JP2008217269A - Analysis method, analysis apparatus and analysis program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an analysis method, analysis apparatus and analysis program which can perform thermal analysis in consideration of an error by element division even when an unknown quantity is included. <P>SOLUTION: An element dividing part 14 of an orthogonal lattice design method creates an approximate model by dividing an analysis object input into a finite number of elements based on an orthogonal grid method. A computing and setting part 15 of a corrected heat transfer coefficient sets a heat transfer coefficient on a surface of the approximation model. When the approximation model or initial temperature or thermal source condition of its circumference is set by an analysis condition input part 13, a temperature change calculation part 16 of an analysis area computes the temperature change of the approximation model when a predetermined time has passed based on the approximation model, the heat transfer coefficient, the initial temperature and the thermal source conditions. The computing and setting part 15 of a corrected heat transfer coefficient corrects the heat transfer coefficient based on a ratio of a surface area of the analysis object before element breakdown with a surface area of the corresponding approximation model. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an analysis method, an analysis apparatus, and an analysis program for performing thermal analysis using a computer.

  In designing the heat of an electronic device, a model based on CAD (Computer Aided Design) data or the like is used to analyze the flow of heat from the heat source or the temperature change at a specified location of the model using various analysis methods.

One of analysis methods used for thermal analysis is an analysis method based on an orthogonal lattice method. When the heat transfer coefficient h ₀ is set as the analysis condition on the curved surface of the analysis object, the curved surface portion of the model is approximated by a stepped surface composed of a plurality of planes in the orthogonal lattice method.

  FIG. 3 is a diagram showing a cross-sectional view of a curved surface portion in the three-dimensional CAD data. When a curved surface portion having such a cross section is approximated by an orthogonal lattice method, a stepped cross section as shown in the cross sectional view of FIG. 4 is obtained.

By such an approximation, the area of the portion where the heat transfer coefficient is set changes before and after the approximation, so the amount of heat that moves through the interface also changes. The surface area of the actual curved setting the heat transfer coefficient (surface area before approximation) S _0, the surface area of the stepped surface approximating a curved surface for setting the heat transfer coefficient in the orthogonal grid method and S _C. Assuming that the desired amount of heat to pass through the curved surface interface is Q ₀ , the amount of heat moving through the curved surface interface after approximation by the orthogonal lattice method is Q _C , and the temperature difference between the curved surface temperature and the ambient temperature is ΔT, After the approximation, an error in the amount of heat (Q _C −Q ₀ ) = h ₀ × ΔT × (S _C −S ₀ ) occurs.

  Patent Document 1 discloses a technique for correcting an approximation error by an orthogonal lattice method when pressure is applied to an analysis object as an analysis condition in a structural analysis by the orthogonal lattice method.

  Although the load is given as an area fraction of the pressure field, the surface area of the actual surface that loads the pressure (surface area before approximation) differs from the surface area of the stepped surface approximated by the orthogonal grid method. The minute value is different from the actual value. In the technique described in Patent Document 1, attention is paid to the relationship that the load is an area fraction of the pressure field in order to give an accurate load, and the pressure applied according to the area error in order to absorb the area error. Is corrected.

  Assuming that the pressure applied to the analysis object is Fp, the actual area where pressure is applied to the analysis object is Cs, and the surface area of the stepped surface approximated by the orthogonal grid method is Vs, the load in the orthogonal grid model of the analysis object The pressure to be expressed is expressed as Vp = Fp × Cs / Vs.

  As a result, the pressure set in the orthogonal lattice model is set accurately by the ratio of the actual surface area of the surface to which pressure is applied and the surface area of the staircase surface obtained by approximating the surface to which pressure is applied by the orthogonal lattice method. The pressure was corrected to be

JP 2002-288239 A

  As described above, in the case of structural analysis, pressure is applied to the object to be analyzed, but the physical quantity of load is represented by the product of pressure and area given as an initial condition. All the constituent variables (pressure and area) are known quantities.

  In contrast, in the case of thermal analysis, the amount of heat that moves through the interface is represented by the product of the heat transfer coefficient, temperature difference (difference between surface temperature and ambient temperature), and surface area. It is a variable and an unknown quantity that are sequentially obtained in the calculation process by the method. Therefore, the unknown quantity is included in the formula representing the physical quantity of heat.

  As described above, the invention described in Patent Document 1 is only a correction when all variables are known, and cannot cope with any case where an unknown amount is included in the variables.

  An object of the present invention is to provide an analysis method, an analysis apparatus, and an analysis program capable of performing thermal analysis in consideration of an error due to element division even when an unknown amount is included.

The present invention divides an analysis object into a finite number of elements based on an orthogonal lattice method, and creates an approximate model; and
A heat transfer coefficient setting step of setting a heat transfer coefficient on the surface of the approximate model;
An analysis condition setting step for setting the approximate model or the surrounding initial temperature, heat source conditions,
A temperature change calculating step of calculating a temperature change when a predetermined time elapses of the approximate model based on the approximate model, the heat transfer coefficient, the initial temperature, and the heat source condition;
In the heat transfer coefficient setting step, the heat transfer coefficient is corrected based on a ratio between a surface area of the analysis object before element division and a surface area of the approximate model corresponding to the surface area. is there.

Further, according to the present invention, in the heat transfer step, the heat transfer coefficient of the surface of the analysis object is h ₀ , the surface area of the setting surface for setting the heat transfer coefficient is S ₀ , and the surface area of the surface corresponding to the setting surface of the approximate model is when the S _C, the heat transfer coefficient _{h C} to set the approximate _model, and calculating by the equation _{h C = h 0 × S 0} / S C.

The present invention also includes an element dividing means for dividing an analysis object into a finite number of elements based on an orthogonal lattice method and creating an approximate model;
Heat transfer coefficient setting means for setting a heat transfer coefficient on the surface of the approximate model;
Analysis condition setting means for setting the approximate model or the surrounding initial temperature, heat source conditions,
A temperature change calculating means for calculating a temperature change when a predetermined time elapses of the approximate model based on the approximate model, the heat transfer coefficient, the initial temperature, and the heat source condition;
The heat transfer coefficient setting means corrects a heat transfer coefficient based on a ratio between a surface area of the analysis object before element division and a surface area of the approximate model corresponding to the surface area. is there.

  Further, the present invention is a program for causing a computer to function as the above-described analysis device.

  According to the present invention, in the element dividing step, the analysis object is divided into a finite number of elements based on the orthogonal lattice method, an approximate model is created, and the heat transfer coefficient setting step is performed on the surface of the approximate model. Set the heat transfer coefficient.

  In the analysis condition setting step, the approximate temperature of the approximate model or its surroundings and the heat source condition are set, and in the temperature change calculation step, the approximation is performed based on the approximate model, the heat transfer coefficient, the initial temperature, and the heat source condition. The temperature change when a predetermined time of the model has elapsed is calculated.

  In the heat transfer coefficient setting step, the heat transfer coefficient is corrected based on the ratio between the surface area of the analysis object before element division and the surface area of the approximate model corresponding thereto.

  In this way, by correcting the heat transfer coefficient, which is a known amount, according to the surface area ratio before and after approximation, even in thermal analysis that includes unknown amounts, errors due to element division are corrected and analysis accuracy is taught. be able to.

According to the invention, in the heat transfer coefficient setting step, the heat transfer coefficient of the surface of the analysis object is h ₀ , the surface area of the setting surface for setting the heat transfer coefficient is S ₀ , and corresponds to the setting surface of the approximate model. when the surface area of the surface was _{S C,} the heat transfer coefficient _{h C} to set the approximate model _is calculated by the equation _{h C = h 0 × S 0} / S C.

  By setting the product of the heat transfer coefficient and the surface area to the same value before and after the approximation, high-accuracy correction can be easily performed.

  According to the invention, the element dividing means divides the object to be analyzed into a finite number of elements based on the orthogonal lattice method to create an approximate model, and the heat transfer coefficient setting means has a surface of the approximate model. Set the heat transfer coefficient to.

  When the analysis condition setting unit sets the approximate model or the initial temperature and heat source conditions around the approximate model, the temperature change calculation unit is configured to perform the approximation based on the approximate model, the heat transfer coefficient, the initial temperature, and the heat source condition. The temperature change when a predetermined time of the model has elapsed is calculated.

  The heat transfer coefficient setting unit corrects the heat transfer coefficient based on a ratio between a surface area of the analysis object before element division and a surface area of the approximate model corresponding to the surface area.

  In this way, by correcting the heat transfer coefficient, which is a known amount, according to the surface area ratio before and after approximation, even in thermal analysis that includes unknown amounts, errors due to element division are corrected and analysis accuracy is taught. be able to.

  Further, according to the present invention, it is possible to provide a program for causing a computer to function as the analysis device.

  FIG. 1 is a block diagram showing a functional configuration of an analysis apparatus 1 according to an embodiment of the present invention.

  The analysis apparatus 1 includes a control unit 10, a shape information input unit 11, a material information input unit 12, an analysis condition input unit 13, an element division unit 14 using an orthogonal lattice method, and a correction heat transfer coefficient calculation and setting unit. 15, an analysis region temperature change calculation unit 16, an output unit 17, a CAD information database 21, a material information database 22, and an output result database 23.

  The control part 10 controls the operation | movement of each site | part of the thermal-analysis apparatus 1, and performs data delivery and data processing between these.

  The shape information input unit 11 inputs shape information that is a parameter of a three-dimensional model conforming to three-dimensional CAD data, such as the outer shape, arrangement, and dimensions of an analysis object (hereinafter referred to as “model”). The material information input unit 12 inputs material information such as thermal conductivity, specific heat, density, and emissivity of each constituent material of the model. The analysis condition input unit 13 is analysis condition setting means for inputting and setting boundary conditions such as initial conditions such as initial temperature, heat generation setting and environmental temperature, heat insulation conditions, and heat dissipation conditions.

  The element dividing unit 14 based on the orthogonal lattice method is an element dividing unit that divides the model into a finite number of elements based on the orthogonal lattice method. The correction heat transfer coefficient calculation and setting unit 15 is a heat transfer coefficient setting unit that corrects and sets the heat transfer coefficient of the model input by the shape information input unit 11.

  The heat transfer coefficient input in the analysis condition input unit 13 (hereinafter referred to as “coefficient before correction”), the surface area of the analysis target surface in the model before element division (hereinafter referred to as “surface area before approximation”), and element division. The surface area of the analysis target surface in the later model (hereinafter referred to as “approximate surface area”) and the heat transfer coefficient corrected using the following (hereinafter referred to as “corrected coefficient”) are calculated and Set to a stepped surface.

  The temperature change calculation unit 16 in the analysis region is a temperature change calculation unit that calculates a temperature change when a predetermined time elapses for each element after the element division by a finite element method, a finite difference method, a finite volume method, or the like. .

  Here, the predetermined time is set when performing non-stationary analysis. The unsteady analysis is an analysis performed when the temperature change is analyzed over time and the temperature distribution after a desired time is desired to be known or when the temperature change until the desired time is desired to be observed. Therefore, the predetermined time may be appropriately set according to the analysis result desired by the user. Note that the number of Courants is a guideline for the time step Δt of unsteady analysis, and if Δt becomes small, the analysis cost for a long time interval greatly increases.

  The output unit 17 outputs the corrected heat transfer coefficient and the corrected coefficient calculated by the setting unit 15 and the temperature change of each element calculated by the temperature change calculation unit 16 in the analysis region.

  The output of the temperature change can be handled by existing technology used in this field. For example, when 3D CAD data is used as a model, the 3D approximate model is converted into a contour map of the absolute temperature (ambient temperature given as initial condition + temperature change) on a post of general-purpose analysis software (application for processing analysis results). Display graphically. Although the output form varies depending on the function of the post, if an element is specified, the temperature of the element can be displayed numerically.

  The CAD information database 21 stores the CAD data of the model input by the shape information input unit 11. The material information database 22 stores physical property data related to heat such as thermal conductivity, specific heat, density, and emissivity of the model input by the material information input unit 12 in association with the model. The output result database 23 stores the temperature change data of the model calculated by the temperature change calculation unit 16 in the analysis region in association with the model.

  The thermal analysis device 1 is realized by a computer including hardware such as an input device, a control device, a storage device, and an output device.

The input device is configured by input devices such as a keyboard and a mouse, for example, and the control device is, for example, a CPU (Central Processing Unit) and an I / O (CPU) connected to the CPU.
Input / Output) interface.

Storage devices include, for example, RAM (Random Access Memory), ROM (Read Only Memory)
, Hard disk drive, flexible disk drive, or CD-ROM (
The output device is composed of a display device such as a CRT (Cathode Ray Tube) or LCD (Liquid Crystal Display), or a printing device such as a printer.

  The hardware configuration is not limited to these. For example, an information database included in a CAD device or an external storage device using a data communication function may be used as an input device, and a plurality of CPUs may be used as a control device. May be used, and a configuration with excellent operability and calculation speed may be used.

  FIG. 2 is a flowchart showing the thermal analysis process. This flowchart shows processing steps by the analysis apparatus 1 shown in FIG. The thermal analysis processing operation executed by each of the above units will be described with reference to the flowchart of FIG.

  First, in step S1, model shape information input from the shape information input unit 11 is acquired.

  For example, in the case of an electronic device including an electronic board on which a heat source is mounted, the shape and dimensions of the housing, the shape and dimensions of the electronic board, the shape and dimensions of the heat source such as resistance and integrated circuit (IC chip), drill Information on the model shape, such as the shape and dimensions of the hole and the like, and the position of each of these components in the housing, and the constituent materials constituting each component are acquired.

  These pieces of information can be acquired from the CAD information database 21 when the electronic board is designed by a CAD apparatus and stored in the CAD information database 21. If it is not stored in the CAD information database 21, for example, the analysis apparatus 1 is provided with a connection interface (wired communication, wireless communication) with a CAD apparatus and a CAE (Computer Aided Engineering) apparatus, and connected to the CAD apparatus. Information may be acquired. Alternatively, it may be connected to a preprocessor of a CAE apparatus for performing thermal fluid analysis and directly acquired from the preprocessor. Or you may make it input directly with an input device and acquire.

In step S2, the material information of the model input from the material information input unit 12 is acquired.
For example, material information such as thermal conductivity, specific heat, density, and emissivity of the constituent materials constituting each component is acquired. These pieces of information may be acquired from the material information database 22 or may be newly input directly from the input device.

In step S3, the analysis condition input from the analysis condition input unit 13 is acquired.
For example, initial conditions such as the heat generation amount of the heat source, ambient temperature, heat insulation conditions between components, contact thermal resistance, boundary conditions such as heat insulation conditions and heat radiation conditions of the analysis area surface, heat transfer coefficient of the housing surface and component surface Get and set.

FIG. 3 shows a cross-sectional view of a curved surface portion that is a part of the model. In order to set the heat transfer coefficient h ₀ to the curved surface portion of the model, the approximate pre-surface area S ₀ is acquired from the shape information and set. When there are a plurality of curved surface portions for setting the heat transfer coefficient, it is necessary to acquire the heat transfer coefficient and the surface area before approximation similarly set for each curved surface portion.

  In step S4, the model is divided into elements by the orthogonal lattice method. All the models input in step S1 are approximated by orthogonal lattices, and all curved surface portions are approximated by stepped portions in which a plurality of planes are aggregated. An approximate post-surface area Sc corresponding to the curved surface portion for which the heat transfer coefficient is set in step S3 is calculated. The approximate surface area Sc can be calculated by extracting a plurality of planes approximated by element division and adding them.

  FIG. 4 is a cross-sectional view of a curved surface portion approximated by an orthogonal lattice method. When there are a plurality of curved surfaces for setting the heat transfer coefficient, the approximate post-surface area is calculated for each.

  In step S5, a corrected coefficient is calculated, and a heat transfer coefficient is set for each element-divided cell.

  Attention is paid to the heat transfer coefficient and the surface area, which are known quantities, in the relational expression of heat quantity = heat transfer coefficient × (surface temperature−ambient temperature) × surface area. The surface temperature of the cell is an unknown quantity and is a variable that is sequentially calculated in the next step S6. The ambient temperature is a known amount included in the analysis conditions, but is a fixed value and need not be corrected.

As a specific correction method, correction is performed so that the product of the heat transfer coefficient and the surface area, which is a known amount, becomes the same value before and after the approximation. That is, the approximate after coefficient _{h C,} performs a process of calculating according to the formula _{h C = h 0 × S 0} / S C. When there are a plurality of curved surfaces for setting the heat transfer coefficient, a calculation process is performed for each of them. The obtained heat transfer coefficient h _C is set for each cell corresponding to the curved surface portion set before the element division.

  In step S6, the temperature change of each cell is calculated by a finite element method, a finite difference method, a finite volume method, or the like. Thereby, one temperature change is calculated for each cell.

  In step S7, the temperature change calculated in step S6 is output as a calculation result, and the analysis process is terminated. The temperature change calculated in step S6 is also accumulated in the output result database 23 when outputting.

  The analysis apparatus 1 described above may be realized as an analysis processing program for causing a computer to function the thermal analysis processing. This analysis processing program is stored in a computer-readable recording medium. As the recording medium, a memory necessary for processing by the microcomputer, for example, a ROM (read only memory) itself may be the recording medium, or a program reading device is provided as an external storage device. It may be a recording medium that can be read by inserting a recording medium in which the analysis processing program is recorded.

  In any case, the stored analysis processing program may be configured to be accessed and executed by the microprocessor, or the analysis processing program is read out and the read program is stored in the microcomputer program storage. It may be configured to download to an area and execute the program. The download program may be stored in the apparatus main body in advance.

  Further, the recording medium is a recording medium configured to be separable from the apparatus main body, and is a tape system such as a magnetic tape or a cassette tape, a magnetic disk such as a floppy (registered trademark) disk or a hard disk, or a CD-ROM (Compact-Disc). Optical discs such as Read Only Memory (MO) (Magneto-Optical) disc / MD (Mini Disc) / DVD (Digital Versatile Disc), IC (Integrated Circuit) cards (including memory cards), optical cards, etc. It may be a medium that carries a fixed program including a semiconductor memory such as a system ROM, mask ROM, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electronically Erasable and Programmable Read Only Memory), flash ROM, or the like. When the analysis processing program is downloaded from the communication network, the download program may be stored in advance in the apparatus main body or installed from another recording medium.

It is a block diagram which shows the structure of the function of the analyzer 1 which is one Embodiment of this invention. It is a flowchart which shows a thermal analysis process. It is a figure which shows sectional drawing of the curved-surface part in three-dimensional CAD data. It is a figure which shows sectional drawing of the curved surface part approximated by the orthogonal lattice method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal analysis apparatus 10 Control part 11 Shape information input part 12 Material information input part 13 Analysis condition input part 14 Element division part by orthogonal lattice method 15 Calculation and setting part of correction | amendment heat transfer coefficient 16 Temperature change calculation part 17 of analysis area | region 17 Output Part 21 CAD information database 22 Material information database 23 Output result database

Claims (4)

An element dividing step of dividing an analysis object into a finite number of elements based on an orthogonal grid method and creating an approximate model;
A heat transfer coefficient setting step of setting a heat transfer coefficient on the surface of the approximate model;
An analysis condition setting step for setting the approximate model or the surrounding initial temperature, heat source conditions,
A temperature change calculating step of calculating a temperature change when a predetermined time elapses of the approximate model based on the approximate model, the heat transfer coefficient, the initial temperature, and the heat source condition;
In the heat transfer coefficient setting step, the heat transfer coefficient is corrected based on a ratio between a surface area of the analysis object before element division and a surface area of the approximate model corresponding thereto. In the heat transfer process, when h ₀ the heat transfer coefficient of the analysis object _surface, S ₀ the surface area of the setting surface for setting the heat transfer _coefficient, the surface area of the surfaces corresponding to the setting surface of the approximate model was S _C the heat transfer coefficient _{h C} to set the approximation _{model, h C = h 0 × S} 0 / S analysis method according to claim 1, characterized in that calculated by the formula _C. An element dividing means for dividing an analysis object into a finite number of elements based on an orthogonal lattice method and creating an approximate model;
Heat transfer coefficient setting means for setting a heat transfer coefficient on the surface of the approximate model;
Analysis condition setting means for setting the approximate model or the surrounding initial temperature, heat source conditions,
A temperature change calculating means for calculating a temperature change when a predetermined time elapses of the approximate model based on the approximate model, the heat transfer coefficient, the initial temperature, and the heat source condition;
The heat transfer coefficient setting means corrects the heat transfer coefficient based on a ratio between a surface area of the analysis object before element division and a surface area of the approximate model corresponding to the surface area.   An analysis program for causing a computer to function as the analysis apparatus according to claim 3.

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