JP2002283001A - Casting simulation unit, casting simulation method, casting simulation program, and computer readable recording medium with stored casting simulation program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately simulate a shifting position in a minute closed range when molten metal flowing in a casting is simulated. SOLUTION: In the case that the detected closed region is not larger than a prescribed volume or not higher than a prescribed pressure, by simulating (S1-S3) the molten metal flowing and detecting (S4) the closed region formed by the molten metal flowing, the closed region is replaced with a virtual grain having zero of the volume and zero of the mass (S5) and thereafter, the virtual grain is shifted along the molten metal flowing (S6). In this way, even in the case of becoming impossible to stably succeed a flowing body calculation using a back pressure calculated result in the conventional simulation because the volume in the closed region becomes too small or the pressure in the closed region becomes too high, the molten metal flowing can accurately be simulated to the last by making use of the virtual grain of this closed region, even in the case of applying to the actual casting having complicated shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a casting simulation apparatus, a casting simulation method, a casting simulation program, and a computer-readable recording medium storing a casting simulation program for simulating the flow of molten metal in casting.

[0002]

2. Description of the Related Art In recent years, when manufacturing a mold for a cast product,
Computer-based simulations have been performed in order to produce molds free from poor running. For example, in Japanese Patent Application Laid-Open No. 8-155625, the flow of molten metal into a mold is simulated, and as a result, how the molten metal is filled into the mold is visually observed. We are analyzing and examining the filling speed based on the ripple phenomenon.

[0003] Also, the Japan Foundry Engineering Society, 133rd National Lecture Meeting Summary Book, page 122, includes a search for a closed area in a mold and calculates a back pressure in this area, thereby involving the closed area. It is disclosed to track the amount of air that has been trapped and to simulate air entrainment.

[0004]

However, in the technique disclosed in Japanese Patent Application Laid-Open No. 8-155625, although the flow of the molten metal is simulated, no consideration is given to the entrainment of air at that time. There is a problem that even if a simulation is performed, it is not possible to predict occurrence of a casting defect caused by air entrainment.

On the other hand, according to the technology disclosed on page 122 of the 133rd Annual Meeting of the Japan Foundry Engineering Society, the entrainment of air is calculated by calculating the back pressure in a closed region, and using the calculation results to calculate the fluid. Is performed, the flow of the molten metal, which is a fluid, is determined.If the closed area has a certain size until the end, how the closed area moves is determined by the flow of the molten metal. However, when the closed region is small, the internal pressure increases, so that the convergence of the fluid calculation using the back pressure calculation value deteriorates with the increase of the pressure value. For this reason, when applied to a casting having an actual complicated shape, as the molten metal is filled, a high-pressure back pressure calculation is performed in the closed region of the complicated shape, and the molten metal is filled in the mold. May not be able to continue the fluid calculation until is completely filled.

Accordingly, an object of the present invention is to provide a casting simulation apparatus, a casting simulation method, a casting simulation program, and a computer-readable recording medium on which a casting simulation program is recorded, which can accurately simulate the movement position of a minute closed area. It is to provide.

[0007]

The object of the present invention is achieved by the following constitution.

(1) A simulation means for simulating the flow of the molten metal filled in the mold, and a closed area detecting means for detecting a closed area formed according to the flow of the molten metal when simulating the flow of the molten metal; When the closed area detected by the closed area detecting means is in at least one of a volume equal to or less than a predetermined value and a pressure equal to or higher than a predetermined value, the closed area is converted into virtual particles having a volume of 0 and a mass of 0. A casting simulation apparatus comprising: virtual particle generating means for replacing; and virtual particle moving means for moving virtual particles generated by the virtual particle generating means in accordance with the flow of molten metal.

(2) The simulation means multiplies a mold shape for simulating the flow of the molten metal by a predetermined mesh, simulates the flow of the molten metal for each cell of the mesh, and executes the closed area detecting means. Assigns an identification code to each cell to indicate whether the cell is an air cell, a molten metal or a mold part cell, and if adjacent cells around the cell of interest have an identification code indicating air, they are identified. A casting simulation device characterized by detecting as one closed region.

(3) The virtual particle generation means determines whether or not the number of cells in the closed area is equal to or less than a predetermined number when determining whether the volume of the closed area is equal to or less than a predetermined value. A casting simulation apparatus characterized by determining.

(4) The casting simulation apparatus, wherein the virtual particle generation means generates virtual particles at the position of the center of gravity of the size of the closed area.

(5) The casting simulation apparatus includes:
Further, a casting defect determining means for determining whether or not a casting defect occurs at the movement position of the virtual particle at the end of the simulation based on the air amount in the closed region at the time when the virtual particle generating means generates the virtual particle. A casting simulation apparatus comprising:

(6) A step of simulating the flow of the molten metal filled in the mold and detecting a closed region formed in accordance with the flow of the molten metal in the simulation, wherein the closed region has a volume equal to or less than a predetermined value or a predetermined value. When at least one of the above-mentioned pressures is in a state, the closed area is replaced with virtual particles having a volume of 0 and a mass of 0, and a step of moving the virtual particles according to the flow of the molten metal. A casting simulation method comprising:

(7) In the simulation, the mold shape for simulating the flow of the molten metal is multiplied by a predetermined mesh, and the flow of the molten metal is simulated for each cell of the mesh to detect the closed region. In this step, each cell is provided with an identification code indicating whether the cell is an air cell or a molten metal or a mold part cell. Is detected as one closed region.

(8) The step of generating the virtual particles includes:
When determining whether or not the volume of the closed area is equal to or less than a predetermined value, the method is performed based on whether or not the number of cells in the closed area is equal to or less than a predetermined number.

(9) The step of generating the virtual particles includes:
A casting simulation method, wherein virtual particles are generated at the position of the center of gravity of the size of the closed region.

(10) The casting simulation method further comprises determining whether or not casting defects occur at the movement position of the virtual particles at the end of the simulation, based on the air amount in the closed region at the time when the virtual particles are generated. A casting simulation method comprising the step of determining.

(11) Inputting mold shape data, setting meshes at predetermined intervals for the mold shapes, simulating the flow of molten metal filled in each cell of the meshes, Detecting a closed region formed according to the flow, and the closed region, at least one of the volume of the predetermined value or less or the pressure of the predetermined value or more,
A casting simulation program, comprising: replacing the closed region with virtual particles having a volume of 0 and a mass of 0; and moving the virtual particles in accordance with the flow of the molten metal.

(12) The step of detecting the closed area includes the step of attaching an identification code to each cell to indicate whether the cell is an air cell, a molten metal or a mold part cell, and adjoining the cell adjacent to the cell of interest. A casting simulation program for detecting an identification code indicating air as one closed region when the identification code indicates air.

(13) The step of generating the virtual particles may include determining whether the number of cells in the closed region is equal to or less than a predetermined number when determining whether the volume of the closed region is equal to or less than a predetermined value. A casting simulation program characterized by making a judgment based on the following.

(14) The casting simulation program, wherein the step of generating the virtual particles generates the virtual particles at the position of the center of gravity of the size of the closed region.

(15) The casting simulation program may further determine, based on the amount of air in the closed area at the time when the virtual particles are generated, whether or not a casting defect occurs at the movement position of the virtual particles at the end of the simulation. A casting simulation program having a determining step.

(16) A computer-readable recording medium storing the casting simulation program according to any one of (11) to (15).

[0024]

The present invention has the following effects for each claim.

According to the first aspect of the present invention, a casting simulation apparatus according to the present invention simulates a flow of a molten metal, detects a closed region formed by the flow of the molten metal, and detects the closed region having a volume equal to or less than a predetermined volume or equal to or higher than a predetermined pressure. In either case, the closed region is replaced with virtual particles having a volume of 0 and a mass of 0, and then the virtual particles are moved along the flow of the molten metal. When the simulation is performed by pressure calculation, etc., the volume of the closed area becomes too small or the pressure of the closed area becomes too high, and the fluid calculation itself using the back pressure calculation result cannot be continued stably In addition, since the closed region is virtual particles, the flow of the molten metal can be accurately simulated to the end.

According to a second aspect of the present invention, a casting simulation apparatus according to the present invention simulates a flow of a molten metal for each cell of a mesh set in a mold shape, and identifies whether each cell is air, a molten metal or a mold part. A code is attached, and this identification code is determined to detect a cell that is also air adjacent to a cell that is air as one closed region, so that it is possible to reliably detect a closed region formed by a plurality of cells. it can.

According to a third aspect of the present invention, in order to determine whether or not the volume of the closed area is equal to or less than a predetermined value, the casting simulation apparatus determines whether the number of cells in the closed area is equal to or less than a predetermined number. Therefore, the calculation of the actual volume in the closed region can be omitted, and the simulation speed can be improved.

In the casting simulation apparatus according to the present invention, virtual particles are generated at the position of the center of gravity of the closed region. Therefore, in the subsequent movement of the virtual particles, the actual closed region replaced with the virtual particles is replaced with the virtual particles. The movement position can be simulated.

According to a fifth aspect of the present invention, there is provided a casting simulation apparatus according to the present invention, wherein, based on the amount of air in a closed region at the time when virtual particles are generated, whether or not casting defects occur at the movement position of the virtual particles at the end of simulation. Is determined, it is possible to automatically find a place where a casting defect may occur automatically at the time of true termination.

According to a sixth aspect of the present invention, a casting simulation method according to the present invention simulates the flow of a molten metal, detects a closed region formed by the flow of the molten metal, and detects the closed region having a predetermined volume or less or a predetermined pressure or more. In either case, the closed region is replaced with virtual particles having a volume of 0 and a mass of 0, and then the virtual particles are moved along the flow of the molten metal. When the simulation is performed by pressure calculation, etc., the volume of the closed area becomes too small or the pressure of the closed area becomes too high, and the fluid calculation itself using the back pressure calculation result cannot be continued stably In addition, since the closed region is virtual particles, the flow of the molten metal can be accurately simulated to the end.

In the casting simulation method according to the present invention, the flow of the molten metal is simulated for each cell of the mesh set in the mold shape, and identification is performed for each cell to indicate whether it is air, molten metal or a mold part. A code is attached, and this identification code is determined to detect a cell that is also air adjacent to a cell that is air as one closed region, so that it is possible to reliably detect a closed region formed by a plurality of cells. it can.

In the casting simulation method according to the present invention, in order to determine whether or not the volume of the closed area is equal to or less than a predetermined value, the determination is made based on whether or not the number of cells in the closed area is equal to or less than a predetermined number. Therefore, the calculation of the actual volume in the closed region can be omitted, and the simulation speed can be improved.

In the casting simulation method according to the ninth aspect of the present invention, virtual particles are generated at the position of the center of gravity of the closed region. Therefore, in the subsequent movement of the virtual particles, the actual closed region replaced with the virtual particles is replaced with the virtual particles. The movement position can be simulated.

According to a tenth aspect of the present invention, there is provided a casting simulation method according to the present invention, wherein, based on the amount of air in the closed region at the time when virtual particles are generated, whether or not a casting defect occurs at the movement position of the virtual particles at the end of the simulation. Is determined, it is possible to automatically find a place where a casting defect may occur automatically at the time of true termination.

According to the present invention, a casting simulation program according to the present invention sets a mesh in a mold shape, simulates a flow of molten metal for each cell of the mesh, detects a closed region formed by the flow of molten metal, and detects the closed area. When the closed area becomes equal to or less than a predetermined volume or equal to or higher than a predetermined pressure, the closed area is set to have a volume of 0,
Was replaced with virtual particles, and then the virtual particles were moved along the flow of the molten metal.
If the volume of the closed area becomes too small or the pressure in the closed area becomes too high, and the fluid calculation itself using the back pressure calculation result cannot be continued stably, the closed area is assumed to be virtual. By using particles, the flow of the molten metal can be accurately simulated to the end.

According to a twelfth aspect of the present invention, there is provided a casting simulation program according to the present invention, wherein each cell is provided with an identification code indicating whether it is air, a molten metal or a mold, and the identification code is air adjacent to the cell having the air. Is detected as one closed region, so that a closed region formed by a plurality of cells can be reliably detected.

According to a thirteenth aspect of the present invention, the casting simulation program according to the present invention determines whether or not the number of cells in the closed area is equal to or less than a predetermined number in order to determine whether or not the volume of the closed area is equal to or less than a predetermined value. Therefore, the calculation of the actual volume in the closed region can be omitted, and the simulation speed can be improved.

According to the casting simulation program of the present invention, virtual particles are generated at the position of the center of gravity of the closed region. Therefore, in the subsequent movement of the virtual particles, the actual closed region replaced with the virtual particles is replaced with the virtual particles. The movement position can be simulated.

According to a fifteenth aspect of the present invention, there is provided a casting simulation program according to the present invention, wherein, based on the amount of air in a closed region at the time when virtual particles are generated, whether or not casting defects occur at the movement position of the virtual particles at the end of the simulation. Is determined, it is possible to automatically find a place where a casting defect may occur automatically at the time of true termination.

According to a sixteenth aspect of the present invention, a computer readable recording medium according to the present invention stores the casting simulation program according to any one of the eleventh to fifteenth aspects.
5 can be provided.

[0041]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of a simulation apparatus to which the present invention is applied, and FIGS. 2 and 3 are flowcharts showing a procedure of a casting simulation.

The simulation device 1 includes an analysis unit 1
1, a data storage device 12, an input device 13, and a display device 14.

In this apparatus, the analysis unit 11 simulates the flow of the molten metal and performs detection of a closed region, generation of virtual particles, determination of defective casting, and the like by the procedure described later. Therefore, this analysis unit functions as a closed region detection unit, a virtual particle generation unit, a virtual particle movement unit, a casting defect determination unit, and the like in the present invention.

The analysis unit 11 includes a preprocessor 31 for setting and preparing initial conditions at the time of simulation, a solver 32 for actually executing the simulation, and a postprocessor for analyzing the results of the simulation and performing processing for graphic display. 33.

The data storage device 12 stores CAD data (design data) of the mold, supplies the data to the analysis unit 11, and stores the simulation results.

The input device 13 is a keyboard, a mouse, or the like, and inputs simulation conditions.

The display device 14 is a CRT, a liquid crystal display, or the like, and displays graphics such as a flow of a molten metal in a simulation and an analysis result.

Such a simulation device is specifically realized by a computer such as a workstation or a personal computer executing a casting simulation program created in accordance with a processing procedure to which the present invention described later is applied. is there. The casting simulation program is usually provided by a computer-readable recording medium. However, the embodiment is not limited to this. For example, the casting simulation program is stored in a server computer, and the program is appropriately used as a terminal. It can be supplied in various forms, such as supplying it to a functioning computer or the like, and executing a casting simulation program by the computer of this terminal.

FIG. 2 is a main flowchart showing the procedure of a casting simulation according to the present invention.

First, the design data of the template shape is input to the preprocessor 31 from the data storage device 12, and the mesh conditions for performing the simulation are described below.
An input of a coordinate system, a step time interval, etc. is performed (S
1).

Here, the mesh conditions are as follows:
This is for determining what analysis density to simulate. For example, in the case of a three-dimensional orthogonal coordinate system, the mesh interval is determined for each of the X, Y, and Z axes. In a normal case, the mesh intervals of the X, Y, and Z axes are the same.

Subsequently, a simulation of casting by the solver 32 is performed. This simulation basically uses an analysis simulation of the flow field, and the process of filling the molten metal into the mold based on the input design data for each cell set by the mesh conditions is set. The simulation is performed for each time step.

In the simulation, first, the velocity and the pressure field are calculated for each time step from the equation of motion and the mass conservation equation (S2).

The equation of motion and the equation of conservation of mass are known, for example, vol44 of “light metal”,
No. 1, 1994, p57-66 (The Japan Institute of Light Metals, issued on January 30, 1994), the equation of motion is as shown in equation (1), and the equations for conservation of mass are as shown in equations (2) and (3). As shown in FIG.

[0056]

(Equation 1)

Here, u and v are velocity components in the x and y directions, p is a value obtained by dividing pressure by density, and ν is a kinematic viscosity coefficient. D is divergence.

The above equation expresses the relation between the velocity component of the isothermal incompressible viscous fluid and the pressure to be satisfied in a differential form.
Equation (1) is called a continuous equation (2), and equation (3) is called a Navier-Stokes equation (NS equation). A method for effectively numerically analyzing each of these equations is well known. For example, there is a SOLA method which can be executed by a small-sized computer. .

Then, based on the calculated velocity and pressure field values, the flow of the molten metal is calculated as the movement of the free surface (S).
3). The movement of the free surface is performed, for example, by the marker method or the VOF.
(Volume Of Fluid) method or the like.

Next, a closed area is detected from the result of the movement of the molten metal (S4). The detection of the closed area is performed by determining whether each cell divided by the mesh is a gas cell, a fluid cell or a cell of a mold portion (hereinafter, referred to as a mold cell), and grouping the gas cells.

For example, as shown in FIG. 4A (cells are shown two-dimensionally for the sake of simplicity of explanation), for each cell in the simulation, each cell is a gas cell. Or an identification code (ID) indicating whether the cell is a fluid cell or a type cell. In the figure, the gas cell is denoted by A, and the other molten metal and shoulders are denoted by F. The ID for each cell is assigned in the simulation according to the state of each cell according to the flow of the molten metal.

At step S4, attention is paid to one of the cells (usually, the cell with the smallest cell number). If the cell ID is a gas cell, as shown in FIG. , A closed region ID (here, a closed region number i) indicating that the region is a closed region.

Subsequently, for a cell to which a closed area ID has been assigned, a cell ID adjacent to the cell is checked. If the adjacent cell ID is also a gas ID, the same closed area I as a group together with the cell of interest is also included.
Add D. Further, adjacent cell IDs are checked, and if the gas IDs are the same, a closed region ID is assigned as the same group to form one closed region. This is sequentially performed on adjacent cells, and if all the adjacent cells have IDs other than gas, the group is registered as one closed area at that time. Here, the closed area number i
(0 <i ≦ M).

By examining all cell IDs in this way, closed areas are detected in groups.

Thereafter, for each closed area, the number Ni of cells (1 ≦ j ≦ N) is registered for each closed area number i. Here, the size of the closed region is known as "the size of one cell x the number" since the size of one cell is known from the size of the mesh input as an initial setting, and this is the volume of the closed region. Becomes The pressure is expressed as “PVγ = constant (P
Is the pressure, V is the volume, γ is the specific heat ratio (for air, usually 1.
4)))). At this time, the pressure P
Calculates the time when the closed region is completed as the atmospheric pressure. Further, the calculation of the pressure is performed by a well-known back pressure calculation in order to consider the case where the closed region is divided or united.

The calculation of the back pressure is well known as disclosed in, for example, the 133rd National Lecture Meeting Summary Book, page 122, which was also described as a conventional example, and its description is omitted here. The calculated back pressure value is used as a pressure condition in the fluid calculation.

Next, when the detected closed area matches the virtual particle generation condition, virtual particles are generated (S5).

The generation process of the virtual particles will be described. FIG. 3 is a subroutine flowchart showing a virtual particle generation processing procedure.

First, it is determined whether or not the pressure P in the closed region i is equal to or more than a predetermined value (S21) (in the initial state, i is 1).
Is). If it is not equal to or greater than the predetermined value, it is determined whether the number of cells in the closed area i is equal to or less than the predetermined number (S22). Here, if the cell number is not equal to or smaller than the predetermined value, the process proceeds to step S26, where it is determined whether or not i is equal to the total number M of the closed area (S26). If equal, the process returns to the main routine. The area number i is incremented (S27), the process returns to step S21, and the above processing is repeatedly executed. That is, the pressure and the number of cells are determined for all the closed regions. In step S22, it is determined whether the volume of the closed region is equal to or less than a predetermined value. Here, it is better to determine based on the number of cells in the closed region than the specific value of the volume. The number of cells is used to simplify the process.

On the other hand, when it is determined that the pressure P in the closed area i is equal to or more than the predetermined value, or when it is determined that the number of cells in the closed area i is equal to or less than the predetermined number,
Subsequently, the position of the center of gravity of the closed area is calculated (S23). For example, when the orthogonal coordinate system is set, the center of gravity of the closed region may be calculated by adding the coordinate values of each cell in the closed region for each axis and dividing by the number Ni of cells in the closed region group. .
For example, if the coordinate value of each cell of the closed area i is (Xj, Yj, Z
j), the position of the center of gravity (Xi, Yi, Zi) is Xi
= ΣXj / Ni, Yi = ΣYj / Ni, Zi = ΣZj /
Ni.

Subsequently, the coordinates (Xi, Yi,
A virtual particle is generated in Zi), and the virtual particle is registered with an ID number (S24). At this time, the air amount in the closed area is calculated, and the air amount is associated with the virtual particle ID and registered together.

The reason why the virtual particles are generated at the previously calculated barycentric position of the closed region is to accurately represent the actual movement position of the closed region replaced by the virtual particles in the subsequent movement of the virtual particles. is there.

Subsequently, the closed area which is set as the virtual particle is deleted (S25). At this time, the deleted closed area group number is also deleted.

Subsequently, it is determined whether or not the closed area number i is equal to the total number M of the closed areas (S26). If they are equal, the process returns to the main routine. If they are smaller, the closed area number i is incremented ( S27), returning to step S21 to repeatedly execute the above processing.

In this virtual particle generation routine, both the pressure and the number of cells are determined for each closed region because each closed region has a different volume when the closed region is formed. In a closed area where the volume at the time the area is completed is relatively large, the flow of the molten metal causes the pressure to increase and the fluid calculation using the back pressure calculation results to be stable even if the volume is not so small when the size is reduced. In order to detect such a pressure, it is determined in step S21 that the pressure has exceeded a predetermined value. On the other hand, in a closed region where the volume at the time when the closed region is completed is relatively small,
Due to the flow of the molten metal, the pressure does not increase so much even if the size is small, but if the volume becomes very small,
At that time, the pressure rapidly rises, and the fluid calculation using the back pressure calculation result cannot be stably continued. Therefore, in order to detect the volume immediately before the pressure rapidly rises, the volume in the step S22 is detected. (Number of cells) is determined to be equal to or less than a predetermined value.

It should be noted that since the pressure and volume used as the reference for generating virtual particles vary depending on the shape of the mold and the speed of the flow of the molten metal, they cannot be determined unequivocally. For example, as a result of the back pressure calculation, a pressure value at which the pressure becomes too high and the fluid calculation does not converge is one guide.

When the generation of the virtual particles is completed in this way, the process returns to the main routine, and the generated virtual particles are moved together with the flow of the molten metal (S6).

Here, the calculation of the movement of the virtual particle will be described. First, to make the explanation easier to understand,
Description will be made using a dimensional coordinate system.

First, the speed in the simulation is
As shown in FIG. 5A, it is located at the center of the boundary of each cell of the mesh. This position is called a speed definition position. It should be noted that there is a pressure defining position at the center of the cell.

Then, as shown in FIG. 5B, when a movement calculation of a certain point in the mesh is performed, the position a (X) is calculated from the coordinate value a (Xa, Ya, Za) of the certain point.
a, Ya, Za), the velocity definition position surrounding the position and the velocity at each position are extracted, and the position a (Xa, Y) is extracted.
a, Za), four areas S1 to S4
Is calculated.

Then, the speed U at a certain point a is obtained by the area average formula shown in the following formula (4).

U ′ = u1S1 + u2S2 + u3S3 + u4S4 (4) Since the speed of a certain point a is obtained in this way, the position anew after the step time t in the simulation is
anew = old + u ′ × t (old is the original position).

Similarly, in the simulation of the three-dimensional coordinate system, the position (Xi, Yi, Z
From i), the velocity at the velocity definition position on the boundary line surrounding the boundary is extracted. At this time, in order to determine the speed in each of the three dimensions, the speed in the X-axis direction is extracted as u1-8, the speed in the Y-axis direction is v1-8, and the speed in the Z-axis direction is extracted as w1-8. Then, the positions of the virtual particles (Xi, Yi, Z
The eight volumes V1 to 8 divided around i) are obtained, and the velocity in each axial direction is calculated from each of the directional axes by the volume average equation as shown in the following equations (5) to (6). u ',
v ′ and w ′ are calculated.

U ′ = u1V1 + u2V2 +... + U8V8 (5) v ′ = v1V1 + v2V2 +... + V8V8 (6) w ′ = w1V1 + w2V2 +... + W8V8 (7) Yinew, Zin
ew) can be obtained by the following equations (8) to (10). In the formula, Xiold, Yiold, Ziol
d is the original position before the movement calculation.

Xinew = Xold + u ′ × t (8) Yinew = Yold + u ′ × t (9) Zinew = Zold + u ′ × t (10) After the movement calculation, the filling rate of the molten metal is determined in advance. It is determined whether the state has been reached (S7). Here, the filling is completed, for example, when the filling rate exceeds 99%. As a result of this judgment, when the filling rate of the molten metal is less than the predetermined filling rate, the time step is updated (S8),
Returning to step S2, the process is continued. On the other hand, when the filling rate has reached the predetermined filling rate, the simulation processing ends.

After the simulation is completed, the simulation result is stored in the data storage device 12 and passed to the post-processing 33, where the simulation result is converted into graphic data and displayed on the display device 14 (S9). ).

Here, in addition to the data processing for graphic display, the post-processing 33 performs processing on the virtual particles whose air amount in the closed area registered at the time of generation of the virtual particles is equal to or more than a certain value. Assuming that there is a possibility that a casting defect may occur in the portion, a process of indicating a final position portion of the virtual particle as a failure occurrence portion in the graphic image is performed. This process is, for example, a process of coloring a location where a casting defect occurs in a graphic image of a simulation result.

Next, an example of the above-described simulation will be described with reference to FIGS. In each of the drawings, the portion filled with the molten metal is indicated by oblique lines. In addition, here, for ease of explanation, the mold is shown as a plan view. However, in an actual simulation, three-dimensional graphics may be displayed by graphics processing in post-processing.

First, as shown in FIG. 6, the mesh 151 is cut with respect to the mold 100, and the simulation is started. In the figure, the mesh (cell boundary line) is shown by a dashed line.

After a lapse of time, as shown in FIG. 7, when the molten metal 105 is introduced from the molten metal injection port 101 of the mold 100, a closed region 111 is formed inside the mold and detected. The detected closed area is registered with a group ID assigned to each cell in the closed area. In FIGS. 7 to 9, meshes are omitted for easy viewing of the drawings.

The pressure and the number of cells are determined for the detected closed region, but at this stage, virtual particles have not yet been generated.

When the filling of the molten metal progresses further after a lapse of time, the closed area is divided into a closed area 111 and a closed area 112 by the advance of the molten metal 105 as shown in FIG. Then, the pressure and the number of cells are determined for each of the two closed regions, but at this stage, virtual particles have not yet been generated.

As the filling of the molten metal progresses after a further time, as shown in FIG.
2, and a closed area 113 is formed. For each closed area,
Although the pressure and the number of cells are determined, even at this stage, virtual particles have not yet been generated.

Subsequently, as time passes and the filling of the molten metal progresses, as shown in FIG.
12, and a closed area 113 is formed. The pressure and the number of cells are determined for each closed region, but at this stage, virtual particles have not yet been generated.

Subsequently, when the filling of the molten metal proceeds after a further elapse of time, a closed region 111, a closed region 112, a closed region 113, and a closed region 114 are formed as shown in FIG. When the pressure and the number of cells are determined for each closed region, the number of cells in the closed region 113 becomes equal to or less than a predetermined value at this stage, and virtual particles 113a are generated as shown in FIG. Then, the coordinates of the position of the center of gravity of the closed region in which the virtual particles are generated are registered. Since the pressure of the closed region 114 exceeds a predetermined value, virtual particles 114a are similarly generated, and the air amount at this time and the coordinates of the center of gravity of the closed region are registered. Then, the closed regions 113 and 114 disappear. The other closed regions 111 and 1
No. 12 has not yet generated virtual particles.

The simulation is terminated when a further time elapses and finally the filling rate of the molten metal 105 reaches 99% as shown in FIG. In this state, the closed regions 111 and 112 also become virtual particles 111a and 112a as in the case of the closed regions 113 and 114 in the process of reaching here. Here, each virtual particle has a mass of 0,
Since the virtual particles have a volume of 0, the moving position can be reliably calculated along the flow of the molten metal.

Then, the air amount of each virtual particle is determined, and virtual particles 111a and 114a whose air amount is larger than a specified value are determined.
As for a, as shown in FIG. 12, it is displayed as a failure occurrence location. In addition, although it was shown by the square mark in the figure,
In the graphic display, the color may be changed.

As described above, in the present embodiment, when the closed region has a pressure equal to or higher than a predetermined pressure or equal to or lower than a predetermined volume,
Since such a closed region is assumed to be virtual particles and then moved along the flow of the molten metal, even when applied to an actual casting having a complicated shape, the pressure in the closed region increases as in the past. It is possible to continue the simulation to the end without causing a problem that the calculation cannot be performed in the middle of the simulation due to too large or too small a volume. In addition, since it is possible to detect the occurrence of a defect based on the amount of air at the final arrival point of the virtual particles, it is possible to design a mold that does not cause the defect by performing this simulation. Become.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a casting simulation apparatus to which the present invention is applied.

FIG. 2 is a flowchart showing a procedure of the casting simulation.

FIG. 3 is a subroutine flowchart showing a procedure of generating virtual particles in the above flowchart.

FIG. 4 is a diagram for explaining a closed region detection operation.

FIG. 5 is a diagram for explaining movement calculation of virtual particles.

FIG. 6 is a view showing a progress state of the casting simulation.

FIG. 7 is a view showing the progress of the casting simulation, following FIG. 6;

FIG. 8 is a drawing showing a progress state of a casting simulation, following FIG. 7;

FIG. 9 is a view showing the progress of the casting simulation, following FIG. 8;

FIG. 10 is a view showing the progress of the casting simulation, following FIG. 9;

FIG. 11 is a view showing the progress of the casting simulation, following FIG. 10;

FIG. 12 is a view showing a progress state of the casting simulation, following FIG. 11;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Simulation apparatus 11 ... Analysis part 12 ... Data storage device 13 ... Input device 14 ... Display device 100 ... Mold 101 ... Molten injection port 105 ... Molten metal 111, 112, 113, 114 ... Closed area 111a, 112a, 113a, 114a ... Virtual particle 151 ... mesh

Claims (16)

[Claims] 1. A simulation means for simulating a flow of a molten metal filled in a mold; a closed area detecting means for detecting a closed area formed according to a flow of the molten metal when simulating the flow of the molten metal; When the closed area detected by the closed area detection means is in at least one of a volume below a predetermined value or a pressure above a predetermined value, the closed area is placed on a virtual particle having zero volume and zero mass. A casting simulation apparatus comprising: a virtual particle generating unit that changes; and a virtual particle moving unit that moves the virtual particles generated by the virtual particle generating unit in accordance with the flow of the molten metal. 2. A simulation method according to claim 1, wherein the simulation unit simulates a flow of the molten metal for each cell of the mesh by applying a predetermined mesh to a mold shape for simulating the flow of the molten metal. Each cell is provided with an identification code indicating whether the cell is an air cell or a cell of a molten metal or a mold portion, and when cells adjacent to the cell of interest have identification codes indicating air, they are assigned to one cell. 2. The casting simulation apparatus according to claim 1, wherein the apparatus is detected as a closed area. 3. The virtual particle generating means determines whether or not the number of cells in the closed area is equal to or less than a predetermined number when determining whether the volume of the closed area is equal to or less than a predetermined value. The casting simulation apparatus according to claim 2, wherein: 4. The casting simulation apparatus according to claim 1, wherein the virtual particle generation means generates virtual particles at a position of the center of gravity having a size of the closed region. 5. The casting simulation apparatus further includes a casting defect at a moving position of the virtual particle at the end of the simulation, based on an air amount in a closed region when the virtual particle generating unit generates the virtual particle. The casting simulation apparatus according to any one of claims 1 to 4, further comprising a casting defect determination unit that determines whether or not the casting is defective. 6. A step of simulating a flow of the molten metal filled in the mold and detecting a closed region formed in accordance with the flow of the molten metal in the simulation, wherein the closed region has a volume less than a predetermined value or more than a predetermined value. Of at least one of the pressures, the closed area is replaced with virtual particles having a volume of 0 and a mass of 0, and a step of moving the virtual particles according to the flow of the molten metal;
A casting simulation method comprising: 7. The simulation includes: applying a predetermined mesh to a mold shape for simulating the flow of the molten metal, simulating the flow of the molten metal for each cell of the mesh, and detecting the closed region. In the step, each cell is provided with an identification code indicating whether the cell is an air cell, a cell of a molten metal or a mold portion, and if cells adjacent to the cell of interest have identification codes indicating air, they are identified. 7. The casting simulation method according to claim 6, wherein the detection is performed as one closed region. 8. The step of generating the virtual particles includes determining whether the number of cells in the closed region is equal to or less than a predetermined number when determining whether the volume of the closed region is equal to or less than a predetermined value. The casting simulation method according to claim 7, wherein the determination is made by: 9. The casting simulation method according to claim 6, wherein in the step of generating the virtual particles, the virtual particles are generated at the position of the center of gravity of the size of the closed region. . 10. The casting simulation method according to claim 1, further comprising: determining whether or not a casting defect occurs at a movement position of the virtual particle at the end of the simulation, based on an air amount in the closed region at the time when the virtual particle is generated. The casting simulation method according to any one of claims 6 to 9, further comprising the step of: 11. A step of inputting data of a mold shape, setting a mesh at a predetermined interval for the mold shape,
Simulating the flow of the molten metal filled for each cell of the mesh, and detecting a closed region formed according to the flow of the molten metal in the simulation; and the closed region has a volume less than a predetermined value or a pressure greater than a predetermined value. A step of replacing the closed region with virtual particles having a volume of 0 and a mass of 0 when at least one of the states is reached, and a step of moving the virtual particles in accordance with the flow of the molten metal. Characteristic casting simulation program. 12. The step of detecting the closed area includes the step of attaching an identification code to each cell to indicate whether the cell is an air cell, a molten metal or a mold part cell, and determining whether a cell adjacent to the cell of interest is adjacent to the cell of interest. 2. The method according to claim 1, wherein when an identification code indicating air is provided, the detection is performed as one closed area.
1. The casting simulation program according to 1. 13. The step of generating the virtual particles includes determining whether the number of cells in the closed area is equal to or less than a predetermined number when determining whether the volume of the closed area is equal to or less than a predetermined value. 13. The casting simulation program according to claim 12, wherein the determination is made by: 14. The non-transitory computer-readable storage medium according to claim 11, wherein the step of generating the virtual particles generates the virtual particles at a position of the center of gravity of the size of the closed region. . 15. The casting simulation program further determines whether or not a casting defect occurs at the movement position of the virtual particle at the end of the simulation, based on the amount of air in the closed area at the time when the virtual particle is generated. The casting simulation program according to any one of claims 11 to 14, further comprising the step of: 16. A computer-readable recording medium storing the casting simulation program according to claim 11. Description: