JP3674452B2 - Solidification analysis method for castings - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for determining a generated burrow and its volume and displaying it on a screen in a solidification analysis of a cast product using an electronic computer.
[0002]
[Prior art]
In order to reduce the solidification defects called burrows that occur in products produced by casting, prior to actual production, simulation (solidification analysis) is performed by an electronic computer to predict the location and size of the burrow. It is widely performed to determine manufacturing conditions based on the results.
[0003]
In such solidification analysis, an analysis model is generally created by dividing a casting to be calculated, for example, a cylinder block of an automobile engine into a number of cells, and various calculation methods such as a heat conduction equation are generated for this analysis model. The analysis is performed by solving using.
[0004]
Based on the results of this solidification analysis, an isocoagulation time diagram showing the coagulation process and an isocoagulation diagram showing the coagulation region at a certain time during the coagulation process are obtained. Identify However, in the conventional solidification analysis, it is necessary to memorize the time change of the solid fraction distribution value in the process of solidifying the melt, that is, the process of calculating using the analysis model, for each time change. However, there is a problem in that the storage capacity of the computer required for this becomes large. Further, in the conventional method, with the progress of solidification, the distribution of coagulation shrinkage when one unsolidified region is divided into a plurality of regions, that is, the calculation of the volume of each divided region is not considered, There is a problem. Furthermore, the conventional method has a problem that it takes time to examine the generation position and size of the shrinkage nest based on the obtained result. In addition, it is possible to predict the location and size of shrinkage nests during the execution of solidification analysis calculations without storing the time change of the solid fraction distribution value for each time change. This is not practical because it significantly increases the execution time. Therefore, in the conventional coagulation analysis, it has been difficult to obtain the final position and size of the tine accurately and in a short time from the isocoagulation time diagram and the isocoagulation diagram.
[0005]
Therefore, the inventor of the present application obtained a solidification time distribution of an analytical model in JP-A-11-314152, and based on this solidification time distribution, traced the division assumption of the unsolidified region accompanying the progress of solidification. We have proposed a solidification analysis method that can relatively easily and easily obtain the location and volume of the shrinkage by determining the amount of solidification shrinkage in each region. However, in order to predict the occurrence of burrow based on solidification analysis, it is desirable that the shape and position of the burrow in the analysis model can be grasped more accurately on the screen of an electronic computer, for example.
[0006]
[Problems to be solved by the invention]
In view of such circumstances, the present invention is capable of predicting a shrinkage nest occurrence position and shape and volume in a cast product in a relatively simple and easy manner, and capable of examining analysis results in a short time. A method is proposed.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a solidification analysis method for a cast product by an electronic computer, wherein a method using an analysis model in which a cast product to be analyzed is divided into a number of cells, A step of calculating a solidification process of the molten metal over time, a step of obtaining a solidification time distribution in the analytical model by storing the solidification time of each cell obtained by the calculation, and the solidification time distribution, Determining the position and volume of the tine generated in the analysis model; determining the three-dimensional shape data of the tine from the solidification time distribution and the position and volume of the nesting; from the data of the dimensional shape, comprising a step of displaying three-dimensional shape of引巣generated within the analysis model on a screen, the step of obtaining a three-dimensional shape of the引巣A step of determining a search time for determining the shape of the nesting, a step of determining a cell having a clotting time equal to or longer than the search time and continuing to the nesting position from the clotting time distribution; and A step of determining a total volume; a step of determining whether a total volume of the determined cells is equal to a volume of the nesting; and if it is determined that the values of the two volumes are different, the exploration The time is changed, and the process returns to the step of obtaining from the coagulation time distribution a cell that is continuous with the nest position and the clotting time is equal to or longer than the exploration time. If a cell continuous with the nest position is obtained from the coagulation time distribution and it is determined that the step after the step is performed again and the two volume values are equal, the exploration time at this time Solidified cell is characterized in that it comprises the determining that a cell showing a three-dimensional shape of引巣.
[0008]
That is, in the method according to the present invention, the solidification time distribution of the molten metal in the analysis model is obtained, the position and volume of the burrow generated in the analysis model are obtained based on the solidification time distribution, and further , From the position, volume, and solidification time distribution , the three-dimensional shape of the nest generated in the analysis model is obtained, and this nest is displayed three-dimensionally on the screen. As a result, it becomes possible to easily grasp and predict the occurrence of shrinkage in the product, and it becomes possible to accurately examine the casting conditions, particularly the countermeasure against shrinkage in a short time.
[0009]
In a preferred embodiment of the method according to the present invention, each of the nests included in the list is associated with a display color on a different screen, and the nest generated in the analysis model is displayed on the screen of the computer. When performing the three-dimensional display above, each nesting is displayed in each of the display colors. As a result, it is possible to easily grasp the position and shape of the nest generated in the analysis model, and to predict the position and size of the nest in a short time.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0011]
FIG. 1 is a flowchart schematically showing the procedure of coagulation analysis according to the present invention. The procedure will be described below. First, in step 11, the melt solidification process is calculated for the model to be analyzed. This calculation is performed by solving a heat conduction equation using a conventional method, for example, a difference method. In subsequent step 12, the solidification time distribution of the analytical model, that is, the solidification time of each cell in the analytical model is recorded from the previous calculation result. In step 13, using the previously obtained solidification time distribution, the division process of the unsolidified region in the analysis model, that is, the process of division and solidification of the unsolidified portion with time is examined. In step 14, the nest volume is calculated.
[0012]
Thereafter, in step 15, a nesting list is created in which the positions (coordinates) and volumes of all nesting sites obtained in the previous steps are summarized in a list form. In step 16, the positions and shapes of all the nests included in the nest list are obtained, and the results are displayed on the screen together with the analysis model in a three-dimensional manner. Steps 11 to 14 have already been disclosed in Japanese Patent Application Laid-Open No. 11-314152 by the inventor of the present application, and detailed description thereof will be omitted.
[0013]
FIG. 2 is a flowchart showing a procedure for obtaining the position and shape of the tine in the analysis model and displaying it on the screen in the solidification analysis according to the present invention. The procedure will be described below. First, in step 21, data related to the target analysis model, which is obtained in advance by calculation of the heat conduction equation, etc., that is, the number of divisions of the analysis model, the size of the calculation cell formed by the division, and the solidification time in each cell Read the data. In subsequent step 22, the data of the nest list obtained in step 15 of the flowchart of FIG. 1 is read. In the next step 23, for each nest in the nest list, the nest shape is determined for each nest in the list based on the nest list data and calculated in each subsequent step. Set the corresponding nest index and define the nest volume.
[0014]
In the subsequent step 24, in order to obtain the shape of the nesting, an exploration time interval for obtaining cells having the same solidification time is set. Here, as initial values of variables ts and te used for calculation, ts = F [I [i]] [J [i]] [K [i]], i.e., the i th of the nest index (that is, nest list) (Corresponding to the i-th) of the nesting nest and te = 0. In the following procedure, a so-called bisection method is used. In step 25, the search time t is set as an average value of the variables ts and te. In the next step 26, cells that are continuous with the nest position and have a coagulation time t or longer are examined, and the number N is obtained. That is, the i th cell of the nesting index, that is, the cell having the same clotting time around the i th cell of the nesting list is obtained.
[0015]
In step 27, the product of the number N of cells having the same solidification time obtained in step 26 and the volume dv of each cell is calculated, and the value is calculated as V [i], that is, the i-th nest of the nest list. Compare with volume. If Ndv is larger than V [i], t is set as a new te value in step 28, and the search range is narrowed down. On the contrary, if Ndv is smaller than V [i], t is set as a new value of ts in step 29, and the search range is expanded. Thereafter, in step 30, the absolute value of the difference between te and ts is obtained. If the value is larger than the predetermined minimum value eps, it is determined that the search for the nest index i has been completed, and the obtained N cells are determined. , A cell included in the nesting index i (that is, the ith nesting in the nesting list). On the other hand, if the absolute value of the difference between te and ts is larger than eps, the process returns to step 25 in order to further reduce the search time and perform the calculation.
[0016]
Thereafter, at step 32, the nesting index i is incremented by one, and at step 33, i is compared with the nesting number CT. Here, if i is equal to CT, it is determined that the calculation has been completed for all the nests on the nest list, and the nest shape is displayed on the screen in the next step 34. Conversely, if i is not equal to CT, it is determined that the calculation has not been completed for all the nests, and the process returns to step 24.
[0017]
Next, a specific example of analysis using the method according to the present invention will be described.
[0018]
FIG. 3 shows an example of the analysis model. The illustrated analysis model 100 has a shape that connects two prisms and has two hollow portions 101 and 102. FIG. 4 shows an isocoagulation time diagram obtained as a result of the solidification analysis of the analysis model 100, and here, an arbitrary cross section of the analysis model is shown. In the coagulation analysis method according to the present invention, the position of occurrence of the nest and the size (volume) thereof are obtained based on the coagulation time distribution in the analysis model represented by the equicoagulation time diagram.
[0019]
Next, FIG. 5 shows a case in which the nest generated in the solidification analysis of the analysis model 100 and its shape are displayed on the screen of an electronic computer. As shown in the figure, it can be seen that the analysis model 100 has cavities indicated by symbols C1 to C7.
[0020]
Here, as shown in FIG. 5, each nest shown in FIG. 5 is given a serial number (nest index), and position and size information is listed (nest list). Each has a different color and a number corresponding to that color. As the color number, the nesting index in the nesting list described above can be used. That is, different colors may be associated with the nest index numbers. Here, it is assumed that indexes 1 to 7 are attached to the respective nests C1 to C7.
[0021]
Next, let us consider a case where an operator designates a specific nesting and knows its shape or the like on the screen displaying the analysis result as shown in FIG. The operator designates a specific nesting by looking at the printed nesting list or by looking at the window displaying the nesting list in which the analysis results are arranged in a graphic form on the screen. When specifying the nest, the index of the nest to be specified is input using various input devices such as a keyboard and a mouse.
[0022]
In the example shown in FIG. 5, the operator specifies the index number 6, that is, the nest indicated by the symbol C <b> 6. Thereby, the burrow C6 indicated by the portion A surrounded by a circle in FIG. 5 is displayed in a color corresponding to this. Similarly, the fact that the shrinkage C6 (index number 6) is designated is displayed in the portion B surrounded by a circle.
[0023]
In this case, the designated nest (C6 in this case) may be displayed not only in a corresponding color but also in a circle as shown in FIG. Further, the other tines C1 to C5 and C7 may be displayed in colors assigned to them, or may be displayed in the same color (for example, white or black). Alternatively, it is possible to display only the chin specified by the operator and not display the other chin.
[0024]
As described above, according to the present invention, the shrinkage volume can be easily calculated, and the capacity for storing the calculation result can be reduced. As a result, the position and volume of shrinkage cavity in casting can be predicted relatively easily and easily, and analysis results can be examined in a short time. It is also possible to make a prediction by associating the occurrence position of the shrinkage nest with the site where the occurrence should be avoided. Furthermore, the calculation accuracy of the shrinkage nest volume can be improved.
[Brief description of the drawings]
FIG. 1 is a flowchart schematically showing the procedure of coagulation analysis according to the present invention.
FIG. 2 is a flowchart showing a procedure for obtaining a shrinkage nest shape in a solidification analysis according to the present invention.
FIG. 3 is a perspective view showing an example of an analysis model.
4 is an isocoagulation time diagram in coagulation analysis using the analysis model of FIG.
FIG. 5 is a diagram showing a screen on which an analysis result is three-dimensionally displayed.
[Explanation of symbols]
100 analysis model
101,102 Hollow part

Claims (3)

In a method of solidification analysis of a cast product by an electronic computer using an analysis model in which a cast product to be analyzed is divided into a number of cells,
Calculating the solidification process of the molten metal over time in the analytical model;
Storing the solidification time of each cell obtained by the calculation to obtain a solidification time distribution in the analysis model;
From the solidification time distribution, obtaining the position and volume of the tine generated in the analysis model,
Obtaining data of the three-dimensional shape of the tine from the solidification time distribution and the position and volume of the tine;
From the three-dimensional shape data of the nesting, a step of three-dimensionally displaying on the screen the shape of the nesting generated in the analysis model;
The equipped,
Determining the three-dimensional shape of the nest;
Determining the exploration time for determining the shape of the nest;
Obtaining a cell having a solidification time equal to or longer than the exploration time and continuing to the nesting position from the solidification time distribution;
Determining the total volume of the determined cells;
Determining whether the total volume of the determined cells is equal to the volume of the nest;
If it is determined that the values of these two volumes are different, the step of changing the exploration time and obtaining a cell that is longer than the exploration time and that is continuous with the nest position from the coagulation time distribution Returning to the step, the coagulation time is equal to or longer than the changed search time, and a cell continuous with the nest position is obtained from the coagulation time distribution, and the steps after the step are performed again;
When it is determined that the two volume values are equal, the step of determining that the cell solidified in the exploration time at this time is a cell indicating the three-dimensional shape of the nesting , Solidification analysis method for castings. The method of claim 1, wherein
In the step of obtaining the exploration time, a section of a search range for setting the exploration time is set in advance and the exploration time is set in the section,
In the step of determining whether or not the total volume of the obtained cells is equal to the volume of the nest, determine the magnitude relationship between these two volume values;
In the step of changing the search time, the search range is changed by narrowing down the search range if the total volume of the obtained cells is larger than the volume of the nesting, and the search time is within the changed search range. If the total volume of the obtained cells is smaller than the volume of the nesting, the search range is changed by expanding the search range, and the search time is set within the changed search range,
After changing the search time, when returning to the step of obtaining from the coagulation time distribution and performing the processing after the step again, the width of the changed search range is obtained, and the width of the search range is a predetermined minimum value. Less than the determined volume, it is determined that the total volume of the obtained cells is equal to the volume of the traction.
A solidification analysis method for a cast product. The method according to claim 1 or 2, wherein
Obtain a list of the positions and volumes of the nests,
Corresponding display colors on the different screens to each of the nests included in the list, and when displaying the nests generated in the analysis model on the screen of the electronic computer, A solidification analysis method for a cast product, wherein the display color is displayed in each of the display colors.

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