Design method for press forming process, design apparatus, program, and method for manufacturing press-formed products.

Abstract

The present invention aims to provide a method for designing a press forming process, a design apparatus, a program, and a method for manufacturing a press-formed product, which enable the press forming process to be designed in a shorter time than conventional methods and which can avoid insufficient load applied to the workpiece during press forming. [Solution] A press forming process design method according to one aspect of the present invention is a press forming process design method in which a press machine performs multiple presses on a workpiece, wherein the press forming load, which is the load required for press forming for each of the multiple presses, is calculated based on the area or length of each ridge and the area of ​​each flat surface formed on the workpiece in each of the multiple presses, and the press forming conditions are set.

Description

[Technical Field]

[0001] The present invention relates to a design method, design apparatus, and program for press forming processes, and to a method for manufacturing press-formed products. [Background technology]

[0002] In press forming of metal sheets, it is important to press form them into the desired shape.

[0003] Patent Document 1 discloses a press forming method for easily manufacturing vehicle body parts with reduced springback and excellent shape retention properties by press forming, wherein in multiple press forming steps, the die clearance in areas corresponding to at least a portion of the already formed parts in the intermediate molded product is made larger than the material sheet thickness. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-163416 [Overview of the project] [Problems that the invention aims to solve]

[0005] In press forming of high-tensile steel sheets, due to the high tension, even when the upper limit load of the press machine is applied to the steel sheet, it may not be possible to push it all the way to the bottom dead center, and the forming may be completed before reaching the bottom dead center. In this case, a press-formed body of the desired shape cannot be obtained. Patent Document 1 does not disclose anything about presses that take the upper limit load into consideration.

[0006] If a press-formed part with the desired shape cannot be obtained, the press forming process needs to be redesigned. Traditionally, redesigning the press forming process has involved calculating the forming load using FEM analysis or measuring the forming load using the press machine; however, these methods require a long time to redesign the press forming process.

[0007] Possible measures to avoid insufficient load include subdividing the press-formed parts, using low-strength materials, or increasing the size of the press machine. However, subdividing the press-formed parts requires many press-formed parts to manufacture the finished product. Using low-strength materials requires increasing the plate thickness to obtain the desired strength, thus increasing the weight. Increasing the size of the press machine requires a significant initial investment.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a method for designing a press forming process, a design apparatus, a program, and a method for manufacturing a press-formed product, which can design a press forming process in a shorter time than conventional methods and can avoid insufficient load applied to the workpiece during press forming. [Means for solving the problem]

[0009] The gist of this invention is as follows: [1] A press forming process design method according to one aspect of the present invention is a press forming process design method for which a press machine performs multiple presses on a workpiece, wherein the press forming load, which is the load required for press forming for each of the multiple presses, is calculated based on the area or length of each ridge and the area of ​​each flat surface formed on the workpiece in each of the multiple presses, and the press forming conditions are set. [2] The press forming process design method described in [1] above may be modified by changing the amount of processing on the ridge line for each press so that the load applied when pressing the workpiece is less than or equal to the upper limit load. [3] The press forming process design method described in [1] or [2] above may be modified to change the ridge line portion to be formed for each press, so that the load applied when pressing the workpiece is less than or equal to the upper limit load. [4] The design method for the press forming process described in any of [1] to [3] above is the load F for each press. i The following equation (1) is satisfied, and the total load F of two or more of the above presses is satisfied. s The following equation (2) may also be satisfied. Fi =F ri +F hi …Equation (1) F s =F rs +F hs …Equation (2) Here, in the above Equation (1), F ri is the F represented by the following Equation (3), riA or the F represented by the following Equation (4), riL and F hi is represented by the following Equation (5), In the above Equation (2), F rs is the F represented by the following Equation (6), rsA or the F represented by the following Equation (7), rsL and F hs is represented by the following Equation (8), F riA =A ri ×α …Equation (3) F riL =L i ×γ …Equation (4) F hi =A hi ×β …Equation (5) F rsA =A rs ×α …Equation (6) F rsL =L s ×γ …Equation (7) F hs =A hs ×β …Equation (8) F i : Load per press (kgf) F ri : Load acting on the ridge line per press (kgf) F hi : Load acting on the flat surface per press (kgf) F riA : Load acting on the ridge line per press based on the area of the ridge line (kgf) F riL : Load acting on the ridge line per press based on the length of the ridge line (kgf) F s : Total load (kgf) acting on the press in two or more stages F rs : Total load (kgf) acting on the ridge line formed by pressing in two or more stages. F rsA : The total load (kgf) acting on the ridge formed by pressing in two or more stages, based on the area of ​​the ridge mentioned above. F rsL : The total load (kgf) acting on the ridge formed by pressing in two or more stages, based on the length of the ridge mentioned above. F hs : Total load (kgf) acting on a flat surface due to pressing on two or more stages A ri : Area of ​​the ridge line for each of the above presses (mm 2 ) A rs : Total area of ​​the ridge formed by pressing in two or more stages (mm²) 2 ) L i : Length of the ridge line for each of the above presses (mm) L s : Total length (mm) of the ridge formed by pressing in two or more stages. A hi : Area of ​​the flat surface for each of the above presses (mm²) 2 ) A hs : Total area of ​​the flat surface formed by pressing in two or more stages (mm²) 2 ) α, β: Load coefficient (kgf / mm²) 2 ) γ: Load factor (kgf / mm) That is the case. [5] In the press forming process design method described in any of [1] to [4] above, the workpiece may be a metal plate with a tensile strength of 440 MPa or more.

[0010] [6] Another design apparatus according to the present invention is a design apparatus for a press forming process in which a press machine presses a workpiece in a plurality of stages, and comprises a control unit that calculates the press forming load, which is the load required for press forming for each press, based on the area or length of each edge portion and the area of ​​each flat portion formed on the workpiece in each of the plurality of presses, and sets the press forming conditions.

[0011] [7] Another aspect of the present invention is a program for designing a press forming process in which a press machine performs multiple presses on a workpiece, and which calculates the press forming load required for each press based on the area or length of each ridge and the area of ​​each flat surface formed on the workpiece in each of the multiple presses, and sets the press forming conditions.

[0012] [8] Another embodiment of the present invention relates to a method for manufacturing a press-formed article, which includes a press-forming step designed by any of the press-forming step design methods described in [1] to [5] above. [Effects of the Invention]

[0013] According to the above-described aspect of the present invention, the press forming process can be designed in a shorter time than conventional methods, and insufficient load can be applied to the workpiece during press forming. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram illustrating the upper limit load when press-forming a workpiece using a transfer press. [Figure 2] This is a perspective view showing an example of a press-formed product. [Figure 3] This is a cross-sectional view AA in Figure 2. [Figure 4] This graph shows an example of the relationship between the area of ​​the ridge and the forming load on the ridge in a press-formed product. [Figure 5]This is a schematic diagram of the process of press-forming a workpiece into a hat shape. [Figure 6] This graph shows an example of the relationship between the unit load required to form the edge of a press-formed product and the sheet thickness. [Figure 7] This graph shows an example of the relationship between the length of the ridge and the forming load on the ridge in a press-formed product. [Figure 8] This flowchart shows the design flow of the press forming process according to the press forming process design method according to this embodiment. [Figure 9] This is a schematic diagram illustrating the changes in the amount of machining required for the ridge lines at each stage. [Figure 10] This is a schematic diagram illustrating how to modify the ridge lines planned for molding at each stage. [Figure 11] This is a schematic block diagram showing a specific example of the functional configuration of a press forming process design device. [Figure 12] This is a schematic diagram of the shapes of the intermediate and final products at each stage in Example 1. [Figure 13] This graph shows the initial setting load for each stage in Example 1 and the modified setting load in Example 1 of the present invention. [Figure 14] This is a schematic diagram of the shapes of the intermediate and final products at each stage in Example 2. [Figure 15] This graph shows the initial load settings for each stage in Example 2 and the modified initial load settings in Example 2 of the present invention. [Figure 16] This is a schematic diagram of the shapes of the intermediate and final products at each stage in Example 3. [Figure 17] This graph shows the initial load settings for each stage in Example 3 and the modified load settings in Example 3 of the present invention. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the examples described below. Furthermore, the dimensions and proportions of each component in the drawings do not represent the actual dimensions and proportions of each component.

[0016] A press forming process design method according to one embodiment of the present invention is a press forming process design method that performs multiple presses on a workpiece using a press machine. In the press forming process design method according to this embodiment, the press forming load, which is the load required for press forming, is calculated based on the area of ​​each edge and the area of ​​the flat surface formed on the workpiece in each of the multiple presses, and the edge to be formed on the workpiece is determined for each press. The press forming process design method according to this embodiment will be described in detail below, with a transfer press machine as an example of a press machine.

[0017] Figure 1 is a schematic diagram illustrating the upper limit load when press-forming a workpiece using a transfer press. Figure 2 is a perspective view showing an example of a press-formed body. Figure 3 is a cross-sectional view AA of Figure 2.

[0018] As shown in Figure 1, the transfer press machine 1 has multiple stages 11A to 11F arranged in the direction of the workpiece's movement, each of which is equipped with a pair of dies 12A to 12F, consisting of an upper die 121 and a lower die 122. Each die 12A to 12F in each stage 11A to 11F is different from the others. The workpiece is fed from upstream to downstream in the transfer press machine 1 and pressed by the dies 12A to 12F located in each stage 11A to 11F. In Figure 1, the workpiece is sequentially pressed by the dies 12 from the first stage 11A to the sixth stage 11F, producing a press-formed body having ridges and flat surfaces. The ridges are the parts with curvature, which are intentionally bent. The flat surfaces refer to the parts of the workpiece other than the ridges. For example, a press-formed body having ridge sections 221A, 221B, 231A, 231B, 24, 25 and flat sections 21, 222A, 222B, 222C, 232A, 232B, 232C, as shown in Figure 2, is manufactured, and each ridge section has curvature, as exemplified by ridge section 231B in Figure 3. Details of the press-formed body 2 shown in Figure 2 will be described later.

[0019] In the transfer press machine 1, a first upper limit load F is set for each of the loads applied to the workpiece in each stage 11A to 11F. Ui This is defined. In Figure 1, F is defined for each of the stages from Stage 11A to Stage 611F. UiA ~F UiF It is stipulated that the transfer press machine 1 has a second upper limit load F that it can simultaneously load. Ut It is defined as F ut ≦ΣF Ui Furthermore, depending on the transfer press machine, there is a third upper limit load F, which is the upper limit of the total load of multiple stages. Us It is also defined. In Figure 1, the third upper limit load F is the load that can be applied simultaneously in the first stage 11A, the second stage 11B, and the third stage 11C. Us1 Furthermore, the third upper limit load F is a load that can be applied simultaneously in the fourth stage 11D, the fifth stage 11E, and the sixth stage 11F. Us2 This is defined. During press forming, in order to apply the load up to the bottom dead center, the first upper limit load F UiA ~F UiF , second upper limit load F Ut , and the third upper limit load F Us1 ~F Us2 The load capacity is determined so as not to exceed the first upper limit load F. UiA ~F UiF , second upper limit load F Ut , and the third upper limit load F Us1 ~F Us2 This is the upper limit load specified for transfer press machine 1. In the following, the third upper limit load F is used. Us1 F Us2 If there is no need to distinguish between them, simply refer to this as the third upper limit load F Us It is stated as follows. Also, the first upper limit load F UiA ~F UiFを If there is no need to distinguish between them, simply refer to them as the first upper limit load F Ui It should be written as follows.

[0020] If the load required for press forming of the workpiece exceeds the upper limit load of the press machine, insufficient load may result, making it impossible to obtain a press-formed body of the desired shape. Therefore, in such cases, it is necessary to change the press forming load, which is the load required for press forming for each press. In the press forming process design method according to this embodiment, if the set load applied to the workpiece exceeds the upper limit load of the press machine, the press forming load, which is the load required for press forming for each press, is calculated based on the area of ​​each ridge and each flat surface formed on the workpiece in each of the multiple presses, and the press forming conditions are changed so that the load is less than or equal to the upper limit load of the press machine. This is explained in detail below.

[0021] Figure 4 is a graph showing an example of the relationship between the area of ​​the ridge and the forming load of the ridge in a press-formed body. The graph in Figure 4 is the result of an investigation conducted on the press-formed body shown in Figure 2. The press-formed body 2 shown in Figure 2 comprises two flat sections 21, vertical wall sections 22 rising from each flat section 21, and a top plate section 23 connecting the two vertical wall sections 22. The flat sections 21 and the vertical wall sections 22 are connected by R sections 24, and the vertical wall sections 22 and the top plate section 23 are connected by R sections 25. The vertical wall section 22 consists of two U-shaped ridge sections 221A and 221B rising from the R sections 24, a flat section 222A surrounded by the ridge sections 221A and the R sections 24, a flat section 222B surrounded by the ridge sections 221B and the R sections 24, and a flat section 222C in the remaining portion. The top plate portion 23 is composed of a circular ridge portion 231A, an elliptical ridge portion 231B, a flat portion 232A surrounded by the ridge portions 231A, a flat portion 232B surrounded by the ridge portions 231B, and a flat portion 232C of the remaining part. R portions 24 and 25 are also ridge portions. The flat portion 21 is also a flat portion. Hereafter, when it is not necessary to distinguish between the ridge portions 221A and 221B, they may be collectively referred to as the first ridge portion 221. The first ridge portion 221 includes both the ridge portions 221A and 221B. Also, when it is not necessary to distinguish between the ridge portions 231A and 231B provided on the top plate portion 23, they may be collectively referred to as the second ridge portion 231. Furthermore, the R-shaped section 25 connecting the vertical wall section 22 and the top plate section 23 may be referred to as the third ridge section 25, and the R-shaped section 24 connecting the flat section 21 and the vertical wall section 22 may be referred to as the fourth ridge section 24.

[0022] The workpiece that makes up the press-formed body shown in Figure 2 is a steel plate with a tensile strength of 980 MPa and a thickness of 1.0 mm.

[0023] <Relationship between ridge area and ridge load> Figure 4 shows a graph illustrating the relationship between the area of ​​each press-formed ridge and the applied load. In Figure 4, the workpiece is press-formed by dies in three stages. The two plots for the first ridge 221 in Figure 4 represent the area and press load of ridge 221A, and the area and press load of ridge 221B, respectively. The first ridge 221 is formed by the die in the third stage. The two plots for the second ridge 231 in Figure 4 represent the area and press load of ridge 231A, and the area and press load of ridge 231B, respectively. The second ridge 231 is formed by the die in the second stage. The plot for the third ridge 25 in Figure 4 represents the area and press load of the R section 25. The third ridge 25 is formed by the die in the first stage. As shown in Figure 4, the first ridge section 221, the second ridge section 231, and the third ridge section 25 all have a certain relationship with the area of ​​each ridge section 221, 231, and 25, and it can be seen that the load required to form them increases accordingly. Furthermore, it can be seen that the relationship between the area of ​​the ridge section and the applied load, in other words, the approximation line, differs depending on the part being press-formed. Specifically, when forming the press-formed body 2 shown in Figure 2, the unit load required to form the second ridge section 231 per unit area is the largest, followed by the unit load required to form the first ridge section 221, and the unit load required to form the third ridge section 25 is the smallest. These findings are the first to be obtained by the inventors. The fourth ridge section is formed by the first and third stage molds, but in these molds, there are parts where two types of ridges overlap during press-formation, and these are not plotted.

[0024] As described above, since the load required to form the ridge is in a constant relationship with the area of ​​the ridge, the load acting on the ridge for each press (ridge load) F is calculated based on the area of ​​the ridge. riA Area A of the ridge ri And, using the coefficient (load factor) α, it is expressed by the following equation (101). F riA =A ri×α … Equation (101)

[0025] The value of the coefficient α varies depending on the tensile strength of the workpiece, the plate thickness, the radius of curvature of the ridge line portion, and the angle of the surface on which the ridge line portion is formed with respect to the moving direction of the mold (pressing direction). The angle of the surface on which the ridge line portion is formed with respect to the moving direction of the mold will be described. FIG. 5 is a schematic view when the workpiece is press-worked into a hat shape. FIG. 5 shows a press molding body 2 including an upper mold 121 that relatively moves vertically with respect to a lower mold 122 and having a top plate portion 23 formed horizontally and a vertical wall portion 22 formed inclined with respect to the vertical direction. For example, the angle of the top plate portion 23 is 90° with respect to the moving direction of the mold 12, and the angle of the surface on which the ridge line portion is formed is θ° with respect to the moving direction of the mold. The value of the coefficient α varies depending on the angle of the surface on which the ridge line portion is formed with respect to the moving direction of the mold.

[0026] Since the value of the coefficient α varies depending on the tensile strength of the workpiece, the plate thickness, the radius of curvature of the ridge line portion, and the angle of the surface on which the ridge line portion is formed with respect to the moving direction of the mold, a correction coefficient (strength correction coefficient) based on the tensile strength of the workpiece is R s , a correction coefficient (plate thickness correction coefficient) based on the plate thickness is R t , a correction coefficient (radius of curvature correction coefficient) based on the radius of curvature of the ridge line portion is R r , and a correction coefficient (angle correction coefficient) based on the angle of the surface on which the ridge line portion is formed with respect to the moving direction of the mold is R θ . Further, when a reference unit load is a base unit load F a , the coefficient α is expressed by the following equation (102). α = F a ×R s ×R t ×R r ×R θ … Equation (102)

[0027] Here, the base unit load F a can be arbitrarily set. For example, when the tensile strength of the workpiece, the plate thickness of the workpiece, the angle of the surface on which the ridge line portion is formed with respect to the pressing direction, and the radius of curvature of the ridge line portion are set to specific values, the load at that time can be used as the base unit load F a .

[0028] Referring to FIG. 6, the plate thickness correction coefficient R t will be further described. FIG. 6 is a graph showing the relationship between the unit load required to form a predetermined ridge line portion in a workpiece having a predetermined tensile strength and the plate thickness of the workpiece. From the plot of the unit load for each plate thickness shown in FIG. 6, an approximate formula for the relationship between the plate thickness t and the unit load f under the above conditions can be obtained. Taking the unit load when the plate thickness is 1.0 mm as the base unit load F a and assuming so, from the above approximate formula, the plate thickness correction coefficient R t is such that R t = f / F a is expressed as. ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Intensity correction factor R s The multiple tensile strength values ​​used when calculating this are not particularly limited and should be calculated according to the tensile strength of the workpiece to be press-formed. Strength correction factor R s For example, it can be calculated for tensile strengths in the range of 440 to 2000 MPa. In other words, for example, an approximate formula can be created from the relationship between multiple tensile strengths and unit loads within the range of 440 to 2000 MPa. Strength correction factor R s The range of tensile strength values ​​used when calculating may be 1470 MPa or less.

[0032] Radius of curvature correction coefficient R r The values ​​of the multiple radii of curvature used when calculating this are not particularly limited and should be calculated according to the radius of curvature of the ridge being formed. Radius of curvature correction coefficient R r For example, the radius of curvature of the ridge can be calculated in the range of 1 to 50 mm. In other words, for example, an approximate formula can be created from the relationship between multiple radii of curvature within the range of 1 to 50 mm of the ridge and the unit load. Radius of curvature correction coefficient R r The range of values ​​for the radius of curvature used when calculating this may be 5 mm or more, or 30 mm or less.

[0033] Angle correction coefficient R θ The values ​​of the multiple angles used when calculating this are not particularly limited and should be calculated according to the angle of the surface on which the ridge is formed relative to the pressing direction. Angle correction coefficient R θ For example, the angle correction coefficient R can be calculated within the range of 0 to 70°, with the mold movement direction set to 0°. In other words, for example, an approximate formula can be created from the relationship between multiple angles within the range of 0 to 70° relative to the mold movement direction and a unit load. θ The range of angle values ​​used when calculating may be 30° or less.

[0034] <Relationship between ridge length and ridge load> The load required to form a ridge line has a certain relationship with the length of the ridge line. Here, the length of the ridge line refers to the length of the line connecting the centers of the ridge line when viewed in a cross section perpendicular to the direction of extension. Ridge lines can be convex, concave, or a combination of convex and concave sections. When a ridge line is a combination of convex and concave sections, the total length of the ridge line is the sum of the lengths of the convex and concave sections. Figure 7 is a graph showing an example of the relationship between the length of a ridge line and the forming load of a press-formed body. The graph in Figure 7 is the result of a study conducted on the press-formed body shown in Figure 2. Figure 7 shows a graph showing the relationship between the length of each press-formed ridge line and the applied load. As shown in Figure 7, it can be seen that the load required to form the ridge line increases in proportion to the length of the ridge line. Furthermore, it can be seen that the relationship between the length of the ridge line and the applied load, or in other words, the approximation line, differs depending on the part being press-formed. In detail, when press-forming the press-formed body 2 shown in Figure 2, the unit load required to form the second ridge portion 231 per unit length is the largest, followed by the unit load required to form the first ridge portion 221, and the unit load required to form the third ridge portion 25 is the smallest. These findings are the first to be obtained by the inventors.

[0035] Since the load required to form the ridge line has a constant relationship with the length of the ridge line, the load acting on the ridge line for each press (ridge line load) F is calculated based on the length of the ridge line. riL The length of the ridge section is L. i And, using the coefficient (load factor) γ, it is expressed by the following equation (103). F riL =L i ×γ …(103) formula

[0036] The value of coefficient γ, like coefficient α, varies depending on the tensile strength of the workpiece, the plate thickness, the radius of curvature of the ridge, and the angle of the surface on which the ridge is formed relative to the direction of die movement. Therefore, the reference unit load is the base unit load F. l Therefore, the base unit load F l , intensity correction coefficient R s , plate thickness correction coefficient Rt , radius of curvature correction coefficient R r , and angle correction coefficient R θ Therefore, the coefficient γ is expressed by the following equation (104). γ=F l ×R s ×R t ×R r ×R θ …(104) formula Here, the base unit load F l is the base unit load F a Similarly, it may be set arbitrarily. For example, the base unit load F is the load when the tensile strength of the workpiece, the thickness of the workpiece, the angle of the surface on which the ridge portion is formed relative to the direction of the load acting during press forming, and the radius of curvature of the ridge portion are set to a specific value. l That is acceptable.

[0037] Furthermore, the intensity correction coefficient R s , plate thickness correction coefficient R t , radius of curvature correction coefficient R r , angle correction coefficient R θ As described above, the relationship between the changed factor and the unit load is determined by changing one of the following: the tensile strength of the workpiece, the thickness of the workpiece, the radius of curvature of the formed edge, or the angle of the surface on which the edge is formed relative to the direction of movement of the die, and then calculating the strength correction coefficient R s , plate thickness correction coefficient R t , radius of curvature correction coefficient R r , or angle correction coefficient R θ You just need to calculate that.

[0038] Up to this point, we have explained the load required to shape the ridge. The ridge load F is based on the area of ​​the ridge. riA and the ridge load F based on the length of the ridge. riL If there is no need to distinguish between them, simply refer to them as ridge load section F ri It should be written as follows.

[0039] Next, we will explain the load acting on the workpiece in each stage 11A to 11F. Load F in each stage 11A to 11F i This is the load applied to form the ridge (ridge load) F riand the load applied to form the flat surface (flat surface load) F hi This is the sum. Therefore, in each stage, the load F i This can be expressed by the following equation (105). F i =F ri +F hi …(105) formula Here, in equation (105), F i : Load capacity (kgf) on the stage F ri Load acting on the ridge (kgf) F hi Load acting on a flat surface (kgf) That is the case.

[0040] Plane load F hi The area A of the flat surface to be molded is... hi And, using the coefficient (load factor) β, it is expressed by the following equation (106). F hi =A hi ×β …(106) formula

[0041] The coefficient β is the product of the standard unit load in the planar section, the load coefficient in the planar section, and the coefficient used when calculating the load on the ridge section.

[0042] Furthermore, the total press load F in two or more stages of multiple presses. s This can be expressed by equation (107) below. F s =F rs +F hs ...(107) formula Here, in equation (107), F s : Total load capacity (kgf) of the press across two or more stages F rs : Total load (kgf) acting on the ridge line formed by pressing in two or more stages. F hs : Total load (kgf) acting on the flat surface formed by pressing in two or more stages. That is the case.

[0043] Total load F rs Of these, the total load F acting on the ridge portion formed by pressing in two or more stages, based on the area of ​​the ridge portion. rsA This is the total area A of the ridge sections. rs And, using the coefficient α, it can be expressed by the following equation (108). F rsA =A rs ×α …(108) formula

[0044] Also, the total load F rs Of these, the total load F acting on the ridge portion formed by pressing in two or more stages, based on the length of the ridge portion. rsL L is the total length of the ridge section. s And, using the coefficient γ, it can be expressed by the following equation (109). F rsL =L s ×γ …(109) formula

[0045] The total load F acting on a flat surface formed by pressing in two or more stages. hs This is the total area A of the planar parts. hs Using the coefficients β, it can be expressed by the following equation (110). F hs =A hs ×β …(110) formula

[0046] In this embodiment, each load F in each stage 11A to 11F i However, the first upper limit load F in each stage 11 Ui It is set so as not to exceed [a certain value]. Also, the load F in each stage 11 i The total load is the second upper limit load F Ut Load F should not exceed this limit. i This is set. Furthermore, the third upper limit load F Us If a limit is specified, each load F must not exceed this limit. i The third upper limit load F is set. Us The total load is the second upper limit load F Ut It will be set so as not to exceed a certain limit.

[0047] <Flow of the press design process> Figure 8 is a flowchart showing the design flow of a press forming process according to the press forming process design method according to this embodiment. The press forming process design method according to this embodiment includes a press forming condition setting step, a load confirmation step, and a press forming condition determination step.

[0048] In the press forming condition setting process, the press forming conditions are set (step S1). The press forming conditions can be set by known methods, such as FEM analysis or prior studies. In this step, the shape to be formed for each stage and the load F for each stage are set. i These settings are configured.

[0049] Next, the first upper limit load F in each stage Ui And the load F for each stage set in the press forming condition setting process. i In comparison with the second upper limit load F of the transfer press machine Ut Total load F under the set press forming conditions s In comparison with the third upper limit load F Us This is compared with the total load at the corresponding stage (comparison step: step S2). In the comparison step, the load obtained by FEM analysis may be compared with each upper limit load, or the load may be compared with each upper limit load by actually press forming under the set press forming conditions. In the latter case, it is determined whether the load is insufficient by whether or not the desired shape can be formed when the press forming is actually performed.

[0050] In the comparison process, the set load F i The load F is below the first upper limit load. iIf the load corresponding to the second upper limit load and the load corresponding to the third upper limit load calculated from are less than or equal to the second upper limit load and the third upper limit load, respectively (Step S2 / NO), it is decided to press form under these press forming conditions (end). If the set load is greater than either of the upper limits (Step S2 / YES), at least one of the processing amount of the edge section for each stage and the edge section to be formed is changed (condition change process: Step S3). The condition change process is described in detail below.

[0051] Figure 9 is a schematic diagram illustrating the change in the amount of processing of the ridge portion at each stage. Here, we will explain using the case of forming the ridge portion 231B shown in Figure 2 as an example. For example, if we try to form the ridge portion 231B in one stage, the applied load may exceed the first upper limit load at that stage. In this case, the ridge portion 231B is formed in multiple stages so that the applied load is less than or equal to the first upper limit load. Specifically, first, in the preceding stage, the ridge portion is pressed with a load less than or equal to the upper limit load. This load forms a ridge portion 231B' with a shape less pronounced than the desired shape (Figure 9(A)). Then, in a stage after the previous press forming, the previously formed, less pronounced ridge portion 231B' is press-formed to obtain the ridge portion 231B with the desired shape (Figure 9(B)). Since the area of ​​the ridge portion 231B' is smaller than the area of ​​the ridge portion 231B, the forming load for forming the ridge portion 231B' is smaller than the forming load for forming the ridge portion 231B in one stage. This allows the ridge portion 231B' to be press-formed without exceeding the upper load limit. Subsequently, the ridge portion 231B' is press-formed to form the ridge portion 231B, so the press load required for this press-forming is also small, and press-forming can be done without exceeding the upper load limit. In this way, by forming one ridge portion through multiple press-forming processes, press-forming can be done without exceeding the upper load limit, and a press-formed body of the desired shape can be manufactured. In other words, by distributing the amount of processing required for the ridge portion to be formed across multiple press processes so that the calculated load does not exceed the upper load limit, a press-formed body of the desired shape can be manufactured.

[0052] Figure 10 is a schematic diagram illustrating how to change the ridge sections to be formed at each stage. Here, we will explain using the case of forming ridge sections 231A and 231B shown in Figure 2 as an example. For example, if we try to form ridge sections 231A and 231B in one stage, the load may exceed the first upper limit load for that stage. In this case, ridge sections 231A and 231B are formed in different stages so as not to exceed the first upper limit load. For example, ridge section 231A is formed in the earlier stage (Figure 10(A)), and ridge section 231B is formed in the later stage (Figure 10(B)). In this way, by determining the ridge sections to be formed at each stage so as not to exceed the upper limit load, a press-formed body of the desired shape can be obtained. In other words, by distributing the positions of the ridge sections to be formed across multiple pressing processes so that the calculated load does not exceed the upper limit load, a press-formed body of the desired shape can be manufactured.

[0053] Furthermore, by changing both the amount of material processed on the ridge line and the ridge line to be processed for each stage, it is possible to more appropriately determine the press conditions so as not to exceed the upper load limit.

[0054] <Press forming process design equipment> Figure 11 is a schematic block diagram showing a specific example of the functional configuration of a press forming process design apparatus. The press forming process design apparatus 3 is configured using an information processing device. The press forming process design apparatus 3 is configured using information devices such as a personal computer, server device, PLC (Programmable Logic Controller), dedicated equipment, smartphone, tablet, etc. The press forming process design apparatus 3 includes an input / output unit 31, a storage unit 32, and a control unit 33.

[0055] The input / output unit 31 is an input / output interface. The input / output unit 31 receives input for press forming conditions. The input / output unit 31 outputs the comparison result between the load and each upper limit load to an output device (not shown). The input / output unit 31 may be configured using an interface with a bus or cable, or it may be configured using communication equipment. If the input / output unit 31 is communication equipment, it may communicate data with other devices via a network in accordance with the control of the control unit 33. In this case, the communication equipment may be a wireless communication device or a wired communication device.

[0056] The storage unit 32 is configured using a storage device such as a magnetic hard disk drive or a semiconductor storage device. The storage unit 32 stores various data used by the control unit 33.

[0057] The control unit 33 is composed of a processor such as a CPU (Central Processing Unit) and memory (main memory). The processor executes programs in the control unit 33. Note that all or part of the functions of the control unit 33 may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), or FPGA (Field Programmable Gate Array). The program may be recorded on a readable recording medium. A readable recording medium is, for example, a portable medium such as a flexible disk, magneto-optical disk, ROM, CD-ROM, or semiconductor memory device (e.g., SSD: Solid State Drive), or a storage device such as a hard disk or semiconductor memory device built into a computer system. The above program may be transmitted via a telecommunications line. The control unit 33 controls various operations of the press forming process design apparatus 3. For example, the control unit 33 compares the load with each upper limit load.

[0058] The program executed by the control unit 33 includes a design program for designing a press forming process in which a press machine performs multiple presses on a workpiece. This design program calculates the press forming load, which is the load required for press forming for each of the multiple presses, based on the area or length of each ridge and the area of ​​each flat surface formed on the workpiece in each of the multiple presses, and sets the press forming conditions.

[0059] The method for manufacturing a press-formed article includes a press-forming process designed according to the press-forming process design method described above. This allows the press-forming process to be designed in a shorter time than conventional methods, and enables the acquisition of a desired shape during press forming.

[0060] The workpiece to be formed by the press forming process is, for example, a metal sheet, and more specifically, a steel sheet or an aluminum sheet. The greater the tensile strength of the workpiece, the easier it is to reach the upper limit of the load that the press machine can handle. Therefore, metal sheets with higher tensile strength can more effectively avoid insufficient load and obtain the desired shape. For this reason, the tensile strength of the workpiece to which this technology can be applied is 440 MPa or higher, and more preferably 980 MPa or higher.

[0061] The embodiments of the present invention have been described above. The embodiments described above are merely illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

[0062] For example, the press machine to which the press forming process design method according to this embodiment can be applied is not limited to transfer press machines, but can also be applied to press machines that perform continuous pressing, such as tandem presses and progressive presses.

[0063] Furthermore, the transfer press machine is not limited to the transfer press machine 1 described above; it may have different numbers of stages, etc. [Examples]

[0064] The present invention will be described in more detail below with reference to examples. The examples described below are merely examples of the present invention and do not limit it.

[0065] <Example 1> We designed a press molding process using a transfer press machine with three stages.

[0066] (Example 1 of the present invention) Figure 12 is a schematic diagram of the shapes of the intermediate and final products at each stage in Example 1. Figure 13 is a graph of the initial setting load at each stage in Example 1 and the modified setting load in Example 1 of the present invention. The dashed line in Figure 13 indicates the upper limit load for each stage set on the transfer press machine. At each stage, the initial press forming conditions shown in Table 1 were set so that the intermediate and final products shown in Figures 12(A) to (C) could be obtained. When the setting load (initial setting load) based on these initial press forming conditions was compared with the upper limit load, it was found that the initial setting load exceeded the upper limit load in the third stage. Next, the press forming load, which is the load required for press forming, was calculated based on the area of ​​each ridge and each flat surface, and the modified press forming conditions were determined so that they matched the modified setting load in Example 1 of the present invention, as shown in Table 1. Specifically, as shown in Figures 12(D) to (F), one of the ridges in the four vertical wall sections that were scheduled to be formed in the third stage (Figure 12(C)) was changed to be formed in the second stage (Figure 12(E)). Table 1 shows the set loads after changing the press forming conditions in Example 1 of the present invention.

[0067] (Comparative Example 1) Similar to Example 1 of the present invention, in the third stage, the initial press forming conditions exceeded the upper limit load. Using FEM analysis, the modified press forming conditions were determined so that the modified set load was as shown in Table 1 for Comparative Example 1. Specifically, one of the four ridge sections in the vertical wall section that was scheduled to be formed in the third stage was changed to be formed in the second stage. Table 1 shows the modified set load for Comparative Example 1. In Table 1, "○" indicates that the consideration time was shorter than the time required to set the modified press forming conditions for Comparative Example 1. For Comparative Example 1, "×" is indicated as it is the criterion for evaluating the consideration time.

[0068] [Table 1]

[0069] As shown in Table 1, in the modified press forming conditions of Example 1 and Comparative Example 1 of the present invention, the set load for each stage was less than or equal to the upper limit load (first upper limit load), and the sum of the set loads for all stages was less than or equal to the second upper limit load that the transfer press machine can simultaneously load in stages 1 to 3. Furthermore, the time required to set the modified press forming conditions for Example 1 of the present invention was 1 / 10 of the time required to set the modified press forming conditions for Comparative Example 1.

[0070] <Example 2> Similar to Example 1, a press forming process using a transfer press machine with three stages was designed.

[0071] (Example 2 of the present invention) Figure 14 is a schematic diagram of the shapes of the intermediate and final products at each stage in Example 2. Figure 15 is a graph of the initial setting load at each stage in Example 2 and the modified setting load in Example 2 of the present invention. The dashed line in Figure 15 indicates the upper limit load for each stage set on the transfer press machine. At each stage, the initial press forming conditions shown in Table 2 were set so that the intermediate and final products shown in Figures 14(A) to (C) could be obtained. When comparing the setting load (initial setting load) with the upper limit load, it was found that the initial setting load exceeded the upper limit load at the third stage. Next, the press forming load, which is the load required for press forming, was calculated based on the area of ​​each ridge and each flat surface, and the modified press forming conditions were determined so that they matched the modified setting load in Example 2 of the present invention, as shown in Table 2. Specifically, as shown in Figures 14(D) to (F), one of the ridges in the four vertical wall sections that were scheduled to be formed at the third stage was modified to be formed in stages at the second and third stages. More specifically, in the second stage, a ridge section with a radius of curvature of 14 mm was formed, and in the third stage, the said ridge section was pressed to form a ridge section with a radius of curvature of 7 mm. Table 2 shows the set loads after changing the press forming conditions in Example 2 of the present invention.

[0072] (Comparative Example 2) Similar to Example 2 of the present invention, in the third stage, the initial press forming conditions showed that the initial load exceeded the upper limit. Using FEM analysis, the modified press forming conditions were determined so that the modified load was as shown in Table 2 for Comparative Example 2. Specifically, one of the four ridge sections in the vertical wall section that was planned to be formed in the third stage was modified to be formed in stages 2 and 3. Table 2 shows the modified load for Comparative Example 2. In Table 2, "○" indicates that the consideration time was shorter than the time required to set the modified press forming conditions for Comparative Example 2. For Comparative Example 2, "×" is used as the criterion for evaluating the consideration time.

[0073] [Table 2]

[0074] As shown in Table 2, in the modified press forming conditions of Example 2 and Comparative Example 2 of the present invention, the set load for each stage was less than or equal to the upper limit load (first upper limit load), and the total load applied in all stages was less than or equal to the second upper limit load that the transfer press machine can simultaneously apply in stages 1 to 3. Furthermore, the time required to set the modified press forming conditions for Example 2 of the present invention was 1 / 10 of the time required to set the modified press forming conditions for Comparative Example 2.

[0075] <Example 3> (Example 3 of the present invention) Figure 16 is a schematic diagram of the shapes of the intermediate and final products at each stage in Example 3. Figure 17 is a graph of the initial setting load for each stage in Example 3 and the modified setting load in Example 3 of the present invention. The dashed line in Figure 17 indicates the upper limit load for each stage set on the transfer press machine. In the first stage, the initial press forming conditions shown in Table 3 were set so that the final product shown in Figure 16(A) could be obtained. When the setting load (initial setting load) with these initial press forming conditions was compared with the upper limit load, it was found that the initial setting load exceeded the upper limit load in the first stage. Next, the press forming load, which is the load required for press forming, was calculated based on the area of ​​each ridge and each flat surface, and the modified press forming conditions were determined so that the modified setting load in Example 3 of the present invention, as shown in Table 3, was obtained. Specifically, as shown in Figures 16(B) and (C), the ridges that were planned to be formed in the first stage were changed to be formed in stages over two stages, the first and second stages. More specifically, in the first stage, the ridge section was formed so that a vertical wall section with an angle of 45° with respect to the vertical direction was formed, and in the second stage, the ridge section was pressed to form a vertical wall section with an angle of 10° with respect to the vertical direction. Table 3 shows the set loads after changing the press forming conditions in Example 3 of the present invention.

[0076] (Comparative Example 3) In the first stage, the initial press forming conditions exceeded the upper limit load. Using FEM analysis, the modified press forming conditions were determined to match the modified set load shown in Table 3 for Comparative Example 3. Specifically, the ridge section, which was planned to be formed in the first stage, was modified to be formed in two stages, the first and second stages. The modified set loads are shown in Table 3. In Table 3, "○" indicates that the time required to set the modified press forming conditions was shorter than the time required to set the modified press forming conditions for Comparative Example 3. For Comparative Example 3, "×" is indicated as it is the criterion for evaluating the time required to set the modified press forming conditions.

[0077] [Table 3]

[0078] As shown in Table 3, in the modified press forming conditions of Example 3 and Comparative Example 3 of the present invention, the set load for each stage was less than or equal to the upper limit load (first upper limit load), and the total load applied in all stages was less than or equal to the second upper limit load that the transfer press machine could simultaneously apply in the first and second stages. Furthermore, the time required to set the modified press forming conditions for Example 3 of the present invention was 1 / 10 of the time required to set the modified press forming conditions for Comparative Example 3.

[0079] As described above, by calculating the press forming load, which is the load required for press forming, based on the area of ​​each ridge and each flat surface, and changing the press forming conditions, we were able to shorten the time required for design.

[0080] Furthermore, by calculating the press forming load, which is the load required for press forming, based on the length of each ridge and the area of ​​each flat surface, we were able to shorten the design time even when the press forming conditions were changed. [Explanation of Symbols]

[0081] 2 Press-molded body Stages 11, 11A-11F 21. Planar section 22. Vertical wall section 23 Top Department 24, 25 R section (edge ​​section) 221, 221A, 221B, 231, 231A, 231B Edge section 222A, 222B, 222C, 232A, 232B, 232C Planar Sections

Claims

1. A method for designing a press forming process in which a workpiece is pressed in multiple stages using a press machine, A method for designing a press forming process, comprising: calculating the press forming load, which is the load required for press forming for each of the multiple presses, based on the area or length of each ridge and the area of ​​each flat surface formed on the workpiece in each of the multiple presses, and setting the press forming conditions.

2. A method for designing a press forming process according to claim 1, wherein the amount of processing on the ridge line portion for each press is changed so that the load applied when pressing the workpiece is less than the upper limit load.

3. A method for designing a press forming process according to claim 1 or 2, wherein the ridge line portion to be formed for each press is changed so that the load applied when pressing the workpiece is less than the upper limit load.

4. Load F for each press ｉ The following equation (1) is satisfied, and the total load F of the press in two or more of the multiple stages is satisfied. ｓ A method for designing a press molding process according to claim 1 or 2, wherein the following equation (2) is satisfied. F ｉ =F ｒｉ +F ｈｉ …(1) F ｓ =F ｒｓ +F ｈｓ …(2) Here, in equation (1) above, F ｒｉ is the F represented by the following formula (3) ｒｉＡ , or the F represented by the following formula (4) ｒｉＬ and F ｈｉ This is expressed by equation (5) below, In equation (2) above, F ｒｓ F is expressed by the following equation (6) ｒｓＡ , or F represented by the following formula (7) ｒｓＬ And, F ｈｓ This is expressed by equation (8) below, F ｒｉＡ =A ｒｉ ×α …(3) F ｒｉＬ =L ｉ ×γ …(4) F ｈｉ =A ｈｉ ×β …(5) F ｒｓＡ =A ｒｓ ×α …(6)equation F ｒｓＬ =L ｓ ×γ …(7)equation F ｈｓ =A ｈｓ ×β …(8)equation F ｉ : Load capacity (kgf) for each press F ｒｉ : Load (kgf) acting on the ridge of each press F ｈｉ : Load (kgf) acting on the flat surface of each press F ｒｉＡ : The load (kgf) acting on the ridge portion for each press, based on the area of ​​the ridge portion. F ｒｉＬ : The load (kgf) acting on the ridge portion for each press, based on the length of the ridge portion. F ｓ : Total load (kgf) applied by pressing on two or more stages F ｒｓ : Total load (kgf) acting on the ridge formed by pressing in two or more stages. F ｒｓＡ : The total load (kgf) acting on the ridge portion formed by pressing in two or more stages, based on the area of ​​the aforementioned ridge portion. F ｒｓＬ : The total load (kgf) acting on the ridge portion formed by pressing in two or more stages, based on the length of the aforementioned ridge portion. F ｈｓ : Total load (kgf) acting on the flat surface formed by pressing in two or more stages. A ｒｉ : Area of ​​the ridge portion for each press (mm ２ ) A ｒｓ : Total area of ​​the ridge formed by pressing in two or more stages (mm²) ２ ) L ｉ : Length of the ridge line for each press (mm) L ｓ : Total length (mm) of the ridge formed by pressing in two or more stages. A ｈｉ : Area of ​​the flat portion for each press (mm ２ ) A ｈｓ : Total area of ​​the flat part formed by pressing in two or more stages (mm²) ２ ) α, β: Load coefficient (kgf / mm) ２ ) γ: Load factor (kgf / mm) That is the case.

5. The method for designing a press forming process according to claim 1 or 2, wherein the workpiece is a metal plate having a tensile strength of 440 MPa or more.

6. A design apparatus for a press forming process, which uses a press machine to press a workpiece in multiple stages, A design apparatus comprising a control unit that calculates the press forming load, which is the load required for press forming for each of the multiple presses, based on the area or length of each ridge and the area of ​​each flat surface formed on the workpiece in each of the multiple presses, and sets the press forming conditions.

7. A program for designing a press forming process in which a press machine performs multiple presses on a workpiece, A program that calculates the press forming load required for each press, based on the area or length of each ridge and the area of ​​each flat surface formed on the workpiece in each of the multiple presses, and sets the press forming conditions.

8. A method for manufacturing a press-formed article, comprising a press-forming step designed by the press-forming step design method described in claim 1 or 2.

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