Method for evaluating the strength of casting defects

Abstract

To provide a method for evaluating the strength of porosities, the method suppressing degradation of the evaluation accuracy.SOLUTION: The method for evaluating the strength of porosities according to the present disclosure includes the steps of: casting a defective casting to generate a porosity in the largest stress site (ST1); and analyzing the strength of the defective casting by using defective casting shape data acquired by running a CT scan on the defective casting (ST2). The stresses of sites A1, A2, A3, A4, A5, and A6 of a defect-free casting AM1 which have the same shape as the defective casting and has no porosities are calculated before the defective casting is casted, and the largest stress site can be determined.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for evaluating the strength of casting nests.

Background Art

[0002] Patent Document 1 discloses a method for evaluating nests. In this evaluation method, the cavity part and the dendritic part are extracted as a single cavity group from the CT image of the evaluation target member, and the cavity group volume representing the volume of the cavity group is obtained. Also, the cavity part is extracted from the CT image, and the cavity part volume representing the volume of the cavity part is obtained. Then, the cavity part volume ratio representing the volume ratio of the cavity part volume to the cavity group volume is obtained, and the type of the nest of the cavity group is discriminated based on the cavity part volume ratio. By performing weighting and evaluation for each type of nest, the strength evaluation can be performed more accurately.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventors of the present application have discovered the following problems. In the above-described nest evaluation method, when the casting, which is the evaluation target member, is cast, casting nests may occur accidentally in various parts of the casting. In such a case, although the accidentally occurring nests can be evaluated, there are cases where the casting nests occurring at the maximum stress part cannot be evaluated. The casting nests occurring at the maximum stress part are predicted to have a greater adverse effect on the strength of the casting compared to the casting nests occurring at other parts. Therefore, there is a risk that the evaluation accuracy may decrease due to failure to evaluate the casting nests occurring at the maximum stress part.

[0005] The present disclosure has been made in view of the above-described problems, and provides a method for evaluating the strength of casting nests that can suppress the risk of a decrease in evaluation accuracy. [Means for solving the problem]

[0006] The method for evaluating the strength of casting defects according to this disclosure is: Defective castings are cast so that casting defects occur at the areas of maximum stress. The strength of the defective casting is analyzed using the shape data of the defective casting obtained by CT scanning the defective casting.

[0007] Furthermore, in the above-mentioned method for evaluating the strength of casting defects, Before casting the aforementioned defective casting, The location of the maximum stress may be determined by calculating the stress at each part of a defect-free casting that has the same product shape as the defective casting and is free of casting defects.

[0008] Furthermore, in the above-mentioned method for evaluating the strength of casting defects, After casting the aforementioned defective casting, Using the acquired defective casting shape data, a casting cavity model is generated that shows the shape of the casting cavity that occurred at the maximum stress location. A cavity defect model encompassing the aforementioned casting cavity model is generated, The strength of the defective casting may be analyzed using the cavity defect model and the product shape model showing the product shape of the defective casting. [Effects of the Invention]

[0009] According to this disclosure, the risk of a decrease in evaluation accuracy can be suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a flowchart showing the method for evaluating the strength of casting defects according to Embodiment 1. [Figure 2] This is a diagram showing the stress distribution. [Figure 3] This is a schematic diagram showing the nest evaluation method according to Embodiment 1. [Figure 4] This is a schematic diagram showing the analysis model. [Figure 5]This is a cross-sectional view of the analysis model. [Modes for carrying out the invention]

[0011] Specific embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings have been simplified as appropriate.

[0012] <Embodiment 1> A method for evaluating the strength of casting defects according to Embodiment 1 will be described with reference to Figure 1.

[0013] It should be noted that the right-handed XYZ coordinate system shown in Figure 2 and other drawings is merely for convenience in explaining the positional relationships of the components. Typically, the positive Z-axis direction is vertically upward, and the XY plane is the horizontal plane, and this is consistent across drawings.

[0014] Defective castings are cast so that casting defects occur at the highest stress points (Step ST1). Specifically, it is advisable to use known casting simulation software beforehand to determine the worst casting conditions under which casting defects occur intensively at the highest stress points of the defective casting. Defective castings are then cast using these determined worst casting conditions. Alternatively, multiple castings may be cast using different casting conditions, and then only those castings in which casting defects occur at the highest stress points may be selected from these multiple castings. These selected castings are treated as defective castings. Casting defects are not particularly limited, but examples include porosity, blowholes, pinholes, shrinkage cavities, and voids. Defective castings are not particularly limited, but examples include those made of metallic materials such as aluminum alloys. The product shape of the defective castings is not particularly limited, but examples include those with the same shape as vehicle parts.

[0015] The strength of the defective casting is analyzed (step ST2) using the defective casting shape data obtained by subjecting the defective casting to a CT (Computed Tomography) scan. Specifically, a known CT scan device is used to perform a CT scan on the defective casting to obtain the defective casting shape data. Using this obtained defective casting shape data, a porosity model showing the shape of the porosity generated at the maximum stress site is generated. A cavity defect model including the porosity model is generated. The strength of the defective casting is analyzed using the cavity defect model and a product shape model showing the product shape of the defective casting. It is advisable to analyze the strength of the defective casting using known strength analysis software.

[0016] Note that before step ST1, the stress at each part of the defect-free casting may be calculated to determine the maximum stress site of the defective casting. The product shape of the defect-free casting is the same as that of the defective casting. The defect-free casting preferably has no porosity at all. For example, the inside of the defect-free casting preferably has no space and is completely filled with the metal material constituting the casting. Therefore, the product shape of the defect-free casting does not include the shape of the porosity. Known stress analysis software may be used to calculate the stress at each part of the defect-free casting in the environment where the defect-free casting is used. At each part of the defect-free casting, the part with the highest stress is confirmed. This confirmed part with the highest stress may be treated as the maximum stress site of the defective casting.

[0017] From the above, according to the porosity strength evaluation method according to the above-described Embodiment 1, the strength can be evaluated using a casting in which porosity is intentionally generated at the maximum stress generation site. Since it is possible to suppress overlooking the evaluation of the porosity generated at the maximum stress site, it is possible to suppress the risk of a decrease in evaluation accuracy.

[0018] <An example> Next, an example of the porosity strength evaluation method according to the above-described Embodiment 1 will be described with reference to FIGS. 2 to 5. FIG. 5 is an enlarged cross-sectional view of the analysis model shown in FIG. 4.

[0019] Before step ST1, the stress at each part of the defect-free casting AM1 shown in Figure 2 is calculated to determine the location of the maximum stress in the defective casting. In the stress distribution of the defect-free casting AM1 shown in Figure 2, each part A1, A2, A3, A4, A5, and A6 shows different stress values. The stress values ​​are highest in the order of A6, A5, A4, A3, A2, and A1. Therefore, part A6 is the location of the maximum stress in the defect-free casting AM1.

[0020] In step ST1, a defective casting is cast so that a casting defect occurs at location A6.

[0021] In step ST2, the defective casting is CT scanned to obtain the shape data of the defective casting. This obtained shape data of the defective casting shows the shape of the casting cavity PC shown in Figure 3. The casting cavity PC is located at location A6.

[0022] Using this acquired defective casting shape data, a casting void model (PM) is generated. The casting void model (PM) shown in Figure 3 is generated by modeling the shape of the casting void (PC). For example, point cloud data representing the shape of the casting void (PC) may be generated from the shape of the casting void (PC), and then this generated point cloud data may be converted into polygon data to generate the casting void model (PM).

[0023] As shown in Figures 3 to 5, a cavity defect model PDM is generated. The partial diagram FF shown in Figure 3 is an enlarged cross-sectional view of the analysis model shown in Figure 4. The cavity defect model PDM only needs to contain the casting void model PM, for example, a sphere or ellipsoid that contains the casting void model PM. An analysis casting model AM2 is generated using the cavity defect model PDM and the product shape model PPM of the defective casting. The analysis casting model AM2 comprises the product shape model PPM and the cavity defect model PDM. The cavity defect model PDM is located at part A6 of the product shape model PPM. The strength of the analysis casting model AM2 is analyzed. Since the cavity defect model PDM contains the casting void model PM, it has a larger volume than the casting void PC. Therefore, the influence of the casting void on the strength of the defective casting is increased, and the evaluation accuracy of the strength analysis of the analysis casting model AM2 can be improved. This makes it possible to improve the evaluation accuracy of the strength of the defective casting.

[0024] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. Furthermore, the present invention may be implemented by combining the above embodiments or examples thereof as appropriate. [Explanation of Symbols]

[0025] A1, A2, A3, A4, A5, A6 parts AM1 Defect-Free Casting AM2 Analysis Casting Model PC casting hole PM casting void model PDM Cavity Defect Model PPM Product Shape Model FF Partial Diagram

Claims

1. Defective castings are cast so that casting defects occur at the areas of maximum stress. The strength of the defective casting is analyzed using the shape data of the defective casting obtained by CT scanning the defective casting. Method for evaluating the strength of casting defects.

2. Before casting the aforementioned defective casting, The stress at each part of a defect-free casting having the same product shape as the aforementioned defective casting and free from casting defects is calculated to determine the location of the maximum stress. The method for evaluating the strength of a casting defect according to claim 1.

3. After casting the aforementioned defective casting, Using the acquired defective casting shape data, a casting cavity model is generated that shows the shape of the casting cavity that occurred at the maximum stress location. A cavity defect model encompassing the aforementioned casting cavity model is generated, The strength of the defective casting is analyzed using the cavity defect model and the product shape model showing the product shape of the defective casting. A method for evaluating the strength of a casting defect according to claim 1 or 2.

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