JP4724626B2 - Springback occurrence cause identifying method, apparatus thereof, and program thereof - Google Patents

Description

  The present invention relates to a method, an apparatus, and a program for identifying a cause portion of a springback generated in a press-formed product when a member for an automobile is press-formed from a steel material such as a steel plate or a steel bar.

Many automotive parts such as doors and bumpers, household electrical appliances, and building materials are manufactured by press forming of steel plates. In recent years, demands for weight reduction of these members have increased, and measures such as thinning the steel material by using a steel material having high strength in order to realize the demand have been attempted.
However, with the strengthening of steel sheets, strict management is required to secure the product shape by press forming, and one of the important items in the management is driving residual stress generated in the steel sheet during press forming. As a force, a spring back is a deformation in which the elastic deformation of the steel plate is elastically recovered.

  In recent years, in order to reduce the development man-hours and costs of automobiles, etc., there is a tendency to start a design stage at the same time as the design stage to examine the molding method of the molded member. Therefore, the man-hours and costs at the design stage for examining the molding method of the molded member have become a bigger problem in the development process and development cost of automobiles and the like.

  FIG. 1 is a schematic cross-sectional view of a molded member showing correspondence to a conventional spring back. (A) shows the shape cross section of the molded product, (b) shows the spring back generated in the molded product after cold press-molding the steel plate with the same mold as the molded product shown in (a), ( c) shows the cross section of the mold shape corrected for spring back. As described above, in order to obtain the molded product shown in (a), there is a correspondence to obtain a desired molded product by using a “prospect” mold that anticipates spring back as shown in (c).

  As a method of forming a mold that anticipates such springback, the residual stress of the steel plate at the bottom dead center pressed to the mold is analyzed by the finite element method, and deformation caused by the residual stress in the opposite direction to the residual stress There has been proposed a method of simply forming a mold in consideration of springback by numerically analyzing a (spring forward) mold (Patent Document 1, Non-Patent Document 1).

  However, since it is very difficult to design a die that fully considers springback by numerical analysis, it is very difficult, so the proposed method simply considers springback by the finite element method. It is to mold a mold. For this reason, it is difficult to numerically analyze what measures are required when the mold does not satisfy the allowable amount of springback. Not.

  For this reason, a mold that easily considers springback, and if the allowable amount of springback is not satisfied, what measures are taken to obtain the desired molded product depends on the experience of engineers. become. Eventually, a trial-and-error test using a mold by the forming method and an actual steel plate is required.

In addition, a method has been proposed in which the springback is reduced by modifying the shape of the steel material or molded product, not the mold shape, to remove residual stress.
FIG. 2 is a perspective view illustrating a conventional method for searching for a site that causes deformation due to springback. (A) shows the shape of the molded product, (b) shows the case where part 1 of the product is cut and removed, (c) shows the case where a hole 2 is made in the product, (d) shows The case where the slit 3 is given to a part of the product is shown. By taking such measures, an attempt has been made to observe the behavior of the springback and to reduce the springback.

  However, even if the springback is suppressed by measures against the springback occurrence site, the rigidity of the member itself is reduced for cutting and removing or drilling. The cause cannot be investigated. Furthermore, since such a measure actually requires a test using a test mold and a steel plate, there arises a problem of an increase in man-hours and costs at the design stage.

JP 2003-33828 A Mitsubishi Motors Technical Review (2006 No.18, pages 126-131)

  In view of the problems as described above, the present invention specifies a part that causes the occurrence of springback in a press-molded product, and numerically analyzes the property of the specific part, thereby reducing the examination time of the molding method of the molded member. It is an object to provide a method for efficiently and economically shortening.

  Moreover, this invention makes it a subject to provide the molded product which makes a springback amount below an allowable value by numerical analysis, maintaining product strength.

In order to solve the above problems, the present invention provides:
(I) a press molding analysis step in which a computer numerically analyzes molding conditions for press molding to obtain molding data of a press molded product;
(Ii) The stress in the three-dimensional coordinate system x, y, z direction, the xy plane, and the yz plane for a partial region of the press-molded product among the molding data of the press-molded product obtained in step (i) by the computer , An arithmetic processing step for performing arithmetic processing to change any one of the factors of shear stress in the zx plane;
(Iii) a springback amount calculating step in which the computer calculates a springback amount based on the result of the arithmetic processing performed in step (ii);
(Iv) a computer obtains a springback amount difference between the springback amount calculated in step (iii) and the springback amount calculated without performing the arithmetic processing in step (ii);
(V) The computer performs the steps (ii) to (iv) for at least one other region different from the partial region to obtain a springback amount difference, and performs the calculation processing of the partial region. Comparing the resulting springback amount difference with the springback amount difference resulting from the calculation processing of the other region to identify a region that gives the maximum springback amount difference;
(Vi) The computer divides the region giving the maximum springback amount difference, and the steps (i) to (b) are performed for each of the divided regions until the size of the divided region becomes a predetermined value or less. v), and
Provided is a method for identifying the cause of occurrence of springback , characterized by identifying a portion that causes springback and stress or shear stress .

The present invention also provides:
  A press molding analysis unit that numerically analyzes the molding conditions of press molding and obtains molding data of the press molded product,
  A numerical analysis of the molding data, and a springback analysis unit for calculating a springback amount;
  Among the molding data of the press-molded product, any one of the factors of the stress in the three-dimensional coordinate system x, y, z direction of the partial region of the press-molded product, the shear stress of the xy plane, the yz plane, and the zx plane Performing an arithmetic process for changing one, causing the springback analysis unit to calculate a springback amount based on the result of the arithmetic process, and performing the arithmetic process on at least one other region different from the partial region And causing the springback analysis unit to calculate a springback amount based on the result of the calculation process, and further causing the springback analysis unit to calculate a springback amount based on molding data that is not subjected to the calculation process, The amount of springback calculated based on the result of the arithmetic processing in the partial area and the arithmetic processing in the other area, An arithmetic processing unit that obtains each springback amount difference from the calculated springback amount without performing the arithmetic processing, and identifies a region that gives the maximum springback amount difference,
  Have
  The arithmetic processing unit divides the region that gives the maximum springback amount difference, and changes the stress or shear stress for each of the divided regions until the size of the divided region becomes a predetermined value or less. Provided is an apparatus for identifying a cause of occurrence of springback, characterized by performing arithmetic processing to identify a portion that causes springback and a stress or shear stress.

Furthermore, the present invention provides
(I) a press molding analysis procedure for numerically analyzing press molding molding conditions to obtain molding data of a press molded product;
(Ii) Three-dimensional coordinate system x, y, z direction stress, xy plane, yz plane, zx plane for a partial region of the press molded product among the molding data of the press molded product obtained in step (i) An arithmetic processing procedure for performing arithmetic processing to change any one of the shear stress factors of
(Iii) a springback amount calculation procedure for calculating a springback amount based on the result of the arithmetic processing;
(Iv) an arithmetic processing procedure for obtaining a springback amount difference between the springback amount calculated in step (iii) and the springback amount calculated without performing the arithmetic processing in step (ii);
(V) Performing the steps (ii) to (iv) for at least one other region different from the partial region to obtain a springback amount difference, and a spring resulting from the arithmetic processing of the partial region A procedure for comparing a back amount difference and a spring back amount difference resulting from the calculation processing of the other region to identify a region that gives the maximum spring back amount difference;
(Vi) dividing the region giving the maximum springback amount difference, and performing the steps (i) to (v) for each of the divided regions until the size of the divided region becomes a predetermined value or less. Steps to do,
  To the computer,
  There is provided a springback occurrence cause identifying program characterized by identifying a portion causing a springback, stress or shear stress.

  According to the present invention, the specific part to be analyzed is changed as a cause of the occurrence of springback in the press-molded product, and the springback amount is minimized while numerically calculating the physical property value / physical quantity of the specific part. It is possible to identify the cause part of the occurrence of springback and to accurately derive the physical property value / physical quantity of the cause part, or to check them by analytical trial and error. The present invention provides a method for economically and efficiently shortening a study time of a molding method of a molded member.

  Furthermore, the present invention changes the specific part and the physical property value / physical quantity of the specific part so that the amount of change in the springback is less than the allowable value without cutting or punching the actual molded product. It is possible to obtain a specific part and its property data. Therefore, it can be confirmed that the molded product analyzed in this way maintains the rigidity of the product while keeping the amount of change in springback below the allowable value, and at the same time sacrifices rigidity to maintain the amount of change in springback. Therefore, it is possible to eliminate the need for measures such as cutting and removing the molded product and making holes.

FIG. 3 is a functional configuration diagram of the springback occurrence cause identifying apparatus according to the embodiment of the present invention.
The springback generation cause identifying apparatus 10A includes a press molding analysis unit 11, a springback analysis unit 12, a physical property value / physical quantity calculation processing unit 14, a file storage unit 16, a molding condition input unit 18, and a springback amount output screen 19. Have.

  The forming condition input unit 18 includes shape data (plate thickness, length, width, curvature, strain, etc.) and properties (strength, elongation, etc.) of a steel plate to be analyzed by the press forming analysis unit 11 and the springback analysis unit 12 described later. Material, shape such as plate thickness), die shape (die (die) and punch shape, curvature, diameter, clearance, lubrication conditions), press conditions (wrinkle holding load, pad load, bead tension, temperature), etc. An input unit for inputting molding conditions.

  The press molding analysis unit 11 uses an elastic-plastic finite element method, a rigid-plastic finite element method, a one-step finite element method, a boundary element method, an elementary analysis, etc., with the molding conditions input by the molding condition input unit 18 as input information. Then, numerical analysis is performed to obtain stress, strain, plate thickness and the like of a press-formed workpiece such as a steel plate. The press forming analysis unit 11 outputs a numerical analysis result in the form of variables such as a plate thickness of the workpiece, a stress component value, a strain component value, and a distribution of the variables. The output data is output, for example, as a file “P org.k” to the springback analysis unit 12, the partial physical property value / physical quantity calculation processing unit 14 and the file storage unit 16 described later.

  Numerical analysis by the press forming analysis unit 11 is performed by a finite element method (for example, commercially available software PAM-STAMP, LS-DYNA, Autoform, OPTRIS, ITAS-3D, ASU / P-FORM, ABAQUS, ANSYS, MARC, HYSTAMP, Hyperform. , SIMEX, Fastform3D, Quikstamp) Shape data (plate thickness, length, width, curvature, distortion, etc.) of the product to be press-formed, and properties of the metal plate used (strength, elongation, etc., material thickness) If necessary, set molding conditions such as die shape (die and punch shape, curvature, diameter, clearance, lubrication conditions), press pressure (temperature, pressure temperature), etc., if necessary. It is possible to numerically obtain the stress and strain value distribution after the molding.

  The springback analysis unit 12 uses an output data file “P org.k” of the press forming analysis unit 11 and an output data file “P rem.casen.k” of a physical property value / physical quantity calculation processing unit 14 described later as input data. To perform springback analysis. The springback analysis is an elastic finite element method, elastoplasticity, based on the output results of the press forming analysis unit 11 such as the plate thickness of the workpiece, the stress component value, the strain component value, and the like, and the variable distribution. Calculate the unloading process using the finite element method, rigid plastic finite element method, one-step finite element method, boundary element method, primary analysis, etc., and numerically analyze the amount of springback that is the amount of deformation in the workpiece. It is. The springback amount is calculated for each element of the three-dimensional data coordinates by dividing the workpiece by the finite element method or the like. The amount of springback, which is the amount of deformation that occurs in the workpiece, includes the amount of deformation at an arbitrary point of the workpiece, the amount of deformation at the maximum or minimum displacement point within the specified area of the workpiece, There is an angle formed by a plurality of arbitrary surfaces or lines, or an arbitrary surface of the workpiece or a curvature formed by the tip.

  The springback analysis unit 12 uses a finite element method (for example, commercially available software PAM-STAMP, LS-DYNA, Autoform, OPTRIS, ITAS-3D, ASU / P-FORM, ABAQUS, ANSYS, MARC, HYSTAMP). The stress distribution described in “P org.k” obtained by the forming analysis unit 11 is input, and the springback analysis is performed. The calculation of the springback in the software is, for example, the basic equation of finite elasto-plastic deformation or the discretization method described in “Nonlinear Finite Element Method” (Corona, December 20, 1994), pages 71-127. It is calculated with the contents along. However, the springback calculation may be an elastic analysis or an elasto-plastic analysis.

  The output data of the springback analysis unit 12 includes a springback amount, a shape such as strain at the time of springback, properties, stress, etc., and is output to the springback amount output screen 19 and the input data file “P org.k”. As a numerical analysis result output data file “SB org.k” or “SB rem.casen.k” as a numerical analysis result output data file “SB rem.casen.k”, which will be described later. It is output to the physical property value / physical quantity calculation processing unit 14 and the file storage unit 16.

  The file storage unit 16 includes data files “P org.k”, “SB org.k”, “SB”, which are output results of the press forming analysis unit 11, the springback analysis unit 12, and a physical property value / physical quantity calculation processing unit 14 described later. A storage unit for storing “P rem.casen.k”, “SB rem.casen.k”, “P trim.casen.k”, and the like. However, when these data files are directly input / output between the press forming analysis unit 11, the springback analysis unit 12, and the physical property value / physical quantity calculation unit 14, the file storage unit 16 is not necessarily provided. Not necessary.

The physical property value / physical quantity calculation processing unit 14 selects a partial region in the output data file “P org.k” of the press forming analysis unit 11, and the plate thickness, elastic modulus, plasticity coefficient, An arithmetic process is performed on at least one of the stress component value and the strain component value. Then, an output data file “P rem.case1.k” after the arithmetic processing is generated and output to the springback analysis unit 12. This data file transmission / reception can be repeated, can be stored in the file storage unit 16 sequentially, and can be exchanged in the form of data input / output of the execution process or thread instead of the file format. good.

  The spring back specific part used for this calculation or the area data for determining the cause is a calculation unit such as one or more elements in the finite element method, a minute area composed of a plurality of elements, or an assembly of continuous elements. Integral points that are part of the points where stress and strain are calculated in the unit of calculation of the numerical integration method by the finite element method (including both points in the plate thickness direction and points in the plane) ) Etc. “One or more elements” refers to an element that is a region division unit of the finite element method, and “calculation unit classification” refers to one or a continuous set of minute regions that are calculation units in primary analysis. The “integration point” is a point at which approximate integration is generally performed by the finite element method. “Partial integration point” refers to a part of the points where stress and strain are calculated in the calculation unit of the numerical integration method based on the finite element method. Both points are included.

The arithmetic processing here is to factor multiplication at least one or more of the variables, it is a constant value including zero, to the four arithmetic operations, be calculated based on a function, any not constant This means replacing with a value.

  In addition, “at least one variable of plate thickness, elastic modulus, plastic coefficient, stress component value, and strain component value” means the plate thickness, elastic constant (Young's modulus, Poisson's ratio) of a part of the workpiece. ), Plastic coefficient (yield stress, plastic coefficient, work hardening index), stress or strain in x, y, z direction (each of three components), when a three-dimensional coordinate system (x, y, z) is analyzed. It means at least one of a total of 18 factors including the xy plane, the yz plane, and the shear stress or shear strain (each of three components) in the zx plane.

FIG. 4 is a diagram showing a coordinate system used in the finite element method. (A) shows the coordinate system of the whole three-dimensional, (b) shows a local coordinate system.
At this time, as shown in FIG. 4A, in addition to the component values on the (x, y, z) coordinate axes, for example, as shown in FIG. 4B, the plane of the element 31 is regarded as the xy plane. It is assumed to include a total of 12 components of stress, strain, shear stress, and shear strain in the local coordinate system (x1, x2, x3). Also, variables obtained by using each stress component and strain component such as equivalent stress, equivalent plastic strain, elastic energy (elastic work), plastic energy (plastic work), and increment of each component value such as stress increment and strain increment (See "Practical Finite Element Method-Large Deformation Elastic-Plastic Analysis-" (Corona, October 20, 1995) Nos. 7, 62, 63, 65, 66, 72) ).

  In general, in a finite element method analysis using a steel plate as an analysis target, the physical property value / physical quantity of the steel plate is divided into 2 mm to 4 mm square finite elements. However, the division unit of the element is not necessarily limited to 2 mm to 4 mm square because it is divided by a length that approximates that the physical property value / physical quantity is constant. In other words, it may be necessary to limit the finite element to be smaller in a region where the residual stress is large. Each element is defined by a three-dimensional coordinate plane, and the angle and curvature of the plane of the finite element are defined by comparison with other planes. When there is almost no change in the angle or curvature, it is estimated that there is no residual stress, and therefore it can be excluded from the determination target of the springback occurrence cause part.

  In this way, in order to identify the springback occurrence part, the plane part that is a molded product part without an angle or curvature is excluded from the judgment object, and the part with a high angle or curvature is made the judgment object, thereby reducing the amount of calculation. By greatly reducing, it is possible to identify a springback occurrence site more quickly.

As an example of arithmetic processing, a method of multiplying the σ _x component value by a coefficient will be described.
The stress component before calculation at the integration point of the selected region is (σ _x0 , σ _y0 , σ _z0 , τ _xy0 , τ _yz0 , τ _zx0 ), and the strain component is (ε _x0 , ε _y0 , ε _z0 , γ _xy0 , γ _yz0 , γ _zx0 ), the stress components (σ _x , σ _y , σ _z , τ _xy , τ _yz , τ _zx ), strain components (ε _x , ε _y , ε _z , γ _xy , γ _yz , γ _zx ) is as follows.
_{σ x = K × σ x0,} σ y = σ y0, σ z = σ z0, τ xy = τ xy0, τ yz = τ yz0, τ zx = τ zx0
ε _x = ε _x0 , ε _y = ε _y0 , ε _z = ε _z0 , γ _xy = γ _xy0 , γ _yz = γ _yz0 , γ _zx = γ _zx0
Here, K is calculated in a range of −1000 to 1000, the value before the processing is used as it is for the plate thickness, and the elastic coefficient and the plastic coefficient are values input by the molding condition input unit 18. It is common to use it. For illustration, K is shown only for σ _x , but other components may be varied as well.

In addition, material characteristics (plate thickness, elastic modulus, plasticity coefficient) can be calculated. For example, the physical property value / physical quantity calculation processing unit 14 selects a partial region of the workpiece obtained from the press forming analysis unit 11 and multiplies the selected region, for example, Young's modulus by a coefficient in the calculation processing. In that case, the thickness t ₀ before calculation of the selected region, Young's modulus E ₀ , Poisson's ratio ν ₀ , plastic coefficients F ₀ , a ₀ , n ₀ (when σ = F ₀ (ε + a ₀ ) ⁿ⁰ ) Then, the thickness t, Young's modulus E, Poisson's ratio ν, plastic coefficient F, a, n (when σ = F (ε + a) ⁿ ) after calculation are as follows.
t = t ₀ , E = K × E ₀ , ν = ν ₀ , F = F ₀ , a = a ₀ , n = n ₀
Here, K can be changed in the range of −1000 to 1000. For illustration, K is shown only for E, but other material properties may be varied as well.

Further, the physical property value / physical quantity calculation processing unit 14 can also select and perform calculation processing by selecting a region by directly editing the file that outputs the state variable obtained from the press forming analysis unit 11. For example, the contents of the file are displayed by software having a text editing function such as word pad, and the component value of the area to be processed is directly rewritten by operating the molding condition input unit 18, or the component value is replaced by cut and paste. Also good.
Thereby, it is possible to quantitatively evaluate how much the variable (component) calculated in the selected region affects the springback.

  For example, when the displacement distribution of a finite element node is displayed in a contour diagram (contour map) or a deformed cut surface is displayed in the springback analysis unit 12, the result of each calculated variable (component) in the selected region is displayed. It is possible to compare the figures side by side on the springback amount output screen 19 or output them to a printer (not shown) for comparison. If you want to check the coordinate values (X, Y, Z) of the nodes at any specified position on the software or by file output, you can compare the numerical values for each variable (component) calculated in the selected area, It is possible to make a graph and compare using calculation software or the like.

  The contour diagram displayed on the springback amount output screen 19 shows the springback while repeating the physical property value / physical quantity calculation processing by the physical property value / physical quantity calculation processing unit 14 and the springback amount calculation by the springback analysis unit 12. It is possible to strictly identify the parts and variables that cause the problem.

  Further, the specific region of the physical property value / physical quantity calculation processing unit 14 is changed by selection, or the component value of the selected region is multiplied not only by σx but also by component coefficients such as σy and τxy as calculation processing, The springback analysis unit 12 performs the springback analysis, displays the portion and variables that cause the springback on the springback amount output screen 18, and compares the amount of change in the displacement due to the springback, thereby causing the cause of the springback. It is possible to specify exactly the parts and variables that become.

  In addition, the physical property value / physical quantity calculation processing unit 14 selects a plurality of areas in a part of the workpiece, and performs the calculation process on each selected area at the same time, which is necessary for specifying the cause. It is possible to reduce the number of analysis steps.

FIG. 5 is a perspective view showing an example of region selection of a hat-shaped cross-sectional component according to an embodiment of the present invention.
For example, when the work piece obtained by the press molding analysis unit 11 is a hat-shaped cross-sectional part as shown in FIG. 5, the physical property value / physical quantity calculation processing unit 14 has a plurality of regions A1, as shown in FIG. A2 is selected at the same time, and arithmetic processing for multiplying σx by a factor is performed on the selected regions A1 and A2, and the springback analysis unit 12 performs a springback analysis using the arithmetic processing result.

  From the result of the springback analysis, the amount of change in displacement caused by the springback is examined, and it is possible to determine how much the stress component value σx applied to the regions A1 and A2 has an influence on the springback without performing calculation processing for each side. It can be evaluated with only one calculation process.

  Further, after the springback analysis of the springback analysis unit 12 is performed, the region where the amount of springback changes the most is subdivided, and determination is performed until the size of the subdivided region becomes a predetermined value or less. For each divided area, the physical property value / physical quantity calculation processing unit 14 performs calculation processing, and the springback analysis unit 12 performs the springback analysis again. Can be identified, and efficient cause identification is possible. The physical property value / physical quantity calculation processing unit 14 can perform convergence calculation so that the physical property value and the physical quantity are changed as manipulated variables so that the springback change amount is equal to or less than the threshold, and at the same time, the division of the specific region is performed. Convergence calculation may be performed so as to change the region as an operation variable.

  In addition, when the press forming analysis unit 11 performs forming analysis using, for example, a finite element method and numerically obtains the stress and strain value distribution after forming, the physical property value / physical quantity calculation processing unit 14 selects a region. In this case, one or more elements can be selected as a calculation target area. The finite element method, which is an analysis method for solving field problems, is characterized by dividing the continuum into finite elements, and the elements are connected at a finite number of nodes located on their sides. The displacement field in the element is uniquely determined from the shape function defined for each element and the displacement of the node (“Nonlinear Finite Element Method” (Corona, published on December 20, 1994) No. 22 See page 35). For example, the distribution of the stress component σx obtained by the press forming analysis unit 11 is displayed, and the element having the largest σx value is set as the selection area, or the group of elements having the largest σx and the elements in contact with the element is set as the selection area. can do.

In addition, when the press forming analysis unit 11 performs forming analysis using, for example, an elementary analysis method and numerically obtains the stress and strain value distribution after forming, the physical property value / physical quantity calculation processing unit 14 selects a region. In this case, one or more calculation unit sections can be selected as a calculation target area.
The calculation unit category is, for example, molding analysis or spring using the primary analysis described in “Plastics and Processing (Journal of the Japan Society for Technology of Plasticity) Vol. 37, No. 431” (issued in December 1996) pages 1352 to 1359. It shows a small region segment that is the minimum for performing the calculation when the back analysis is performed.

In addition, when the press forming analysis unit 11 performs forming analysis using, for example, a finite element method and numerically obtains the stress and strain value distribution after forming, the physical property value / physical quantity calculation processing unit 14 selects a region. In this case, one or more integration points can be selected as a calculation target region.
An integration point is a point where approximate integration is generally performed by the finite element method. For example, “Static Solution FEM Plate Forming (Edited by the Japan Society for Technology of Plasticity, Corona, published on July 7, 2004)” It is described in detail on pages 80-82.
For example, in the finite element analysis of the press forming analysis unit 11, the workpiece is analyzed with a shell element having five integration points (1, 2, 3, 4, 5 from the back surface to the front surface) in the thickness direction. In addition, it is possible to set only 1 integration point closest to the plate back surface of the element selected in the physical property value / physical quantity calculation processing unit 14 and 5 integration points closest to the plate surface as a calculation target region. Thereby, the evaluation which isolate | separated the influence of the bending deformation received when contacting and deform | transforming the part which has a curvature of a metal mold | die can be performed.

  FIG. 6 is a flowchart of the springback generation cause specifying process of the springback cause site specifying process according to the embodiment of the present invention.

  In step S <b> 101, molding conditions are input to the molding condition input unit 18. Next, the process proceeds to step S102.

  In step S102, the press molding analysis unit 11 performs numerical analysis processing on the workpiece defined by the molding conditions, and calculates the distribution of stress and strain values after molding of the product to be press molded. Next, the process proceeds to step S103.

  In step S <b> 103, the physical property value / physical quantity calculation processing unit 14 determines a specific part to be a conversion target region. This specific part is set by the molding condition input means 11 or is automatically determined by the physical property value / physical quantity calculation processing unit 14. Next, the process proceeds to step S104.

  In step S104, the above-described arithmetic processing for converting the physical property value and the physical quantity is performed. Next, the process proceeds to step S105.

  In step S105, the springback amount is calculated based on the physical property value and the physical quantity subjected to the conversion process of the workpiece during press molding (SB = springback). Next, the process proceeds to step S106, and at the same time, the result of the springback amount is displayed on the screen in step S107.

  In step S106, it is determined whether the allowable value of springback is within the allowable value. If it is within the allowable value, this process is terminated. If it is equal to or greater than the allowable value, the process proceeds to step S108. In step S106 and step S108, a human may manually designate a specific part while watching the amount of change in springback.

  In step S108, the physical property value / physical quantity of the specific part and the workpiece are changed. Here, only a specific part may be changed, only the physical property value / physical quantity may be changed, or both of them may be simultaneously performed. Then, the process returns to step S105. The processing of step S105, step S106, and step S108 can be performed by a convergence calculation such that the amount of springback change is less than or equal to the threshold value, and is repeated until it becomes less than or equal to the threshold value.

  Note that the number of repetitions of this process is limited, and the process may be terminated when the limited number of repetitions is exceeded. In that case, the human examines the output data file “SB rem.casen.k” of the springback analysis unit 12 stored in the file storage unit 16, and the person looks at the springback amount output screen 19 to determine the optimum specific part. Can be obtained by searching.

FIG. 7 is a functional configuration diagram of a springback generation cause identifying apparatus according to another embodiment of the present invention.
Compared with the springback occurrence cause site specifying device 10A shown in FIG. 3, the springback occurrence cause site specifying device 10B shown in FIG. 7 is a partial residual stress removal processing unit instead of the physical property value / physical quantity calculation processing unit 21. 21.

The partial residual stress removal processing unit 21 is a processing unit that performs a process of removing the residual stress on a specific part that is considered to be a cause of occurrence of springback.
The specific part can be determined in advance as a specific part from the shape data of the workpiece, and the part to be subjected to the residual stress countermeasure can be determined. In this case, the specific part can be defined as setting data of the partial residual stress removal processing unit 21 or can be defined as input data from the molding condition input unit 18. The region to be selected may be performed by the molding condition input unit 18 (for example, a mouse or a keyboard) while looking at the shape displayed on the springback amount output screen 19, or the range is designated by a coordinate value or the like. It can also be done. Furthermore, a plurality of specific parts can be set.

Further, the specific part is based on the residual stress distribution of the data file “P org.k” or the data files “SB org.k” and “SB UVC.casen.k” obtained by the springback analysis unit 12. It can also be obtained by calculation based on the amount of spring back and / or the residual stress distribution.
That is, the residual stress concentration part at the bottom dead center of press molding may be set as the specific part, the residual stress concentration part at the time of springback may be set as the specific part, or the part having the maximum springback amount may be set as the specific part.

  Furthermore, the partial residual stress removal processing unit 21 can determine the amount of springback change by removing the residual stress without changing the physical property value of the molding data of the molded product, so that the strength of the molded product is maintained. In addition, the state of the molded product that suppresses the spring back can be obtained.

  In the determination of these specific parts, when the springback allowable value is not satisfied, various combination cases may be automatically generated to calculate the springback amount. In general, the portion where the amount of springback is maximized is often the outer peripheral portion of the molded product. Therefore, it is preferable to preferentially set the residual stress concentration portion as the specific portion. For example, the part where the residual stress is most concentrated is set as the highest priority selection candidate for the specific part, then the part where the springback amount is maximum is the second priority selection candidate for the specific part, and the residual stress is concentrated second. You may prescribe | regulate the site | part which is doing like the 3rd priority selection candidate etc. of a specific site | part.

  The partial residual stress removal processing unit 21 uses the output file “SB org.k” from the springback analysis unit 12 as input data to determine a specific part as described above, and to reduce the residual stress at the specific part to zero or more Value. The data file in which the residual stress of the specific part is changed is defined as “P trim case1.k”, and the corresponding specific part in “Porg.k” is the data of “P trim case1.k”. Replace the file after replacement with “P UVC case1.k”.

  The partial residual stress removal processing unit 21 outputs “P UVC case1.k” to the springback analysis unit 12 and causes the springback analysis unit 12 to calculate the springback amount. At this time, the springback analysis unit 12 saves the data file “SB UVC.Case1.k”, which is the calculation result, in the file storage unit 16, and sets the springback amount indicated in the data file to the springback output screen 19. To display.

The partial residual stress removal processing unit 21 also stores the amount of springback before the residual stress removal processing in “SB org.k” stored in the file storage unit 16 and the first in “SB UVC.Case1.k”. A comparison is made with the amount of spring back after the residual stress removal process for the second time, and it is determined whether the amount of spring back has decreased to be below a threshold value.
If the springback amount is less than or equal to the allowable value, the process is terminated. If the amount of springback is greater than or equal to a certain allowable value, the partial residual stress removal processing unit 21 performs processing for reducing the residual stress at the remaining residual stress portion, in the other specific portion and / or other residual stress. Partial residual stress treatment can also be performed by value. Other specific parts are candidates for the residual stress concentration part at the bottom dead center of press forming, the part with the largest amount of springback, the residual stress concentration part at the time of springback, etc., as mentioned above. The springback amount may be automatically calculated for the combination. At that time, “P trim casen.k” is generated for each n cases of the position coordinate data and stress data file of the specific part to be generated.

  The partial residual stress removal processing unit 21 performs “SB UVC.Casen” obtained by performing a springback calculation using “P UVC.casen.k” generated corresponding to “P trim caseen.k” generated for each of a plurality of cases as input data. . K ”may be stored in the file storage unit 16.

  FIG. 8 shows a flowchart of the springback cause site specifying process according to the embodiment of the present invention.

  In step S <b> 201, molding conditions are input to the molding condition input unit 18. Next, the process proceeds to step S202.

  In step S202, the press molding analysis unit 11 performs numerical analysis processing on the workpiece defined by the molding conditions, and calculates the distribution of stress and strain values after molding of the product to be press molded. Next, the process proceeds to step S203.

  In step S203, the spring back analysis unit 12 performs an analysis process for the amount of spring back of the press-molded workpiece. Next, the process proceeds to step S204.

  In step S204, the specific part from which the residual stress is removed is determined. This specific part is set by the molding condition input means 11 or is determined automatically by the partial residual stress removal processing unit 21. This automatic determination is determined based on the residual stress at the time of press molding or spring back, the amount of spring back, or the like. Next, the process proceeds to step S205.

  In step S205, a process of reducing or reducing the residual stress at the specific part to zero is performed. Next, the process proceeds to step S206.

  In step S206, the springback amount is calculated based on the shape or property data at the time of press molding in which the residual stress at the specific part is reduced or made zero. Next, the process proceeds to step S207, and at the same time, the result of the springback amount is displayed on the screen in step S208.

  In step S207, it is determined whether the allowable value of springback is within the allowable value. If it is within the allowable value, this process is terminated. If it is equal to or greater than the allowable value, the process proceeds to step S209. In step S207 and step S209, a human may manually designate a specific part while watching the amount of change in springback.

  In step S209, the specific part is changed. For the change of the specific part, one or more specific parts are selected based on a judgment material such as a residual stress concentration part at the time of press molding or spring back, or a spring back amount maximum part. In this step, the specific part may be manually selected via the molding condition input unit 18. Then, the process returns to step S205, and the above-described processing is repeated until the value falls within the allowable springback value in step S207.

  If a convergent solution cannot be obtained in relation to the allowable springback value, the number of repetitions of this process may be limited, and the process may be terminated with the limited number of repetitions. Even in such a case, the human examines the output data file “SB UVC.casen.k” of the springback analysis unit 12 stored in the file storage unit 16, and the human looks at the springback amount output screen 19. It is possible to search for and find the optimum specific part.

FIG. 9 is a hardware configuration diagram of a springback occurrence cause identifying apparatus according to an embodiment of the present invention. The processes in the press forming analysis unit 11, the spring back analysis unit 12, the physical property value / physical quantity calculation processing unit 14, and the partial residual stress removal processing unit 21 described above are defined in the program 100, and the program 100 is executed by the computer 90. You may let them.
The computer 90 includes a CPU 91 for executing necessary processing, a memory 92 for storing processing results (for example, RAM (Random Access Memory)), a display 93, for example, an input device 94 such as a keyboard and a mouse, a hard disk 95, a CD / CD An external storage device 96 such as a DVD drive, a NIC (network interface card) 97, and a printer 98 are provided. The computer 90 can be connected to another computer 90 </ b> A via a network 99 configured by an Ethernet (registered trademark) cable connected to the NIC 97.

  The program 100 is stored in a recording medium, loaded from the external storage device 96, or downloaded from another computer 90A via the network 99, and stored in the hard disk 95 of the computer 90 under the control of the CPU 91. Next, the saved program 100 is executed by the CPU 91 and stored in the memory 92 as an execution process or thread. For example, each process in the press forming analysis unit 11, the springback analysis unit 12, the physical property value / physical quantity calculation processing unit 14, or the partial residual stress removal processing unit 21 becomes an execution process or thread, and between each execution process or thread The data file or data described above is input / output. Each of these execution processes or threads may be distributed in the other computer 90A, and each process may be distributed by the computer 90 and the other computer 90A.

Moreover, the molding condition input unit 18 and the springback amount output screen 19 shown in FIGS. 3 and 7 may be an input device 94 and a display 93, respectively. The file storage unit 16 described above may be a hard disk 95. The program 100 may be stored in the hard disk 95. The above contour map output to the display 93 can be output to the printer 98.
Hereinafter, the present invention will be specifically described with reference to Examples 1 and 2.

  FIGS. 10A and 10B are diagrams showing a hat-shaped cross-sectional component subject to springback analysis according to an embodiment of the present invention, where FIG. 10A is a perspective view thereof, FIG. 10B is a cross-sectional view thereof, and a web surface W0, It consists of side walls W1, W2 and flanges F1, F2.

  For the numerical analysis performed by the press forming analysis unit 11 and the spring back analysis unit 12, commercially available plate forming simulation analysis software PAM-STAMP based on the finite element method was used. The springback analysis used the elastic analysis by the static implicit method.

  As the forming conditions, data of a high-strength steel plate having a plate thickness of 1.6 mm and a tensile strength of 780 MPa was used as the properties of the metal plate. The shape of the die (die, punch, holder) was modeled with shell elements and analyzed assuming a rigid body. The clearance between the die and the punch was 1.6 mm, the same as the plate thickness. A friction coefficient of 0.15 was input and 60 ton was set as the wrinkle holding load.

FIGS. 11A and 11B are views showing a cross-sectional position and a twist angle of a hat-shaped cross-sectional component according to an embodiment of the present invention, in which FIG.
The coordinate values of the points constituting the cross section at the positions A and B shown in FIG. Here, the springback amount is an angle θ.

FIG. 12 is a perspective view showing the specific area A3 according to the embodiment of the present invention.
FIG. 13 is a perspective view showing specific areas A4 and A5 according to an embodiment of the present invention.
FIG. 14 is a perspective view showing specific areas A6 to A9 according to an embodiment of the present invention.
FIG. 15A is a perspective view showing specific areas A10 to A14 according to an embodiment of the present invention, and FIG. 15B is a cross-sectional view showing specific areas A10 to A14 according to an embodiment of the present invention.
FIG. 16 is a perspective view showing specific areas A15 to A17 according to the embodiment of the present invention.
FIG. 17 is a perspective view showing specific areas A18 to A21 according to the embodiment of the present invention.
FIG. 24 is a perspective view showing the specific area A22 according to the embodiment of the present invention.
For specific area A3～A 21 shown in FIG. 12 to 16 will be described the result of the spring-back arithmetic processing by changing the stress component below.
The stress component before calculation at the integration point of the selected region is (σ _x0 , σ _y0 , σ _z0 , τ _xy0 , τ _yz0 , τ _zx0 ), and the strain component is (ε _x0 , ε _y0 , ε _z0 , γ _xy0 , γ _yz0 , γ _zx0 ), the stress components after the processing are (σ _x , σ _y , σ _z , τ _xy , τ _yz , τ _zx ), and the strain components are (ε _x , ε _y , ε _z , γ _xy , γ _yz , γ _zx ).
The plate thickness used was the value before the arithmetic processing as it was, and the elastic coefficient and plastic coefficient were used as they were the input values of the press forming analysis unit 11. The calculated stress and strain values were output as a calculation result file.

  Table 1 shows a study case for analyzing the relationship between the variable processed in a specific area and the twist angle. Table 1 shows specific areas and variables that have been changed in the arithmetic processing.

  Springback analysis was performed on all the elements belonging to each region using the computation-processed variables obtained by the physical property value / physical quantity computation processing unit 14.

  The coordinate values of the points constituting the cross section at the positions A and B shown in FIG. 11 were obtained from the obtained results by post processing software, and the angle θ formed by the web surface of the cross section was obtained.

FIG. 18 is a diagram illustrating a twist angle of the specific region A3 according to the embodiment of the present invention.
The result of performing the arithmetic process on σx in the region A3 has a larger θ than the result of the springback analysis when the arithmetic process is not performed. From this, it can be seen that σx in the region A3 has a great influence on θ, and it can be seen from this result that the value of σx in the region A3 may be changed in order to make the springback change amount equal to or less than the threshold value.

FIG. 19 is a diagram illustrating the twist angles of the specific regions A4 and A5 according to the embodiment of the present invention.
The result of performing the arithmetic process on the region A4 is larger than the result of performing the arithmetic process on the region A5, and is larger than the result of the springback analysis when the arithmetic process is not performed. From this, it can be seen that σx in the region A4 has a larger influence on θ than σx in the region A5. From this result, in order to make the springback change amount equal to or less than the threshold value, the σx of the region A4 is larger than the region A5. It can be seen that the value should be changed.

FIG. 20 is a diagram illustrating the twist angles of the specific areas A6 to A9 according to the embodiment of the present invention.
As a result of performing the arithmetic processing on the regions A6, A7, A8, and A9, θ is small and close to 0 compared to the springback analysis result when the arithmetic processing is not performed. From this, it can be seen that the stress σx of the regions A6, A7, A8, and A9 has a great influence on θ.

FIG. 21 is a diagram illustrating the twist angles of the specific regions A10 to A14 according to the embodiment of the present invention. As a result, among the results of the arithmetic processing performed on the regions A10 to A14, when arithmetic processing is performed on the region A11, θ is the smallest compared to the springback analysis result when the arithmetic processing is not performed. . From this, it can be seen that the stress of the region A11 has a great influence on θ.

FIG. 22 is a diagram illustrating the twist angles of the specific regions A15 to A17 according to the embodiment of the present invention. As a result, among the results of the arithmetic processing performed on the regions A15 to A17, when arithmetic processing is performed on the region A16, θ is the smallest compared to the springback analysis result when the arithmetic processing is not performed. From this, it can be seen that the stress of the region A16 has a great influence on θ.

FIG. 23 is a diagram illustrating the twist angles of the specific regions A18 to A21 according to the embodiment of the present invention. Region A16 was divided into regions A18, A19, A20, and A21, and springback analysis was performed for each of the divided regions. As a result, among the results of the arithmetic processing performed on the regions A18 to A21, when arithmetic processing is performed on the region A20, θ is the smallest compared to the springback analysis result when the arithmetic processing is not performed. From this, it can be seen that the stress of the region A20 has a great influence on θ. In this way, by first identifying a region having a large influence level in the global region and further performing region division and arithmetic processing within that range and investigating the impact level, it is possible to efficiently identify the cause of the occurrence of springback.

FIG. 25 is a diagram showing a twist angle when the calculation method of the specific area A22 according to the embodiment of the present invention is changed. As a result, in the case of the calculation method 2, θ is the smallest compared to the result of the springback analysis in the case where the calculation process is not performed or in the case of the calculation method 1. From this, it can be seen that θ can be reduced by making the selected region A22 have a stress distribution close to σx replaced by the calculation method 2.

FIG. 26 is a diagram showing the twist angle of the specific regions A23 and 24 according to the embodiment of the present invention. Here, the regions A23 and A24 are designated for each integration point in the plate thickness direction, and here, an analysis using five integration points was considered. The integration point numbers were sequentially numbered 1 to 5 from the inner surface (punch side) to the outer surface (die side). In the region A11, all integration points (integration points 1, 2, 4, 5) other than the integration point 3 on the center plane in the thickness direction are defined as a region A23. Further, in the region A11, the integration point 3 on the center plane in the thickness direction is defined as a region A24. According to the results of FIG. 20, the springback analysis results in the regions A23 and A24 are substantially the same, and the integration points (1, 2, 4, 5) other than the center surface in the plate thickness direction and the center in the plate thickness direction are The influence of the integration point 3 on the surface is almost the same. In this way, by specifying the area for each integration point in the plate thickness direction, the influence of the bending stress in the plate thickness direction (front and back) and the effect of the in-plane stress in the center plane in the plate thickness direction are distinguished to investigate the degree of influence. be able to.

27A and 27B are diagrams showing a hat-shaped cross-sectional component that is an object of springback analysis according to an embodiment of the present invention, where FIG. 27A is a perspective view thereof, FIG. 27B is a cross-sectional view thereof, Symmetric shape. The punch width used was 80 mm, the molding height was 80 mm, and the workpiece width was 100 mm.
For the numerical analysis performed by the press forming analysis unit 11 and the spring back analysis unit 12, commercially available plate forming simulation analysis software PAM-STAMP based on the finite element method was used. The springback analysis used the elastic analysis by the static implicit method.

As the forming conditions, data of a high-strength steel plate having a plate thickness of 1.6 mm and a tensile strength of 780 MPa was used as the properties of the metal plate. Further, the first region of 2 minutes as shown in FIG. 27 (b) taking into account the symmetrical shape of the hat cross-section analyzed in symmetrical conditions. The shape of the die (die, punch, holder) was modeled with shell elements and analyzed assuming a rigid body. The clearance between the die and the punch was 1.6 mm, the same as the plate thickness. The coefficient of friction was 0.15, and 10 ton was set as the wrinkle holding load.
Coordinate values before and after the springback analysis were obtained from the obtained results using the post processing software at the position shown in FIG. 27 (b), and the opening amount Δd of the cross section was obtained. Here, the springback amount is the opening amount Δd.

  Table 2 shows a study case for analyzing the relationship between the variable subjected to the arithmetic processing in the specific region and the opening amount. Table 2 shows specific areas and variables that are changed in the arithmetic processing.

  In Case 9, first, the stress component was changed by calculation with one element having the smallest element number as a specific region, and the springback analysis was performed. The same analysis was repeated in the order of the smallest element number, and all elements were analyzed.

In case 10, first, the integration point 5 of the element with the smallest element number is used as a specific region, the stress component is changed by calculation, and the springback analysis is performed. 5 was analyzed.
The stress component before calculation at the integration point of the selected region is (σ _x0 , σ _y0 , σ _z0 , τ _xy0 , τ _yz0 , τ _zx0 ), and the strain component is (ε _x0 , ε _y0 , ε _z0 , γ _xy0 , γ _yz0 , γ _zx0 ), the stress components after the processing are (σ _x , σ _y , σ _z , τ _xy , τ _yz , τ _zx ), and the strain components are (ε _x , ε _y , ε _z , γ _xy , γ _yz , γ _zx ).
The plate thickness used was the value before the arithmetic processing as it was, and the elastic coefficient and plastic coefficient were used as they were the input values of the press forming analysis unit 11. The calculated stress and strain values were output as a calculation result file.
Springback analysis was performed on all the elements belonging to each region using the computation-processed variables obtained by the physical property value / physical quantity computation processing unit 14.

FIG. 28 shows the elements of 5% of the total number of elements in order of increasing Δd among the opening amounts Δd of all elements obtained in the study case 9 according to the embodiment of the present invention. From this, it was found that elements that greatly affect Δd are concentrated in the region near the punch shoulder R.

FIG. 29 shows the elements of 5% of the total number of elements in order of increasing Δd among the opening amounts Δd of all elements obtained in the study case 10 according to the embodiment of the present invention. From this, it was found that elements having an integration point 5 that greatly affects Δd are concentrated in the region near the center of the vertical wall.

  As described above, the apparatus for identifying a springback generation site according to the present invention can identify the springback generation site by numerical analysis by examining the springback using a conventional actual device. It reduces costs. Moreover, since such a spring back generation | occurrence | production site | part identification apparatus is anticipated being applied to the whole workpiece, it brings a great profit in industry.

  The embodiments described above are merely given as typical examples, and it is obvious to those skilled in the art to combine the components of each embodiment, and variations and variations thereof. Those skilled in the art will understand the principles and claims of the present invention. It is apparent that various modifications of the above-described embodiment can be made without departing from the scope of the invention described in the above.

(A)-(c) is a cross-sectional schematic diagram of the shaping | molding member which shows the response | compatibility to the conventional spring back. (A)-(d) is a perspective view which illustrates the conventional method which searches the site | part which becomes the cause of generation | occurrence | production of a deformation | transformation by springback. The functional block diagram of the spring back generation | occurrence | production cause site | part identification apparatus by one Embodiment of this invention is shown. It is a figure which shows the coordinate system used by the finite element method by one Embodiment of this invention. It is a perspective view which shows the example of the area | region selection of the workpiece by one Embodiment of this invention. It is a flowchart of the spring back generation | occurrence | production site | part identification process by one Embodiment of this invention. The functional block diagram of the spring back generation | occurrence | production cause site | part identification apparatus by one Embodiment of this invention is shown. It is a flowchart of the springback generation | occurrence | production cause identification process of the springback cause site | part identification apparatus by one Example of this invention. It is a hardware block diagram of the springback cause site | part identification process by one Embodiment of this invention. It is the perspective view and sectional drawing which show the example of a to-be-processed object. (A), (b) is a figure which shows the cross-sectional position and twist angle of the hat-shaped cross-section part by the Example of this invention. It is a perspective view which shows specific area | region A3 by the Example of this invention. It is a perspective view which shows specific area | region A4, A5 by the Example of this invention. It is a perspective view which shows specific area | region A6-A9 by the Example of this invention. (A) is a perspective view which shows specific area | region A10-A14 by the Example of this invention, (b) is sectional drawing which shows specific area | region A10-A14 by the Example of this invention. It is a perspective view which shows specific area | region A15-A17 by the Example of this invention. It is a perspective view which shows specific area | region A18-A21 by the Example of this invention. It is a figure which shows the twist angle of specific area | region A3 by the Example of this invention. It is a figure which shows the twist angle of specific area | region A4, A5 by the Example of this invention. It is a figure which shows the twist angle of specific area | region A6-A9 by the Example of this invention. It is a figure which shows the twist angle of specific area | region A10-A14 by the Example of this invention. It is a figure which shows the twist angle of specific area | region A15-A17 by the Example of this invention. It is a figure which shows the twist angle of specific area | region A18-A21 by the Example of this invention. It is a perspective view which shows specific area | region A22 by the Example of this invention. It is a figure which shows the twist angle at the time of changing the calculation method of specific area | region A22 by the Example of this invention. It is a figure which shows the twist angle of specific area | region A23-A24 by the Example of this invention. (A), (b) is a figure which shows the cross-sectional position and opening amount of the hat bending part by the Example of this invention. It is a figure which shows the result of the examination case 9 by the Example of this invention. It is a figure which shows the result of the examination case 10 by the Example of this invention.

Explanation of symbols

10A, 10B Springback occurrence cause identifying device 11 Press molding analysis unit 12 Springback analysis unit 14 Physical property / physical quantity calculation processing unit 16 File storage unit 18 Molding condition input unit 19 Springback amount output screen 21 Partial residual stress removal processing unit

Claims (3)

(I) a press molding analysis step in which a computer numerically analyzes molding conditions for press molding to obtain molding data of a press molded product;
(Ii) The stress in the three-dimensional coordinate system x, y, z direction, the xy plane, and the yz plane for a partial region of the press-molded product among the molding data of the press-molded product obtained in step (i) by the computer , An arithmetic processing step for performing arithmetic processing to change any one of the factors of shear stress in the zx plane ;
(Iii) a springback amount calculating step in which the computer calculates a springback amount based on the result of the arithmetic processing performed in step (ii);
(Iv) a computer obtains a springback amount difference between the springback amount calculated in step (iii) and the springback amount calculated without performing the arithmetic processing in step (ii);
(V) The computer performs the steps (ii) to (iv) for at least one other region different from the partial region to obtain a springback amount difference, and performs the calculation processing of the partial region. Comparing the resulting springback amount difference with the springback amount difference resulting from the calculation processing of the other region to identify a region that gives the maximum springback amount difference ;
(Vi) The computer divides the region giving the maximum springback amount difference, and the steps (ii) to (ii) are performed for each of the divided regions until the size of the divided region becomes a predetermined value or less. v) , and
Wherein the part that causes the scan pulling back, to identify the stress or shear stress, springback cause specifying method. A press molding analysis unit that numerically analyzes the molding conditions of press molding and obtains molding data of the press molded product,
A numerical analysis of the molding data, and a springback analysis unit for calculating a springback amount;
Among the molding data of the press-molded product, any one of the factors of the stress in the three-dimensional coordinate system x, y, z direction of the partial region of the press-molded product, the shear stress of the xy plane, the yz plane, and the zx plane Performing an arithmetic process for changing one, causing the springback analysis unit to calculate a springback amount based on the result of the arithmetic process, and performing the arithmetic process on at least one other region different from the partial region And causing the springback analysis unit to calculate a springback amount based on the result of the calculation process, and further causing the springback analysis unit to calculate a springback amount based on molding data that is not subjected to the calculation process, The amount of springback calculated based on the result of the arithmetic processing in the partial area and the arithmetic processing in the other area , An arithmetic processing unit that obtains each springback amount difference from the calculated springback amount without performing the arithmetic processing, and identifies a region that gives the maximum springback amount difference ,
Have
The arithmetic processing unit divides the region that gives the maximum springback amount difference, and changes the stress or shear stress for each of the divided regions until the size of the divided region becomes a predetermined value or less. performing arithmetic processing, and identifies the sites responsible for the scan pulling back, the stress or shear stress, springback cause a particular device. (I) a press molding analysis procedure for numerically analyzing press molding molding conditions to obtain molding data of a press molded product;
(Ii) Three-dimensional coordinate system x, y, z direction stress, xy plane, yz plane, zx plane for a partial region of the press molded product among the molding data of the press molded product obtained in step (i) An arithmetic processing procedure for performing arithmetic processing to change any one of the shear stress factors of
(Iii) a springback amount calculation procedure for calculating a springback amount based on the result of the arithmetic processing;
(Iv) an arithmetic processing procedure for obtaining a springback amount difference between the springback amount calculated in step (iii) and the springback amount calculated without performing the arithmetic processing in step (ii) ;
(V) Performing the steps (ii) to (iv) for at least one other region different from the partial region to obtain a springback amount difference, and a spring resulting from the arithmetic processing of the partial region A procedure for comparing a back amount difference and a spring back amount difference resulting from the calculation processing of the other region to identify a region that gives the maximum spring back amount difference ;
(Vi) dividing the region giving the maximum springback amount difference, and performing the steps (ii) to (v) for each of the divided regions until the size of the divided region becomes a predetermined value or less. Steps to do ,
To the computer ,
A springback generation cause identifying program characterized by identifying a site, stress or shear stress that causes springback.

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