JP7501487B2 - Molding analysis method and program - Google Patents

Description

The present invention relates to a forming analysis method that uses a computer to perform forming analysis of the behavior of a workpiece when bending the outer periphery of the workpiece that has a surface shape. The present invention is a technology suitable for forming analysis of press forming, for example, when manufacturing exterior panels that form the exterior of an automobile, in which the outer periphery of a panel part that has a predetermined shape (design) given to its surface is bent to form a flange part that serves as a joint with another part.

As mentioned above, the present invention analyzes bending forming of a workpiece that has been given a specific surface shape (design) by an upstream pressing process.

Traditionally, when manufacturing the parts that make up an automobile, forming analysis using the finite element method, such as FEM, is widely carried out before the actual parts are manufactured. Such parts include exterior panels (panel parts) such as doors and roofs, and the shape accuracy of these is also confirmed in advance using forming analysis.

There are two methods of analysis for forming analysis using FEM: the dynamic explicit method and the static implicit method. When the dynamic explicit method is used for forming analysis of an outer panel, vibrations occur in the workpiece (panel part) during forming analysis, and the effects of the vibrations may remain on the workpiece until it reaches the bottom dead center of forming.
Outer panels are automotive parts for which the surface design is particularly important, and the above-mentioned vibrations that occur during analysis are a phenomenon that must be eliminated in order to determine the panel's design.

For example, although it is not a patent for suppressing vibration, as in Patent Document 1, there is an analysis method that applies acceleration to an analytical model of the exterior panel of an automobile opening/closing part, simulating the state of the automobile opening/closing part at the moment it is closed, and uses that vibration to predict the reversal phenomenon in which the direction of curvature of the exterior panel changes.

JP 2016-218785 A

The analysis method described in Patent Document 1 aims to predict the curvature reversal phenomenon by utilizing the vibration of the outer panel, and is not effective in suppressing the vibration that occurs during forming analysis.

In forming analysis, investigations and identification of friction coefficients, forming speeds, and cushion pressures are frequently performed to predict shapes with high accuracy in press forming, which gives shapes to surfaces. However, until now, there have been few examples of analyzing workpieces after a design (surface shape) has been added, and working on improving accuracy when bending the outer periphery to form a flange. As a result, there have been no studies of analysis methods for bending the outer periphery of a panel to form a flange.

In addition, in the actual press forming process of an outer panel, for example, press forming is performed to apply a design to the surface of the outer panel. In the subsequent process, unnecessary peripheral excess material is trimmed and a flange is formed by bending the outer periphery of the panel to form a joint with another part. In order to prevent damage to the design surface when bending to form the flange, in the actual press process, the bending to form the flange is performed with only the vicinity of the flange (the outer periphery of the panel) pressed with a pad, without pressing the area of the design surface with a pad. For this reason, it is generally assumed that forming analysis of bending to form a flange on the outer periphery of a workpiece is performed under forming conditions such as, for example, holding and restraining the vicinity of the flange with a lower die and pads for a workpiece with a design formed on its surface, and bending the end of the workpiece with a lower die and bending blade (see Figure 3).

However, this type of bending analysis for forming the flange had a negative impact on the evaluation of the surface shape (design) that had already been formed.

The present invention was made with the above in mind, and aims to provide a method that allows for more accurate forming analysis of the behavior of a workpiece when the workpiece, which has a shape (design) applied to its surface, is bent.

The inventors conducted various studies on forming analysis of bending the outer periphery of an exterior panel to form a flange, with an exterior panel having a design (such as a door shape) applied to its surface by press forming as the evaluation subject. As a result of their studies, they noticed a problem that the analysis of bending to form a flange changes the surface shape applied to the surface, resulting in a poor evaluation of the design of the surface shape. Specifically, they noticed that the design would be destroyed.

The inventors conducted various investigations into the reasons for this and discovered that this is because vibrations occur during bending analysis, and as the bending progresses, these vibrations propagate to the design surface that is not in the forming area, and the vibrations may remain until the forming bottom dead center is reached.
The present invention has been made based on the above findings.

In other words, in order to solve the problem, one aspect of the present invention is a forming analysis method that analyzes press forming in which a plate-shaped workpiece having a shape imparted to its surface by press forming is used as an analysis target, and at least a portion of the outer periphery surrounding the area of the surface of the workpiece to which the shape has been imparted is bent to form a flange portion, and the bending conditions are set to perform the bending using a lower die having a surface that can face the lower surface of the workpiece and a bending blade, and a condition is set that during the bending, a pressure is applied to press at least the area of the workpiece surface to which the shape has been imparted, on the upper surface of the workpiece, toward the lower die, excluding the flange portion that is plastically deformed by the bending.

In one aspect of the present invention, when analyzing the bending of the outer periphery of a plate-shaped workpiece, which has a shape (hereinafter also referred to as a design) given to its surface by press forming, to form a flange, the analysis is performed under the condition that a pressure is applied that constrains at least the area of the design shape. As a result, according to this aspect of the present invention, vibrations of the workpiece, which occur from the analysis of bending to form the flange, to the end of the analysis, particularly vibrations transmitted to the area given the design (area that is not the forming area), are suppressed, making it possible to suppress adverse effects on the surface shape (design).

FIG. 2 is a diagram illustrating a processing configuration. FIG. 4 is a diagram showing analysis conditions for bending according to an embodiment of the present invention. FIG. 13 is a diagram showing analysis conditions for bending in Comparative Example 1. FIG. 11 is a diagram showing a surface shape of a panel component before molding analysis in an embodiment. FIG. 13 is a diagram showing an example of a surface shape (shape at bottom dead center) after analysis in Comparative Example 1. FIG. 13 is a diagram showing an example of a surface shape (shape at bottom dead center) after analysis in Example 1.

Next, an embodiment of the present invention will be described with reference to the drawings.
The workpiece to be analyzed in this embodiment is a plate-shaped workpiece having a design shape applied to its surface. This embodiment assumes that when an outer panel for an automobile is manufactured, press molding for manufacturing the outer panel is evaluated by molding analysis.

The bending forming analysis using a computer in this embodiment is a CAE analysis using the finite element method. As in the conventional analysis method, the software (program) includes CAD software 100 and analysis software 110 (preprocessor 110A, solver 110B, and postprocessor 110C) as shown in FIG. 1. Publicly known software may be used as the CAD software 100 and analysis software 110. The analysis software 110 corresponds to the analysis program of this disclosure.

CAD software 100 sets the shape data information and physical property information (material information) of the workpiece to be press molded based on the input information.

The shape data of the workpiece may be, for example, the shape data resulting from forming analysis of the press forming process that adds a design to the workpiece surface in the previous process. Or, data on the design designed to be added to the exterior panel may be used.

The preprocessor 110A creates an analytical model (FEM model) of the workpiece to be analyzed from the above-mentioned shape data information, mesh creation conditions, physical property definition (material definition), boundary conditions, constraint conditions (fixing method), load conditions, and other analysis conditions.

Solver 110B performs an analysis of the set analysis model (shape model for FEM analysis) under the set bending conditions. The analysis using the finite element method can be either an implicit or explicit method, but from the perspective of the time required for the analysis, a dynamic explicit method is preferable.

"Analysis conditions for bending"
As shown in FIG. 2, the bending conditions are set so that the outer periphery of the workpiece 1 is bent using a lower die 3 having a surface capable of facing the lower surface of the workpiece 1 and bending blades 4 to 7.
The upper surface of the lower die 3 has a shape following the back surface (lower surface) of the workpiece 1. In other words, the upper surface of the lower die 3 has a shape following the design given to the workpiece 1.

The process under analysis is the process of bending the outer periphery of the workpiece 1 using the end face of the lower die 3 and bending blades 4 to 7 to form a flange portion.

"Other analysis conditions for bending"
In this embodiment, further, condition 2 is added in which a pressure P is applied to press at least the entire area A1 of the surface of the workpiece 1 to which the above-mentioned shape is imparted, toward the lower mold 3, excluding the flange portion which is subjected to plastic deformation by bending.

Specifically, condition 2 is applied to apply pressure P that restrains the surface of workpiece 1 to the entire surface on the inner circumferential side of the region that will become the flange portion.
The direction of pressure P may be a direction perpendicular to the surface of the work 1, or may be the moving direction (press direction) of the bending blades 4 to 7. It is preferable to apply pressure P in a direction perpendicular to the surface of the work 1, which is perpendicular to the entire surface of the design given to the work 1.

Condition 2 for pressure P may be such that pressure P is applied to at least the area of the surface of the workpiece 1 to which the design is applied, excluding the flange portion. However, for simplicity, it is preferable that pressure P is applied to the entire surface on the inner side of the area that will become the flange portion.

It is also preferable that the pressure P to be applied is constant and uniformly distributed over the area to which the pressure P is applied.
The magnitude of the pressure P is set to a pressure capable of restraining the surface of the workpiece 1 and within the elastic region of the workpiece 1. The pressure P is set to, for example, 1 Pa. However, the pressure P applied to the region near the flange portion may be set relatively small to make it easier for the material to flow toward the flange portion.

The post-processor 110C performs processing to display the analysis results of the behavior of the workpiece 1 analyzed by the solver 110B. For example, the post-processor 110C performs processing to display the stress distribution and surface deformation occurring in the constrained workpiece 1 using a three-dimensional model.

The above molding analysis is performed by the analysis program 110.
The analysis program 110 is a program that is called up by a computer and executes a forming analysis process in which a plate-shaped workpiece 1 having a surface shaped by press molding is analyzed, and a flange portion is formed by bending at least a portion of the outer periphery surrounding the area of the surface of the workpiece 1 to which the above-mentioned shape has been imparted.

In the analysis program 110 of this embodiment, the bending conditions are set to bending conditions in which the workpiece 1 is bent using a lower die 3 having a surface that can face the lower surface of the workpiece 1 and bending blades 4 to 7. In addition, condition 2 is set to apply and restrain pressure P that presses at least the area of the surface of the workpiece 1 to which the above-mentioned shape has been imparted on the upper surface of the workpiece 1 toward the lower die 3, excluding the flange portion that is plastically deformed by bending. The pressure P may be of a magnitude that is large enough to restrain the surface of the workpiece 1 without plastically deforming it.

In line with the actual bending process, a bending condition may be added in which the area near the bend is restrained by the lower die 3 and upper pad (not shown); however, since the workpiece 1 is restrained by applying pressure P to the top surface of the workpiece 1, the condition of restraining the area near the bend with the lower die 3 and upper pad may not be necessary.

(Action etc.)
Here, it is assumed that bending conditions are set as shown in FIG. 3 (comparative example).
3, the analysis conditions for bending are set as die conditions including a lower die 13 whose upper surface is shaped to conform to the surface of the workpiece 11, a frame-shaped upper pad 12 that faces the outer periphery of the lower die 13, and bending blades 14 to 17 for bending the workpiece 11. The forming conditions are such that, with the outer periphery of the workpiece 11 (a position in the vicinity of the region that will become the flange portion) held by the lower die 13 and the upper pad 12, the outer periphery of the workpiece 11 is bent by the bending blades 14 to 17 to form the flange portion.

When bending analysis is performed under the bending conditions shown in Figure 3, the vibrations generated during bending analysis propagate to the surface of the workpiece 11 that is on the inner side of the gripping position, causing the ungripped area A1 of the workpiece 11 (the surface on which the design is formed) to vibrate during analysis. Due to the vibrations propagated during the analysis, the shape of the design applied in advance may be distorted on surface A1 of the workpiece 1, even though it is not in the bending area, and input distortion that affects the surface shape may remain.

For this reason, if a forming analysis of the press forming to impart a design is followed by a forming analysis of the bending to form the flange, there is a risk that the design of the exterior press part will be judged as NG in the forming analysis, even if no problems arise with the actual part when evaluating the surface shape of the final exterior press part.

In contrast, in this embodiment, the bending analysis is performed by applying pressure P to at least the surface area A1 to which the design is applied, thereby imposing a condition that constrains the workpiece 1. As a result, the vibrations that occur during bending analysis are prevented from being propagated to the surface area to which the design is applied. As a result, it is possible to prevent unnecessary changes in the surface A1 to which the design is applied during the forming analysis.

As a result, according to this embodiment, vibrations of the workpiece 1, particularly vibrations transmitted to the area to which the design is applied, that occur from the time of analysis of the bending process to form the flange portion until the end of the analysis are suppressed, making it possible to suppress adverse effects on the applied design during analysis.

In addition, when setting the pressure load conditions in this embodiment, the frame-shaped upper pad 12 as described above is not required regardless of the shape of the workpiece 1. This has the effect of reducing data and shortening analysis time in molding analysis.
(Example)

[Comparative Example]
In the above forming analysis, the bottom dead center shape during bending is shown in Figure 5 when forming analysis is performed on the workpiece shown in Figure 4 (only the design surface is shown) under the bending forming conditions (mold conditions) shown in Figure 3. Figure 5 shows the shape as viewed from above (Figure 5(a)) and the shape on the A-B cross section (Figure 5(b)). During the bending analysis, vibrations were continuously propagated to the design part, so the surface shape gradually changed due to each vibration.

As can be seen from Figure 5, in this comparative example, vibrations during analysis remained more noticeable on the inner side (surface area not gripped by the upper pad) than on the outer side. As a result, it was found that there were cases where molding analysis was not performed satisfactorily from the standpoint of design.

[Example]
In contrast, for the workpiece shown in Fig. 4 (only the design surface portion is shown), forming analysis was performed under the same forming analysis conditions as in the comparative example, except that the forming conditions for bending were set to the configuration in Fig. 2 based on the embodiment. That is, forming analysis was performed under condition 2 in which the upper pad 12 was omitted and a pressure P of 1 Pa was applied with an equal pressure distribution to the surface of the workpiece 1 placed on the lower die 3. The bottom dead center shape during bending at that time is shown in Fig. 6. Fig. 6 shows the shape when viewed from above (Fig. 6(a)) and the shape in the C-D cross section (Fig. 6(b)).

As can be seen from Figure 6, in the embodiment, the vibrations over the entire work surface were suppressed by the pressure load, and good results were obtained in that molding analysis was possible without compromising the design.

(others)
The present disclosure may also have the following configuration.
(1) A forming analysis method for analyzing press forming in which a plate-shaped workpiece having a surface shaped by press forming is analyzed, and at least a part of an outer periphery surrounding the surface area of the workpiece to which the shape is imparted is bent to form a flange portion, the method comprising the steps of:
As the bending, forming conditions are set to execute bending using a lower die having a surface capable of facing the lower surface of the workpiece and a bending blade,
During the bending process, a condition is imposed that pressure is applied to press at least the area of the workpiece surface to which the shape is imparted on the upper surface of the workpiece, excluding the flange portion that is subjected to plastic deformation during the bending process, toward the lower die.
(2) The area to which the pressure is applied is the entire surface on the inner circumferential side of the flange portion.
(3) The magnitude of the pressure is set to a pressure capable of restraining the workpiece and within the elastic range of the workpiece.
(4) The pressure applied to the workpiece is constant and uniformly distributed.
(5) This analysis assumes press molding for manufacturing exterior panels for automobiles.
(6) A program for causing a computer to execute a forming analysis process for performing a forming analysis of a press forming process in which a plate-shaped workpiece having a surface shaped by press forming is used as an analysis target, and a flange portion is formed by bending at least a part of an outer periphery surrounding the area of the surface of the workpiece to which the shape is given,
The bending conditions are set so that the workpiece is bent using a lower die having a surface that can face the lower surface of the workpiece and a bending blade,
During the bending process, conditions are set to apply pressure to restrain at least the area of the workpiece surface on the upper surface to which the shape is imparted, excluding the flange portion which is subjected to plastic deformation during the bending process, toward the lower die.

1 Workpiece 2 Condition 3 Lower die 4-7 Bending blade 100 CAD software 110 Analysis software (analysis program)
110A Pre-processor 110B Solver 110C Post-processor A1 Designed area P Pressure

Claims (5)

A forming analysis method for analyzing press forming in which a plate-shaped workpiece having a surface shaped by press forming is analyzed, and a flange portion is formed by bending at least a part of an outer periphery surrounding the surface area of the workpiece to which the shape is imparted,
As the bending, a forming condition is set to execute the bending using a lower die having a surface capable of facing the lower surface of the workpiece and a bending blade,
During the bending, a condition is imposed that a pressure is applied to press at least the area of the surface of the workpiece to which the shape is imparted, on the upper surface of the workpiece, toward the lower die, except for the flange portion to which plastic deformation is applied during the bending ;
The magnitude of the pressure is set to a pressure capable of restraining the workpiece and within the elastic range of the workpiece.
A molding analysis method comprising: The region to which the pressure is applied is the entire surface on the inner circumferential side of the flange portion.
2. The molding analysis method according to claim 1 . 3. The forming analysis method according to claim 1 , wherein the pressure applied to the workpiece is constant and has an equal pressure distribution. The forming analysis method according to any one of claims 1 to 3 , characterized in that the analysis is performed assuming press forming for manufacturing an outer panel for an automobile. A program for causing a computer to execute a forming analysis process for performing a forming analysis of a press forming process in which a plate-shaped workpiece having a surface shaped by press forming is analyzed, and a flange portion is formed by bending at least a part of an outer periphery surrounding the surface area of the workpiece to which the shape is given,
The bending is performed by a lower die having a surface that can face the lower surface of the workpiece and a bending blade.
During the bending process, a condition is set in which a pressure is applied to press at least the area of the surface of the workpiece to which the shape is imparted, on the upper surface of the workpiece, toward the lower die, to restrain the workpiece , except for the flange portion to which plastic deformation is applied during the bending process;
The magnitude of the pressure is set to a pressure capable of restraining the workpiece and within the elastic range of the workpiece.
A program characterized by:

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