Stress influence analysis device, stress influence analysis method, and program

Abstract

The present invention provides an apparatus and method capable of analyzing the influence of stress, which is a factor in the occurrence of springback, in a short time and with high accuracy. [Solution] A stress influence analysis device 10 comprises an acquisition unit 11 that acquires information on the shape, characteristics, and stress of a press-formed part after press forming and before springback (SB) occurs, information on the shape and characteristics of a press-formed part after SB occurs, and information on the stress of an analysis model after a forced displacement is applied to an analysis model generated based on the information on the shape and characteristics before or after SB occurs; and a calculation unit 12 that calculates the degree of influence of the stress in the press-formed part before SB occurs on SB based on the information on the stress of the press-formed part before SB occurs and the information on the stress of the analysis model after a forced displacement is applied, wherein the forced displacement is set based on the information on the shape of the press-formed part before and after SB occurs.

Description

[Technical Field]

[0001] This invention relates to an analytical apparatus, analytical method, and program for analyzing the influence of stress on the occurrence of springback. [Background technology]

[0002] Springback occurs when stress generated during press forming is released upon demolding. This stress varies depending on the part shape and forming method, and also differs from location to location within the part, resulting in a very complex distribution. Therefore, it is generally difficult to distinguish between stresses with a high and low impact on springback.

[0003] For example, Patent Document 1 discloses a springback cause analysis technique that enables more accurate analysis of the locations causing springback in press-formed products through numerical analysis, thereby reducing the time and cost spent on considering the molding method for molded members. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-172677 [Overview of the project] [Problems that the invention aims to solve]

[0005] The technology described in Patent Document 1 makes it possible to predict with high accuracy the location that causes springback. However, this technology has the problem of increasing analysis time because it virtually divides the pressed part into many small sections, performs a springback analysis by changing the stress state in each divided region, and calculates the degree of influence.

[0006] The present invention aims to solve the above problems and provides an apparatus and method capable of analyzing the degree of influence of stress, which is a factor causing springback, in a short time with high accuracy.

Means for Solving the Problems

[0007] As described above, when performing innumerable springback analyses, a great deal of analysis time is required. Therefore, the present inventors focused only on the change in the shape of the formed part before and after springback. Then, by comparing the stress distribution generated when deforming from the shape before springback to the shape after springback with the stress distribution generated by pressing, it was conceived that the degree of influence of the stress, which is a factor causing springback, could be analyzed in a short time with high accuracy.

[0008] The present invention is made based on the above findings, and its gist is the following stress influence degree analysis apparatus, stress influence degree analysis method, and program.

[0009] (1) An apparatus for analyzing the degree of influence of stress, which is a factor causing springback, in a press-formed part after press forming, comprising: information on the shape, characteristics, and stress in the press-formed part after press forming and before springback occurs; information on the shape and characteristics in the press-formed part after press forming and after springback occurs; an acquisition unit that acquires information on the stress in the analysis model after applying a forced displacement to the analysis model generated based on the information on the shape and characteristics in the press-formed part before or after springback occurs; and a calculation unit that calculates the degree of influence of the stress in the press-formed part before springback on springback based on the information on the stress in the press-formed part before springback and the information on the stress in the analysis model after applying the forced displacement. The forced displacement is set based on information regarding the shape of the press-formed part before the springback occurs and information regarding the shape of the press-formed part after the springback occurs. Stress influence analysis device.

[0010] (2) The calculation unit calculates information regarding the stress in the analysis model after the forced displacement has been applied. The stress influence analysis apparatus described in (1) above.

[0011] (3) The calculation unit calculates information regarding the shape of the press-formed part after the springback occurs, using an analysis model generated based on information regarding the shape, characteristics, and stress of the press-formed part before the springback occurs. A stress influence analyzer as described in (1) or (2) above.

[0012] (4) A method for analyzing the influence of stress that causes springback in press-formed parts after press forming, Information regarding the shape, characteristics, and stress of a press-formed part after press forming and before springback occurs, Information regarding the shape and characteristics of press-formed parts after springback has occurred following press forming, The steps include obtaining information on the stress in the analysis model after applying a forced displacement to the analysis model, which is generated based on information on the shape and characteristics of the press-formed part before or after the occurrence of springback, The method includes the step of calculating the degree of influence of the stress in the press-formed part before springback occurs on springback, based on information regarding the stress in the press-formed part before springback occurs and information regarding the stress in the analysis model after the forced displacement is applied. The forced displacement is set based on information regarding the shape of the press-formed part before the springback occurs and information regarding the shape of the press-formed part after the springback occurs. Methods for analyzing the impact of stress.

[0013] (5) The step of calculating information regarding the stress in the analysis model after the forced displacement has been applied, The stress influence analysis method described in (4) above.

[0014] (6) The method further comprises the step of calculating information regarding the shape of the press-formed part after springback occurs, using an analysis model generated based on information regarding the shape, characteristics, and stress of the press-formed part before springback occurs. The stress influence analysis method described in (4) or (5) above.

[0015] (7) A computer program for analyzing the degree of influence of stress that causes springback in press-formed parts after press forming, Information regarding the shape, characteristics, and stress of a press-formed part after press forming and before springback occurs, Information regarding the shape and characteristics of press-formed parts after springback has occurred following press forming, The steps include obtaining information on the stress in the analysis model after applying a forced displacement to the analysis model, which is generated based on information on the shape and characteristics of the press-formed part before or after the occurrence of springback, The procedure involves performing the step of calculating the degree of influence of the stress in the press-formed part before springback occurs on the springback, based on the information regarding the stress in the press-formed part before springback occurs and the information regarding the stress in the analysis model after the forced displacement is applied. The forced displacement is set based on information regarding the shape of the press-formed part before the springback occurs and information regarding the shape of the press-formed part after the springback occurs. program.

[0016] (8) The step of calculating information regarding the stress in the analysis model after the forced displacement has been applied, The program described in (7) above.

[0017] (9) The method further comprises the step of calculating information regarding the shape of the press-formed part after springback occurs, using an analysis model generated based on information regarding the shape, characteristics, and stress of the press-formed part before springback occurs. The program described in (7) or (8) above. [Effects of the Invention]

[0018] According to the present invention, it becomes possible to analyze the degree of influence of stress, which is a factor in the occurrence of springback, in a short time and with high accuracy. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 shows a schematic configuration of a stress influence analysis device according to one embodiment of the present invention. [Figure 2] Figure 2 shows an example of a press-formed part whose stress influence is analyzed by the stress influence analysis apparatus according to this embodiment. [Figure 3] Figure 3 shows a schematic configuration of a stress influence analysis apparatus according to another embodiment of the present invention. [Figure 4] Figure 4 is a flowchart showing a stress influence analysis method according to one embodiment of the present invention. [Figure 5] Figure 5 shows an example of a stress influence distribution map calculated using a stress influence analysis device according to one embodiment of the present invention. [Figure 6]Figure 6 shows an example of a stress influence distribution map calculated using conventional technology. [Figure 7] Figure 7 is a block diagram showing an example of a computer that implements the stress influence analysis device in this embodiment. [Modes for carrying out the invention]

[0020] A stress influence analysis apparatus and stress influence analysis method according to one embodiment of the present invention will be described with reference to Figures 1 to 7.

[0021] Figure 1 is a diagram showing a schematic configuration of a stress influence analysis device according to one embodiment of the present invention. Figure 2 is a diagram showing an example of a press-formed part that is the subject of stress influence analysis by the stress influence analysis device according to this embodiment, where (a) is a perspective view of the press-formed part after press forming and before springback occurs, and (b) is a perspective view of the press-formed part after press forming and after springback occurs. Note that in Figure 2, the displacement caused by springback is exaggerated. The press-formed part shown in Figure 2 has a hat-shaped cross-section.

[0022] The following description will focus on the analysis of press-formed parts shown in Figure 2. However, the shape of the press-formed parts to be analyzed by the stress influence analyzer according to this embodiment is not limited to the shape shown in Figure 2. The stress influence analyzer according to this embodiment can handle press-formed parts of various shapes.

[0023] The stress influence analysis device according to this embodiment is a device for analyzing the influence of stress that causes springback in press-formed parts after press forming. As shown in Figure 1, the stress influence analysis device 10 comprises an acquisition unit 11 and a calculation unit 12.

[0024] The acquisition unit 11 acquires information on the shape, properties, and stress of a press-formed part after press forming and before springback occurs. This information is used to perform numerical analyses such as finite element analysis (FEA) and isogeometric analysis (IGA). Specifically, the shape information includes nodal data, element data, etc. The property information includes material data such as strength and Young's modulus.

[0025] Information regarding stress includes stress for each element, for example, normal stress (σ xx ,σ yy ,σ zz ) and shear stress (σ xy ,σ yz ,σ xz The stress includes a total of six components. The stress information may be obtained by performing numerical analysis such as elastoplastic finite element analysis or one-step finite element analysis (FEA) or IGA using a known press forming analysis device based on press forming conditions set by the user, or it may be measured by X-ray analysis or the like. Note that the above numerical analysis may be performed by an external analysis device or by the calculation unit 12 described later.

[0026] Furthermore, the acquisition unit 11 acquires information regarding the shape and characteristics of the press-formed part after press forming and after springback has occurred. The information regarding characteristics is determined by the material, and is therefore the same as the information regarding the characteristics of the press-formed part before springback has occurred, as described above.

[0027] Information on the shape of the press-formed part after springback may be, for example, data actually measured by manufacturing the press-formed part and performing displacement measurement on the obtained press-formed part, or may be obtained by performing numerical analysis such as FEA or IGA based on information on the shape, characteristics, and stress in the press-formed part before springback described above. The analysis model used at this time may consider all deformation modes such as torsion, warp, and opening of the hat shape, or may consider only a part of them. Also, a plurality of analysis models considering different deformation modes may be used. Note that the above numerical analysis may be performed by an external analysis device or may be performed by the calculation unit 12 described later.

[0028] In the example shown in FIG. 2, nodes a and b are set as fixed points, and due to springback, in the xyz coordinate system, node 1 moves from (x S0,1 , y S0,1 , z S0,1 ) to (x R0,1 , y R0,1 , z R0,1 ), and node i moves from (x S0,i , y S0,i , z S0,i ) to (x R0,i , y R0,i , z R0,i ). However, in this specification, i = 1 to m (m: the number of nodes of the analysis model).

[0029] Furthermore, the acquisition unit 11 acquires information on the stress in the analysis model after applying a forced displacement to the analysis model generated based on information on the shape and characteristics in the press-formed part before or after springback. Note that the above analysis model does not have information on the stress in the press-formed part before springback. Also, the information on the stress in the analysis model includes the stress for each element of the analysis model. For example, normal stress (σ xx , σ yy , σ zz ) and shear stress (σxy ,σ yz ,σ xz This includes a total of six stress components.

[0030] Here, the forced displacement is set based on information regarding the shape of the press-formed part before springback occurs and information regarding the shape of the press-formed part after springback occurs. The calculation of stress information in the analysis model after applying the forced displacement may be performed by an external analysis device or by the calculation unit 12 described later.

[0031] First, we will explain the case where forced displacement is applied to an analysis model (hereinafter also referred to as the "first analysis model") that is generated based on information regarding the shape and characteristics of the press-formed part before springback occurs.

[0032] Due to springback, at node i, (x S0,i ,y S0,i ,z S0,i ) from (x R0,i ,y R0,i ,z R0,i If the displacement is to ), the deformation vector V1 at node i i is (x R0,i -x S0,i ,y R0,i -y S0,i ,z R0,i -z S0,i ) is expressed as. The acquisition unit 11 obtains the deformation vector V1 for the first analysis model. i Information regarding stress in the first analysis model is obtained after applying a forced displacement of one or more components at any one or more nodes.

[0033] In the example above, the forced displacement is set based on a single analysis model, but as mentioned above, the forced displacement may also be set based on multiple analysis models that consider different deformation modes.

[0034] The first analysis model is generated based on information regarding the shape and characteristics of the press-formed part before springback occurs. However, a forced displacement may be applied to the analysis model generated based on information regarding the shape and characteristics of the press-formed part after springback occurs (hereinafter also referred to as the "second analysis model"). In this case, the forced displacement is V2 i = -1 × V1 i The deformed vector V2 is defined as i Use one or more components from any one or more nodes. Note that the deformation vector V2 at node i i is (x S0,i -x R0,i ,y S0,i -y R0,i ,z S0,i -z R0,i ) is expressed as.

[0035] The calculation unit 12 calculates the degree of influence of the stress in the press-formed part before springback occurs on springback (hereinafter also referred to as "stress influence") based on the information on the stress in the press-formed part before springback occurs, which was acquired by the acquisition unit 11, and the information on the stress in the analysis model after the forced displacement is applied.

[0036] In the following description, information regarding the stress in the press-formed part before springback occurs, and information regarding the stress in the first and second analysis models after forced displacement is applied, will be expressed as determinants of equations (i) to (iii) below, using a total of six stress components: normal stress and shear stress. However, in this specification, j = 1 to n (n: number of elements in the analysis model).

[0037]

number

[0038]

number

[0039]

number

[0040] There are no particular restrictions on the method for calculating the stress influence, however, when using the first analysis model, for example, I1 expressed by equation (iv) or (v) below can be used. j This may be used as the stress influence in element j. Furthermore, when using the second analysis model, for example, I2, expressed by equation (vi) or (vii) below, can be used. j This may also be considered as the stress influence in element j.

[0041]

number

[0042]

number

[0043]

number

[0044]

number

[0045] When equation (iv) or (vi) above is used as the stress influence, the stress influence is analyzed as high when both the stress in the press-formed part before springback occurs and the stress in the first or second analysis model after forced displacement is applied are high values. On the other hand, when equation (v) or (vii) above is used as the stress influence, the stress influence is analyzed as high when at least one of the stresses in the press-formed part before springback occurs and the stress in the first or second analysis model after forced displacement is applied is high value. Considering these factors, the method for calculating the stress influence should be set according to the purpose.

[0046] Figure 3 shows a schematic configuration of a stress influence analysis device according to another embodiment of the present invention. As shown in Figure 3, the stress influence analysis device 10 may further include an output unit 13. For example, the output unit 13 outputs the stress influence values ​​obtained by the calculation unit 12, along with element data, as a table to an external display device 20. The output unit 13 may also create a distribution map of the stress influence values ​​obtained by the calculation unit 12 as a two-dimensional or three-dimensional image and output it to the external display device 20. When creating the distribution map of stress influence values, for example, the stress influence values ​​can be shown by color coding or by contour lines.

[0047] Next, a stress influence analysis method according to one embodiment of the present invention will be explained using Figure 4. Figure 4 is a flowchart showing a stress influence analysis method according to one embodiment of the present invention.

[0048] As shown in Figure 4, the acquisition unit 11 first acquires nodal data, element data, and material data of the press-formed part after press forming and before springback occurs (step A1). Next, the calculation unit 12 performs elastoplastic finite element analysis based on the press forming conditions set by the user, as well as the nodal data, element data, and material data acquired by the acquisition unit 11, and calculates the six-component stress for each element of the press-formed part after press forming and before springback occurs (step A2). The acquisition unit 11 then calculates the six-component stress σ shown in equation (i) above, which has been calculated by the calculation unit 12. S0,j Obtain (Step A3).

[0049] Next, the calculation unit 12 performs a springback analysis based on the nodal data, element data, material data, and six-component stress for each element of the press-formed part before springback occurs, which were acquired by the acquisition unit 11, and calculates the nodal data and element data of the press-formed part after springback occurs (step A4). The acquisition unit 11 then acquires the nodal data and element data of the press-formed part after springback occurs, which were calculated by the calculation unit 12 (step A5).

[0050] Next, the calculation unit 12 calculates the six-component stress for each element in the analysis model after applying a forced displacement to the analysis model generated based on the nodal data, element data, and material data of the press-formed part before springback occurred, which was acquired by the acquisition unit 11 (step A6). The acquisition unit 11 then calculates the six-component stress σ shown in equation (ii) above, which was calculated by the calculation unit 12. R1,j Obtain (Step A7). The forced displacement used in this process is the deformation vector V1 for each node, calculated based on the nodal data and element data of the press-formed part before and after springback. i Of these, a predetermined component at a predetermined node selected in advance by the user is used.

[0051] Then, the calculation unit 12 calculates the stress σ acquired by the acquisition unit 11. S0,j and stress σ R1,j Based on this, the stress influence is calculated by multiplying each component together as shown in equation (iv) above (Step A8). Then, the output unit 13 creates a distribution map of the stress influence obtained by the calculation unit 12 and outputs it to the display device 20 (Step A9).

[0052] Figure 5 shows an example of a stress influence distribution map calculated using a stress influence analysis device according to one embodiment of the present invention. In the figure, darker colors indicate a larger stress influence value. Figure 6 shows an example of a stress influence distribution map calculated using the prior art (the art described in Patent Document 1 above). In the example shown in Figure 6, the press-formed part is divided into 5969 regions, and analysis is performed for each divided region.

[0053] As can be seen by comparing Figures 5 and 6, by employing the stress influence analysis device according to this embodiment, it is possible to obtain analysis results similar to those of the conventional technology in a short time. Specifically, in the examples shown in Figures 5 and 6, while the conventional technology required 5,969 analyses, employing the stress influence analysis device according to this embodiment made it possible to obtain similar results with only 1 to several tens of analyses.

[0054] The program according to one embodiment of the present invention is any program that causes a computer to execute steps A1 to A8 shown in Figure 4. By installing and executing this program on a computer, the stress influence analysis device 10 in this embodiment can be realized. In this case, the computer's processor functions as an acquisition unit 11, a calculation unit 12, and an output unit 13, and performs the processing.

[0055] Furthermore, the program in this embodiment may be executed by a computer system constructed by multiple computers. In this case, for example, each computer may function as either the acquisition unit 11, the calculation unit 12, or the output unit 13.

[0056] Here, a computer that realizes the stress influence analysis device 10 by executing the program in this embodiment will be described with reference to Figure 7. Figure 7 is a block diagram showing an example of a computer that realizes the stress influence analysis device in this embodiment.

[0057] As shown in Figure 7, the computer 100 includes a CPU (Central Processing Unit) 111, main memory 112, storage device 113, input interface 114, display controller 115, data reader / writer 116, and communication interface 117. These components are connected to each other via a bus 121, enabling data communication. In addition to the CPU 111, or in place of the CPU 111, the computer 100 may also include a GPU (Graphics Processing Unit) or an FPGA (Field-Programmable Gate Array).

[0058] The CPU 111 loads the program (code) in this embodiment, stored in the storage device 113, into the main memory 112 and performs various calculations by executing them in a predetermined order. The main memory 112 is typically a volatile storage device such as DRAM (Dynamic Random Access Memory). The program in this embodiment is provided stored in a computer-readable recording medium 120. The program in this embodiment may also be distributed over the internet connected via the communication interface 117.

[0059] Furthermore, specific examples of the storage device 113 include hard disk drives and semiconductor storage devices such as flash memory. The input interface 114 mediates data transmission between the CPU 111 and input devices 118 such as a keyboard and mouse. The display controller 115 is connected to the display device 119 and controls the display on the display device 119.

[0060] The data reader / writer 116 mediates data transmission between the CPU 111 and the recording medium 120, reads programs from the recording medium 120, and writes processing results from the computer 100 to the recording medium 120. The communication interface 117 mediates data transmission between the CPU 111 and other computers.

[0061] Specific examples of the recording medium 120 include general-purpose semiconductor memory devices such as CF (Compact Flash®) and SD (Secure Digital), magnetic recording media such as Flexible Disks, or optical recording media such as CD-ROMs (Compact Disk Read Only Memory).

[0062] Furthermore, the stress influence analysis device 10 in this embodiment can be implemented not by a computer with a program installed, but by using hardware corresponding to each part. Also, the stress influence analysis device 10 may be partially implemented by a program and the remaining parts by hardware. Moreover, the stress influence analysis device 10 may be configured using a cloud server. [Industrial applicability]

[0063] According to the present invention, it becomes possible to analyze the degree of influence of stress, which is a factor in the occurrence of springback, in a short time and with high accuracy. [Explanation of symbols]

[0064] 10. Stress Influence Analysis Device 11. Acquisition Department 12. Calculation Section 13. Output Section 20.Display device 100. Computers

Claims

1. A device for analyzing the degree of influence of stress that causes springback in press-formed parts after press forming, Information regarding the shape, characteristics, and stress of a press-formed part after press forming and before springback occurs, Information regarding the shape and characteristics of press-formed parts after springback has occurred following press forming, An acquisition unit that acquires information on the stress in the analysis model after applying a forced displacement to the analysis model, which is generated based on information on the shape and characteristics of the press-formed part before or after the occurrence of springback. The system includes a calculation unit that calculates the degree of influence of the stress in the press-formed part before springback occurs on springback, based on information regarding the stress in the press-formed part before springback occurs and information regarding the stress in the analysis model after the forced displacement is applied. The forced displacement is set based on information regarding the shape of the press-formed part before the springback occurs and information regarding the shape of the press-formed part after the springback occurs. Stress influence analysis device.

2. The calculation unit calculates information regarding the stress in the analysis model after the forced displacement has been applied. The stress influence analysis apparatus according to claim 1.

3. The calculation unit calculates information regarding the shape of the press-formed part after springback occurs, using an analysis model generated based on information regarding the shape, characteristics, and stress of the press-formed part before springback occurs. A stress influence analysis apparatus according to claim 1 or claim 2.

4. A method for analyzing the influence of stress on springback occurring in press-formed parts after press forming, Information regarding the shape, characteristics, and stress of a press-formed part after press forming and before springback occurs, Information regarding the shape and characteristics of press-formed parts after springback has occurred following press forming, The steps include obtaining information on the stress in the analysis model after applying a forced displacement to the analysis model, which is generated based on information on the shape and characteristics of the press-formed part before or after the occurrence of springback, The method includes the step of calculating the degree of influence of the stress in the press-formed part before springback occurs on springback, based on information regarding the stress in the press-formed part before springback occurs and information regarding the stress in the analysis model after the forced displacement is applied. The forced displacement is set based on information regarding the shape of the press-formed part before the springback occurs and information regarding the shape of the press-formed part after the springback occurs. Methods for analyzing the impact of stress.

5. The method further comprises the step of calculating information regarding the stress in the analysis model after the forced displacement has been applied. The stress influence analysis method according to claim 4.

6. The method further comprises the step of calculating information regarding the shape of the press-formed part after springback occurs, using an analysis model generated based on information regarding the shape, characteristics, and stress of the press-formed part before springback occurs. The stress influence analysis method according to claim 4 or claim 5.

7. A computer program for analyzing the influence of stress on springback that occurs in press-formed parts after press forming, Information regarding the shape, characteristics, and stress of a press-formed part after press forming and before springback occurs, Information regarding the shape and characteristics of press-formed parts after springback has occurred following press forming, The steps include obtaining information on the stress in the analysis model after applying a forced displacement to the analysis model, which is generated based on information on the shape and characteristics of the press-formed part before or after the occurrence of springback, The procedure involves performing the step of calculating the degree of influence of the stress in the press-formed part before springback occurs on the springback, based on the information regarding the stress in the press-formed part before springback occurs and the information regarding the stress in the analysis model after the forced displacement is applied. The forced displacement is set based on information regarding the shape of the press-formed part before the springback occurs and information regarding the shape of the press-formed part after the springback occurs. program.

8. The method further comprises the step of calculating information regarding the stress in the analysis model after the forced displacement has been applied. The program according to claim 7.

9. The method further comprises the step of calculating information regarding the shape of the press-formed part after springback occurs, using an analysis model generated based on information regarding the shape, characteristics, and stress of the press-formed part before springback occurs. The program according to claim 7 or claim 8.

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