Press-molded article design method, press-molded article design device, and program

Abstract

To provide a press-molded article design method, a press-molded article design device, and a program which, with respect to design and development of a press-molded article, allow the press-molded article with less spring back to be designed in a short time.SOLUTION: The press-molded article design method according to one aspect of the present invention includes the steps of analyzing a press-molded article, generating first stress data having at least one of an in-plane stress component and a bending moment component, segmenting the press-molded article into a plurality of areas and generating second stress data in each of the areas, performing spring back analysis on each piece of decomposed molding data to obtain a shape of the press-molded article after the spring back, obtaining a degree of influence on the spring back of stress in each of the areas, and correcting the stress in each of the areas on the basis of the degree of influence to optimize a deformation of the spring back.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for designing a press-formed body, an apparatus for designing a press-formed body, and a program. [Background technology]

[0002] Many automobile parts, such as doors and bumpers, and home appliance parts, such as refrigerator panels, are manufactured by press-forming metal sheets, such as steel sheets. Press-formed products obtained through press-forming are developed by repeatedly designing and prototyping a mold, press-forming metal sheets using the prototype mold, measuring the dimensions of the obtained press-formed product, and modifying the mold based on the measurement results. Mold design and modification are carried out using the experience of the developer and computer-aided engineering (CAE).

[0003] In recent years, there has been an increasing demand for lighter weight components such as those mentioned above, and efforts have been made to reduce their thickness and weight by using high-strength metal sheets. However, increasing the strength of metal sheets increases their deformation resistance, making them more susceptible to springback due to residual stress generated during press forming.

[0004] As a countermeasure against springback, for example, Patent Document 1 describes a technology in which calculations are repeatedly performed on the plate thickness, elastic modulus, plastic modulus, stress component values, and strain component values ​​in a partial region of a press-formed body by changing a partial region, thereby identifying the value at which springback is minimized or the region and value at which the difference in springback before and after calculation is maximized.

[0005] Furthermore, Patent Document 2 describes a technology for designing a shape for suppressing springback by setting the region where shape change is to be performed, the shape in the shape change, and the target stress magnification in a press-formed body.

[0006] Furthermore, Patent Document 3 describes a technology for identifying the stress that causes deformation by comparing the analysis results of data in which the stress state inside a part is decomposed into in-plane average stress and deviatoric stress with the analysis results of data in which the stress in a press-formed body is compiled after being separated into in-plane average stress and deviatoric stress. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-148838 [Patent Document 2] Japanese Patent Publication No. 2020-42566 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-172677 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology described in Patent Document 1 cannot take into account the springback of the entire press-formed body at once. Furthermore, the technologies described in Patent Documents 1 to 3 only identify the stress that causes springback. These technologies do not suggest a stress correction amount for suppressing springback, and the correction amount must be set subjectively. Therefore, achieving a stress balance that can suppress springback of the entire press-formed body requires repeated trial and error, which can take a long time to consider. Therefore, the technologies described in Patent Documents 1 to 3 have room for improvement.

[0009] The present invention has been made in consideration of the above circumstances, and aims to provide a method for designing a press-formed body, a design device for a press-formed body, and a program that enable a press-formed body with suppressed springback to be designed in a short period of time in the design and development of the press-formed body. [Means for solving the problem]

[0010] The gist of the present invention, which has been made to solve the above problems, is as follows. [1] A design method for a press-formed body according to one embodiment of the present invention includes a press-forming analysis step of performing press-forming analysis by numerical analysis based on the forming conditions of the press-formed body and calculating press-forming analysis data for the press-formed body; a calculation step of dividing the press-formed body into a plurality of regions and performing calculations on first stress data included in the press-forming analysis data of the press-formed body in each region to generate second stress data; a springback analysis step of performing springback analysis by numerical analysis on the first stress data and the second stress data to determine the shape of the press-formed body after springback based on the first stress data and the shape of the press-formed body after springback based on the second stress data; an influence calculation step of determining the influence of the stress of each region on springback calculated from the first stress data and the second stress data; and a correction step of correcting the stress of each region based on the influence to optimize the amount of springback deformation. [2] The design method for a press-formed body described in [1] above further includes an exploded forming data generation step of decomposing at least one of the stress components in each direction across the entire press-formed body for the first stress data into an in-plane stress component and a bending moment component, and generating first exploded forming data having at least one of the in-plane stress component and the bending moment component, wherein in the calculation step, calculations are performed on the first exploded forming data to generate second exploded forming data, and in the springback analysis step and the influence calculation step, the first exploded forming data may be used in place of the first stress data, and the second exploded forming data may be used in place of the second stress data. [3] In the method for designing a press-formed body described in [1] or [2] above, the correction step may correct the stress in each region based on the relationship between the stress in each region and the deformation amount of the springback. [4] In the method for designing a press-formed body described in [3] above, in the correction step, the stress in each region may be corrected based on the relationship between the stress and the springback deformation amount obtained from a plot of the stress and springback amount at two or more points in the range of -70 to 70% of the stress included in the press-forming analysis data. [5] In the method for designing a press-formed body described in [4] above, in the correction step, plots of 0% stress and springback amount relative to the stress contained in the press-forming analysis data may be excluded from the plots used to obtain the relationship. [6] In the method for designing a press-formed body according to any one of [1] to [5] above, the amount of springback deformation at a plurality of evaluation points may be predicted simultaneously based on the stresses in a plurality of regions.

[0011] [7] In addition, a design device for a press-formed body according to another aspect of the present invention includes: a press-formed analysis unit that performs press-forming analysis by numerical analysis based on the forming conditions of the press-formed body and calculates press-forming analysis data for the press-formed body; a calculation unit that divides the press-formed body into a plurality of regions and performs calculations on first stress data included in the press-forming analysis data of the press-formed body in each region to generate second stress data; a springback analysis unit that performs springback analysis by numerical analysis on the first stress data and the second stress data and determines the shape of the press-formed body after springback based on the first stress data and the shape of the press-formed body after springback based on the second stress data; an influence calculation unit that calculates the influence of the stress of each region on springback calculated from the first stress data and the second stress data; and a correction unit that corrects the stress of each region based on the influence to optimize the amount of springback deformation.

[0012] [8] Furthermore, a program according to yet another aspect of the present invention causes a computer to function as: a press forming analysis unit that performs press forming analysis by numerical analysis based on the forming conditions of the press-formed body and calculates press forming analysis data for the press-formed body; a calculation unit that divides the press-formed body into a plurality of regions and performs calculations on first stress data included in the press forming analysis data of the press-formed body in each region to generate second stress data; a springback analysis unit that performs springback analysis by numerical analysis on the first stress data and the second stress data and determines the shape of the press-formed body after springback based on the first stress data and the shape of the press-formed body after springback based on the second stress data; an influence calculation unit that calculates the influence of the stress of each region on springback calculated from the first stress data and the second stress data; and a correction unit that corrects the stress of each region based on the influence to optimize the amount of springback deformation. [Effects of the Invention]

[0013] According to the present invention, a press-formed body with suppressed springback can be designed in a short period of time. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a flowchart of a method for designing a press-formed body according to one embodiment of the present invention. [Figure 2] 1 is a graph schematically showing the relationship between stress and springback amount, for explaining how to determine the influence of stress in each region on springback. [Figure 3] FIG. 1 is a contour diagram of a press-formed body showing the effect of stress in region A on springback at evaluation points 1 and 2. [Figure 4] 1 is a graph schematically showing the relationship between stress and springback amount when press forming is simulated. [Figure 5] 1 is a graph schematically showing the relationship between load and displacement simulating press forming. [Figure 6]1 is a graph schematically showing the relationship between stress and springback amount, for explaining how to determine the influence of stress in each region on springback. [Figure 7] 1A shows an example of the shape of a press-formed body, and FIG. 1B shows a graph of the relationship between the amount of springback (displacement in the Z direction) of the press-formed body and the stress ratio. [Figure 8] 1A shows an example of the shape of a press-formed body, and FIG. 1B shows a graph of the relationship between the amount of springback (displacement in the Z direction) and the stress ratio at evaluation points a and b in the press-formed body. [Figure 9] 10 is an example of a screen displayed by a display unit. [Figure 10] 1 is a flowchart of a method for designing a press-formed body according to an embodiment of the present invention. [Figure 11] 1 is a block diagram showing an example of the functions of a design device for a press-formed body according to an embodiment of the present invention. [Figure 12] FIG. 2 is a block diagram showing an example of a hardware configuration of the design device for a press-molded body according to the embodiment. [Figure 13] FIG. 2 is a diagram showing the shape of a press-formed body and the amount of springback at each evaluation point in the examples. [Figure 14] (A) is a diagram showing the springback amount at each evaluation point after optimization, and (B) is a graph showing the predicted value of the springback amount at each evaluation point after optimization and the analytical value of the springback amount at each evaluation point by CAE analysis that reflects the stress corrected in the correction step. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Design method for press-molded products> Preferred embodiments of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a flowchart of a design method for a press-formed body according to one embodiment of the present invention. The design method for a press-formed body according to the embodiment of the present invention includes a press-forming analysis step, an exploded forming data generation step, a calculation step, a springback analysis step, an influence calculation step, and a correction step.

[0016] (Press forming analysis step) In the press-forming analysis step (step S1), press-forming analysis is performed by numerical analysis based on the forming conditions of the press-formed body, and press-forming analysis data of the press-formed body is calculated.

[0017] Forming conditions include the shape data of the metal plate to be analyzed (plate thickness, length, width, curvature, distortion, etc.), properties (metal type, strength, elongation, etc.), mold shape used for press forming (die and punch shape, curvature, diameter, clearance, lubrication conditions), and press conditions (blanket load, pad load, bead tension, press pressure, temperature).

[0018] The press-forming analysis data is various information related to the press-formed body, such as data including the shape of the press-formed body, stress, strain, plate thickness, and distribution thereof in the press-formed body. Examples of numerical analysis methods include the elastic-plastic finite element method, the rigid-plastic finite element method, the one-step finite element method, and the boundary element method.

[0019] (Calculation steps) In the calculation step (step S3), the press-formed body is divided into a plurality of regions, and second stress data is generated by performing calculations on the first stress data included in the press forming analysis data of the press-formed body for each divided region. The second stress data refers to data obtained after performing calculations on the first stress data for each region.

[0020] The press-formed body may be divided into any desired ranges into any desired regions. For example, the division ranges may be determined based on the curvature and magnitude of stress of the press-formed body obtained through press forming analysis, or may be determined by an operator. Furthermore, the divided regions may be divided to have uniform dimensions based on the shape of the press-formed body, or may be divided to have uniform dimensions in the shape of the plank material before press forming. The divided regions do not have to have uniform dimensions.

[0021] The calculation is performed by multiplying the first stress data in each region by a coefficient (reduction rate) k. The coefficient k may be different for each region.

[0022] (Springback analysis step) In the springback analysis step (step S4), a springback analysis is performed by numerical analysis on the first stress data and the second stress data to determine the shape of the press-formed body after springback (first shape) based on the first stress data and the shape of the press-formed body after springback (second shape) based on the second stress data. In this step, the springback amount of the first shape (first springback amount) and the springback amount of the second shape (second springback amount) are calculated.

[0023] The amount of springback (amount of deformation due to springback) can be the difference in coordinates (= displacement) of an arbitrarily selected node (specific node in finite element data) before and after springback, the difference in angle of a line connecting two arbitrarily selected nodes before and after springback (= twist), the difference in the difference in relative displacement of two arbitrarily selected nodes before and after springback (= relative displacement), or the difference in the angle between a line connecting two arbitrarily selected nodes and a line connecting two other specific nodes before and after springback (= relative twist).

[0024] The amount of springback of the first shape is determined by taking the shape of the press-formed body obtained by press forming analysis as the shape before springback and the first shape as the shape after springback, and taking the difference between them. The amount of springback of the second shape is determined by taking the shape of the press-formed body obtained by press forming analysis as the shape before springback and the second shape as the shape after springback, and taking the difference between them. The shape of the press-formed body before springback is included in the press forming analysis data.

[0025] In springback analysis, the unloading process is calculated using the elastic finite element method, the elastic-plastic finite element method, the one-step finite element method, etc., to determine the shape of the press-formed body after springback. The shape of the press-formed body after springback is obtained as finite element analysis data (data on each element and the node data that make up each element).

[0026] (Impact calculation step) In the influence calculation step (step S5), the influence of stress on springback for each region is calculated. The influence of stress on springback for each region is calculated by comparing the first springback amount with the second springback amount. For example, the influence of stress on one region is calculated by changing the stress in that region while leaving the stress in other regions unchanged. For that region, if the first springback amount based on the first stress data (100% stress) is 27.1 mm, and the second springback amount based on the second stress data when the reduction rate k is 0.4 (40% stress) is 5.5 mm, when the stress in that region is 60% (100-40%) of the first stress data, the springback amount is 21.6 mm. The springback amount calculated by the difference 1-k (=k i ) between the first stress data and the second stress data indicates the influence of stress on springback in that region. In the influence calculation step, an approximation line between stress and springback amount is created from the first stress data, the first springback amount, and a second springback amount using one or more ki (see FIG. 2). FIG. 2 shows an approximation line between stress and springback amount created from the first stress data, the first springback amount, and two second springback amounts using two ki (k1 and k2). However, as will be described later, the first stress data and the first springback amount do not have to be used to create the approximation line (see FIG. 6). Furthermore, if the areas of the divided regions are uneven, the influence per unit area may be calculated by further dividing by the area of ​​the region.

[0027] Furthermore, the calculation of the above-mentioned springback amount is based on springback analysis using fixed points set in the press forming analysis data, but the springback amount varies greatly depending on how the fixed points are selected. Therefore, when calculating the springback influence at a different fixed point, if you perform the above-mentioned influence calculation after aligning (moving and rotating) the fixed point you want to evaluate, you can easily calculate the springback influence at the different fixed point without having to perform forming analysis or springback analysis again.

[0028] By calculating the degree of influence on springback for each divided region, it is possible to determine the distribution of the degree of influence on springback over the entire press-formed body.

[0029] The stress in each region has a different effect on springback at each evaluation point. For example, Figure 3 is a contour diagram of a press-formed body showing the effect of stress in region A on springback at evaluation points 1 and 2. In the example shown in Figure 3, the stress in region A increases the springback amount at evaluation point 1, but increases the springback amount in the opposite direction from evaluation point 1 at evaluation point 2. In other words, the stress in region A increases the springback amount in the positive direction at evaluation point 1, but increases the springback amount in the negative direction at evaluation point 2. Therefore, to suppress the springback amount for the entire press-formed body, it is important to consider the stresses in multiple regions in combination. Therefore, in the correction step described below, it is preferable to simultaneously predict the springback deformation amount at multiple evaluation points based on the stresses in one or more of the multiple regions.

[0030] (Correction step) In the correction step (step S6), the stress in each region is corrected based on the calculated influence to optimize the amount of springback deformation. Specifically, the approximation line created in the influence calculation step is used to determine a design magnification (coefficient mi) that falls within the range of a preset threshold magnification. In the optimization, a region with a large influence is selected, and the stress in the selected region is corrected. The number of selected regions may be one or two or more. Furthermore, the coefficient mi may be a different value for each region.

[0031] Furthermore, in this step, it is preferable to modify the stress in each region based on the relationship between the stress in each region and the amount of springback deformation. As shown in the schematic graph of the relationship between stress and springback in Figure 4, the relationship between stress and springback is not necessarily linear. One possible reason for the non-linear relationship between stress and springback is a discontinuity in the relationship between load and displacement. Figure 5 is a graph schematically showing the relationship between load and displacement simulating press forming. As shown in Figure 5(A), when the load acting on the metal plate is small, the amount of displacement increases in proportion to the load. However, once the load reaches a certain level, as shown in Figure 5(B), the proportional relationship in the low load range deviates and the amount of displacement becomes larger. In other words, once a certain load is reached, deformation progresses in an extremely short time. In a higher load range, the proportional relationship has a different slope from that in the low load range, as shown in Figure 5(C). In this way, the relationship between load and displacement may become discontinuous. This discontinuity may cause the relationship between stress and springback to become non-linear. Therefore, even if the stress is corrected using a straight line connecting the plot of the first springback amount and the corresponding stress, and the plot of the second springback amount and the corresponding stress, it may not be possible to obtain a sufficiently accurate prediction of the springback amount.

[0032] Therefore, in this embodiment, as shown in FIG. 6, it is preferable to perform multiple analyses by changing the coefficient k and changing ki (=1-k), create a relational expression (approximation line) between stress and springback amount based on the results of each analysis, and correct the stress based on this relational expression. Correcting the stress based on the obtained relational expression improves the accuracy of springback prediction. The coefficient ki for creating the relational expression can be determined depending on the press forming conditions, but is preferably greater than -1 and less than 1. In other words, it is preferable to create the relational expression from a plot of stress and springback amount at two or more points in the range of greater than -100% and less than 100% of the stress included in the press forming analysis data. Within this range, a predicted value of springback amount can be obtained with higher accuracy. The coefficient ki for obtaining the relational expression is more preferably greater than -0.7 and less than 0.7 (-70 to 70% of the stress included in the press forming analysis data). FIG. 7 shows an example of the shape of a press-formed body (A) and a graph (B) of the relationship between the springback amount (Z-direction displacement) and stress ratio at evaluation points on the press-formed body. As shown in FIG. 7(B), a nearly linear relationship between stress and springback is confirmed when the corrected stress is within the range of -70 to 70% of the stress (stress ratio) included in the press-forming analysis data. Therefore, by performing multiple analyses with the coefficient ki set to a value between -0.7 and 0.7, prediction accuracy can be further improved. Furthermore, since the actual stress correction amount is larger, the springback amount can be adjusted over a wider range. Therefore, it is preferable to correct the stress in each region based on the relationship between stress and springback deformation obtained from plots of stress and springback amount at two or more points within the range of -70 to 70% of the stress included in the press-forming analysis data. Furthermore, FIG. 8 shows an example of the shape of a press-formed body (A) and a graph (B) of the relationship between springback amount (Z-direction displacement) and stress ratio at evaluation points a and b of the press-formed body. In the example shown in FIG. 8, a nearly linear relationship is confirmed at evaluation point a when the stress ratio is in the range of 0 to 100%, but at evaluation point b, the slope changes at the boundary of a stress ratio of 50%.In such a case, it is preferable that the coefficient ki for obtaining the relational expression is set to be equal to or greater than -0.5 and equal to or less than 0.5 (-50 to 50% of the stress included in the press forming analysis data).More preferably, in order to further improve accuracy, it is preferable to exclude data for which the coefficient ki is 0 from the data for obtaining the relational expression between stress and springback amount.

[0033] FIG. 9 is a schematic table showing the springback amounts that stresses in multiple divided regions exert on multiple evaluation points. FIG. 9 shows the design magnification m1 (calculated design magnification) for the four optimized regions and the springback amounts that stresses in each region exert on the four evaluation points. For example, the design magnification m1 (calculated design magnification) for the stress in region 1 is 0.8 when optimized. In this case, the springback amount at each evaluation point due to stress in region 1 is -0.11 mm at evaluation point 1. The springback amount is then displayed as the sum of the springback amounts at each evaluation point due to stresses in each region, allowing the user to confirm whether the sum is within the desired range. A table like that shown in FIG. 9 is displayed on a display unit, which will be described later. The threshold range for the magnification is a range that is arbitrarily set in advance.

[0034] The following methods can be used as optimization methods. For example, the coefficient mi is changed within an arbitrary numerical range (within the range of the magnification threshold) given for each region, and calculations are repeated to fall within the set springback amount range, and the springback amount determined by the coefficient mi when the total value of the springback amounts at each evaluation point is minimized is determined to be the optimal value. Alternatively, the coefficient mi is changed within an arbitrary numerical range given for each region, and calculations are repeated to fall within the set springback amount range, and the springback amount determined by the coefficient mi when the number of regions other than where the coefficient mi = 1 is minimized is determined to be the optimal value.

[0035] (Decision step) This embodiment may include a determination step. If the total springback amount of all evaluation points is within the desired range (step S7 / YES), pressing may be performed under press-forming conditions that result in a stress distribution that can achieve this. On the other hand, if the total springback amount is not within the desired range (step S7 / NO), the press-forming conditions are changed and steps S6 to S7 are repeated again. In this step, the adoption of the press-forming conditions may be determined based on whether the springback amount for each evaluation point is within the desired range.

[0036] According to this embodiment, the stress in each region is presented so that the amount of springback of the entire press-formed body is optimized, making it possible to design a press-formed body with reduced springback in a short period of time.

[0037] (Decomposition molding data generation step) The above-described design method for a press-formed body uses first stress data included in press-forming analysis data for the press-formed body and second stress data obtained by performing a calculation on the first stress data. However, instead of the first stress data, first resolved forming data having at least one of an in-plane stress component and a bending moment component of the first stress data may be used. The first resolved forming data may be an in-plane stress component or a bending moment component in at least one direction of the first stress data, or may be the in-plane stress component or the bending moment component multiplied by a coefficient greater than 0 and less than 1. In this case, instead of the second stress data, second resolved forming data generated by performing a calculation on the first resolved forming data is used. Therefore, the design method for a press-formed body may include a resolved forming data generation step (step S2, see FIG. 10 ) of decomposing at least one of the stress components in each direction of the first stress data over the entire press-formed body into an in-plane stress component and a bending moment component, and generating first resolved forming data having at least one of the in-plane stress component and the bending moment component. In the resolved molding data generating step, the first resolved molding data may be generated by multiplying an in-plane stress component or a bending moment component in at least one direction of the first stress data by a coefficient greater than 0 and less than 1. Here, the stress components in each direction refer to the x-direction stress σx acting on the x-plane, the y-direction stress σy acting on the y-plane, the z-direction stress σz acting on the z-plane, the y-direction stress τxy acting on the x-plane, the z-direction stress τyz acting on the y-plane, and the x-direction stress τzx acting on the z-plane in a Cartesian coordinate system. The in-plane stress component is the average stress component of the in-plane stress distribution in the thickness direction of the press-formed body, and is calculated by assigning the average stress of the thickness direction distribution to all integration points in the thickness direction for each element in the press forming analysis results. The bending moment component is the deviatoric stress of the in-plane stress distribution in the thickness direction of the press-formed body, i.e., the stress component with a thickness direction distribution obtained by subtracting the average stress component from the stress values ​​at all integration points in the thickness direction generated for each element.

[0038] Here, the decomposition of stress into components in each direction may be performed based on the global coordinate system, or based on a local coordinate system for each element based on the coordinates of the nodes that make up that element. Alternatively, a local coordinate system may be set for each element based on the global coordinate system in the initial state of each element in the press forming analysis, i.e., in the initial blank state in the press, and the stress may be decomposed based on a coordinate system after press forming, which is obtained by moving and rotating this local coordinate system set for each element in accordance with the deformation of each element during press forming.

[0039] When the first resolved molding data is generated, in the calculation step, the stress component of an arbitrarily selected area from the divided areas is multiplied by the following coefficient ai (i = 1 to 6) to generate the second resolved molding data. σx=a1×σx0 …(1) formula σy=a2×σy0 ...Eq. (2) σz=a3×σz0 …(3) formula τxy=a4×τxy0 …(4) formula τyz=a5×τyz0 …(5) formula τzx=a6×τzx0 …(6) formula In the above equations (1) to (6), σx0, σy0, σz0, τxy0, τyz0, and τzx0 represent the stress components before calculation (first resolved forming data) at the integration points of the selected region, and σx, σy, σz, τxy, τyz, and τzx represent the stress components after calculation (second resolved forming data). If there are multiple arbitrarily selected regions, the values ​​of the coefficients ai for each region may be different.

[0040] When the first decomposed molding data and the second decomposed molding data are generated, the springback analysis step and the influence calculation step use the first decomposed molding data instead of the first stress data, and use the second decomposed molding data instead of the second stress data.

[0041] <Press-molded body design device> Next, a design device for a press-formed body according to an embodiment of the present invention will be described. Fig. 11 is a functional block diagram of the design device 1 for a press-formed body according to an embodiment of the present invention. The design device 1 includes a forming condition input unit 11, a press forming analysis unit 12, a resolved forming data generation unit 13, a calculation unit 14, a springback analysis unit 15, an influence calculation unit 16, a display unit 18, a correction unit 17, and a file storage unit 19.

[0042] The forming condition input unit 11 inputs forming conditions such as shape data and properties of the metal sheet to be analyzed, the shape of the die used for press forming, and press conditions to the press forming analysis unit 12 and the springback analysis unit 15. The forming condition input unit 11 can also separately set and input data areas for press forming analysis, data areas for the resolved forming data generation unit 13, data areas for the calculation unit 14, and segmented areas for displaying analysis results on an output screen.

[0043] The press forming analysis unit 12 determines the shape, stress, strain, thickness, etc. of the press-formed body after press forming by the above-mentioned numerical analysis based on the input information from the forming condition input unit 11. The press forming analysis unit 12 outputs the numerical analysis results in the form of variables for the thickness, stress component values, and strain component values ​​of the press-formed body, as well as the distribution of these variables. The press forming analysis data is output to the resolved forming data generation unit 13, the calculation unit 14, the springback analysis unit 15, and the influence calculation unit 16, and is also stored in the file storage unit 19.

[0044] The resolved forming data generation unit 13 resolves at least one stress in each directional component of stress across the entire press-formed body, for the stress data included in the press forming analysis data obtained by the press forming analysis unit 12, into an in-plane stress component and a bending moment component. Then, it generates first resolved forming data having at least one of the in-plane stress component and the bending moment component. The first resolved forming data is output to the calculation unit 14 and the springback analysis unit 15, and is also stored in the file storage unit 19. The resolved forming data generation unit 13 may also generate first resolved forming data by multiplying the in-plane stress component or the bending moment component in at least one direction of the first stress data by a coefficient greater than 0 and less than 1.

[0045] The calculation unit 14 acquires data on the press-formed body from the press-forming analysis data, divides the press-formed body into a plurality of regions, and performs calculations on the first stress data in each divided region to generate second stress data. The calculations are performed for each region, and the resulting second stress data for each region is output to the springback analysis unit 15 and stored in the file storage unit 19. The calculation unit 14 may also determine whether the total springback amount for all evaluation points is within a desired range, or may determine whether the press-forming conditions are acceptable based on whether the springback amount for each evaluation point is within a desired range.

[0046] The springback analysis unit 15 performs a springback analysis by numerical analysis on the first stress data and the second stress data, and determines the shape of the press-formed body after springback (first shape) based on the first stress data and the shape of the press-formed body after springback (second shape) based on the second stress data. As calculation result data, the first shape data and second shape data corresponding to the above-mentioned respective data are output to the influence calculation unit 16 and stored in the file storage unit 19.

[0047] The influence calculation unit 16 calculates the influence on springback for each divided region based on the first shape data and the second shape data. By calculating the influence on springback for each divided region, the influence calculation unit 16 can obtain the distribution of the influence on springback throughout the entire press-formed body.

[0048] The modifying unit 17 modifies the stress in each region based on the degree of influence to optimize the amount of deformation due to springback.

[0049] The display unit 18 outputs various analysis results. The display unit 18 can display the influence of each divided region on springback using a contour. The display unit 18 can display the calculated influences individually or as a contour display for the entire part. The display unit 18 can also display these influences for each stress component. The display unit 18 may also output, for example, the design magnification mi of the stress calculated in each region, the magnification threshold, the amount of springback at each evaluation point due to the stress in the divided region, the calculated displacement at each evaluation point, and the like, as shown in FIG. 9.

[0050] The file storage unit 19 stores data, programs, etc. required for the various analyses described above. The file storage unit 19 also stores data generated or acquired by the design device 1 performing various processes.

[0051] 12 is a schematic block diagram showing an example of the hardware configuration of the design device 1. The design device 1 includes a processor 52, a drive unit 56, an input unit 58, an output unit 60, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 64, an auxiliary storage unit 66, and an interface unit 68. The processor 52, the drive unit 56, the input unit 58, the output unit 60, the ROM 62, the RAM 64, the auxiliary storage unit 66, and the interface unit 68 are interconnected using a bus BS.

[0052] The processor 52, for example, reads out programs and various data stored in the ROM 62 and executes the programs to control the operation of the design device 1. The processor 52 is, for example, a CPU (Central Processing Unit). The processor 52 may execute a predetermined program to realize the functions of the press forming analysis unit 12, the decomposition forming data generation unit 13, the calculation unit 14, the springback analysis unit 15, the influence calculation unit 16, and the correction unit 17. Note that "executing a program" means executing processing instructed by various commands written in the program.

[0053] The storage medium 54 stores various types of data and is, for example, a portable storage medium such as a magneto-optical disk, a flexible disk, or a flash memory.

[0054] The drive unit 56 is, for example, a device that reads various data from the storage medium 54 and / or writes various data to the storage medium 54.

[0055] The input unit 58 is an input device that receives an operation from an operator, generates an operation signal in accordance with the received operation, and outputs the generated operation signal to the processor 52. The input unit 58 corresponds to, for example, a pointing device such as a mouse or a keyboard. The input unit 58 realizes the molding condition input unit 11.

[0056] The output unit 60 includes, for example, a display unit such as a display, and a playback unit such as a speaker. The output unit 60 realizes the display unit 18.

[0057] The ROM 62 stores, for example, a program to be executed by the processor 52.

[0058] The RAM 64 functions as a work area for temporarily storing various data and programs used by the processor 52, for example.

[0059] The auxiliary storage unit 66 is a storage medium such as an HDD (Hard Disk Drive) or a flash memory.

[0060] The interface unit 68 is connected to other devices and allows various data to be input and output, and includes, for example, a communication module for connecting to a network via wire or wirelessly.

[0061] The present invention has been described above using the present embodiment. However, the technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0062] For example, the second resolved molding data may be generated based on data obtained by multiplying the first resolved molding data by an arbitrary coefficient.

[0063] The program for designing a press-molded body can be stored in a computer-readable storage medium and distributed. [Example]

[0064] Next, examples of the present invention will be shown, but the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to the conditions used in the following examples. The present invention can adopt various conditions as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0065] The shape of the press-formed body shown in Figure 13 was modified using the above method to optimize the springback amount. The optimization involved changing the coefficient mi within the range of the coefficient ki given for each region, and iterative calculations were performed to ensure that the springback amount remained within the set range. The springback amount calculated by the coefficient mi when the sum of the springback amounts at each evaluation point was minimized was determined to be the optimal value. In this example, a relationship obtained from plots of stress and springback amount at two or more points within the range of -70 to 70% of the stress contained in the press-forming analysis data was used. The values ​​shown in Figure 13 are the springback amounts (mm) at each evaluation point. Figure 14(A) shows the springback amounts (mm) at each evaluation point when the stress distribution was optimized. Figure 14(B) shows a graph of the predicted springback amounts at each evaluation point after optimization, as well as the analytical values ​​of the springback amounts at each evaluation point obtained by CAE analysis, reflecting the stress corrected in the correction step. As shown in Figure 14(B), the predicted springback amounts were comparable to the analytical values. By applying this method, it was found that the amount of springback could be predicted with high accuracy, eliminating the need for CAE analysis and enabling the design of press-formed bodies to be completed in a short period of time. [Explanation of symbols]

[0066] 1 Design equipment 11 Molding condition input section 12 Press forming analysis section 13. Decomposition molding data generation unit 14 Arithmetic section 15 Springback analysis section 16 Impact calculation part 17 Correction section 18 Display 19 File Storage

Claims

1. a press-forming analysis step of performing a press-forming analysis by numerical analysis based on the forming conditions of the press-formed body and calculating press-forming analysis data of the press-formed body; a calculation step of dividing the press-formed body into a plurality of regions and performing calculations on first stress data included in press forming analysis data of the press-formed body for each region to generate second stress data; a springback analysis step of performing a springback analysis by numerical analysis on the first stress data and the second stress data to determine a shape of the press-formed body after springback based on the first stress data and a shape of the press-formed body after springback based on the second stress data; an influence degree calculation step of calculating an influence degree of the stress of each region on springback calculated from the first stress data and the second stress data; and a correction step of optimizing the amount of springback deformation by correcting the stress in each region based on the degree of influence.

2. The method further includes a resolved molding data generation step of: decomposing at least one of the stress components in each direction of the first stress data into an in-plane stress component and a bending moment component over the entire press-formed body, and generating first resolved molding data having at least one of the in-plane stress component and the bending moment component; In the calculation step, a calculation is performed on the first resolved molding data to generate second resolved molding data, 2. The design method for a press-formed body according to claim 1, wherein in the springback analysis step and the influence calculation step, the first resolved forming data is used instead of the first stress data, and the second resolved forming data is used instead of the second stress data.

3. The method for designing a press-formed body according to claim 1 or 2, wherein the modifying step modifies the stress in each region based on a relationship between the stress in each region and the deformation amount of springback.

4. In the correction step, the stress in each region is obtained from a plot of the stress and the springback amount at two or more points in a range of −70 to 70% of the stress included in the press forming analysis data. The design method for a press-formed body according to claim 3, wherein the stress in each region is corrected based on the relationship between the stress and the springback deformation amount.

5. The method for designing a press-formed body according to claim 4, wherein in the correction step, plots of stress and springback amount at 0% relative to the stress included in the press forming analysis data are excluded from the plots for obtaining the relationship.

6. The method for designing a press-formed body according to claim 1 or 2, further comprising simultaneously predicting the amount of springback deformation at one or more evaluation points based on the stress in one or more of the plurality of regions.

7. a press forming analysis unit that performs press forming analysis by numerical analysis based on the forming conditions of the press-formed body and calculates press forming analysis data of the press-formed body; a calculation unit that divides a press-formed body into a plurality of regions and performs calculations on first stress data included in press forming analysis data of the press-formed body in each region to generate second stress data; a springback analysis unit that performs a springback analysis by numerical analysis on the first stress data and the second stress data, and determines a shape of the press-formed body after springback based on the first stress data and a shape of the press-formed body after springback based on the second stress data; an influence calculation unit that calculates an influence of stress of each region on springback calculated from the first stress data and the second stress data; and a correction unit that corrects the stress in each region based on the degree of influence to optimize the amount of springback deformation.

8. Computer, a press forming analysis unit that performs press forming analysis by numerical analysis based on the forming conditions of the press-formed body and calculates press forming analysis data of the press-formed body; a calculation unit that divides a press-formed body into a plurality of regions and performs calculations on first stress data included in press forming analysis data of the press-formed body in each region to generate second stress data; a springback analysis unit that performs a springback analysis by numerical analysis on the first stress data and the second stress data, and determines a shape of the press-formed body after springback based on the first stress data and a shape of the press-formed body after springback based on the second stress data; an influence calculation unit that calculates an influence of stress of each region on springback calculated from the first stress data and the second stress data; A program for functioning as a correction unit that corrects the stress in each region based on the degree of influence to optimize the amount of springback deformation.

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