Device for generating finite element model

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a method for generating a mesh of a finite element model for the finite element method, and in particular, a finite element with less distortion in the shape model can be easily obtained without modifying the shape model or generating new auxiliary lines or auxiliary points. The present invention relates to a method of generating a mesh and controlling its coarseness and density, and a device to which this is applied.

【0002】

[Conventional technology]

Conventionally, in order to improve the efficiency of numerical simulation analysis of phenomena, the purpose is to generate a finite element mesh on the shape model to be analyzed by using the mapping method to further improve the calculation accuracy and efficiency. Development of 3D automatic element division system using shape recognition "Hiroaki Takahashi, Hiromi Shimizu et al. Proceedings of the Japan Society of Mechanical Engineers, Vol. 59, No. 560, p.279-285 1993-4, JP-A 1-311373 and JP-A 2- There is an automatic mesh generation method represented by the meshing method described in Japanese Patent Application Laid-Open No. 236677, which has been realized on the integrated mechanical CAE system HICAD / MESH.

【0003】

In addition, as a finite element mesh generation method using the mapping method, the calculation accuracy and calculation are performed by removing unnecessary meshes from the pattern of the mapping model prepared by the system and easily generating a mapping model adapted to the shape model. There is also a semi-automatic mesh generation method represented by the meshing method described in Japanese Patent Application Laid-Open No. 5-2627 for the purpose of increasing efficiency.

【0004】

[Problems to be Solved by the Invention]

In the conventional automatic mesh generation method technology, only the shape model to be analyzed and the finite element mesh generation model, which is the final result, are displayed on the screen, and the system user intervenes in the mesh generation process to provide progress information. I couldn't get it. In addition, even if the semi-automatic mesh generation method is used, there is a limit to the shape model pattern that can be applied.

【0005】

On the other hand, as the shape model becomes more complicated, there is a problem that a part of the mapping model overlaps in the process of mapping to the Cartesian coordinate space, and the mapping model cannot be generated, or even if a finite element can be generated, it is very distorted. In some cases, it contained elements.

【0006】

In the conventional system, when the mapping model cannot be generated, an error message is displayed on the screen and the process is interrupted. Therefore, the system user had to return to the initial state and empirically correct the error-causing part of the shape model. Also, if you want to correct an element that has been distorted as a result, you have to return to the initial state and change the shape model and the number of divisions. The above-mentioned method requires complicated, time-consuming and labor-intensive work as the model becomes complicated. On the other hand, the method of preparing a pattern of a mapping model and semi-automatically controlling the pattern in element units so as to match the shape model also has a limit in dealing with the complexity of the model.

【0007】

As a method to solve these problems and easily and surely generate a mesh, the problem that occurs during automatic processing in the mesh generation process is removed and the desired mesh is generated without changing the shape model by the system user. In order to make it possible, the introduction of an interactive user intervention method into the system has been an issue.

【0008】

An object of the present invention is the sophistication of an automatic finite element mesh model creation system for analysis, which aims to save labor in product design and support the strengthening of new product development capabilities, and is used for complicated shape model change work by returning to the initial state. We provide a finite element mesh generator that can easily generate a finite element mesh even with a complicated shape model without being shifted, and improve the calculation accuracy by controlling the shape and density of the generated finite element mesh. To do.

【0009】

[Means for solving problems]

The purpose of the above is to create a shape model to be analyzed, to input division information to generate a finite element mesh, and to assign the ridgeline of this shape model to one of the coordinate axes of the Cartesian coordinate system. A function to generate a recognition model in which the connection relationship between the shape model and the ridgeline is the same, a function to generate a mapping model in which an orthogonal grid is generated on the surface and inside of this recognition model, and a function to display this generated mapping model on the screen. The function, the function to specify the ridgeline of this mapping model, the function to change the number of divisions of the specified ridgeline based on the amount of change in the number of divisions input by the input device, and the grid points on the surface and inside of this mapping model. This is achieved by providing a function of mapping to the shape model and generating a finite element model. In particular, it is provided with a function of highlighting the error portion of the mapping model.

【0010】

With this configuration, a mapping model that recognizes the original shape generated in the middle of the mesh generation process is displayed on the screen, and the system user intervenes in the process to change the shape of the mapping model. It can assist automatic mesh generation, and can easily generate a finite element mesh even with a complicated shape model without being bothered by the complicated shape model change work of returning to the initial state, or the generated finite element. The shape and density of the mesh can be controlled.

【0011】

Hereinafter, in the present specification, a model means a set of numerical data expressing a shape, and a shape model means a model created by a system user and expressing an analysis target in a three-dimensional space. The recognition model means a model in which the ridgeline of the shape model is transformed so as to be parallel to any coordinate axis direction of the Cartesian coordinate system, and the connection relationship between the shape model and the ridgeline is equal. The mapping model means a model in which an orthogonal lattice is generated on the surface and inside of the recognition model, and the finite element model is a finite element that maps the lattice points on the surface and inside of the mapping model to the shape model. It means a model converted into a form that can be input to the analysis of the method. Further, the interference portion means a portion where a portion that does not intersect or overlap on the shape model intersects or overlaps on the mapping model.

【0012】

When the system user selects the change method from the menu, selects each line segment of the displayed mapping model with the mouse, and inputs the change amount from the keyboard, the shape of the mapping model on the screen is changed in response to the change. Let me redisplay. At the same time, the generated mesh on the expected shape model corresponding to the mapping model at that time is also provisionally displayed to clarify the effect of the change. In addition, when interference occurs on the mapping model and a mesh cannot be generated, the causative part is displayed separately by color, thickness, etc., and the system user is urged to change.

【0013】

In this way, in the finite element generation process, the system user can efficiently generate a finite element mesh without directly changing a complicated shape model, and control the mesh shape and density by simply making simple changes. Make it possible.

【0014】

[Example]

Examples of the present invention will be described below with reference to the drawings. A typical example of the present invention is a set of unit cubes for recognition consisting only of line segments parallel to orthogonal coordinate axes, which is generated in the process of dividing a 3D solid shape model into finite elements using a curvilinear coordinate transformation method. The coarseness and density of the finite element mesh is controlled by displaying the mapping model divided into the above on the screen and modifying / changing the mapping model by interactive operation. Examples 1 to 6 thereof are used. Will be described in.

【0015】

FIG. 1 is a system configuration diagram for realizing this embodiment. This system roughly includes an input / output device 101, an input / output data processing unit 102 connected to the input / output device 101, a shape model generation unit 103 connected to the input / output data processing unit 102, and a finite element mesh generation. It is composed of a unit 104, a database input / output processing unit 110 connected to the shape model generation unit 103 and the finite element mesh generation unit 104, and a database 111 connected to the database input / output processing unit 110.

【0016】

The input / output device 101 includes a CRT display 101a for displaying a shape model, a mapping model, etc., a keyboard 101b for a system user to create a model, input numerical values, and change a model. It is mainly composed of mouse 101c. The input / output data processing unit 102 to which the input / output device 101 is connected analyzes and processes the data input from the input device 101 by the system user.

【0017】

The shape model generation unit 103 generates a shape model input by the system user based on the data processed by the input / output data processing unit 102. The finite element mesh generation unit 104 generates a finite element mesh in the shape model. The database input / output processing unit 110 processes the data generated by each generation unit so that it can be stored in the database 111.

【0018】

After the input / output data processing unit 102 processes the shape model generation data input by the system user using the keyboard 101b or mouse 101c of the input / output device 101, and then the shape model generation unit 103 generates the shape model data. It is stored in the database 111 via the database input / output processing unit 110.

【0019】

The finite element mesh generation unit 104 that causes the shape model to generate a finite element mesh includes a division information input unit 105 that determines an element unit, and the shape model in which the ridgeline of the shape model is assigned in any coordinate axis direction of the orthogonal coordinate system. A recognition model generation unit 106 that generates a recognition model with the same connection relationship of ridge lines, a mapping model generation unit 107 that generates a mapping model in which orthogonal grids are generated on the surface and inside of the recognition model, and a generated mapping model on the screen. It is composed of a mapping model correction unit 108 for displaying on the map and changing it by interactive operation, and a mesh generation unit 109 for mapping the surface and internal lattice points of the modified mapping model to the shape model to generate a finite element model. Will be done.

【0020】

The data for division information input by the system user using the keyboard 101b or mouse 101c of the input / output device 101 is processed by the input / output data processing unit 102 and then stored in the database 111 via the database input / output processing unit 110. .. Further, the mapping model generated by the mapping model generation unit 107, which is the process of the finite element mesh generation unit 104, is displayed on the CRT display 101a by the mapping model correction unit 108 via the input / output data processing unit 102, and the displayed information is displayed. When the system user changes the data with the keyboard 101b or mouse 101c, the data is processed again by the mapping model correction unit 108 via the input / output data processing unit 102, and the resulting mapping model is displayed on the CRT display 101a. Redisplay. If there is no change from the system user, the mesh generation unit 109 generates a finite element mesh in the shape model based on the mapping model, and the mesh data is stored in the database 111 via the database input / output processing unit 110.

【0021】

The media for providing the software for realizing this system to system users can be DAT, magnetic tape, or floppy (registered trademark) disk.

【0022】

FIG. 2 is an overall flowchart of finite element mesh generation according to this embodiment, and FIGS. 3 to 6 show models generated in each process. The finite element generation method, which is the core of this embodiment, will be described while associating each with each other.

【0023】

(1) Set the shape model to be analyzed by the finite element method. (ST1, for example, as shown in Fig. 3). The setting is performed by the input / output device 101. The shape model is generated by the shape model generation unit 103.

【0024】

(2) After inputting the division information for generating the finite element mesh by the division information input unit 105 in the finite element mesh generation unit 104 (ST2), the shape model is composed of only line segments parallel to the orthogonal coordinate axes. Generates a model that is phase-equal to and geometrically closest to the original shape. Hereinafter, this model is referred to as a recognition model (ST3, recognized model generation unit 106. If Fig. 3 is a shape model, the recognition model is as shown in Fig. 4).

【0025】

(3) Based on the division information, the recognition model is fine-tuned so as to be composed of only line segments that are integral multiples of the unit element length, and then an orthogonal lattice is generated in the recognition model to generate a mapping model. (ST4, the mapping model generation unit 107. If Fig. 4 is the recognition model, the mapping model is as shown in Fig. 5). At this time, the mapping model is displayed on the screen (ST5) so that the mapping model can be changed by an interactive operation (ST6 to 7, the mapping model correction is performed by the mapping model correction unit 108).

【0026】

(4) A grid is generated inside the shape model from the correspondence between the grid of the boundary of the mapping model and the grid of the boundary of the shape model obtained in (3) above, and a finite element mesh model is generated (ST8, mesh generator). It is performed at 109. If Fig. 5 is a mapping model, the finite element mesh model is as shown in Fig. 6).

【0027】

The process of (2) and (3) above will be described in detail. FIG. 7 shows a detailed flowchart of the first half process up to the generation of the mapping model. In (2), the recognition model is generated by decomposing the shape model into units called "body". Therefore, the shape model to be analyzed is first decomposed into "body" (ST9). The "body" means a set of line segments that are connected in a shape model, and is a minimum partial shape composed of only loops that do not include other closed loops in its own closed loop. For example, in the case of the shape model as shown in FIG. 3, for example, it is decomposed into the hole shape and the protrusion shape shown in 8a to 8c of FIG. A recognition model is generated for each of these bodies (that is, all the bodies are mapped to the Cartesian coordinate space to generate a recognition model. ST10. If Fig. 3 is a shape model, it is as shown in Fig. 9). In (3), the mapping model can be roughly divided into two stages: a stage of generating each of the above-mentioned bodies and a stage of assembling the mapping model of each generated body. Therefore, the present embodiment is characterized in that it has a two-stage configuration in which the primary correction and the secondary correction can be performed so that the mapping model generated at each stage can be displayed on the screen and corrected / changed. Figure 7 above shows the flow until a mapping model for each body is generated.

【0028】

In the mapping model generation process, first, based on the division information, the constituent line segments of each body are fine-tuned so as to be an integral multiple of the unit element length, and then an orthogonal lattice is generated on the recognition model of all the bodies. A mapping model for each body is generated (Fig. 10 shows a series of examples using Fig. 3 as a shape model).

【0029】

However, when the recognition model of each body is finely adjusted to an integral multiple of the element unit length, a self-interference portion that does not hold as a shape may occur. Figures 11 and 12 are examples of loops that cause two-dimensional self-interference. Figure 11 The shape model on the left contains a very elongated portion (11a). If the above-mentioned fine adjustment is performed on the recognition model of the shape including the portion smaller than the unit element length, a portion (11b) with an interval of 0 occurs and a normal mapping model cannot be generated. Also, in the case of a concave shape model including a curve as shown in Fig. 12, when mapped to the Cartesian coordinate space, the part composed of 12a to 12c may pass through the line segment 12d as shown on the right side of Fig. 12, which is normal. Cannot generate a good mapping model.

【0030】

However, these interferences can be avoided by changing the mapping model. In the case of FIG. 11, by moving the line segment 11d that overlaps the line segment 11c in the direction of the arrow 11e, the portion corresponding to 11a can be constructed, and a mapping model can be generated. Similarly, in the case of FIG. 12, interference can be avoided by moving the line segment 12b penetrating the line segment 12d in the direction of the arrow 12e.

【0031】

Therefore, in order to change the primary mapping model, when generating a mapping model for each body, it is searched for self-interference in all the loops constituting each body, and even one loop is interfering. If is included (ST11), the target body is displayed on the screen in an interfering state (ST12). After the system user corrects / changes this mapping model to a normal shape by mouse operation or keyboard input, the process proceeds to the assembly process of the mapping model. In addition, after ST10, the division information is taken in, and after there is an unprocessed body, it becomes ST11.

【0032】

One method of determining self-interference is to search for areas where line segments and points that do not intersect or touch on the shape model intersect or touch as a result of generating a mapping model. There is a method to check if there is a point (13a or 13b) that passes twice when each loop is traced counterclockwise as shown in FIG.

【0033】

As a method of displaying the body to be modified, a method of displaying the mapping model orthogonal lattice state or displaying the interference portion by color is used in order to clearly indicate the mapping model change guideline to the system user. Regarding the orthogonal grid state, as shown in Fig. 14, even if only the grid points on each line segment are displayed (14a) or the grid itself is displayed (14b), the number of divisions (number of grids) of each line segment is a number. It may be displayed with (14c). In addition, the interference portion detected by the above search method or the like is displayed by changing the color or thickness of the corresponding line segment (for example, the line segment 11d in FIG. 11 above) or the loop. Clarify the parts to be corrected / changed (ST13 in Fig. 7 for color-coded display of interference parts).

【0034】

FIG. 15 shows a typical method of changing the displayed mapping model three-dimensionally. The system user selects an arbitrary point (15a2) closer to the desired change direction (arrow 15a1) from the midpoint of the line segment to be changed in the mapping model (a) displayed on the screen with the mouse, and changes the desired point from the keyboard. Enter the amount as an integer value. When this change amount is positive, the number of grids of the selected line segment increases, and when it is negative, it decreases. According to the operation of the system user, the map model shape on the screen is changed as shown in (b), and at the same time, the density of the finite element mesh generated on the shape model is changed by the changed amount (c). At this time, the position selected with the mouse may be changed by selecting a line segment (15a3) orthogonal to the desired change direction. Further, if the line segments are changed by the same amount in the same direction, it is possible to select a plurality of line segments as one change target.

【0035】

As one method of avoiding the interference shown in FIG. 12 above, the upper half of the line segment 12a may be selected with the mouse and a negative value may be input.

【0036】

By the way, care must be taken when correcting the penetration as shown in FIG. This is because a secondary penetration may occur by correcting the penetration of a certain part. An example is shown in FIG.

【0037】

It is assumed that the mapping model of the shape model shown in (a) of FIG. 16 is generated as shown in (c). The line segment 16A1 and the line segment 16A2 on the loop 16A are interfering with each other. To correct this, change the line segment 16A2 by one grid downward on the screen (d). On the other hand, at this time, if the grid generated in the loop 16B is as shown in (b), the line segment 16c1 connected to the line segment 16A2 lowered for the correction of the loop 16A is changed by the same amount. As a result, interference is newly generated in the line segments 16c1 and 16c2 as in (e), so it is necessary to perform the same interference avoidance operation as in loop 16A for loop 16B and correct it as in (f). In this way, to prevent omission of the search for secondary interference caused by a certain change, every time the system user changes the mapping model, the interference search of all loops in the body is performed and the correction is performed interactively. Is repeated (ST14 in Fig. 7).

【0038】

When self-interference is eliminated for all bodies and a normal mapping model can be generated, the process of assembling each generated mapping model proceeds (ST15 in Fig. 7).

【0039】

FIG. 17 shows a flowchart of assembling the mapping model. Assembly is performed based on the positional relationship of the connection surfaces of each body (ST16). Here, the connecting surface is a surface to which each body is connected before disassembly, and means a surface as shown in 5a of FIG. The outermost loop 5b in this plane is called an outer loop, and the inner loop is called a junction loop.

【0040】

Since each body is assembled three-dimensionally from the two-dimensional positional relationship of a plane, even if each body is a normal mapping model, self-interference or mutual interference between bodies may occur in the assembled model. Examples are shown in FIGS. 18 to 21.

【0041】

Figure 18 is an example of a three-dimensional penetration of a shape model consisting of two bodies, body 18a and body 18b. The mapping model of each body is generated normally, but when they are assembled, the height of the body 18b including the diagonal line (18b1 to 18b4) shown by the broken line is mapped larger than the height of the body 18a. As shown in (d) and (d), a penetration part (18c1) and a contact part (18d1) are generated. To avoid this interference, it is necessary to reduce the number of grids of line segments 18c2 to 18c5 and 18d2 to 18d5, or increase the number of grids of line segments 18c6 to 18c9 and 18d6 to 18d9.

【0042】

FIG. 19 shows an example of mutual interference between the bodies of holes in a shape model having holes having a complicated shape. The mapping model for each body and the positional relationship on the connecting surface are determined without any problem, but since the shapes of body 19a2 and body 19a3 are special, when the mapping model is assembled three-dimensionally as shown in (a). Mutual interference of holes occurs inside the body 19a1 and a normal overall mapping model cannot be generated.

【0043】

FIG. 20 shows an example of mutual interference between the bodies of the protrusions and the holes in the shape model (a) having the protrusions and the holes. A mapping model for each body is generated without problems, but if you try to determine the positions of bodies 20b1 and 20b2 first and finally body 20b3 when assembling the mapping model, each joint loop on the joint surface When trying to determine the position of, the body 20b3 and the joint loops (20b11, 20b21) of the body 20b1 and body 20b2 partially overlap the hole loop (20b31) as shown in (b), causing mutual interference. , Cannot generate a normal global mapping model. This is because the body 20a1 of the shape model is trapezoidal, so even though there is no mutual interference in the shape model, the body 20b3, which is a mapping model of the body 20a1, is generated based on the loop 20a12 instead of the loop 20a11. to cause.

【0044】

The interferences shown in FIGS. 19 and 20 above can be avoided by moving the body involved in the interference. For example, in the case of FIG. 19, the mapping model (b) without the interference part is moved by moving the body 19a2 in the direction of the arrow 19a4, and in the case of FIG. By doing so, the mapping model of (c) can be generated.

【0045】

FIG. 21 shows an example in which the outer loop of the connecting surface is small and the bodies of the holes interfere with each other when assembling the mapping model. In the shape model of (a), when the body of two trapezoidal holes (21a1 and 21a2) located without interference is generated based on the larger loops 21a11 and 21a21. Interference as shown in (b) occurs. In this case, since there are not enough grids to move the body of the hole on the connecting surface and avoid interference, the outer loop 21b1 is extended in the direction of arrow 21b2 and then as in FIG. Interference can be avoided by moving body 21a1 or 21a2 ((c)).

【0046】

The second mapping model is changed to avoid interference in the assembly stage as described above. When assembling the mapping model for each body, if even a part of the bodies interferes with each other, the entire mapping model is displayed on the screen in the interfering state (ST17 in FIG. 17). The system user corrects / changes this mapping model to a normal shape by operating the mouse or inputting the keyboard, and completes the generation of the mapping model without interference (ST18 to ST21 in FIG. 17). At this time, even in the second change, as in the case of the first change, each time the mapping model is modified or changed in one place, the entire interference part is displayed so that it can be identified (ST19), and the presence or absence of the interference part is present. The change operation shall proceed while confirming.

【0047】

In order to show the specific operation procedure, the shape model whose processing was interrupted because the mapping model could not be generated in FIGS. 22 to 26 and the mapping model by applying this system to the shape model were operated. An example in which mesh generation is possible is shown on the display. The shape model of (a) is an example in which a contradiction occurs when assembling the mapping model and a finite element cannot be generated.

【0048】

When trying to generate a finite element model for the shape model to be analyzed displayed on the CRT display 101a, the screen shown in (b) is displayed, and an error message such as 22b1 is displayed and the process is interrupted. Conventionally, in such a case, the system user had to return to (a) and modify the shape model itself.

【0049】

On the other hand, when this system is applied to the same shape model as (a) in FIG. 22 ((a) in FIG. 23), the error part (23b2) as shown in (b) in FIG. 23 on the CRT display 101a. ) Is highlighted and the mapping model and the mapping correction command menu (23b3) are displayed.

【0050】

Here, FIG. 24 shows an example of a map correction command menu list. In this display example, vertex movement, fill switching, division number display switching, mapping model display movement, shape recovery, shape recovery, division cancellation, and division continuation are listed.

【0051】

Next, the procedure for modifying the mapping model will be described with reference to FIG. The system user selects the required command from the command menu with the mouse 101c, then moves the icon 25a1 with the mouse 101c to the error line segment position on the mapping model displayed on the CRT display 101a, and the mouse 101c. By pressing the left button 101c1 of, the line segment to be changed and its change direction are instructed. Next, input the change amount from the keyboard 101b to change the mapping model.

【0052】

After repeating the change operation until a mapping model with no error is displayed as shown in (a) of FIG. 26, when the division continuation is instructed, the changed mapping model is displayed on the shape model of (a) of FIG. 23. A finite element mesh is generated based on the data, and a finite element model as shown in FIG. 26 (b) is displayed as a result on the CRT display 101a.

【0053】

FIG. 27 shows a method for determining mutual interference between bodies. In the grid coordinates generated in the mapping model (a) of each body, a numerical value representing the positional attribute of each grid as shown in (b) obtained from the positional relationship of each body in the shape model is set, and each body is set. The grid points on the boundary of the body must not overlap or touch. Search for the parts that overlap or touch on the grid on the surface or inside of the other body.

【0054】

The method of displaying the body to be modified is the same as that of the first mapping model change. As a typical change method, an example of line segment expansion / contraction and point movement based on the case of the first change will be described below.

【0055】

FIG. 28 is an example of avoiding interference by expanding and contracting the line segment length. In the mapping model of (a), interference occurs at the 28a1 part. In this case, interference can be avoided by selecting the line segment 28a2 indicated by the alternate long and short dash line and changing the number of positive quantity grids in the direction of arrow 28a3. At this time, if all the points on the change direction side from the midpoint of the line segment 28a2 are moved by the same amount, the mapping model as shown in (b) is regenerated.

【0056】

FIG. 29 is an example of avoiding interference by moving points. In the mapping model of (a), when line segment 29a2 is selected and changed in the direction of arrow 29a6 in the same way as above in order to avoid the interference occurring in the 29a1 part, the line segment 29a3 and the line segment 29a4 are quadratic. Interference will occur. In this case, even if the change operation is the same, only the grid points in the loop 29a5, which are directly related to the interference, are changed. As a result, the mapping model (b) in which only the necessary parts are changed is regenerated.

【0057】

The movement of each body is realized by selecting the change direction line segment of the body to be changed with the mouse and inputting the change amount from the keyboard. For example, as an operation example when the body 19a2 is moved in the direction of the arrow 19a4 in FIG. 19, the change amount is input by selecting the change desired direction side from the midpoint of the line segment 19a21.

【0058】

As a result of the movement correction operation as described above, the grid state can be changed even if there is no interference in the whole mapping model. As a result, the case where a distorted finite element mesh is generated as shown in the 30b1 part of FIG. 30 (b) is immediately detected, and the mapping model is changed from FIG. 30 (a) to FIG. 31 (a). By changing it, it becomes possible to adjust the mesh shape and control the density as shown in (b) of Fig. 31.

【0059】

At this time, in order to allow the system user to control the density to the satisfaction while comparing how the finite element mesh changes due to the change of the mapping model, the mapping model (as shown in FIGS. 32 and 33) 30a, 31a) and the finite element model (30b, 31b) are displayed on one screen at the same time. Further, when the mapping model 30a displayed on the screen in FIG. 32 is modified, the figure is promptly switched to the changed figure as shown in 31a of FIG. 33, and the corresponding finite element model 31b is displayed at the same time.

【0060】

All types of operations related to the above mapping model change may be selected in the menu format as shown in FIG. 24, or may be in the command input format. In either case, it is preferable to temporarily save the data before the change so that the recovery operation can be easily returned to the initial state or the state immediately before the change during the change operation. After completing these series of interactive operations, a lattice is generated inside the shape model to generate a final finite element mesh from the correspondence between the boundary lattice of the mapping model and the boundary lattice of the shape model generated as a result. (ST22 in Figure 17).

【0061】

[Effect of the invention]

According to the present invention, a mapping model generated in the process of automatically generating a finite element mesh by the mapping method is displayed on the screen of the three-dimensional shape model to be analyzed, and the system user interacts with the mapping model. Since it is possible to control the density of the finite element mesh by changing it by a specific operation, it is possible to efficiently generate a mesh for accurate analysis.

[Simple explanation of drawings]

[Figure 1]

It is a system block diagram for carrying out this invention.

[Figure 2]

It is an overall flowchart of the mesh generation method by this invention.

[Fig. 3]

It is explanatory drawing of the example of the 3D shape model to be analyzed.

[Fig. 4]

It is a recognition model diagram generated from the shape model of FIG.

[Fig. 5]

FIG. 4 is a mapping model diagram in which an orthogonal grid is generated.

[Fig. 6]

It is a finite element mesh model diagram generated based on the mapping model of FIG.

[Fig. 7]

It is a flowchart until the mapping model is generated for each body.

[Fig. 8]

It is explanatory drawing which shows the state which disassembled the shape model of FIG. 3 into a body.

[Fig. 9]

It is a recognition model diagram for each body generated from the shape model of FIG.

[Fig. 10]

FIG. 9 is a mapping model diagram for each body in which an orthogonal lattice is generated.

[Fig. 11]

It is explanatory drawing of the example of a loop in which self-interference occurs due to a narrow portion.

[Fig. 12]

It is explanatory drawing of the example of the loop in which self-interference occurs by penetration.

[Fig. 13]

It is explanatory drawing which shows the counterclockwise direction of a loop.

[Fig. 14]

It is explanatory drawing of the example of the division number display method of each line segment of a mapping model.

[Fig. 15]

It is explanatory drawing of the example of the basic change method of the displayed mapping model.

[Fig. 16]

It is explanatory drawing of the example of the secondary interference generated by correcting one interference.

[Fig. 17]

It is a flowchart of the mapping model assembly method generated for each body.

[Fig. 18]

It is explanatory drawing of the 3D self-interference example.

[Fig. 19]

It is explanatory drawing of the interference example of the body of a plurality of holes.

[Fig. 20]

It is explanatory drawing of the interference example of the body of a hole and a protrusion.

[Fig. 21]

It is explanatory drawing of the example when it is necessary to change the outer loop in order to avoid the interference between the body of a hole.

[Fig. 22]

It is explanatory drawing of the example which failed to generate a mapping model.

[Fig. 23]

It is explanatory drawing of the display state of an error mapping model.

[Fig. 24]

It is explanatory drawing of the example of a map model modification command menu list.

[Fig. 25]

It is explanatory drawing of the mapping model correction method.

[Fig. 26]

It is explanatory drawing of the finite element model generated based on the modified mapping model.

[Fig. 27]

It is explanatory drawing of the example which shows the position attribute of each grid point in a mapping model.

[Fig. 28]

It is explanatory drawing of the change method example by the line segment expansion and contraction of the whole mapping model.

[Fig. 29]

It is explanatory drawing of the change method example by point movement of the whole mapping model.

[Fig. 30]

It is explanatory drawing of the example that the generated mesh shape is distorted.

[Fig. 31]

It is explanatory drawing of the example which corrected the distortion of the generated mesh shape.

[Fig. 32]

Modify before mapping model and a finite element model of the Dell is an explanatory diagram of an example that is displayed on the same screen.

[Fig. 33]

It is explanatory drawing of the example which displayed the modified mapping model and the finite element model on the same screen.

[Explanation of symbols]

101 ... I / O device, 101a ... CRT display, 101b ... Keyboard, 101c ... Mouse, 102 ... I / O data processing unit, 103 ... Shape model generator, 104 ... Limited element mesh generator, 110 ... database input / output processing unit, 111 ... database.