JPH0755656A - Method and device for analyzing stress - Google Patents

Abstract

PURPOSE:To form a less distorted mesh with ease and in a short time for a partial model B which is cut out of a total model A. CONSTITUTION:A finite element breaking means 101 breaks a total model A into rough finite elements. A displacement calculation means 102 calculates the displacement of each node (a) of the total model A. A finite element breaking means 105 breaks into fine finite elements a partial model B cut out of the total model A by a cutting means 104. A node detection means 106 detects the coordinates of a node (b) formed on the cut plane of the partial model B. A displacement condition setting means 103 calculates the displacement of the node (b) of the partial model B according to each node (a) of the total model A and sets the displacement at each node (b). A stress analysis means 107 analyzes the stress on the partial model B when the node (b) of the partial model B is displaced by the set displacement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stress analysis method and apparatus for performing stress analysis using finite element division, and more particularly, to a concentrated stress of a local model cut out from an entire model easily and accurately in a short time. The present invention relates to a stress analysis method and device that can be calculated.

[0002]

2. Description of the Related Art Conventionally, each part of graphic data drawn three-dimensionally or two-dimensionally is divided into a mesh shape and divided into a finite number of elements, and the rigidity matrix of each element is made into a simultaneous equation to analyze the whole. Structural analysis by the so-called finite element method is known. In such an analysis method, how to create an appropriate mesh in a short time and with a simple operation, in other words, how to perform finite element division of each surface in a short time and with a simple operation What you do is important.

In such a finite element division, in order to accurately calculate the so-called concentrated stress in a so-called micro portion such as a cutout portion or a stepped portion, it is necessary to divide the element of the micro portion finely. However, if the other macro parts are also finely divided according to the micro parts, FEM (Fi
The number of man-hours for creating the nits Elements Method model becomes large, which causes a problem that the calculation time becomes long and the accuracy deteriorates.

In order to solve such a problem, a calculation procedure called "zooming" has recently been adopted. In "zooming", a relatively coarse finite element division is first performed on the entire model (macro part) to calculate global deformation and stress distribution, and then a local model of appropriate size including stress concentration parts is calculated. Is defined, and fine finite element division is performed only on the local model.

FIG. 9 is a flowchart showing a conventional stress analysis method using "zooming". Here, a case will be described as an example in which the stress in the vicinity of the opening 51 formed in the center of the plate-like body 50 is analyzed as shown in FIG. Although a two-dimensional model is used here for the sake of clarity, the three-dimensional model can be used in almost the same procedure.

In step S201, the operator reads desired graphic data from the database and displays the entire model A on an appropriate display device such as a CRT [Fig. 1].
0]. In step S202, the local model B is defined by surrounding a small area including the opening 51 with a boundary line 53 [FIG. 11]. When the observation target is a three-dimensional model as in many cases, the boundary surface is defined by setting the boundary line for each surface while rotating the entire model A on the display device.

In steps S203 and S204, relatively coarse finite element division is separately performed on the local model B and the rest of the overall model A excluding the local model B [FIG. 12]. By executing the finite element division separately for the global model A and the local model B in this way, the elements can be divided on the boundary line (plane) 53, so that the node c is set on the boundary line 53. You will be able to. In step S205, the FEM calculation is performed on the entire model A including the local model B to obtain the displacement result at each node. FIG. 13 is a diagram showing how the overall model A is deformed when each node c is displaced based on the displacement result.

At step S206, each node c set on the boundary line 53 by the finite element division [FIG. 12].
The coordinate position of is detected. In step S207, only the local model B is displayed, and the outer contour 54 (that is,
The operator manually sets a node b again at each coordinate position on the boundary line 53) corresponding to each of the detected nodes c [FIG. 14]. In this embodiment, five nodes c including the vertices (16 in total) are set on each side of the local model B defined as a quadrangle, so that the response of each side on the contour 54 of the local model B is set. Five nodes b are also set at the positions to be set.

In step S208, the local model B is divided into relatively fine finite elements by utilizing each node b [FIG. 15]. In step S209, in step S2
The displacement result of each node c on the boundary line 53 obtained by the FEM calculation in 05 is given to each node b to which the local model B responds as a displacement condition [FIG. 16]. Step S21
At 0, the local model B is based on each given displacement condition.
Is obtained, and its distribution state is displayed in a moire pattern, for example [FIG. 17].

[0010]

As described above, the model to be analyzed is decomposed into a local model B and an overall model A,
In the method of giving the displacement result of each node performed on the overall model A as the displacement condition of the local model B, it is necessary for both to share the node on the boundary line of each model. For this reason,
In the above-described conventional technique, as described with respect to steps S206 and S207, when a large number of nodes c are set on the boundary line 53 by the relatively coarse finite element division initially performed on the overall model A, the local model is generated. The node b had to be manually set at the same position on the contour 54 of B. Therefore, there is a problem that not only the working time becomes long, but also if the setting is incorrect, the analysis accuracy is lowered.

Further, when performing finite element division for performing FEM calculation on the whole model A, finite element division must be performed so that the element is forcibly divided at the boundary line 53 with the local model B. Must be (steps S202, S2
03), there is a problem in that each element is distorted and the analysis accuracy decreases.

Moreover, because of the constraint that the elements of each model must be divided by the boundary line 53 in this way, when another part of the overall model A is newly defined as a local model B ', the overall model A There is also a problem that the processing time becomes long because almost all of the processing including the finite element division of (3) has to be executed from the beginning, that is, all the processing after step S202 has to be executed.

Further, even when fine finite element division is performed on the local model in step S208, the contour 5
4 has a wide interval between the nodes b and a narrow interval between the nodes set in the other part (the contour of the opening in this embodiment), the problem that each element is distorted and the analysis accuracy is deteriorated. was there.

An object of the present invention is to solve the above-mentioned problems of the prior art and to enable a stress analysis with high analysis accuracy by making it possible to easily create a mesh with little distortion for the local model B in a short time. Another object of the present invention is to provide a stress analysis method and device.

[0015]

In order to achieve the above-mentioned object, in the present invention, in a stress analysis device for analyzing the stress of the local model B cut out from the overall model A based on the displacement result of the overall model A, Means for dividing the overall model A into relatively coarse finite elements, means for dividing the local model B into relatively fine finite elements, and means for detecting the position of the node b of the local model B formed on the cutout surface, It is characterized in that it has means for calculating the displacement amount of the whole model A at the node b and means for analyzing the stress of the local model B when the node b is displaced by the calculated displacement amount.

Further, in the present invention, in the stress analysis method for analyzing the stress of the local model B cut out from the overall model A based on the displacement result of the overall model A, the step of disposing the overall model A on a known coordinate system. And dividing the overall model A into relatively coarse finite elements on the coordinate system,
A step of dividing the local model B into relatively small finite elements on the coordinate system, a step of detecting coordinates of a node b formed on a cut surface of the local model B, and a coordinate position of the detected node b. The feature is that it includes a step of calculating the displacement amount of the overall model A and a step of analyzing the stress of the local model B when the node b is displaced by the calculated displacement amount.

[0017]

According to the above configuration, the displacement condition on the cutout surface (boundary surface) of the local model B is obtained by calculation based on the displacement amount of the global model A. It is not necessary to match both nodes on the boundary surface. Therefore, the processing procedure can be greatly simplified.

Further, when dividing each model into finite elements, various constraints which have been necessary so far for making the nodes of each model coincide with each other on the boundary surface are not required, so that each model is uniform without distortion. Can be divided into various finite elements.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a stress analysis device 10 according to an embodiment of the present invention.
3 is a block diagram for explaining the function of FIG.

The database 20 stores a large number of shape data of figures to be subjected to stress analysis. The first finite element dividing means 101 divides the entire model A of the analysis target graphic read from the database 20 into relatively coarse finite elements. The displacement amount calculation means 102 is the entire model A.
Then, the FEM calculation is performed on the target object to calculate the displacement amount of each node a. The local model cutout unit 104 cuts out the local model B from the whole model A. Second finite element dividing means 1
Reference numeral 05 divides the local model B into relatively fine finite elements regardless of the division state of the overall model A. The nodal point detection means 106 detects the coordinate position of the nodal point b formed on the cut surface of the local model B. Displacement condition setting means 103
Is the displacement amount of each node b formed on the cutout surface (boundary surface) of the local model B based on the coordinate position and displacement amount of each node a of the overall model A as described below, and the calculation result Is set at each node b. The stress analysis means 107 is
The stress of the local model B when the node b formed on the cut surface of the local model B is displaced by the set displacement amount is analyzed.

The finite element division according to this embodiment will be described below. FIG. 2 is a flow chart for explaining the operation of the stress analysis device 10.

In step S101, the operator operates the operation unit 3
Operate 0 to specify the desired graphic data. The designated graphic data is read from the database 10, developed into geometric data on a known coordinate system, and displayed as the overall model A on the display device 40 [FIG. 3]. Step S10
2, the whole model A is the first finite element dividing means 1
It is divided by 01 into relatively coarse finite elements. At this time, in the present embodiment, the elements must be divided at the boundary with the local model B (step S20 described above).
Since there is no restriction such as (3, 204) and it is possible to freely divide under optimum conditions, it is possible to perform uniform finite element division without distortion [FIG. 4].

In step S103, the overall model A
The displacement amount calculating means 102 calculates the displacement amount of each node a by performing FEM calculation on the target [FIG. 5]. Step S104
Then, when the operator instructs the cutout surface 55 [FIG. 3] of the small area including the opening 51 from the operation unit 30, the local model cutout unit 104 cuts out the small area along the cutout surface 55. The cut out small area is displayed on the display device 40 as the local model B. At this time, the local model B is developed on the same coordinate system as the global model A, and the parts common to the models are managed so as to have the same coordinates.

In step S105, the local model B
Is divided into relatively fine finite elements by the second finite element dividing means 105 [FIG. 6]. Also at this time, in the present embodiment, the node b on the cut surface of the local model B is different from the conventional one.
Since it is not necessary to set (step S207) in advance, if a fine division is instructed, each node b can be set narrow at equal intervals, and uniform finite element division without distortion becomes possible.

In step S106, the coordinates of the node b formed on the cut surface 55 of the local model B are detected by the node detecting means 106. At this time, on the display device 40, by making the display form of the node b formed on the cutout surface 55 of the local model B different from the display form of the other node b formed other than the cutout surface, the operator can The two can be easily identified.

In step S107, the displacement amount of the whole model A at the coordinate position of the nodal point b formed on the cut surface 55 of the local model B is the whole model A surrounding the nodal point b.
Is calculated by the displacement condition setting means 103 based on the position of each node a and the amount of displacement at that position [FIG. 7]. That is, the local model B formed on the cut surface
The amount of displacement of the node b1 of the
It is calculated based on the relative positional relationship between 2, a5, a6 and the node b1 and the amount of displacement of each node a1, a2, a5, a6. Similarly, the displacements of the nodes b2 and b3 of the local model B are determined by the relative positional relationship between the nodes a2, a3, a6 and a7 of the general model A and the nodes b2 and b3, and the respective points a.
It is calculated based on the displacement amounts of 2, a3, a6 and a7, for example, by executing a known interpolation process or the like. The displacement result thus obtained is given to each node b formed on the cut surface 55 of the local model B as a displacement condition [FIG. 8].

In step S108, the FEM calculation of the local model B is performed based on the given displacement condition,
Thereafter, the stress in the vicinity of the opening 51 is obtained by the stress analysis means 107 in the same manner as described above.

In this embodiment, even when another part of the overall model A is newly defined as the local model B ',
Since it is sufficient to execute the processing after step S104 and it is not necessary to divide the whole model A into finite elements again, when performing stress analysis of a plurality of different local models B for the same whole model A The processing time of can be greatly shortened compared to the conventional case.

[0029]

As described above, according to the present invention, the displacement condition on the cut surface (boundary surface) of the local model B is calculated based on the displacement amount of the overall model A. It is not necessary to make the nodes of the model A and the local model B coincident with each other on the boundary surface, and the processing procedure can be greatly simplified.

Further, when dividing the local model B, it is not necessary to take into consideration various constraints which have conventionally been taken into consideration, so that the local model B can be divided into uniform finite elements without distortion, It enables highly accurate stress analysis.

Furthermore, even when another part of the overall model A is newly defined as a local model B ', the overall model A
Does not need to be divided into finite elements again. Therefore,
The processing time when performing stress analysis on a plurality of different local models B for the same entire model A can be significantly shortened compared to the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the function of a stress analysis device that is an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment.

FIG. 3 is a diagram for explaining processing contents of the embodiment.

FIG. 4 is a diagram for explaining processing contents of the embodiment.

FIG. 5 is a diagram for explaining the processing content of the embodiment.

FIG. 6 is a diagram for explaining the processing content of the embodiment.

FIG. 7 is a diagram for explaining the processing contents of the embodiment.

FIG. 8 is a diagram for explaining the processing contents of the embodiment.

FIG. 9 is a flowchart for explaining the processing contents of the conventional technique.

FIG. 10 is a diagram for explaining processing contents of a conventional technique.

FIG. 11 is a diagram for explaining processing contents of a conventional technique.

FIG. 12 is a diagram for explaining processing contents of a conventional technique.

FIG. 13 is a diagram for explaining the processing content of the conventional technique.

FIG. 14 is a diagram for explaining the processing content of the conventional technique.

FIG. 15 is a diagram for explaining the processing content of the conventional technique.

FIG. 16 is a diagram for explaining the processing content of a conventional technique.

FIG. 17 is a diagram for explaining the processing content of the conventional technique.

[Explanation of symbols]

10 ... Stress analysis device, 20 ... Database, 30 ... Operation unit, 40 ... Display device, 101 ... First finite element dividing means, 102 ... Displacement amount calculating means, 103 ... Displacement condition setting means, 104 ... Local model cutting means , 105 ... Second finite element dividing means, 106 ... Node detecting means, 107 ... Stress analyzing means

Claims (6)

[Claims] 1. A stress analysis device for analyzing the stress of a local model B cut out from the whole model A based on the displacement result of the whole model A, a display means for displaying a series of processing progress and providing information to an operator. A means for dividing the overall model A into coarse finite elements, a means for cutting out the local model B from the overall model A, a means for dividing the local model B into fine finite elements, and a local model B formed on the cut surface A unit for detecting the position of the node b, a unit for calculating the displacement amount of the overall model A at the detected node b, and a node b formed on the cut surface of the local model B displaced by the calculated displacement amount. And a means for analyzing the stress of the local model B at that time. 2. The global model A and the local model B
Is developed on a coordinate system whose relative positional relationship is known, The stress analysis device according to claim 1. 3. The global model A and local model B
3. The stress analysis apparatus according to claim 2, wherein is developed on the same coordinate system so that points common to each model have the same coordinates. 4. The means for calculating the displacement amount of the overall model A at the node b is composed of a node b of the local model B formed on the cut surface and a node a of the overall model A located around the node b. The stress analysis device according to claim 1, wherein the displacement amount of the overall model A at the node b is calculated based on the relative positional relationship and the displacement amount of the node a. 5. The display means makes the display form of the node b formed on the cutout surface of the local model B different from the display form of the node b formed on other than the cutout surface. 5. The stress analysis device according to any one of 4 to 4. 6. A stress analysis method for analyzing the stress of a local model B cut out from the whole model A based on the displacement result of the whole model A, a step of arranging the whole model A on a known coordinate system, A step of dividing the whole model A into coarse finite elements on the system, a step of dividing the local model B into fine finite elements on the coordinate system, and detecting the coordinates of the node b formed on the cut surface of the local model B. And the overall model A at the coordinate position of the detected node b.
And a step of analyzing a stress of the local model B when the node b formed on the cut surface of the local model B is displaced by the calculated displacement amount. Stress analysis method.