Analyzer, method for analysis, and program

Abstract

To estimate the intensity of the effect that change of the internal stress of each site in a press component exercises on reduction of the internal stress of a delay breakage concerned site.SOLUTION: An analyzer executes analysis processing on a component formed by pressing a steel plate and calculates a stress effect degree as an index which shows the intensity of the effect that the internal stress in an analysis region as at least a first part of the analysis target exercises on a stress value calculated from the internal stress in an evaluation site as a second part of the analysis target.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an analysis device, an analysis method, and a program. [Background technology]

[0002] In recent years, there has been a stronger demand than ever for automobiles to improve fuel efficiency through weight reduction and crashworthiness. To achieve both, there has been an increasing trend in the use of high-strength steel plates with a tensile strength of 980 MPa or more in automotive parts, but one of the issues with the use of high-strength steel plates is delayed fracture (hydrogen embrittlement cracking). Delayed fracture is a fracture phenomenon in which brittle cracks suddenly occur a certain amount of time after press forming due to hydrogen that penetrates from the environment or tensile residual stress after press forming, and it becomes more likely to occur as the tensile strength of the steel plate increases.

[0003] It is believed that the occurrence of delayed fracture in molded products is influenced by the internal stress and plastic strain remaining in the parts after press molding. In particular, areas with high tensile residual stress and large plastic strain are more likely to experience delayed fracture.

[0004] Therefore, as a countermeasure for areas where delayed fracture is a concern after press forming, it is possible to reduce the residual internal stress.

[0005] For example, when a high-strength steel plate with a tensile strength of 1470 MPa and a thickness of 1.6 mm is drawn to form a cup-shaped part with a diameter of 105 mm and a depth of 34 mm as shown in Figure 14, it was confirmed that a maximum principal stress of approximately 910 MPa of internal stress occurs at the end of the part, causing delayed fracture. On the other hand, if a notch is made at the end as shown in Figure 15, the product shape changes, but the maximum principal stress of the internal stress at the end part where no notch is made is reduced to approximately 600 MPa, and delayed fracture does not occur.

[0006] As a method to reduce the residual internal stress without changing the product shape, it is effective to preform the part of concern so that the cross-sectional line length in the first process is longer than the product shape, and then form it to the normal dimensions in the next process and plastically deform it. For example, in the case of the shape of Figure 14, if the end diameter is preformed to be larger than that of Figure 14 and then formed into the shape of Figure 14, the end of the product will be plastically deformed and the internal stress will be reduced. However, even if this method is used to reduce the maximum principal stress of the internal stress in the end part to about 600 MPa, delayed fracture will occur. This is because the plastic strain increases even if the internal stress is reduced. Therefore, the method of directly applying plastic deformation to the part of concern to delay fracture to reduce the internal stress is not necessarily an effective measure against delayed fracture because the plastic strain increases. Note that the part of concern to delay fracture is the part that the user assumes will cause delayed fracture based on experience, etc. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2022 / 118497 Summary of the Invention [Problem to be solved by the invention]

[0008] Residual stresses occurring throughout the entire press-molded part are balanced as internal stresses within the part, so changing the stress in one area of ​​the press-molded part also changes the stress in other areas. Therefore, in order to reduce the internal stress in areas at risk of delayed fracture, it is possible to consider a method of changing the internal stress in areas other than the area at risk of delayed fracture (for example, by applying plastic deformation), thereby reducing the internal stress without increasing the plastic strain in the area at risk of delayed fracture.

[0009] However, since it is unknown how changes in internal stress in each part of a component affect the reduction of internal stress in parts at risk of delayed fracture, this method is not used in practice because it requires trial and error through molding analysis and experiments to consider a method for reducing internal stress in parts at risk of delayed fracture, which is time-consuming and costly.

[0010] In view of the above circumstances, an object of the present invention is to provide a technique for estimating the magnitude of the effect that a change in internal stress at each portion in a pressed part has on reducing the internal stress at a portion susceptible to delayed fracture. [Means for solving the problem]

[0011] One aspect of the present invention is a process for analyzing a part formed by pressing a steel plate, the process including a control unit that executes an analysis process for calculating a stress influence degree, which is an index showing the strength of the influence of internal stress in an analysis region that is at least a part of the analysis region on a stress value calculated from internal stress in an evaluation portion that is a part of the analysis region, the control unit performing the analysis process by performing a first elasticity analysis, which is an elasticity analysis including, as an initial condition, a distribution of internal stress in the analysis region at the bottom dead center of the press working, and estimating the result of a change in the analysis region caused by the internal stress, and an elasticity analysis including, as an initial condition, a distribution of internal stress that satisfies a comparison condition that the internal stress in the analysis region has changed from the internal stress at the bottom dead center of the press working, and the internal stress outside the analysis region is the internal stress in the analysis region at the bottom dead center of the press working, and estimating the result of a change in the analysis region caused by the internal stress that satisfies the comparison condition. and a second elasticity analysis, and the control unit further executes an influence acquisition process to acquire, as the stress influence degree, either one of a first type value which is a value calculated from the internal stress in the evaluation part estimated by the first elasticity analysis and the internal stress in the evaluation part estimated by the second elasticity analysis, and a second type value which is a value calculated from the internal stress in the evaluation part estimated by the first elasticity analysis, the internal stress in the evaluation part estimated by the second elasticity analysis, and a stress change rate α which is a rate of change in the internal stress in the analysis region under the comparison conditions from the internal stress at the bottom dead point of the press working, and the information indicating the shape and plate thickness of the analysis object at the bottom dead point of the press working, the information indicating the distribution of strain in the analysis object at the bottom dead point of the press working, and the information indicating the distribution of internal stress in the analysis object at the bottom dead point of the press working are obtained by forming analysis.

[0012] One aspect of the present invention is a process for analyzing a part formed by pressing a steel plate, the process comprising a control step of executing an analysis process for calculating a stress influence degree, which is an index showing the strength of the influence of internal stress in an analysis region, which is at least a part of the analysis region, on a stress value calculated from internal stress in an evaluation portion, which is a part of the analysis region, the control step includes a first elasticity analysis, which is an elasticity analysis including an initial condition of a distribution of internal stress in the analysis region at the bottom dead point of the press working, and which estimates the result of a change in the analysis region caused by the internal stress, and a second elasticity analysis, which is an index showing the strength of the influence of internal stress in an analysis region, which is at least a part of the analysis region, on a stress value calculated from internal stress in an evaluation portion, which is a part of the analysis region, the control step includes a first elasticity analysis, which is an elasticity analysis including an initial condition of a distribution of internal stress in the analysis region at the bottom dead point of the press working, the first elasticity analysis estimating the result of a change in the analysis region caused by the internal stress, and and a second elasticity analysis which is an elasticity analysis including, as an initial condition, a distribution of internal stresses which satisfies a comparison condition that the internal stress in the evaluation portion is a change from the internal stress in the evaluation portion at the bottom dead center of press working and the internal stress in the portion other than the analysis portion is an internal stress in the analysis portion at the bottom dead center of press working, and which estimates the result of the change in the analysis portion caused by the internal stress which satisfies the comparison condition. In the control step, in the analysis process, a first type value which is a value calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis and the internal stress in the evaluation portion estimated by the second elasticity analysis, and a second type value which is a value calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis and the internal stress in the evaluation portion estimated by the and further executing an influence acquisition process to acquire, as the stress influence degree, either one of the internal stress in the evaluation portion estimated by the second elastic analysis and a second type value which is a value calculated from a stress change rate α which is the rate of change of the internal stress in the analysis area under the comparison conditions from the internal stress at the bottom dead point of the press working, wherein information indicating the shape and plate thickness of the analysis object at the bottom dead point of the press working, information indicating the distribution of strain within the analysis object at the bottom dead point of the press working, and information indicating the distribution of internal stress within the analysis object at the bottom dead point of the press working are obtained by forming analysis.

[0013] One aspect of the present invention is a program for causing a computer to function as the above-described analysis device. Effect of the Invention

[0014] According to the present invention, it is possible to estimate the magnitude of the effect that a change in internal stress at each portion in a pressed part has on the internal stress at a portion susceptible to delayed fracture. [Brief description of the drawings]

[0015] [Figure 1] FIG. 2 is an explanatory diagram for explaining an analysis device according to an embodiment. [Diagram 2] FIG. 4 is a first diagram showing an example of region division according to the embodiment. [Diagram 3] FIG. 2 is a second diagram showing an example of region division in the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a relationship between an analysis target, an evaluation portion, and an analysis region in the embodiment. [Diagram 5] FIG. 2 is a diagram illustrating an example of a hardware configuration of an analysis apparatus according to an embodiment. [Figure 6] 1 is a flowchart showing an example of the flow of an analysis process executed by an analysis device according to an embodiment. [Figure 7] FIG. 1 is a first diagram showing an example of an experimental result obtained by using the analysis device of the embodiment. [Figure 8] FIG. 2 is a second diagram showing an example of an experimental result obtained by using the analysis device of the embodiment. [Figure 9] FIG. 3 is a third diagram showing an example of an experimental result obtained by using the analysis device of the embodiment. [Figure 10] FIG. 4 is a fourth diagram showing an example of an experimental result using the analysis device of the embodiment. [Figure 11] FIG. 8 is a contour diagram in which the influence of the results of an analysis of the stress influence on the components of the maximum principal stress of the internal stress of the evaluation portion shown in FIG. 7 according to the embodiment is represented by a color shade and projected onto the part shape. [Figure 12] FIG. 11 is an explanatory diagram for explaining another example of the first predetermined rule in the modified example. [Figure 13] FIG. 11 is an explanatory diagram for explaining a countermeasure target determination process in a modified example. [Figure 14] FIG. 1 is a first diagram illustrating the prior art. [Figure 15] FIG. 2 is a second diagram illustrating the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] (Embodiment) 1 is an explanatory diagram illustrating an analysis device 1 according to an embodiment. The analysis device 1 includes a control unit 11 including a processor 91, such as a CPU (Central Processing Unit), and a memory 92, which are connected via a bus, and executes a program.

[0017] The control unit 11 performs an analysis of the analysis object. The analysis object is a part formed by pressing a steel plate. The control unit 11 executes an analysis process to analyze the analysis object. The analysis process is a process to calculate a stress influence degree. The stress influence degree is the strength of the influence of the internal stress in the analysis area, which is at least a part of the analysis object, on the internal stress in the evaluation part, which is a part of the analysis object. The stress influence degree is a quantity indicating that the stronger the strength of the influence indicated by the stress influence degree, the stronger the contribution of the distribution of internal stress in the analysis area to the internal stress in the evaluation part.

[0018] The evaluation portion may be any portion determined in any way so long as it is a part of the analysis object, but may be, for example, a portion within the analysis object determined according to a predetermined rule (hereinafter referred to as the "first predetermined rule") regarding the determination of a portion estimated to be at risk of delayed fracture.

[0019] Therefore, the first predetermined rule may be, for example, a rule that a portion is designated in advance by a user of the analysis device 1. The user may designate, for example, based on experience, a portion that is likely to cause delayed fracture as an evaluation portion in the analysis device 1. Another example of the first predetermined rule may be based, for example, on the results of elastic analysis, and the details of such an example will be described later in the modified example in consideration of easy explanation. The evaluation portion may be, for example, a portion determined randomly.

[0020] The analysis area may be any part that is part of the analysis object and different from the evaluation part. The analysis area may be, for example, a part that is randomly determined from among parts different from the evaluation part. The analysis area may be, for example, a part within the analysis object that is determined according to a rule for determining a part for which the stress influence degree is estimated (hereinafter referred to as the "second predetermined rule").

[0021] The second predetermined rule may be, for example, a combination of a rule for dividing the analysis object into one or more parts (hereinafter referred to as "area division rule") and a rule for determining which of the parts divided by the area division rule is to be used as the stress influence estimation target. The area division rule is, for example, a rule for dividing the analysis object before molding into a grid along at least one of two predetermined orthogonal axes such as the X-axis or Y-axis of the XY coordinate system. The second predetermined rule may be, for example, a rule set by the user so that the part that the user wants to analyze is distinguished from other parts. In this case, the user may set the rule taking into account the machine power.

[0022] Fig. 2 is a first diagram showing an example of region division in an embodiment. In the example of Fig. 2, the circumferential direction is the X-axis, and the direction perpendicular to the circumferential direction is the Y-axis, and the analysis object 991 is divided in the Y-axis direction.

[0023] Fig. 3 is a second diagram showing an example of region division in an embodiment. In the example of Fig. 3, the surface of the analysis target is regarded as a two-dimensional plane embedded in a three-dimensional space, and the analysis target 991 is divided into a grid along two orthogonal axes set on the two-dimensional plane. In other words, the analysis target 991 is divided into a grid along two orthogonal axes set on a development of the surface of the analysis target.

[0024] FIG. 4 is a diagram showing an example of the relationship between an analysis target, an evaluation part, and an analysis area in an embodiment. FIG. 4 shows a part 900 as an example of an analysis target. FIG. 4 shows a part 901 as an example of an evaluation part. In FIG. 4, parts 902-1 to 902-7 are all examples of the analysis area. In the example of FIG. 4, part 901 is present in part 902-8. Therefore, parts of part 902-8 excluding part 901 are also examples of the analysis area. In the analysis process, for example, a stress influence level, which is the strength of the influence of part 902-2 on the internal stress generated in part 901, is estimated.

[0025] The analysis process may be performed for each of a plurality of analysis regions, which are the parts 902-1 to 902-7 and the part 902-8 excluding the part 901, and in such a case, the stress influence degree on the evaluation part is estimated for each analysis region. In the example of Fig. 4, for example, the analysis process is performed for each of a plurality of analysis regions, which are the parts 902-1 to 902-7 and the part 902-8 excluding the part 901, to obtain the stress influence degree, which is the strength of the influence of each of the parts 902-1 to 902-7 and the part 902-8 excluding the part 901 on the internal stress generated in the part 901, which is the evaluation part.

[0026] In the analysis process, a first elasticity analysis, a second elasticity analysis, and an influence degree acquisition process are executed. The first elasticity analysis is an elasticity analysis that includes the distribution of internal stress (hereinafter referred to as "first internal stress") in the analysis object at the bottom dead center of press working as an initial condition, and is an elasticity analysis that estimates the result of the change in the analysis object caused by the first internal stress.

[0027] The result of the change in the analyte caused by the first internal stress specifically indicates at least the internal stress at each position in the equilibrium state of the analyte changed by the first internal stress. The result of the change in the analyte caused by the first internal stress may further indicate the strain at each position in the equilibrium state of the analyte changed by the first internal stress.

[0028] The second elastic analysis is an elastic analysis that includes, as an initial condition, a distribution of internal stress (hereinafter referred to as "second internal stress") that satisfies a comparison condition, and estimates the results of changes in the object of analysis caused by the second internal stress.

[0029] The result of the change in the analyte caused by the second internal stress specifically indicates at least the internal stress at each position in the equilibrium state of the analyte changed by the second internal stress. The result of the change in the analyte caused by the second internal stress may further indicate the strain at each position in the equilibrium state of the analyte changed by the second internal stress.

[0030] The comparison condition is that the internal stress in the analysis area is a change from the internal stress at the bottom dead point of the press working, and the internal stress outside the analysis area is the internal stress in the analysis object at the bottom dead point of the press working. In other words, the comparison condition is that the internal stress in the analysis area is different from the internal stress at the bottom dead point of the press working, and the internal stress outside the analysis area is the internal stress in the analysis object at the bottom dead point of the press working.

[0031] The internal stress in the analysis region under the comparison conditions may be different from the internal stress at the bottom dead center of the press working as long as at least some of the stress components have changed. The stress components that change may be one or more of the following: a directional stress component in an arbitrary direction, an average stress component obtained by averaging the in-plane stress in the plate thickness direction, a deviatoric stress component obtained by excluding the average stress component from the internal stress, or all of the components of the internal stress. The change is, for example, a change to a value obtained by multiplying the stress component that is the subject of the change by (1-α). α is the stress change rate. The stress change rate is the proportion of the change in stress.

[0032] For example, when analyzing the effect of the average stress component of the internal stress in the analysis area on the internal stress of the evaluation area, the internal stress of the analysis area can be determined by multiplying the average stress component by (1-α). When analyzing the effect of all components of the internal stress in the analysis area on the internal stress of the evaluation area, all internal stresses in the analysis area can be changed to a value obtained by multiplying all stress components by (1-α).

[0033] For example, if α is 0.2, it means that the target stress component is multiplied by 0.8 (= 1-0.2) to reduce the magnitude of the target stress by 20%, and if α is -0.5, it means that the target stress component is multiplied by 1.5 (= 1-(-0.5)) to increase the magnitude of the target stress by 50%, and if α is 1, the target stress will be set to 0.

[0034] However, if α is set to 0, the internal stress in the analysis region does not change, so α cannot be set to 0. Therefore, α can be any value other than 0.

[0035] From the above, the internal stress in the analysis area under the comparative conditions is summarized. The internal stress in the analysis area under the comparative conditions is different from the internal stress at the bottom dead point of the press working in that at least some of the stress components have changed, and the changing stress components are either one or more of the following: a directional stress component in an arbitrary direction, an average stress component obtained by averaging the stress in the thickness direction in the in-plane direction, and a deviatoric stress component obtained by excluding the average stress component from the internal stress, or all of the components of the internal stress, and the change in the changing stress component is a change from the value of the stress component before the change to a value obtained by multiplying the stress component before the change by a value obtained by subtracting a stress change rate α, which is an arbitrary coefficient other than zero, from 1.

[0036] Since the first elasticity analysis is an elasticity analysis, the initial conditions of the first elasticity analysis further include the shape and plate thickness of the analysis object at the bottom dead center of the press working. Since the first elasticity analysis is an elasticity analysis, the physical property values ​​used in the elasticity analysis are also used. Since the second elasticity analysis is an elasticity analysis, the initial conditions of the second elasticity analysis further include the shape and plate thickness of the analysis object at the bottom dead center of the press working. Since the second elasticity analysis is an elasticity analysis, the physical property values ​​used in the elasticity analysis are also used. The physical property values ​​used in the first elasticity analysis and the second elasticity analysis include, for example, Young's modulus and Poisson's ratio. Hereinafter, information indicating the physical property values ​​used in the elasticity analysis is referred to as physical property information.

[0037] The information that provides the initial conditions in the first elasticity analysis, that is, information indicating the shape and thickness of the analysis object at the bottom dead point of the press working and information indicating the distribution of internal stress within the analysis object at the bottom dead point of the press working, are obtained, for example, by forming analysis. In the second elasticity analysis, the information indicating the shape and thickness of the analysis object at the bottom dead point of the press working and information indicating the distribution of internal stress within the analysis object at the bottom dead point of the press working are also obtained, for example, by forming analysis. The distribution of internal stress that satisfies the comparison condition, which is one of the initial conditions in the second elasticity analysis, is obtained using information indicating the distribution of internal stress within the analysis object at the bottom dead point of the press working.

[0038] The molding analysis may be executed in advance before the first elasticity analysis and the second elasticity analysis in the analysis process, or may be executed before the first elasticity analysis and the second elasticity analysis by another device different from the analysis device 1. When the molding analysis is executed by another device, the analysis device 1 obtains the results of the analysis process from the other device that executed the analysis process.

[0039] The influence degree acquisition process is a process for acquiring either a first type value or a second type value as a stress influence degree based on the results of the first elasticity analysis and the second elasticity analysis. The first type value is a value calculated from the internal stress in the evaluation part estimated by the first elasticity analysis and the internal stress in the evaluation part estimated by the second elasticity analysis. The second type value is a value calculated from the internal stress in the evaluation part estimated by the first elasticity analysis, the internal stress in the evaluation part estimated by the second elasticity analysis, and the stress change rate α.

[0040] Therefore, the stress influence degree is, for example, the change σ1-σ2 obtained by subtracting the stress value σ2 calculated from the internal stress in the evaluation portion estimated by the second elasticity analysis from the stress value σ1 calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis.

[0041] The stress influence degree may be, for example, the change rate (σ1-σ2) / σ1 obtained by subtracting the stress value σ2 calculated from the internal stress in the evaluation portion estimated by the second elasticity analysis from the stress value σ1 calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis, and dividing the change rate by the stress value σ1 calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis.

[0042] The stress influence degree may be, for example, a change amount (σ1-σ2) / α taking into consideration the stress change rate obtained by dividing the change amount obtained by subtracting the stress value σ2 calculated from the internal stress in the evaluation portion estimated by the second elasticity analysis from the stress value σ1 calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis by the stress value σ2 calculated from the internal stress in the evaluation portion estimated by the second elasticity analysis, by the value obtained by subtracting the stress change rate α under the comparison conditions from 1.

[0043] The stress influence degree may be, for example, a change rate (σ1-σ2) / σ1 / α, which takes into account a stress change rate obtained by dividing the change amount obtained by subtracting the stress value σ2 calculated from the internal stress in the evaluation portion estimated by the second elasticity analysis from the stress value σ1 calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis by the stress value σ1 calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis, by the stress value σ1 calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis, and further dividing this change rate by the value obtained by subtracting the stress change rate α under the comparison conditions from 1.

[0044] Although several examples of stress influence have been given so far, these are merely examples. As described above, the definition of stress influence is a quantity indicating the strength of influence of the internal stress in the analysis region, which is at least a part of the analysis target, on the internal stress in the evaluation part, which is a part of the analysis target. Therefore, the index indicating the stress influence is not limited to a specific calculation method, but may be an index indicating the amount of change in the internal stress in the evaluation part estimated by the second elasticity analysis relative to the internal stress in the evaluation part estimated by the first elasticity analysis, as required by the analyst.

[0045] The stress value calculated from the internal stress is the maximum value within the evaluation area of ​​either the von Mises stress, the equivalent stress, or a specific stress component of the internal stress calculated from the internal stress estimated by the first elastic analysis or the second elastic analysis.

[0046] The specific stress component is any one of the maximum principal stress, a directional stress component in an arbitrary direction, an in-plane principal stress component, an average stress component obtained by averaging the in-plane stress in the thickness direction, a moment component due to a deviatoric stress obtained by subtracting the average stress component from the internal stress, a directional stress component in an arbitrary direction in the surface layer, the maximum in-plane principal stress in the surface layer, and the in-plane principal stress component in the surface layer.

[0047] Therefore, obtaining a stress value from internal stress means, for example, when analyzing the degree of stress influence on the maximum principal stress of the evaluation part, obtaining σ1 and σ2 by finding the maximum value of the maximum stress in the evaluation part from the internal stresses of the evaluation part obtained by the first elasticity analysis and the second elasticity analysis. Also, obtaining a stress value from internal stress means, when analyzing the degree of stress influence on the von Mises stress of the evaluation part, obtaining σ1 and σ2 by finding the maximum value of the von Mises stress in the evaluation part from the internal stresses of the evaluation part obtained by the first elasticity analysis and the second elasticity analysis.

[0048] Below, examples will be shown in which the component 900 in Fig. 4 is analyzed and the stress influence degree is calculated by a number of calculation methods. Other examples will be described in the modified examples described later.

[0049] 5 is a diagram showing an example of a hardware configuration of the analysis device 1 in the embodiment. As described above, the analysis device 1 includes the control unit 11 and executes a program. The analysis device 1 functions as a device including the control unit 11, an input unit 12, a communication unit 13, a storage unit 14, and an output unit 15 by executing the program.

[0050] More specifically, the processor 91 reads out a program stored in the storage unit 14 and stores the read out program in the memory 92. The processor 91 executes the program stored in the memory 92, whereby the analysis device 1 functions as a device including a control unit 11, an input unit 12, a communication unit 13, a storage unit 14, and an output unit 15.

[0051] The control unit 11 controls the operation of various functional units included in the analysis device 1. The control unit 11 executes, for example, an analysis process. The control unit 11 controls, for example, the operation of the output unit 15. The control unit 11 records, for example, various pieces of information generated by the execution of the analysis process in the storage unit 14.

[0052] The input unit 12 includes input devices such as a mouse, a keyboard, and a touch panel. The input unit 12 may be configured as an interface that connects these input devices to the analysis device 1. The input unit 12 accepts input of various information to the analysis device 1. For example, information used to execute the analysis process is input to the input unit 12. The information used to execute the analysis process may be, for example, information indicating an evaluation site. The information used to execute the analysis process may be, for example, information indicating an analysis region. The information used to execute the analysis process may be, for example, information indicating an initial condition of a first elasticity analysis. The information used to execute the analysis process may be, for example, information indicating an initial condition of a second elasticity analysis. The information used to execute the analysis process may be, for example, physical property information.

[0053] The information used to execute the analysis process may be input via the communication unit 13. The information used to execute the analysis process does not necessarily have to be input via the input unit 12 or the communication unit 13, and may be stored in advance in the storage unit 14. For ease of explanation, the analysis device 1 will be described below using as an example a case in which the information used to execute the analysis process has been stored in advance in the storage unit 14.

[0054] The communication unit 13 includes a communication interface for connecting the analysis device 1 to an external device. The communication unit 13 communicates with the external device via a wired or wireless connection. The external device is, for example, a device that inputs information used to execute the analysis process. In such a case, the communication unit 13 acquires information used to execute the analysis process by communicating with the device that inputs the information used to execute the analysis process. The communication unit 13 may acquire, for example, the results of molding analysis. The results of molding analysis do not necessarily need to be acquired via the communication unit 13, and may be acquired via the input unit 12.

[0055] The storage unit 14 is configured using a computer-readable storage medium device (non-transitory computer-readable recording medium) such as a magnetic hard disk device or a semiconductor storage device. The storage unit 14 stores various information related to the analysis device 1. The storage unit 14 stores information inputted, for example, via the input unit 12 or the communication unit 13. Therefore, the storage unit 14 stores information used, for example, in the execution of an analysis process. The storage unit 14 stores various information generated, for example, by the execution of a process by the control unit 11. Therefore, the storage unit 14 stores various information generated, for example, by the execution of an analysis process. Note that the information used in the execution of the analysis process stored in the storage unit 14 may be changeable by a user via the input unit 12 or the communication unit 13. The storage unit 14 may have already stored the results of the molding analysis before the execution of the first elastic analysis and the second elastic analysis.

[0056] The output unit 15 outputs various information. The output unit 15 includes a display device such as a CRT (Cathode Ray Tube) display, a liquid crystal display, or an organic EL (Electro-Luminescence) display. The output unit 15 may be configured as an interface that connects these display devices to the analysis device 1. The output unit 15 outputs, for example, information input to the input unit 12. The output unit 15 may display, for example, various information generated by the execution of processing by the control unit 11. Thus, the output unit 15 may display, for example, the execution result of an analysis processing.

[0057] Fig. 6 is a flowchart showing an example of the flow of the analysis process executed by the analysis device 1 in the embodiment. Fig. 6 is a flowchart showing an example of a case where the execution result of the molding analysis has been stored in advance in the storage unit 14. If the molding analysis has not been executed, the molding analysis is executed before executing step S101.

[0058] The control unit 11 executes a first elasticity analysis (step S101). Next, the control unit 11 executes a second elasticity analysis (step S102). Next, the control unit 11 executes an influence degree acquisition process (step S103). Note that steps S101 and S102 do not necessarily need to be executed after step S101 is executed, and may be executed at any timing as long as step S102 is executed before the execution of step S103 starts.

[0059] <Experimental Results> 7 to 10 are diagrams showing an example of an experimental result using the analysis device 1. In the experiment, the part 900 in Fig. 4, which was made by drawing a steel plate having a tensile strength of 1470 MPa and a thickness of 1.6 mm into a cup shape having an outer diameter of 105 mm and a depth of 34 mm, was used as the analysis object, and an analysis process was performed with a portion 901 in Fig. 4 as the evaluation portion.

[0060] In the experiment, information indicating the shape and plate thickness of the analysis object in the analysis process, information indicating the distribution of strain within the analysis object at the bottom dead point of press working, and information indicating the distribution of internal stress within the analysis object at the bottom dead point of press working were obtained by forming analysis through computer simulation using the finite element method. In the experiment, the analysis areas were each of the eight areas obtained by dividing part 900 into eight areas 902-1 to 902-8 shown in Figure 4. In the experiment, the evaluation parts were each of the areas obtained by dividing area 901 shown in Figure 4.

[0061] In Figures 7 to 11, the column "Evaluation part" indicates the evaluation part for evaluating the strength of the influence of the distribution of internal stress in the analysis area. The column "Stress type of evaluation part to be evaluated" indicates the type of stress component of the internal stress to be evaluated in the evaluation part. The column "Analysis area" indicates the area for analyzing the strength of the influence on the internal stress of the evaluation part of the area. The column "Type of stress to analyze" indicates the stress component to be analyzed among the internal stress of the analysis area. The column "Stress change rate α" indicates the stress change rate α, which is the ratio of the change in internal stress at the bottom dead center of press working in the analysis area under comparison conditions. The column "Stress value σ1" indicates the stress value σ1 calculated from the internal stress in the evaluation part estimated by the first elastic analysis in the analysis process. The column "Stress value σ2" indicates the stress value σ2 calculated from the internal stress in the evaluation part estimated by the second elastic analysis in the analysis process.

[0062] 7 to 10, the columns of "influence 1", "influence 2", "influence 3" and "influence 4" represent stress influences calculated by different calculation methods. "Influence 1" is the change obtained by subtracting the stress value σ2 calculated from the internal stress in the evaluation part estimated by the second elasticity analysis from the stress value σ1 calculated from the internal stress in the evaluation part estimated by the first elasticity analysis, i.e., σ1-σ2, as the influence. "Influence 2" is the change rate obtained by dividing the change obtained by subtracting the stress value σ2 calculated from the internal stress in the evaluation part estimated by the second elasticity analysis from the stress value σ1 calculated from the internal stress in the evaluation part estimated by the first elasticity analysis by the stress value σ2 calculated from the internal stress in the evaluation part estimated by the second elasticity analysis, by the stress value σ1 calculated from the internal stress in the evaluation part estimated by the first elasticity analysis, i.e., the percentage of (σ1-σ2) / σ1.

[0063] "Influence level 3" is the change amount taking into consideration the stress change rate of the internal stress, i.e. (σ1-σ2) / α, obtained by dividing the change amount obtained by subtracting the stress value σ2 calculated from the internal stress in the evaluation part estimated by the second elasticity analysis from the stress value σ1 calculated from the internal stress in the evaluation part estimated by the first elasticity analysis by the stress value σ2 calculated from the internal stress in the evaluation part estimated by the second elasticity analysis, by the stress value σ1 calculated from the internal stress in the evaluation part estimated by the first elasticity analysis, and further dividing the change amount obtained by subtracting the stress value σ2 calculated from the internal stress in the evaluation part estimated by the second elasticity analysis from the stress value σ1 calculated from the internal stress in the evaluation part estimated by the first elasticity analysis by the stress value σ1 calculated from the internal stress in the evaluation part estimated by the first elasticity analysis, by the stress value α of the internal stress, and is a percentage of (σ1-σ2) / σ1 / α, taking into consideration the stress change rate of the internal stress.

[0064] 7 to 10, furthermore, "locations with high influence level 1" indicate analysis regions where the stress influence level 1 was the highest among the analysis regions analyzed as a result of the analysis process.

[0065] The results in Fig. 7 are the results of analyzing the stress influence degree on the maximum principal stress component of the internal stress of the evaluation part 901 by the radial stress, which is the in-plane direction stress component of the internal stress of seven analysis parts out of the analysis parts 901-1 to 901-6 and the analysis part 902-7, excluding the evaluation part 901. For example, looking at the analysis part 902-5, the stress value σ1 calculated as the radial stress using the stress component analyzed from the first internal stress by the first elastic analysis is 909 MPa. As a comparison condition, the stress value σ2 calculated as the radial stress using the stress component analyzed from the second internal stress obtained by the second elastic analysis as the internal stress changed by dividing the stress change rate α = 0.8 by 0.2, which is 1, for the radial component of the internal stress of the analysis part 902-5 is 590 MPa.

[0066] Influence level 1 (amount of change) calculated from σ1 and σ2 is 319 MPa, and influence level 2 (percentage of change) is 35.1%. Influence level 3 (amount of change taking into account the rate of change in stress) calculated from σ1, σ2, and α is 399 MPa, and influence level 4 (percentage of change taking into account the rate of change in stress) is 43.9%. The same is true for the other analysis regions.

[0067] In addition, the analysis process results show that the analysis area 902-5 has the largest influence 1 (amount of change), indicating that the influence on the stress of the evaluation area is strong. Therefore, the experimental results show that in order to reduce the risk of delayed fracture occurring in the evaluation area, it is effective to take measures to reduce the stress in the analysis area 902-5, thereby reducing the stress in the evaluation area.

[0068] FIG. 8 shows the results of an analysis of the degree of stress influence on the circumferential stress component of the internal stress of the evaluation area 901, caused by the deviatoric stress component of the internal stress of seven analysis areas excluding the evaluation area 901, which are analysis areas 901-1 to 901-6 and analysis area 902-7.

[0069] FIG. 9 shows the results of an analysis of the stress effect of the circumferential component of the internal stress in seven analysis areas excluding the evaluation area 901 among the analysis areas 901-1 to 901-6 and the analysis area 902-7 on the circumferential stress component of the internal stress in the evaluation area 901.

[0070] FIG. 10 shows the results of an analysis of the stress influence on the circumferential stress components of the internal stress of the evaluation portion 901, caused by all the stress components of the internal stress of six analysis regions 901-1 to 901-6.

[0071] 11 is a contour diagram in which influence 1 (stress difference) of the result of analyzing the stress influence on the components of the maximum principal stress of the internal stress of the evaluation part 901 shown in FIG. 7 of the embodiment is represented by color shading and projected onto the part shape, and is a diagram expressing the distribution of the stress influence so as to facilitate visual and three-dimensional understanding of the distribution of the stress influence by the analyst. Note that the contour diagram only needs to project the stress influence as color or color shading onto the shape of the analysis target, and does not necessarily have to be represented by color shading (i.e. color shading) alone.

[0072] In addition, the control unit 11 may output to a specified output destination an image showing a contour diagram in which the stress influence degree at multiple evaluation locations is projected onto the shape of the object of analysis as color or color intensity, such as the contour diagram in Figure 11.

[0073] The analysis device 1 configured in this manner acquires the stress influence degree by executing the first elasticity analysis, the second elasticity analysis, and the influence degree acquisition process for the evaluation part to be analyzed. The greater the internal stress in the evaluation part, the more likely delayed fracture is to occur in the evaluation part. Therefore, if the acquired stress influence degree indicates that the internal stress in the evaluation part estimated by the second elasticity analysis is smaller than the internal stress in the evaluation part estimated by the first elasticity analysis, this means that the internal stress in the evaluation part, which is a cause of delayed fracture, can be reduced by making efforts to reduce the internal stress in the analysis region.

[0074] Moreover, the acquired stress influence degree of each analysis region means that the greater the stress influence degree of the analysis region, the greater the effect of reducing the internal stress of the evaluation portion when the internal stress of the analysis region is reduced. In this way, the analysis device 1 of the embodiment performs an analysis of the evaluation portion as a portion at risk of delayed fracture, thereby making it possible to estimate the magnitude of the influence that the internal stress change of each portion in the press part has on the internal stress of the portion at risk of delayed fracture.

[0075] (Modification) <Other examples of the first prescribed rule> Another example of the first predetermined rule, which is a rule for determining an evaluation part, will be described. Another example of the first predetermined rule is a rule for determining an evaluation part based on the result of the zero-th elasticity analysis, the strain obtained by the molding analysis, and a function (hereinafter referred to as an "example function") in which the independent variable is a strain value calculated from the strain and the objective variable is a stress value calculated from the internal stress. Note that this example function is an example of a reference function, which is a function that represents a stress value relative to a strain value.

[0076] The zeroth elasticity analysis is an elasticity analysis that includes as initial conditions the distribution of internal stress in the analysis object at the bottom dead point of press working and the shape and plate thickness of the analysis object at the bottom dead point of press working, that estimates the change in the analysis object caused by the internal stress in the analysis object at the bottom dead point of press working, and that obtains the internal stress in the analysis object. Hereinafter, the internal stress in the analysis object obtained by the zeroth elasticity analysis will be referred to as the zeroth internal stress. The zeroth internal stress, the zeroth internal stress, is the result of the zeroth elasticity analysis.

[0077] The determination of the evaluation portion based on the result of the zero-th elasticity analysis and the criterion function will be described in more detail with reference to FIG. 12, taking as an example a case where the criterion function is an example function.

[0078] FIG. 12 is an explanatory diagram for explaining another example of the first predetermined rule in the modified example. FIG. 12 shows a graph G100. The graph G100 is a graph showing the relationship between the stress value and the strain value for a plurality of evaluation sites of the part 900 in FIG. 4, which is formed by drawing a steel plate having a tensile strength of 1470 MPa and a thickness of 1.6 mm into a cup shape having an outer diameter of 105 mm and a depth of 34 mm. Specifically, the graph G100 is a graph showing the relationship between the stress value and the strain value obtained by the following process. In order to obtain the graph G100, a forming analysis was first performed by computer simulation using the finite element method. This forming analysis obtained information indicating the shape and thickness at the bottom dead center of the press working to be analyzed, the distribution of internal stress, and information indicating the distribution of strain. Next, in order to obtain the graph G100, a zero-th elasticity analysis was performed with the obtained shape and thickness and information indicating the distribution of internal stress as initial conditions. This zero-th elasticity analysis gave stress and strain values ​​for a number of evaluation sites. Graph G100 shows the relationship between stress and strain thus obtained.

[0079] The graph in FIG. 12 is merely an example, and the stress values ​​are values ​​for the maximum in-plane principal stress component. The strain values ​​are for equivalent plastic strain. There are various types of stress, but the stress values ​​in FIG. 12 are specifically the values ​​of one specified stress component out of three types of stress components, namely, von Mises stress, equivalent stress, or internal stress, calculated from internal stress. Furthermore, even if it is a specified type of stress component, its value differs depending on the location. Therefore, the stress values ​​in FIG. 12 are the maximum values ​​of the one type of stress component in the evaluation area. In summary, the stress values ​​in FIG. 12 are the maximum values ​​of any one of the von Mises stress, equivalent stress, or internal stress calculated from internal stress, in the evaluation area.

[0080] The one type of stress component is any one of a maximum principal stress, a directional stress component in an arbitrary direction, an in-plane principal stress component, an average stress component obtained by averaging the in-plane stress in the thickness direction, a moment component due to a deviatoric stress obtained by subtracting the average stress component from the internal stress, a directional stress component in an arbitrary direction in the surface layer, a maximum in-plane principal stress in the surface layer, and an in-plane principal stress component in the surface layer.

[0081] The strain value may be any of the maximum principal strain, maximum plastic strain, strain in any direction, plastic strain in any direction, equivalent strain, equivalent plastic strain, maximum principal strain of the surface layer, maximum plastic strain of the surface layer, strain in any direction of the surface layer, and plastic strain in any direction of the surface layer, which are calculated from the strain, and may be the maximum value in the evaluation area. In the example of Fig. 12, the unit of the vertical axis is MPa, and the unit of the horizontal axis is percentage.

[0082] Fig. 12 shows a set of stress values ​​calculated from the internal stress indicated by the zeroth internal stress in multiple evaluation sites in the analysis object and strain values ​​calculated from the strain obtained by molding analysis. Data P903-1 to P903-11 are shown in Fig. 12. All of these are sets of stress values ​​indicated by the zeroth internal stress and strain values ​​obtained by molding analysis, and different sets show strain values ​​and stress values ​​indicated by the zeroth internal stress in different evaluation regions in the analysis object. Therefore, data P903-1 to P903-11 shown in Fig. 12 are in one-to-one correspondence with the evaluation regions in the analysis object.

[0083] To explain examples of numerical values, for example, data P903-1 indicates that the strain value in the associated portion is approximately 0.125, and the stress value indicated by the zeroth internal stress is approximately 1500. For example, data P903-11 indicates that the strain in the associated portion is approximately 0.28, and the internal stress indicated by the zeroth internal stress is approximately 900.

[0084] In Fig. 12, graph G101 is a graph of the reference function. Data located in region R101 in Fig. 12 satisfies the condition that the internal stress indicated by the data is greater than the internal stress indicated by the reference function. Data located in region R102 in Fig. 12 satisfies the condition that the internal stress indicated by the data is smaller than the internal stress indicated by the reference function.

[0085] The criterion function is, for example, a function that indicates the upper limit of the stress value that occurs in the material, below which delayed fracture is assumed to not occur in practice, with respect to the magnitude of the strain value applied to the material. The occurrence of delayed fracture is a complex phenomenon that is influenced by factors other than strain and stress values, such as the amount of hydrogen that penetrates the material, the surface condition of the material, the environment, and temperature, and the detailed mechanism has not been clarified, so it is difficult to determine the exact conditions for delayed fracture to occur. However, since the occurrence of delayed fracture is greatly influenced by strain and stress, it is possible to determine a guideline for the stress below which delayed fracture is assumed to not occur in practice, for a strain value, in automobile parts formed by pressing general steel sheets (i.e., under the conditions of the amount of hydrogen that penetrates the material, the surface condition of the material, the environment, and temperature in the press forming of general automobile parts). For example, a delayed fracture test is performed on a material that has been strained by plastic deformation, in which multiple levels of stress are applied under any environment and maintained for a certain period of time to confirm the occurrence of delayed fracture, and the stress value below which delayed fracture is assumed to not occur can be determined. The environment for this delayed fracture test may be the actual environment in which the pressed part is used, or an environment in which the part is immersed in an acidic solution in order to shorten the time until delayed fracture occurs, or any other environment may be selected by the analyst.

[0086] Therefore, each stress value for the strain value represented by the criterion function is a value that is determined in advance by a predetermined determination method. The predetermined determination method may be, for example, a determination method based on the results of actual measurement of delayed fracture, such as the results of the delayed fracture test described above. The predetermined determination method is not limited to a determination method based on a delayed fracture test, and may be any determination method that can obtain a function that represents a guideline for the stress below which an analyst believes that delayed fracture will not occur in practical terms, and may be a determination method based on experience, a metallurgical theory, or a method that takes into account a safety factor.

[0087] In addition, if the stress determined for the strain value is equal to or exceeds the guideline stress value at which delayed fracture is not expected to occur, there is a risk that delayed fracture will occur (although it is difficult to determine whether delayed fracture will occur because factors other than strain and stress, such as the amount of absorbed hydrogen, the condition of the material surface, and the environment and temperature, also affect delayed fracture), and the higher the stress value, the higher the risk is considered to be.

[0088] Therefore, in the example of Figure 12, data located in region R101 has a risk of delayed fracture in its corresponding portion. Data located in region R102 can be considered to have no practical risk of delayed fracture in its corresponding portion. Furthermore, even among data located in region R101, the risk of delayed fracture increases as the data moves away from the criterion function, i.e., the stress value is higher. Therefore, as an index of the risk of delayed fracture, the value obtained by dividing the stress value of the target portion obtained by the zeroth elasticity analysis by the stress value indicated by the criterion function when the magnitude of the strain value at that portion is the value of the independent variable of the criterion function is defined as the risk.

[0089] For example, under certain strain and stress values, when the amount of absorbed hydrogen is small and the surface quality of the material is good and delayed fracture is unlikely to occur, delayed fracture will not occur even if the risk is 105%, exceeding 100%, but delayed fracture may occur under the same conditions when only the stress value increases and the risk reaches 150%. In this way, if the risk is low, delayed fracture is unlikely to occur even under conditions where delayed fracture is likely to occur, and the higher the risk, delayed fracture will occur even under conditions where delayed fracture is more unlikely to occur. Therefore, the risk can be used as a guide to compare the relative merits of the risk of delayed fracture occurring under the same conditions except for stress.

[0090] Furthermore, since delayed fracture can be considered not to occur in practice if the risk is 100% or less, a high risk means that a large amount of stress must be reduced in order to prevent the occurrence of delayed fracture, and the risk serves as a guideline indicating the amount of stress that must be reduced in order to prevent the occurrence of delayed fracture.

[0091] Therefore, for data P903-1 to P903-13, the risk of delayed fracture is higher than 100% in the corresponding areas, and there is a risk of delayed fracture occurring, while for data P903-14 to P903-22, the risk of delayed fracture is lower than 100% in the corresponding areas, and therefore it can be considered that there is no practical risk of delayed fracture occurring.

[0092] In this way, by using the zeroth internal stress and the criterion function, it is possible to compare the presence or absence of a risk of delayed fracture for a desired portion of an analysis object, and to compare the relative severity of the risk of delayed fracture if a risk exists. It is also possible to determine the magnitude of stress that should be reduced in order to reduce the risk to 100% or less and thereby eliminate the risk of fracture.

[0093] <An example of a process for determining an evaluation portion based on the result of the zero-th elasticity analysis and a criterion function> With the explanation of FIG. 12 in mind, an example of the process of determining an evaluation part based on the result of the zeroth elasticity analysis and the criterion function (hereinafter referred to as the "evaluation part determination process") will be explained using an example in which the process is performed by the analysis device 1 for simplicity of explanation. Note that the evaluation part determination process does not necessarily have to be performed by the analysis device 1, but may be performed by another device. In such a case, the analysis device 1 obtains the result of the process performed by the other device through communication. The result of the process performed by the other device is, specifically, information indicating the determined evaluation part.

[0094] Information indicating the criterion function is stored in advance in the memory unit 14 of the analysis device 1. In the analysis device 1, the control unit 11 executes an evaluation part determination process. By executing the evaluation part determination process, the control unit 11 first executes a zeroth elasticity analysis. By executing the zeroth elasticity analysis, a zeroth internal stress is obtained. Next, the control unit 11 obtains a risk level for each evaluation part of the analysis target based on the result of the zeroth elasticity analysis, the strain obtained in the molding analysis, and the criterion function. Next, the control unit 11 determines an evaluation part for evaluating the stress influence level based on the risk level and on a sub-determination rule.

[0095] The secondary determination condition is a predetermined rule for determining an evaluation part for evaluating the stress influence degree based on the risk. The secondary determination condition includes at least a condition that the stress value at a part determined as the evaluation part for evaluating the stress influence degree is higher than the stress value indicated by the criterion function when the magnitude of the strain value at the part obtained by the forming analysis is set as the independent variable of the criterion function.

[0096] If there is no part that satisfies the secondary determination condition, the control unit 11 controls the operation of the output unit 15 to output information to the effect that it is not possible to determine an evaluation part.

[0097] The secondary determination condition is, for example, a rule that, among candidates for evaluation parts for evaluating stress influence designated in advance by a user or the like, a part with a risk level greater than 100% and the highest risk level is determined as the evaluation part for evaluating stress influence. Note that the evaluation part for evaluating stress influence means a part that is the subject of evaluation of stress influence. Note that, if there is no part with a risk level greater than 100%, the control unit 11 controls the operation of the output unit 15 to output information that it is not possible to determine an evaluation part for evaluating stress influence.

[0098] It is not necessary that the computer performs all the determination of the evaluation part for evaluating the stress influence degree, and for example, the zeroth elasticity analysis may be performed by a computer, and the evaluation part for evaluating the stress influence degree may be determined by a human using the result of the zeroth elasticity analysis (i.e., the zeroth internal stress) and the reference function. In order to reduce the burden of human decision-making, the control unit 11 may control the operation of the output unit 15 to display a graph showing the zeroth internal stress as shown in the example of FIG. 12 after performing the zeroth elasticity analysis, for example.

[0099] Therefore, for example, the control unit 11 may control the operation of the output unit 15 to output a burden reduction image to a predetermined output destination. The burden reduction image is a graph taking strain values ​​as the first axis and stress values ​​as the second axis, and is an image showing a graph showing the relationship between the strain of one or more parts of a part generated by press molding and either or both of the stress of the analysis result of a first elasticity analysis with the part as the evaluation part and the stress of the analysis result of a second elasticity analysis with the part as the evaluation part, and the strain of the part, and also showing a reference function. An example of a burden reduction image is the image in FIG. 12.

[0100] The strain value shown in the load-reduced image is either one of those based on the equivalent plastic strain or the maximum principal strain component, and the stress value shown in the load-reduced image is either one of those based on the in-plane stress component, those based on the in-plane principal stress component, those based on the average stress component obtained by averaging the in-plane stress in the thickness direction, those based on the deviatoric stress component obtained by subtracting the average stress component from the internal stress, those based on the surface stress component which is the stress of the surface layer, those based on the Mises stress, or those based on the equivalent stress.

[0101] The predetermined output destination to which the burden reducing image is output may be, for example, a monitor or a printer. Therefore, the output of the burden reducing image may be, for example, a display or a print. The output unit 15 itself may be a monitor or a printer that outputs the burden reducing image.

[0102] <Example of stress effect> The stress influence degree may be any value indicating the difference between the internal stress in the evaluation part estimated by the first elasticity analysis and the stress value in the evaluation part estimated by the second elasticity analysis. Therefore, the stress influence degree may be, for example, a result of subtracting the stress value in the evaluation part estimated by the first elasticity analysis from the stress value in the evaluation part estimated by the second elasticity analysis. The stress influence degree may be, for example, a value obtained by dividing the stress value in the evaluation part estimated by the first elasticity analysis by the stress value in the evaluation part estimated by the second elasticity analysis. The stress influence degree may be, for example, a value obtained by dividing the stress value in the evaluation part estimated by the second elasticity analysis by the stress value in the evaluation part estimated by the first elasticity analysis.

[0103] When the first elasticity analysis and the second elasticity analysis are performed to estimate not only the internal stress but also the strain in the evaluation part, the stress influence degree may be, for example, the difference between the above-mentioned risk values. More specifically, it may be the difference between the risk value obtained by the strain value and the stress value in the evaluation part obtained by the first elasticity analysis and the reference function, and the risk value obtained by the strain value and the stress value in the evaluation part obtained by the second elasticity analysis and the reference function.

[0104] The risk value is the difference from the reference function, and cannot be said to indicate the difference in stress value precisely. However, in many cases, the difference between the strain value at the evaluation part obtained by the first elasticity analysis and the strain value at the evaluation part obtained by the second elasticity analysis is almost zero, so in many cases, the risk value indicates the difference between the stress value at the evaluation part estimated by the first elasticity analysis and the stress value at the evaluation part estimated by the second elasticity analysis, similar to the stress influence degree.

[0105] <An example of processing for measures based on the results of risk estimation> After estimating the risk by executing the analysis process, the control unit 11 may execute a process (hereinafter referred to as "countermeasure target determination process") to determine, based on the estimation result, a portion where processing to relieve internal stress is desirable in order to suppress the occurrence of delayed fracture. Specifically, the countermeasure target determination process is a process to determine the portion with the highest risk as the countermeasure target portion. The control unit 11 may control the operation of the output unit 15 to output the portion determined by executing the countermeasure target determination process.

[0106] In the countermeasure target determination process, the area with the highest risk is determined as the countermeasure target area. Therefore, if measures are taken to relieve the internal stress in the determined area, the risk of delayed fracture occurring in the evaluated area will be reduced more than if measures were taken in other areas.

[0107] Fig. 13 is an explanatory diagram for explaining the countermeasure target determination process in the modified example. Graph G200 shown in Fig. 13 is a graph showing the relationship between strain value and stress value. The horizontal axis of graph G200 shows strain value, and the vertical axis shows stress value. Graph G202 is a graph of a reference function. Data located in region R201 has a high risk of greater than 100% in the corresponding part, and data located in region R202 has a low risk of less than 100% in the corresponding part.

[0108] In the example of Fig. 13, data P904-1 indicates stress values ​​and strain values ​​in part 901 obtained as a result of a first elasticity analysis in which part 900 in Fig. 4 is the analysis target and part 901 is the evaluation target. Data P904-2 indicates stress values ​​and strain values ​​in part 901 obtained as a result of a second elasticity analysis in which part 900 shown in Fig. 4 is the analysis target, part 901 is the evaluation target, part 902-2 in Fig. 4 is the analysis region, and the internal stress in the analysis region is set to zero regardless of the position within the analysis region.

[0109] The example of Figure 13 shows that when the internal stress in part 902-2 becomes zero, the risk in the evaluated part drops from a value greater than 100, which is a risk of delayed fracture occurring, to a value below 100%, which is no risk of delayed fracture occurring.

[0110] In addition, when the internal stress in the analysis region is changed from the internal stress at the bottom dead center of press working in the second elastic analysis, the internal stress to be changed may be one or more of a directional stress component in any direction, an in-plane principal stress component, an average stress component obtained by averaging the in-plane stress in the thickness direction, and a moment component due to a deviatoric stress obtained by subtracting the average stress component from the internal stress.

[0111] The parts produced by press molding are, for example, metal parts, and examples of materials constituting the metal parts include iron, aluminum, stainless steel, titanium, and magnesium.

[0112] The analysis device 1 may be implemented using a plurality of information processing devices communicably connected via a network, in which case each functional unit of the analysis device 1 may be distributed and implemented in the plurality of information processing devices.

[0113] The analysis device 1 may be implemented using a plurality of information processing devices communicably connected via a network. In this case, each functional unit of the analysis device 1 may be distributed and implemented in the plurality of information processing devices.

[0114] All or part of the functions of the analysis device 1 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. The program may be transmitted via an electric communication line.

[0115] The stress value σ1 is an example of a stress value. The stress value σ2 is an example of a stress value. The stress value calculated from the internal stress is an example of a stress value.

[0116] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0117] REFERENCE SIGNS LIST 1...analytical device, 11...control section, 12...input section, 13...communication section, 14...storage section, 15...output section, 91...processor, 92...memory

Claims

1. a control unit that executes an analysis process in which a part formed by pressing a steel plate is treated as an analysis object, and that calculates a stress influence degree, which is an index showing the strength of the influence of internal stress in an analysis region, which is at least a part of the analysis object, on a stress value calculated from internal stress in an evaluation portion, which is a part of the analysis object; Equipped with In the analysis process, the control unit executes a first elasticity analysis, which is an elasticity analysis including, as an initial condition, a distribution of internal stress within the analysis object at the bottom dead point of the press working, and which estimates the result of a change in the analysis object caused by the internal stress, and a second elasticity analysis, which is an elasticity analysis including, as an initial condition, a distribution of internal stress that satisfies a comparison condition that the internal stress in the analysis region has changed from the internal stress at the bottom dead point of the press working, and the internal stress outside the analysis region is the internal stress within the analysis object at the bottom dead point of the press working, and which estimates the result of a change in the analysis object caused by the internal stress that satisfies the comparison condition, the control unit further executes an influence degree acquisition process in the analysis process to acquire, as the stress influence degree, either one of a first kind value which is a value calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis and the internal stress in the evaluation portion estimated by the second elasticity analysis, and a second kind value which is a value calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis, the internal stress in the evaluation portion estimated by the second elasticity analysis, and a stress change rate α which is a rate of change in the internal stress in the analysis region under the comparison condition from the internal stress at the bottom dead center of the press working, information indicating a shape and a plate thickness of the analysis object at the bottom dead point of the press working, information indicating a distribution of strain within the analysis object at the bottom dead point of the press working, and information indicating a distribution of internal stress within the analysis object at the bottom dead point of the press working are obtained by forming analysis; Analyzer.

2. In the calculation of the stress influence degree by the control unit, the stress value is the maximum value of one of three types of stress components, namely, Mises stress, equivalent stress, or internal stress, in the evaluation portion, and the one type of stress component is any one of a maximum principal stress, a directional component stress component in an arbitrary direction, an in-plane principal stress component, an average stress component obtained by averaging the in-plane direction stress in the plate thickness direction, a moment component due to a deviatoric stress obtained by excluding the average stress component from the internal stress, a directional stress component in an arbitrary direction of the surface layer, an in-plane maximum principal stress of the surface layer, and an in-plane principal stress component of the surface layer, The internal stress in the analysis region under the comparison conditions is different from the internal stress at the bottom dead point of the press working in that at least a part of the stress components has changed, and the changing stress components are one or more of the following: a directional stress component in an arbitrary direction, an average stress component obtained by averaging the in-plane stress in the plate thickness direction, and a deviatoric stress component obtained by excluding the average stress component from the internal stress; and all components of the internal stress, and the change in the changing stress component is a change from the value of the stress component before the change to a value obtained by multiplying the stress component before the change by a value obtained by subtracting a stress change rate α, which is an arbitrary coefficient other than zero, from 1. The analytical device of claim 1 .

3. The control unit executes the analysis process for each of the plurality of analysis areas. The analytical device of claim 1 .

4. The control unit outputs, to a predetermined output destination, an image showing a contour diagram in which the stress influence degree at the plurality of evaluation portions is projected onto a shape of an analysis target as a color or a color density. The analytical device of claim 1 .

5. The evaluation portion is determined based on a stress value calculated from the zero internal stress obtained by a zero-th elastic analysis, which is an elastic analysis including, as initial conditions, the distribution of internal stress of the analysis object at the bottom dead point of the press working and the shape and plate thickness of the analysis object at the bottom dead point of the press working, and which estimates a change in the analysis object caused by the internal stress, and which obtains a zero-th internal stress, which is the internal stress in the analysis object, a strain value calculated from the strain obtained by the forming analysis, and a reference function whose independent variable is the strain value and whose objective variable is the stress value calculated from the internal stress, The part determined as the evaluation part satisfies at least the condition that the stress value at the part indicated by the zero internal stress is greater than the stress value indicated by the criterion function when the value of the independent variable of the criterion function is the strain value at the part. The analytical device of claim 1 .

6. The stress value is a maximum value of one of the von Mises stress, the equivalent stress, and the internal stress calculated from the zero internal stress in the evaluation portion, The one type of stress component is any one of a maximum principal stress, a directional stress component in an arbitrary direction, an in-plane principal stress component, an average stress component obtained by averaging the in-plane stress in the thickness direction, a moment component due to a deviatoric stress obtained by excluding the average stress component from the internal stress, a directional stress component in an arbitrary direction of the surface layer, an in-plane maximum principal stress of the surface layer, and an in-plane principal stress component of the surface layer; The strain value is calculated from the strain obtained by the forming analysis, and is the maximum value among the maximum principal strain, maximum plastic strain, strain in any direction, plastic strain in any direction, equivalent strain, equivalent plastic strain, maximum principal strain of the surface layer, maximum plastic strain of the surface layer, strain in any direction of the surface layer, and plastic strain in any direction of the surface layer, which are the maximum values ​​in the evaluation part. The analytical device according to claim 5 .

7. the control unit outputs to a predetermined output destination an image showing a graph in which a first axis represents a strain value calculated from the strain obtained in the forming analysis and a second axis represents the stress value, and the image also shows a reference function in which an independent variable is the strain value and a response variable is the stress value, and the image also shows a reference function in which an independent variable is the strain value and a response variable is the stress value, and the stress value is a maximum value of one of the Mises stress, the equivalent stress, and the internal stress calculated from the internal stress estimated by the first elasticity analysis or the second elasticity analysis in the evaluation portion, The one type of stress component is any one of a maximum principal stress, a directional stress component in an arbitrary direction, an in-plane principal stress component, an average stress component obtained by averaging the in-plane stress in the thickness direction, a moment component due to a deviatoric stress obtained by excluding the average stress component from the internal stress, a directional stress component in an arbitrary direction of the surface layer, an in-plane maximum principal stress of the surface layer, and an in-plane principal stress component of the surface layer; The strain value is calculated from the strain obtained by the forming analysis, and is the maximum value among the maximum principal strain, maximum plastic strain, strain in any direction, plastic strain in any direction, equivalent strain, equivalent plastic strain, maximum principal strain of the surface layer, maximum plastic strain of the surface layer, strain in any direction of the surface layer, and plastic strain in any direction of the surface layer, which are the maximum values ​​in the evaluation portion. The analytical device of claim 1 .

8. a control step of executing an analysis process in which a part formed by pressing a steel plate is treated as an analysis object, the analysis process calculating a stress influence degree, which is an index showing the strength of influence of internal stress in an analysis region, which is at least a part of the analysis object, on a stress value calculated from internal stress in an evaluation portion, which is a part of the analysis object; having The control step executes, in the analysis process, a first elasticity analysis which is an elasticity analysis including, as an initial condition, a distribution of internal stress within the analysis object at the bottom dead point of the press working, and which estimates the result of a change in the analysis object caused by the internal stress, and a second elasticity analysis which is an elasticity analysis including, as an initial condition, a distribution of internal stress which satisfies a comparison condition that the internal stress in the analysis region has changed from the internal stress at the bottom dead point of the press working, and the internal stress outside the analysis region is the internal stress within the analysis object at the bottom dead point of the press working, and which estimates the result of a change in the analysis object caused by the internal stress which satisfies the comparison condition, The control step further executes an influence degree acquisition process for acquiring, as the stress influence degree, either one of a first kind value which is a value calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis and the internal stress in the evaluation portion estimated by the second elasticity analysis, and a second kind value which is a value calculated from the internal stress in the evaluation portion estimated by the first elasticity analysis, the internal stress in the evaluation portion estimated by the second elasticity analysis, and a stress change rate α which is a rate of change from the internal stress at the bottom dead center of the press working of the internal stress in the analysis region under the comparison condition, in the analysis process; information indicating a shape and a plate thickness of the analysis object at the bottom dead point of the press working, information indicating a distribution of strain within the analysis object at the bottom dead point of the press working, and information indicating a distribution of internal stress within the analysis object at the bottom dead point of the press working are obtained by forming analysis; Analysis method.

9. A program for causing a computer to function as the analysis device according to any one of claims 1 to 7.

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