Method for designing preformed shape, method for manufacturing press-formed product, and program

Abstract

The present invention provides a technology that enables easier design of a preformed shape. The method for designing a preformed shape of an intermediate part includes a position identification process (20) for identifying a crack occurrence position where a crack is estimated to occur in a press-formed product when a metal plate is press-formed to the bottom dead center with a die capable of forming the target shape in one press forming operation, a first surface area calculation process (21) for calculating a surface area (A1) located in a first region within a preset distance (L0) from the crack occurrence position in the target shape, a basic shape setting process (22) for setting a basic shape of the preformed shape based on the target shape, a second surface area calculation process (23) for calculating a surface area (A2) located in a second region within the distance (L0) from a position corresponding to the crack occurrence position in the basic shape, and a basic shape deformation process (24) for deforming the basic shape so as to satisfy the following formula (1). 0.9×A1

Description

[Technical field]

[0001] The present invention relates to a technique for realizing the manufacture of difficult-to-form parts and the like. A difficult-to-form part is a press-formed product that may crack if it is formed into a target shape in a single press molding. In particular, the present invention relates to a technique for designing a preformed shape, which is the shape of an intermediate part, in order to realize the molding of a difficult-to-form part. The present invention also relates to a method for manufacturing a press-formed product using the preformed shape design technique. [Background technology]

[0002] From the viewpoint of improving vehicle crash safety and fuel efficiency, the performance required for automobile parts includes light weight, high strength, high rigidity, etc. To improve these performances, there is a demand for more complex part shapes. There is also a demand for higher strength materials to be used. For this reason, automobile parts tend to be difficult to form. As a result, there is a problem that it may be difficult to manufacture automobile parts by press forming.

[0003] In order to solve the above problems, various press forming methods have been developed, such as those described in Patent Documents 1 and 2. Patent Document 1 discloses a method for improving formability by dividing processes to form a target shape and optimizing the shape of each process. Patent Document 2 deals with deep drawn square cylinder shapes. Patent Document 2 also discloses a method for improving formability by optimizing the shape of each process or the blank shape. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5867657 [Patent Document 2] Patent No. 7070820 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, cracks during forming are a frequent problem when manufacturing parts with complex shapes by press forming, or when manufacturing products by press forming high-strength materials. Cracks occur due to localized concentration of strain in the material. Therefore, in order to prevent this, it is effective to suppress the concentration of strain.

[0006] For this reason, in the methods described in Patent Documents 1 and 2, the press working process is divided into two or more steps. In addition, in the methods described in Patent Documents 1 and 2, a proper intermediate part shape is formed in a step prior to the final step. In this way, Patent Documents 1 and 2 disclose a technique for effectively dispersing strain and improving formability. However, in the disclosed technology, the line length in a specific cross section is compared between preforming and actual forming. Then, the design is made based on the comparison. However, the position, direction, and number of the cross sections are arbitrary. Therefore, the formability improvement effect may differ greatly depending on how the cross sections are taken and the number of cross sections taken. Also, countless preforming shapes with the same cross-sectional line length but different cross-sectional shapes can be designed. Therefore, repeated calculations are required to determine the appropriate shape from among them. Moreover, at that time, it is necessary to design the preforming shape over almost the entire area of ​​the part shape each time. Therefore, in the past, there was a problem that designing the preforming shape required a large time cost.

[0007] The present invention has been made in light of the above-mentioned points, and aims to provide a technique that enables a preformed shape to be designed more easily, and a technique related to the manufacture of a press-formed product using the preformed shape design. [Means for solving the problem]

[0008] The inventors have investigated a preform shape design method to solve the above problems, and have obtained the following findings. (1) When press-molding the desired shape, there is no need to design the preform shape for areas where cracks will not occur. Based on this idea, it is sufficient to consider the design of the preform shape only for the area where cracks are expected to occur and the surrounding area of ​​that area. (2) When comparing cross-sectional line lengths, the results are affected by how the cross-sections are taken. However, if the interval at which the cross-sections are taken is made infinitesimally small, the sum of the cross-sectional line lengths will be equal to the surface area or can approximate the surface area. Furthermore, once the area to calculate the surface area has been determined, the same value will be obtained no matter who calculates it. (3) In areas where cracks are expected to occur, the necessary surface area is secured by preforming, which reduces the concentration of strain in the material that occurs during the actual forming process and makes it possible to suppress cracks.

[0009] The above finding has the following feature: once the area for designing the preformed shape and the method for combining the surface areas are determined, the result is uniquely determined. Therefore, the above finding has the feature that the result is the same no matter who designs it. Therefore, the above finding has the feature that, for example, once a program for designing the preformed shape is created, the preformed shape can be designed automatically.

[0010] In order to solve the problem, one aspect of the present invention is a method for designing a preformed shape when manufacturing a press-formed product of a target shape by press working including a preforming process of press-forming a metal plate into a preformed shape and a main forming process of press-forming an intermediate part of the preformed shape into a target shape, the method including a position identification process for identifying a crack occurrence position where a crack is estimated to occur in the press-formed product when the metal plate is press-formed to the bottom dead center with a die capable of forming the metal plate into the target shape in a single press forming operation, a first surface area calculation process for calculating a surface area A1 located in a first region within a preset distance L0 from the crack occurrence position in the target shape, a basic shape setting process for setting a basic shape of the preformed shape based on the target shape, a second surface area calculation process for calculating a surface area A2 located in a second region within the distance L0 from a position corresponding to the crack occurrence position in the basic shape, and a basic shape deformation process for deforming the shape of the basic shape so as to satisfy the following formula (1). 0.9×A1 <A2<1.1×A1 ··(1) The first and second regions are large and have the same shape. Effect of the Invention

[0011] According to the aspects of the present invention, it is possible to more easily design a preformed shape, and as a result, it is possible to more easily manufacture a press-formed product. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram showing an example of a flow of manufacturing a press-molded product according to an embodiment based on the present invention. [Diagram 2] FIG. 1 illustrates an example of a process configuration for designing a preformed shape according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a conceptual diagram illustrating the transition of a preformed shape design according to an embodiment of the present invention. [Figure 4] FIG. 11 is a diagram illustrating a second shape setting step. [Diagram 5] FIG. 11 is a diagram illustrating a second shape setting step. [Figure 6] 4 is a diagram showing the relationship between each side and a dividing line 42 of a single shape and a target shape 41 when viewed in a plan view. [Figure 7] FIG. 13 is a diagram illustrating a change in a surface in a second region. [Figure 8] 1 is an example for explaining an example of a function f(L). [Figure 9] FIG. 13 illustrates an example of a program configuration. [Figure 10] FIG. 1 illustrates an example of a process configuration for designing a preformed shape according to an embodiment of the present invention. [Figure 11] FIG. 13 illustrates an example of a program configuration. [Figure 12] 13A and 13B are diagrams showing a target shape and crack positions in an embodiment. [Figure 13] FIG. 2 is a diagram showing a basic shape in an embodiment. [Figure 14] FIG. 1 is a diagram showing a preformed shape in an embodiment. [Figure 15] FIG. 2 is a diagram showing a press-molded product in an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, an embodiment of the present invention will be described with reference to the drawings. Consider press forming in which a metal sheet is press-formed to the bottom dead center in one press forming operation using a die capable of forming the metal sheet into a target shape. In some cases, it is estimated that cracks will occur in the press-formed product formed during the press forming operation. This embodiment is a technique that assumes such a case. The die capable of forming the metal sheet into the press-formed product of the target shape is, for example, a die whose forming surface is the same as or similar to the target shape.

[0014] In this embodiment, as shown in Fig. 1, a press working 2 including a preforming step 2A and a main forming step 2B is used. In this embodiment, a technique for manufacturing a press-formed product 11 having a target shape by the press working 2 is described. The preforming step 2A is a step of press-forming a metal plate into an intermediate part 10 having a preformed shape. The main forming step 2B is a step of press-forming the intermediate part 10 having the preformed shape into a press-formed product 11 having a target shape. The present disclosure is particularly a technique related to the design of the preformed shape associated with the manufacture of the press-formed product.

[0015] "First embodiment" (Preformed shape design method) In the design of the preformed shape in the first embodiment, a basic shape of the preformed shape, which is the shape of the intermediate part 10, is provisionally set. Then, a partial area of ​​the provisionally set basic shape is changed as a design area. In this way, in the design of the preformed shape in the first embodiment, the preformed shape is designed. In this embodiment, after the basic shape is provisionally set, only the design area needs to be changed. However, the present invention also includes changing the shapes of other areas in conjunction with the change in the shape of the design area. The design area is the crack occurrence area and the peripheral area of ​​that area. The peripheral area is, for example, a part that is affected by cracks.

[0016] As shown in Fig. 2, the preformed shape design method of this embodiment includes a position identification step 20, a first surface area calculation step 21, a basic shape setting step 22, a second surface area calculation step 23, a basic shape deformation step 24, and a shape evaluation step 25. As shown in Fig. 2, the preformed shape design method of this embodiment also includes a basic shape resetting step 26. It does not matter which of the first surface area calculation step 21 and the basic shape setting step 22 is executed first. It does not matter which of the first surface area calculation step 21 and the basic shape setting step 22 is executed first.

[0017] The design of the preformed shape of this embodiment is processed according to the procedure shown below. As described below, this process can be performed by a known forming analysis method. The known forming analysis method may be a forming analysis method using CAE that uses a computer. That is, the process of the method for designing the preformed shape of this embodiment can be configured as a program executed by a computer.

[0018] <Location identification process 20> The position specifying process 20 assumes that a metal plate is press-formed to the bottom dead center with a die capable of forming the metal plate into a target shape in one press forming operation. The position specifying process 20 then performs a process of specifying a crack occurrence position W where a crack is estimated to occur in the press-formed product based on that assumption (see FIG. 3(a)). In the position specifying step 20 of this embodiment, a forming analysis for press-forming a metal plate into a target shape is performed by finite element analysis using CAE. Then, in the position specifying step 20, a region where a crack will occur is specified from the analysis result.

[0019] In this process, if the target shape, the material properties of the target metal plate, and the fracture limit of the material are known in advance, it is possible to automatically determine the crack occurrence position W using conventional general knowledge. Note that the crack occurrence position W may be determined by performing actual press forming. Here, the detected crack occurrence position W is not limited to one. As shown in Fig. 3(a), there may be multiple crack occurrence positions W. In this case, the processes of the first surface area calculation step 21 and the second surface area calculation step 23 described below, and the associated process of the basic shape transformation step 24 may be performed for each crack occurrence position W. The following description of the process basically assumes that the process is performed in response to each crack occurrence position W individually.

[0020] <First surface area calculation step 21> The first surface area calculation process 21 performs a process of calculating a surface area A1 based on the crack occurrence position W determined by the position identification process 20 (see FIG. 3(b)). The surface area A1 is the surface area located in a first region within a preset distance L0 from the crack occurrence position W in the target shape. For example, the center position of the cracked part is used as the crack occurrence position W. In this case, the area surrounded by a sphere of radius L0 with the center position of the cracked part as the center becomes the first area. The same applies to the second area described later. Note that the first area and the second area are, for example, areas of the same size. Alternatively, the crack occurrence position W may be an area having a predetermined size, and a position a predetermined distance away from the outer circumferential contour position of that area may be set as the outer edge of the first region. However, the above method is simpler.

[0021] In the first surface area calculation step 21 of this embodiment, the sum of the surface areas (surface area A1) of the meshes present in the first region among the meshes expressing the target shape (press molded shape) is calculated from the molding analysis information. This step can be performed automatically in conjunction with the result of the position specification step 20 if the distance L0 is determined in advance. The area of ​​each mesh can be calculated, for example, by Heron's rule from the coordinate information of each node constituting the mesh. However, other methods may also be used to calculate the area.

[0022] [About distance L0] The distance L0 is set as follows. For example, the distance L0 is set to a size that ensures that the crack area and its entire outer periphery are included within the first area defined by the distance L0. The setting may be based on, for example, experiments or past experience. The distance L0 (mm) may be set so as to satisfy the following formula (3), for example, when the tensile strength of the metal plate to be processed is TS (MPa). 0.5×(TS 0.5 )≦ L0(mm) ≦ 3×(TS 0.5 ) (3)

[0023] Here, the outer edge of the first region defined by the distance L0 is basically designed to be closer to the crack generation region to have a greater effect in suppressing cracks. However, if the distance L0 is less than 0.5 x (TS^0.5), the defined region may become too narrow. In this case, the preformed shape designed to match the surface area may become too steep, making it difficult to form the preformed shape. On the other hand, if the distance L0 exceeds 3 x (TS^0.5), the first region defined by the distance L0 becomes too large, reducing the effect of suppressing cracks.

[0024] The reason why tensile strength TS is included in the regulation of distance L0 in formula (3) is as follows. In other words, ultra-high tensile steel is generally more susceptible to strain concentration and cracking than mild steel. Therefore, the higher the tensile strength, the more widely it is necessary to perform pre-forming to disperse strain. Also, if the pre-formed shape is too steep, it will not be possible to fully form the pre-formed shape into the target shape in the main forming process 2B, and marks will likely remain.

[0025] <Basic shape setting process 22> The basic shape setting process 22 involves setting a basic shape 30, which is the basis of the preformed shape, which is the shape of the intermediate part 10, based on the target shape (see FIG. 3(c)). It is preferable that the basic shape 30 is a shape that is close to the target shape as a whole. The basic shape setting step 22 may be exemplified by the following first shape setting step and second shape setting step. However, the scope of the present disclosure also includes a case where the basic shape 30 is obtained by other known methods for obtaining a preformed shape. However, it is preferable to set the basic shape 30 of the preformed shape by a simple process.

[0026] [First shape setting process] In the first shape setting process, one of the multiple formed shapes before the crack occurs is selected as the basic shape 30 of the preformed shape. Each of the multiple formed shapes is a shape selected from the formed shapes during forming of the metal plate to the bottom dead center using a die capable of forming the metal plate into a target shape. In the first shape setting step of this embodiment, a basic shape 30 of the preforming shape is set in the forming analysis in the position specifying step 20. At this time, a shape in a forming stage before cracks occur is set as the basic shape 30 of the preforming shape.

[0027] At this time, there is a possibility that strain concentration has already started in the formed shape immediately before cracks occur. For this reason, it is desirable to use a formed shape in a state where the forming depth is 2 mm or more shallower than the forming depth at which cracks occur as the basic shape 30. Here, the minimum value of the forming depth is 0 mm. In other words, the present disclosure also includes using the shape of the metal sheet before forming as the basic shape 30.

[0028] [Second shape setting process] In the second shape setting step, the basic shape 30 is set by the following first to fifth steps. Here, the shape of the metal plate is expressed as a set of multiple elements from before to during forming. The shape is expressed, for example, as a mesh of multiple elements (see FIG. 4(a)). FIG. 4(a) shows the state in which the sides of all elements are expressed as equations and Amm, Bmm, and Cmm are calculated for all elements.

[0029] First, in the first setting step, a reference plane 40 that is a plane perpendicular to the pressing direction in the main forming step 2B is assumed (see FIG. 5(a)). Then, polygonal single shapes 40A are arranged so as to be continuously aligned on the reference plane 40. This sets the reference plane 40 as a plane partitioned by a repetition of a plurality of single shapes 40A (see FIG. 5(b)). It is preferable that the plurality of unitary shapes 40A are arranged two-dimensionally so as to be aligned linearly in the same direction.

[0030] FIG. 5(b) shows an example in which the single shape 40A is a quadrangle. The quadrangle may be a rectangle or a rhombus. For example, the reference plane 40 may be divided by lines in a grid pattern, and multiple single shapes 40A may be arranged on the reference plane 40. In this case, the reference plane 40 can be easily divided into multiple single shapes 40A simply by dividing it into a grid pattern. In other words, it is possible to simply and easily define the reference plane 40 consisting of multiple single shapes 40A. Examples of the single shape include a quadrilateral shape, a triangular shape, a hexagonal shape, etc. However, it is preferable that the sides of the multiple adjacent single shapes 40A arranged in a two-dimensional direction are linearly continuous along the extension direction of the sides (see FIG. 5(b) and FIG. 6).

[0031] Next, a reference plane 40 is assumed to be partitioned by a plurality of single shapes 40A and made up of the plurality of single shapes 40A. The reference plane 40 is moved in the press direction toward the target shape 41, and a state in which it intersects with the target shape 41 is assumed. That is, a state in which each side of each single shape 40A arranged on the reference plane 40 intersects with the target shape 41 is assumed. Then, in the second setting step, a process is performed in which the faces of the target shape are divided by division lines 42 formed on the faces of the target shape 41 by the above intersection (see FIG. 6). An example of the relationship between the division lines 42 and the meshes is shown in FIG. 4(b). Next, in the third setting step, three or more nodes 45 are arranged on each of the division lines 42 corresponding to each side of each single shape 40A. The three or more nodes 45 are arranged apart from each other. The multiple nodes 45 are arranged, for example, at equal intervals when viewed from the pressing direction.

[0032] Next, in the fourth setting step, a plurality of smooth curves 43 are set by connecting the plurality of nodes 45 arranged along the extension direction of each division line 42 (see FIG. 4(c)). Consider the case as seen from the pressing direction (for example, from above) as shown in FIG. 6. In this case, the division lines 42 connecting the respective sides of the single shape 40A and the smooth curves 43 based on the division lines have the same straight line shape. However, when viewed from a side perpendicular to the pressing direction, the curves 43 have a smooth curved shape without corners. On the other hand, the division lines 42 are lines connecting the respective sides of the single shape 40A. Therefore, when viewed from a side perpendicular to the pressing direction, the division lines 42 may have corners in parts. In addition, the division lines 42 may have a portion with a sharper curvature than the curves 43.

[0033] Next, in the fifth setting step, a surface shape is formed by smoothly extending surfaces in each region 44 (see FIG. 6) surrounded by the set curves 43. The surface shape is set as the basic shape 30 (see FIG. 4(d)). Note that it is preferable to smoothly connect the surfaces extended in each region 44.

[0034] Here, cracks in press-formed products occur when deformation is concentrated in areas where the shape is deformed sharply. The basic shape 30 designed by the method of this second shape setting process is roughly close to the target shape. However, the basic shape 30 is a shape that is easy to form because the surface shapes in various places are appropriately gentle. This shape is used as the basic shape 30 of the preformed shape, and the preformed shape is designed in a later process. The shape designed in this step may be used as a preformed shape for the actual forming. If no cracks are generated as a result, the design of the preformed shape is completed at this step. In addition, it is preferable to set the interval between adjacent parting lines 42 to be 1 / 10 or less of the line length of the target shape. The line length of the target shape is the line length in the arrangement direction of the adjacent parting lines 42.

[0035] <Second surface area calculation step 23> The second surface area calculation process 23 performs a process of calculating the surface area A2 based on the crack occurrence position W determined by the position identification process 20 (see FIG. 3(d)). The surface area A2 is the surface area located in a second region within a distance L0 from the position corresponding to the crack occurrence position W in the basic shape 30. In the second surface area calculation step 23 of this embodiment, the basic shape 30 obtained in the basic shape setting step 22 is defined by a mesh based on a known forming analysis. Then, the sum of the surface areas of the meshes present in the second region (surface area A2) is calculated. The mesh conditions may be, for example, the same as the mesh conditions defining the target shape.

[0036] In this step, the second region is determined, for example, by a method in which the second region is determined to be a region made up of elements having the same element numbers as the elements included in the first region determined in the first surface area calculation step 21. In the case of an analysis method in which the element numbers change during molding, a mark is added to the outer edge of the first region in the analysis software. Then, a method can be considered in which the molding analysis is rewound to the shape that is the basis of the preformed shape, and the region is determined to be the region surrounded by the mark. However, any method may be used.

[0037] <Basic shape transformation process 24> Here, the area of ​​basic shape 30 existing within the second region becomes the design region of the preformed shape for basic shape 30. Then, in basic shape deformation process 24, a process is performed in which the second region of basic shape 30 is deformed to change the surface area within the second region so that the above-mentioned cracks do not occur in main forming process 2B. In this way, shape 31 obtained by deforming basic shape 30 is designed as a candidate for the preformed shape (see FIG. 3(e)).

[0038] The basic shape transformation step 24 of this embodiment performs processing to transform the shape of the basic shape 30 so as to satisfy formula (1). 0.9×A1 <A2<1.1×A1 ···(1) As described above, A1 indicates the surface area existing in the first region in the target shape 41. A2 indicates the surface area existing in the second region in the basic shape 30.

[0039] Here, if the surface area A2 is too small, there is a risk that preforming will be ineffective and cracks will occur. On the other hand, if the surface area A2 is too large, cracks may occur during preforming. On the other hand, if the surface area A2 is too large, even if no cracks occur during preforming, there may be excess material during main forming, which may result in wrinkles. For these reasons, it is more desirable to have "0.95 x A1 < A2 < 1.05 x A1".

[0040] In the basic shape deformation process 24, for example, as shown in Fig. 7, the nodes of the mesh in the second region are moved up and down (in the pressing direction or plate thickness direction). This adjusts the surface area A2 of the basic shape existing in the second region. At this time, the amount of movement (amount of displacement in the vertical direction) is adjusted according to the distance from the crack occurrence position W. In addition, adjustments are made so that the area to be changed in the second region and the area around the second region are smoothly connected.

[0041] In the basic shape transformation step 24, such an adjustment is performed based on an equation such as the following equation (2). By setting equation (2), it becomes possible to further automate the processing in the basic shape transformation step 24. The surface shape in the second region is changed to, for example, the surface shape expressed by this equation (2). P(q, L) = q × f(L) (2) Here, the function f(L) represents a smooth curve and is a function formula that satisfies f(L0)=0, f'(0)=0, and f'(L0)=0. It should be noted that L is the shortest distance from the position corresponding to the crack occurrence position W. The shortest distance from the crack occurrence position W to the boundary of the second region is L0. An example of the function f(L) is shown in FIG. Then, the value of q is adjusted as a variable, so that the surface area A2 of the portion of basic shape 30 located within the second region is determined so as to satisfy formula (1).

[0042] An example of formula (2) is shown below. P(q, L)=q×(-(cos(2π×L / L0)-1) / 2) (2)′ In this example, f(L) is set to "(-(cos(2π×L / L0)-1) / 2)".

[0043] Next, consider the second region for designing the shape of the basic shape 30 that is the basis for preforming of the finite element analysis model. Add the number represented by P(q, L) corresponding to L of each node to the z coordinate of all nodes in the second region. By such processing, the surface area A2 is calculated. At this time, a conceivable method is to adjust the basic shape 30 by performing calculations while increasing or decreasing the value of q until formula (1) is satisfied.

[0044] The reason why trigonometric functions are used in equation (2)' is as follows. That is, the differential value of equation (2)' is 0 at positions L = 0 and L = L0, and P(L) is 0 at position L = L0. Also, if the above condition is not satisfied, the connection between the second area where the shape is designed and the outside of the second area becomes discontinuous. As a result, it becomes difficult to establish the shape as a mold shape (molding surface shape). However, as long as the above condition is satisfied, f(L) may be another equation, such as a combination of trigonometric functions or a polynomial function.

[0045] <Shape evaluation process 25> In the shape evaluation process 25, first, the basic shape 30 obtained in the basic shape transformation process 24 is set as a preforming shape. Then, using the preforming shape and the target shape, a forming analysis is performed simulating the preforming process 2A and the main forming process 2B (see FIG. 3(f)). Then, in a shape evaluation process 25, it is determined whether or not cracks will occur through forming analysis. If it is determined through the forming analysis that no cracks will occur, the design process is terminated (see FIG. 3(g)).

[0046] If it is determined that cracks will occur, the process proceeds to basic shape resetting step 26. Then, basic shape 30 is changed, and the processing of second surface area calculation step 23 and basic shape transformation step 24 is repeatedly executed until the cracks are contained. Even if cracks have occurred, if it is determined that the cracks can be avoided by minor corrections to the preformed shape using other means, it is possible to end the design at any time.

[0047] <Basic shape resetting process 26> In the case where a crack occurs in the main forming process 2B, the basic shape resetting process 26 updates the changed basic shape 30 obtained in the basic shape deformation process 24 to a new basic shape 30. Note that the areas that are addressed in the processing of the second surface area calculation process 23 and the basic shape deformation process 24 are only the areas where a crack occurred in the shape evaluation process 25 described above. Furthermore, if the location where the crack has occurred has changed, the shape evaluation step 25 is treated as a process of the position identification step 20, and the first surface area calculation step 21 is also executed again. Regardless of whether the location where the crack has occurred has changed, the shape evaluation step 25 may be treated as a process of the position identification step 20, and the first surface area calculation step 21 may also be executed again.

[0048] If it is determined that a crack has occurred in the preforming process 2A, the basic shape resetting process 26 increases the safety margin against cracks compared to the previous time. Then, the same process as the basic shape setting process 22 is performed to reset the basic shape 30. In the first shape setting process, increasing the safety margin corresponds to, for example, making the forming depth shallower.

[0049] (program) Here, it is preferable that the above processing is performed automatically using a computer. Once formula (2) and distance L0 are determined, other conditions can be determined mechanically. Therefore, it is possible to automatically process the calculation of the design of the preformed shape by a computer. In this case, it is possible to achieve further efficiency. That is, the design processing of this embodiment is configured as a program. Then, the program may be stored in a storage unit and executed by a computer.

[0050] For example, a program 50 for causing a computer to execute is configured to include a position identification step 50A, a first surface area calculation step 50B, a basic shape setting step 50C, a second surface area calculation step 50D, a basic shape deformation step 50E, and a shape evaluation step 50F as shown in FIG. 9.

[0051] The position identification step 50A performs a forming analysis up to the bottom dead center of the forming under the analysis conditions of press-forming a metal plate into a target shape in a single press-forming. Thereby, a process of identifying the position where cracks occur is executed. The first surface area calculation step 50B executes a process of obtaining a surface area A1 located within a region within a set distance L0 from the crack generation position identified in the position identification step 50A in the target shape.

[0052] The basic shape setting step 50C executes a process of temporarily setting a basic shape 30 of a preformed shape based on the target shape. The second surface area calculation step 50D executes a process of obtaining a surface area A2 located within a second region in the basic shape 30. The second region is a region within the distance L0 from the position corresponding to the crack generation position identified in the position identification step 50A. The basic shape deformation step 50E performs a process of deforming at least the shape within the second region in the basic shape 30 so that the shape within the second region in the basic shape 30 satisfies 0.9×A1 < A2 < 1.1×A1.

[0053] At this time, when only the shape within the second region is deformed, it is preferable that the deformation is zero at the outer peripheral position of the second region and the deformation is made to be smoothly connected to the outside of the second region. In the shape evaluation step 50F, the modified basic shape 30 obtained in the basic shape deformation step 50E is used as the preformed shape, and a forming analysis is performed to form the preformed shape and perform the main forming. Then, the presence or absence of cracks is evaluated. If it is determined that no cracks will occur, the process ends. If it is determined that cracks will occur, the modified basic shape 30 obtained in the basic shape deformation step 50E is changed to the basic shape 30. Then, the process returns to the first surface area calculation step 50B and the subsequent steps are repeatedly performed until the cracks are eliminated.

[0054] The program consisting of the above steps can be created by a known forming analysis method using a computer-aided CAE. Examples of inputs to the program include the target shape, the material properties of the target metal plate, and the fracture limit of the material. The program may also be configured to execute each process described above in the design of the preformed shape.

[0055] (Method of manufacturing press-molded products) As shown in FIG. 1, the method for manufacturing a press-formed product of this embodiment includes a preformed shape design step 1, a preformed step 2A, and a main forming step 2B. In the preform shape design step 1, the preform shape is determined by the preform shape design method described above. In the preforming step 2A, a metal plate is press-formed into a desired preform shape to manufacture the intermediate part 10. In the main forming step 2B, the intermediate part 10 having the preform shape is press-formed into a target shape. By the above-described processing, a preformed shape can be designed in a simple manner, and a press-formed product that is free from cracks can be produced more reliably.

[0056] "Second embodiment" (Preformed shape design method) The second embodiment is a forming method for directly determining the preformed shape, which is the shape of the intermediate part 10. The preformed shape design of the second embodiment includes a preformed shape setting step 60 and a shape evaluation step 25, as shown in FIG. In the preformed shape setting step 60, the preformed shape is designed by the following first setting step 60A to fifth setting step 60E. First, in the first setting step 60A, a reference plane 40 that is a plane perpendicular to the pressing direction in the main forming step 2B is assumed. Then, polygonal single shapes 40A are arranged so as to be continuously aligned on the reference plane 40. In this way, the reference plane 40 is set as a plane partitioned by a repetition of a plurality of the single shapes 40A.

[0057] At this time, in the first setting step 60A, it is preferable to arrange a plurality of single shapes 40A by making the single shape 40A a quadrangle and dividing the reference plane 40 with grid-like lines. It is also preferable to divide the reference plane 40 into a plurality of single shapes 40A. In this case, it is possible to simply and easily define the reference plane 40 consisting of a plurality of single shapes 40A.

[0058] Next, a reference plane 40 is assumed to be partitioned by a plurality of single shapes 40A and made up of the plurality of single shapes 40A. The reference plane 40 is moved in the press direction toward the target shape to assume a state in which it intersects with the target shape. That is, a state in which each side of each single shape 40A arranged on the reference plane 40 intersects with the target shape is assumed. In a second setting process 60B, the surface of the target shape is divided by division lines 42 formed on the surface of the target shape by the intersecting state. Next, in a third setting step 60C, three or more nodes are placed on each of the division lines 42 corresponding to each side of each single shape 40A. The three or more nodes are placed at equal intervals when viewed from the pressing direction.

[0059] Next, in a fourth setting step 60D, a curve 43 is set that connects the multiple nodes aligned along the extension direction of the division lines 42. The curve 43 is set as a smooth curve that does not have a steep curvature portion (corner portion). A plurality of curves 43 are set for each extension direction of each division line 42. Next, in a fifth setting step 60E, a surface shape is formed by smoothing each area surrounded by the set curves 43, and the surface shape is set as a preform shape.

[0060] Here, cracks in press-formed products occur when deformation is concentrated in areas where the shape is deformed sharply. The preformed shape designed using the method of the second embodiment is roughly close to the target shape. However, the preformed shape has a moderately gentle shape in each area, making it easy to form. Moreover, it is preferable to set the interval between adjacent parting lines 42 to be 1 / 10 or less of the line length of the target shape. The line length of the target shape is the line length in the arrangement direction of the adjacent parting lines 42.

[0061] <Shape evaluation process 61> In the shape evaluation process 61, first, a forming analysis is performed simulating the preforming process 2A and the main forming process 2B using the preforming shape and the target shape obtained in the preforming shape setting process. Then, in the shape evaluation process 61, it is determined whether or not cracks will occur in the forming analysis. If it is determined that cracks will occur, the preformed shape is changed until the cracks subside. That is, if a crack occurs in the preforming process 2A, the preforming shape setting process executes processing with a larger safety margin against cracks than in the previous process, thereby resetting the preforming shape. Even if cracks have occurred, if it is determined that the cracks can be avoided by minor corrections to the preformed shape using other means, it is possible to end the design at any time.

[0062] (program) Here, it is preferable that the above processing is performed automatically using a computer. By determining the reference plane 40 consisting of a plurality of single shapes 40A, other conditions can be determined mechanically. Therefore, it is possible to further improve efficiency by automatically performing the calculations using a computer. In other words, the design processing of this embodiment may be configured as a program, stored in a storage unit, and executed by a computer.

[0063] For example, a program 70 executed by a computer may be configured to include a first setting step 70A to a fifth setting step 70E as shown in FIG. First, in the first setting step 70A, a reference plane 40 that is a plane perpendicular to the pressing direction in the main forming process 2B is assumed. Then, polygonal single shapes 40A are arranged so as to be continuously aligned on the reference plane 40. In this way, the reference plane 40 is set as a plane partitioned by a repetition of a plurality of the single shapes 40A.

[0064] At this time, in the first setting step 70A, it is preferable to set the single shape 40A to a quadrangle shape. Then, the reference plane 40 is partitioned by grid-like lines to arrange a plurality of single shapes 40A. In this way, it is preferable to partition the reference plane 40 by a plurality of single shapes 40A. In this case, it is possible to simply and easily define the reference plane 40 consisting of a plurality of single shapes 40A.

[0065] Next, in the second setting step 70B, a reference plane 40 is defined by a plurality of single shapes 40A and is made up of the plurality of single shapes 40A. The reference plane 40 is moved in the pressing direction toward the target shape, and a state in which it intersects with the target shape is assumed. Then, the surface of the target shape is divided by division lines 42 formed by intersecting each side of each single shape 40A with the target shape. Next, in a third setting step 70C, three or more nodes are placed on each of the division lines 42 corresponding to each side of each single shape 40A. The three or more nodes are placed at equal intervals when viewed from the pressing direction. Next, in a fourth setting step 70D, the multiple nodes aligned along the extension direction of each division line 42 are connected to each other, thereby setting multiple smooth curves 43.

[0066] Next, in a fifth setting step 70E, a surface shape is formed by smoothly stretching a surface in each area surrounded by the set plurality of curves 43. The surface shape is set as a preform shape. Next, in the shape evaluation step 70F, the preforming shape set in the fifth setting step 70E is set as the preforming shape. Then, forming analysis of the preforming and main forming is performed. If it is determined that cracks will occur, the conditions are changed and then the process proceeds to the second setting step 70B. Then, the second setting step 70B to the fifth setting step 70E are repeatedly executed until the cracks are eliminated.

[0067] The program consisting of the above steps can be created by a known forming analysis method using a computer-aided CAE. Examples of inputs to the program include the target shape and the material properties of the target metal plate.

[0068] (Method of manufacturing press-molded products) The method for manufacturing a press-formed product of this embodiment includes a preformed shape design step 1, a preformed step 2A, and a main forming step 2B. In the preform shape design step 1, the preform shape is determined by the preform shape design method described above. In the preforming step 2A, a metal plate is press-formed into a desired preform shape to manufacture the intermediate part 10. In the main forming step 2B, the intermediate part 10 having the preform shape is press-formed into a target shape. By the above-described processing, a preformed shape can be designed in a simple manner, and a press-formed product that is free from cracks can be produced more reliably.

[0069] "others" The present disclosure may also have the following configuration. (1) A method for designing a preformed shape when manufacturing a press-formed product having a target shape by press working including a preformed process for press-forming a metal plate into a preformed shape and a main forming process for press-forming an intermediate part having the preformed shape into a target shape, comprising: a position identification process for identifying a crack occurrence position where a crack is estimated to occur in a press-formed product when the metal plate is press-formed to the bottom dead center by a die capable of forming the metal plate into the target shape in one press forming operation; A first surface area calculation step of calculating a surface area A1 located in a first region within a preset distance L0 from the crack occurrence position in the target shape; a basic shape setting step of setting a basic shape of the preformed shape based on the target shape; A second surface area calculation step of calculating a surface area A2 located within a second region within the distance L0 from a position corresponding to the crack occurrence position in the basic shape; a basic shape deformation step of deforming the basic shape so as to satisfy the following formula (1); A method for designing a preformed shape comprising: 0.9×A1 <A2<1.1×A1 ··(1)

[0070] (2) The basic shape setting process sets one forming shape selected from a plurality of forming shapes which are the forming shapes in the middle of forming the metal plate to the bottom dead center in the die and before the crack occurs as the basic shape of the preformed shape. (3) the position identifying step includes identifying a position where the crack is expected to occur by a computer-based forming analysis of press-forming the metal plate into a target shape; The basic shape setting process involves a computer-aided forming analysis of the press forming of a metal plate into a target shape, in which the formed shape before cracks occur is determined.

[0071] (4) The basic shape setting process is A single polygonal shape is arranged in a continuous line on a reference plane, which is a plane perpendicular to the press direction in this forming process, to divide the reference plane into a plurality of repetitions of the single shape, When the partitioned reference plane is moved in the press direction toward the target shape, each side of each single shape arranged on the reference plane intersects with the target shape to form a division line on the surface of the target shape, dividing the surface of the target shape; Three or more nodes are arranged at a distance from each other on each dividing line corresponding to each side of each of the single shapes; A plurality of smooth curves are set to connect the plurality of nodes arranged along the extending direction of each dividing line, The surface shape formed by applying a smooth surface to each area surrounded by the plurality of curved lines set above is set as the basic shape.

[0072] (5) The single shape is a rectangle, and a plurality of single shapes are arranged on the reference plane by dividing the reference plane with grid-like lines. (6) The interval between adjacent parting lines is set to 1 / 10 or less of the line length of the target shape in the arrangement direction of the adjacent parting lines.

[0073] (7) The basic shape transformation step is For the surface shape within the crack occurrence area, which is an area within the distance L0 from the position corresponding to the crack occurrence position in the above basic shape, the shape of a position at a distance L from the position corresponding to the crack occurrence position is determined using the function P(q, L) expressed by the following equation (2). P(q, L) = q × f(L) (2) Here, f(L) is a function formula that satisfies f(L0)=0, f'(0)=0, and f'(L0)=0.

[0074] (8) The distance L0 is set to a value that can include the entire area of ​​the crack within the first area. (9) When the tensile strength of the material of the metal plate is TS (MPa), the distance L0 is set to a value that satisfies the following formula (3). L0 < 3×TS 0.5 (3)

[0075] (10) If the basic shape after deformation in the basic shape deformation process is used as a preformed shape and the preformed process and main forming process are performed and no crack reduction effect is observed, the basic shape after deformation in the basic shape deformation process is updated to the basic shape, and the second surface area calculation process and the basic shape deformation process are repeatedly performed until a crack reduction effect is observed, thereby designing a preformed shape.

[0076] (11) A method for designing a preformed shape when a press-formed product having a target shape is manufactured by press working including a preformed process for press-forming a metal plate into the preformed shape and a main forming process for press-forming an intermediate part having the preformed shape into a target shape, the method comprising: A single polygonal shape is arranged in a continuous line on a reference plane that is a plane perpendicular to the press direction, thereby dividing the reference plane into a repetition of a plurality of the single shapes, When the partitioned reference plane is moved in the press direction toward the target shape, each side of each single shape arranged on the reference plane intersects with the target shape to form a division line on the surface of the target shape, dividing the surface of the target shape; Three or more nodes are arranged at a distance from each other on each dividing line corresponding to each side of each of the single shapes; A plurality of smooth curves are set to connect the plurality of nodes arranged along the extending direction of each dividing line, The surface shape formed by smoothly stretching a surface in each area surrounded by the set curves is defined as the preformed shape.

[0077] (12) The single shape is a rectangle, and a plurality of single shapes are arranged on the reference plane by dividing the reference plane with grid-like lines. (13) The interval between adjacent parting lines is set to 1 / 10 or less of the line length of the target shape in the arrangement direction of the adjacent parting lines. (14) determining a preformed shape by the preformed shape design method of the present disclosure; A press-formed product having a target shape is manufactured by a press working method including a preforming step of press-forming the metal plate into the preformed shape, and a main forming step of press-forming an intermediate part having the preformed shape into a target shape. A manufacturing method for press-molded products.

[0078] (15) When a metal plate is press-formed into a target shape in a single press-forming operation, cracks occur in the press-formed product. Therefore, a pre-forming process for press-forming the metal plate into a pre-formed shape and a main-forming process for press-forming the intermediate part of the pre-formed shape into the target shape are provided. A program for causing a computer to execute a design process for obtaining the pre-formed shape when manufacturing a press-formed product of the target shape by press working, In an analysis condition where a metal plate is press-formed into a target shape in a single press-forming operation, a position specifying step of specifying the position where cracks occur by performing a forming analysis up to the bottom dead center of the forming; A first surface area calculating step of obtaining a surface area A1 located within a first region within a set distance L0 from the crack occurrence position specified in the position specifying step in the target shape; A basic shape setting step of temporarily setting a basic shape of the pre-formed shape based on the target shape; A second surface area calculating step of obtaining a surface area A2 located within a second region within the distance L0 from the position corresponding to the crack occurrence position specified in the position specifying step in the basic shape; A basic shape deforming step of deforming the basic shape so that the shape within the second region in the basic shape satisfies 0.9×A1 < A2 < 1.1×A1; A program comprising the above.

[0079] (16) The basic shape setting step uses, as the basic shape, one of the forming shapes during forming up to the bottom dead center obtained by the same forming analysis as the position specifying step and before the occurrence of the crack among a plurality of forming shapes. (17) The basic shape setting step A step of partitioning the reference plane by repeatedly arranging a single shape composed of a polygonal shape so as to be continuous with respect to a reference plane that is a plane orthogonal to the press direction; A step of obtaining a plurality of dividing lines formed on the surface of the target shape by the intersection of each side of each single shape arranged on the reference plane with the target shape when the partitioned reference plane is moved in the press direction toward the target shape; A step of arranging three or more nodes at equal intervals as viewed from the press direction on each of the division lines corresponding to each side of each of the single shapes; A step of setting a plurality of smooth curves by connecting a plurality of nodes arranged along an extension direction of each of the division lines; and setting, as the basic shape, a surface shape formed by smoothly applying a surface to each area surrounded by the set plurality of curved lines.

[0080] (18) The single shape is a rectangle, and a plurality of single shapes are arranged on the reference plane by dividing the reference plane with grid-like lines. (19) The basic shape transformation step includes: For the surface shape within the crack occurrence region, which is the second region within the distance L0 from the position corresponding to the crack occurrence position in the basic shape, the preformed shape at a position distance L from the position corresponding to the crack occurrence position is determined using P(q, L) expressed by the following formula. P(q, L) = q × f(L) Here, f(L) is a function formula that satisfies f(L0)=0, f'(0)=0, and f'(L0)=0. (20) When the tensile strength of the metal plate material is TS (MPa), the distance L0 is set to a value that satisfies the following formula. L0 < 3×TS 0.5

[0081] (21) If it is determined that the effect of reducing cracks is not recognized when the pre-forming process and the main forming process are performed using the basic shape after deformation obtained in the basic shape deformation step as a pre-forming shape, the basic shape after deformation obtained in the basic shape deformation step is updated to the pre-forming shape, and the processing of the second surface area calculation step and the basic shape deformation step is repeatedly performed until the effect of reducing cracks is recognized.

[0082] (22) A program for causing a computer to execute a design process for determining a preformed shape when a press-formed product having a target shape is manufactured by press working including a preformed process for press-forming a metal plate into a preformed shape and a main forming process for press-forming an intermediate part having the preformed shape into the target shape, since cracks will occur in the press-formed product if a metal plate is press-formed into a target shape in one press forming, the program comprising: A step of dividing a reference plane, which is a plane perpendicular to the press direction, into a plurality of repetitions of the single polygonal shapes by continuously arranging the single polygonal shapes on the reference plane; A step of determining a plurality of division lines formed on a surface of the target shape by each side of each single shape arranged on the reference plane intersecting with the target shape when the divided reference plane is moved in a press direction toward the target shape; A step of arranging three or more nodes at equal intervals as viewed from the press direction on each of the division lines corresponding to each side of each of the single shapes; setting a plurality of smooth curves connecting the plurality of nodes arranged along the extending direction of each of the division lines; A step of setting a surface shape formed by smoothly applying a surface to each area surrounded by the set plurality of curves as a preformed shape; A program that includes: (23) The single shape is a rectangle, and a plurality of single shapes are arranged on the reference plane by dividing the reference plane with grid-like lines, thereby arranging a plurality of single shapes on the reference plane. EXAMPLES

[0083] "First embodiment" In the first example, an example based on the first shape setting step in the above-mentioned first embodiment will be described. In this example, the target shape is a shape that imitates a front pillar lower of an automobile, as shown in Fig. 12. A 1180 MPa-class hot-dip galvanized material (sheet thickness 1.2 mm) was used as the metal sheet.

[0084] At this time, when attempting to form the target shape in one press molding, cracks occurred at the positions shown in Figure 12. Therefore, based on the first embodiment employing the first shape setting process, a basic shape 81 serving as the basis for the preformed shape was set as shown in FIG. 13. Then, as shown in FIG. 14, the shape of the basic shape 81 near the crack occurrence position W was changed. The area enclosed in a box is the design portion of the shape. This process was repeated until the crack was eliminated, with the changed basic shape being set as the new basic shape 81, and the process of changing the shape near the crack was executed. In this example, the number of repetitions was four. The final target shape formed result is shown in FIG. 15.

[0085] In this way, it was found that by adopting the design of the preform shape based on the present invention, it is possible to obtain a formed product having a good target shape without the occurrence of cracks. In this way, the use of the present invention makes it possible to easily design the preform shape.

[0086] "Second embodiment" In the second example, an example based on the second shape setting step in the above-mentioned first embodiment will be described. In this example, the preform shape was designed under the same conditions as in the first example, except that the method for setting the basic shape 81 was the second shape setting process. In this case, the preformed shape that eliminated the cracks was obtained after three repetitions. In this way, it was found that by adopting the design of the preform shape based on the present invention, it is possible to obtain a formed product having a good target shape without the occurrence of cracks. In this way, the use of the present invention makes it possible to easily design the preform shape.

[0087] The entire contents of Japanese Patent Application No. 2023-197994 (filed on November 22, 2023), from which this application claims priority, are incorporated herein by reference. Although the present invention has been described with reference to a limited number of embodiments, the scope of the rights is not limited thereto, and modifications of each embodiment based on the above disclosure would be obvious to one skilled in the art. [Explanation of symbols]

[0088] 1 Preform shape design process 2. Press processing 2A Preforming process 2B Main molding process 10 Intermediate parts 11 Press-molded products 20 Location identification process 21 First surface area calculation step 22 Basic shape setting process 23 Second surface area calculation step 24 Basic shape transformation process 25 Shape evaluation process 26 Basic shape resetting process 30 Basic shapes 40 Reference plane 40A single shape 41 Target shape 42 Partition Line 43 Curve 44 Areas enclosed by curves 45 nodes 50 Programs 50A Location Step 50B First surface area calculation step 50C Basic shape setting step 50D Second surface area calculation step 50E Basic shape transformation step 50F Shape evaluation step 60 Preform shape setting process 61 Shape evaluation process 70 Programs 70F Shape evaluation step A1 surface area A2 surface area W Generation position

Claims

1. A method for designing a preformed shape when manufacturing a press-formed product having a target shape by press working including a preformed process for press-forming a metal plate into a preformed shape and a main forming process for press-forming an intermediate part having the preformed shape into a target shape, a position identification process for identifying a crack occurrence position where a crack is estimated to occur in a press-formed product when the metal plate is press-formed to the bottom dead center by a die capable of forming the metal plate into the target shape in one press forming operation; a first surface area calculation step of calculating a surface area A1 located in a first region within a preset distance L0 from the crack occurrence position in the target shape; a basic shape setting step of setting a basic shape of the preformed shape based on the target shape; A second surface area calculation step of calculating a surface area A2 located in a second region within the distance L0 from a position corresponding to the crack occurrence position in the basic shape; a basic shape deformation step of deforming the basic shape so as to satisfy the following formula (1); Equipped with The basic shape setting process includes: A reference plane is a plane perpendicular to the pressing direction in this forming process, and a single shape consisting of a polygonal shape is arranged so as to be continuously arranged in a line, thereby dividing the reference plane into a plurality of repetitions of the single shape, When the partitioned reference plane is moved in the press direction toward the target shape, each side of each single shape arranged on the reference plane intersects with the target shape to form a division line on the surface of the target shape, dividing the surface of the target shape; Three or more nodes are arranged at a distance from each other on each dividing line corresponding to each side of each of the single shapes; A plurality of smooth curves are set to connect the plurality of nodes arranged along the extending direction of each dividing line, A surface shape formed by applying a smooth surface to each area surrounded by the plurality of curved lines is set as the basic shape. How to design preformed shapes. 0.9×A1<A2<1.1×A1...(1)

2. The basic shape setting step is to set one of a plurality of forming shapes, which are formed shapes in the middle of forming the metal plate to the bottom dead center by the die and before the crack occurs, as the basic shape of the preforming shape. A method for designing a preformed shape according to claim 1.

3. The position identifying step identifies a position where the crack is estimated to occur by a forming analysis using a computer for press-forming the metal plate into a target shape, The basic shape setting process involves a computer-aided forming analysis of a metal plate to be press-formed into a target shape, to determine the shape before cracks occur. A method for designing a preformed shape according to claim 2.

4. The single shape is a quadrangle, and a plurality of single shapes are arranged on the reference plane by dividing the reference plane with lines in a grid pattern. A method for designing a preformed shape according to claim 1.

5. A distance between adjacent dividing lines is set to 1 / 10 or less of a line length of the target shape in an arrangement direction of the adjacent dividing lines. A method for designing a preformed shape according to claim 4.

6. The basic shape transformation step includes: Regarding the surface shape within the crack occurrence region, which is a region within the distance L0 from the position corresponding to the crack occurrence position in the basic shape, the shape of the position at a distance L from the position corresponding to the crack occurrence position is determined using a function P(q, L) expressed by the following formula (2): A method for designing a preformed shape according to claim 1. P(q,L)=q×f(L)...(2) Here, f(L) is a function formula that satisfies f(L0)=0, f'(0)=0, and f'(L0)=0.

7. The distance L0 is set to a value that can include the entire crack area within the first area. A method for designing a preformed shape according to claim 1.

8. When the tensile strength of the material of the metal plate is TS (MPa), the distance L0 is set to a value that satisfies the following formula (3): A method for designing a preformed shape according to claim 1. L0<3×TS ０．５ ・・・(3)

9. If the basic shape after deformation in the basic shape deformation process is used as a preformed shape and the preformed process and the main forming process are performed, and the crack reduction effect is not recognized, the basic shape after deformation in the basic shape deformation process is updated to the basic shape, and the second surface area calculation process and the basic shape deformation process are repeatedly performed to design a preformed shape. A method for designing a preformed shape according to claim 1.

10. A method for designing a preformed shape when manufacturing a press-formed product having a target shape by press working including a preformed process for press-forming a metal plate into a preformed shape and a main forming process for press-forming an intermediate part having the preformed shape into a target shape, A single polygonal shape is arranged in a continuous line on a reference plane that is a plane perpendicular to the press direction, thereby dividing the reference plane into a repetition of a plurality of the single shapes, When the partitioned reference plane is moved in the press direction toward the target shape, each side of each single shape arranged on the reference plane intersects with the target shape to form a division line on the surface of the target shape, dividing the surface of the target shape; Three or more nodes are arranged at a distance from each other on each dividing line corresponding to each side of each of the single shapes; A plurality of smooth curves are set to connect the plurality of nodes arranged along the extending direction of each dividing line, The surface shape formed by smoothly stretching a surface in each area surrounded by the multiple curves set is defined as the preformed shape. How to design preformed shapes.

11. The single shape is a quadrangle, and a plurality of single shapes are arranged on the reference plane by dividing the reference plane with lines in a grid pattern. The method for designing a preformed shape according to claim 10.

12. A distance between adjacent dividing lines is set to 1 / 10 or less of a line length of the target shape in an arrangement direction of the adjacent dividing lines. The method for designing a preformed shape according to claim 10.

13. A preformed shape is obtained by a method for designing a preformed shape according to any one of claims 1 to 12, A press-formed product having a target shape is manufactured by a press working method including a preforming step of press-forming the metal plate into the preformed shape, and a main forming step of press-forming an intermediate part having the preformed shape into a target shape. A manufacturing method for press-molded products.

14. A program for causing a computer to execute a design process for determining a preformed shape when a press-formed product having a target shape is manufactured by press working including a preformed process for press-forming a metal plate into a preformed shape and a main forming process for press-forming an intermediate part having the preformed shape into the target shape, since cracks will occur in the press-formed product if a metal plate is press-formed into a target shape in one press forming, a position identification step of identifying a position where a crack will occur by performing forming analysis up to the bottom dead center of forming under analysis conditions for press-forming a metal plate into a target shape in one press forming; a first surface area calculation step of calculating a surface area A1 located in a first region within a set distance L0 from the crack occurrence position identified in the position identification step in the target shape; A basic shape setting step of provisionally setting a basic shape of a preforming shape based on the target shape; a second surface area calculation step of calculating a surface area A2 located within a second region within the distance L0 from a position corresponding to the crack occurrence position identified in the position identification step in the basic shape; a basic shape deformation step of deforming the basic shape so that a shape in the second region of the basic shape satisfies 0.9×A1<A2<1.1×A1; Equipped with The basic shape setting step is as follows: A step of dividing a reference plane, which is a plane perpendicular to the press direction, into a plurality of repetitions of the single polygonal shapes by continuously arranging the single polygonal shapes on the reference plane; A step of determining a plurality of division lines formed on a surface of the target shape by each side of each single shape arranged on the reference plane intersecting with the target shape when the divided reference plane is moved in a press direction toward the target shape; A step of arranging three or more nodes at equal intervals as viewed from the press direction on each of the division lines corresponding to each side of each of the single shapes; A step of setting a plurality of smooth curves by connecting a plurality of nodes arranged along an extension direction of each of the division lines; setting a surface shape formed by applying a smooth surface to each area surrounded by the set plurality of curved lines as the basic shape; Equipped with program.

15. The basic shape setting step sets one of a plurality of formed shapes, which are formed shapes obtained by the same forming analysis as in the position specifying step and are formed to the bottom dead center and before the crack occurs, as the basic shape.

15. The program according to claim 14.

16. The single shape is a quadrangle, and a plurality of single shapes are arranged on the reference plane by dividing the reference plane with lines in a grid pattern.

15. The program according to claim 14.

17. The basic shape transformation step includes: Regarding the surface shape in the crack occurrence region, which is the second region within the distance L0 from the position corresponding to the crack occurrence position in the basic shape, the preformed shape at a position that is a distance L from the position corresponding to the crack occurrence position is determined using P (q, L) expressed by the following formula:

15. The program according to claim 14. P(q,L)=q×f(L) Here, f(L) is a function formula that satisfies f(L0)=0, f'(0)=0, and f'(L0)=0.

18. When the tensile strength of the material of the metal plate is TS (MPa), the distance L0 is set to a value that satisfies the following formula:

15. The program according to claim 14. L0<3×TS ０．５

19. If it is determined that the effect of reducing cracks is not recognized when the preforming process and the main forming process are performed using the basic shape after deformation obtained in the basic shape deformation step as a preforming shape, the basic shape after deformation obtained in the basic shape deformation step is updated to the preforming shape, and the processing of the second surface area calculation step and the basic shape deformation step is repeatedly performed until the effect of reducing cracks is recognized.

15. The program according to claim 14.

20. A program for causing a computer to execute a design process for determining a preformed shape when a press-formed product having a target shape is manufactured by press working including a preformed process for press-forming a metal plate into a preformed shape and a main forming process for press-forming an intermediate part having the preformed shape into the target shape, since cracks will occur in the press-formed product if a metal plate is press-formed into a target shape in one press forming, A step of dividing a reference plane, which is a plane perpendicular to the press direction, into a plurality of repetitions of the single polygonal shapes by continuously arranging the single polygonal shapes on the reference plane; A step of determining a plurality of division lines formed on a surface of the target shape by each side of each single shape arranged on the reference plane intersecting with the target shape when the divided reference plane is moved in a press direction toward the target shape; A step of arranging three or more nodes at equal intervals as viewed from the press direction on each of the division lines corresponding to each side of each of the single shapes; A step of setting a plurality of smooth curves by connecting a plurality of nodes arranged along an extension direction of each of the division lines; A step of setting a surface shape formed by smoothly applying a surface to each area surrounded by the set plurality of curves as a preformed shape; A program that includes:

21. The single shape is a quadrangle, and a plurality of single shapes are arranged on the reference plane by dividing the reference plane with lines in a grid pattern, thereby arranging the plurality of single shapes on the reference plane.

21. The program according to claim 20.

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