Parameter acquisition method and parameter acquisition program

Abstract

To easily acquire a YU parameter by using test results of a tensile test and a bending test of a test piece without performing a tensile compression test for an elastoplastic material, the elastic test piece.SOLUTION: A simulation system 10 simulates by adding a processing history according to a bending test and an applied strain tensile test, to test piece data on a computer based on physical property value data and the test result data, and a YU parameter in a Yoshida-Uemori model, to generate analysis result data representing a deformation degree of the test piece data. The simulation system 10 calculates a difference between the test result data and the analysis result data, and repeatedly adjusts the YU parameter in the Yoshida-Uemori model so as to reduce the difference. The simulation system 10 acquires a final YU parameter by repeatedly adjusting the YU parameter until the difference becomes equal to or smaller than a threshold.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a parameter acquisition method and a parameter acquisition program. Background Art

[0002] Conventionally, techniques for predicting the springback amount of an elastoplastic material during press forming are known (e.g., Patent Documents 1 and 2). The techniques of Patent Documents 1 and 2 non-linearly formulate an approximation method for the stress-strain relationship during unloading when performing a tensile-compression test, as well as the stress-strain curve. In particular, Patent Document 2 improves the estimation accuracy of the stress-strain relationship by considering the term of back stress. Prior Art Literature Patent Literature

[0003] Patent Document 1 Japanese Patent No. 5866892 Patent Document 2 Japanese Patent No. 5582211 Summary of Invention Problems to be Solved by the Invention

[0004] Incidentally, in order to obtain the YU parameter calculated by the Yoshida-Uemori model disclosed in the above Patent Documents 1 and 2, it is necessary to perform a tensile-compression test on the elastoplastic material. However, when a tensile-compression test is performed on an elastoplastic material, buckling or the like often occurs in the elastoplastic material during the compression process, and the success rate is low.

[0005] For this reason, in the prior art, since it is necessary to perform a tensile-compression test on an elastoplastic material, there has been a problem that the YU parameter calculated by the Yoshida-Uemori model cannot be easily obtained.

[0006] This invention has been made in view of the above problems, and aims to easily obtain the YU parameter by utilizing the test results from tensile and bending tests of a test specimen, without performing tensile and compression tests on the elastoplastic material test specimen. [Means for solving the problem]

[0007] A first aspect of the present invention is a parameter acquisition method in which a computer performs the following processing: it receives physical property data of a test piece obtained by a simple tensile test on the test piece, and test result data representing the results of a bending test and a strained tensile test on the test piece; it performs a press forming simulation, which is a simulation that adds processing history corresponding to the bending test and the strained tensile test to the test piece data on a computer, based on the physical property data, the test result data and the YU parameter in the Yoshida-Uemori model, thereby generating analysis result data representing the degree of deformation of the test piece data; it calculates the difference between the test result data and the analysis result data; it repeatedly adjusts the YU parameter so that the difference becomes smaller; and it repeatedly adjusts the YU parameter until the difference falls below a threshold, thereby obtaining the final YU parameter.

[0008] A second aspect of the present invention is a parameter acquisition program for causing a computer to perform a process that receives physical property data of a test specimen obtained by a simple tensile test on the test specimen, and test result data representing the results of a bending test and a strained tensile test on the test specimen, and performs a press forming simulation, which is a simulation that adds processing history corresponding to the bending test and the strained tensile test to the test specimen data on a computer based on the physical property data, the test result data and the YU parameter in the Yoshida-Uemori model, thereby generating analysis result data representing the degree of deformation of the test specimen data, calculating the difference between the test result data and the analysis result data, repeatedly adjusting the YU parameter so that the difference becomes smaller, and repeating the adjustment of the YU parameter until the difference is below a threshold, thereby obtaining the final YU parameter. [Effects of the Invention]

[0009] According to the present invention, the YU parameter can be easily obtained by utilizing the test results from tensile and bending tests of a test specimen, without performing tensile and compression tests on the elastoplastic material test specimen. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram illustrating tension and compression in a tensile-compression experiment. [Figure 2] This block diagram shows an example of the configuration of a simulation system according to the embodiment. [Figure 3] This is a diagram illustrating the bending test in this embodiment. [Figure 4] This figure shows an example of the computer configuration of the parameter acquisition device according to the embodiment. [Figure 5] This figure shows an example of a processing routine executed by a parameter acquisition device. [Modes for carrying out the invention]

[0011] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In the following embodiments, the components are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and they do not limit the present invention.

[0012] Traditionally, in order to obtain the YU parameters calculated in the Yoshida-Uemori model, it was necessary to perform tensile and compressive experiments on the specimens to reproduce the Bausinger effect.

[0013] By performing tensile and compressive experiments on an elastoplastic material specimen, a stress-strain diagram of the specimen can be obtained. In the stress-strain diagram, after the specimen reaches its early re-yield point, transitional softening due to the Bausinger effect and permanent softening of the specimen appear. The relationship between tension and compression in the tensile and compressive experiments is as shown in Figure 1 of the stress-strain diagram.

[0014] Compression experiments on test specimens are theoretically possible. However, in reality, the specimens buckle during compression experiments, resulting in a low success rate, making them unsuitable for actual manufacturing environments.

[0015] Therefore, the parameter acquisition method of this embodiment acquires YU parameters by utilizing a computer simulation that reproduces the stress-strain relationship of the elastoplastic material, which is the test specimen. The target YU parameters are, for example, the kinematic hardening convergence rate C1 of the yield surface representing the transition softening region, the kinematic hardening convergence rate C2 of the yield surface representing the transition softening region, and the mean Young's modulus asymptotic value E. av And so on.

[0016] Specifically, in the parameter acquisition method of the present embodiment, test result data is obtained by performing a bending test and a pre-strain tensile test on an elastic-plastic material that is a test piece. Next, in the parameter acquisition method of the present embodiment, press forming simulation, which is a simulation that adds processing history corresponding to the bending test and the pre-strain tensile test to test piece data on a computer, is executed. Then, in the parameter acquisition method of the present embodiment, the YU parameters are sequentially adjusted so that the difference between the test result data obtained from the actual test and the analysis result data obtained from the press forming simulation is reduced. Then, the YU parameter obtained when the difference becomes equal to or less than a predetermined threshold is acquired as the final YU parameter. This makes it possible to easily acquire the YU parameters by utilizing the test results obtained from the tensile test and bending test performed on the elastic-plastic material, without performing a tensile-compression test on the elastic-plastic material. A detailed description is given below.

[0017] <Configuration of Simulation System> Figure 2 is a block diagram showing an example of the configuration of the simulation system 10 according to the embodiment. Functionally, as shown in Figure 3, the simulation system 10 can be expressed as a configuration including an operation unit 12, a parameter acquisition device 14, and a display unit 16.

[0018] The operation unit 12 receives operation information input from a user. The operation unit 12 is, for example, a keyboard, a mouse, or the like. Specifically, the user inputs various types of information for executing simulation via the operation unit 12.

[0019] Information output from the parameter acquisition device 14 is displayed on the display unit 16. The display unit 16 is implemented by, for example, a display or the like.

[0020] The parameter acquisition device 14 is configured to include a CPU (Central Processing Unit), a ROM (Read Only Memory) storing programs and the like for implementing each processing routine, a RAM (Random Access Memory) temporarily storing data, a memory serving as a storage means, a network interface, and the like. Functionally, the parameter acquisition device 14 includes a data storage unit 20, a result storage unit 22, a reception unit 24, a simulation unit 26, and a calculation unit 28, as shown in FIG. 1.

[0021] The data storage unit 20 stores various types of data for executing simulations described later.

[0022] The result storage unit 22 stores YU parameters acquired by the parameter acquisition method of the present embodiment.

[0023] The reception unit 24 receives information input by a user.

[0024] Specifically, the user performs a simple tensile test on a test piece of an elastoplastic material using equipment for a simple tensile test, and inputs physical property value data of the test piece, which is the test result, to the parameter acquisition device 14. Further, after the user performs a pre-strain tensile test on the test piece, the user performs a bending test on the test piece using a bending test jig, and inputs test result data, which is the test result, to the parameter acquisition device 14. Note that the compression process in a tensile-compression test is reproduced to a certain extent by the bending test of the present embodiment.

[0025] The reception unit 24 receives the physical property value data and the test result data representing results of the bending test and the pre-strain tensile test performed on the test piece. The physical property value data are general physical properties of the test piece, including the elastic modulus, Poisson's ratio, yield stress, and the like of the test piece. Further, the test result data includes the springback amount of the test piece, the bending angle of the test piece after springback, and the like.

[0026] In this embodiment, the bending test is performed such that the end point of the bend of the test specimen lies tangent to the circle. Figure 3 shows a diagram illustrating the bending test in this embodiment. As shown in V1 of Figure 3, when a bending test is performed on a test specimen T with plate thickness t, the bending angle is θ and the radius of curvature is ρ. On the other hand, in the scene V2 following V1, springback occurs in the test specimen T, resulting in a bending angle θ' and a radius of curvature ρ' after springback.

[0027] In this embodiment, the bending test is performed such that the bending endpoints P1 and P2 of the test specimen T are located tangent to circle C, as shown on the right side of Figure 3. Such a bending test has the advantage of easily reflecting the analysis results obtained by the simulation described later, as it is possible to reproduce the following empirical formula. Furthermore, the compression process in the tensile-compression test is reproduced to some extent by the bending test in this embodiment.

[0028]

number

[0029] In the above equation, M represents the bending moment, I represents the second moment of area, E represents Young's modulus, and Y represents the yield stress.

[0030] The simulation unit 26 generates analysis result data representing the degree of deformation of the test specimen data by adding processing history corresponding to the bending test and strain tensile test to the test specimen data on the computer, based on the physical property data and test result data received by the reception unit 24 and the YU parameters in the set Yoshida-Uemori model, and then executing a press forming simulation. The press forming simulation can be performed using known methods. As a result, the analysis result data obtained includes the amount of springback when a virtual bending test and strain test are performed on the test specimen data on the computer, the bending angle after springback, and data related to the shape of the test specimen.

[0031] Furthermore, when acquiring analysis result data, the press forming simulation of the processing history corresponding to the bending test and strain tensile test is performed so that the bending endpoint of the test piece data on the computer lies tangent to the circle.

[0032] The calculation unit 28 calculates the difference between the test result data received by the reception unit 24 and the analysis result data generated by the simulation unit 26. The calculation unit 28 then determines whether the difference is less than or equal to a predetermined threshold. If the difference is less than or equal to the predetermined threshold, the YU parameters used at that time are stored in the result storage unit 22 as the final YU parameters. On the other hand, if the difference is greater than the predetermined threshold, the YU parameters are changed, and the press forming simulation by the simulation unit 26 is repeated. In this way, the YU parameters in the Yoshida-Uemori model are repeatedly adjusted so that the difference between the test result data and the analysis result data becomes smaller, and the final YU parameters are obtained by repeatedly adjusting the YU parameters until the difference is less than or equal to the threshold.

[0033] The parameter acquisition device 14 can be implemented, for example, by a computer 50 as shown in Figure 4. The computer 50 implementing the parameter acquisition device 14 includes a CPU 51, a memory 52 as a temporary storage area, and a non-volatile storage unit 53. The computer 50 also includes an input / output interface (I / F) 54 to which input / output devices, etc. (not shown) are connected, and a read / write (R / W) unit 55 that controls the reading and writing of data to the recording medium 59. The computer also includes a network I / F 56 that connects to a network such as the Internet. The CPU 51, memory 52, storage unit 53, input / output I / F 54, R / W unit 55, and network I / F 56 are connected to each other via a bus 57.

[0034] The storage unit 53 can be implemented using a Hard Disk Drive (HDD), Solid State Drive (SSD), flash memory, etc. The storage unit 53, as a storage medium, stores programs that enable the computer to function. The CPU 51 reads the programs from the storage unit 53, loads them into memory 52, and sequentially executes the processes contained within the programs.

[0035] <How the simulation system works>

[0036] Next, we will explain the operation of the simulation system 10.

[0037] The user performs a simple tensile test on a specimen of elastoplastic material using equipment for simple tensile testing, and inputs the resulting physical property data into the parameter acquisition device 14. The user also performs a strained tensile test on the specimen, followed by a bending test using a bending jig, and inputs the resulting test data into the parameter acquisition device 14. Upon receiving a predetermined instruction signal, the parameter acquisition device 14 executes the processing routine shown in Figure 5.

[0038] In step S100, the reception unit 24 receives physical property data and test result data.

[0039] In step S102, the simulation unit 26 sets the initial values ​​of the YU parameters.

[0040] In step S104, the simulation unit 26 generates analysis result data representing the degree of deformation of the test piece data by performing a known press forming simulation on the computer to add the processing history corresponding to the bending test and strain tensile test, based on the physical property data and test result data received in step S100 and the initial value of the YU parameter set in step S102.

[0041] In step S106, the calculation unit 28 calculates the difference between the test result data received in step S100 and the analysis result data generated in step S104. Specifically, the calculation unit 28 calculates the difference between the springback amount of the actual test specimen included in the test result data and the springback amount included in the test specimen data included in the analysis result data. The calculation unit 28 also calculates the difference between the bending angle after springback of the actual test specimen included in the test result data and the bending angle after springback of the test specimen data included in the analysis result data. Furthermore, the calculation unit 28 calculates the difference between other values ​​representing the shape of the actual test specimen included in the test result data and other values ​​representing the shape of the test specimen data included in the analysis result data.

[0042] In step S108, the calculation unit 28 determines whether the difference calculated in step S106 is less than or equal to a predetermined threshold. If the difference calculated in step S106 is less than or equal to the predetermined threshold, the process proceeds to step S110. On the other hand, if the difference calculated in step S106 is greater than the predetermined threshold, the YU parameter is adjusted in step S112.

[0043] Various methods can be considered for determining whether the difference is below a threshold. For example, one method could determine whether the difference in springback amount, the difference in bending angle, and the difference in other values ​​representing the shape of the test specimen are each below a predetermined threshold. Alternatively, one method could determine whether at least one of the differences in springback amount, bending angle, and other values ​​representing the shape of the test specimen is each below a predetermined threshold.

[0044] In step S110, the calculation unit 28 stores the YU parameters adjusted in the previous step S112 as the final YU parameters in the result storage unit 22.

[0045] The final YU parameters stored in the result storage unit 22 are used by the user.

[0046] As described above, the simulation system 10 of the embodiment receives material property data representing the results of an actual simple tensile test on a test specimen, and test result data representing the results of a bending test and a strained tensile test on the test specimen. The simulation system 10 then generates analysis result data representing the degree of deformation of the test specimen data by adding the processing history corresponding to the bending test and strained tensile test to the test specimen data on the computer and performing a simulation based on the material property data, the test result data, and the YU parameters in the Yoshida-Uemori model. The simulation system 10 calculates the difference between the test result data and the analysis result data, and repeatedly adjusts the YU parameters in the Yoshida-Uemori model so that the difference becomes smaller. The simulation system 10 obtains the final YU parameters by repeatedly adjusting the YU parameters until the difference falls below a threshold. In this way, the YU parameters calculated in the Yoshida-Uemori model can be easily obtained by using the test results from tensile tests and bending tests on an elastoplastic material, without performing tensile and compression tests on the elastoplastic material.

[0047] Furthermore, since the time required to acquire YU parameters can be significantly reduced, design time can be shortened, as can the amount of work required for mold modification, and product delivery times can be shortened.

[0048] It should be noted that the present invention is not limited to the embodiments described above, and various modifications and applications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0049] 10 Simulation Systems 12 Control section 14 Parameter acquisition device 16 Display section 20 Data storage unit 22 Result storage 24 Reception Department 26 Simulation Department 28 Calculation section 50 Computers

Claims

1. The system receives physical property data of the specimen obtained by a simple tensile test on the specimen, and test result data representing the results of a bending test and a strain-induced tensile test on the specimen. Based on the aforementioned physical property data and test result data, and the YU parameter in the Yoshida-Uemori model, a press forming simulation is performed, which is a simulation that adds the processing history corresponding to the bending test and the strain-applied tensile test to the test specimen data on a computer, thereby generating analysis result data that represents the degree of deformation of the test specimen data. The difference between the aforementioned test result data and the aforementioned analysis result data is calculated, The YU parameter is repeatedly adjusted so that the aforementioned difference becomes smaller. The final YU parameter is obtained by repeatedly adjusting the YU parameter until the difference falls below a threshold. A method for obtaining parameters that a computer uses to execute a process, The bending test used to obtain the aforementioned test result data is performed such that the end point of the bending of the test piece lies on the tangent to the circle. The processing history corresponding to the bending test when acquiring the analysis result data is carried out such that the bending endpoint when the test piece data is bent lies on the tangent line of the circle. How to obtain parameters.

2. The difference between the test result data and the analysis result data is at least one of the difference in springback amount and the difference in bending angle after springback. The parameter acquisition method according to claim 1.

3. The system receives physical property data of the specimen obtained by a simple tensile test on the specimen, and test result data representing the results of a bending test and a strain-induced tensile test on the specimen. Based on the aforementioned physical property data and test result data, and the YU parameter in the Yoshida-Uemori model, a press forming simulation is performed, which is a simulation that adds the processing history corresponding to the bending test and the strain-applied tensile test to the test specimen data on a computer, thereby generating analysis result data that represents the degree of deformation of the test specimen data. The difference between the aforementioned test result data and the aforementioned analysis result data is calculated, The YU parameter is repeatedly adjusted so that the aforementioned difference becomes smaller. The final YU parameter is obtained by repeatedly adjusting the YU parameter until the difference falls below a threshold. A program for obtaining parameters to cause a computer to execute a process, The bending test used to obtain the aforementioned test result data is performed such that the end point of the bending of the test piece lies on the tangent to the circle. The processing history corresponding to the bending test when acquiring the analysis result data is carried out such that the bending endpoint when the test piece data is bent lies on the tangent line of the circle. Parameter acquisition program.

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