Technical field
[0001]
The present invention, fracture determination apparatus, fracture determination program, and a method thereof.
BACKGROUND
[0002]
　Recently, from the request of the collision safety and weight reduction, while the application of high-strength steel sheet is rapidly advanced to the automobile body. High-strength steel sheet used for automobile body, by increasing the reaction force at the time of collision without increasing the plate thickness, it is possible to increase the absorbed energy. However, by reducing the ductility of the steel sheet with high strength of a steel sheet, there is a possibility that the steel sheet is broken upon collision deformation of the vehicle at the time of press forming, and an automobile. To determine the state of the steel sheet during press molding and during collision deformation, FEM (Finite Element Method, FEM) forming simulation and collision deformation simulation by has been performed, to the precise fracture criterion in their simulation there is a growing need.
[0003]
　In order to evaluate the margin for the breaking of time or when collision performance evaluation moldability evaluation, use the maximum principal strain and minimum principal strain and the forming limit diagram giving the fracture limit with the relationship (FLD, Forming Limit Diagram) it is known to (e.g., see Patent documents 1 and 2). Maximum main strain and minimum principal strain elements which are obtained by simulating the press-forming and a collision deformation by FEM, compares the forming limit line shown in forming limit diagram, whether each element is broken it is determined whether the.
[0004]
　However, the strain is obtained by simulation by FEM, the element size of the analytical model, which is one of the analysis conditions of the simulation (gauge length, mesh size) of the fracture criterion results differ by the size of the element size since it depends on the there is a problem.
[0005]
　Therefore, when the press-forming simulation by FEM, and calculates the fracture limit strain in accordance with the element size, using a breaking strain limit computed, it is known that the element to determine whether or not broken are (e.g., see Patent Document 3). The fracture determination method described in Patent Document 3, breakage of the steel sheet in accordance with the element size when press-molding a relatively low strength steel sheet, such as tensile strength 270MPa grade steel and 440MPa grade steel becomes predictable.
CITATION
Patent Document
[0006]
Patent Document 1: JP 2000-107818 Patent Publication
Patent Document 2: JP 2009-61477 JP
Patent Document 3: JP 2011-147949 JP
Summary of the Invention
Problems that the Invention is to Solve
[0007]
　Recently, steel sheets of ultra high strength of at least referred tensile strength 980MPa with ultrahigh-tensile have been developed. The fracture determination method described in Patent Document 3, the tensile although the strength 270MPa grade steel and 440MPa grade relatively low strength steel such as a steel plate can be predicted properly fracture corresponding to element size, tensile strength 980MPa above about steel ultra high strength can not be properly predict fracture corresponding to the element size.
[0008]
　Accordingly, an object of the present invention is to provide a properly predictable fracture judgment apparatus fracture in accordance with the element size of the steel material containing more than tensile strength 980MPa ultra high strength steel.
Means for Solving the Problems
[0009]
　The present invention to solve such problems, fracture determination device described below is intended to break determining program, and the fracture determination method and gist.
　(1) the material properties and thickness of the steel, as well as the input information element indicating an element size in the analysis model used for deformation simulation of steel by the finite element method, the forming limit value in the reference element size is an element size as a reference a storage unit for storing the reference forming limit value information indicating a reference forming limit value indicating, and
　based on the reference forming limit value information, generates a reference forming limit value according to the material properties and thickness included in the input information a reference forming limit value generation unit,
　by using the tensile strength of the steel, the target forming limit value generation unit for generating object forming limit value by changing the reference shaping limit predict the forming limit in element size,
　run the deformation simulation using the input information, a simulation executing unit that outputs modification information including the strain of each element,
　the elements included in the deformation information And principal strain determining section for determining a main strain respectively,
　the main strain strain respective maximum principal of the determined elements and minimum principal strain and, on the basis of the target forming limit line which is defined by the target molding limit , fracture determination apparatus characterized by having a fracture determination unit that determines whether each of which breakage of the elements in the analysis model.
　(2) target forming limit value generation unit predicts the element size, the forming limit value using a first coefficient obtained from a tensile strength of the steel material, fracture determination apparatus according to (1).
　(3) subject forming limit value generation unit predicts a first coefficient and a second coefficient including the maximum principal strain and the first coefficient in the reference element size, the maximum principal strain in the element size using the element size , fracture determination apparatus according to (2).
　(4) The second factor is a function of the maximum principal strain and the first coefficient in the reference element size, fracture determination apparatus according to (3).
　(5) the second coefficient is proportional to the maximum principal strain at the reference element size to the logarithm of the value obtained by dividing the first coefficient, fracture determination apparatus according to (4).
　(6) Other forming limit value generator, predicted a first coefficient, the second coefficient and the exponent and the maximum principal strain in the element size using the product of the operation result of exponentiation operation to base element size to break determination apparatus according to any one of (2) to (5).
　(7) Other forming limit value generation unit, and the element size, using a second coefficient obtained from a tensile strength of the steel to predict the forming limit value, fracture determination apparatus according to (1).
　(8) the second coefficient is a function of the maximum principal strain and the first coefficient in the reference element size, fracture determination apparatus according to (7).
　(9) The second factor is proportional to the maximum principal strain at the reference element size to the logarithm of the value obtained by dividing the first coefficient, fracture determination apparatus according to (8).
　(10) Other forming limit value generator generates a target forming limit value using a function of the tensile strength of the element size and the steel forming limit value predicting equation,
　forming limit value prediction equation, [rho is strain ratio in it, M is an element size indicating the size of the elements of the analysis model used in the simulation by FEM, epsilon 1 is the maximum principal strain in the element size M, epsilon 2 time the is the minimum principal strain in element size M , the first coefficient k1 and the second coefficient k2
[number 1]

is represented by the first coefficient k1 is well tensile strength TS of the material of the steel sheet, the coefficient γ and [delta]
[Equation 2]

is represented by the second coefficient k2 is the maximum principal strain ε in the reference element size 1B from and coefficient eta
[number 3]

represented by the fracture judgment apparatus according to (1).
　(11) when the breaking determination unit that the maximum of the determined elements principal strain and minimum principal strain exceeds the threshold given by the object forming limit line, it is determined that the element is broken, (1) - (10 fracture determination apparatus according to any one of).
　(12) and a target forming limit stress generator for generating a target forming limit stress by changing the target forming limit value,
　convert each of the maximum of the determined elements principal strain and minimum principal strain to maximum principal stress and the minimum principal stress a strain stress conversion unit to further include a
　fracture determination unit determines that the maximum principal stress and the minimum principal stress of the transformed elements when exceeding the target forming limit stress element is broken, (1 ) fracture determination apparatus according to any one of - (10).
　(13) deformation simulation is a collision deformation simulation of the vehicle formed by the steel, (1) fracture judgment apparatus according to any one of - (12).
　(14) based on the reference forming limit value information indicating a forming limit value corresponding to the forming limit line in the reference element size indicating the reference made element size, an element size in the analysis model used for deformation simulation of steel by FEM generates a reference forming limit value according to the material properties and thickness of the steel contained in the input information indicating the element,
　using a tensile strength of element size and steel, molded in element size by changing the reference shaping limits It generates a target molding limits to predict limits,
　by performing the deformation simulation using the input information, and outputs the modification information including the strain of each element,
　each of the largest elements in the deformation information determine the principal strain and minimum principal strains,
　the respective maximum main strain and minimum principal strain elements principal strain is determined, the target forming limit value Based on the target forming limit line to be constant, fracture determination method each element in the analysis model, which comprises a determining, that whether breaks.
　(15) based on the reference forming limit value information indicating a forming limit value corresponding to the forming limit line in the reference element size indicating the reference made element size, an element size in the analysis model used for deformation simulation of steel by FEM generates a reference forming limit value according to the material properties and thickness of the steel contained in the input information indicating the element,
　using a tensile strength of element size and steel, molded in element size by changing the reference shaping limits It generates a target molding limits to predict limits,
　by performing the deformation simulation using the input information, and outputs the modification information including the strain of each element,
　each of the largest elements in the deformation information determine the principal strain and minimum principal strains,
　the respective maximum main strain and minimum principal strain elements principal strain is determined, the target forming limit value Based on the target forming limit line to be constant, determines whether each element in the analysis model is broken, the fracture criterion program characterized by executing the process to the computer.
Effect of the invention
[0010]
　In one embodiment, the fracture of the tensile strength 980MPa or more ultra-high-strength steel can be properly predicted.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
[1] a shaping limit line generated using the forming limit prediction expression is a diagram showing the relationship between the actual measurement value.
2 is a diagram showing a fracture determining apparatus according to the first embodiment.
3 is a flowchart of a fracture determination process by breaking determining apparatus according to the first embodiment.
4 is a diagram showing a fracture determination apparatus according to the second embodiment.
5 is a flowchart of a fracture determination process by breaking determining apparatus according to the second embodiment.
6 is a diagram showing a mold manufacturing system which is an example of application of the fracture determination apparatus according to the embodiment.
Load in [7] Tensile according fracture determination device according to a comparative example simulation test results - a diagram showing the relationship of strain between reference points.
[Figure 8] is a diagram showing the displacement at break determination apparatus tensile test simulation results of in accordance with the first embodiment, (a) shows the element size indicates when 2 mm and is (b) and the element size, It indicates when the 3 mm and indicates when the (c) is an element size 5 mm.
[9] load at break determination device Tensile simulation test results according to the first embodiment - is a graph showing the relationship strain between reference points.
DESCRIPTION OF THE INVENTION
[0012]
　With reference to the accompanying drawings, fracture determination apparatus, fracture determination program, and its method will be described. However, the technical scope of the present invention is not limited to the embodiments shown.
[0013]
　(Overview of the fracture determination device according to the embodiment)
　fracture determination device according to the embodiment, the reference forming limit value information created by actual measurement or the like, by material properties and thickness in the input information elements by the Finite Element Method is determined, the reference forming limit value in the reference element size, modified by a function of the tensile strength of the element size and the steel is the size of the elements in the analysis model forming limit value prediction equation. Implementation fracture judgment apparatus according to the embodiment, by using the target forming limit values that have been changed by a function of the tensile strength of the element size and the steel is the size of the elements in the analysis model forming limit value predicting equation, the tensile strength It may be used subject forming limit value according to. Break determining apparatus according to the embodiment, tensile Since the object forming limit value corresponding to the intensity can be used, it is possible to predict fracture above tensile strength 980MPa of ultra high strength steel. Hereinafter, the principle of breaking determination processing in fracture determination apparatus according to the embodiment before describing fracture determination apparatus according to the embodiment will be described.
[0014]
　The inventors of the present invention includes a reference forming limit value information corresponding to the forming limit curve prepared by actual measurement or the like, is determined by the material properties and thickness of the steel sheet is used as a judgment target, reference forming limit at the reference element size values ​​were found maximum principal strain forming limit value predicting equation for predicting the in element size based on the relationship of the maximum principal strain and the element size and the reference element size in the analytical model of the steel sheet is used as a judgment target. That is, the inventors of the present invention, the reference forming limit value corresponding to the reference shaping limit line as a reference, is generated by modifying the forming limit value prediction expression which is a function of the tensile strength and element size steel It was found to determine the presence or absence of fracture using object forming limit value. Depending on the element size, by changing the forming limit value using a forming limit prediction equation allows fracture determination in accordance with the element size.
[0015]
　Equation (1) shown below are forming limit value prediction equation found by the inventors of the present invention.
[0016]
[Formula 4]

[0017]
　Here, [rho is strain ratio, M is an element size (mm) indicating the size of the element of interest in the simulation by FEM, epsilon 1 is the maximum principal strain in the element size M, epsilon 2 elements it is the minimum principal strain in size M. A multiplier element size M k1 is the first coefficient, the maximum strain mainly in reference element size as k2 is an index of the element size M will be described with reference to equation (2) and (4) shown below it is a second coefficient which depends on. Equation (1), the maximum principal strain ε in element size M based on the relationship of the maximum principal strain and the element size M and the reference element size 1 is an equation to predict. In the formula (1), the maximum principal strain ε in element size M 1 has a first coefficient k1, an operation result to be calculated by the calculation by powers operation to the base and element size M and the second coefficient k2 and index it is shown that is generated by multiplying.
[0018]
　Equation (2) below is an expression indicating the equation (1) in more detail.
[0019]
[Formula 5]

[0020]
　Here, TS denotes the tensile strength [MPa] of the material such as a steel plate, epsilon 1B shows the maximum principal strain at the reference element size, gamma, the δ and η indicates a coefficient. γ is a negative value, [delta] is a positive value. Coefficient γ and δ may vary depending on the strain ratio [rho. Coefficient η is determined by the reference element size. From equation (1) and (2), the first coefficient k1 is
[0021]
[Number 6]

[0022]
　In shown. In the formula (3), the first coefficient k1 is strain ratio ρ is proportional to the tensile strength TS of the steel at the time of constant, i.e., is shown to be a function of the tensile strength of the strain ratio ρ and steel. Equation (3), the first coefficient k1 has shown that proportional to the tensile strength TS of the steel, according to the tensile strength TS of steel increases, the maximum principal strain epsilon 1 and the minimum principal strain epsilon 2 that is increased It is shown. First coefficient k1 is a positive value, gamma is a negative value, [delta] is because it is a positive value, the first coefficient k1 in accordance with the tensile strength TS of steel increases decreases. Further, from equation (1) and (2), the second coefficient k2 is
[0023]
[Number 7]

[0024]
　In shown. In the formula (4), the second coefficient k2, the maximum principal strain ε in the reference element size 1B it is and function of the first coefficient k1 is shown. More specifically, in the equation (4), the second coefficient k2, the maximum principal strain ε in the reference element size 1B it is shown that is proportional to and a function of the logarithm of the first coefficient k1. More specifically, in the equation (4), the second coefficient k2, the maximum principal strain ε in the reference element size 1B to be proportional to the logarithm of the value obtained by dividing the first coefficient k1 shown.
[0025]
　Figure 1 shows the formula (1) to (4) forming limit line generated using the target forming limit value changed by the molding limit prediction equation described with reference to the relationship between the actual measurement value it is a diagram. 1, the horizontal axis is the minimum principal strain epsilon 2 and a Y axis maximum principal strain epsilon 1 shows a. Also, circles indicate the measured values when the gauge length of 10 mm. Square marks gauge length indicates the measured value at 6 mm and triangles gauge length is 2 [mm shows the measured value when the]. Curve 101 is the reference forming limit curve prepared using the calculated reference forming limit value from the generated reference forming limit value information and material properties and the sheet thickness from measured data of the gauge length of 10 mm. is there. Curves 102 and 103 were generated using the equation (1) to the target forming limit values that have been changed from the reference forming limit value indicated by the curve 101 by reference to the forming limit line prediction formula described by (4) representing the target forming limit line. Curve 102 shows the forming limit line when the gauge length of 6 mm and a curve 103 represents a forming limit line when the gauge length of 2 mm. Incidentally, was used to generate the actual measurement and the forming limit line shown in FIG. 1, the tensile strength of the material properties of the steel sheet is 1180 [MPa], the plate thickness is 1.6 mm. In general, since the strain at rupture in the vicinity it is localized strain higher closer to the fracture portion has occurred. Therefore, as the gauge length for reading the distortion of the fracture portion is shortened, to read high strain occurring in breaking the vicinity, the value of the forming limit is higher. That is, forming limit line in FIG. 1 is located above a more. Also, when compared to steel other material properties, since in general the tensile strength TS of the steel is the steel ductility is reduced significantly, the value of the strain at break in the vicinity is reduced. Therefore forming limit curve in FIG. 1 will be more positioned below.
[0026]
　As shown in FIG. 1, the object forming limit lines which are modified using the reference forming limit value from the reference forming limit line, and the measured values ​​both in the case of the gauge length of 2 [mm] and 6 mm. accuracy well matched, forming limit line prediction equation according to the present invention is shown to have a high accuracy.
[0027]
　(Configuration and Function of the fracture determination apparatus according to the first embodiment)
　FIG. 2 is a diagram showing a fracture determining apparatus according to the first embodiment.
[0028]
　Fracture determination apparatus 1 includes a communication unit 11, a storage unit 12, an input unit 13, an output unit 14, a processing unit 20. Communication unit 11, a storage unit 12, input unit 13, output unit 14 and the processor 20 are connected to each other via a bus 15. Fracture determination apparatus 1, by forming limit value prediction formula using the tensile strength of the steel, to generate a target forming limit value showing the molding limit in element size by changing the reference forming limit value, such as an automobile by FEM performing collision deformation simulation of the vehicle. Fracture determination apparatus 1 determines based on the generated object forming limit value, since collision respective maximum deformation simulation output by elements principal strain and minimum principal strain, whether each element is broken. In one example, fracture determination apparatus 1 is a personal computer simulations that can be performed by FEM.
[0029]
　The communication unit 11 has a wired communication interface circuit such as Ethernet (registered trademark). The communication unit 11 communicates with the server or the like (not shown) via a LAN.
[0030]
　Storage unit 12 includes, for example, a semiconductor memory device, a magnetic tape unit, a magnetic disk device, or at least one of the optical disk apparatus. Storage unit 12 stores an operating system program used for processing in the processing unit 20, a driver program, an application program, stores the data, and the like. For example, the storage unit 12 as an application program, stores the break determining program for executing the fracture determination process for determining the respective breaking element. Further, the storage unit 12 as an application program, stores the collision deformation simulation program for performing a collision deformation simulation using FEM. Break determining program and a collision deformation simulation program, etc., for example, a CD-ROM, a computer readable portable recording medium such as a DVD-ROM, or may be installed in the storage unit 12 using such as a known setup program.
[0031]
　The storage unit 12 stores various data used in fracture determination process and the collision deformation simulation. For example, the storage unit 12 stores the input information 120 and the reference forming limit value information 121 or the like is used in fracture determination process and the collision deformation simulation.
[0032]
　Input information 120 includes material properties and thickness of the steel, and the element size indicating the size of the elements in the collision deformation simulation by the finite element method. Material properties of the steel comprises stress-strain (stress-strain, S-S) curve, each coefficient in equation Swift used for fitting S-S curve, Young's modulus, Poisson's ratio and density or the like. Reference forming limit value information 121 is used to define the reference forming limit value indicating a forming limit value corresponding to the forming limit line in the reference element size indicating the element size to be a reference for each material properties and thickness. In one example, the reference forming limit value information 121 includes a reference forming limit value corresponding to the material properties and the actually measured reference forming limit line for each thickness. In another example, the reference shaping limit line information 121, corresponding to the reference shaping limit line corrected as forming limit curve obtained from the theoretical formula of Storen-Rice matches the actually measured reference forming limit line including the reference forming limit value.
[0033]
　The storage unit 12 stores the input data of the collision deformation simulation by FEM. Further, the storage unit 12 may temporarily store temporary data associated with a predetermined processing.
[0034]
　The input unit 13 may be any device as long as possible input data, for example, a touch panel, a keyboard or the like. Operator uses the input unit 13 can input characters, numbers, symbols, or the like. The input unit 13, when operated by the operator, generates a signal corresponding to the operation. The generated signal, as an indication of the operator, is supplied to the processing unit 20.
[0035]
　The output unit 14 may be any device as long as capable of displaying such video or image, for example, a liquid crystal display or an organic EL (Electro-Luminescence) display or the like. The output unit 14, and video corresponding to the video data supplied from the processing unit 20, and displays an image or the like in accordance with image data. The output unit 14, the display medium such as paper, the image may be an output device for printing images or characters, and the like.
[0036]
　Processor 20 has one or a plurality of processors and their peripheral circuitry. Processing unit 20, which centrally controls the overall operation of the fracture judgment apparatus 1, for example, a CPU. Processor 20, programs stored in the storage unit 12 (driver program, an operating system program and application programs) executes processing based on the. The processing unit 20 can execute a plurality of programs (application programs) in parallel.
[0037]
　Processor 20 includes an information acquisition unit 21, a reference forming limit value generator 22, a target forming limit value generator 23, a simulation execution unit 24, and the principal strain determining section 25, a fracture determining unit 26, the simulation results and an output unit 27. These units are functional modules implemented by a program executed by the processor of the processing unit 20 is provided. Alternatively, these units may be implemented to break determination device 1 as firmware.
[0038]
　(First fracture determination process by breaking determination device according to the embodiment)
　FIG. 3 is a flow chart of determining fracture judgment processing whether each break of the fracture determination device 1 is a collision deformation simulation element. Break determination process shown in FIG. 3, in advance based on the program stored in the storage unit 12, are executed in cooperation with the elements of the fracture determination apparatus 1 mainly by the processor 20.
[0039]
　First, the information acquisition unit 21 acquires the material properties such as tensile strength, acquires the input information 120 including the thickness and element size from the storage unit 12 (S101), the reference forming limit value information 121 from the storage unit 12 (S102).
[0040]
　Then, the reference forming limit value generator 22, based on the reference forming limit value information 121 obtained by the processing of S102, and generates a reference forming limit value corresponding to the material properties and thickness obtained by the processing of S101 (S103). Specifically, reference shaping limit value generator 22 may, for example, based on the material properties and thickness of the combinations included in the input information 120 from the reference forming limit values ​​of groups stored in the storage unit 12, by selecting a group of reference forming limit value, generating a reference forming limit value corresponding to the material properties and thickness. In this case, the reference forming limit value of plurality of groups included in the reference forming limit value information 121 is actually measured values. The reference forming limit value generator 22 may, for example, correspond to the material properties and thickness by correcting the set of reference forming limit value stored in the storage unit 12 in material properties and the measured value according to the thickness generating a reference molding limit. In this case, the reference forming limit value generation unit 22 first generates a forming limit value from the theoretical formula of Storen-Rice. Then, the reference forming limit value generator 22, based on the measured value stored in the storage unit 12 as a shift amount according to the material properties and thickness, shifting the forming limit value generated from the theoretical formula of Storen-Rice generating a reference forming limit value corresponding to the material properties and thickness and.
[0041]
　Then, the target forming limit value generator 23, obtained in the process of the forming limits value predicting equation shown in equation (1) to (4), by changing the reference forming limit value generated by the processing of S103 S101 elements generating a target forming limit value showing the molding limit in size (S104).
[0042]
　Then, the simulation execution unit 24, based on the acquired input information in the process of S101, by using the mesh data stored in the storage unit 12, the collision deformation simulation of a vehicle such as an automobile formed by steel FEM executed by (S105). Simulation execution unit 24, as the execution result of the simulation, the displacement of the contact point, and sequentially outputs the modification information including the stress strain and elements of the element for each element.
[0043]
　Then, the main strain determining unit 25, each of the maximum principal strain epsilon of elements in the modification information outputted in the process of S105 1 and the minimum principal strain epsilon 2 to determine (S106).
[0044]
　Then, breaking determining unit 26, each of the maximum principal strain epsilon of the determined element in the process of S106 1 and the minimum principal strain epsilon 2 and, subject forming limit defined by the target forming limit value generated by the processing of S103 based on the line, each element determines whether the fracture (S107). Break determining section 26, the maximum principal strain epsilon 1 and the minimum principal strain epsilon 2 when plotting point determined by does not exceed the threshold value given by the target forming limit line, it is determined that the element is not broken, the maximum principal strain epsilon 1 and minimum principal strain epsilon 2 when plotting point determined by exceeds the threshold given by the object forming limit line, it is determined that the element is broken. In one example, the target forming limit line is calculated as an approximation expression of the target molding limit.
[0045]
　Then, breaking determining unit 26, and determines an element is broken (S107-YES), the element outputs the element breaking information indicating that broke the simulation execution unit 24 (S108). Simulation execution unit deletes the determined elements and breaking, i.e. can be removed from the data of the crash deformation simulation.
[0046]
　Then, the simulation result outputting unit 27, a simulation execution unit 24 outputs the modification information are sequentially output (S109). Then, the simulation execution unit 24 determines whether a predetermined simulation end condition is satisfied (S110). Simulation end time is obtained from the input data. Until the simulation end condition is determined to be satisfied, the process is repeated.
[0047]
　(Effect of the fracture determination apparatus according to the first embodiment)
　fracture determination apparatus 1, using the modified object forming limit value in accordance with the element size by forming limit value prediction formula using the tensile strength of the steel breaking to determine whether the does not rely on element size, it is possible to perform an accurate fracture prediction in accordance with the tensile strength of the steel.
[0048]
　It is possible to perform an accurate fracture prediction by breaking determining apparatus 1, it is possible to significantly reduce the number of crash tests in actual automobile member. Furthermore, in some cases, it is possible to omit the crash test of an actual automobile parts.
[0049]
　By performing an accurate fracture prediction by breaking determining apparatus 1, it is possible to design a member for preventing breakage at the time of collision on a computer, can contribute to shortening of the significant cost savings, development time.
[0050]
　(Configuration and Function of the fracture determination apparatus according to the second embodiment)
　FIG. 4 is a diagram showing a fracture determination apparatus according to the second embodiment.
[0051]
　Fracture judgment apparatus 2, processing unit 30 is different from the fracture judgment apparatus 1 that is arranged instead according to the first embodiment of the processor 20. Processing unit 30, to have a target forming limit stress generator 34 and strain stress converter 35, as well as breaking the determination unit 36 ​​is different from the processing unit 30 to be arranged in place of the fracture determining unit 26. Object forming limit stress generating unit 34, configuration and functions of the components of the strain stress converter 35 and the break determining section 36 except the break judgment apparatus 2, the components of the fracture determination apparatus 1 of the same reference numerals are attached configuration and function since the same as, and a detailed description thereof will be omitted.
[0052]
　(Second fracture determination process by breaking determination device according to the embodiment)
　FIG. 5 is a flowchart of determining fracture judgment processing whether each break of the fracture judgment apparatus 2 is collision deformation simulation element. Break determination process shown in FIG. 5, in advance based on the program stored in the storage unit 12, are executed in cooperation with the elements of the fracture judgment apparatus 2 mainly by the processor 30.
[0053]
　Processing of S201 ~ S204 is the same as the processing of S101 ~ S104, and a detailed description thereof will be omitted. Object forming limit stress producing unit 34 changes the reference forming limit value generated by the processing of S204 to generate a target forming limit stress (S205).
[0054]
　Then, the simulation executing unit 24 based on the input information, by using the mesh data stored in the storage unit 12, performed by FEM collision deformation simulation when a predetermined collision has occurred (S206). Then, the main strain determining unit 25, each of the maximum principal strain epsilon of elements in the modification information outputted in the process of S205 1 and the minimum principal strain epsilon 2 to determine (S207).
[0055]
　Then, the strain stress converter 35 is outputted determined elements each maximum principal strain epsilon in the processing of S207 1 and the minimum principal strain epsilon 2 converts to maximum principal stress and the minimum principal stress (S208).
[0056]
　Then, breaking determination unit 36, each of the maximum principal stress and the minimum principal stress of the transformed elements in the process of S208, on the basis of the target forming limit stress generated in the process of S205, each element is broken determines whether (S209). Break determining section 36, when the maximum principal stress and the minimum principal stress does not exceed the target forming limit stress, it is determined that the element is not broken, when the maximum principal stress and the minimum principal stress exceeds the target forming limit stress, It determines that the element is broken. Processing of S210 ~ S212 is the same as the processing of S108 ~ S110, and a detailed description thereof will be omitted.
[0057]
　(Modification of the fracture determination device according to the embodiment)
　is broken determination apparatus 1 and 2, executes the break determination process in collision deformation simulation of the vehicle, the fracture determination apparatus according to the embodiment, at the time of press-molding a steel plate in another simulation deformation simulation such may execute fracture judgment process. Further, in the example described, the case element size of the analysis model is uniform has been described as an example, fracture determination device according to embodiments may use the analytical model element size differs depending on the site. That is, element model fracture judgment apparatus used according to the embodiment may include a plurality of element size.
[0058]
　(Application Example of the fracture determination device according to the embodiment)
　FIG 6 is a diagram showing a mold manufacturing system which is an example of application of the fracture determination apparatus according to the embodiment.
[0059]
　Mold manufacturing system 100 includes a fracture judgment apparatus 1, the mold design apparatus 111, and a mold manufacturing apparatus 112. Mold design apparatus 111 is, for example, a device for designing a mold for manufacturing a car body, is an electric machine that is connected through the fracture judgment apparatus 1 and LAN 113. Mold design apparatus 111 uses the fracture determination by breaking determination apparatus 1 generates the mold data indicating the desired mold. In Figure 8, the mold design apparatus 111 is arranged as break determination device 1 and the separate device may be integrated with the fracture determination apparatus 1 in another embodiment.
[0060]
　Mold manufacturing device 112, electric discharge machine (not shown), has a mold manufacturing equipment such as milling and grinding machines, mold design apparatus via the communication network 114 is a wide area communication network by the switch (not shown) 111 It is connected to. Mold manufacturing apparatus 102, based on the mold data transmitted from the die design device 111, for producing a mold corresponding to the die data.
Example
[0061]
　7, the load at break determination device Tensile simulation test results of the comparative example - shows between gauge marks strain relationship. Figure 8 is a diagram showing the risk of fracture in a is broken determination apparatus tensile simulation test results 1 Inventive Example was determined to be broken, that is, erase risk of fracture exceeds 1 elements is, the test piece shows a state after being separated. 8 (a) is element size indicates when 2 mm. FIG. 8 (b) element size indicates when the 3 mm and FIG. 8 (c) element size is 5 [mm] indicate when. 9, the load in the simulation results of the tensile test by breaking determination apparatus 1 is an example of the present invention - it shows the relationship strain between reference points. 7 and 9, the horizontal axis represents the strain between reference points and the vertical axis represents the load [kN].
[0062]
　Fracture judgment apparatus according to the comparative example, the simulation was run in tensile tests with respect to 980MPa grade steel plate thickness is 1.6 mm. Also, fracture determination apparatus according to the comparative example, analyzes beforehand using FEM model of element size 2 mm and check the breaking strain, element size is 3 to remain with the breaking strain was confirmed mm. also models and element size is 5 [mm] model executing the break determination process is set to the same criteria.
[0063]
　In fracture judgment apparatus tensile simulation test results of the comparative example, for the model of the element size 2 was confirmed breaking strain in advance mm and of course showed experiments agree well, element size 3 [mm] and If the element size saw model of 5 [mm], different break time for each element size according to the element size increases, resulting in a timing that is determined to have broken is delayed. For this reason, when the element size is different, it became a result that can not be correctly predicted the experimental results.
[0064]
　On the other hand, in fracture determination apparatus tensile simulation test results 1, fractured at substantially the same timing regardless of the element size is determined. Further, a tensile test of a simulation result of the fracture determination apparatus 1 is also accurately determine the experimental results.

The scope of the claims
[Requested item 1]
　Shows the material properties and thickness of the steel, as well as the input information element indicating an element size in the analysis model used for deformation simulation of the steel according to the finite element method, the forming limit value in the reference element size is the element size as a reference a storage unit for storing the reference forming limit value information, the indicating reference molded limits,
　based on the reference forming limit value information, the reference forming limit in accordance with the material properties and the thickness is included in the input information a reference forming limit value generation unit for generating a value,
　using a tensile strength of the steel, for which to generate the target molding limits to predict the forming limit of the element size by changing the reference shaping limits and forming limit value generation unit,
　by executing the deformation simulation using the input information, and outputs the modification information including the strain of each element simulators And Deployment execution unit,
　and the principal strain determining section for determining respective principal strain of elements included in the deformation information,
　respective maximum main strain and minimum principal strains of the principal strain is determined elements, the target forming limit based on the target forming limit line defined by a value, each element in the analysis model, a break determining section determines whether or not to break
　fracture judgment apparatus characterized in that it comprises a.
[Requested item 2]
　The object forming limit value generation unit, and the element size to predict the forming limit value using a first coefficient obtained from a tensile strength of the steel, fracture determination apparatus according to claim 1.
[Requested item 3]
　The object forming limit value generator, said first coefficient, and a second coefficient including the maximum principal strain and the first coefficient in the reference element size, maximum principal strain in the element size using said element size predicting, fracture determination apparatus according to claim 2.
[Requested item 4]
　The second factor is a function of the maximum principal strain and the first coefficient in the reference element size, fracture determination device according to claim 3.
[Requested item 5]
　The second factor is proportional to the maximum principal strain in the reference element size to the logarithm of the value obtained by dividing the first coefficient, fracture determination apparatus according to claim 4.
[Requested item 6]
　The object forming limit value generator, said first coefficient and the exponent of said second coefficient, the maximum principal strain in the element size using the product of the operation result of exponentiation operation to base the element size predicting, fracture determination apparatus according to any one of claims 2-5.
[Requested item 7]
　The object forming limit value generation unit, and the element size to predict the forming limit value using a second coefficient obtained from a tensile strength of the steel, fracture determination apparatus according to claim 1.
[Requested item 8]
　The second factor is a function of the maximum principal strain and the first coefficient in the reference element size, fracture determination apparatus according to claim 7.
[Requested item 9]
　The second factor is proportional to the maximum principal strain in the reference element size to the logarithm of the value obtained by dividing the first coefficient, fracture determination apparatus according to claim 8.
[Requested item 10]
　The object forming limit value generation unit uses the element size and shaped limits prediction expression which is a function of the tensile strength of the steel material to produce the target forming limit value,
　the forming limit value prediction equation, [rho is a strain ratio, M is an element size indicating the size of the elements of the analysis model used in the simulation by FEM, epsilon 1 is the maximum principal strain in the element size M, epsilon 2 is the minimum principal strain in element size M On one occasion, the first coefficient k1 and the second coefficient k2
[number 1]

is represented by the first coefficient k1 is the tensile strength TS of the material of the steel sheet and, from the coefficient γ and [delta]
[Equation 2]

is represented by, the second coefficient k2, the maximum principal strain ε in the reference element size 1B and from the coefficient eta
[number 3]

represented by the fracture judgment apparatus according to claim 1.
[Requested item 11]
　The fracture determination unit, when the maximum of the determined elements principal strain and minimum principal strain exceeds the threshold given by the target forming limit line, it is determined that the element is broken, according to claim 1 to 10 any fracture determination apparatus according to an item.
[Requested item 12]
　Wherein the target forming limit stress generator for generating a target forming limit stress by changing the target forming limit value,
　converts respective maximum principal strain and minimum principal strain of the determined elements to the maximum principal stress and the minimum principal stress a strain stress conversion unit, further comprising a
　said fracture determination unit determines that when the maximum principal stress and the minimum principal stress of the converted elements is greater than the target forming limit stress element is broken, fracture determination apparatus according to any one of claims 1 to 10.
[Requested item 13]
　The deformation simulation is collision deformation simulation of the vehicle formed by the steel, fracture determination apparatus according to any one of claims 1 to 12.
[Requested item 14]
　Based on the reference forming limit value information indicating a forming limit value corresponding to the forming limit line in the reference element size indicating the element size as a reference, the element indicating an element size in the analysis model used for deformation simulation of steel by FEM generates the reference forming limit value according to the material properties and thickness of the steel contained in the input information,
　by using a tensile strength of the element size and the steel, the elements by changing the reference shaping limits generates a target molding limits to predict the forming limit in size,
　by running the deformation simulation using the input information, and outputs the modification information including the strain of each element,
　included in the deformation information determining the strain respective maximum main elements and minimum principal strains that,
　each of the maximum principal strain and minimum of the principal strain is determined elements Strain and the based on the object forming limit line which is defined by the object forming limit value, each element in the analysis model for determining whether to break
　fracture determination method, characterized in that it comprises.
[Requested item 15]
　Based on the reference forming limit value information indicating a forming limit value corresponding to the forming limit line in the reference element size indicating the element size as a reference, the element indicating an element size in the analysis model used for deformation simulation of steel by FEM generates the reference forming limit value according to the material properties and thickness of the steel contained in the input information,
　by using a tensile strength of the element size and the steel, the elements by changing the reference shaping limits generates a target molding limits to predict the forming limit in size,
　by running the deformation simulation using the input information, and outputs the modification information including the strain of each element,
　included in the deformation information determining the strain respective maximum main elements and minimum principal strains that,
　each of the maximum principal strain and minimum of the principal strain is determined elements Strain and the based on the object forming limit line which is defined by the object forming limit value to determine whether each element in the analysis model is broken,
　breaking, characterized in that to execute the process to the computer determination program.