JP7013248B2 - Fitting part analysis model creation method, fitting part analysis model creation device, program, and analysis model creation method - Google Patents

Description

The present invention relates to a technique for suppressing mesh interference generated at a fitting portion of a model in finite element analysis.

In model analysis by CAE (Computer Aided Engineering), mesh interference may occur when the mesh size of each part is different or the mesh position is different at the fitting part connected by parts such as screws and screws. be. Then, if the calculation process is executed in a state where the interference of the mesh is generated, problems such as obtaining an analysis result significantly different from the actual one or interrupting the calculation process due to an error occur.

Therefore, before executing the calculation process, it is necessary to check whether the mesh interferes and correct the mesh so that the mesh interference does not occur. However, this has a problem that, for example, when the scale of the analysis model is large, a large number of fitting portions are included in the analysis model, and therefore a huge number of man-hours are required to check all of them.

Therefore, in order to deal with such problems, a technique for automatically checking the fitting part where mesh interference may occur and modifying the mesh so that the mesh interference does not occur in the fitting part is available. It has been proposed (Patent Document 1). Specifically, the technique of Patent Document 1 extracts screws and screw holes from the analysis model and replaces them with a prepared mesh without interference.

International Publication No. 2007/0776228

However, since the fitting portion can actually take various shapes such as a cross-shaped caulking shaft and an oblong hole, the technique of Patent Document 1 uses a mesh in advance for all shapes. Must be prepared. It is also difficult to automatically determine which mesh should be used for the shape of the model.

The present invention has been made in view of these problems, and is to automatically create a mesh in which interference is suppressed without preparing a mesh corresponding to the fitting portion of the model in advance.

In order to achieve the above object, the fitting part analysis model creation method of the present invention is configured by a convex curved surface in a hole formed by the concave curved surface based on the positional relationship between the concave curved surface and the convex curved surface included in the three-dimensional model. The fitting part extraction step for extracting the fitting part for fitting the shaft, and the mesh when the convex curved surface constituting the shaft is modeled based on the geometric information and the position information of the fitting part make the hole. The mesh division number calculation step for calculating the number of mesh divisions, the concave curved surface constituting the hole, and the axis are configured so that the amount of penetration into the mesh when the concave curved surface to be constructed is modeled is equal to or less than the allowable penetration amount. It is characterized by including a mesh creating step of creating a mesh in the fitting portion by allocating a polyhedral mesh to a region divided based on the calculated number of mesh divisions for each of the convex curved surfaces.

According to the present invention, it is possible to automatically create a mesh that suppresses interference without preparing a mesh corresponding to the fitting portion of the model in advance.

It is a block diagram which shows the structure of the analysis model creation apparatus. It is a flowchart which shows the procedure of the analysis model creation processing in an analysis model creation apparatus. It is a figure for demonstrating the relationship between the penetration amount and the number of mesh divisions. It is a flowchart which shows the detailed procedure of the mesh making process in a fitting part. It is a figure which shows the example which applied the mesh making process in the fitting part of the analysis model.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the present invention, and not all combinations of features described in the present embodiment are essential for the means for solving the present invention.

First, the configuration of the analysis model creation device will be described with reference to FIG. FIG. 1 is a block diagram schematically showing the configuration of an analysis model creation device. The analysis model creation device shown in FIG. 1 can be configured by installing a program for creating an analysis model on a PC (Personal Computer). The analysis model creating device also functions as a fitting portion analysis model creating device for creating a mesh in the fitting portion.

As shown in FIG. 1, the analysis model creation device 1 includes an arithmetic processing unit 10, a storage unit 20, an input control unit 30, and an output control unit 40. The analysis model creation device 1 includes an input device 50 and an output device. Each of the 60s is connected.

The arithmetic processing unit 10 includes a CPU (Central Processing Unit) and executes various arithmetic processes based on software such as a program for creating an analysis model (fitting unit model). The arithmetic processing unit 10 functions as, for example, a fitting unit extraction means, a mesh division number calculation means, and a mesh creation means in relation to the processing contents described later.

The storage unit 20 is composed of a storage device such as an HDD (Hard Disk Drive), a RAM (Random Access Memory), and a ROM (Read Only Memory). The storage unit 20 stores information about software (program) related to the arithmetic processing unit 10, a CAD (Computer-Aided Design) model to be processed, and the like.

The input control unit 30 controls operation (input) information from the input device 50 such as a keyboard and a mouse, and transmits the information to the arithmetic processing unit 10 as needed. The output control unit 40 controls screen output to an output device 60 such as a liquid crystal display, a CRT (Cathode Ray Tube), or a plasma display. Specifically, the output control unit 40 can display image information (for example, character information, still image information, moving image information, etc.) configured based on the information transmitted by the arithmetic processing unit 10 on the output device 60. Convert to format.

Hereinafter, the process of creating a mesh in the analysis model (particularly, the fitting portion of the analysis model) using the analysis model creation device 1 shown in FIG. 1 will be described. The three-dimensional model information handled in the analysis model creation process includes a list of the shape information of the parts, and the shape information of the parts is the geometry of the faces, ridges, vertices, etc., which are the shape elements constituting the parts, respectively. Includes information and location information indicating the adjacency between each shape element. In addition, each shape element is given a unique label to identify the shape element, and in addition, the phase information indicating the adjacency relationship between the surface and the ridge line and the ridge line and the apex includes the shape element. Contains a list of pairs of labels.

Next, the procedure of the analysis model creation process in the analysis model creation device will be described with reference to the flowchart of FIG. In step S10, the arithmetic processing unit 10 searches all the pairs of the concave curved surface constituting the hole of the fitting portion and the convex curved surface constituting the axis (that is, the fitting portion) from the analysis target. That is, the arithmetic processing unit 10 executes the fitting unit extraction process.

Specifically, in step S10, a pair of concave curved surface and convex curved surface is searched so that the distance between the concave curved surface and the convex curved surface (between faces) is within a predetermined threshold value set by the user. A predetermined threshold value regarding the distance between the surfaces is input by the user in the input device 50 of FIG. 1 and stored in the storage unit 20 via the input control unit 30 and the arithmetic processing unit 10.

When the arithmetic processing unit 10 searches for the fitting unit (S10), it separates the fitting unit and the other parts, and branches the subsequent processing. Specifically, the processing of steps S20 and S30 is executed for the fitting portion, and the processing of step S40 is executed for the portion other than the fitting portion.

In step S20, for each of the pair (that is, the fitting portion) of the concave curved surface and the convex curved surface searched in step S10, the worst value of the penetration amount of the mesh created on the curved surface from the geometric information of the concave curved surface and the convex curved surface. The number of mesh divisions is calculated so that is less than or equal to the allowable penetration amount. That is, the arithmetic processing unit 10 executes the mesh division number calculation process. The permissible penetration amount is input by the user in the input device 50 of FIG. 1 and stored in the storage unit 20 via the input control unit 30 and the arithmetic processing unit 10. Hereinafter, the description regarding the calculation of the number of mesh divisions will be supplemented with reference to FIG.

FIG. 3 is a diagram for explaining the relationship between the penetration amount and the number of mesh divisions. In FIG. 3, both the concave curved surface and the convex curved surface have the same central axis, and when the concave curved surface and the convex curved surface are modeled, the polyhedral mesh (polygon) inscribed in the axis is a hole in the fitting portion. It shows the state of penetrating into the polyhedral mesh inscribed in. In this case, the required number of mesh divisions is calculated by, for example, the following equation, where the allowable penetration amount is ε, the hole arc length is l _h , the hole radius is _rh , and the axis radius is r _s . The radius.

The worst value of the penetration amount of the mesh is the polyhedral mesh inscribed in the shaft and the polyhedral mesh inscribed in the hole of the fitting portion in the positional relationship between the polyhedral mesh inscribed in the shaft and the polyhedral mesh inscribed in the hole of the fitting portion. It is shown as the amount of penetration in the most intrusive state. Further, in the above description, it is assumed that the central axis of the concave curved surface and the central axis of the convex curved surface are the same, but when the central axis of the concave curved surface and the central axis of the convex curved surface are deviated from each other, for example, the axis. The number of mesh divisions may be calculated by adding the amount of deviation of the axis to the radius r _s of. In addition, it is also possible to multiply the number of mesh divisions calculated by using the above equation by a certain amount, change the value obtained by multiplying the number by a certain amount as the number of mesh divisions, and execute the subsequent processing. However, in this case, in order to prevent the mesh to be created (generated) from becoming too small, the number of mesh divisions can be determined so as not to be larger than a predetermined upper limit set by the user.

In addition, when at least one of the concave curved surface and the convex curved surface is composed of a free curved surface other than the cylindrical surface, the free curved surface is divided into subsections, and each of the divided subsections is approximated to a cylindrical surface. , The number of mesh divisions may be calculated using the above equation, and the maximum value thereof may be used. However, in this case as well, in order to prevent the created mesh from becoming too small, the number of mesh divisions may be determined so as not to be larger than a predetermined upper limit set by the user. can.

In step S30, for each of the pair (that is, the fitting portion) of the concave curved surface and the convex curved surface searched in step S10, the number of mesh divisions calculated (determined) in step S20 is calculated on the curved surface of the concave curved surface and the convex curved surface. Create a mesh based on it. Hereinafter, regarding the process in step S30 of FIG. 2, a detailed procedure of the mesh creation process in the fitting portion shown in the flowchart of FIG. 4 and an application example of the mesh creation process in the fitting portion using the schematic model of FIG. Is used to supplement the explanation.

As a mesh creation process in the fitting portion, in step S31 of FIG. 4, the arithmetic processing unit 10 is one of a pair of a concave curved surface and a convex curved surface for which the number of mesh divisions is calculated in step S20 of FIG. Select a pair of concave and convex surfaces. Next, in step S32, the central axis of the concave curved surface and the convex curved surface in the selected pair of concave curved surface and convex curved surface is estimated, and further, as shown in FIG. 5A, the estimated central axis is set to the estimated central axis. Based on this, a common (same) unit cylindrical surface is generated. The central axis can be estimated, for example, by extracting a plurality of arbitrary points on a concave or convex curved surface and finding the central axis of the cylindrical surface that minimizes the distance from those points. can.

In step S33, a pair of a concave curved surface and a convex curved surface (that is, each of the concave curved surface and the convex curved surface) selected in step S31 is projected onto the unit cylindrical surface created in step S32, and is shown in FIG. 5 (b). Thus, the region where the concave curved surface and the convex curved surface intersect is obtained. That is, the arithmetic processing unit 10 executes the intersection area calculation processing.

In step S34, as shown in FIG. 5C, a grid is created (that is, divided into grids) based on the number of mesh divisions calculated in step 20 of FIG. 2 in the intersection region obtained in step S33. do). That is, the arithmetic processing unit 10 executes the grid division processing. Next, in step S35, as shown in FIG. 5D, the grid on the unit cylindrical surface is projected again on the concave and convex curved surfaces, and the nodes of the polyhedral mesh are assigned on the grid points of the grid. In addition, a mesh is created on each of the concave and convex curved surfaces. That is, the arithmetic processing unit 10 executes the node allocation processing. Note that FIG. 5D is shown as a diagram in which the lattice on the unit cylindrical surface is projected again with respect to the axis (that is, the convex curved surface).

Then, in step S36, it is determined whether or not the above processes from steps S32 to S35 have been executed for all the pairs of the concave curved surface and the convex curved surface searched in step S10 of FIG. 2 (that is, the mesh is formed). Determine if it was created). As a result of the determination, if there is a pair of a concave curved surface and a convex curved surface that has not been processed yet (S36 No), the arithmetic processing unit 10 returns the processing to step S31, and the processing is returned to the concave curved surface and the convex curved surface that have not been processed yet. Of the pairs, select any one pair of concave and convex curved surfaces. After that, similarly, by executing the processes from steps S32 to S35, a mesh is created for all the pairs of the concave curved surface constituting the hole of the fitting portion and the convex curved surface constituting the axis. That is, a mesh is created for the fitting portion searched (extracted) in step 10 of FIG.

Here, returning to FIG. 2, the mesh of the portion other than the fitting portion is created by using an arbitrary known (well-known) mesh creating method for the portion of the analysis model other than the fitting portion (S40). .. Then, when the processing of step S30 and the processing of step S40 are completed, the processing of step S50 is executed. In step S50, the created meshes are joined together (that is, the mesh connection process is executed) to create a mesh for the entire analysis model, thereby completing a mesh that can be used for finite element analysis.

As described above, the above processing is executed by the arithmetic processing unit 10 of FIG. 1, and the created mesh is stored in the storage unit 20. The user can confirm the mesh stored in the storage unit 20 in the output device 60. Further, as described above, when the analysis model creation device 1 functions as the fitting portion analysis model creation device, the processes of steps S10, S20, and S30 in FIG. 2 may be executed. In this case, a mesh at the fitting portion is created.

As a supplement, the present invention can be applied even when a mesh (mesh at the fitting portion) has already been created (state) using a commercially available mesh creating tool or the like. In this case, specifically, first, according to the process of steps S20 and S30 in FIG. 2, the number of mesh divisions that suppress the interference of the fitting portion in the portion corresponding to the fitting portion where the existing mesh is created. Is calculated, and a mesh is created with the calculated number of mesh divisions. That is, a mesh at the fitting portion is created based on the calculated number of mesh divisions (however, in this case, the mesh may be created only on the convex curved surface constituting the axis and the concave curved surface constituting the hole). .. Next, among the meshes created in step S30, the meshes on the convex curved surface constituting the axis and the concave curved surface constituting the hole are the existing meshes (to be exact, the convex curved surfaces constituting the axis among the existing meshes). And the mesh other than the mesh on the concave curved surface that constitutes the hole). As a result, the arithmetic processing unit 10 recreates the mesh (that is, executes the mesh recreating process).

In addition, when connecting meshes as described above, if various predetermined conditions are satisfied, it is determined that a mesh of poor quality has been created, and the mesh is located in or around the mesh. It is also possible to execute a process of locally modifying the mesh to be used. Here, as a process of locally modifying the mesh, the arithmetic processing unit 10 executes, for example, a process of joining a mesh having poor quality and a mesh adjacent to the mesh. Further, various predetermined conditions include, for example, a skew angle, a time step Δt in dynamic analysis, a Jacobian value, and the like. Hereinafter, the description of these conditions will be supplemented.

First, the skew angle (for example, the skew angle in a hexahedral mesh) will be described. For hexahedral meshes, the skew angle is calculated for each of the six quadrilaterals that make up the hexahedral mesh. Regarding the skew angle of the quadrangle, first, in one of the combinations of opposite sides of the quadrangle, draw the first line from the midpoint of one side to the midpoint of the other side, and draw this on the other opposite side. The same applies to the combination of, and a second line is drawn. Next, draw a third line perpendicular to the second line with respect to the intersection of the first line and the second line. Further, the angle between the first line and the third line is acquired as a skew angle. Then, these are carried out for each of the six quadrangles constituting the hexahedron mesh as described above, and the largest skew angle among them is acquired as the skew angle of the hexahedron. Finally, it is determined whether or not the acquired skew angle satisfies a predetermined condition (angle range), and if it is satisfied, a process of modifying the mesh is executed.

Next, the time step Δt in the dynamic analysis will be described. The time step Δt in the dynamic analysis is calculated by, for example, the following equation, where l is the representative length of the element (the surface constituting the polyhedral mesh) and c is the stress wave velocity propagating in the element. If the time step Δt in the dynamic analysis is shorter than the unit step of the simulation time, the arithmetic processing unit 10 executes a process of modifying the mesh.

Here, the description of the representative length of each element is supplemented by using a tetrahedral mesh. In the case of a tetrahedral mesh, first, for each of the four nodes of the tetrahedral mesh, the shortest distance from that node to the surface facing the node is calculated. Next, the shortest shortest distance calculated is obtained as the representative length of the element.

Finally, the Jacobian value is expressed as the degree of deviation from the ideal shape of the element, for example, when the Jacobian value ranges from 0.0 to 1.0, it indicates the ideal shape of 1.0. Determine how far away from. Then, if it is more than 1.0 (that is, if it is equal to or less than a predetermined threshold value), the process of modifying the mesh is executed.

The various predetermined conditions and the measures to be taken when the conditions are not satisfied (that is, the modification of the mesh) have been described above. Regarding these, in addition to the re-creation of the mesh at the fitting portion, the connection process in step S50 of FIG. The same can be applied to the above. In addition, although the term curved surface is used in the above description, the curved surface includes a plane, a combination of a plurality of planes, and a combination of a plane and a curved surface.

[Other embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

10 Arithmetic processing unit 20 Storage unit 30 Input control unit 40 Output control unit

Claims (13)

From the positional relationship between the concave curved surface and the convex curved surface included in the 3D model, the fitting portion extraction step for extracting the fitting portion for fitting the axis composed of the convex curved surface into the hole composed of the concave curved surface, and the fitting portion extraction step.
Based on the geometric information and position information of the fitting portion, the amount of penetration of the mesh when modeling the convex curved surface constituting the axis into the mesh when modeling the concave curved surface constituting the hole is permissible. A mesh division number calculation step that calculates the mesh division number so that it is less than the amount,
A mesh for creating a mesh at the fitting portion by allocating a polyhedral mesh to a region divided based on the calculated number of mesh divisions for each of the concave curved surface constituting the hole and the convex curved surface constituting the axis. A method for creating a fitting part analysis model in a fitting part analysis model creation device, which comprises a creation step. When an existing mesh is created in the fitting portion, the mesh on the concave curved surface forming the hole and the convex curved surface forming the axis created in the mesh creation step is connected to the existing mesh. The method for creating a fitting portion analysis model according to claim 1, further comprising a mesh recreating step of recreating the mesh in the fitting portion. The mesh creation step is
A projection step of projecting a concave curved surface constituting the hole and a convex curved surface constituting the axis onto the same unit cylindrical surface,
An intersection area calculation step for calculating an intersection region of a concave curved surface constituting the projected hole and a convex curved surface constituting the projected axis on the same unit cylindrical surface.
A grid division step that divides the intersection region into a grid based on the number of mesh divisions,
It is characterized by including a node assignment step of projecting the grid onto each of the concave curved surface constituting the hole and the convex curved surface constituting the axis, and assigning the nodes of the polyhedral mesh to the grid points of the grid. The method for creating a fitting portion analysis model according to claim 1 or 2. In the mesh division number calculation step, the convex curved surface constituting the axis is the amount by which the mesh when modeling the convex curved surface constituting the axis penetrates into the mesh when modeling the concave curved surface constituting the hole. In the positional relationship between the mesh when modeling the above and the mesh when modeling the concave curved surface that constitutes the hole, the mesh when modeling the convex curved surface that constitutes the axis forms the concave curved surface that constitutes the hole. The fitting portion analysis model according to any one of claims 1 to 3, wherein the number of mesh divisions is calculated using the amount of the state that penetrates the mesh most when modeled. Method. One of claims 1 to 4, wherein in the mesh division number calculation step, the mesh division number is calculated from the geometric information of the concave curved surface constituting the hole and the convex curved surface constituting the axis. The method for creating a fitting part analysis model described in 1. In the mesh division number calculation step, the allowable penetration amount is ε, the arc length of the hole is l _h , the radius of the hole is _rh , and the radius of the axis is r _s .

The fitting portion analysis model creating method according to claim 5, wherein the method is calculated. The fitting portion analysis model according to any one of claims 4 to 6, wherein in the mesh division number calculation step, the calculated mesh division number is multiplied by a certain amount to change the mesh division number. How to make. In the mesh re-creation step, as a result of re-creating the mesh in the fitting portion, among the re-created meshes, a mesh satisfying a predetermined condition, a mesh satisfying the predetermined condition, and the predetermined mesh are satisfied. The fitting portion analysis model creation method according to claim 2, further comprising a step of modifying a mesh located around the mesh satisfying the condition. The fitting portion analysis model creating method according to claim 8, wherein the predetermined condition is any one of a skew angle, a time step Δt in dynamic analysis, and a Jacobian value. The fitting portion extraction step is characterized in that when the distance between the surfaces of the concave curved surface and the convex curved surface included in the three-dimensional model is within a predetermined threshold value, the fitting portion is extracted as the fitting portion. The method for creating a fitting portion analysis model according to any one of items 9 to 9. A program comprising causing a computer to execute the fitting portion analysis model creating method according to any one of claims 1 to 10. From the positional relationship between the concave curved surface and the convex curved surface included in the 3D model, the fitting portion extraction step for extracting the fitting portion for fitting the axis composed of the convex curved surface into the hole composed of the concave curved surface, and the fitting portion extraction step.
In the fitting portion, the mesh when the convex curved surface constituting the axis is modeled becomes the mesh when the concave curved surface constituting the hole is modeled based on the geometric information and the position information of the fitting portion. A mesh division number calculation step for calculating the mesh division number so that the penetration amount is less than the allowable penetration amount, and
A mesh is created by allocating a polyhedral mesh to a region divided based on the calculated number of mesh divisions for each of the concave curved surface constituting the hole and the convex curved surface constituting the axis in the fitting portion. 1 mesh creation step and
A second mesh creation step for creating a mesh in a portion other than the fitting portion,
A method for creating an analysis model in an analysis model creation apparatus, which comprises a first mesh creation step and a mesh connection step for connecting meshes created in the second mesh creation step. A fitting portion extraction means for extracting a fitting portion for fitting an axis composed of a convex curved surface into a hole composed of the concave curved surface from the positional relationship between the concave curved surface and the convex curved surface included in the three-dimensional model.
Based on the geometric information and position information of the fitting portion, the amount of penetration of the mesh when modeling the convex curved surface constituting the axis into the mesh when modeling the concave curved surface constituting the hole is permissible. A mesh division number calculation means for calculating the mesh division number so as to be less than or equal to the amount,
A mesh for creating a mesh at the fitting portion by allocating a polyhedral mesh to a region divided based on the calculated number of mesh divisions for each of the concave curved surface constituting the hole and the convex curved surface constituting the axis. A fitting part analysis model creating device characterized by having a creating means.

Images