JPH0618376A - Method for automatic reduction of degree of freedom - Google Patents

Abstract

PURPOSE:To automatically, rapidly and accurately form partial structure data by preliminarily recording inherent mode data and selecting a nodal point to extract the partial structure data on reference to the degree-of-freedom selection data of the nodal point. CONSTITUTION:The inherent values by modes of an object to be analyzed and the mode vector data of the degrees of freedom at respective nodal points are preliminarily recorded while restriction data showing whether the degrees of freedom of the nodal points are restricted are recorded and the degree of freedom of the object to be analyzed is selected on the basis of said data (referred to as the reduction of a degree of freedom). Function checking whether a degree of freedom is accurately selected in this selection process is provided and the accurately selected degree of freedom is registered in a degree-of- freedom selection table. Partial structure data is extracted and recorded from the preliminarily recorded inherent mode on the basis of the selected degree of freedom registered in the degree-of-freedom selection table. By this constitution, partial structure data can be automatically formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for automating the reduction of the degree of freedom used when predicting the vibration characteristics of a structure after assembly.

[0002]

2. Description of the Related Art A conventional vibration characteristic analysis device will be described below by taking a structure vibration simulation device as an example. As shown in FIG. 8, in product design of a structure, particularly a mechanical structure, CAE (Com
(putter Aided Engineering)
Has been attracting attention as a powerful means to reduce development period and cost. Among them, vibration analysis occupies an important position as a reliability evaluation method in product design of mechanical structures. Conventionally, the method of vibration analysis of mechanical structures has been experimental FF.
There are a T (fast Fourier transform) analysis method and a finite element method as a theoretical analysis method. Further, as shown in FIG. 9, as in Japanese Patent Application No. 63-060766, these experimental FFT analysis and theoretical analysis by the finite element method are performed for each component (partial structure) unit of the mechanical structure. There is a partial structure synthesis method that numerically simulates the vibration characteristics of the mechanical structure after joining by inputting each result. In the experimental FFT analysis method, an artificial excitation force is applied to a mechanical structure, the response at that time is measured, those signals are sampled by an A / D converter, and the mini computer or the microcomputer displays the digital signal. Enter the data and use Fast Fourier Transform
ier Transform-FFT), and repeatedly measuring the transfer function between the excitation point and the response point at various points of the mechanical structure, and further performing curve fitting (modal analysis) of the structure. It is a method for obtaining modal parameters such as natural frequency, damping ratio, and vibration mode, and is used as an important means for obtaining the vibration characteristics of an actual structure. On the other hand, the finite element method is considered to be represented by a finite set of finite elements of a mechanical structure, and the relationship between the external force and the deformation of each element is obtained, and this is calculated for the entire mechanical structure between the external force and the displacement. Theoretical analysis using a computer that solves the eigenvalue problem by defining the displacement function of the relation, finds the natural frequency and vibration mode of the structure, and further solves the equation of motion and also finds the response analysis of each element. It is a technique. In the substructure synthesis method, theoretical FFT analysis and theoretical analysis by the finite element method are performed for each component (substructure) unit of the mechanical structure to be analyzed, and the respective results are input to input the mechanical structure after coupling. This is a method of numerically simulating the vibration characteristics of an object, and a specific example thereof will be described with reference to FIG. Figure 1
0 is a diagram illustrating a train design simulation. In the figure, 100 is a train body, 101 is a pedestal, and 1
Reference numeral 02 is a base A, and reference numeral 103 is a base B, each of which is a constituent element of a train. 110-113 is the vehicle body 10
0, each of the vibration characteristics of the gantry 101, the base A102, and the base B103, and 121 indicates the vibration characteristics of the entire system obtained by the partial structure synthesis method 120. In the vibration characteristic example, the horizontal axis represents frequency f and the vertical axis represents vibration response x. Again 20
0 indicates the coordinate system in which the train is placed, where x
A three-dimensional coordinate space in which the axes, the y-axis, and the z-axis are orthogonal to each other is shown. Further, 11 to 14, 21 to 24, and 31 to 34 are measurement points (hereinafter, also referred to as nodes) selected by the vehicle body 100 and the gantry 101. A and B are base 101 and base A10
2. This is the measurement point selected on the table B103. The measurement points having the same numbers or the same symbols are the connection points when the respective constituent elements are combined. Generally, in order to investigate the vibration response of one measurement point, the following six directions may be considered as shown in the coordinate system 200. (1) x-axis direction (x) (2) y-axis direction (y) (3) z-axis direction (z) (4) rotation direction around the x-axis (rx) (5) around the y-axis Rotational direction (ry) (6) Rotational direction (rz) about the z-axis These directions are called degrees of freedom. Therefore, one measurement point has a maximum of six degrees of freedom. Here, for example, if there is a system in which the rotation directions (rx, ry, rz) can be fixed, the degrees of freedom are only x, y, z, and are 3. Further, when the spring only moves up and down, the degree of freedom is 1 (for example, only in the x direction). FIG. 11 is a block diagram showing the structure of a structure vibration simulation apparatus according to an embodiment of the prior art. In the figure, 51a and 51b are partial structure data storages for storing partial structure data of the first and second structures, respectively, and 52a and 52b are partial structure data storages 51a and 51a.
Transfer function calculating means for calculating the transfer function matrix of the structure from the partial structure data from 51b (that is, the partial structure data obtained by actually measuring or analyzing the vibrations of the first and second structures), 53 is a rigid connection It is a partial structure connection definition data storage in which a connection condition indicating soft connection and a constraint relationship matrix indicating a constraint relationship of each degree of freedom, and a coordinate conversion matrix overlapping the constraint relationship matrix are stored. 55 combines the transfer function matrices of the first and second structures obtained by the transfer function calculating means 52a and 52b according to a predetermined combining condition in the partial structure definition data storage 53, and the combined structure It is a coupling means for generating a transfer function matrix. Reference numeral 59 denotes the eigenmodes and modes of the structure after coupling by the transfer function matrix from the transfer function coupling means 55.
The eigenvalue analysis means for analyzing the shape and 60 are eigenvalue analysis result storages for storing the analysis results obtained by the eigenvalue analysis means 59. Reference numeral 61 is a time domain excitation data storage for storing excitation data in the time domain of the structure, and 62 is frequency domain excitation data by performing Fourier analysis on the time domain excitation data in order to perform analysis in the time domain. It is a Fourier analysis means for converting into. Reference numeral 56 is a frequency domain vibration data storage for storing frequency domain vibration data obtained by the Fourier analysis means. Reference numeral 57 represents the frequency of each point of the structure after the combination by the transfer function matrix from the coupling means 55 and the frequency domain excitation data from the Fourier analysis means (frequency domain excitation data from the frequency domain excitation data storage 56). Frequency domain response analysis means for analyzing the response in the domain, 58
Is a frequency domain response result storage for storing the frequency domain response analysis result obtained by the frequency domain response analysis means 57. Reference numeral 63 denotes an inverse Fourier analysis means for converting the frequency response analysis result (contents of the frequency domain response result storage 58) obtained by the frequency domain response analysis means 57 into a time domain response analysis result, and 64 denotes the time domain response analysis result. It is a time domain response result storage for storing. Such a conventional vibration analysis device manually extracts the vibration mode characteristics obtained by the experimental FFT analysis or the finite element method, and creates the partial structure data files 51a and 51b.

FIG. 12 is a diagram showing a list of eigenvalue analysis results. Based on the list of eigenvalue analysis results as shown in FIG. 12, the value of the mode vector of the degree of freedom in the node of interest is selected and the result shown in FIG. I was creating partial structure data such as.
When analyzing with the substructure synthesis method, unlike the finite element method analysis, all nodes and directions are not used as the analysis target,
By selecting and analyzing the node and the direction (degree of freedom) focused on as the analysis target, the efficiency of the calculation memory and the speed can be improved. In this way, selecting the degrees of freedom (nodes and directions) to be analyzed is called reduction of degrees of freedom.
That is, when creating partial structure data, by manually selecting only necessary data from the list of eigenvalue analysis results as shown in FIG. 11 and copying it as partial structure data The amount was decreasing.

[0004]

Since the conventional system is configured as described above, it is necessary to manually select the required degree of freedom one by one, and the time and effort for creating the data are required. This was an advantage of the partial structure synthesis method because it was necessary. The freedom reduction method was not used.

The present invention has been made to solve the above-mentioned problems, and speeds up the degree of freedom reduction processing,
Moreover, it is an object of the present invention to obtain a method capable of automatically creating partial structure synthesis method data.

[0006]

An automated method for reducing the degree of freedom according to the present invention has the following steps. (A) a storage step of storing data regarding the degrees of freedom at each node of the analysis object; (b) a node selection step of selecting the nodes; (c) a degree of freedom of the nodes selected by the node selection step. Degree-of-freedom selection step, (d) an extraction step of extracting and storing data relating to the degree of freedom from the data stored in the storage step based on the degree of freedom selected in the degree-of-freedom selection step.

[0007]

According to the present invention, the partial structure data is extracted and created by referring to the degree-of-freedom selection information created by the node selection step and the degree-of-freedom selection step from the eigenmode information stored in advance in the memory by the storage step. Therefore, there is no error in the partial structure data and the data can be automatically created, and the utilization of the reduced degree of freedom is promoted in the partial structure synthesis method.

[0008]

【Example】

Example 1. An embodiment of the present invention will be described below. FIG. 1 is a diagram showing a flowchart of an automated method of reducing the degree of freedom, and FIG. 2 is a diagram showing an example of a degree of freedom selection table. In FIG. 1, 21 is a storage step of storing the degrees of freedom at each node of the analysis target, 22 is a node selection step of selecting the nodes, 23 is a degree of freedom selection step of selecting the degrees of freedom of the nodes, Reference numeral 24 is an extraction step of extracting the degrees of freedom of the nodes selected in the node selection step in the degrees of freedom selection step from the degrees of freedom stored in the storage step. In FIG. 1, 31 indicates eigenvalues as shown in FIG. 12, and 32 shows mode vector data as shown in FIG. 33
Is a memory for storing these eigenvalues 31 and mode vectors 32. Reference numeral 41 is data for indicating whether the degree of freedom of the node is restricted or not restricted. Reference numeral 42 is a memory for recording constraint information of the degrees of freedom of these nodes. 43 is a step of displaying selectable degrees of freedom. Four
Reference numeral 4 is a freedom degree selection step of selecting the selectable degrees of freedom displayed in the display step. Reference numeral 45 is a check step for checking whether or not the degree of freedom selected in the selection step 44 has been correctly selected based on the rule. Reference numeral 46 is a degree-of-freedom selection table for registering the degree of freedom correctly checked in the checking step 45. Reference numeral 51 denotes a partial structure data storage device which records partial structure data from the memory 33 storing the eigenmode based on the degree of freedom to be selected recorded in the degree of freedom selection table 46.

FIG. 2 is a diagram showing an example of the degree of freedom selection table 46. Node numbers 101 to 200 are selected at the left end, and 1 is entered when the nodes 101 to 200 are selected next, and 0 is not entered when they are not selected. And in the 6 columns next to it, x,
y, z, rx, ry, and rz are entered as six degrees of freedom. When a node is selected, it is possible to determine whether the degree of freedom is selected by checking whether these values are 0 or 1. ing. For example, the node number 101 is selected as a node, indicating that all the degrees of freedom have been selected. Next, since the node number 102 has not been selected as a node, no data is required for the six degrees of freedom, so * is entered in this example. Further, the node number 103 is selected as a node, of which the necessary degrees of freedom are only y, rx, and rz, and other x
It shows that the data of z and ry are not selected as the degrees of freedom. Similarly, this degree-of-freedom selection table shows a list of six degrees of freedom for each node.

Next, the specific examples shown in FIGS. 1 and 2 will be described with reference to the flowcharts and screen layouts below. FIG. 3 is a flowchart showing the shape display of the partial structure model, the selection and display of the degrees of freedom, and the generation of the partial structure data. Hereinafter, the partial structure data will be referred to as S
We will call it DF data. In FIG. 3, reference numeral 1 is a shape display process having the flow shown in FIG. Two
Is a degree-of-freedom process for selecting a degree of freedom for the partial structure selected by the shape display process. 3 is SD
This is SDF data generation processing for generating F data. Figure 4
4 is a diagram showing a flow of the shape display process of FIG. 3, and 4 is a process of displaying a partial structure definition screen as shown in FIG. FIG. 5 is a diagram showing an example of the partial structure definition screen displayed by the shape display processing. In this system, up to two windows can be opened, and the selected partial structure is displayed in the upper frame of the left shape area. The model name and file name are displayed. This allows the user to know which partial structure the displayed partial structure is. In addition, the viewpoint can be changed as the data on the right side. Further, the structure can be confirmed, and the structure of the beam or the structure of the plane shell can be confirmed. FIG. 6 is a diagram showing the flow of the operation of the degree-of-freedom process, and FIG. 7 is a diagram showing an example of a screen when the degree of freedom is selected in the operation.

In the selection of the degree of freedom, there are the following two kinds of selection methods in order to create the shape of the whole structure (with a reduced degree of freedom). (A) The degree of freedom is selected as the beam element. (B) Select the degree of freedom as a plane shell element.

The operation method will be described below. (A) Select the degree of freedom as a beam element (1) Click "beam" in the degree of freedom selection process on the partial structure definition screen of FIG. 5 to invert it. (2) Select the node of the end point 1 by picking. The pick ID is set on a straight line connecting two points. In the system, a node near the pick position on the straight line is selected and a circle (○) is drawn at that position. Further, the degree-of-freedom screen of FIG. 7 is opened, in which: -node number-degree of freedom (direction) that can be selected in (3) below ("X", "Y", "Z", ... are reversed) Is displayed. (3) The degree of freedom of the node of the end point 1 is selected using the degree of freedom screen. (I) When selecting all of the degrees of freedom highlighted in (2) a) Click “All degrees of freedom”. b) Click "Finish" to close the degrees of freedom screen. (Ii) When selecting a part of the degrees of freedom highlighted in (2) above a) Click "Partial degrees of freedom". b) Click the item to reverse the degree of freedom that is not selected. c) Click “Finish” to close the degrees of freedom screen. (Iii) To constrain (do not select) all the degrees of freedom highlighted in (2) a) Click "Constrain". b) Click "Finish" to close the degrees of freedom. (4) The node of the end point 2 and its degree of freedom are selected by repeating the operations of (2) and (3). (5) Clicking "Execute" registers the degree of freedom selection, and clicking "Cancel" disables the processes of (1) to (4).

(B1) Selection of degree of freedom as a plane shell element (rectangular element) (1) Click "plane shell" of the degree of freedom selection processing of the partial structure definition screen of FIG. 5 to invert it. (2) Select the node of the end point 1 by picking. The pick ID is set on a straight line connecting two points. In the system, a node near the pick position on the straight line is selected and a circle (○) is drawn at that position. Further, the degree-of-freedom screen of FIG. 7 is opened, in which: -node number-degree of freedom (direction) that can be selected in (3) below ("X", "Y", "Z", ... are reversed) Is displayed. (3) The degree of freedom of the node of the end point 1 is selected using the degree of freedom screen. (I) When selecting all of the degrees of freedom highlighted in (2) above a) Click "All degrees of freedom". b) Click "Finish" to close the degrees of freedom screen. (Ii) When selecting a part of the degrees of freedom highlighted in (2) above a) Click "Partial degrees of freedom". b) Click the item to reverse the degree of freedom that is not selected. c) Click “Finish” to close the degrees of freedom screen. (Iii) To constrain (do not select) all the degrees of freedom highlighted in (2) above a) Click "Constrain". b) Click "Finish" to close the degrees of freedom. (4) The node of the end point 2 and its degree of freedom are selected by repeating the operations of (2) and (3). (5) The node of the end point 3 and its degree of freedom are selected by repeating the operations of (2) and (3). (6) The node of the end point 4 and its degree of freedom are selected by repeating the operations of (2) and (3). (7) The node of the end point 1 is reselected by the operation of (2). (8) Clicking "Execute" registers the degree of freedom selection, and clicking "Cancel" disables the processing of (1) to (7).

(B2) Degree of freedom selection as a plane shell element (triangular element) (1) Click "plane shell" of the degree of freedom selection process of the partial structure definition screen of FIG. 5 to invert it. (2) Select the node of the end point 1 by picking. The pick ID is set on a straight line connecting two points. In the system, a node near the pick position on the straight line is selected and a circle (○) is drawn at that position. Further, the degree-of-freedom screen of FIG. 7 is opened, in which: -node number-degree of freedom (direction) that can be selected in (3) below ("X", "Y", "Z", ... are reversed) Is displayed. (3) The degree of freedom of the node of the end point 1 is selected using the degree of freedom screen. (I) When selecting all of the degrees of freedom highlighted in (2) above a) Click "All degrees of freedom". b) Click "Finish" to close the degrees of freedom screen. (Ii) When selecting a part of the degrees of freedom highlighted in (2) above a) Click "Partial degrees of freedom". b) Click on the item to reverse the unselected degrees of freedom. c) Click “Finish” to close the degrees of freedom screen. (Iii) To constrain (do not select) all the degrees of freedom highlighted in (2) above a) Click "Constrain". b) Click "Finish" to close the degrees of freedom. (4) The node of the end point 2 and its degree of freedom are selected by repeating the operations of (2) and (3). (5) The node of the end point 3 and its degree of freedom are selected by repeating the operations of (2) and (3). (6) The node of the end point 1 is reselected by the operation of (2). (7) Click "Execute" to register the degree of freedom selection, and click "Cancel" to invalidate the processes (1) to (6). The degree-of-freedom display processing is performed as
It is used to know what was selected in (1). Also,
The degree-of-freedom initialization process is a case of initializing the degree-of-freedom selection process. Through the above-described specific operation, the degree-of-freedom selection table as shown in FIG. 2 is created.

As described above, this embodiment is characterized by the following points. (1) 1 / freedom information of constraint / non-constraint of all nodes
0 is stored in the memory. (2) Degree of freedom Information about whether or not the selected node is stored in the memory in units of nodes. (3) Check whether the selected degree of freedom out of the six degrees of freedom of the selected node is unconstrained in (1). (4) If the above (3) is OK, the selection / non-selection information is stored in the memory in the degree-of-freedom list for each node. (5) Partial structure composite data is created from both the information in (2) and (4) above and the mode information stored in the memory in advance.

Example 2. In the above-mentioned embodiment, the case where the node selection step 22 precedes the degree-of-freedom selection step 23 is shown, but the order of the node-selection step 22 and the degree-of-freedom selection step 23 may be exchanged. Alternatively, the degree of freedom may be selected for each node by executing the nodes alternately.

Embodiment 3. In the first embodiment described above, the case of selecting the degree of freedom has been described, but the case of selecting eigenmode information such as eigenvalue mode mass and mode combination may be used. In that case, it is necessary to provide the necessary selection conditions in the selection process in order to extract these pieces of information.

[0018]

As described above, according to the present invention, eigenmode information and degree-of-freedom selection information are stored in a memory,
Since partial structure data is created, accurate data can be created easily.

[Brief description of drawings]

FIG. 1 is a diagram showing a flowchart of an automated method of reducing the degree of freedom according to the present invention.

FIG. 2 is a diagram showing an example of a degree-of-freedom selection table used in an automated method of reducing the degree of freedom according to the present invention.

FIG. 3 is a diagram showing a flow of a partial structure definition process in the present invention.

FIG. 4 is a diagram showing a flow of shape display processing in the present invention.

FIG. 5 is a diagram showing an example of a partial structure definition screen according to the present invention.

FIG. 6 is a diagram showing a flow of a degree-of-freedom selection process according to the present invention.

FIG. 7 is a diagram showing an example of a degree-of-freedom selection screen according to the present invention.

FIG. 8 is a diagram showing a flow of a conventional CAE.

FIG. 9 is a diagram showing a schematic diagram by a conventional partial structure synthesis method.

FIG. 10 is a diagram for explaining an example of a conventional partial structure synthesis method.

FIG. 11 is a diagram showing components of a conventional partial structure synthesis method.

FIG. 12 is a diagram showing an example of an eigenvalue eigenmode.

FIG. 13 is a diagram showing an example of partial structure data.

[Explanation of symbols]

 21 storage process 22 node selection process 23 degree of freedom selection process 24 extraction process

Claims (1)

[Claims] 1. An automated method for reducing the degree of freedom having the following elements: (a) a storage step of storing data relating to the degrees of freedom at each node of an analysis object; (b) a node selection step of selecting the node; c) a degree-of-freedom selection step of selecting the degree of freedom of the node selected in the above-mentioned node-selection step, and An extraction step of extracting and storing data regarding the degree of freedom.