Press forming analysis method and press forming product manufacturing method

Abstract

To provide a press molding analysis method in which analysis accuracy in analyzing press molding of a press molded product having a thickness increased part whose thickness is increased by press molding is improved, and a manufacturing method for a press molded product that in which dimensional accuracy of a press molded product is improved.SOLUTION: In a press molding analysis method according to the present invention, consideration is given to elastic deformation of a metal mold in analyzing press molding of a press molded product 110 having a bent shoulder part 115 whose thickness increases during press molding, and a metal mold model 10 that is used in analyzing the press molding has a site of an elastic body where the bent shoulder part 115 is molded, which is modeled by one or more layers of elastic solid elements, and a site of a rigid body where a part other than the bent shoulder part 115 is molded, which is modeled by a rigid shell element, where nodal points of site of the elastic body and of the site of the rigid body are rigidly coupled to each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a press-forming analysis method for a press-formed product having a plate thickness increasing portion whose plate thickness increases due to press forming, and a manufacturing method for the press-formed product. [Background technology]

[0002] The majority of automobile body parts are manufactured by press forming of sheet metal. The press formability of body parts varies depending on the part shape and is also greatly influenced by material properties such as the ductility of the sheet metal. In recent years, the demand for lighter car bodies has led to the use of stronger sheet steel for body parts. However, as the strength of sheet metal increases, springback increases, making it necessary to improve the dimensional accuracy of press-formed parts.

[0003] To reduce the number of trial steps required to manufacture dies used in press forming of auto body parts, advance predictions are made using press forming analysis using the finite element method (FEM).However, the accuracy of press forming analysis is deteriorating due to the increase in springback that accompanies the increased strength of thin metal sheets.

[0004] Furthermore, as the material strength of the sheet metal increases, the reaction force that the die receives from the sheet metal during press forming also increases. Therefore, in reality, the die also undergoes very slight elastic deformation, and the amount of elastic deformation of the die increases as the material strength of the sheet metal increases. However, in normal press forming analyses, the die is often treated as a rigid body that does not deform at all in order to reduce the analysis load. Therefore, it is thought that the elastic deformation of the die is one of the causes of the deterioration of press forming analysis accuracy.

[0005] Therefore, as a press forming analysis that takes into account the elastic deformation of the die, Patent Document 1 proposes a method of modeling the die as an elastic solid model that has a predetermined thickness from the blank contact surface (die surface) that comes into contact with the blank. This method is said to be able to obtain highly accurate results that closely match the material inflow in an actual press by representing the elastic deformation of the die surface in forming analysis of shapes that involve local increases and decreases in thickness at flange portions, such as curved hat materials. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5795151 Summary of the Invention [Problem to be solved by the invention]

[0007] Although the method of Patent Document 1 can improve analysis accuracy, it has the problem of significantly increasing the analysis load because it uses elastic solid elements to model the die and take elastic deformation into account. Potential solutions to suppress the increase in analysis load include reducing the thickness of the parts modeled with elastic solid elements or increasing the size of the elastic solid elements, but these methods result in reduced analysis accuracy. Therefore, in order to perform realistic and highly accurate press forming analysis at the size of mass-produced parts, it is necessary to appropriately model the die while considering the balance between analysis load and analysis accuracy.

[0008] The present invention has been made to solve the above-mentioned problems, and aims to provide a press forming analysis method for performing press forming analysis by modeling a die so as to improve analysis accuracy while suppressing an increase in analysis load. Furthermore, it is an object of the present invention to provide a method for manufacturing a press-molded product, in which a die is designed and manufactured to improve the dimensional accuracy of the press-molded product by the press molding analysis according to the present invention. [Means for solving the problem]

[0009] (1) A press forming analysis method according to the present invention considers elastic deformation of a die in a press forming analysis of a press-formed product having a plate thickness increasing portion in which the plate thickness increases during press forming, The die model used in the press forming analysis is an elastic body portion that forms the plate thickness increased portion and is modeled using one or more layers of elastic body solid elements; A rigid portion that forms a portion other than the plate thickness increasing portion and is modeled by a rigid shell element, The elastic member and the rigid member are rigidly connected at their joints.

[0010] (2) In the above (1), The increased thickness portion is a bent shoulder portion formed by foam molding.

[0011] (3) The manufacturing method of the press-formed product according to the present invention manufactures a press-formed product having a plate thickness increasing portion in which the plate thickness is increased by press forming, a surface pressure calculation step of performing a press forming analysis of the press-formed product using a die model in which the entire die is modeled using rigid shell elements, and calculating the surface pressure of the plate thickness increased portion; a surface pressure measuring step of measuring a surface pressure of the increased plate thickness portion when the press-formed product is actually press-formed; a press-forming analysis step of comparing the surface pressure of the plate thickness increased portion calculated in the surface pressure calculation step with the surface pressure actually measured in the surface pressure actual measurement step, and performing a press-forming analysis of the press-formed product by the press-forming analysis method described in (1) above when the calculated surface pressure is 1.5 times or more the measured surface pressure; an actual die design and manufacturing process for designing and manufacturing a die to be used in press molding of the press-molded product based on the analysis results obtained in the press molding analysis process; and a press molding step of press-molding the press-molded product using the mold thus prepared. [Effects of the Invention]

[0012] In the present invention, a mold model is used that has an elastic portion where the portion that forms the thickened portion is modeled with elastic solid elements, and a rigid portion where the portion that forms the portion other than the thickened portion is modeled with rigid shell elements, and the nodes at the connection points between the elastic portion and the rigid portion are rigidly connected. This makes it possible to take into account the elastic deformation of the mold that occurs when the thickened portion is strongly pressed down at the bottom dead center of forming, and improves the analysis accuracy while suppressing the increase in analysis load that would be caused by using elastic solid elements.

[0013] Furthermore, according to the present invention, by designing and manufacturing a mold to improve the dimensional accuracy of a press-formed product having a plate thickness increasing portion where the plate thickness increases by press forming, it is possible to manufacture a press-formed product with improved dimensional accuracy. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing a die model used in a press-molding analysis method according to a first embodiment of the present invention. FIG. [Figure 2] 1 is a diagram showing an example of a press-molded product having a U-shaped cross section that is an object to be molded in the present invention. FIG. [Figure 3] 1 is a diagram showing a cross-sectional shape of a blank during press-forming of a forming target and a press-formed product in the present invention. FIG. [Figure 4] 10 is a flowchart showing a process flow of a press molding method according to a second embodiment of the present invention. [Figure 5-1] FIG. 10 is a diagram showing a conventional mold model in which the entire mold is modeled using rigid shell elements in the second embodiment and examples of the present invention (conventional example 1). [Figure 5-2] FIG. 10 is a diagram showing rigid body connection points between a punch shoulder and a die shoulder modeled with elastic solid elements in an embodiment. [Figure 6]FIG. 10 is a diagram showing a conventional mold model in which the entire mold is modeled using elastic solid elements in the embodiment (conventional example 2). [Figure 7] 10 is a graph comparing the surface pressure of the bend shoulder of a press-formed product at the bottom dead center of forming, which was obtained by press forming analysis using each die model in the examples. [Figure 8] FIG. 10 is a graph showing the wall opening amount of a press-formed product after springback obtained by press forming analysis using each mold model in the examples, and is a diagram explaining how to obtain the wall opening amount. [Figure 9] 10 is a graph comparing analysis times for press molding analysis using each die model in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0015] Before describing the first and second embodiments of the present invention, the background to the invention will be explained. Note that the dimensions and other specific values ​​shown in the specification and drawings are merely examples to facilitate understanding of the present invention and do not limit the present invention.

[0016] <Background to the invention> The inventors have conducted extensive research into specific methods for modeling a die and performing press forming analysis so as to improve the accuracy of analysis while suppressing an increase in the analysis load.

[0017] In this study, the inventors noticed that when a press-formed product having a thickness-increasing portion whose thickness increases during press forming is crushed to the thickness of the target shape at the bottom dead center of forming, the thickness-increasing portion is subjected to strong pressure from the die. They then found that when the thickness-increasing portion is subjected to strong pressure, the portion of the die that forms the thickness-increasing portion elastically deforms as a reaction force, which has a significant impact on the dimensional accuracy of the press-formed product.

[0018] Here, the increased thickness portion is a region where the wire length of the material in the material flow direction is temporarily longer than the wire length of the material at the bottom dead center of forming when the periphery is constrained during press forming, such as the bent shoulder portion 115 in the form forming of the press-formed product 110 shown in Fig. 2. Another example of such an increased thickness portion is the protruding portion of the top plate in form forming.

[0019] 3 shows, as an example, the change in material length during the press-forming process of a press-formed product 110 in which a bent shoulder 115 is formed by foam forming using a mold 40. In FIG. 3, (a) shows the position of the mold 40 at 30 mm from the bottom dead center of forming, (b) shows 10 mm from the bottom dead center of forming, and (c) shows the cross-sectional shape of the blank 100 at the bottom dead center of forming. Furthermore, as shown in FIG. 2, the press-formed product 110 has a U-shaped cross-sectional shape having a top plate portion 111, a pair of vertical wall portions 113 continuing from both ends of the top plate portion 111, and a bent shoulder portion 115 connecting the top plate portion 111 and the vertical wall portions 113.

[0020] During press forming, as shown in Figure 3(a), while the vertical wall equivalent portion 103 of the blank 100 corresponding to the vertical wall portion 113 is restrained by the mold 40, deflection occurs in the top plate equivalent portion 101 corresponding to the top plate portion 111, resulting in excess material. Therefore, when the punch 41 is further moved relative to the die 43 toward the bottom dead center of the forming, the top plate equivalent portion 101 is deformed as if being crushed, as shown in Fig. 3(b). As a result, at the bending shoulder equivalent portion 105 corresponding to the bending shoulder portion 115, material moves from the top plate equivalent portion 101, and the plate thickness increases. As a result, at the bottom dead center of forming, as shown in FIG. 3(c), the bending shoulder 115 is subjected to a strong pressure by the die 40 to crush it to less than the plate thickness, and the part of the die 40 that forms this part undergoes large elastic deformation.

[0021] In contrast, areas where the thickness does not increase or decrease during press forming, such as the top plate portion 111 and vertical wall portion 113 of the press-formed product 110, are not crushed to the thickness of the target shape at the bottom dead center of forming, so the elastic deformation of areas in the mold that form areas other than the areas where the thickness increases is small.

[0022] From the above, it is thought that in the die model used in press forming analysis, taking into account the elastic deformation of the die in areas where the impact of elastic deformation when forming the thickened section is large will contribute to improving dimensional accuracy. On the other hand, it is thought that taking into account the elastic deformation of the die in areas where the impact of elastic deformation when forming sections other than the thickened section is small will not contribute much to improving dimensional accuracy.

[0023] The method of Patent Document 1 described above takes into account the elastic deformation of the die by modeling a predetermined thickness from the die surface with elastic solid elements. However, the method of Patent Document 1 does not accommodate modeling of a flexible die, without making settings according to the parts of the press-molded product, i.e., increasing the thickness only in parts that are greatly affected by elastic deformation and decreasing the thickness in parts that are less affected by elastic deformation.

[0024] Therefore, the inventors thought that by modeling the mold so that it has parts where the effects of elastic deformation are taken into account and parts where they are not, it might be possible to improve the accuracy of analysis by taking elastic deformation into account and minimize the increase in analysis load.

[0025] Based on the above-mentioned results of the study, the inventors came up with the idea of ​​modeling the mold model used in the press forming analysis using elastic solid elements that can take elastic deformation into account for the areas where the increased thickness parts are formed, and using rigid shell elements for the areas where parts other than the increased thickness parts are formed. The present invention has been made based on the above-mentioned investigation results, and its specific configuration is as follows.

[0026] [Embodiment 1] <Press forming analysis method> The press-forming analysis method according to the first embodiment of the present invention considers elastic deformation of a die in the press-forming analysis of a press-formed product having a thickness-increasing portion where the thickness increases due to press-forming. Hereinafter, the press-forming analysis method according to the first embodiment will be described using a press-formed product 110 having a U-shaped cross section in which a bent shoulder portion 115 is formed by forming, as shown in Fig. 2, as an analysis target.

[0027] The press-forming analysis method according to the first embodiment performs press-forming analysis using a die model 10 shown in FIG.

[0028] The mold model 10 includes a punch 11 and a die 13 . The punch 11 has a punch bottom portion 11a that forms the top plate portion 111, a punch vertical wall portion 11b that forms the vertical wall portion 113, and a punch shoulder portion 11c that forms the bent shoulder portion 115. The die 13 has a die bottom 13a that cooperates with the punch bottom 11a to form the top plate portion 111, a die vertical wall portion 13b that cooperates with the punch vertical wall portion 11b to form the vertical wall portion 113, and a die shoulder portion 13c that cooperates with the punch shoulder portion 11c to form the bending shoulder portion 115.

[0029] In the mold model 10, the punch shoulder 11c and the die shoulder 13c are the portions that form the bent shoulder 115, which is the portion with increased plate thickness. Therefore, in the mold model 10, the punch shoulder 11c and the die shoulder 13c are elastic portions that are modeled with one or more layers of elastic solid elements in the direction away from the blank 100 from the contact surface with the blank 100 (plate-like member).

[0030] Furthermore, in the mold model 10, the parts that form the top plate part 111 and the vertical wall part 113 other than the bending shoulder part 115 are the punch bottom part 11a and the die bottom part 13a, and the punch vertical wall part 11b and the die vertical wall part 13b. Therefore, in the mold model 10, the punch bottom part 11a and the die bottom part 13a, and the punch vertical wall part 11b and the die vertical wall part 13b are each made into rigid parts modeled with rigid shell elements.

[0031] The material properties and size of the punch shoulder 11c and die shoulder 13c modeled with elastic solid elements may be appropriately set by setting the Young's modulus and element size in accordance with the degree of elastic deformation in the mold used in actual press forming.

[0032] Furthermore, in the die model 10 shown in FIG. 1, the nodes of the connection between the punch shoulder 11c, which is modeled using elastic solid elements, and the punch bottom 11a and punch vertical wall 11b, which are modeled using rigid shell elements, are rigidly connected. Furthermore, in the die 13, the nodes at the connection between the die shoulder 13c, which is modeled with elastic solid elements, and the die bottom 13a and die vertical wall 13b, which are modeled with rigid shell elements, are rigidly connected.

[0033] 1, the press forming analysis method according to the first embodiment uses a die model 10 in which only the portion that forms the bent shoulder 115 is modeled with elastic solid elements, and the portions that form the portions other than the bent shoulder 115 are modeled with rigid shell elements. This makes it possible to take into account the elastic deformation of the die that occurs when the bent shoulder 115 is strongly pressed down at the bottom dead center of forming, and improves the accuracy of the analysis while suppressing an increase in the analysis load that would otherwise be caused by using elastic solid elements to model the die model 10.

[0034] In press forming analysis using the die model 10, the operation of the die model 10 can be such that the punch shoulder 11c and the die shoulder 13c, which are rigidly connected to the rigid parts, are simultaneously displaced by applying displacement conditions to the rigid parts modeled using rigid shell elements.

[0035] Furthermore, when the elastic deformation of the elastic portions (punch shoulder 11c and die shoulder 13c) in the mold model 10 is large, excessive stress concentration may occur if only the row of nodes (nodes located perpendicular to the paper surface in FIG. 1) located at the boundary between the elastic portion and the rigid portion on the surface of the mold model 10 are rigidly connected. In such a case, in addition to the row of nodes described above, it is advisable to also rigidly connect the group of nodes located inward (away from the blank 100) from the boundary between the elastic portion and the rigid portion on the surface of the mold model 10.

[0036] However, if nodes located deep inward from the surface of the mold model 10 are rigidly connected, it becomes impossible to take into account the elastic deformation of the elastic portion. Therefore, it is desirable to rigidly connect nodes of the elastic portion located within 1 / 10 of the arc length of the bend shoulder 115 inward from the boundary between the elastic portion and the rigid portion on the surface of the mold model 10 to nodes of the rigid portion.

[0037] The press forming analysis method according to the present invention can be implemented by a computer executing a predetermined program.

[0038] [Embodiment 2] <Method of manufacturing press-molded products> The manufacturing method of a press-formed product according to the second embodiment of the present invention manufactures a press-formed product having a plate thickness increasing portion in which the plate thickness increases during press forming. The manufacturing method of the press-formed product includes a contact pressure calculation step S1, a contact pressure measurement step S3, a press forming analysis step S5, an actual die design and manufacturing step S7, and a press forming step S9, as shown in Fig. 4. Below, each of the above steps will be described for the case where a press-formed product 110 having a U-shaped cross section shown in Fig. 2 is manufactured by form forming.

[0039] ≪Surface pressure calculation process≫ In the surface pressure calculation process S1, a press forming analysis of the press-formed product 110 is performed using a mold model 20 (Figure 5-1) in which the entire mold is modeled using rigid shell elements, and the surface pressure of the bend shoulder portion 115, which is the part with increased plate thickness, is calculated.

[0040] The surface pressure of the bent shoulder 115 calculated in the surface pressure calculation step S1 may be, for example, the surface pressure at the center of the bent shoulder 115 in the cross section of the press-formed product 110 at the center in the longitudinal direction.

[0041] <Surface pressure measurement process> In the surface pressure measurement step S3, the surface pressure of the increased thickness portion (bending shoulder portion 115) when the press-formed product 110 is actually press-formed is measured.

[0042] The portion of increased plate thickness where the surface pressure is measured in the surface pressure measurement step S3 may be, for example, a portion where an increase in plate thickness and an increase in surface pressure are predicted in the surface pressure calculation step S1. In addition, in the surface pressure measurement step S3, the surface pressure of the bend shoulder portion 115 of the press-formed product 110 that has actually been press-formed up to the bottom dead center can be measured by, for example, using pressure-sensitive paper or embedding a load cell in the mold.

[0043] <Press forming analysis process> In the press-forming analysis step S5, first, the surface pressure of the thickness-increased portion (bend shoulder 115) calculated in the surface pressure calculation step S1 is compared with the surface pressure of the thickness-increased portion (bend shoulder 115) actually measured in the surface pressure actual measurement step S3. The surface pressure of the thickness-increased portion calculated in the surface pressure calculation step S1 is determined by press-forming analysis using a die model modeled with rigid shell elements, and therefore is likely to differ from the surface pressure actually measured during actual press-forming in the surface pressure actual measurement step S3. Then, if the calculated surface pressure is 1.5 times or more the actually measured surface pressure, a press-forming analysis of the press-formed product 110 is performed using the press-forming analysis method according to the first embodiment.

[0044] In this embodiment 2, by performing a press molding analysis of the press-molded product 110, it is possible to obtain, as analysis results, for example, the surface pressure of the bending shoulder 115 at the bottom dead center of molding, and the wall opening amount, which is the amount of springback of the press-molded product 110 after it is released from the mold model 10.

[0045] In addition, in order to determine the amount of springback, such as the amount of wall opening of the press-formed product 110, in the press forming analysis process S5, an analysis is performed of the press forming process of the press-formed product 110 up to the bottom dead center of the forming and the springback behavior of the press-formed product 110 after it is released from the mold model 10.

[0046] <Actual mold design and manufacturing process> In the actual die design and manufacturing step S7, a die to be used for press-forming the press-formed product 110 is designed and manufactured based on the analysis results obtained in the press-forming analysis step S5.

[0047] In the actual die design and manufacturing process S7, the die (punch R, die R, clearance, etc.) is adjusted so that the springback amount determined in the press forming analysis process S5 is within the allowable range. Then, the die shape based on the analysis results in the press forming analysis process S5 is used as the NC data for the die design, and the die is machined to design and manufacture it. By doing so, the time-consuming effort required for die adjustment, which has traditionally been required, is minimized, and good press-formed products can be obtained in the press forming process.

[0048] <Press molding process> In the press-molding step S9, press-molding of a press-molded product 110 is performed using the mold designed and manufactured in the actual mold design and manufacturing step S7.

[0049] As described above, according to the manufacturing method of a press-formed product according to the second embodiment, by designing a mold to improve the dimensional accuracy of a press-formed product 110 having a plate thickness increasing portion where the plate thickness increases by press forming, it is possible to manufacture a press-formed product 110 with improved dimensional accuracy.

[0050] Note that the above explanation was about a press-formed product with a U-shaped cross section, but actual press-formed products have a variety of shapes other than just a U-shaped cross section. Therefore, when targeting a press-formed product that does not have a U-shaped cross section, in the press-forming analysis process, a highly accurate analysis can be performed by performing press-forming analysis using a die model in which the areas where there is a large difference in contact pressure between the contact pressure calculation process and the contact pressure measurement process are modeled with elastic solid elements. [Example]

[0051] An analysis was carried out to verify the effects of the present invention, which will be described below. In the example, a press-molding analysis was carried out on a press-molded product 110 having a U-shaped cross section shown in FIG.

[0052] In the press forming analysis, a high-strength hot-rolled steel sheet with a tensile strength of 980 MPa and a thickness of 2.6 mm was used as blank 100, and it was modeled using five layers of cubic elastic-plastic solid elements in the thickness direction. Table 1 shows the mechanical property values ​​of blank 100. [Table 1]

[0053] In addition, the press forming analysis used a die model 10 according to an embodiment of the present invention, as shown in Figure 5-2. In the die model 10, the punch shoulder 11c and die shoulder 13c that form the bent shoulder 115 were modeled using elastic solid elements. Furthermore, in the die model 10, the punch bottom 11a and die bottom 13a, and the punch vertical wall 11b and die vertical wall 13b that form parts other than the bent shoulder 115 were modeled using rigid shell elements.

[0054] Furthermore, in the mold model 10, at the connection between the punch shoulder 11c and die shoulder 13c (modeled with elastic solid elements) and the rigid parts (punch bottom 11a, die bottom 13a, punch vertical wall 11b, die vertical wall 13b) modeled with rigid shell elements, the group of nodes located within 8.9% of the arc length of the bending shoulder 115 inward from the blank contact surface (the group of nodes located within the dotted frame shown in Figure 5-2) were rigidly connected.

[0055] As an example of the invention, a press molding analysis was performed on the process of forming a blank 100 into a press-formed product 110 in one step using a mold model 10, and the springback behavior of the press-formed product 110 after it had been press-formed to the bottom dead center and released from the mold model 10.

[0056] Then, from the press forming analysis results, the surface pressure of the bend shoulder 115 and the wall opening amount of the press-formed product 110 after springback were determined. Here, the surface pressure of the bend shoulder 115 was taken as the value at the center of the bend shoulder 115 of the press-formed product 110 at the bottom dead center of forming. Furthermore, as shown in FIG. 8(b), the wall opening amount is the change in the bending angle of the bend shoulder 115 of the press-formed product 110 before and after springback (= bending angle after springback - bending angle before springback), and is a positive value when the wall opens due to springback, and a negative value when it closes.

[0057] Furthermore, as conventional examples, press forming analysis was performed in the same manner as for the die model 10 when using the conventional die model 20 shown in FIG. 5-1 and the die model 30 shown in FIG. 6. Here, the die model 20 is a model of the entire die (punch 21 and die 23) using rigid shell elements (conventional example 1). Moreover, the die model 30 is a model of the entire die (punch 31 and die 33) using elastic solid elements (conventional example 2). For each of Conventional Example 1 and Conventional Example 2, the blank 100 was modeled in the same manner as in the invention example, and the surface pressure of the bent shoulder portion 115 and the wall opening amount after springback were determined.

[0058] FIG. 7 is a graph comparing the surface pressure of the bending shoulder 115 at the bottom dead center of forming in the invention example, conventional example 1, and conventional example 2. In Conventional Example 1, it is seen that an extremely large surface pressure acts on the bending shoulder portion 115 because the die model 20 does not elastically deform at all. In Conventional Example 2 and the invention example, the die model 30 or die model 10 elastically deforms at the bottom dead center of forming, and therefore the surface pressure at the bend shoulder 115 is reduced compared to Conventional Example 1. Conventional Example 2, in which the entire die is modeled with elastic solid elements, had the lowest surface pressure, while the invention example, in which only the portion that forms the bend shoulder 115 is modeled with elastic solid elements, had a surface pressure that was intermediate between Conventional Example 1 and Conventional Example 2.

[0059] FIG. 8 shows a graph comparing the wall opening amount after springback of a press-formed product 110 that was actually press-formed and a press-formed product 110 that was determined by press forming analysis. It can be seen that Conventional Example 1, in which the entire die was modeled with rigid shell elements, deviated the most from the experimental results, while Conventional Example 2, in which the entire die was modeled with elastic solid elements, was closest to the experimental results. The example of the present invention, in which only the area that forms the bent shoulder was modeled with elastic solid elements, had a wall opening amount that was intermediate between Conventional Example 1 and Conventional Example 2, and showed improved analysis accuracy compared to Conventional Example 1, in which the entire die was modeled with only rigid shell elements.

[0060] Fig. 9 shows a graph comparing the analysis times for the invention example, conventional example 1, and conventional example 2. The analysis times shown in Fig. 7 are plotted against the analysis time for the invention example and conventional example 2, with the analysis time for conventional example 1, in which the entire mold is modeled using elastic shell elements, set at 1. As shown in FIG. 7, the analysis time for Conventional Example 2 was 3.3 times or more that for Conventional Example 1, whereas the analysis time for the inventive example was about 2.3 times that of Conventional Example 1, which was shorter than that of Conventional Example 2.

[0061] The above results show that according to the present invention, in press forming analysis of a press-formed product 110 having a bending shoulder portion 115 whose plate thickness increases during press forming, it is possible to improve analysis accuracy while minimizing increases in analysis time. [Explanation of symbols]

[0062] 10 Mold Model 11 Punch 11a Punch bottom 11b Punch vertical wall 11c Punch shoulder 13 Die 13a Die bottom 13b Die vertical wall 13c Die shoulder 20 Mold Model 21 Punch 23 Die 30 Mold Model 31 Punch 33 Die 40 mold 41 Punch 43 Die 100 blank 101 Top plate equivalent part 103 Vertical wall equivalent 105 Bent shoulder equivalent part 110 Press-molded products 111 Top plate 113 Vertical wall section 115 Bent shoulder

Claims

1. A press forming analysis method that considers elastic deformation of a die in a press forming analysis of a press-formed product having a plate thickness increasing portion whose plate thickness increases during press forming, The die model used in the press forming analysis is an elastic body portion that is a portion for forming the plate thickness increased portion and is modeled using only one or more layers of elastic body solid elements without using rigid body shell elements; A rigid portion that forms a portion other than the plate thickness increasing portion and is modeled by a rigid shell element, a group of nodes of the elastic body portion, which includes a boundary between the elastic body portion and the rigid body portion on the surface of the mold model and is located inward from the boundary and within a range in which elastic deformation in the elastic body portion can be taken into consideration, and nodes of the rigid body portion are rigidly connected.

2. 2. The press forming analysis method according to claim 1, wherein the thickness increasing portion is a bend shoulder formed by forming.

3. A method for manufacturing a press-formed product, which manufactures a press-formed product having a plate thickness increasing portion in which the plate thickness is increased by press forming, a surface pressure calculation step of performing a press forming analysis of the press-formed product using a die model in which the entire die is modeled using rigid shell elements, and calculating the surface pressure of the plate thickness increased portion; a surface pressure measuring step of measuring a surface pressure of the increased plate thickness portion when the press-formed product is actually press-formed; a press-forming analysis step of comparing the surface pressure of the plate thickness increased portion calculated in the surface pressure calculation step with the surface pressure actually measured in the surface pressure actual measurement step, and performing a press-forming analysis of the press-formed product by the press-forming analysis method according to claim 1 when the calculated surface pressure is 1.5 times or more the actually measured surface pressure; an actual die design and manufacturing process for designing and manufacturing a die to be used in press molding of the press-molded product based on the analysis results obtained in the press molding analysis process; and a press molding step of press-molding the press-molded product using the mold thus prepared.

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