Press forming analysis method, press forming crack determination method for press forming material, press forming material manufacturing method, press forming analysis device, and press forming

Abstract

A press forming analysis method according to the present invention comprises: a blank model creation step (S1) for creating a blank model; and a press forming analysis step (S2) for performing press forming analysis using the created blank model, the blank model creation step (S1) including: a blank mesh creation step (S1-1) for creating a finite element mesh constituting the blank model; a grouping step (S1-2) for grouping the finite elements constituting the finite element mesh into a plurality of groups; and a deformation condition setting step (S1-3) in which, for the finite elements of the grouped groups, conditions relating to deformation are set differently for each group.

Description

Technical Field

[0001] The present invention relates to a press forming analysis method based on the finite element method, a press forming crack determination method of a press forming part using the press forming analysis method, a method for manufacturing a press forming part using the press forming crack determination method, a press forming analysis device, and a press forming analysis program. Background Art

[0002] Due to the rising demand for improved fuel efficiency and collision safety brought about by the lightweighting of automobiles, the application of high-tensile steel sheets in automobile bodies is expanding. However, due to its low ductility, high-tensile steel sheets have low formability such as fracture, which has become a problem in their application. For example, even if high-tensile steel is applied, in the case of fracture caused by forming, it is sometimes necessary to change the shape of the component, which becomes an obstacle to the application of high-tensile steel sheets. In this regard, if fracture can be predicted in advance through press forming analysis, it can be dealt with, and high-precision prediction technology based on press forming analysis is pursued.

[0003] However, steel sheets are composed of various metal structures, and the size and direction of crystal grains are also different. The deformation in the steel sheet has an uneven distribution, so there are cases where fracture cannot be predicted. As an analysis of inhomogeneous deformation in the material, in non-patent document 1, an example of using crystal plasticity finite element analysis to predict the generation of void defects in a steel sheet containing ferrite and martensite is recorded. In addition, in non-patent document 2, an example of studying the tensile test of aluminum by crystal plasticity finite element analysis taking into account the crystal orientation is recorded.

[0004] Non-patent document 1: Shigeru Yonemura, “Finite element analysis of deformation and failure at the mesoscale,” Nippon Steel & Sumitomo Metal Corporation Technical Bulletin, No. 410, 2018, pp. 47–56

[0005] Non-patent document 2: Kengo Yoshida, “Forming simulation of thin metal sheets using crystal plasticity theory, Plasticity and Processing, The Japan Society of Plastic Processing, March 2016, Vol. 57, No. 662, p. 38–42

[0006] However, the crystal plasticity finite element analysis applied in Non-Patent Documents 1 and 2 uses very small elements, which results in a huge calculation time, and therefore its application is limited to simple forming analysis such as tensile testing. Summary of the invention

[0007] The present invention is completed to solve the above-mentioned problems, and its purpose is to provide a stamping analysis method that can take into account the non-uniformity of deformation in the metal material (metal material) by the finite element method in stamping using a metal sheet, and can predict cracks in a stamped part (press formed part) with high accuracy. In addition, another purpose of the present invention is to provide a stamping crack determination method that can determine cracks in a stamped part with high accuracy, and a method for manufacturing a stamped part using the stamping crack determination method. In addition, another purpose of the present invention is to provide a stamping analysis device and a stamping analysis program that can perform stamping analysis with high accuracy by the finite element method.

[0008] The first embodiment of the present invention involves a stamping analysis method that is based on a finite element method in which each process is executed by a computer, and includes: a blank model creation process for creating a blank model; and a stamping analysis process for performing stamping analysis using the created blank model, wherein the blank model creation process includes: a blank mesh creation process for creating a finite element mesh constituting the blank model; a grouping process for grouping the finite elements constituting the finite element mesh into a plurality of groups; and a deformation condition setting process for setting deformation-related conditions differently for each group of finite elements in the grouped groups.

[0009] The deformation condition setting step may set mechanical properties or sheet thickness differently for each group.

[0010] The deformation condition setting step may set the element size differently for each group.

[0011] The deformation condition setting step may set different element types for each group.

[0012] When the mechanical properties are set differently, the range of the mechanical properties to be set can be set within the range of dispersion of the mechanical properties of the structures of the metal materials used as the blanks.

[0013] When the mechanical properties are set differently, the range of the mechanical properties to be set can be set within the range of variation of the mechanical properties of the metal material used as the blank.

[0014] It may include: a blank property variation range measuring step, measuring the variation range of the mechanical properties of the metal plate used as the blank, in which the hardness distribution of the metal plate used as the blank is measured, and the range of deviation of the mechanical properties is determined based on the above hardness distribution.

[0015] In the above-mentioned blank property variation range measurement process, the surface roughness of the front and back sides of the metal plate used as the blank can also be measured, and the range of plate thickness can be determined based on the surface roughness of the above-mentioned metal plate, and the plate thickness of the finite element mesh constituting the blank model can be randomly set within the above-mentioned plate thickness range.

[0016] When the plate thickness is set differently, when the plate thickness is set, the plate thickness can be set within a range of ±20% of the plate thickness of the metal material used as the blank.

[0017] It may include: a blank property variation range measuring step, the measuring step measures the range of plate thickness of a metal plate used as a blank, in the blank property variation range measuring step, the surface roughness of the front and back sides of the metal plate used as a blank is measured, and the range of plate thickness is determined based on the surface roughness of the above-mentioned metal plate.

[0018] The second embodiment of the present invention involves a stamping analysis method that is a stamping analysis method based on the finite element method in which each process is executed by a computer, which includes: a blank model creation process, creating a blank model; and a stamping analysis process, using the created blank model to perform stamping analysis, the above-mentioned blank model creation process includes: an area setting process, setting multiple areas on the inner side of the contour line representing the shape of the blank; and a mesh creation process, creating a finite element mesh with different deformation-related conditions, i.e., unit sizes, for each of the set multiple areas.

[0019] The range of the cell size to be set can be set to be equal to or greater than 1 / 2 of the thickness of the metal plate used as the blank.

[0020] The method for determining stamping cracks of a stamped part involved in the present invention uses the stamping analysis method involved in the present invention to perform stamping analysis of the stamped part, and includes: a stamping crack determination step, which determines whether cracks are generated in the stamping of the stamped part based on the forming limit diagram (FLD) of the metal plate used for the stamped part.

[0021] The manufacturing method of stamped parts involved in the present invention is a manufacturing method of stamped parts that suppresses stamping cracks, which includes a stamping crack determination step, a stamping condition adjustment step and a stamping part manufacturing step. The above-mentioned stamping crack determination step determines whether cracks are generated in the stamping of the above-mentioned stamped parts through the stamping crack determination method of the stamped parts involved in the present invention. When it is determined that cracks are generated in the above-mentioned stamping crack determination step, the above-mentioned stamping condition adjustment step changes the stamping conditions (pressforming condition) including the blank shape (blank shape) and the die shape (press forming die shape) in the stamping analysis until it is determined that no cracks are generated in all parts of the stamped part. The stamping part manufacturing step manufactures the stamped parts by stamping the metal plate under the stamping conditions of the stamping analysis when it is determined that no cracks are generated in the above-mentioned stamping condition adjustment step.

[0022] The first embodiment of the present invention involves a stamping analysis device that performs stamping analysis on stamped parts, wherein the device comprises: a blank model creation unit that creates a blank model; and a stamping analysis unit that uses the created blank model to perform stamping analysis, wherein the blank model creation unit comprises: a blank mesh creation unit that creates a finite element mesh that constitutes the blank model; a grouping unit that groups the finite elements that constitute the finite element mesh into a plurality of groups; and a deformation condition setting unit that sets mechanical properties, unit sizes or unit types that are conditions related to deformation to different settings for each group of finite elements.

[0023] The stamping analysis device involved in the second embodiment of the present invention is a stamping analysis device for performing stamping analysis of stamped parts, wherein it comprises: a blank model creation unit for creating a blank model; and a stamping analysis unit for performing stamping analysis using the created blank model, the above-mentioned blank model creation unit comprises: an area setting unit for setting multiple areas inside the contour line representing the shape of the blank; and a mesh creation unit for creating a finite element mesh with different deformation-related conditions, i.e., unit sizes, for each of the set multiple areas.

[0024] The stamping analysis program according to the present invention causes a computer to function as the stamping analysis device according to the first or second aspect of the present invention.

[0025] According to the present invention, in stamping using a metal plate, an appropriate stamping analysis can be performed that takes into account the non-uniformity of deformation within the metal material. In addition, the accuracy of determining stamping cracks during stamping can be improved. Furthermore, stamping cracks are determined based on the results of the stamping analysis of the present invention, and stamping is performed under stamping conditions in which crack countermeasures are implemented, thereby suppressing defects in stamped parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flowchart showing the processing flow of the stamping analysis method involved in the first embodiment.

[0027] Figure 2 This is a flowchart showing the processing flow of another aspect of the stamping analysis method according to the first embodiment.

[0028] Figure 3 This is a flowchart showing the processing flow of the stamping analysis method involved in the second embodiment.

[0029] Figure 4 This is a flowchart showing the processing flow of the stamping analysis method involved in the third embodiment.

[0030] Figure 5This is a block diagram showing the structure of a stamping analysis device according to a fourth embodiment.

[0031] Figure 6 This is a block diagram showing the structure of another form of the stamping analysis device involved in the fourth embodiment.

[0032] Figure 7 This is an explanatory diagram of the shape of the component to be analyzed in Example 1.

[0033] Figure 8 This is an explanatory diagram of the blank mesh in Example 1.

[0034] Fig. 9 This is an explanatory diagram of a state after press forming of an actual component having the same shape as the component to be analyzed in Example 1.

[0035] Fig.10 This is an explanatory diagram of the analysis results of Example 1.

[0036] Fig.11 This is a flowchart showing the processing flow of the stamping analysis method involved in another aspect of the first embodiment.

[0037] Fig.12 This is a flowchart showing the processing flow of the press forming crack determination method involved in another aspect of the second embodiment.

[0038] Fig.13 This is a flowchart showing the process flow of a method for manufacturing a press-formed product according to another aspect of the third embodiment.

[0039] Fig.14 This is an explanatory diagram of a press forming die used in Example 2.

[0040] Fig.15 This is an explanatory diagram of the analysis results of Example 2.

[0041] Fig.16 This is an explanatory diagram of a state after press forming of an actual component having the same shape as the component analyzed in Example 2. DETAILED DESCRIPTION

[0042] [Implementation Method 1]

[0043] Before describing the embodiment, the process of completing the invention will be described. The inventors studied the deformation of the metal material when reproducing the non-uniformity of the deformation in the metal material by finite element analysis.

[0044] Metal materials are formed by the aggregation of multiple grains with the same direction of slip deformation of crystals. It is believed that the difference in the deformation direction of each grain and the difference in its size show the uneven deformation in the metal material. Due to the unevenness of deformation in the metal material, in the metal material, the microscopic strain (strain) is mixed with the small strain. In the metal material with high ductility, the deformation amount until the fracture is large, so the strain distribution caused by the unevenness of deformation in the metal material is small relative to the strain of the metal material as a whole, and will not greatly affect the cracks of the stamped parts. However, in the high-tensile steel plate with low ductility, the strain distribution caused by the unevenness of deformation in the metal material becomes a size that cannot be ignored relative to the strain of the metal material as a whole, and sometimes affects the cracks of the stamped parts. The size of the grain of the metal material is about tens of microns. In contrast, the mesh size of the finite element usually used in the stamping analysis is much larger than a few millimeters, and it is difficult to reproduce the conditions related to the deformation of the grain monomer in the previous stamping analysis.

[0045] Therefore, focusing on the fact that conditions related to the deformation of actual metal materials are determined by the shape, size, and distribution of the grains, in the stamping analysis based on the finite element method, the finite element grids are understood as a collection of grains of about several millimeters, and the conditions related to the deformation are processed according to each finite element grid. Moreover, with regard to the conditions related to the deformation, all finite element grids were previously treated as grids with uniform properties, but by forming a stamping analysis in which non-uniform properties are given to each finite element grid, the deformation of the finite element grid is uneven, and the idea of ​​being able to reproduce the cracks of the stamped parts caused by the uneven deformation in the metal material is obtained. Moreover, the following insight is obtained: when performing a stamping analysis, the finite element grids constituting the blank are grouped, and the conditions related to the deformation are set differently for each group. The present invention is an invention based on this insight, specifically the invention shown in the following embodiments.

[0046] The stamping forming analysis method involved in this embodiment is a method based on the finite element method of executing each process on a computer. Figure 1 As shown, the process includes a blank model creation step (S1) of creating a blank model and a stamping analysis step (S2) of performing stamping analysis using the created blank model. Each step will be described in detail below.

[0047] <Blank model creation process>

[0048] The blank model creation step (S1) is a step of creating a blank model by modeling a metal plate to be a blank using finite elements. The metal plate can be a plate made of various metals such as SUS, aluminum, and magnesium, represented by a hot rolled steel sheet, a cold rolled steel sheet, or a galvanized steel sheet subjected to surface treatment (electro-galvanizing, hot-dip galvanizing, organic finishing, etc.).

[0049] The blank model creation step (S1) includes a blank mesh creation step (S1-1), a grouping step (S1-2), and a deformation condition setting step (S1-3).

[0050] 《Blank mesh creation process》

[0051] The blank mesh creation step (S1-1) is a step of creating a finite element mesh constituting a blank model.

[0052] 《Grouping process》

[0053] The grouping step (S1-2) is a step of grouping the finite elements constituting the finite element mesh into a plurality of groups. For example, when there are 1000 finite elements, the 1000 finite elements are divided into three groups, such as A, B, and C. It is possible to arbitrarily determine which finite element belongs to which group. The finite element mesh constituting the blank is divided into a plurality of groups because the conditions related to the deformation are set differently for each group in order to reproduce the uneven deformation in the metal material, and the number of groups can be at least 2 or more.

[0054] 《Deformation condition setting process》

[0055] The deformation condition setting step (S1-3) sets deformation-related conditions differently for each of the grouped finite elements. Examples of deformation-related conditions include mechanical properties, plate thickness, element size, and element type.

[0056] Mechanical properties refer to yield strength, tensile strength, strain hardening exponent (n-value), plastic strain ratio (plastic strain ratio) (r-value), friction coefficient, stress-strain relation, etc., which are deformation-related characteristics such as the ease of deformation in stamping. Plate thickness is also a condition related to deformation. If the plate thickness is thick, it is difficult to deform, and if the plate thickness is thin, it is easy to deform. In addition, in the forming analysis using the finite element method, the calculated stress and strain are different depending on the unit size and unit type, so the unit size and unit type also become conditions related to deformation. As unit types, as shapes, triangles and quadrilaterals can be cited, and as integral methods, complete integral types and selective reduced integral types can be cited.

[0057] When the mechanical properties are set differently, it is preferable to set the range of the mechanical properties to be within the range of the deviation of the mechanical properties of the structures of the metal materials used as the blank. For example, in the case of dual-phase steel mainly composed of ferrite and martensite, the tensile strength of ferrite is set within the range of 210 to 300 MPa (MPa-grade) in each grid, and the tensile strength of martensite is set within the range of 1200 to 1800 MPa.

[0058] In addition, it is preferable to set the range of mechanical properties within the range of the deviation of the mechanical properties of the metal material used as the blank. For example, in the case of a 1180 MPa grade high-tensile steel sheet, the tensile strength is set within the range of 1180 to 1300 MPa in each mesh.

[0059] As described above, when the mechanical properties are set to different settings, by setting the properties to be within the range of the actual metal material, it is possible to obtain analysis results suitable for the metal material actually used.

[0060] In addition, when the plate thickness is set to different settings, it is preferable to set the plate thickness to be within the range of ±20% of the plate thickness of the metal material used as the blank. For example, when the metal material is a cold-rolled steel plate, the maximum allowable difference in thickness (Tables 15 and 16) shown in JIS G 3141 (cold-rolled steel plates and steel strips) is ±20%, and the plate thickness can be set to different settings within this range.

[0061] When the element size is set differently, it is preferred that the range of the element size to be set is at least 1 / 2 of the thickness of the metal plate used as the blank. The definition of the shell element requires the element size to be sufficiently larger than the plate thickness, but in actual analysis, about 1 / 2 of the plate thickness is used, so the element size can be set differently within this range.

[0062] <Stamping Forming Analysis Process>

[0063] The stamping analysis process (S2) is a process for performing stamping analysis using the created blank model. In the stamping analysis, the deformation state when the blank model is formed into the target shape by the die model is analyzed, and the analysis results of the forming process, the stress, strain, plate thickness, etc. at the forming bottom dead center are obtained. The analysis results based on the created blank model reproduce the unevenness of the deformation of the metal plate, and obtain results close to the actual stamping results. This is shown in the embodiment described later. If a crack judgment is performed based on the stamping analysis results using the blank model of the present invention, a result close to the actual stamping part is obtained. This confirms that the stamping analysis results reproduce results close to the actual stamping results.

[0064] According to the present embodiment, in the stamping analysis using the finite element method, it is possible to perform appropriate forming analysis that takes into account the unevenness of deformation within the metal material. As a result, it is possible to improve the accuracy of determining stamping cracks during stamping. Therefore, stamping cracks are determined based on the results of the stamping analysis of the present invention, and stamping is performed under stamping conditions in which crack countermeasures are implemented, thereby suppressing defects in stamped parts.

[0065] In the above description, the finite element meshes constituting the blank are grouped, and the conditions related to deformation are set differently for each group. However, if the condition related to deformation is the element size, Figure 2As shown, the blank model creation step (S11) may be constituted by the following steps. That is, it may also be a method including the following steps: a region setting step (S11-1) of setting a plurality of regions inside a contour line representing the shape of the blank; and a mesh creation step (S11-2) of creating a finite element mesh having a different condition related to deformation, that is, a different unit size, for each of the plurality of regions set.

[0066] <Another aspect of embodiment 1>

[0067] like Fig.11 As shown, the stamping analysis method involved in another mode of the present embodiment 1 includes: before the blank model creation process (S1) of the stamping analysis method involved in the present embodiment 1, a blank characteristic variation range measurement process (S0) is performed to measure the variation range of the mechanical properties or the range of the plate thickness of the metal plate used as the blank.

[0068] Moreover, in the deformation condition setting step (S1-3) of the blank model creation step S1 of the stamping analysis method of the above-mentioned embodiment 1, when the mechanical properties are set differently, in the blank characteristic variation range measurement step (S0), for the range of mechanical properties to be set, the hardness distribution of the metal plate used as the blank is measured, and the range of deviation of the mechanical properties is determined based on the measured hardness distribution.

[0069] For example, the hardness (Vickers hardness HV) distribution of the metal plate used as the blank is measured. It is known that the Vickers hardness HV is equivalent to about 1 / 3 of the tensile strength (for example, JIS Handbook (1) Steel I, Japan Standards Association, SAE-J-417 Hardness Conversion Table). Even if it is impossible to collect a tensile test piece from the metal plate used as the blank (for example, JIS Z 2201), as long as the distance between the centers of the indentations is more than 3 times the diagonal distance of the indentations (more than 20 μm) (for example, ISO 6507), the range of the deviation of the tensile strength can be obtained based on the Vickers hardness HV distribution of the metal plate.

[0070] In addition, in the deformation condition setting step (S1-3) of the blank model creation step S1 of the stamping forming analysis method of the above-mentioned embodiment 1, when the plate thickness is set to different settings, in the blank characteristic variation range measurement step (S0), for the range of the plate thickness to be set, the surface roughness of the front and back surfaces of the metal material applied as the blank can also be measured, and the range of the plate thickness can be determined based on the measured surface roughness. For example, the arithmetic average roughness Ra defined in JIS B0601 and the arithmetic average height Sa defined in ISO 25178 can be used as the range of the plate thickness of the metal material applied as the blank.

[0071] In addition, when measuring the hardness distribution of a metal plate used as a blank, determining the range of deviation of mechanical properties based on the measured hardness distribution, and setting different tensile strengths for each unit belonging to each group, the surface roughness of the front and back sides of the metal plate used as a blank can also be measured, and the range of plate thickness can be determined based on the surface roughness of the above-mentioned metal plate, and the plate thickness of the finite element mesh constituting the blank model can be randomly set within the above-mentioned plate thickness range regardless of the group.

[0072] According to the stamping analysis method involved in another mode of the present embodiment 1, the variation range of the mechanical properties (tensile strength) of the metal plate used as the blank to be formed into the stamping part or the range of the plate thickness is determined based on the hardness distribution of the metal plate used as the blank to be formed into the stamping part and the measurement results of the surface roughness of the front and back surfaces of the metal plate. As a result, the reproduction accuracy of the cracks of the stamping part caused by the uneven deformation in the metal material used as the blank to be formed into the stamping part can be further improved.

[0073] [Implementation Method 2]

[0074] By implementing the stamping analysis method of the first embodiment described above and using the results thereof, it is possible to determine whether cracks are generated in the stamping of the stamped part. Figure 3 As shown, it includes a blank model creation step (S1, S11), a stamping analysis step (S2) and a stamping crack determination step (S3). The blank model creation step (S1, S11) and the stamping analysis step (S2) are as described in Implementation Example 1. The stamping crack determination step (S3) determines whether cracks are generated in the stamping of the above-mentioned stamped parts based on the forming limit diagram (FLD) of the metal sheet used for the stamped parts.

[0075] Many commercial CAE (Computer Aided Engineering) solvers are also equipped with a function that uses the results obtained through press forming simulation to determine whether cracks have occurred based on FLD. Therefore, by using this function, it is possible to easily determine whether cracks have occurred during press forming.

[0076] <Another aspect of the second embodiment>

[0077] Another aspect of the second embodiment relates to a method for determining cracks in stamping, which implements the stamping analysis method according to another aspect of the first embodiment and uses the result to determine whether cracks are generated in the stamping of the stamped part. Fig.12 As shown, another method of stamping crack determination of the second embodiment includes a blank characteristic variation range determination step (S0), a blank model creation step (S1, S11), a stamping analysis step (S2) and a stamping crack determination step (S3). The blank characteristic variation range determination step (S0), the blank model creation step (S1, S11) and the stamping analysis step (S2) are as described in the first embodiment.

[0078] According to this embodiment, the range of variation of the mechanical properties (tensile strength) or the range of the plate thickness of the metal plate used as a blank to be formed into a stamped part is determined based on the hardness distribution of the metal plate used as a blank to be actually formed into a stamped part and the measurement results of the surface roughness of the front and back sides of the metal plate, thereby further improving the accuracy of judging cracks in the stamped part.

[0079] [Implementation method 3]

[0080] The third embodiment relates to a method for manufacturing a stamped part using the stamping crack determination method of the second embodiment. Figure 4 As shown, the manufacturing method of the stamped parts of the present embodiment 3 includes a blank model creation step (S1, S11), a stamping analysis step (S2), a stamping crack judgment step (S3), a stamping condition adjustment step (S4) and a stamping part manufacturing step (S5).

[0081] The blank model creation step (S1, S11) and the stamping analysis step (S2) are as described in Embodiment 1. In addition, the stamping crack determination step (S3) determines whether cracks are generated in the stamping of the stamped part by the stamping crack determination method of Embodiment 2. In addition, when it is determined in the crack determination step that cracks are generated, the stamping condition adjustment step (S4) changes the stamping conditions including the blank shape and the die shape in the stamping analysis until it is determined that no cracks are generated in all parts of the stamped part.

[0082] When a stamping die composed of a die, a punch, and a blank holder (blank holder) is used to draw a stamped part, the stamping conditions such as the blank holder pressure, the radius of the die shoulder part, the radius of the punch shoulder part, and the lubrication of the blank in contact with the die surface and the blank holding surface are changed. By changing the plate pressing force, the tension acting on the blank during stamping can be optimized to eliminate the generation of cracks.

[0083] In the shoulder part of a die and the shoulder part of a punch, the blank is subjected to bending deformation and unbending deformation while bearing tension, and the thickness reduction is easily promoted sharply to reach rupture. Therefore, by changing the shape of the stamping die in a way that increases the radius of the die shoulder and the radius of the punch shoulder, it is also possible to eliminate cracks at the die shoulder and the punch shoulder, promote the flow of material (metal flow) through the die shoulder and the punch shoulder, and eliminate cracks generated near the die shoulder and the punch shoulder. By lubricating the blank in contact with the die surface and the plate pressing surface, the drawability limit is increased, and the generation of cracks can be eliminated.

[0084] In addition, the stamping part manufacturing process (S5) manufactures a stamping part by stamping a metal plate under the stamping conditions of the stamping analysis when it is determined that no cracks are generated in the stamping condition adjustment process (S4). When the plate pressing force is changed as the stamping condition of the stamping analysis, the set value in the control panel of the air pressure of the air pressure die cushion (auxiliary pressure device) of the stamping machine is changed, and the metal plate is stamped to manufacture the stamping part.

[0085] In the case where the shape of the stamping die is changed as a stamping condition for stamping analysis, the shape data of the stamping die (model) used in the stamping analysis is input into a CAD / CAM program that cooperates with an NC machine tool (numerically-controlled machine) and converted into NC data (numerical control data) (NC program) for NC machining (NC machining). In addition, the NC machine tool performs machining on a casting mold model or a steel mold made of expanded polystyrene by a full mold casting method (evaporative pattern casting method). Then, using the NC data (NC program), a casting mold model or a steel mold made of expanded polystyrene is created by the NC machine tool. Then, using the stamping die with the changed shape, the metal plate is stamped to manufacture a stamped part. When the lubrication of the blank in contact with the die surface and the plate pressing surface is changed as the stamping forming conditions for stamping analysis, the type of lubricating oil is changed (viscosity coefficient is increased, extreme pressure additives are added), polymer films such as polyethylene films are inserted, and metal plates are stamped to produce stamped parts.

[0086] According to the present embodiment, a press-formed product in which press-forming cracks are suppressed can be manufactured.

[0087] <Another aspect of the third embodiment>

[0088] like Fig.13As shown, the method for manufacturing a stamped part according to another aspect of the third embodiment may include a blank property variation range measuring step (S0). The blank property variation range measuring step (S0) is as described in the first embodiment.

[0089] According to another mode of the third embodiment, the variation range of the mechanical property (tensile strength) or the range of the plate thickness of the metal plate used as the blank to be formed into the stamped part is determined based on the hardness distribution of the metal plate used as the blank to be actually formed into the stamped part, and the surface roughness measurement results of the front and back surfaces of the metal plate, so that the accuracy of the determination of the crack of the stamped part can be further improved. Thus, the stamped part in which the stamping crack is further suppressed can be manufactured.

[0090] [Implementation Method 4]

[0091] The present embodiment relates to a stamping analysis device that executes the stamping analysis method of the first embodiment. Figure 5 An example of the structure of the stamping analysis device 1 according to the present embodiment is shown. The stamping analysis device 1 is composed of a PC (personal computer) and the like. Figure 5 As shown, there is a display device 3, an input device 5, a memory storage 7, a working data memory 9 and an arithmetic processing unit 11. The display device 3, the input device 5, the memory storage 7 and the working data memory 9 are connected to the arithmetic processing unit 11, and each function is executed according to the instruction from the arithmetic processing unit 11. The functions of each component of the stamping forming analysis device 1 involved in this embodiment are described below.

[0092] Display Device

[0093] The display device 3 is used to display the blank model, the analysis target model, the analysis results, etc., and is composed of a liquid crystal monitor (LCD monitor) or the like.

[0094] Input Device

[0095] The input device 5 is used for the blank model file 13 ( Figure 5 ) reading, blank model, analysis object model display, etc., and the operator's input of instructions, etc., is composed of a keyboard, a mouse, etc.

[0096] Storage Device

[0097] The storage device 7 is used for storing various files such as the flat model file 13 and analysis results, and is composed of a hard disk or the like.

[0098] 《Data storage for operation》

[0099] The working data memory 9 is used for temporary storage and calculation of data used by the calculation processing unit 11 and is composed of a RAM (Random Access Memory) or the like.

[0100] 《Calculation Processing Department》

[0101] like Figure 5 As shown, the operation processing unit 11 includes a blank model creation unit 15 and a stamping forming analysis unit 17. In addition, the blank model creation unit 15 includes a blank mesh creation unit 19, a grouping unit 21, and a deformation condition setting unit 23. Each unit of the operation processing unit 11 functions by executing a predetermined program through the CPU (central processing unit) of the PC (personal computer). The functions of each unit of the operation processing unit 11 are described below.

[0102] <Material mesh creation section>

[0103] The blank mesh creating unit 19 has a function of creating a finite element mesh constituting a blank model.

[0104] <Grouping Department>

[0105] The grouping unit 21 has a function of grouping the finite elements constituting the finite element mesh into a plurality of groups.

[0106] <Deformation condition setting section>

[0107] The deformation condition setting unit 23 has a function of setting mechanical properties, element sizes, or element types, which are conditions related to deformation, differently for each group of finite elements.

[0108] According to the stamping analysis device 1 involved in this embodiment, as described in Embodiment 1, in the stamping analysis using the finite element method, it is possible to perform appropriate forming analysis that takes into account the unevenness of deformation in the metal material. This can improve the accuracy of determining stamping cracks during stamping.

[0109] In the case where the condition relevant to the deformation is the element size, it can also be Figure 6As shown in the stamping analysis device 25, the blank model creation unit 27 is composed of a region setting unit 29 and a mesh creation unit 31. The region setting unit 29 has a function of setting a plurality of regions inside the contour line representing the shape of the blank. In addition, the mesh creation unit 31 has a function of creating a finite element mesh with different conditions related to deformation, that is, unit sizes, for each of the set plurality of regions.

[0110] [Implementation method 5]

[0111] The stamping analysis program involved in this embodiment enables the computer to function as the stamping analysis device 1, 25 shown in Embodiment 4. Specifically, the stamping analysis program is executed by the CPU, thereby enabling the blank model creation unit 15 (blank mesh creation unit 19, grouping unit 21, deformation condition setting unit 23) and the stamping analysis unit 17 to function. In addition, as another mode, the stamping analysis program is executed by the CPU, thereby functioning as the blank model creation unit 27 (region setting unit 29, mesh creation unit 31).

[0112] Example 1

[0113] Since a simulation was performed to confirm the effect of the present invention, the following description will be given. Figure 7 33 is a component of the present embodiment. Figure 7 As shown in FIG. 1 , the component 33 includes a top plate portion 35, side wall portions 37 on both sides of the top plate portion 35, and a flange portion 39 located at the lower end of the side wall portion 37. The top plate portion 35 is bent into an upward convex shape. In addition, both ends are bent downward, and end flange portions 41 are provided at the lower end. The width of the end flange portion 41 is 100 mm, the width between the two side wall portions in the center of the component is 60 mm, and the R (radius) of the ridge line section connecting the top plate portion 35 and the side wall portion 37 in the center of the component is 10 mm (R10). In addition, the material of the component 33 is a cold-rolled 1180 MPa grade high-tensile steel plate with a plate thickness of 1.40 mm.

[0114] The blank mesh used in the existing stamping analysis is as follows Figure 8 As shown in (a), the blank mesh involved in the present invention is as follows Figure 8 (b) Figure 8 (c) Figure 8 As shown in (d), the specifications shown in each figure are shown in Table 1.

[0115] [Table 1]

[0116]

[0117] Figure 8 All the elements of the blank mesh shown in (a) are the same, the element size is 1.20 mm, the element type is a quadrilateral fully integrated shell element, the plate thickness is 1.40 mm, the yield strength is 886 MPa, and the tensile strength is 1234 MPa.

[0118] Figure 8 The blank mesh shown in (b) divides the elements constituting the blank mesh into three groups, and sets different plate thicknesses or tensile strengths for each element belonging to each group, while the other setting conditions are the same. Specifically, situation 1 is a case where the element size is 1.20 mm, the element type is a quadrilateral fully integrated shell element, the plate thickness is 1.35 mm, 1.40 mm, and 1.45 mm for each group, the yield strength is 886 MPa, and the tensile strength is 1234 MPa. In addition, situation 2 is a case where the element size is 1.20 mm, the element type is a quadrilateral fully integrated shell element, the plate thickness is 1.40 mm, the yield stress is 886 MPa, and the tensile strength is 1234 MPa as a benchmark, 1221 MPa relative to the benchmark -1%, and 1246 MPa relative to the benchmark +1% for each group.

[0119] Figure 8 The blank mesh shown in (c) makes the size of one side of the quadrilateral unit arbitrarily change between 0.70mm and 1.80mm, the unit type is a quadrilateral fully integrated shell unit, the plate thickness is 1.40mm, the yield strength is 886MPa, and the tensile strength is 1234MPa. In the embodiment, after creating units with uniform sizes of 1.20mm in length and width, the coordinates of the nodes of the units constituting the range (group) of unit size changes are arbitrarily moved in the range of +0.30mm and -0.25mm in the length and width of the plane, respectively, to change the unit size.

[0120] exist Figure 8 In the blank mesh shown in (d), the units constituting the blank mesh are divided into two groups, and the unit type is different for each unit belonging to each group, and other setting conditions are the same. Specifically, the unit size is 1.20 mm, the unit type is quadrilateral fully integrated shell unit and triangular fully integrated shell unit, the plate thickness is 1.40 mm, the yield strength is 886 MPa, and the tensile strength is 1234 MPa.

[0121] Fig. 9 Indicates the actual Figure 7 The actual stamped part 43 is manufactured by stamping a stamped part having the same shape as the stamped part shown in FIG. Fig. 9As shown, in the actual press-formed product 43 , cracks are generated in the width direction of the top plate portion 45 near the center of the top plate portion 45 in the longitudinal direction of the component 33 .

[0122] in addition, Fig.10 (a) indicates the use of Figure 8 The previous forming analysis results of the blank composed of the blank grid of (a). Fig.10 (b-1) is represented by Figure 8 (b) is the analysis result of the blank case 1 composed of the blank mesh, Fig.10 (b-2) is represented by Figure 8 (b) is the analysis result of case 2 of the blank composed of the blank mesh. In addition, Fig.10 (c) indicates that Figure 8 (c) The analysis results of the blank composed of the blank grid, Fig.10 (d) indicates that Figure 8 (d) Analysis results of the blank composed of the blank mesh. Fig.10 The analysis results are the results of stamping analysis based on the crack judgment using FLD, and the analysis results of the crack occurrence site are shown in black in the figure.

[0123] As a result of the existing example Fig.10 In (a), no black line indicating crack generation appears, but in the result of the invention example Fig.10 In (b) to (d), a black line appears near the center of the top plate in any case. As described above, the crack generation cannot be determined in the conventional example, but the crack generation can be determined in the example of the present invention, and a close approximation can be obtained. Fig. 9 The result of the actual stamped part 43 is shown.

[0124] Example 2

[0125] will with Figure 7 The same shape of the component 33 as in the first embodiment shown in the figure is used as the object, and a metal plate with a thickness of 1.4 mm, a yield strength of 1055 MPa, and a tensile strength of 1470 MPa is used as the blank. Fig.14 The stamping die shown ( Fig.14 (a) is the lower mold 47, Fig.14 (b) is the upper die 49), and the stamped part (component 33) involved in this embodiment 3 is manufactured. The lower die is composed of a punch 47a and a plate pressing member 47b (blank holder), and the upper die 49 is composed of a die 49a.

[0126] The element size of the blank mesh used in the stamping analysis is 1.20 mm, and the element type is a quadrilateral fully integrated shell element, such as Figure 8As shown in (b), the cells constituting the blank mesh are divided into three groups, and different tensile strengths are set for each cell belonging to each group.

[0127] The Vickers hardness HV distribution of the metal plate used as the blank was measured, and the range of tensile strength set for each unit belonging to each group was set based on the range of deviation of the mechanical properties determined by the measured hardness distribution. The Vickers hardness HV was measured at 1mm intervals over the entire length of the metal plate in the plate width direction, and the indenter used the indenter specified in JIS B 7725, the test force was 200g, and the test force was maintained for 10 seconds. Based on the deviation of the Vickers hardness HV relative to the average value (1σ=3.8%), the tensile strength was set to three types for each group: 1234MPa relative to the benchmark -7.6% (-2σ) 1141MPa, and 1327MPa relative to the benchmark +7.6% (=2σ).

[0128] In addition, the surface roughness of the front and back surfaces of the metal material used as the blank was measured, and the range of the blank thickness was determined based on the arithmetic mean height Sa defined in ISO 25178. Based on the measured average value (Ave) of Sa of 0.022 mm and the standard deviation (σ) of 0.0018 mm, the range of the thickness (total of the front and back surfaces) was set to 1.40 mm ± 0.0025 (= Ave + 2σ) mm, and the thickness of the finite element mesh constituting the blank was randomly set regardless of each group.

[0129] Furthermore, the press forming analysis was performed with the plate pressing force (force generated at the contact portion between the plate pressing member and the die) being 40 tons as the press forming condition. Fig.15 (a) shows the analysis results. Fig.15 The analysis result of (a) is based on the result of stamping analysis, and the crack judgment is performed using FLD, and the analysis result of the crack occurrence site is shown by the black line in the figure. Fig.16 (a) indicates the use of Fig.14 The stamping die is used to stamp the metal plate under the above-mentioned stamping conditions to produce the actual stamped parts. Fig.16 As shown in (a) of FIG. 1 , in the actual press-formed product, cracks are generated in the width direction of the top plate portion near the center of the top plate portion in the component length direction.

[0130] Next, press forming analysis was performed with the plate pressing force being 30 tons as press forming conditions. Fig.15 (b) shows the analysis results. Fig.15 In the analysis result of (b), it was determined that the crack generation site of the top plate portion was eliminated and no cracks were generated in any site of the stamped part.

[0131] Next, as the stamping forming conditions for the stamping forming analysis in which no cracks were determined, the air pressure of the air pressure type die pad (auxiliary pressure device) of the stamping forming machine was changed to the setting value in the control panel so that the plate pressing force became 30 tons, and the Fig.14 The stamping die actually stamps the metal plate to produce the stamped parts. Fig.16 (b) represents the actual stamping part. Fig.16 As shown in (b), in the actual stamping part, Fig.15 Similarly to the analysis result of (b), cracks in the width direction of the top plate near the center of the top plate portion in the member length direction can be suppressed.

[0132] As described above, it has been confirmed that by performing stamping analysis using a blank model to which the present invention is applied, the analysis result can be made close to the actual stamped part 43. That is, the present invention can improve the accuracy of determining stamping cracks during stamping. Therefore, stamping cracks are determined based on the results of the forming analysis of the present invention, and stamping is performed under stamping conditions in which crack countermeasures are implemented, thereby suppressing defects in stamped parts.

[0133] Industrial Applicability

[0134] According to the present invention, it is possible to provide a stamping analysis method that can take into account the non-uniformity of deformation within the metal material by the finite element method in stamping using a metal plate and can predict cracks in a stamped part with high accuracy. In addition, according to the present invention, it is possible to provide a stamping crack determination method that can determine cracks in a stamped part with high accuracy, and a method for manufacturing a stamped part using the stamping crack determination method. Furthermore, according to the present invention, it is possible to provide a stamping analysis device and a stamping analysis program that can perform stamping analysis with high accuracy by the finite element method.

[0135] Description of Reference Numerals

[0136] 1…stamping analysis device; 3…display device; 5…input device; 7…storage device; 9…operation data storage device; 11…calculation processing unit; 13…blank model file; 15…blank model creation unit; 17…stamping analysis unit; 19…blank mesh creation unit; 21…grouping unit; 23…deformation condition setting unit; 25…stamping analysis device (another method); 27…blank model creation unit (another method); 29…area setting unit; 31…mesh creation unit; 33…component; 35…top plate portion; 37…longitudinal wall portion; 39…flange portion; 41…end flange portion; 43…actual stamping part; 45…top plate portion; 47…lower die; 47a…punch; 47b…plate pressing member; 49…upper die; 49a…die.

Claims

1. A stamping forming analysis method, based on a finite element method for executing each process on a computer, characterized in that: The method comprises: a blank model creation step, in which a blank model is created; and a stamping forming analysis step, in which the created blank model is used to perform stamping forming analysis. The blank model creation process comprises: A billet mesh creation process, which creates a finite element mesh constituting a billet model; a grouping step of grouping the finite elements constituting the finite element mesh into a plurality of groups; and The deformation condition setting step sets conditions related to deformation differently for each of the grouped finite elements.

2. The stamping forming analysis method according to claim 1, characterized in that: The deformation condition setting step sets mechanical properties or plate thicknesses differently for each group.

3. The stamping forming analysis method according to claim 1, characterized in that: The deformation condition setting step sets the unit size differently for each group.

4. The stamping analysis method according to claim 1, characterized in that: The deformation condition setting step sets the unit type differently for each group.

5. The stamping analysis method according to claim 2, characterized in that: When the mechanical properties are set differently, the range of the mechanical properties to be set is set within the range of the variation of the mechanical properties of the structures of the metal materials used as the blank.

6. The stamping analysis method according to claim 2, characterized in that: When the mechanical properties are set differently, the range of the mechanical properties to be set is set within the range of variation of the mechanical properties of the metal material used as the blank.

7. The stamping analysis method according to claim 6, characterized in that: include: The process of measuring the variation range of the mechanical properties of the metal plate used as the blank is used to measure the variation range of the mechanical properties of the metal plate used as the blank. In this process of measuring the variation range of the blank properties, the hardness distribution of the metal plate used as the blank is measured, and the range of deviation of the mechanical properties is determined based on the hardness distribution.

8. The stamping analysis method according to claim 7, characterized in that: In the process of measuring the range of variation of the blank characteristics, the surface roughness of the front and back sides of the metal plate used as the blank is also measured, and the range of the plate thickness is determined based on the surface roughness of the metal plate. The plate thickness of the finite element mesh constituting the blank model is randomly set within the range of the plate thickness.

9. The stamping analysis method according to claim 2, characterized in that: When the plate thickness is set differently, when the plate thickness is set, the range of the plate thickness is set to be within the range of ±20% of the plate thickness of the metal material used as the blank.

10. The stamping analysis method according to claim 9, characterized in that: include: A blank property variation range measuring step is used to measure the range of the plate thickness of the metal plate used as the blank. In this blank property variation range measuring step, the surface roughness of the front and back sides of the metal plate used as the blank is measured, and the range of the plate thickness is determined based on the surface roughness of the metal plate.

11. A stamping forming analysis method, based on a finite element method for executing each process on a computer, characterized in that: The method comprises: a blank model creation step, in which a blank model is created; and a stamping forming analysis step, in which the created blank model is used to perform stamping forming analysis. The blank model creation process comprises: an area setting step of setting a plurality of areas inside a contour line representing the shape of the blank; and The mesh creation step creates a finite element mesh having a different cell size, which is a condition related to deformation, for each of the plurality of set regions.

12. The stamping analysis method according to claim 3 or 11, characterized in that: The range of the cell size to be set is set to be at least 1 / 2 of the thickness of the metal plate used as the blank.

13. A method for determining a stamping crack of a stamped part, characterized in that: A stamping analysis of a stamped part is performed using the stamping analysis method described in any one of claims 1 to 12, and includes: a stamping crack determination step for determining whether cracks are generated during the stamping of the stamped part based on a forming limit diagram (FLD) of a metal plate used for the stamped part.

14. A method for manufacturing a stamped part, which suppresses stamping cracks, characterized in that: It includes the stamping crack determination process, stamping condition adjustment process and stamping part manufacturing process. The stamping crack determination step determines whether cracks are generated in the stamping of the stamped part by using the stamping crack determination method of the stamped part according to claim 13. When it is determined in the stamping crack determination step that cracks are generated, the stamping condition adjustment step changes the stamping conditions including the blank shape and the die shape in the stamping analysis until it is determined that no cracks are generated in all parts of the stamped part. The stamped part manufacturing step manufactures a stamped part by stamping a metal sheet under the stamping conditions of the stamping analysis when it is determined in the stamping condition adjustment step that no cracks are generated.

15. A stamping analysis device for performing stamping analysis of stamping parts, characterized in that: have: a blank model creating unit that creates a blank model; and The stamping analysis department uses the created blank model to perform stamping analysis. The blank model creation unit comprises: A blank mesh creation section creates a finite element mesh constituting a blank model; a grouping unit, which groups the finite elements constituting the finite element mesh into a plurality of groups; as well as The deformation condition setting unit sets mechanical properties, element sizes, or element types, which are conditions related to deformation, differently for each of the grouped finite elements.

16. A stamping analysis device for performing stamping analysis of stamping parts, characterized in that: have: a blank model creating unit that creates a blank model; and The stamping analysis department uses the created blank model to perform stamping analysis. The blank model creation unit comprises: an area setting unit that sets a plurality of areas inside a contour line representing a shape of the blank; and The mesh creation unit creates a finite element mesh having a different cell size, which is a condition related to deformation, for each of the plurality of set regions.

17. A stamping forming analysis program, characterized in that: A computer is made to function as the press forming analysis device according to claim 15 or 16.

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