JPH0916559A - Method for analyzing finite element and device therefor - Google Patents

Abstract

PURPOSE: To obtain an analysis result with high accuracy by generating a shape model, regardless of kinds of imparted shape data, performing a batch processing for the process from the input of shape data up to the output of the analysis result and performing the redivision of a mesh without any manual aid when the paint-out of the element in the mesh becomes excessive during the execution of the analysis. CONSTITUTION: The shape data imparted by having each form from a CAD data file 10, a measured data file 11 and a mesh data file 12 is once stored in a shape data file 3, the data is read in an arithmetic processing part 1, the data is transformed into point group data having attributes of coordinate values and the data is stored in a point group data file 2. This point group data is read in the arithmetic processing part 1, each point is approximated by a free curved surface or a free curve, a shape model is generated, a mesh division is performed for the generated shape model and a finite element analysis is executed by using the obtained mesh.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finite element analysis method and a finite element analysis apparatus used for various analyses, and more specifically, a finite element used for analysis of a phenomenon involving large deformation of an object to be analyzed. The present invention relates to an analysis method and a finite element analysis device.

[0002]

2. Description of the Related Art Finite element method
nt Method) is a powerful method that enables not only structural analysis and vibration analysis of various structures but also various phenomena that occur under complicated conditions such as heat conduction analysis and fluid analysis, and is used in many industries. Widely used in the field.

In the analysis by the finite element method, an object to be analyzed is divided into meshes, and changes in physical quantities such as strain and stress generated in each element in the mesh are analyzed under predetermined conditions such as restraint and external force. The calculation procedure is repeated. This calculation is complicated including matrix calculation that requires a large amount of calculation, but in recent years, various programs have been developed according to the purpose of analysis, and by using these, it is relatively easy to use. Finite element analysis can be performed.

In carrying out the finite element analysis,
It is necessary to divide the analysis target into meshes, but in recent years, various methods for automating the mesh division such as Delaunay method have been established, and a shape model corresponding to the analysis target is given. At this time, a finite element analysis device having a mesh generation means for automatically mesh-dividing the shape model into elements having a predetermined shape such as a triangle or a tetrahedron has been put into practical use.

Further, in recent years, when shape data of an object to be analyzed is given, means for generating a shape model for mesh division using this shape data has been put into practical use, and particularly, CAD (Computer). Aide
The finite element analysis device provided with the shape model generation means for the shape data by d Design) and the mesh generation means described above can easily perform the structural analysis or vibration analysis of various structures by using together with CAD. Is being watched as.

[0006]

However, the shape data of the structure to be subjected to the finite element analysis is the shape data obtained by the shape measurement of the analysis object using the three-dimensional measuring device, and the mesh-divided state. It may be given in a form different from the shape data obtained as the output of CAD, such as the shape data given by, and in order to handle these shape data together, a model generation that generates a shape model from each shape data It is necessary to prepare a means for each, and there has been a problem that the configuration of the analysis system is complicated.

On the other hand, one of the main applications of finite element analysis is the analysis of deformation and stress in a structure during plastic working. In this case, it was generated using a shape model at the stage before working. There is a problem that the mesh is greatly crushed as the analysis progresses, and elements with extremely distorted shapes occur in the middle of the analysis, which not only significantly reduces the accuracy of subsequent analysis but also hinders the continuation of the analysis. I was even afraid.

In order to solve such a problem, conventionally, an analyst generally monitors the collapse of each element that occurs during analysis, suspends the analysis when a large collapse occurs, and at that time The analysis is restarted after the mesh is subdivided according to the shape. However, in this case,
Since the analyst decides whether to interrupt the analysis or re-divide the mesh, there is the inconvenience that the analysis results will differ depending on the quality of this decision, and the manual re-division of the mesh requires a large amount of time for the analyst. There is a problem of compelling labor.

The present invention has been made in view of such circumstances, and a shape model is generated irrespective of the type of shape data given, and the subsequent mesh division and analysis calculation are executed to input the shape data. It is possible to batch process the process up to the output of analysis results. Furthermore, when the elements in the mesh are excessively crushed during the analysis, the mesh is re-divided without relying on human hands, resulting in high accuracy. It is an object of the present invention to provide a finite element analysis method and a finite element analysis device that can obtain the analysis result of 1.

[0010]

A finite element analysis method according to the present invention generates a shape model of an object to be analyzed based on given shape data, and then obtains the generated shape model by mesh division. In the finite element analysis method for analyzing the state change of the analysis object accompanied by the deformation of each element in the mesh, the shape data is converted into point cloud data represented as coordinate values, and the point cloud data is converted into a free-form surface. Alternatively, the shape model is generated by approximating with a free curve.

Further, the finite element analysis apparatus according to the present invention generates a shape model of an object to be analyzed on the basis of given shape data, and then divides the generated shape model into meshes to obtain each mesh. In the finite element analysis device for analyzing the state change of the analysis target with the deformation of the element,
Shape data conversion means for converting the shape data into point cloud data represented as coordinate values, and model generation means for approximating the obtained point cloud data with a free curved surface or a free curve to generate the shape model. It is characterized by doing.

In addition, comparing means for comparing the collapse generated in each element in the mesh with the deformation with a predetermined allowable value, and when the result of this comparison is a collapse exceeding the allowable value, And a means for feeding back the shape data of the mesh including the collapse to the shape data converting means.

[0013]

In the present invention, it includes CAD data given as a combination of curved surface data, measurement data of an analysis object given as a set of coordinate values at respective measurement positions, and element configuration and coordinate values of vertices. When various shape data showing the shape of the analysis object such as given mesh data is given, these are once converted into point cloud data including a large number of points expressed as three-dimensional or two-dimensional coordinate values. The point group data is approximated by a free-form surface or free-form curve to generate a shape model, and the shape model is divided into meshes for analysis.

For example, the conversion from CAD data to point cloud data is performed by taking a plurality of points on a large number of planes defined by the CAD data and specifying the coordinate values of these points.
In addition, for conversion from measurement data and mesh data to point cloud data, the coordinate values of the measurement points or the vertices of the elements are used as they are, and one or more points are taken on the curved surface including these points, and these coordinate values are used. And specify.

Further, in the present invention, the deformation occurring in each element during the execution of the analysis is monitored by using, for example, the aspect ratio, the twist angle, the apex angle, etc. as an index, and the collapse of each element due to the deformation exceeds the allowable value. When this occurs, the mesh data including the element in which this collapse has occurred is fed back to the shape data conversion means,
After converting to point cloud data, a model generation unit regenerates a shape model that matches the current situation, and the analysis is continued using a new mesh obtained by dividing the shape model into meshes.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing the configuration of a finite element analysis apparatus according to the present invention. As shown in the figure, the finite element analysis apparatus A according to the present invention includes a calculation processing unit 1, a point cloud data file 2 as a data storage unit during calculation, a shape data file 3 as a storage unit for input data, and analysis conditions. And a data file 4.

On the input side of the finite element analyzer A, a CAD
It is possible to connect a CAD data file 10 provided in the apparatus, a measurement data file 11 provided in the measuring apparatus for shape measurement, and a mesh data file 12 provided in the analysis apparatus, and The shape data shown is given from any of the files 10, 11 and 12 and is temporarily stored in the shape data file 3.

An input unit 13 such as a keyboard is connected to the input side of the finite element analysis apparatus A. This input section 13
Is provided for performing various input operations such as an operation for instructing execution of analysis, an operation for specifying an input file, and an operation for inputting various data necessary for setting analysis conditions used for analysis. When performing deformation analysis and stress analysis related to plastic working, the data necessary for setting the analysis conditions include, for example, the restraint position and restraint condition of the analysis target, and the action mode of the load, the action position and action direction, and the material condition. These data are input by the operation of the input unit 13 and stored in the analysis condition data file 4.

The arithmetic processing unit 1 includes a shape data conversion means 1a.
(See FIGS. 2 and 3), and model generation means 1b (see FIG. 4). The shape data conversion means 1a reads the shape data stored in the shape data file 3 and converts the shape data into point cloud data having an attribute of coordinate value according to a predetermined rule. The shape data stored in the shape data file 3 is given from the CAD data file 10, the measurement data file 11, or the mesh data file 12 as described above, and each shape data is converted into point cloud data. Is performed as follows, for example.

FIG. 2 is an explanatory diagram of a method of converting CAD data into point cloud data. As shown in the upper half of the figure, the CAD data regards the surface of the object to be analyzed as a series of planes such as planes and curved surfaces, and is given as a set of data showing the respective planes. The shape data conversion unit 1a sets a sufficient number of points for each of the surface segments included in the CAD data to specify their position and shape, calculates the coordinate value of each point, and obtains the point group data. Configure. As a result, as shown in the lower half of the figure, point group data including a sufficient number of points to represent the shape of the analysis object is determined with the attribute of the coordinate value.

As described above, the set points on the plane data and the curved surface data only have to exist so as to specify the position and shape of each surface portion, but more points may be set. That is, in order to specify the position and shape of the surface segment represented by the plane data, it is sufficient to set the vertices that define the surface segment, but as shown by the white dots in FIG. Also, intermediate points may be set at appropriate intervals on a plane passing through the respective vertices, and in the case of the surface segment represented by the curved surface data, as shown by the white dots in FIG. One or a plurality of intermediate points may be set at appropriate intervals on the free-form surface including the vertices that define the.

FIG. 3 is an explanatory diagram of a method of converting mesh data into point cloud data. Mesh data file 12
As shown in the figure, the mesh data given from contains the configuration of each element and the coordinate values of the vertices as data for specifying the position and size of many elements obtained by dividing the analysis target in a predetermined procedure. Given. Shape data conversion means 1a
Uses the coordinates of the vertices of each element as they are, and further adds the coordinates of the points on the sides that demarcate each element, for example, the coordinates of the midpoint of the line segment connecting the vertices to form point cloud data. . As a result, as shown in the lower half of the figure, point group data including a sufficient number of points to represent the shape of the analysis object is determined with the attribute of the coordinate value.

A plurality of points are set on the sides of each element,
These may be added to form point cloud data, and further,
Point cloud data may be configured by adding determinable points (center of gravity, center, etc.) inside each element.

On the other hand, the shape data given from the measurement data file 11 is the coordinate values obtained as the measurement results by various measuring devices at many measurement points set appropriately on the surface of the object to be analyzed, and the shape data has already been obtained. It has a form as group data. The shape data conversion means 1a may output this data without processing it, but similarly to the case of the mesh data, one or a plurality of points are set between the measurement points and within the curved surface including the measurement points. It is also possible to construct the point cloud data by adding the coordinates of these points.

The point cloud data generated as described above is temporarily stored in the point cloud data file 2. The model generation means 1b reads the data stored in the point cloud data file 2 and approximates the coordinates of each point included in this data by a free-form surface to generate a shape model B ′ of the analysis object.

FIG. 4 is a diagram for explaining the operation of the model generating means 1b. As shown in the upper half of the figure, the input to the model generating means 1b is point cloud data consisting of a large number of points set on the surface of the analysis object, and the point cloud data is the model generating means 1b. By the operation of, the shape model B ′ is obtained by approximating each point included in the data by the free-form surface. Various methods have been conventionally known for approximating a large number of randomly set points by a free-form surface, and any method may be used to generate the shape model B ′. Note that the analysis target is 2
In the case of the dimension, the model generating means 1b approximates the free curve to generate a two-dimensional shape model.

The shape model B'generated in this way is
A mesh is automatically generated by dividing into a large number of elements according to a known automatic mesh division method such as Delaunay method. At this time, in consideration of the radii of curvature in each part of the surface of the shape model B ′, the mesh of the part having a small radius of curvature can be subdivided in advance. The mesh thus generated is used in the finite element analysis performed under the analysis conditions read from the analysis condition data file 4.

FIG. 5 is a flow chart showing the flow of processing by the finite element analysis apparatus according to the present invention. The operation according to this flowchart is started, for example, in response to a predetermined operation on the input unit 13, and first, the variable N representing the number of repetitions is set to 0 (step 1), and the shape data conversion unit
1a performs an operation of reading the shape data stored in the shape data file 3 and converting it into point cloud data (step 2), and the point cloud data obtained by this is stored in the point cloud data file 2 ( Step 3).

The data stored in the point cloud data file 2 is read by the model generating means 1b, and the shape model B'of the analysis object is generated by the above-described operation (step 4), and the obtained shape model B '. Is automatically divided into a large number of elements, and mesh data for execution of analysis is generated (step 5). The mesh thus generated is given to the analyzing means (step 6) and used for executing the finite element analysis. In this analysis, 1 is set in the variable N that represents the number of repetitions.
Is performed (step 7), the variable N is compared with a preset final number Nmax (step 8), and N ≧
If it is Nmax, the analysis operation is terminated.

On the other hand, if N does not reach Nmax, the collapse of each element in the mesh is examined (step 9). If the collapse of all elements does not exceed the preset allowable value, step 6 If the collapse of any element exceeds the allowable value, the current mesh data is stored in the shape data file 3 (step
10), by feeding back to the shape data conversion means 1a, the operation from step 2, that is, conversion to point cloud data, generation of a shape model, generation of a mesh is sequentially performed, and a new mesh corresponding to the deformed shape. To restart the analysis operation.

During the above operation, the determination in step 9 is made using, for example, one or more of the aspect ratio, the twist angle, and the apex angle of each element in the mesh as an index. This is for sequentially monitoring the crushing that occurs in each element as the finite element analysis is performed, and for determining whether or not subdivision is necessary. As a result of this determination, it is determined that subdivision is necessary. In this case, the mesh data including the elements that have collapsed beyond the allowable value is fed back as shape data and stored in the shape data file 3.

The stored shape data is converted into point cloud data by the shape data conversion means 1a, the shape model B'is regenerated by the model generation means 1b, and the shape model B'is mesh-divided and analyzed. Used to continue. The shape data re-stored in the shape data file 3 is the mesh data corresponding to the shape of the mesh used for executing the analysis, and the conversion to the point cloud data is the mesh data given from the mesh data file 12. It is done exactly as in the case of conversion.

[0033]

As described above in detail, in the finite element analysis method and the finite element analysis apparatus according to the present invention, the shape data representing the shape of the analysis object is once converted into the point cloud data having the attribute of the coordinate value, Since a shape model is generated by approximating this point cloud data by a free-form surface or free-form curve, CA
For various shape data such as D data, measurement data, and mesh data, a shape model can be generated by common processing, and by performing analysis using a mesh obtained by dividing the shape model into meshes, The process from the input of the shape data to the output of the analysis result can be collectively processed regardless of the type of the shape data.

Further, the crushing that occurs in each element in the mesh during the execution of the analysis is checked, and when this exceeds an allowable value, the mesh data at that time is fed back to be reconverted into the point cloud data, and the model generating means is used. Since a shape model that matches the mesh deformation state at that time is regenerated, finite element analysis involving large element deformation can be executed continuously without the occurrence of unanalyzable situations and without human intervention. The present invention has excellent effects such as being able to obtain a highly accurate analysis result.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a finite element analysis apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a conversion method from CAD data to point cloud data.

FIG. 3 is an explanatory diagram of a conversion method from mesh data to point cloud data.

FIG. 4 is an explanatory diagram of an operation of model generation means.

FIG. 5 is a flowchart showing a flow of processing in the finite element analysis device according to the present invention.

[Explanation of symbols]

 1 Calculation processing unit 1a Shape data conversion means 1b Model generation means 2 Point cloud data file 3 Shape data file 4 Analysis condition data file

Claims (3)

[Claims] 1. A shape model of an analysis object is generated based on given shape data, and the analysis object is accompanied by deformation of each element in a mesh obtained by dividing the generated shape model into meshes. In the finite element analysis for analyzing the state change of, the shape data is converted into point cloud data represented as coordinate values, and the point cloud data is approximated by a free curved surface or a free curve to generate the shape model. Characteristic finite element analysis method. 2. An object to be analyzed accompanied by deformation of each element in a mesh obtained by generating a shape model of an object to be analyzed based on given shape data and then dividing the generated shape model into meshes. In the finite element analysis device for analyzing the state change of, the shape data conversion means for converting the shape data into point cloud data represented as coordinate values, and the obtained point cloud data are approximated by a free curved surface or a free curve. A finite element analysis device comprising: a model generation unit that generates the shape model. 3. A comparison means for comparing the crushing generated in each element in the mesh due to the deformation with a predetermined allowable value, and the shape of the mesh when the crushing exceeding the allowable value occurs as a result of this comparison. The finite element analysis device according to claim 2, further comprising means for feeding back data to the shape data conversion means.