JP2020144819A - Method of analyzing cause of occurrence of shape defect, shape defect correction method, device for analyzing cause of occurrence of shape defect, program for analyzing cause of occurrence of shape defect and recording medium - Google Patents

Abstract

To provide a method of analyzing a cause of the occurrence of shape defect allowing for identification of a region becoming the main cause of the occurrence of the shape defect of a press-formed article due to a hot stamp construction method, and provide a shape defect correction method, a device for analyzing the cause of the occurrence of shape defect, a program for analyzing the cause of the occurrence of shape defect and a recording medium.SOLUTION: The method of analyzing the cause of the occurrence of shape defect of a press-formed article is provided that comprises a press forming analysis step, a metallic mold cooling analysis step, a first stress value calculation step, a first shape defect value calculation step, a parameter change step, a second stress value calculation step, a second shape defect value calculation step, a shape defect value comparison step, a difference value calculation step and a shape defect factor identification step.SELECTED DRAWING: Figure 1

Description

The present invention relates to a shape defect occurrence cause analysis method, a shape defect correction method, a shape defect occurrence cause analysis device, a program for analyzing a shape defect occurrence cause, and a recording medium.

Conventionally, many automobile members such as door beams, pillars and bumpers are manufactured by press forming a metal plate such as a steel plate. In recent years, in order to reduce the weight of these members, there is an increasing demand for higher strength and higher functionality. In order to meet this requirement, the application of automobile skeleton members having a strength distribution by the hot stamping method is expanding.

In the molding process and the cooling process by the hot stamping method, non-uniform contact with the mold and the like occur, and a temperature distribution occurs in the member. Further, when a member having a strength distribution is manufactured, mold heating, partial cooling, and the like are performed, so that a larger temperature distribution is generated in the member. When such a temperature distribution occurs, the phase transformation of the material becomes non-uniform, so that the residual stress locally increases. When the component is removed from the mold, this residual stress is released, so that the shape of the component is defective.

Countermeasures against such shape defects are required, but in the hot stamping method, specific shape defect countermeasure methods have been established because component rigidity and temperature non-uniformity mutually affect shape defects. Absent. Further, the same situation applies to a member having a strength distribution in the member.

As a countermeasure against shape defects in conventional cold forming, the springback factor analysis system is used to virtually rewrite the stress that is the cause of springback of parts, analyze the main factor part of springback, and analyze that part. Measures to reduce stress have been taken (Patent Document 1).
Further, a method of analyzing a portion causing springback at the design stage of a molded product has also been proposed (Patent Document 2).

Japanese Patent Application Laid-Open No. 2008-090481 Japanese Patent Application Laid-Open No. 2009-172677

Although the above-mentioned analysis methods have been studied, the cause of the shape defect of hot forming by the hot stamping method is mainly due to the stress distribution generated as a result of temperature non-uniformity. In view of these, as a countermeasure against shape defects, a system is assumed in which the temperature is virtually partially rewritten sequentially and the main cause of the shape defects is analyzed.

However, in the hot stamping method, strain and thermal strain (expansion and contraction) occur due to phase transformation during cooling by the die, so it is possible to predict the stress at the press bottom dead center as easily as in cold forming. could not. Therefore, the present inventors have investigated a stress analysis system that considers phase transformation and thermal strain in hot forming using a numerical computer.
Then, the present inventors have integrated the conventional analysis method of the cause of failure and the stress analysis system considering the phase transformation / thermal strain in hot forming, so that the temperature non-uniformity during hot forming will die after cooling. We found that the effect on the stress distribution at points can be analyzed numerically. Furthermore, by performing temperature control such as partial water cooling and partial heating for the main cause of shape defects obtained as a result of this analysis, it can be expected to realize high-performance automobile parts with high strength and excellent shape accuracy. I found it.

An object of the present invention, which has been made in view of such a situation, is to provide a method for analyzing the cause of shape defect occurrence, which can identify a portion which is a main cause of shape defect of a press-formed product by a hot stamping method. .. Another object of the present invention is to provide a shape defect correction method capable of proposing a correction method for a portion specified as a main cause of shape defects in a press-formed product by a hot stamping method.
Further, an object of the present invention is an analysis device for causing shape defects, a program and recording for analyzing the causes of shape defects, which can identify a portion which is a main cause of shape defects in a press-formed product by the hot stamping method. To provide a medium.

(1) The method for analyzing the cause of shape defects according to one aspect of the present invention is
This is a method for analyzing the cause of shape defects in press-formed products.
A press molding analysis process that performs press molding analysis by numerical simulation and calculates molding data for the press molded product based on the molding conditions of the press molded product.
A mold cooling analysis process that calculates molding data for mold cooling products by mold cooling by numerical simulation,
A first stress value calculation step for calculating the first stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the mold-cooled product.
The first shape defect value calculation step of calculating the first shape defect value based on the first stress value of the mold cooling product obtained by the first stress value calculation step, and
A parameter change process that divides the press-formed product into multiple regions and changes the parameters of each region,
The second stress value of the die-cooled product is calculated based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product whose parameters have been changed in the parameter changing process and the molding data of the mold-cooled product. Second stress value calculation process and
A second shape defect value calculation step for calculating a second shape defect value based on the second stress value of the mold cooling product obtained by the second stress value calculation step, and a second shape defect value calculation process.
A shape defect value comparison step for comparing the first shape defect value and the second shape defect value, and
The difference value calculation process for calculating the difference value between the first shape defect value and the second shape defect value, and
Based on the result of the difference value calculation process, the shape defect factor identification process that identifies the shape defect factor region from the area where the parameters are changed, and the shape defect factor identification process.
It is characterized by including.
(2) In the method for analyzing the cause of shape defects described in (1) above,
In the parameter change process, change the area to change the parameter and the parameter,
The parameter changing process, the second stress value calculation process, the second shape defect value calculation process, the shape defect value comparison process, and the difference value calculation process are repeated.
When the second shape defect value is smaller than the first shape defect value and the second shape defect value is the smallest in the shape defect value comparison step and the difference value calculation process, or the second shape is smaller than the first shape defect value. The region in which the parameter is changed when the defective value is small and the difference value is the largest may be specified as the shape defect factor region.
(3) In the method for analyzing the cause of shape defects according to (1) or (2) above,
The parameters are selected from the group consisting of temperature, plate thickness, thermal conductivity, stress component value, strain component value, coefficient of thermal expansion, transformation plasticity coefficient, specific heat, and chemical component of the work material of the press-formed product. It may be one kind or two or more kinds.

(4) The method for correcting a shape defect according to another aspect of the present invention is
In the transfer process or press process from heating the work material of the press-formed product to installing it in the die.
It is characterized in that the region of the cause of shape defect identified by the method for analyzing the cause of occurrence of shape defect according to any one of (1) to (3) above is partially cooled, kept warm or heated.
(5) The shape defect correction method according to another aspect of the present invention is
In the transfer process or press process from heating the work material of the press-formed product to installing it in the die.
It is characterized in that a region other than the shape defect factor region specified by the shape defect occurrence cause analysis method according to any one of (1) to (3) above is partially heated, kept warm or cooled. And.
(6) The method for correcting a shape defect according to another aspect of the present invention is
In the transfer process or press process from heating the work material of the press-formed product to installing it in the die.
To change the plate thickness of the shape defect factor region or the plate thickness of the region other than the shape defect factor region specified by the shape defect occurrence cause analysis method described in any one of (1) to (3) above. It is a feature.
(7) The method for correcting a shape defect according to another aspect of the present invention is
In the press process after heating the work material of the press-formed product and then installing it in the die.
The clearance of the mold facing the shape defect factor region or the mold facing the region other than the shape defect factor region identified by the shape defect occurrence cause analysis method according to any one of (1) to (3) above. It is characterized by changing the clearance of the mold.

(8) The shape defect occurrence cause analyzer according to one aspect of the present invention is
A press molding analysis unit that performs press molding analysis of a press-molded product and calculates molding data of the press-molded product based on the molding conditions of the press-molded product.
A mold cooling analysis unit that calculates molding data for mold cooling products by mold cooling,
A first stress value calculation unit that calculates the first stress value of the mold cooling product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the mold cooling product.
The first shape defect value calculation unit that calculates the first shape defect value based on the first stress value,
A parameter change section that divides the press-formed product into multiple regions and changes the parameters of each region,
A second stress value that calculates the second stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product with changed parameters and the molding data of the mold-cooled product. Calculation part and
A second shape defect value calculation unit that calculates a second shape defect value based on the second stress value of the mold cooling product, and
A shape defect value comparison unit that compares the first shape defect value and the second shape defect value,
A difference value calculation unit that calculates the difference value between the first shape defect value and the second shape defect value,
The shape defect factor identification part that identifies the shape defect factor area from the area where the parameters are changed,
It is characterized by having.
(9) In the shape defect occurrence cause analyzer according to (8) above,
The part that identifies the cause of the shape defect is
When the second shape defect value is smaller than the first shape defect value and the second shape defect value is the smallest, or when the second shape defect value is smaller than the first shape defect value and the difference value is the largest. The area in which the parameters have been changed and the parameters may be specified as a cause of shape defects.

(10) The program according to one aspect of the present invention is
This is a program for analyzing the causes of shape defects in press-formed products.
Press molding analysis is performed by numerical simulation, and molding data of the press molded product is calculated based on the molding conditions of the press molded product.
Processing to calculate molding data of mold cooled products by mold cooling by numerical simulation,
A process of calculating the first stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the mold-cooled product.
The process of calculating the first shape defect value based on the first stress value of the mold cooling product, and
The process of dividing the press-formed product into multiple regions and changing the parameters of each region,
A process of calculating the second stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product whose parameters have been changed and the molding data of the mold-cooled product.
The process of calculating the second shape defect value based on the second stress value of the mold cooling product, and
The process of comparing the first shape defect value and the second shape defect value,
Processing to calculate the difference value between the first shape defect value and the second shape defect value,
Processing to identify the shape defect cause area from the area where the parameters are changed,
Is a program to make a computer execute.
(11) The recording medium according to one aspect of the present invention is a computer-readable recording medium in which the program described in (10) above is stored.

According to the present invention, a method for analyzing the cause of a shape defect that can identify a portion that is a major cause of a shape defect of a press-molded product by the hot stamping method, and a main cause of a shape defect of a press-molded product by the hot stamping method. A shape defect correction method that can propose a correction method for the part specified as, a shape defect occurrence cause analyzer that can identify the part that is the main cause of the shape defect of the press-formed product by the hot stamping method, and a shape defect. Programs and recording media for analyzing the cause can be provided.

It is a flow chart for demonstrating the shape defect occurrence cause analysis method which concerns on 1st Embodiment of this invention. It is a figure for demonstrating an example of the data table which concerns on this embodiment. It is a figure for demonstrating an example of the data table which concerns on this embodiment. It is a figure for demonstrating an example of the data table which concerns on this embodiment. It is a figure for demonstrating an example of the data table which concerns on this embodiment. It is a figure which shows the example which divided the press-molded product into a plurality of regions by the shape defect occurrence cause analysis method which concerns on 1st Embodiment of this invention. It is a figure for demonstrating an example of the data table which changed the parameter which concerns on this embodiment. It is a figure for demonstrating an example of the data table which changed the parameter which concerns on this embodiment. It is a figure for demonstrating an example of the data table which changed the parameter which concerns on this embodiment. It is a figure explaining that the part which is the main cause of the shape defect was identified by the shape defect occurrence cause analysis method which concerns on 1st Embodiment of this invention. It is a figure which showed the degree of influence of the part which is the main cause of the shape defect in the shape defect occurrence cause analysis method which concerns on 1st Embodiment of this invention. It is a figure which showed the degree of influence of the part which is the main cause of the shape defect and the part which can be dealt with in the shape defect occurrence cause analysis method which concerns on 1st Embodiment of this invention. It is the schematic for demonstrating the structure of the shape defect occurrence cause analysis apparatus which concerns on 4th Embodiment of this invention. It is a figure which showed the influence degree of the part which is the main cause of the shape defect and the part which can be dealt with, which was output in the Example of this invention.

In order to ensure the shape accuracy of the parts of the hot-molded product by the hot stamping method, the present inventors predict the product shape with high accuracy using CAE as in the case of cold molding, and efficiently take measures against the method. We found that it is effective to hit. In cold forming, by partially deleting or changing the stress and Young's modulus on a computer, it is possible to identify the cause of the shape defect of the press-formed part and take measures such as giving the shape.
On the other hand, for example, in hot / warm forming of a steel plate, so-called hot stamp forming, there are a heated part, a non-heated part, and a cooling part in the mold, and the mold and the heated steel plate are partially contacted and cooled to form a steel plate. There is a problem that it is difficult to predict the stress at the bottom dead point of the press and the shape after cooling because the transformation strain and the thermal strain occur due to the phase transformation of the internal structure of the press.

The present inventors consider the phase transformation and thermal strain in hot and warm forming, and provide a system that can predict the stress after the phase transformation so that the temperature distribution of hot and warm forming is after cooling. Based on the idea that the effect on the stress distribution at the bottom dead point can be analyzed numerically, the shape of the press-molded part is formed by partially changing the temperature distribution of the molded product at the bottom dead point after cooling. We have come to the conclusion that it is possible to take measures such as identifying the cause of the defect and giving it a shape.

Hereinafter, embodiments of the present invention will be described with reference to examples, but it is obvious that the present invention is not limited to the examples described below. In the following description, specific numerical values and materials may be exemplified, but other numerical values and materials may be applied as long as the effects of the present invention can be obtained.

[First Embodiment]
In the first embodiment, the method for analyzing the cause of shape defect occurrence of the present invention will be described.
The shape defect cause analysis method according to the present embodiment is a shape defect occurrence cause analysis method for a press-molded product, and press-molding analysis is performed by numerical simulation, and the press-molded product molding data is based on the molding conditions of the press-molded product. Obtained from the press molding analysis process that calculates, the mold cooling analysis process that calculates the molding data of the mold cooling product by mold cooling by numerical simulation, the molding data of the press molding product, and the molding data of the mold cooling product. The first stress value calculation step of calculating the first stress value of the mold cooling product based on the temperature change and the amount of strain during press molding, and the first of the mold cooling products obtained by the first stress value calculation step. The first shape defect value calculation step of calculating the first dimensional accuracy defect value based on the stress value, the parameter change process of dividing the press-formed product into a plurality of regions and changing the parameters of each region, and the parameter change process. The second stress that calculates the second stress value of the mold cooling product based on the temperature change and strain amount during press molding obtained from the molding data of the press molded product and the molding data of the mold cooling product whose parameters have been changed in The second shape defect value calculation step for calculating the second shape defect value based on the value calculation step and the second stress value of the mold cooling product obtained by the second stress value calculation step, and the first shape defect value. Based on the results of the shape defect value comparison step of comparing the first shape defect value with the second shape defect value, the difference value calculation process of calculating the difference value between the first shape defect value and the second shape defect value, and the difference value calculation process. It includes a process for identifying a shape defect factor that identifies a shape defect factor region from a region in which parameters are changed.

The hot stamping method uses a heating furnace or an energizing heating device to heat and transport the work material to 700 to 1000 ° C., install the work material in a mold for press molding, and cool it together with press molding. This is a method of obtaining a molded product. In the method for analyzing the cause of shape defects according to the present embodiment, the work material is heated to 700 to 1000 ° C., the work material is molded at 400 to 850 ° C., and then cooled at a cooling rate of 1 to 1000 ° C./s. It can be preferably used in the hot stamping method.
Poor dimensional accuracy includes, for example, springback and twisting due to thermal strain. Springback is a phenomenon in which an error occurs in a press-formed product after press forming due to a stress locally generated in a work material during press forming.

Hereinafter, the method for analyzing the cause of shape defects according to the present embodiment will be described together with the flow chart of FIG.

First, the steps for calculating the first shape defect value (S100 to S108) will be described.

(Press molding analysis process)
In the press molding analysis step, molding conditions are input (S100), and press molding analysis is performed by numerical simulation (S102).
In the press molding analysis step, the molding data of the press molded product is calculated based on the input molding conditions of the press molded product. The molding conditions include the chemical composition of the work material (for example, the material steel plate), the shape data of the work material, the plate thickness, the heating condition, the transport time of the work material, the cooling condition, the thermal conductivity, the heat transfer coefficient, and the thermal expansion. Includes coefficients, transformational plasticity coefficients, specific heat, and mold shape data. The molding conditions of the press-molded product may be input to a computer-readable / readable / writable recording medium as, for example, a data table as shown in FIG. 2 or FIG.

The molding data of the press-molded product means the molding data after the work material is heated and press-molded. The molding data of the press-molded product includes the temperature, plate thickness, thermal conductivity, stress component value, strain component value, and phase fraction of the press-molded product.

The molding data of the press-molded product may be stored in a computer-readable / readable / writable recording medium as, for example, a data table as shown in FIG.
The fraction of the phases constituting the work material can be calculated from the chemical composition of the work material and the heating history input as the molding conditions. Further, the coefficient of thermal expansion of the material to be processed is calculated from the fraction of the phases constituting the material to be processed and the coefficient of thermal expansion of each phase. Further, the transformation plasticity coefficient of the work material is calculated from the fractions of the phases constituting the work material and the transformation plasticity coefficient of each phase.

(Mold cooling analysis process)
In the mold cooling analysis step, molding data of the mold cooled product after mold cooling is calculated by numerical simulation (S104).
The molding data of the mold-cooled product means the molding data after holding the bottom dead center during press molding by the hot stamping method. The molding data of the die-cooled product includes the temperature, plate thickness, stress component value, strain component value, and phase fraction of the press-molded product.
The change in the fraction of the phase constituting the work material can be calculated and updated from the cooling history obtained by the press forming analysis. The coefficient of thermal expansion of the material to be processed is calculated from the fractions of the phases constituting the updated material to be processed and the coefficient of thermal expansion of each phase. Further, the transformation plasticity coefficient of the work material is calculated from the fractions of the phases constituting the work material and the transformation plasticity coefficient of each phase.

The molding data of the mold cooling product may be stored in a computer-readable / readable / writable recording medium as a data table as shown in FIG.

(First stress value calculation process)
The first stress value of the die-cooled product is calculated based on the momentary temperature change and strain amount during press molding obtained when analyzing the molding data of the press-molded product and the molding data of the mold-cooled product (S106). ).

(First shape defect value calculation process)
In the first shape defect value calculation step, the first shape defect value is calculated based on the first stress value obtained by the calculated first stress value calculation step of the press-formed product or the mold cooling product (S108). ..

The shape defect value is the amount of difference in shape accuracy with respect to the design value at an arbitrary location of the press-formed product.
In the example of this embodiment, the shape defect value is the height direction z of the point b (the longitudinal direction x of the press-formed product 10) when the points a and a'are constrained in the press-formed product shown in FIG. The amount of displacement in the direction perpendicular to the width direction y). In the example of this embodiment, the displacement amount of point b with respect to the design value is set as the shape defect value.

The first shape defect value calculated in the first shape defect value calculation process is a calculated value indicating how much the press-molded product molded by the hot stamping method has an error with respect to the design value of the press-molded product. Is. As described above, in hot stamping, there are a heated part, a non-heated part, and a cooling part in the mold, and the mold and the heated material steel sheet are partially contacted and cooled to undergo phase transformation in the internal structure of the material steel sheet. And thermal distortion occur. The first shape defect value is a shape defect value in consideration of such phase transformation and thermal strain.

Next, the steps for calculating the second shape defect value (S110 to S122) will be described. These steps may be performed in parallel regardless of the order in which the first shape defect value calculation steps (S100 to S108) and the second shape defect value calculation steps (S110 to S122) are performed.
In the following description, the description of the overlapping configuration in the first shape defect value calculation step (S100 to S108) and the second shape defect value calculation step (S110 to S122) will be omitted.

(Press molding analysis process)
In the press molding analysis step, molding conditions are input (S110), and press molding analysis is performed by numerical simulation (S112).
In the press molding analysis step, the molding data of the press molded product is calculated based on the input molding conditions of the press molded product.

(Mold cooling analysis process)
In the mold cooling analysis step, molding data of the mold cooled product by mold cooling is calculated by numerical simulation (S114).

(Parameter change process)
In the parameter changing step, the press-formed product is divided into a plurality of regions (S116).
Specifically, the area division software is used to virtually divide the surface of the press-formed product into a plurality of areas. The region to be divided may be determined based on the shape of the press-formed product and the like, and is preferably divided into a number of 5 to 200 in the width direction and 5 to 400 in the longitudinal direction.

FIG. 6 shows an example in which the press-formed product 10 is divided into 7 regions in the width direction and 10 regions in the longitudinal direction. In the example of FIG. 6, the areas of the ridge line portion and the flat surface portion are different, and it is preferable to divide the ridge line portion, the top plate surface, and the vertical wall portion so as to separate them.

Then, the parameters of each of the divided regions are changed (S118).
7 to 9 show an example of a data table when changing the parameters of each divided area.
For example, in FIG. 7, the area is divided into X pieces, and the temperature of only the area 4 is changed to 540 ° C. By continuously processing, X pieces of pre-molding input data in which the temperature of only one of the areas 1 to X is changed are created. For example, in FIG. 8, the area is divided into X pieces, and the plate thickness of only the area 1 is changed to 1.6 mm. By continuously processing, X pieces of pre-molding input data in which the plate thickness of only one of the areas 1 to X is changed are created. Further, for example, in FIG. 9, the area is divided into X pieces, and the heat transfer coefficient of only the area 4 is changed to 2600 W / m ² · K. By continuously processing, X pieces of pre-molding input data in which the heat transfer coefficient of the mold in only one region 1 to X is changed are created.

The parameters to be changed in the parameter change process are temperature, plate thickness, thermal conductivity, stress component value, strain component value, coefficient of thermal expansion, transformation plasticity coefficient, specific heat, chemical component of material steel plate, and gold of the press-formed product. It is preferably one or more selected from the group consisting of the heat transfer coefficient with the mold.
The parameter to be changed in the parameter changing step is more preferably one selected from the group consisting of temperature, plate thickness, thermal conductivity, specific heat, and heat transfer coefficient with the mold of the press-formed product.

(Second stress value calculation process)
In the second stress value calculation step, the mold cooling product is based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product whose parameters are changed in the parameter changing step and the molding data of the mold cooling product. The second stress value of is calculated (S120).

(Second shape defect value calculation process)
In the second shape defect value calculation step, the second shape defect value is calculated based on the second stress value of the mold cooling product obtained in the second stress value calculation step (S122).
The method for calculating the second shape defect value and the like is the same as the method for calculating the first shape defect value described above.

(Shape defect value comparison process)
In the shape defect value comparison step, the first shape defect value and the second shape defect value are compared at the evaluation point (S124). It is desirable that the evaluation point is a position away from the restraint point for calculating the shape defect value. For example, b, which is a position away from the restraint points a and a'shown in FIG. 6, is an evaluation point.
In the shape defect value comparison step, the absolute values of the first shape defect value and the second shape defect value calculated in the above steps S100 to S122 are compared, and which of the first shape defect value and the second shape defect value is Determine if it is large.

(Difference value calculation process)
In the difference value calculation step, the difference value between the first shape defect value and the second shape defect value calculated in the above steps S100 to S122 is calculated (S126).
In the difference value calculation step, the difference value of each absolute value of the first shape defect value and the second shape defect value is calculated.

In the shape defect occurrence cause analysis method according to the present embodiment, the region for changing the parameter and the parameter are changed in the parameter changing step, molding input data for the number of divided regions is created, and the above-mentioned parameter changing step and the second stress The value calculation step, the second shape defect value calculation step, the shape defect value comparison step, and the difference value calculation step (S118 to S126) are repeated.
That is, the steps S118 to S126 are carried out for all of the divided regions for one or more predetermined parameters. Alternatively, the steps S118 to S126 may be carried out for a specific region of the divided regions for one or more predetermined parameters.

(Process for identifying the cause of shape defects)
In the shape defect factor identification step, the shape defect factor region is specified from the region where the parameter is changed based on the result of the difference value calculation step (S128).

In the shape defect occurrence cause analysis method according to the present embodiment, the second shape defect value is smaller than the first shape defect value based on the results of the shape defect value comparison step and the difference value calculation step in the shape defect factor identification step. Identify the shape defect factor area in the area where the parameters are changed when the difference value becomes the largest.

When the second shape defect value is smaller than the first shape defect value and the difference value between the first shape defect value and the second shape defect value is the largest, the shape defect value, that is, the springback amount of the press-formed product is large. The smallest.
Therefore, the region where the parameter is changed when the second shape defect value is smaller than the first shape defect value and the difference value between the first shape defect value and the second shape defect value is the largest is the most shape defect. It can be specified as an influential shape defect factor site (or region). Such a portion may be referred to as a shape defect factor region. The shape defect factor region may be shown as a region surrounded by a thick line portion c, for example, on a display device as shown in FIG.

Further, the parameter of the region where the parameter is changed when the second shape defect value is smaller than the first shape defect value and the difference value between the first shape defect value and the second shape defect value is the largest is the shape defect. Can be specified as the parameter that most affects. Such a parameter may be referred to as, for example, a shape defect factor parameter.

From the results of the shape defect value comparison step and the difference value calculation step, it is determined that there is no region affecting the shape defect when the second shape defect value is larger than the above-mentioned first shape defect value. .. In this case, the first shape defect value may be set as the minimum shape defect value.

As a display method or an output method of a region that causes a shape defect, for example, a difference value between the first shape defect value and the second shape defect value is given as a numerical value for the region in which the parameter is changed, and Livermore Software Technology Corp. There is a method of displaying using software such as LS-PREPOST manufactured by LS-PREPOST.
FIG. 11 is a diagram showing an example of displaying the cause of shape defect on the screen of the display device. As shown in FIG. 11, for example, the regions that cause shape defects may be color-coded according to the degree of influence on the shape defects for each divided region.

In the example of FIG. 11, it is said that the central side surface portion of the press-formed product 10 is a region having a large influence on the shape defect. Further, both ends of the press-formed product 10 and its vicinity are defined as regions having a small influence on the shape defect.

The order of each step in the shape defect occurrence cause analysis method described in the present embodiment is only an example, and the same analysis method may be carried out by changing the order of each step.

In the shape defect occurrence cause analysis method according to the present embodiment, it is also possible to specify a specific value of the shape defect factor parameter described above. From the results of the shape defect value comparison process and the difference value calculation process, when the second shape defect value is smaller and the difference value is the largest than the first shape defect value, the area and parameter in which the parameter is changed, and this parameter The value of may be specified.
Areas and parameters in which the parameters specified as described above are changed have the greatest effect on shape defects. Therefore, by changing the parameters in this region, the shape defect of the press-formed product can be minimized.

After the shape defect cause analysis method according to the above-described embodiment is performed to identify the shape defect cause, the shape defect occurrence cause analysis method according to the above-described embodiment is further applied to the region specified as the shape defect factor. It may be carried out to further identify the region that causes the shape defect.
In this case, the above-mentioned S100 to S128 are carried out, and the same steps as in S100 to S128 are carried out with respect to the region specified as the cause of the shape defect by further reducing the division region. Thereby, a more detailed cause of shape defect can be identified.

The method for analyzing the cause of shape defects according to the above-described embodiment is preferably used when the work material (blank) has a temperature gradient, that is, when one work material has a temperature distribution immediately before press forming. it can. Further, in the method for analyzing the cause of shape defects according to the above-described embodiment, when the mold used for press forming by the hot stamping method has a temperature gradient, that is, the temperature is distributed to any or all of the dies, punches, and pads. It can also be preferably used when there is. Alternatively, the method for analyzing the cause of shape defects according to the above-described embodiment can be preferably used even when the material to be processed (blank) and the mold have a temperature gradient.

According to the method for analyzing the cause of shape defects according to the above-described embodiment, when a steel material such as a steel plate or a steel bar, a material such as aluminum, magnesium, or titanium, or an alloy thereof is press-formed by a hot stamping method, a press-formed product is produced. It is possible to specify the region of the work material that causes the shape defect that occurs in the above and / or the site and the parameter that causes the shape defect that occurs in the press-formed product.

According to the shape defect occurrence cause analysis method according to the present embodiment, it is possible to identify a portion that is the main cause of the shape defect of the press-formed product by the hot stamping method. In addition, it is possible to identify the parameters that cause the shape defect in the portion that is the main cause of the shape defect.

[Second Embodiment]
The basic configuration of the shape defect occurrence cause analysis method according to the present embodiment is the same as that of the shape defect occurrence cause analysis method according to the first embodiment described above, but in the shape defect factor identification step, the shape defect value comparison step From the results of the difference value calculation process and the result, when the second shape defect value is smaller than the first shape defect value and the second shape defect value is the smallest, the area where the parameters are changed and the parameters are specified as the shape defect factors. To do.

When the second shape defect value is the smallest, the shape defect value, that is, the springback amount of the press-formed product is the smallest.
Therefore, the region in which the parameter is changed when the second shape defect value is the smallest can be specified as the shape defect factor portion (or region) that most affects the shape defect.
Further, the parameter in the region where the parameter when the second shape defect value is the smallest is changed can be specified as the parameter that most affects the shape defect.

From the results of the shape defect value comparison step and the difference value calculation step, it is determined that there is no region affecting the shape defect when the second shape defect value is larger than the above-mentioned first shape defect value. .. In this case, the first shape defect value may be set as the minimum shape defect value.

In the shape defect occurrence cause analysis method according to the present embodiment, parameter values for reducing shape defects can be quantitatively obtained, and if the pressing method is controlled with the parameter as the target, a product with excellent shape accuracy can be obtained. It has the effect of being.

[Third Embodiment]
Next, the shape defect correction method of the present invention will be described. In the shape defect correction method according to the present embodiment, in the transport process from heating the material steel plate of the press-formed product to installation in the mold, or in the press process, the following method for analyzing the cause of shape defect in the press-formed product is used. Partially cool, heat-retain, or heat the specified parameter-changed region, or partially cool, heat-retain, or heat the region other than the parameter-changed region during the manufacturing process. Take measures to reduce the non-uniformity of the temperature distribution near the part that causes the shape defect.

The shape defect correction method according to the present embodiment utilizes a shape defect occurrence cause analysis method of a press-formed product including the following steps.
Press molding analysis is performed by numerical simulation, and the press molding analysis process that calculates the molding data of the press molded product based on the molding conditions of the press molded product, and the molding data of the mold cooled product by mold cooling are calculated by the numerical simulation. The first stress value of the mold cooling product is calculated based on the mold cooling analysis process and the temperature change and strain amount during press molding obtained from the molding data of the press molded product and the molding data of the mold cooling product. 1 The first shape defect value calculation step for calculating the first shape defect value based on the first stress value of the mold cooling product obtained by the first stress value calculation step and the first stress value calculation step, and the press-molded product. Is divided into a plurality of regions and the parameters of each region are changed, and the press molding data obtained from the molding data of the press-formed product and the molding data of the mold cooling product whose parameters are changed in the parameter changing process Based on the second stress value calculation process that calculates the second stress value of the mold cooling product based on the temperature change and the amount of strain, and the second stress value of the mold cooling product obtained by the second stress value calculation process. , The second shape defect value calculation process for calculating the second shape defect value, the shape defect value comparison process for comparing the first shape defect value and the second shape defect value, and the first shape defect value and the second shape defect value. A shape defect factor identification process that identifies a shape defect factor region from a region in which parameters are changed based on the results of a difference value calculation process that calculates a difference value from a value and a difference value calculation process.

In the shape defect correction method according to the present embodiment, the configuration of the shape defect occurrence cause analysis method of the first and second embodiments described above can be adopted.
In this embodiment, a case where a region and a parameter that cause a shape defect are specified in the shape defect factor identification step of the first embodiment described above will be described.

FIG. 12 is a diagram showing an example of displaying the cause of shape defect on the screen of the display device as in FIG. 11.
In the example of FIG. 12, the region where the central side surface portion of the press-formed product 10 has a large influence on the shape defect is shown as a range surrounded by a thick line d. Further, both ends of the press-formed product 10 and its vicinity are shown as a range in which a region having a small influence on the shape defect is surrounded by thick lines e and e'.
It is considered that the stress value increases due to the non-uniformity of the temperature distribution near the site of the cause of the shape defect during the manufacturing process and the non-uniformity of the phase transformation accompanying the unevenness of the temperature distribution, resulting in the shape defect. In the shape defect correction method according to the present embodiment, the shape defect is improved by reducing the non-uniformity of the temperature distribution in the vicinity of the shape defect factor portion.

In the shape defect correction method according to the present embodiment, in order to eliminate the non-uniformity of the temperature distribution in the transport process from heating the material steel plate of the press-formed product to the installation in the die or the press process, the shape is formed. Partially cool, heat-retain, or heat the defect factor region, or partially cool, heat, or heat the region other than the shape defect factor region, and the temperature near the shape defect factor region during the manufacturing process. Take measures to reduce non-uniform distribution.

For example, in FIG. 12, the region indicated by the thick line d is partially cooled. Alternatively, the region indicated by the thick line e or e'is partially kept warm or heated to reduce the non-uniformity of the temperature distribution during the manufacturing process.
Examples of the cooling method include a method of partially increasing the flow rate and directly performing water cooling, a method of partially spraying a refrigerant, and a method of partially cooling the mold using a mold having a high thermal conductivity. Examples of the heating method include a method of irradiating a laser during transportation to heat the mold, a method of partially heating by partially energizing and heating, a method of heating the mold using a mold equipped with a heater, and the like. Examples of the heat retention method include a method of partially covering the material to be processed with a heat insulating cover and transporting the material.

The above-mentioned heating, heat retention, or cooling is performed in a transfer step or a press step from heating the material steel plate of the press-formed product to installing it in the mold.

Further, in the shape defect correction method according to the present embodiment, in the transport process from heating the material steel plate of the press-formed product to installation in the die, or in the press process, the plate thickness or the shape defect of the shape defect factor region The plate thickness of the region other than the factor region may be changed.

By adjusting the plate thickness, the cooling rate of the work material can be controlled, and the temperature non-uniformity in the manufacturing process can be reduced.

The plate thickness of the press-formed product according to the above-described embodiment is 3 mm or less, preferably 1.6 mm or less.

Further, in the shape defect correction method according to the present embodiment, in the pressing process after heating the work material of the press-formed product and then installing it in the mold, the clearance of the mold facing the shape defect factor region or the clearance of the mold, or The clearance of the mold facing the region other than the shape defect factor region may be changed.

Further, in the shape defect correction method according to the present embodiment, in the pressing process after heating the material steel plate of the press-formed product and then installing it in the mold, the thermal conductivity or the shape defect of the mold in the shape defect factor region is performed. The thermal conductivity of the mold may be changed in a region other than the factor region.

Further, in the shape defect correction method according to the present embodiment, in the pressing process after heating the material steel plate of the press-formed product and then installing it in the die, the contact between the work material and the die in the shape defect factor region The contact pressure between the work material and the mold in a region other than the pressure or shape defect factor region may be changed.

From the results of the shape defect value comparison step and the difference value calculation step, it is determined that there is no region affecting the shape defect when the second shape defect value is larger than the above-mentioned first shape defect value. .. In this case, it is not necessary to correct by the shape defect correction method according to the present embodiment.

In the shape defect correction method according to the present embodiment, each configuration of the shape defect occurrence cause analysis method of the first and second embodiments described above can be adopted alone or in combination.

[Fourth Embodiment]
Next, the shape defect occurrence cause analyzer of the present invention will be described.
FIG. 13 is a configuration diagram of a shape defect factor analyzer according to the present embodiment.
As shown in FIG. 13, the shape defect occurrence cause analyzer 400 according to the present embodiment performs press-molding analysis of the press-molded product obtained by the hot stamping method, and based on the molding conditions of the press-molded product, the press-molded product Obtained from the press molding analysis unit 401 that calculates the molding data, the mold cooling analysis unit 402 that calculates the molding data of the mold cooled product by mold cooling, the molding data of the press molding product, and the molding data of the mold cooling product. The first stress value calculation unit (stress value calculation unit 403) that calculates the first stress value of the die cooling product based on the temperature change and strain amount during press forming, and the first stress value calculation unit based on the first stress value. The parameters are changed by the first shape defect value calculation unit (shape defect value calculation unit 404) that calculates the shape defect value, and the parameter change unit 405 that divides the press-formed product into a plurality of regions and changes the parameters of each region. A second stress value calculation unit that calculates the second stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the die-cooled product. The stress value calculation unit 403), the second shape defect value calculation unit (shape defect value calculation unit 404) that calculates the second shape defect value based on the second stress value of the mold cooling product, and the one shape defect value. The shape defect value comparison unit 406 that compares the first shape defect value with the second shape defect value, the difference value calculation unit 407 that calculates the difference value between the first shape defect value and the second shape defect value, and the shape from the area where the parameters are changed. A shape defect factor specifying unit 408 for specifying a defect factor region is provided.

In the example of FIG. 13, the shape defect factor identification unit 408 from the press forming analysis unit 401 described above is included in the arithmetic processing unit 409. Further, in the shape defect factor analysis device according to the present embodiment, the arithmetic processing unit 409 includes an input unit 410, a storage unit 411, and an output unit 412.
The arithmetic processing unit 409 may be a computer including a CPU and a memory. The input unit 410 may be an external storage device, another computer, a measuring device, a keyboard, or the like. The storage unit 411 may be a storage medium such as a hard disk. The output unit 412 may be a display or a printer.

The input unit 410 contains shape data (plate thickness, length, width, curvature, etc.) and properties (chemical components, crystal grains, etc.) of the work material to be analyzed by the press molding analysis unit 401 and the die cooling analysis unit 402, which will be described later. Materials such as diameter, strength, elongation, friction coefficient corresponding to surface condition, etc.), heating temperature and temperature distribution of the work material, mold shape (die (die) and punch shape, curvature, diameter, clearance, lubrication conditions ), Press conditions (wrinkle pressing load, pad load, bead tension, press pressure, temperature, cooling rate) and other molding conditions are input.

The press forming analysis unit 401 uses the forming conditions input by the input unit 410 as input information, and uses the elasto-plastic finite element method, the rigid-plastic finite element method, the one-step finite element method, the boundary element method, the elementary analysis, and the like. Numerical analysis is performed to determine the stress, strain, and plate thickness of a steel plate, which is a press-formed work piece. The press forming analysis unit 401 outputs the numerical analysis result in the form of variables such as the plate thickness of the work piece, the stress component value, the strain component value, and the distribution of the variables. Regarding the calculation of the stress value, data communication is performed between the stress value calculation unit 403 and the press forming analysis unit 401 regarding the state variables related to the temperature, phase fraction, and strain state of the work material, and the thermal expansion strain and phase are calculated. Taking the transformation strain into consideration, assuming a plane stress state, the stress in any strain state and the state variable for each element are calculated by performing the convergence calculation. The output data of the press forming analysis unit 401 is output to the storage unit 411 as, for example, an electronic file "press_post_data.k". “Press_post_data.k” includes updated state variable data of temperature, phase fraction, strain, and stress of the work material.

Numerical analysis by the press forming analysis unit 401 is performed by a finite element method (for example, commercially available software PAM-STAMP, LS-DYNA, Autoform, OPTRIS, ITAS-3D, ASU / P-FORM, ABAQUS, ANSYS, MARC, HYSTAMP, Hyperform, Shape data (plate thickness, length, width, curvature, etc.) of products to be press-molded using SIMEX, Finiteform3D, Quikstam) and properties of the metal plate used (chemical composition, crystal grain size, strength, elongation, etc.) Based on the material, friction coefficient corresponding to the surface condition, etc.), if necessary, mold shape (die and punch shape, curvature, diameter, clearance, lubrication conditions), press conditions by hot stamping method (temperature, pressure) , Cooling rate, heat transfer coefficient), and other molding conditions can be set, molding analysis can be performed, and the distribution of stress and strain values after molding can be obtained numerically.

Further, the press forming analysis unit 401 can display the analysis results such as the stress distribution and the curvature by the finite element method on the output unit 412 by using post processing software.

The mold cooling analysis unit 402 uses the molding conditions input by the input unit 410 and the output data "press_post_data.k" of the press molding analysis unit 401 as input information, and is an elasto-plastic finite element method, a rigid-plastic finite element method, and one step. Using the finite element method, boundary element method, elementary analysis, etc., numerical analysis is performed to determine the stress, strain, and thickness of the steel plate, which is the work piece cooled by the mold. The mold cooling analysis unit 402 outputs numerical analysis results in the form of variables such as the plate thickness of the work piece, stress component values, strain component values, and the distribution of the variables. Regarding the calculation of the stress value, data communication is performed between the stress value calculation unit 403 and the mold cooling analysis unit 402 regarding the state variables related to the temperature, phase fraction, and strain state of the work material, and the thermal expansion strain is calculated. Taking the phase transformation strain into consideration, assuming a plane stress state, the stress in any strain state and the state variable for each element are calculated by performing the convergence calculation. The output data of the mold cooling analysis unit 402 is output to the storage unit 411 as, for example, an electronic file “quench_post_data.k”. “Quench_post_data.k” includes updated state variable data of temperature, phase fraction, strain, and stress of the work material.

The shape defect value calculation unit 404 uses the output data file "press_post_data.k" of the press forming analysis unit 401 or the output data file "quench_post_data.k" of the mold cooling analysis unit 402 as input data to perform springback analysis. Do. The springback analysis is a variable such as the plate thickness of the work piece, the stress component value, and the strain component value, which are the output results of the press forming analysis unit 401, the die cooling analysis unit 402, and the stress value calculation unit 403. And the material is fixed at any constraint point by elastic finite element method, elasto-plastic finite element method, one-step finite element method, elementary analysis, etc. based on the variable distribution data "press_post_data.k" or "quench_post_data.k" Then, the unloading process is calculated, and the amount of springback, which is the amount of deformation that occurs in the workpiece, is numerically analyzed. The amount of springback is calculated for each element of the three-dimensional data coordinates by dividing the workpiece by the finite element method or the like.
The amount of springback, which is a shape defect value that occurs in the work piece, includes the amount of deformation of an arbitrary point of the work piece, the amount of deformation of the maximum or minimum displacement point in the designated area of the work piece, and the work piece. There is an angle formed by a plurality of arbitrary surfaces or lines in the work piece, or a curvature formed by any surface or line of the workpiece.

The output data, which is the springback analysis result of the shape defect value calculation unit 404, includes the springback amount, the shape such as strain after springback, properties, stress, and the like, and is output to the output unit 412. Using the input data file "press_post_data.k" or "quench_post_data.k", the numerical analysis result output data file "SB_post_data.k" is output to the shape defect value comparison unit 406 and the storage unit 411.

When the parameter changing unit 405 acquires the data of the press-formed product, which is one of the workpieces, from the input data, the parameter changing unit 405 performs a process of dividing the data of the press-formed product into a plurality of regions. One of the area division methods is to specify the number of divisions in the width direction and the longitudinal direction according to the local coordinate system of the press-formed product.

When considering division, it is desirable to consider a size that allows countermeasures to be implemented. That is, even if a specific part is found, the analysis result may not be effectively utilized in an extremely small area where effective measures for the specific part cannot be taken. For example, when the countermeasure for a specific part is to add a bead of 20 mm × 100 mm, the divided region may be about 20 mm square.

As one method for determining the divided region of the molded product, there is also a method of determining the divided region based on the curvature and the element.
The press forming analysis unit 401 can obtain the coordinate values of each node as geometric information of the workpiece after the forming analysis by numerical analysis, and objectively calculate the curvature of each element and the angle between the elements. It is possible. In the case of a press-formed product, the deformed workpiece has a very large curvature at the bending ridges such as the punch shoulder R and the die shoulder R in the direction perpendicular to the bending ridge as compared with other parts.

Here, the maximum curvature of each element is calculated, the elements having a curvature above a certain threshold are hidden, and the parts other than the punch shoulder R and the die shoulder R (web surface, vertical wall part, flange part) are set as separate areas. By dividing the region and dividing the punch shoulder R and the die shoulder R portion in the longitudinal direction of the member, it is possible to analyze the degree of contribution of each portion to the shape defect.

The shape defect value comparison unit 406 compares the first shape defect value and the second shape defect value at the evaluation points, and verifies the effect of the shape defect countermeasure by changing the parameters for each divided portion.

The difference value calculation unit 407 calculates the difference value between the first shape defect value at the evaluation point and each second shape defect value obtained by changing the parameter.

The shape defect factor identification unit 408 visualizes the degree of improvement in shape due to the parameter change by mapping the above difference value for each divided region in which the parameter on the press-formed product is changed, and the shape of the press-formed product. Identify the defect factor area.
When the second shape defect value is smaller and the second shape defect value is the smallest than the first shape defect value calculated by the shape defect value calculation unit 404 described above, or the first shape defect factor identification unit 408 is used. When the second shape defect value is smaller than the shape defect value and the difference value is the largest, the region in which the parameter is changed is specified as the shape defect main cause portion.

The shape defect factor is output to the output unit 412.

[Fifth Embodiment]
Next, a program of the present invention for analyzing the cause of shape defects in a press-formed product will be described.
The program for analyzing the cause of the shape defect of the press-formed product according to the present embodiment is a program for analyzing the cause of the shape defect of the press-formed product obtained by the hot stamping method. The program performs press molding analysis by numerical simulation and calculates molding data of the press molded product based on the molding conditions of the press molded product, and by numerical simulation, the molding data of the mold cooled product by die cooling is obtained. The process of calculating, the process of calculating the first stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the die-cooled product, and the mold. A process of calculating the first shape defect value based on the first stress value of the die-cooled product, a process of dividing the press-formed product into a plurality of regions and changing the parameters of each region, and a press having the parameters changed. A process of calculating the second stress value of the mold cooling product based on the temperature change and strain amount during press molding obtained from the molding data of the molded product and the molding data of the mold cooling product, and the second of the mold cooling product. The process of calculating the second shape defect value based on the stress value, the process of comparing the first shape defect value and the second shape defect value, and the difference value between the first shape defect value and the second shape defect value. This is a program for causing a computer to execute a process of calculating a shape defect and a process of identifying a shape defect cause region from a region in which a parameter is changed.

The above program may be stored on a computer-readable recording medium. The recording medium may be a non-transient recording medium such as a hard disk, a memory device, or a general recording medium.
Further, the program according to the present embodiment may be stored in the storage unit 411 of the device described in the fourth embodiment.

[Example]
Hereinafter, examples of the method for analyzing the cause of shape defects according to the present invention will be described.
In the examples, Livermore Software Technology Corp. Using the analysis software LS-DYNA manufactured by LS-DYNA, after heating in a furnace at 900 ° C., using a steel plate for hot stamping with a plate thickness of 1 mm under the condition of low-speed transportation, a long part with a hat cross-sectional shape shown in FIG. 14 is manufactured by hot stamping. The shape defect at the time of making was calculated. The heating temperature of the work piece was 900 ° C., the molding start temperature was about 600 ° C., and the average cooling rate by the mold was 40 ° C./s.

FIG. 14 shows a contour diagram showing the degree of influence on the shape defect of the press-formed product output by the shape defect occurrence cause analysis method according to the present invention.
According to FIG. 14, a region in which the central side surface portion of the press-formed product 10 has a large influence on the shape defect is shown as a range (A portion) surrounded by a thick line A. Further, both ends of the press-formed product 10 and its vicinity are shown as ranges (parts B and C) in which regions having a small influence on shape defects are surrounded by thick lines B and C.

Table 1 shows the results of taking measures such as heating and cooling for parts A to C.
The reference example in Table 1 is an example when no measures are taken.
The amount of separation from the product shape at the evaluation point in the z direction is a dimensional value that is separated from the drawing of the evaluation point of the manufactured part (press-formed product) in the z direction. The smaller this value is, the less the shape defect is, and the better the dimensional accuracy is.

According to the results in Table 1, it can be seen that the amount of separation of the press-molded product from the product shape at the evaluation point in the z-direction is reduced by taking measures for parts A to C during the transfer process or press molding. ..

The effect of the countermeasure is determined by the degree of influence, the area, and the parameter adjustment effect of the countermeasure. For example, in Example 5, measures are taken for a region (range of thick lines B and C) having a small influence on the shape defect, but the target area is wide and the temperature distribution of that portion can be efficiently eliminated. .. Therefore, the amount of separation is smaller than that in the case of Example 1 in which countermeasures are taken for a region (range of thick line A) having a large influence on shape defects.

According to the shape defect occurrence cause analysis method, the shape defect correction method, the shape defect occurrence cause analysis device, the program for analyzing the shape defect occurrence cause, and the recording medium according to the present invention, the shape defect of the press-formed product by the hot stamping method. It is extremely useful in industry because it is possible to identify the part that is the main cause of the occurrence of the shape defect and to propose a correction method for the part that is identified as the main cause of the shape defect.

Claims (11)

This is a method for analyzing the cause of shape defects in press-formed products.
A press molding analysis process that performs press molding analysis by numerical simulation and calculates molding data for the press molded product based on the molding conditions of the press molded product.
A mold cooling analysis process that calculates molding data for mold cooling products by mold cooling by numerical simulation,
First stress value calculation step for calculating the first stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the mold-cooled product. When,
A first shape defect value calculation step for calculating a first shape defect value based on the first stress value of the mold cooling product obtained by the first stress value calculation step, and a first shape defect value calculation step.
A parameter change process that divides the press-formed product into multiple regions and changes the parameters of each region,
The second stress value of the die-cooled product is based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the mold-cooled product whose parameters are changed in the parameter changing step. The second stress value calculation process to calculate
A second shape defect value calculation step for calculating a second shape defect value based on the second stress value of the mold cooling product obtained by the second stress value calculation step, and a second shape defect value calculation step.
A shape defect value comparison step for comparing the first shape defect value and the second shape defect value, and
A difference value calculation step for calculating a difference value between the first shape defect value and the second shape defect value, and
Based on the result of the difference value calculation step, the shape defect factor identification step of specifying the shape defect factor region from the region where the parameter is changed, and the shape defect factor identification step.
A method for analyzing the cause of shape defects, which comprises. In the parameter changing step, the area where the parameter is changed and the parameter are changed.
The parameter changing step, the second stress value calculation step, the second shape defect value calculation step, the shape defect value comparison step, and the difference value calculation step are repeated.
In the shape defect value comparison step and the difference value calculation step, when the second shape defect value is smaller than the first shape defect value and the second shape defect value is the smallest, or when the first shape defect value is the smallest. The shape defect occurrence according to claim 1, wherein a region in which the parameter is changed is specified as a shape defect factor region when the second shape defect value is smaller than the value and the difference value is the largest. Cause analysis method. The parameters are selected from the group consisting of temperature, plate thickness, thermal conductivity, stress component value, strain component value, coefficient of thermal expansion, transformation plasticity coefficient, specific heat, and chemical component of the work material of the press-formed product. The method for analyzing the cause of shape defect according to claim 1 or 2, wherein the number of types is one or more. In the transfer process or press process from heating the work material of the press-formed product to installing it in the die.
A shape defect characterized by partially cooling, keeping warm, or heating the shape defect factor region identified by the shape defect occurrence cause analysis method according to any one of claims 1 to 3. How to fix. In the transfer process or press process from heating the work material of the press-formed product to installing it in the die.
It is characterized in that a region other than the shape defect factor region specified by the shape defect occurrence cause analysis method according to any one of claims 1 to 3 is partially heated, kept warm or cooled. How to fix shape defects. In the transfer process or press process from heating the work material of the press-formed product to installing it in the die.
Changing the plate thickness of the shape defect factor region or the plate thickness of the region other than the shape defect factor region specified by the shape defect occurrence cause analysis method according to any one of claims 1 to 3. A characteristic shape defect correction method. In the press process after heating the work material of the press-formed product and then installing it in the die.
The clearance of the mold facing the shape defect factor region or the mold facing the region other than the shape defect factor region identified by the shape defect occurrence cause analysis method according to any one of claims 1 to 3. A shape defect correction method characterized by changing the mold clearance. A press molding analysis unit that performs press molding analysis of a press-molded product and calculates molding data of the press-molded product based on the molding conditions of the press-molded product.
A mold cooling analysis unit that calculates molding data for mold cooling products by mold cooling,
A first stress value calculation unit that calculates the first stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the mold-cooled product. When,
A first shape defect value calculation unit that calculates a first shape defect value based on the first stress value,
A parameter change section that divides the press-formed product into multiple regions and changes the parameters of each region,
A second stress that calculates the second stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product whose parameters have been changed and the molding data of the mold-cooled product. Value calculation unit and
A second shape defect value calculation unit that calculates a second shape defect value based on the second stress value of the mold cooling product, and
A shape defect value comparison unit that compares the first shape defect value with the second shape defect value,
A difference value calculation unit that calculates a difference value between the first shape defect value and the second shape defect value,
A shape defect factor identification part that identifies a shape defect factor region from the region where the parameters are changed,
A shape defect occurrence cause analyzer characterized by being provided with. The shape defect factor identification part
When the second shape defect value is smaller than the first shape defect value and the second shape defect value is the smallest, or when the second shape defect value is smaller than the first shape defect value and the difference is The shape defect occurrence cause analyzer according to claim 8, wherein the region in which the parameter is changed and the parameter are configured to be specified as a shape defect factor when the value becomes the largest. This is a program for analyzing the causes of shape defects in press-formed products.
Press molding analysis is performed by numerical simulation, and molding data of the press molded product is calculated based on the molding conditions of the press molded product.
Processing to calculate molding data of mold cooled products by mold cooling by numerical simulation,
A process of calculating the first stress value of the die-cooled product based on the temperature change and strain amount during press molding obtained from the molding data of the press-molded product and the molding data of the mold-cooled product.
A process of calculating the first shape defect value based on the first stress value of the mold cooling product, and
The process of dividing the press-formed product into multiple regions and changing the parameters of each region,
A process of calculating the second stress value of the die-cooled product based on the temperature change and strain amount at the time of press molding obtained from the molding data of the press-molded product in which the parameters are changed and the molding data of the mold-cooled product. ,
A process of calculating a second shape defect value based on the second stress value of the mold cooling product, and
The process of comparing the first shape defect value with the second shape defect value and
The process of calculating the difference value between the first shape defect value and the second shape defect value, and
The process of identifying the shape defect factor region from the region where the parameters are changed, and
A program that lets your computer run. A computer-readable recording medium containing the program according to claim 10.