Press molding analysis method and method for manufacturing press molding

Abstract

In a press molding analysis method according to the present invention, elastic deformation of a mold is taken into consideration in press molding analysis of a press molding 110 having a bending shoulder part 115 where a plate thickness increases during press molding. A mold model 10 used for the press molding analysis has: an elastic body part which is a part for molding the bending shoulder part 115 and is modeled by one or more layers of elastic body solid elements; and a rigid body part which is a part for molding parts other than the bending shoulder part 115 and is modeled by a rigid body shell element. Nodes of connection parts between the elastic body part and the rigid body part are rigid-coupled.

Description

Press forming analysis method and press forming product manufacturing method

[0001] The present invention relates to a press-forming analysis method for a press-formed product having an area where thickness increases due to press forming, and a manufacturing method for the press-formed product.

[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 the material properties of the sheet metal, including the ductility. In recent years, the demand for lighter car bodies has led to the trend toward higher strength steel sheets used in body parts. However, as the strength of sheet metal increases, spring back also increases, making it necessary to improve the dimensional accuracy of press-formed parts.

[0003] For dies used in press forming of auto body parts, advance predictions are made using press forming analysis with the finite element method (FEM) in order to reduce the trial man-hours required for fabrication. 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 metal sheet increases, the reaction force that the die receives from the metal sheet during press forming also increases. As a result, the die actually undergoes very slight elastic deformation, and the amount of elastic deformation of the die increases as the material strength of the metal sheet increases. However, in typical 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 having 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 metal inflow / material inflow in an actual press by representing the elastic deformation of the die surface in a forming analysis of a shape that involves local increases and decreases in thickness at a flange portion, such as longitudinally curved parts with hat-shaped cross sections.

[0006] Patent No. 5795151

[0007] The method of Patent Document 1 can improve analysis accuracy. However, since elastic solid elements are used to model the die and elastic deformation is taken into account, the analysis load increases significantly. 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 a decrease in 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 an object of the present invention is 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, another object of the present invention is to provide a method for manufacturing a press-formed product by designing and manufacturing a die so as to improve the dimensional accuracy of the press-formed product by the press-forming analysis according to the present invention.

[0009] The press forming analysis method according to the present invention takes into account the elastic deformation of a mold in the press forming analysis of a press-formed product having a plate thickness increasing portion where the plate thickness increases during press forming, and the mold model used in the press forming analysis has an elastic portion that forms the plate thickness increasing portion and is modeled with one or more layers of elastic solid elements, and a rigid portion that forms the portion other than the plate thickness increasing portion and is modeled with rigid shell elements, and the nodes of the connection portions between the elastic portion and the rigid portion are rigidly connected (rigid joint).

[0010] The increased thickness portion may be a bent shoulder formed by foam molding.

[0011] The manufacturing method of the press-molded product according to the present invention manufactures a press-molded product having an increased plate thickness portion whose plate thickness increases by press molding, and includes the following steps: a surface pressure calculation step of performing a press-molding analysis of the press-molded product using a die model in which the entire die is modeled with rigid shell elements, and calculating the surface pressure of the increased plate thickness portion; a surface pressure measurement step of measuring the surface pressure of the increased plate thickness portion when the press-molded product is actually press-molded; a press-molding analysis step of comparing the surface pressure of the increased plate thickness portion calculated in the surface pressure calculation step with the surface pressure actually measured in the surface pressure measurement step, and if the calculated surface pressure is 1.5 times or more the measured surface pressure, performing a press-molding analysis of the press-molded product using the press-molding analysis method according to the present invention; an actual die design and manufacturing step of designing and manufacturing a die to be used in press-molding the press-molded product based on the analysis results obtained in the press-molding analysis step; and a press-molding step of press-molding the press-molded product using the manufactured die.

[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 accuracy of the analysis 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.

[0014] FIG. 1 is a diagram showing a die model used in a press-forming analysis method according to a first embodiment of the present invention. FIG. 2 is a diagram showing an example of a press-formed product having a U-shaped cross section, which is the target of the present invention. FIG. 3 is a diagram showing the cross-sectional shapes of a blank during press-forming of the target of the present invention and the press-formed product. FIG. 4 is a flowchart showing the processing flow of a press-forming method according to a second embodiment of the present invention. FIG. 5-1 is a diagram showing a conventional die model in which the entire die is modeled with rigid shell elements in the second embodiment and examples of the present invention (Conventional Example 1). FIG. 5-2 is a diagram showing rigid connection points between the punch shoulder and die shoulder, which are modeled with elastic solid elements in the examples. FIG. 6 is a diagram showing a conventional die model in which the entire die is modeled with elastic solid elements in the examples (Conventional Example 2). FIG. 7 is a graph comparing the surface pressure of the bend shoulder of a press-formed product at the bottom dead center of forming, determined by press-forming analysis using each die model in the examples. Fig. 8 is a graph showing the wall opening of a press-formed product after springback determined by press forming analysis using each die model in the examples, and a diagram explaining how to determine the wall opening. Fig. 9 is a graph comparing the analysis time of press forming analysis using each die model in the examples.

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

[0016] <Background to the Invention> The inventors have conducted extensive research into a specific method for performing press forming analysis by modeling a die 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] 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 the press forming while 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 a bulging area of ​​a top portion in form forming (crash forming).

[0019] 3 shows, as an example, the change in wire length during the press-forming process of a press-formed product 110 in which a bend shoulder 115 is formed by foam forming using a die 40. In FIG. 3, (a) shows the position of the die 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 bend shoulder portion 115 connecting the top plate portion 111 and the vertical wall portions 113.

[0020] During press forming, as shown in FIG. 3( a), while the vertical wall-equivalent portion 103 of the blank 100 corresponding to the vertical wall portion 113 is restrained by the die 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 forming bottom dead center, the top plate-equivalent portion 101 is deformed as if crushed, as shown in FIG. 3( b). As a result, at the bending shoulder-equivalent portion 105 corresponding to the bending shoulder 115, material moves from the top plate-equivalent portion 101, increasing the plate thickness. As a result, at the forming bottom dead center, as shown in FIG. 3( c), the bending shoulder 115 is subjected to strong pressure by the die 40 to crush it down to the plate thickness or less, and the portion of the die 40 that forms this portion 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 parts 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, i.e., it does not set the thickness according to the parts of the press-molded product, i.e., it increases the thickness only in parts that are greatly affected by elastic deformation and decreases 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 study results, the inventors came up with the idea of ​​modeling the die model used in press forming analysis using elastic solid elements that can take elastic deformation into account for the parts forming the increased thickness parts, and using rigid shell elements for the parts forming parts other than the increased thickness parts. The present invention was made based on the above-mentioned study results, and its specific configuration is as follows.

[0026] [Embodiment 1] <Press-forming analysis method> A press-forming analysis method according to embodiment 1 of the present invention considers elastic deformation of a die in a 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 embodiment 1 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 Figure 2, as an analysis target.

[0027] In the press-forming analysis method according to the first embodiment, a press-forming analysis is performed 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 11a that forms a top plate portion 111, a punch vertical wall portion 11b that forms a vertical wall portion 113, and a punch shoulder portion 11c that forms a bending 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 portions that form the top plate portion 111 and the vertical wall portion 113 other than the bending shoulder portion 115 are the punch bottom portion 11a and the die bottom portion 13a, and the punch vertical wall portion 11b and the die vertical wall portion 13b. Therefore, in the mold model 10, the punch bottom portion 11a and the die bottom portion 13a, and the punch vertical wall portion 11b and the die vertical wall portion 13b are each set as rigid portions 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 can be determined by appropriately 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] 1, the punch 11 has rigidly connected nodes at the connection between the punch shoulder 11c modeled with elastic solid elements and the punch bottom 11a and punch vertical wall 11b modeled with rigid shell elements. Similarly, the die 13 has rigidly connected nodes at the connection between the die shoulder 13c modeled with elastic solid elements and the die bottom 13a and die vertical wall 13b modeled with rigid shell elements.

[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 bend shoulder 115 is modeled with elastic solid elements, and the portions that form the portions other than the bend 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 bend 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 mold model 10, the operation of the mold 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 elastic portions 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 for manufacturing a press-formed product> A method for manufacturing a press-formed product according to embodiment 2 of the present invention manufactures a press-formed product having a plate thickness increasing portion in which the plate thickness increases during press forming. As shown in Fig. 4, the method for manufacturing a 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 production step S7, and a press-forming step S9. 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 Step> In the surface pressure calculation step 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 portion 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 a cross section at the center of the longitudinal direction of the press-formed product 110.

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

[0042] The portion of the plate thickness increase 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 expected 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 (carbonless duplicating paper) or embedding a load cell in the mold.

[0043] <Press-forming analysis step> 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) measured in the surface pressure 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 measured during actual press-forming in the surface pressure measurement step S3. Then, if the calculated surface pressure is 1.5 times or more the 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-formed 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 the forming, and the wall opening amount, which is the amount of springback of the press-formed 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 Die Design and Fabrication Step>> In the actual die design and fabrication step S7, a die to be used for press-forming the press-formed product 110 is designed and fabricated 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 falls within the allowable range. Then, the die shape based on the analysis results in the press forming analysis process S5 is used as 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 conventionally been required, can be minimized, and a good press-formed product can be obtained in the press forming process.

[0048] <Press-molding Step> In the press-molding step S9, press-molding of the 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] 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 using elastic solid elements.

[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 as 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 the 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 the blank 100.

[0053]

[0054] In addition, the press forming analysis used a die model 10 according to an embodiment of the present invention shown in Fig. 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.

[0055] 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 portions modeled with rigid shell elements (punch bottom 11a, die bottom 13a, punch vertical wall 11b, die vertical wall 13b), the group of nodes located within 8.9% of the arc length of the bend shoulder 115 inward from the blank contact surface (the group of nodes present within the dotted line frame shown in Figure 5-2) were rigidly connected.

[0056] 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 has been press-formed to the bottom dead center and released from the mold model 10.

[0057] 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. 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. 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), as shown in Figure 8 (b). If the wall opens due to springback, the value is positive, and if it closes, the value is negative.

[0058] Furthermore, as conventional examples, press forming analysis was performed in the same manner as for the die model 10 for the conventional die model 20 shown in FIG. 5-1 and the die model 30 shown in FIG. 6. The die model 20 was modeled using rigid shell elements to represent the entire die (punch 21 and die 23) (Conventional Example 1). The die model 30 was modeled using elastic solid elements to represent the entire die (punch 31 and die 33) (Conventional Example 2). For each of Conventional Examples 1 and 2, the blank 100 was modeled in the same manner as for the inventive example, and the surface pressure of the bend shoulder 115 and the wall opening amount after springback were determined.

[0059] 7 is a graph comparing the surface pressure on the bend shoulder 115 at the bottom dead center of forming in the invention example, conventional example 1, and conventional example 2. It can be seen that in conventional example 1, the mold model 20 does not elastically deform at all, so an extremely large surface pressure acts on the bend shoulder 115. In conventional example 2 and the invention example, the mold model 30 or mold model 10 elastically deforms at the bottom dead center of forming, so the surface pressure on the bend shoulder 115 is reduced compared to conventional example 1. Conventional example 2, in which the entire mold 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 somewhere between conventional examples 1 and 2.

[0060] 8 shows a graph comparing the wall opening amount after springback for an actual press-formed product 110 and a press-formed product 110 calculated 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. Furthermore, the inventive example, in which only the portion forming the bend shoulder was modeled with elastic solid elements, showed a wall opening amount intermediate between Conventional Examples 1 and 2, demonstrating improved analysis accuracy compared to Conventional Example 1, in which the entire die was modeled with only rigid shell elements.

[0061] Fig. 9 is a graph comparing the analysis times for the invention example, conventional example 1, and conventional example 2. The analysis time shown in Fig. 7 is set to 1 for conventional example 1, in which the entire mold is modeled with elastic shell elements, and shows the analysis times for the invention example and conventional example 2. As shown in Fig. 7, the analysis time for conventional example 2 is more than 3.3 times that of conventional example 1, while the analysis time for the invention example is about 2.3 times that of conventional example 1, which is shorter than that of conventional example 2.

[0062] From the above results, it has been shown 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 suppressing an increase in analysis time.

[0063] According to the present invention, it is possible to provide a press-forming analysis method for performing press-forming analysis by modeling a die so as to improve the analysis accuracy while suppressing an increase in the analysis load.Furthermore, according to the present invention, it is possible to provide a method for manufacturing a press-formed product by designing and manufacturing a die so as to improve the dimensional accuracy of the press-formed product by the press-forming analysis according to the present invention.

[0064] REFERENCE SIGNS LIST 10 Die 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 Die model 21 Punch 23 Die 30 Die model 31 Punch 33 Die 40 Die 41 Punch 43 Die 100 Blank 101 Top plate equivalent 103 Vertical wall equivalent 105 Bending shoulder equivalent 110 Press-molded product 111 Top plate 113 Vertical wall 115 Bending shoulder

Claims

1. A press forming analysis method that takes into account elastic deformation of a mold in a press forming analysis of a press-formed product having a plate thickness increasing portion whose plate thickness increases during press forming, wherein the mold model used in the press forming analysis has an elastic portion that forms the plate thickness increasing portion and is modeled with one or more layers of elastic solid elements, and a rigid portion that forms portions other than the plate thickness increasing portion and is modeled with rigid shell elements, and the nodes of the connection portions between the elastic portion and the rigid portion are rigidly connected.

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

3. A method for manufacturing a press-formed product that manufactures a press-formed product having an increased thickness portion whose thickness increases through press forming, comprising: 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 increased thickness portion; a surface pressure measurement step of measuring the surface pressure of the increased thickness portion when the press-formed product is actually press-formed; a press-forming analysis step of comparing the surface pressure of the increased thickness portion calculated in the surface pressure calculation step with the surface pressure actually measured in the surface pressure measurement step, and if the calculated surface pressure is 1.5 times or more the measured surface pressure, performing a press-forming analysis of the press-formed product using the press-forming analysis method according to claim 1; an actual die design and fabrication step of designing and fabricating a die to be used in press-forming the press-formed product based on the analysis results obtained in the press-forming analysis step; and a press-forming step of press-forming the press-formed product using the fabricated die.

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