JPH113439A - Model generating method for press formation analysis - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a fillet plane with such a simple operation as to input a radius by generating a model for a press formation analysis whose corner parts are eliminated and which has a smooth shape. SOLUTION: Line data is inputted from a keyboard, and a mesh-shaped form that is shown in Figure (a) is produced based on the data. Next, when a radius (fillet R value) is inputted, nodes that are included in ridge lines of graphics in Figure (a) are moved in the direction of normal lines of the nodes. A graphic form that is finally shown in Figure (b) is generated with the movement. The graphics shown in Figure (c) is generated by shifting nodes that exist in a fixed distance from the ridge lines by respectively different distances in order to smooth (apply mesh R) a form that is produced in this way. That is, the movement of nodes of the ridge line and the form correction of the mesh are recursively performed by giving a fillet R value to the ridge line of line data, and round processing is directly and easily performed of finite element mesh.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a model for press forming analysis which can relatively easily prepare a model for press forming analysis for studying press formability.

[0002]

2. Description of the Related Art Conventionally, in order to obtain a high-quality press-formed product, a mold shape has been studied before starting mass production. Conventionally, a mold that is considered to be optimal is actually manufactured, the product is actually pressed with this mold, and the product after pressing is analyzed by three-dimensional molding (with or without shape defects, chipping, cracks, etc.). The presence / absence of the mold is corrected, and the process is repeated to mass-produce a mold having the best shape (a mold capable of obtaining a high-quality press product).

[0003] However, the analysis of the press product and the correction of the mold shape require a great deal of time and cost.
It will take a lot of time before mass production can be achieved. For this reason, recently, for example, Japanese Patent Application No. 5-64.
No. 42, Japanese Patent Application No. 5-322535, simulation (pressing a virtual material with a virtual die) before press molding, before actually manufacturing a die. Techniques have been developed that can predict the shape defects that will occur and their countermeasures in advance, and search for the optimal mold shape.

[0004]

According to such a simulation, however, there is no need to create a mold, but on the other hand, it is very necessary to input data for creating an optimum mold shape. There is a problem that it takes time.

More specifically, when forming a mold shape, it is necessary to prepare model data for plate forming analysis, that is, an analysis model for press forming from the line data of an ideal formed product (the corner portion is formed by a model). If there is, the calculation will not be performed accurately due to the inflow of the material during the molding process), but the creation of the model uses a smooth fillet shape that can not be created from the input line data using the existing method It is required to separately create the fillet shape and add the fillet shape to the press-forming analysis model created from the line data. Therefore, if the line data does not include data on the fillet shape, it takes a very long time to create the fillet shape.

The time required for forming the fillet shape increases exponentially as the shape of the molded product becomes more complicated.
Depending on the shape of the molded article, it may take a long time to be no different from the method of actually manufacturing and correcting a mold as in the conventional case.

SUMMARY OF THE INVENTION The present invention has been made to solve such a conventional problem. A fillet surface is formed by a simple operation of inputting a radius to a press forming analysis model created from line data. It is an object of the present invention to provide a method for creating a model for press forming analysis that can form a model.

[0008]

The present invention for achieving the above object is constituted as follows.

According to a first aspect of the present invention, there is provided a press-forming analysis model having a corner portion, without forming a fillet surface for making the corner portion a smooth shape, without forming a corner having a smooth shape. It is characterized in that a model for press forming analysis is created.

According to a second aspect of the present invention, there is provided a first step of preparing a mesh-shaped press-formed model from a press-formed analysis model composed of line data, and a method of forming a mesh-shaped press-formed model on a ridge line forming a corner of the mesh-shaped press formed model. Extraction of nodes of the second
A third step of calculating a normal vector for moving a node on the extracted ridge line from normal vectors of both sides sharing the ridge line, and calculating the node on the extracted ridge line A fourth step of moving in the direction of the normal vector, and a certain distance from the ridge through the moved node from a node on one of the two surfaces sharing the ridge at a certain distance from the ridge. A fifth step of moving all nodes existing on both sides sharing the ridge line at a fixed distance from the ridge line so that an arc is drawn up to a node on the other surface sharing the distant ridge line. It is characterized by being performed.

According to a third aspect of the present invention, in the second aspect, the third step includes a step of calculating a normal vector of each mesh from meshes included on both sides sharing the ridge line. Moving the nodes on the extracted ridge line included in each mesh according to the calculated normal vector.

According to a fourth aspect of the present invention, in the second aspect of the present invention, the fourth step includes inputting a radius of the arc formed in the fifth step; Moving the node on the extracted ridge line in the direction of the calculated normal vector so as to be located at a corresponding distance.

According to a fifth aspect of the present invention, there is provided a first step in which a mesh-shaped press-formed model is created from a press-formed analysis model composed of line data, and a ridge line forming a corner portion of the mesh-shaped press-formed model. Extraction of nodes of the second
A third step of calculating a normal vector for moving a node on the extracted ridge line from a normal vector of both sides sharing the ridge line, and inputting a radius of an arc; So that it is located at a distance corresponding to the radius,
A fourth step of moving a node on the extracted ridge in the direction of the calculated normal vector, and nodes present on both sides sharing the ridge from the ridge based on the radius of the input arc. A fifth step of calculating a range in which to move, and moving all nodes existing on both sides sharing the ridge line within the calculated range from the ridge line such that an arc passing through the moved node is drawn. And a sixth step.

[0014]

The present invention configured as described above has the following effects. The invention according to claim 1 is based on a press-forming analysis model having corners, and without forming a fillet surface for making the corners smooth, a press-forming analysis of a smooth shape with the corners removed. Since the press model is prepared, the press forming analysis model can be prepared in a shorter time than in the past, and the press formability can be easily analyzed.

According to a second aspect of the present invention, a mesh-shaped press-formed model is created, nodes on ridges forming corners thereof are extracted, and ridges extracted from normal vectors on both sides sharing the ridges. Calculate the normal vector for moving the upper node, move the node on the extracted ridge in the direction of the normal vector, and move one of the two sides sharing the ridge at a certain distance from the ridge From the node on the surface of the surface to the node on the other surface that shares the ridge line that is a certain distance away from the ridge line, the ridge line that is a certain distance away from that ridge is drawn so that an arc is drawn By moving all the nodes existing on both sides to create a smooth shape press-forming analysis model with corners removed, the press-forming analysis model is faster than in the past. Create Can be, for press forming analysis is easily so.

According to the third aspect of the present invention, since a normal vector for moving a node on a ridge line is calculated from a mesh, a smooth shape press in which corners are removed from line data. A molding analysis model can be created.

According to the fourth aspect of the present invention, since an arc is drawn in accordance with the input radius, a press having a smooth shape in which corners are removed from the line data only by the operation of inputting the radius. A molding analysis model can be created.

According to a fifth aspect of the present invention, a mesh-shaped press-formed model is created, nodes on ridges forming corners thereof are extracted, and ridges extracted from normal vectors on both sides sharing the ridges. The normal vector for moving the upper node is calculated, the radius of the arc is input, and the method is calculated so that the range of moving the node on the ridgeline is located at a distance corresponding to the input radius. Move in the direction of the line vector and move the nodes existing on both sides sharing the ridge within the range calculated from the ridge so that an arc passing through the moved node is drawn, so enter the radius By simply performing this operation, it is possible to create a press-shape analysis model having a smooth shape with the corners removed from the line data in a shorter time than in the past, making it possible to analyze press-formability. It will be performed so to.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a configuration of one device used to carry out the method of the present invention.

This apparatus is a computer capable of performing image processing, and the image processing based on the input data is performed by the graphic operation device 10. Input of a line data of a press-formed model described later and a radius for drawing an arc at a corner thereof is performed by the keyboard 15. The press forming analysis model obtained after the image processing is performed by the graphic operation device 10 is displayed on a display device (for example, a CRT, an LCD, a plasma display, etc.) 20.

FIG. 2 is a flowchart showing a procedure of a method for preparing a model for press forming analysis according to the present invention. Before describing the specific processing of this flowchart, the outline of the method of the present invention will be described with reference to FIG.

Line data (wire frame model data) is input from the keyboard 15 and the graphic operation device 10 uses the data to generate a mesh-like shape (finite element generated from the line data) as shown in FIG. mesh)
Create Then, the intersection of the mesh is defined as a node. Next, a radius r (fillet R
When (value) is input, the nodes included in the ridge line of the figure in FIG. 9A are moved in the normal direction of the nodes based on the value of the radius r. By this movement, a figure as shown in FIG. In order to smooth the shape created in this way (to perform R-attachment of the mesh), all the nodes located at a fixed distance from the above-mentioned ridge line are respectively moved by different distances (the shape correction by the Laplacian method is repeatedly performed). Then, a figure as shown in FIG.

That is, by giving a fillet R value to the edge of the line data, the node of the edge is moved and the shape of the mesh is corrected repeatedly, and the finite element mesh generated from the line data is directly and simply converted. The rounding process is performed.

As described above, since the rounding process is directly performed on the finite element mesh, there is no corner by only the operation of inputting the radius of the corner to be smoothed without creating surface data or a fillet surface. It is possible to obtain a figure with a smooth shape, eliminating the need to create a fillet surface that fits into that part to remove corners as in the past, making it possible to easily and reliably process fillets with complicated shapes This makes it possible to create a press-forming analysis model from line data in a relatively short time and easily.

Next, a method for preparing a model for press forming analysis according to the present invention will be described in detail with reference to FIGS. 4 to 21. First, when line data (wire frame model data) is input from the keyboard 15,
The graphic operation device 10 creates a mesh-like (finite element mesh) shape as shown in FIG. 4 based on the input line data (data for expressing only the outline of the shape). Then, an intersection (for example, a black circle part in the figure) of the line in this figure is defined as a node, and a line of a part constituting a corner (a mountain fold part, a valley fold part) of the figure is defined as a ridge line. . Therefore, the nodes on the ridge line are mountain-folded portions in the portions indicated by black circles in FIG.
This is the intersection included in the ridgeline of the valley fold.

In order to move a node included in the ridge line, it is necessary to calculate a normal vector indicating the moving direction of the node as shown in FIG. This normal vector must be calculated for each node. If this calculation is not performed, it will not be possible to finally create a smooth press-forming analysis model.

This normal vector is created specifically as follows. This normal vector is shown in FIG.
As shown in the figure, a normal vector on both sides sharing the ridge line (R ridge line) or a normal vector n1 of a mesh included on both sides sharing the ridge line is obtained, and the obtained normal vector n1 includes the ridge line and the mesh. Is obtained as the sum of vectors multiplied by the angle θ1 made by That is,

[0028]

(Equation 1)

Next, as shown in FIG. 7, a normal vector Na, N
The angle α between the meshes is obtained from b. In terms of accuracy, it is desirable to calculate from all meshes having nodes, but in this case, it is calculated from two meshes between edges. That is,

[0030]

(Equation 2)

As described above, when the process of calculating the normal vector of the node on the ridge line of the line data from the angle of the surrounding mesh is completed, the fillet radius r is input as the fillet R value from the keyboard 15 (S3). The input fillet radius r is read, and the node on the ridge is moved through the following operation.

In this process, for example, a process in a stage before performing a process of rounding a corner portion (including both a convex ridge line and a concave ridge line) having a shape as shown in FIG. It is.

The radius of the fillet r is determined by rounding the corners of the finite element mesh as shown in FIG.
When only the fillet radius r of the ridge portion is input and the corner of the finite element mesh shape as shown in FIG. 10 is rounded, the intersection of the fillet radius r of the ridge portion and the ridge line having a different normal vector, that is, It is necessary to input the fillet radius r of the corner.

The movement amount I is calculated using the angle α between the meshes obtained in the step S2 and the input fillet radius r. For example, in the case of the shape shown in FIG. 8, the moving direction of the node in this case is such that the convex ridge moves the node to the back side of the figure, and the concave ridge moves the node to the front side of the figure. When the moving direction of the node is determined, each node is moved in the direction of the normal vector calculated in step S1, as shown in FIG. 12 or FIG.

The movement amount I is calculated as follows. This calculation method will be described with reference to FIG. As shown in the figure, the angle α between the meshes calculated in step S2, the fillet radius r input for the ridge line, S1
If the position of the node before movement is Pc and the position of the node after movement is Pn,
The position Pn of the node after the movement is: Pn = Pc + I · Nv Further, from sin (α / 2) = r / (r + I), I = [1−sin (α / 2)] · r / sin (α / 2 ) To determine the movement amount I. This movement amount I is obtained for each node. Then, the node is moved along the normal vector by the obtained moving amount. When this processing is performed for all the ridge nodes where the fillet radius is input, a mesh shape as shown in FIG. 12 or FIG. 13 is finally obtained.

As described above, for the nodes located at the ridge lines of the corners of the mesh shape, the amount of movement is calculated using the scissor angle α of the nodes calculated from the surrounding mesh and the input fillet radius r, and Processing is performed to move the node along the direction of the normal vector obtained for the node.

For the nodes forming the vertices of the corners, the amount of movement I cannot be calculated by the above-described method. Therefore, the rolling ball method which is one of the fillet surface generation methods is used for this portion. According to the concept of, the following calculation is performed. This will be described with reference to FIG.

First, according to the input fillet radius r, it is checked whether the surrounding ridge line is concave or convex with respect to the node of the corner vertex. This is because it is not known to which side the node should be moved. For example, in the case of the shape shown in FIG. 8, the convex ridge line cannot be rounded unless the node is moved to the back side of the figure, and the concave ridge line cannot be rounded unless the node is moved to the front side of the figure. It is.

The amount of movement of the node at the corner vertex in three-dimensional coordinates is I, and the amount of movement when viewed from the left side (X coordinate) is I
b, the movement amount when this is viewed from the right side (Y coordinate) is Ia
Then, the movement amount I is

[0040]

(Equation 3)

Here, Ia = r / tan (β / 2) Ib = [1-sin (γ / 2)] · r / sin (γ /
2).

The nodes at the vertices of the corners are moved by the movement amount I inward for the convex ridges and outward for the concave ridges. The final press-forming analysis model is obtained by moving the corners and the nodes at the vertices of the corners in the manner described above and performing rounding processing described later (S4).

Next, in order to perform a so-called rounding process for obtaining a smooth shape with rounded corners, as shown in FIG. 15, a fillet width (rounding) indicating a range of nodes in the mesh shape to be moved. Area). This calculation is performed as follows based on the angle (scissor angle) α between the meshes previously obtained for all corners and the vertices of all corners, and the input fillet radius r.

The fillet width h is calculated by h = r / tan (α / 2) as shown in FIG.

Therefore, all nodes existing within the calculated fillet width h, in other words, nodes whose distance from the ridge line is smaller than the fillet width h, have their corresponding nodes modified by the following Laplacian method. Is performed (S5).

The shape correction (smoothing process) is performed by performing the following equation.

Here, as shown in FIG. 17, i,
j and k represent the three vertices of one triangle, Pi, Pj and Pk represent the coordinates of these three vertices, and n represents the number of triangles sharing the point i. Then

[0048]

(Equation 4)

This equation shows that the point i is moved to the position of the center of gravity of the area of all the triangles having the point as the vertex. Note that this equation is for the case where all the meshes sharing the point i are triangular. However, even in the case where a quadrangle exists, the same calculation may be performed by obtaining the center of gravity.

In order to make the corners and the vertices of the corners smooth, it is preferable to repeat this smoothing process a plurality of times. Here, it is considered that it is preferable to determine the number of repetitions as a factor of the number of nodes existing within the fillet width h in the direction orthogonal to the ridge line. The number of repetitions is obtained by the following equation.

It = A · Nh ^B where Nh is Nh = number of nodes around the edge / number of nodes on the edge, and Nh is Nh for the vertex of the corner. = The number of nodes around the vertex / the number of edges gathering at the vertex, and A and B are empirical coefficients.

More specifically, in the case of a mesh shape as shown in FIG. 18, the number of nodes existing on the ridge line is four, and the number of nodes existing within the fillet width is one for one surface.
Since there are two, Nh for this surface is 12/4 =
It becomes 3. Since the number of nodes existing on the other surface is eight, Nh on this surface is 8/4 = 2
Becomes If the calculation is performed by applying the empirical values of A and B to this, the number of repetitive calculations for performing the rounding process is obtained.
The movement amounts of all the contact points within the fillet width are calculated by the number of repetitions. By repeating this calculation, the graphic shown in FIG. 18 becomes a graphic with smooth corners as shown in FIG.

In the above-described rounding processing, a circular arc is created based on one radius. However, the fillet radius input to the ridge is given to the node of the ridge. Thus, by giving different radii to the respective nodes, it is also possible to perform a process of rounding the curve as shown in FIG. Such a process is referred to as a gradual fillet process. When the gradual fillet process is designated, a rounding process is performed by calculating a value of an internal division ratio of a fillet radius given to each ridge line. The process of drawing an S-shaped curve as shown in FIG. 21 is referred to as a preceding R process. When the preceding R process is specified, a ridge line to which an R is added first is usually used. Is rounded, and only the mesh shape correction is performed on the ridge line to be rounded later.

Thus, the “gradual change fillet processing”
By performing the "preceding R process", a smoother shape can be obtained (S6).

FIG. 22 shows an example of a mesh-shaped press-forming analysis model obtained as a result of performing the method of the present invention.
23 and FIG. It can be clearly seen that the corners are removed to form a smooth shape.

FIGS. 24 and 25 show a press-forming analysis model of any shape as a result of applying the method of the present invention to a mesh-shaped press-forming model created based on input line data. Is obtained. It can be clearly seen that the corners are removed to form a smooth shape.

As described above, according to the present invention, a smooth press-forming analysis model can be created only by inputting the fillet radius, so that the time required for creating the model can be greatly reduced. become able to. When the present invention is actually applied to a pressed part of an automobile, the shape of the part is often very complicated, so that the effect of increasing the efficiency of model creation is incalculable.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an apparatus for performing a method of the present invention.

FIG. 2 is a flowchart showing a procedure of the method of the present invention.

FIG. 3 is a diagram for explaining a schematic procedure of the method of the present invention.

FIG. 4 is a diagram for explaining a node moving process;

FIG. 5 is a diagram for explaining a node moving process;

FIG. 6 is a diagram for explaining a node moving process;

FIG. 7 is a diagram for explaining a node moving process;

FIG. 8 is a diagram for explaining a node moving process;

FIG. 9 is a diagram for explaining a node moving process;

FIG. 10 is a diagram for explaining a node moving process;

FIG. 11 is a diagram for explaining a node moving process;

FIG. 12 is a diagram for explaining a node moving process;

FIG. 13 is a diagram for explaining a node moving process;

FIG. 14 is a diagram illustrating a smoothing process.

FIG. 15 is a diagram illustrating a smoothing process.

FIG. 16 is a diagram illustrating a smoothing process.

FIG. 17 is a diagram illustrating a smoothing process.

FIG. 18 is a diagram illustrating a smoothing process.

FIG. 19 is a diagram illustrating a smoothing process.

FIG. 20 is a diagram illustrating a smoothing process.

FIG. 21 is a diagram illustrating a smoothing process.

FIG. 22 is a diagram showing an example of a shape obtained after processing by the method of the present invention.

FIG. 23 is a diagram showing an example of a shape obtained after processing by the method of the present invention.

FIG. 24 is a diagram showing a graphic (input graphic) before processing according to the method of the present invention.

FIG. 25 is a diagram showing a figure after applying the method of the present invention to the figure of FIG. 24;

[Explanation of symbols]

 10: Graphic calculation device, 15: Keyboard, 20: Display device.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Ryuji Kawashima 2 Nissan Motor Co., Ltd., Takaracho, Kanagawa-ku, Yokohama, Kanagawa

Claims (5)

[Claims] 1. A press-forming analysis model having a smooth shape with the corners removed from the press-forming analysis model having the corners without creating a fillet surface for making the corners a smooth shape. A method for creating a model for press forming analysis, characterized in that: 2. A first step of creating a mesh-shaped press-forming model from a press-forming analysis model consisting of line data, and a second step of extracting nodes on ridge lines forming corners of the mesh-shaped press-forming model. A third step of calculating a normal vector for moving a node on the extracted ridge line from normal vectors of both sides sharing the ridge line; and calculating the node on the extracted ridge line A fourth step of moving in the direction of the normal vector, and from a node on one of the two surfaces sharing the ridge line separated by a certain distance from the ridge line, a fixed distance from the ridge line through the moved node Fifth step of moving all nodes existing on both sides sharing the ridge line at a certain distance from the ridge line so that an arc is drawn up to a node on the other surface sharing the distant ridge line Model generating method for press forming analysis, characterized in that they are composed of. 3. The third step includes: calculating a normal vector of each of the meshes from meshes included on both sides sharing the ridge line; and calculating a normal vector of each of the meshes according to the calculated normal vector. Moving the nodes on the extracted ridge line included in the method. 3. The method for creating a model for press forming analysis according to claim 2, wherein 4. The step of inputting a radius of the arc formed in the fifth step, the step of: inputting a radius of the arc formed in the fifth step; Moving the nodes in the direction of the calculated normal vector. 5. A first step of creating a mesh-shaped press-forming model from a press-forming analysis model composed of line data, and a second step of extracting nodes on ridge lines forming corners of the mesh-shaped press-forming model. A third step of calculating a normal vector for moving a node on the extracted ridge line from normal vectors of both sides sharing the ridge line; and inputting a radius of an arc, and A fourth step of moving a node on the extracted ridge line in a direction of the calculated normal vector so as to be located at a distance corresponding to a radius, and based on the radius of the inputted arc, A fifth step of calculating a range for moving nodes existing on both sides sharing the ridge line from the ridge line, and all the nodes existing on both sides sharing the ridge line within the calculated range from the ridge line, Sixth step and press forming analysis model creation method, characterized in that it consists of moving as an arc through the nodes and serial movement is drawn.