of the nodes in the shape of the analysis object specified in step 101 of FIG. (Step 301). This setting may be performed, for example, as shown in FIG. 7 so that the coarse density representative points are uniformly distributed in the shape model of the analysis object according to the number of meshes specified in advance by the user. Also, with reference to the coarse density function set in step 202 of FIG. 4, a large number of coarse density representative points are set in a high coarse density area, and a small number of coarse density representative points are set in a low coarse density area. You may make it set. Each of the plurality of coarse density representative points has an identification number.

Next, 1 is substituted for the variable i (step 3).
02). After that, the i-th coarse density representative point has the coarse density information of the node. The coarse density of the node at the coarse density representative point is obtained by substituting the shortest distance between the coarse density representative point and the shape element selected in step 201 of FIG. 4 into the coarse density function set for the shape element. be able to.
When a coarse density function is set for a plurality of shape elements, each of the shortest distances between the coarse density representative point and each of the shape elements is substituted into the corresponding coarse density function, so that a node at the coarse density representative point is obtained. Is determined for each of the plurality of coarse density functions. Then, the one having the largest value among the plurality of obtained node coarse densities is set as the coarse density of the node at the coarse density representative point.

Next, 1 is added to the variable i (step 30).
4) Then, it is determined whether or not the variable i exceeds the total number of coarse density representative points (step 305). If the variable i exceeds the total number of coarse density representative points, it means that all coarse density representative points have information on the coarse density of the nodes.
Shift to 06. On the other hand, if the variable i does not exceed the total number of coarse density representative points, the process returns to step 303.

In step 306, the drawing button 4 in FIG.
It is determined whether or not 4 is specified. If the drawing button is designated, the coarse density distribution of the nodes is displayed on the analysis object displayed in the display area of FIG. 2 (step 3).
07). As a display method, a method of connecting coarse density representative points having substantially the same node coarse density at a constant coarse density interval with a smooth line so as to display contour lines on a map, or a method of displaying the node coarseness of the coarse density representative point. A method of classifying the shape model of the analysis target into a plurality of regions in accordance with the value of the density and coloring each region with a color according to the rank is conceivable. However, the present invention is not limited to these, and any display may be used as long as it is possible to visually grasp what kind of coarse density distribution nodes are set in the shape model of the analysis object.

FIG. 8 shows an example in which the coarse density distribution of the nodes is displayed in different colors on the shape model of the object to be analyzed. In the example shown in FIG. 8, an arc portion is selected as a shape element, and a node coarse density function is set in the portion. Then, based on the nodal coarse densities of each of the plurality of coarse density representative points set in the shape model of the analysis target, the shape model of the analysis target is ranked into six regions, and from the higher node coarse density, Red,
The colors are orange, yellow, green, blue, and purple. In this example, the classification is made into six. However, the shape model of the analysis object is divided into more regions, and each region is colored according to the rank, so that a smooth color display is performed. You may make it.

According to the present embodiment, the coarse density distribution of the nodes for generating the mesh can be displayed on the shape model of the object to be analyzed at the stage of the mesh densification. With the nodal coarse density function, it is possible to visually grasp the distribution of the nodal points for generating a mesh in the shape model of the analysis object.

Thus, when the user differs from the intended coarse density distribution, the user can designate the cancel button in FIG. 2 to cancel the coarse density function of the node and reset the coarse density function of the node. As described above, by repeatedly setting the coarse density function of the node and visually grasping the coarse density distribution of the node based on the set coarse density function, the coarse density distribution of the node intended by the user is easily created. be able to.

In this embodiment, a plurality of coarse density representative points are set in the shape model of the object to be analyzed, and each coarse density representative point has information on the nodal coarse density at the point. Then, based on the node coarse density information of each coarse density representative point, the node coarse density distribution is displayed in the shape model of the analysis object. By doing so, for example, based on the node coarse density at each pixel position of a plurality of pixels constituting the shape model of the analysis target, the display processing can be performed at a higher speed than when displaying the node coarse density distribution. Can be.

In this embodiment, FIGS. 7 and 8 are described by taking as an example the case where the object to be analyzed has a two-dimensional shape. However, the present invention is naturally applicable even when the analysis target has a three-dimensional shape. In this case, the coarse density distribution in the three-dimensional space is calculated by setting a plurality of coarse density representative points on the surface or inside the analysis object. And
The node coarse density distribution of the object to be analyzed is displayed for a surface or a cross section specified by the user.

[0063]

As described above, according to the present invention,
At the stage of mesh densification, it is possible to visually grasp the distribution of nodes for generating a mesh in the analysis object.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a mesh generation system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a screen in a setting process of a node coarse density function (mesh coarse / density) displayed on a display device by a user interface unit of FIG. 1;

FIG. 3 is a flowchart for explaining an outline of the operation of the mesh generation system shown in FIG. 1;

FIG. 4 is a flowchart for explaining mesh roughening.

FIG. 5 is a diagram for explaining an example of a coarse density function.

FIG. 6 is a flowchart for explaining a coarse density distribution calculation / display process.

FIG. 7 is a diagram for describing coarse density representative points set in the shape of an analysis target object.

FIG. 8 is a diagram for explaining a display example of a coarse density distribution of an analysis object.

[Explanation of symbols]

 Reference Signs List 1 mesh generation system 2 input device 3 processing device 4 display device 10 processing unit 11 analysis target specifying unit 12 shape element selection unit 13 coarse density function setting unit 14 coarse density distribution calculation / display unit 15 mesh generation unit 20 storage unit 30 user Interface part 41 Shape element type designation area 42 Maximum density designation area 43 Ratio designation area 44 Draw button 45 Registration button 46 Cancel button 47 Display area 48 End button

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukio Hamaguchi 3-2-1, Sachimachi, Hitachi, Ibaraki Prefecture Inside Hitachi Engineering Co., Ltd. (72) Kazunori Tsukahara 3-2-2, Sachimachi, Hitachi, Ibaraki No. 1 Inside Hitachi Engineering Co., Ltd.

Claims (4)

[Claims] 1. A mesh generation system for generating a plurality of nodes in a shape model of an object to be analyzed and dividing the shape model into meshes based on the plurality of nodes, wherein the shape model of the object to be analyzed is stored. Storage means; selecting means for selecting an arbitrary shape element from a plurality of shape elements constituting the shape model of the analysis object stored in the storage device; distance from the shape element selected by the selection means; Setting means for setting a nodal coarse density function representing a relationship with the coarse density of, and calculating means for obtaining a coarse density distribution of the nodes in the shape model of the object to be analyzed according to the nodal coarse density function set by the setting means Display means for displaying a shape model of the analysis object in which the coarse density distribution state of the node calculated by the calculation means is indicated; selection of a shape element by the selection means and the setting means Mesh generation system characterized in that it comprises a graphical user interface means, the receiving setting of the node density of functions. 2. The method according to claim 1, wherein the calculating unit calculates a value of a node according to a node coarse density function set by the setting unit at each of a plurality of representative points set in the shape model of the object to be analyzed. Determining the coarse density, wherein the display means ranks the shape model of the analysis target into a plurality of regions based on the coarse densities of the nodes at the positions of the plurality of representative points obtained by the calculating means. The mesh generation system displays a shape model of the object to be analyzed in which the coarse distribution state of the nodes is displayed. 3. A computer system comprising at least a storage device storing at least a shape model of an object to be analyzed, a central processing unit, an input device, and a display device, wherein a plurality of nodes are added to the shape model of the object to be analyzed. And generating a mesh model of the shape model based on the plurality of nodes, according to a command input to the input device, the shape model of the analysis object stored in the storage device, A selection step of selecting an arbitrary shape element from a plurality of constituent shape elements to be configured; and, based on data input to the input device, a relationship between a distance from the shape element selected in the selection step and a coarse density of a node. A setting step of setting a nodal coarse density function to be represented, and a calculating step of obtaining a nodal coarse density distribution in the shape model of the object to be analyzed according to the nodal coarse density function set in the setting step. If, mesh generation method characterized by comprising: a display step of rough density distribution of nodes calculated by the calculating step the shape model of the analysis object shown, and displays on the display device. 4. A computer system comprising a storage device, a central processing unit, an input device, and a display device, wherein a plurality of nodes are generated in a shape model of an object to be analyzed.
A recording medium in which a program for mesh-dividing the shape model based on the plurality of nodes is recorded, wherein a shape model of an analysis target stored in the storage device is configured according to a command input to the input device. A selecting step of selecting an arbitrary shape element from the plurality of shape elements to be performed by the central processing unit, based on data input to the input device, a distance from the selected shape element, and a coarse density of a node. A setting procedure in which the central processing unit sets a nodal coarse density function representing the relationship of, and a central processing unit obtains a coarse density distribution of nodes in the shape model of the analysis object according to the set nodal coarse density function. A calculation procedure, and a display procedure of displaying, on the display device, a shape model of the analysis object in which the calculated coarse density distribution state of the node is indicated. Recording medium.