JP2002140373A - Method for generating hexahedral mesh fem model for three-dimensional solidification analysis, and method for analyzing precise molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which can automatically generate a hexahedral mesh FEM model in a short time by putting a precise molding product, a shell mold, an accessory, and jigs, together, and to provide a precise solidification analyzing method which uses the hexahedral mesh FEM model. SOLUTION: The hexahedral mesh FEM model for a shell mold for casting a product, a hexahedral mesh FEM model for the accessory, and a hexahedral FEM model for the jigs are automatically successively generated in conformity with meshes of a hexahedral mesh FEM model for designing the product and the obtained hexahedral mesh FEM models are built to obtain the mesh FEM model for three-dimensional solidification analysis of the cast product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preparing a hexahedral mesh FEM (finite element method) model for performing solidification analysis of a precision casting, and a solidification analysis method using the mesh model.

[0002]

2. Description of the Related Art In order to produce a high-quality precision cast product, it is necessary to sufficiently analyze the solidification of the precision cast product. As a technique therefor, solidification analysis by FEM (finite element method) is effective. . In order to analyze the solidification of a precision casting by FEM, in addition to the FEM mesh model of the precision casting, the shell mold and core for casting the precision casting, and the FEM mesh of accessories such as feeder and starter You need a model.

However, in the case of normal product development,
In most cases, only the FEM model of the product is created. Therefore, when performing solidification analysis by FEM for precision casting of the product, a shell mold, core, and accessories are newly created on CAD, and then the FEM mesh model including the product is cut again. It is necessary. In this case, if the mesh model to be created is a tetrahedral mesh model, a mesh model can be created by the automatic mesh creation software because the software already exists.

FIG. 9 shows an example of a procedure for creating a mesh model in the above-described conventional manner. As shown in FIG. 9, after designing a casting plan by three-dimensional CAD, a mold and a core are created by three-dimensional CAD, and an FEM mesh model is created by using tetrahedral mesh automatic creation software as follows. . First, a core mesh is generated, a surface mesh of the core is aligned to generate a product mesh, and then a surface mesh of the product is aligned to generate a starter or feeder mesh.

[0005] Next, a mold mesh is formed by matching the surface mesh of the starter, the riser, and the product.
A cold plate mesh is created by matching the starter and the mold surface mesh, and finally a jig mesh is created. All parts of the product, mold, core, and accessories for which the mesh has been generated in this way are assembled, and a tetrahedral mesh model for solidification analysis by FEM in the case of product casting is created.

[0006] The tetrahedral mesh model created in this manner can be created with automation, so that the labor is greatly reduced, and even a complicated shape can be easily created while freely adjusting the mesh division size. There is an advantage. FIG. 10 shows a process of obtaining a tetrahedral mesh model of the FEM by the above-described procedure, and proceeding to mass production of the product through solidification analysis in casting, die production for a wax model, die production, and test casting. FIG. 9 shows a detailed process of a portion surrounded by a broken line in FIG.

However, the tetrahedral mesh model is
The arithmetic program becomes extremely complicated as compared with the hexahedral mesh model, and requires enormous amount of time, labor and cost.
Further, the reliability of the correspondence between the operation result and the actual result is poor, and the efficiency is low and the practicability is low for use in structural analysis and flow analysis. That is, it is often difficult to analyze a tetrahedral mesh model with low reliability or difficult to analyze in order to apply it to stress analysis for evaluating molten metal flow analysis or casting cracks during casting. Therefore, a hexahedral mesh model is desired. Many.

However, at present, there is no software capable of automatically creating a hexahedral mesh model while maintaining consistency between a cast product and a shell mold. Therefore, a hexahedral mesh FEM model for solidification analysis of a precision casting is manually created, and a great deal of labor and time is required to create the hexahedral mesh model.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method for solidification analysis by FEM including shell molds and accessories for product casting necessary for solidification analysis of precision castings by FEM.
To provide a method for creating a hexahedral mesh model for three-dimensional solidification analysis of precision castings that enables automatic creation of a face mesh model, and an analysis method for precision castings such as accurate solidification analysis and stress analysis by FEM. It is an issue.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problem of preparing a hexahedral mesh model for three-dimensional solidification analysis of a precision casting, the present invention relates to a method of matching a mesh of a hexahedral mesh FEM model for product design. Hexahedral mesh FEM model of shell mold for casting the same product, 6
A precision machine that automatically creates a hexahedral mesh FEM model and a hexahedral mesh FEM model of jigs sequentially and assembles the obtained hexahedral mesh FEM model to obtain a mesh FEM model for three-dimensional solidification analysis of a casting. Provided is a method for creating a hexahedral mesh FEM model for three-dimensional solidification analysis of a casting.

Although a hexahedral mesh FEM model for product design can be partially automated, generally humans use CAD.
The mesh generation is performed while instructing the computer of the detailed mesh structure by the operation. The mesh generated in this way usually has a number of finite elements arranged neatly with a topological structure dictated by humans.
It is called a structured lattice. All the three-dimensional hexahedral meshes for analysis currently manufactured are the structured grids. In the present invention, the hexahedral mesh F created for product design is used.
Utilizing that the EM model is a structural lattice, a hexahedral mesh FEM model of a shell mold for product casting, a hexahedral mesh FEM model of accessories, and a hexahedral mesh FEM model of jigs are referred to as a product surface mesh. It is generated by matching.

In this case, since the structural grid of the product generally has a structure that is stacked in the height direction, a mesh generating method for generating and stacking meshes for each layer is patterned to automatically generate the meshes described above. Can do it. Thus, according to the present invention, it is possible to significantly reduce the time required to create a hexahedral mesh FEM model for three-dimensional solidification analysis of a precision casting.

By using the hexahedral mesh FEM model obtained by the production method of the present invention, accurate three-dimensional solidification analysis of a precision casting can be quickly performed. In addition, by using the hexahedral mesh FEM model obtained by the method of the present invention, in addition to solidification analysis, stress analysis for evaluating casting cracks and the like, which is a particular problem in directional solidification precision casting, can be performed with high reliability. Can be.

If the hexahedral mesh FEM model obtained by the method of the present invention is used, not only solidification analysis of a normal cast product but also flow analysis of a molten metal can be performed with high analysis reliability. The results of the various analyzes performed in this way are easy to feed back to the design because a product design model is used, and it is easy to re-analyze with a new improved model. Can be shortened.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail by embodiments with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment shown in FIGS. 1 to 3 will be described. The first embodiment is an example of a case in which a moving mold and a stationary blade of a gas turbine are precision cast, and a hexahedral mesh FEM model of a shell mold and other accessories used for the precision casting is formed. For designing wings with platform and wing roots 6
FIGS. 1 and 2 show examples of the surface mesh in the face mesh FEM model.

Although this mesh FEM model is a surface mesh of a design hexahedral mesh FEM model that is partially and manually created by hand, a mesh model used in another analysis can be used. . For example, the surface division is performed by extracting only the free surface from the existing wing mesh model, and the wings, shank, etc. automatically extract the contour ridges of the constituent mesh, and extract the inner and outer offset ridges from the nodes forming the ridges. Alternatively, an offset mesh may be generated by connecting the ridge lines of each section.

By extracting the cross section of the uppermost surface of the wing tip portion in the wing surface mesh described above, the starter 2 is automatically generated in conformity with the wing surface mesh as shown in FIG. The mesh of the shell mold 4 is generated by matching with the mesh and the surface mesh of the blade, and then the mesh of the cooling plate 6 and other jigs is formed by matching with these meshes. As described above, a shell mold and an accessory hexahedral mesh FEM model used for precision casting of gas turbine blades can be obtained, and a solidification analysis in the case of precision casting of blades by assembling all of these parts can be obtained. It can be performed with high accuracy.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the turbine blade is used as a one-way solidified blade, and a crystal is grown in the height direction of the blade to cast a turbine blade with increased strength in the height direction of the blade, which is the direction of centrifugal force. The case is targeted. FIG. 6 shows a configuration of a shell mold and the like in the case of precision casting of the one-way solidification blade.

As shown in FIG. 6, a starter 1 is provided at the lower end.
0, the core 16 is accommodated in a shell mold 14 having a feeder 12 formed at the upper end, and the blade 18 is precision-cast. Shell mold 1
4 is heated in a heater 20, and is cooled by a water cooling chamber 24 with a cooling plate 22 attached below the starter 10.
The heater 20 and the water cooling chamber 24 are partitioned by a heat shield plate 26. The shell mold 14 is gradually lowered from the inside of the heater 20 into the water cooling chamber 24 and slowly cooled from the lower end to grow crystals in a vertical direction to cast a one-way solidified blade.

In this way, solidification analysis in the case of precision casting of the one-way solidification blade and stress analysis in the solidification process are performed. Therefore, it is matched with the surface mesh in the hexahedral mesh FEM model (structure lattice) for design of the wing 18,
Hexahedral mesh FEM such as shell mold 14 and core 16
Create a model. The production process is shown in FIG.

First, a hexahedral mesh FE for designing the wing 18
Match the inner surface mesh in the M model with the core 16
Is generated. In this case, 6 of wing 18
The mesh generation method is patterned using the fact that the planar mesh FEM model is a structured grid, and meshes are generated and stacked in the height direction. Next, a hexahedral mesh of the feeder 12 and the starter 10 is generated by matching the surface mesh of the wing 18 and similarly patterned, and the hexahedron of the cooling plate 22 is aligned with the surface mesh of the shell mold 14 and the starter 10. Mesh, and finally 6 of other jigs
A face mesh is generated similarly.

All the parts thus obtained are assembled to complete the entire three-dimensional hexahedral mesh FEM model shown in FIG. Using the three-dimensional hexahedral mesh FEM model of the entire precision casting facility obtained in this way, solidification analysis and stress analysis are performed as shown in FIG. Make a mold. Hereinafter, the mass production of the one-way solidification blade is performed through mold production and test casting. FIG. 4 shows a detailed process of a portion surrounded by a broken line in FIG.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIGS. The second embodiment is an example in which the present invention is applied to a process of manufacturing a mold by performing a molten metal flow analysis and a solidification analysis when a molten metal is put in a mold when precision casting of a turbine blade is performed by ordinary casting. It is.

FIG. 8 shows an example of equipment for manufacturing the wing by ordinary casting. The core 3 is provided in the casting space of the shell mold 30.
2 is inserted. The shell mold 30 includes a gate 34, a runner 3
6. It has weirs 38 and 40. A hexahedral mesh FEM model for this casting scheme is created by the steps shown in FIG. The steps in the broken line are the same as those described in the second embodiment with reference to FIG. 4, and a description thereof will be omitted.

After the molten metal flow analysis and solidification analysis are performed using the obtained whole hexahedral mesh FEM model, a die for a wax model and a die are manufactured, and thereafter, mass production is performed through test casting. In this manner, the flow analysis and the solidification analysis can be accurately performed using the hexahedral mesh FEM model.

As described above, the present invention has been specifically described based on the illustrated embodiments. However, the present invention is not limited to these embodiments, and the specific structure thereof is within the scope of the present invention described in the appended claims. Needless to say, various changes may be made to the configuration. For example, in the above embodiment, the case of casting a blade having a directionally solidified crystal and manufacturing a blade by ordinary casting has been described, but the present invention can be similarly applied to precision casting of a single crystal blade. Further, the casting method in each embodiment may be variously changed, and the casting is not limited to the turbine blade.

[0028]

As described above, the present invention matches the mesh of the hexahedral mesh FEM model for product design with the hexahedral mesh FE of the shell mold for casting the same.
An M model, a hexahedral mesh FEM model of accessories, and a hexahedral mesh FEM model of jigs are automatically created sequentially, and the obtained hexahedral mesh FEM model is assembled to obtain a mesh FEM for three-dimensional solidification analysis of a casting. Provided is a method of creating a hexahedral mesh FEM model for three-dimensional solidification analysis of a precision cast product from which a model is obtained.

In the present invention, as described above, by utilizing the fact that the hexahedral mesh FEM model created for product design is a structural lattice, the shell mold 6 for product casting is used.
Fahedral mesh FEM model, accessory hexahedral mesh F
EM model, hexahedral mesh FEM model of jigs,
Since it is generated in conformity with the product surface mesh, the time required to create a hexahedral mesh FEM model for three-dimensional solidification analysis of a precision casting can be significantly reduced.

The hexahedral mesh F obtained according to the present invention
By using the EM model, accurate three-dimensional solidification analysis of a precision casting can be quickly performed. The hexahedral mesh FEM obtained by the method of the present invention
If a model is used, in addition to solidification analysis, stress analysis for evaluating casting cracks and the like, which are particularly problematic in directional solidification precision casting, can be performed with high reliability. Further, if the hexahedral mesh FEM model obtained in the present invention is used, in addition to the solidification analysis of a normal casting, a molten metal flow analysis can be performed with high analysis reliability. The results of the various analyzes performed in this way are easy to feed back to the design because the product design model is used, and it is easy to re-analyze with a new improved model. Can be shortened.

[Brief description of the drawings]

FIG. 1 is a diagram showing a surface mesh of a hexahedral mesh FEM model of a wing created according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the surface mesh of FIG. 1 as viewed from a tip of a wing.

FIG. 3 is a diagram showing a surface mesh of a hexahedral mesh FEM model for three-dimensional solidification analysis in a state where a shell mold, accessories, and a jig are assembled according to the first embodiment of the present invention.

FIG. 4 shows a hexahedral mesh F according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing a procedure for creating an EM model.

FIG. 5 is a block diagram showing a procedure for performing mass production casting after solidification analysis and stress analysis using a hexahedral mesh FEM model created according to a second embodiment of the present invention.

FIG. 6 is an explanatory view showing a casting method according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a procedure from a flow analysis and a solidification analysis to a mass production casting using a hexahedral mesh FEM model created according to a third embodiment of the present invention.

FIG. 8 is an explanatory view showing a casting method according to a third embodiment of the present invention.

FIG. 9 is a block diagram showing a procedure for creating a conventional tetrahedral mesh FEM model for coagulation analysis.

FIG. 10 shows a tetrahedral mesh FEM obtained by a conventional method.
FIG. 4 is a block diagram showing a procedure up to mass production casting after solidification analysis by a model.

DESCRIPTION OF SYMBOLS 2 Starter part 4 Shell mold 6 Cooling plate 10 Starter 12 Feeder 14 Shell mold 16 Core 18 Blade 20 Heater 22 Cooling plate 24 Water cooling chamber 26 Heat shield plate 30 Shell mold 32 Core 34 Faucet 36 Runner 38 weir 40 weir 42 wing

Claims (4)

[Claims] 1. A hexahedral mesh FEM model of a shell mold, a hexahedral mesh FEM model of an accessory, and jigs and the like of a jig are matched with a mesh of a hexahedral mesh FEM model for product design. A hexahedral mesh FEM model is sequentially and automatically created, and the obtained hexahedral mesh F
A method of creating a hexahedral mesh FEM model for three-dimensional solidification analysis of a precision casting, wherein an EM model is assembled to obtain a mesh FEM model for three-dimensional solidification analysis of a casting. 2. A method for analyzing a precision casting, wherein a three-dimensional solidification analysis is performed using the hexahedral mesh FEM model generated according to claim 1. 3. The method for analyzing a directionally solidified precision casting according to claim 2, further comprising performing a stress analysis. 4. The method according to claim 2, further comprising performing a flow analysis.