JPH03223969A - Shell mode generating device - Google Patents

Abstract

PURPOSE:To eliminate the waste of time required for calculation due to the worng designation of dircetion of a mesh surface and to improve the analizing efficiency by using a solid model for generation of a shell model and keeping the surface direction of the solid mode also in the shell model. CONSTITUTION:A solid model function part 2 is provided together with a sold/ shell model conversion function part 3, a mesh generating function part 4, a solid model data part 5, a shell model data part 6, and a mesh data part 7. The the solid model data obtained by the 2 is partly converted into a shell model via the part 3. At the same time, the data on the surface direction of the converted shell model is succeeded as it is form the solid model data. Thus it is possible to evade such a defect where the surface direction is unfixed owing to the generating procedure. Then the direction of the shell surface is automatically decided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shell model generation device for FEM analysis, etc., and particularly to a shell model generation device that can improve the efficiency of analysis work when performing analysis using shell elements. It is something.

[Conventional technology]

For generating shell models for conventional FEM analysis.

There are two methods: One method is conventional CAE
This is a method of using the system, called the stacking method. As shown in Figure 11, this method first moves a point [see figure (a)], makes its locus a line [see figure (b)], and then rotates the line to make the locus a plane. [See figure (c)].

At this time, give the number of divisions of the mesh for FEM analysis and the direction of the surface of the analysis element created by the mesh.

The shell model (metshu model) is now being generated. In the case shown in Figure (C), the number of divisions is 4 degrees, and the arrow 111 in the figure is the direction of the surface.

Another method is a system having a shape modeler, which will be described in conjunction with FIG. (a) of the figure is a shell model generation flowchart, in which 112 is a mesh information % 115 is a mesh generation function, 115a is mesh data, and 116 is an analysis condition setting function.

In addition, the same figure (b) is an explanatory diagram of the analysis target, and 11 in the figure
7 is the cylindrical object to be analyzed %118 is the cylindrical body 11
7 indicates the inside, and 119 indicates the outside of the cylindrical body 117.

The same figure (c) is an explanatory diagram of the shape modeling function, the same figure (d)
is an explanatory diagram of the mesh generation function, (e) is a partially enlarged view of a shell element, and (f) is an explanatory diagram of mesh information.

When generating a shell model using this method, the figure to be analyzed [the shaded part in Figure (b)] is
As shown in FIG. 4(c), a surface model or wire frame model is constructed using the computer's shape modeling function. Based on this model data mesh information (number of divisions, surface direction), a shell model (mesh model) that is actually used for analysis is generated.

Cielmo del is generally expressed as a thin skin with zero thickness, so it does not have any information about the inside or outside (or front or back). That is, a shell model 12 having a shape as shown in FIG.
In the case of 0, since the thickness is O, the distinction between inner and outer cannot be determined from the shape.

However, when performing analysis using FEM shell elements, the direction of the shell surface affects the analysis results.

That is, when analyzing a part of the spherical tank 121 shown in FIG. 14 using shell elements, it is necessary to clearly distinguish between inside and outside. In this example, the normal vector direction 122 (
counterclockwise direction) is the outer side 123, and the opposite side is the inner side 124.
It is defined as Therefore, the internal pressure 12 applied to the spherical tank 121
5 (Tension force) is normal vector direction 122, spherical tank 1
The external pressure (compressive force) 126 applied to 21 is in the opposite direction to the normal vector direction 122.

Therefore, if this specification is incorrect, the direction of the load value set in the analysis conditions, that is, the + and - signs of the data will be reversed, and correct analysis results will not be given.

[Problem to be solved by the invention]

For the above reasons, when generating a shell model (mesh data) using the above two methods, it is essential for the analyst to orient the surfaces for each mesh when generating the shell model (mesh data). . Therefore, it takes a lot of time to create mesh data, and errors occur frequently when changing the mesh shape. Also, when a third party checks, the orientation of one surface is determined by the vertices and order of the mesh for each element, whether clockwise or counterclockwise, so each element definition is the same as the original data creator. This makes it inefficient and virtually impossible for large-scale problems.

The purpose of the present invention is to eliminate such drawbacks of the prior art,
To provide a shell model generation device for FEM analysis, etc., which has high efficiency in analysis work and allows the orientation of surfaces to be inherited by mesh data (18M shell elements) without being affected by the model generation procedure. It is in.

[Failure to solve the problem]

In order to achieve the above object, the present invention includes a solid model function section, a solid/shell model conversion function section, a mesh generation function section, a solid model data section, a shell model data section, and a mesh data section. Be prepared.

Then, the solid model data generated by the solid modeling function section is converted into a shell model at least in part by the solid/shell model conversion function section, and the planar direction data of the converted shell model is converted into a solid model. It is characterized by being configured to inherit model data as is.

[Effect]

A solid model has internal and external information, that is, information that it is filled with content. To use this information, first, the shape of the shell model is temporarily generated as a solid model, and the faces of the solid model are converted to the shell model.

The generation method is to generate a solid model so that its surfaces match those of the shell model, and to create a shell model by stripping only the surfaces that correspond to the shell model. At this time, the direction of the surface of the shell model inherits the direction of the surface of the solid model. By doing this, the direction of the shell surface is automatically determined without making the surface direction unstable due to the generation procedure as in the conventional case.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a shell model generation device for FEM analysis according to an embodiment.

In the figure, 1 is the dialog processing 1 diagram display processing section, 2 is the solid modeling function section, 3 is the solid/shell model conversion function section, 4 is the mesh generation function section, 5 is the solid model data section % 6 is the shell model data Section %7 is a mesh data section, 8 is a graphic display device, 9 is a menu that appears on the display screen of the graphic display device 8, 10 is a keyboard, and 11 is a mouse.

The analyst uses a keyboard 10 or (as well as) a mouse 11
, input commands and parameters by picking up or keying in the menu 9 on the graphic display device 8, and confirming the response on the graphic display device 8. and generate mesh data.

The internal configuration of the Buri processor in this case is as shown in the same figure. Solid modeling function section 2% Solid model shell model conversion function section 3, mesh generation function section 4% File section (solid model data section 5, shell model data section 6% mesh data section 7
etc.).

Next, specific operations will be explained. The analyst uses the keyboard 10 to key in a desired command, or uses the mouse 11 to pick up the menu 9 displayed on the graphic display device 8.

Dialogue Processing 1 The solid modeling function unit 2 is operated via the graphic display processing unit 1. Then, the figure to be analyzed is constructed as a solid model in the computer, solid data is generated, and the generated solid data is stored in the solid data section 5. Then, using the solid/shell model conversion function section 3, the solid data is converted into shell model data. This shell model data becomes input data for the mesh generation function section 4.

Generate mesh data actually required for FEM analysis.

FIG. 2 is a diagram showing a body plate 8 of a drum, which is an example of an object to be analyzed. Next, an example in which the shaded area 9 in the figure is analyzed using shell elements will be described.

First, using the solid modeling function section 2,
A cylinder 10 (filled with contents) having a diameter d shown in l is generated. At this time, the diameter d of the cylinder 10 is the curvature R (0/D) of the finally required shell model, as shown in FIG.
Generate to match. This solid model data is processed using the boundary representation method 13-reps (Boundary
representations).

In the solid model data of the cylinder 10 expressed in B-reps, the surface 13 expressed as a polyhedron has a fixed direction, as shown in FIG. 4(a). That is, the normal vector direction 14 represents the outside 15, and the opposite represents the inside 16, meaning that the contents are packed.

FIG. 4(b) is an enlarged view of a part of the surface. Then, in the local deformation operation of the solid modeling function section 2, the range of the surface 9 actually used for analysis is defined using the edge line division and surface division functions. This state is shown in FIG. 3(b), where 11 is the boundary line and 12 is the vertex.

Next, as shown in FIG. 5, the solid/shell model conversion function section 3 picks up and specifies vertices on the boundary line of the solid model surface to be converted into a shell model using the mouse. In other words, this operation can be said to be stripping away a part of the solid model. In the figure, 17 is the solid model, 18 is the boundary picked up by the mouse, and 1
9 is a shell model. In this example, s S'l l
sl, l s, is the shell model surface, and the shell model surface S,′ is the vertex vl + V on the boundary line as shown in the figure.
It is specified by picking up t r Vt + va. Also, the shell model surface s- has the vertex Vt +
By picking up v31 V6 + V7, shell model surface S1 becomes vertex v3 + v41 v51
Each is designated by picking up va.

The direction of the peeled surface S:,≦,S; is inherited so as to be the same as the direction of the surface of the solid model 17 (inheritance of surface direction). Namely.

Regardless of whether the boundary line 18 of the surface to be peeled off is traced clockwise or counterclockwise, it is automatically corrected so that it is in the same direction as the surface of the solid model 17. This is the parameters a and b of the normal vector of the surface of the solid model 17 and the normal vector of the surface of the peeled shell model.
, c are determined by determining whether the signs are the same.

As a result, the surface S of the shell model: + S−+ S,
The vertex sequence of ' is v1°V - + y? -+y8-y,
-+ V3°v6°v7·v3°v4°vr+v6 (same direction as the surface of the solid model 17), and is stored in the shell model data section 6 as final shell model data.

When this shell model data is input, the mesh generation function unit 4, as shown in FIG. All directions are generated by inheriting the direction of the surface of the shell model data. In FIG. 6, s, l St p sl, surrounded by solid lines, are shell models, and M, ~M, , surrounded by broken lines, are mesh models. The inheritance method is the same as the method used to convert the Rad model to the shell model. Furthermore, as shown in I to ■ in FIG. 8, even if the mesh is locally cut finely, the direction of the mesh surface can be inherited in the same way.

In addition, I in the figure indicates the surface direction of M3 (see Figure 6), and ■ indicates the direction of M3 (see Figure 6).
, ■ is the surface direction of M, ■ is the surface direction of M7. The surface direction of each is inherited.

According to this method, the analyst only needs to consider the number of divisions when generating the mesh, and can concentrate on the original analysis work without worrying about the orientation of shell elements specific to the FEM solver. Furthermore, it is possible to prevent errors in specifying the orientation of shell elements when changing the mesh division (particularly when making the mesh locally finer), which has frequently occurred in the past.

The above example describes the case where one shell model is generated from one solid model.

Next, we will explain the case of generating one shell model from multiple solid models. When generating the H-shaped shell model shown in Figure 10 (a), three solid models shown in Figure 10 (b) will be generated. generate. At this time, the solid model is generated so that one side (shaded area) of each part corresponds to the side of the shell model. That is, at this point, the orientation and position of the surface of the shell model are determined.

Next, using the solid-shell model conversion function, the shaded area of the solid model is stripped off to generate the shell model shown in FIG. 3(c). At this time, the direction of the surface of the solid model is inherited by the shell model using the method described above. Next, these three shell models are integrated by a joining process, which is one of the solid-shell model conversion functions [see the same figure (d>)].

The completed shell model shown in FIG. 4(e) is generated.

In this joining process, when a solid model is generated in advance, the direction and position of the surfaces converted to the shell model are generated corresponding to the completed shell model, so vertices with the same coordinate values are connected with the mouse. You can pick it up and specify it. Alternatively, it is also possible to automatically search for the same coordinate values of the three shell models using a program and to change the correspondence.

According to this method, even if the shell model is complex, there is no need for extra set processing, and all that is required is to develop a solid modeling function, and there is no need to develop a modeling function exclusively for shell models, which shortens the development time and Development man-hours can be reduced.

Also, it is very easy to check the inside and outside directions of the first surface, and it is possible to display the inside and outside in different colors, for example, red and blue, or to display the direction of the first surface with arrows indicating vectors, making it extremely easy to understand.

Although the present invention requires a shape model, the technique is B-r
In addition to eps, for example, C, S, G (Constr
uct ive Sol id Geffnetn
Similar effects can be achieved using other modeling techniques such as y ).

In the previous embodiment, the case of FBM analysis was explained, but it is also applicable as an analytical model such as boundary element method (BEM) or finite difference method (FDM).

〔Effect of the invention〕

According to the present invention, a solid model can be used to generate a shell model, so there is no need for a modeler dedicated to shell models. Also, the surface orientation of the solid model can be directly inherited to the shell model.

The direction of the mesh surface can be automatically determined when creating a mesh or changing mesh data.

Therefore, it is possible to perform mesh division processing by inputting only the number of divisions of the mesh, and it is possible to eliminate the wasted calculation time due to the incorrect specification of the orientation of the mesh surface, which conventionally occurred frequently when changing the mesh shape, and to reduce the analysis work. Efficiency can be improved.

[Brief explanation of drawings]

1 to 10 are for explaining the present invention in detail. FIG. 1 is a schematic configuration diagram of a shell model generation device for FEM analysis, and FIG. 2 is a drum body plate as an example of an object to be analyzed. 3(a) is a perspective view of a cylinder to be analyzed, FIG. a) is a perspective view expressing solid model data as a polyhedron;
b) is an enlarged view of one of the surfaces, Figure 5 is an explanatory diagram showing the state in which the shell model is peeled off from the solid model, and Figure 6
The figure is an explanatory diagram showing an example of the number of divisions for mesh cutting. Figure 7 is an explanatory diagram showing the inheritance of the shell model data in the plane direction, Figure 8 is an explanatory diagram showing the state where the mesh is locally finely cut, and Figure 9 (a3 is a cross-sectional view of the shell model; b) is a perspective view of a cylinder, and FIG. 10 is a flowchart for generating one shell model from a plurality of solid models. FIG. 11 is a flowchart of the conventional stacking method, and FIG.
The figure is a flowchart of a conventional shape modeler system.
FIG. 3 is a perspective view showing an example of a shell model. FIG. 14(a) is a partial sectional view of a spherical tank to be analyzed, and FIG. 14(b) is an explanatory diagram of normal vectors. 2...Solid modeling function section, 3...
・・Solid 9/Shell model conversion function section% 4・・・・
... mesh generation function section, 5 ... solid model data section, 6 ... ° ... shell model data section, 7
・Old...Meshte-Figure 2 Figure Figure Figure

Claims (1)

[Claims] A solid model generated by the solid modeling function section, comprising a solid modeling function section, a solid/shell model conversion function section, a mesh generation function section, a solid model data section, a shell model data section, and a mesh data section. The solid/shell model conversion function unit converts at least a part of the solid model into a shell model, and inherits the planar direction data of the converted shell model as is from the solid model data. A shell model generation device characterized by: