JP7410407B2 - Deformation resistance calculation device, deformation resistance calculation method and program - Google Patents

Description

The present invention relates to a deformation resistance calculation device, a deformation resistance calculation method, and a program.

As a method for measuring the deformation resistance of steel materials or the like by a compression test, an end face restraint compression test is known, for example, as described in Non-Patent Document 1. In the end face restraint compression test, a cylindrical test piece is used, and a conical recess is formed at the center of both end faces of the test piece. Both end surfaces of this test piece are held between a pair of jigs that have a holding surface with a conical protrusion in the center and a concentric protrusion around the convex part, and compressed in the axial direction of the test piece. . As a result, the test piece is compressed in the axial direction while the end face of the test piece is restrained from displacing in the radial direction. Non-Patent Document 1 describes a method of correcting the influence of frictional force using a predetermined calibration curve and converting the relationship between compressibility and load into the relationship between equivalent plastic strain and deformation resistance. The method using a calibration curve described in Non-Patent Document 1 is widely used as a method for measuring deformation resistance up to a high strain range because the influence of frictional force on deformation resistance can be easily quantified.

K. Oaskada, T. Kawasaki & K. Mori, "A Method of Determining Flow Stress under Forming Conditions," Ann. CIRP, 30-1 (1981), pp. 135-138.

However, when performing forming analysis by applying the deformation resistance obtained using the calibration curve described in the above-mentioned non-patent document 1 (hereinafter also referred to as "Osakata et al.'s calibration curve") to FEM, the forming load As a result of research conducted by the present inventors, it was found that there are cases where the actual value is estimated to be about 8% lower than the actual value. Furthermore, as a result of intensive study by the present inventors, the calibration curve for calculating the average equivalent plastic strain from the compressibility ratio actually depends on the work hardening index, but the calibration curve of Osakata et al. It was found that one of the causes of error was that this was not taken into consideration. For example, in order to maximize the life of a mold used for molding, it is necessary to accurately calculate the load on the mold, so there is a need to more accurately calculate the deformation resistance in an end face restraint compression test.

Therefore, an object of the present invention is to provide a deformation resistance calculation device, a deformation resistance calculation method, and a program that can improve the accuracy of deformation resistance calculated by using an end face restraint compression test.

[1] A restraint coefficient calculation unit that calculates the restraint coefficient of the test piece in the end face restraint compression test using the first polynomial approximation curve from the compressibility of the test piece measured in the end face restraint compression test, and the compression ratio of the test piece. and a strain calculation unit that calculates the average equivalent plastic strain of the test piece in the end face restraint compression test using a second polynomial approximation curve from the first work hardening index, and the load measured in the end face restraint compression test and the restraint coefficient. Determine the second work hardening index by regressing a hardening function that includes the work hardening index as a variable onto the deformation resistance curve showing the relationship between the deformation resistance of the test piece calculated using the method and the average equivalent plastic strain. If the difference between the second work hardening index and the first work hardening index is less than a threshold value, the hardening function regression unit outputs the deformation resistance curve or the regressed hardening function; A deformation resistance calculation device comprising: a difference determination unit that updates a work hardening index of 1 and causes a strain calculation unit to recalculate an average equivalent plastic strain.
[2] The second polynomial approximation curve is defined by a polynomial with the compression ratio as a variable, and an exponential function formula that defines the coefficients of the polynomial with the first work hardening index as a variable. Deformation resistance calculation device.
[3] The deformation resistance calculation device according to [1] or [2], wherein the first polynomial approximate curve includes the compression ratio as a variable and does not include the work hardening index as a variable.
[4] Calculating the restraint coefficient of the test piece in the end face restraint compression test using the first polynomial approximation curve from the compressibility of the test piece measured in the end face restraint compression test; calculating the average equivalent plastic strain of the test piece in the end face restraint compression test using a second polynomial approximation curve from the work hardening index; determining a second work hardening index by regressing a hardening function including the work hardening index as a variable on a deformation resistance curve showing the relationship between the deformation resistance of the test piece and the average equivalent plastic strain; If the difference between the work hardening index No. 2 and the first work hardening index is less than a threshold value, the deformation resistance curve or the regressed hardening function is output, and if not, the first work hardening index is updated. and re-executing the step of calculating the average equivalent plastic strain.
[5] The modification according to [4], wherein the second polynomial approximation curve is defined by a polynomial with the compression ratio as a variable and an exponential function formula that defines the coefficients of the polynomial with the first work hardening index as a variable. How to calculate resistance.
[6] The deformation resistance calculation method according to [4] or [5], wherein the first polynomial approximate curve includes the compressibility as a variable and does not include the work hardening index as a variable.
[7] A function that calculates the restraint coefficient of the test piece in the end face restraint compression test using the first polynomial approximation curve from the compressibility of the test piece measured in the end face restraint compression test, and A function that calculates the average equivalent plastic strain of a test piece in an end face restraint compression test using a second polynomial approximation curve from the work hardening index of a function of determining a second work hardening index by regressing a hardening function including the work hardening index as a variable on a deformation resistance curve showing the relationship between the deformation resistance of the test piece and the average equivalent plastic strain; If the difference between the work hardening index and the first work hardening index is less than a threshold value, output the deformation resistance curve or the regressed hardening function, otherwise update the first work hardening index. A program that enables a computer to re-execute the function of calculating the average equivalent plastic strain.
[8] The program according to [7], wherein the second polynomial approximation curve is defined by a polynomial with the compression rate as a variable and an exponential function formula that defines the coefficients of the polynomial with the first work hardening index as a variable. .
[9] The program according to [7] or [8], wherein the first polynomial approximation curve includes the compression ratio as a variable and does not include the work hardening index as a variable.

According to the above configuration, the dependence on the work hardening index is reflected in the polynomial approximation curve for calculating the average equivalent plastic strain from the compressibility in the end face restraint compression test, and the deformation resistance curve is self-consistent with respect to the work hardening index. By obtaining this, it is possible to improve the accuracy of the calculated deformation resistance.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a schematic configuration example of an end face restraint compression testing machine used in an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration example of the deformation resistance calculating device illustrated in FIG. 1; FIG. 3 is a diagram for conceptually explaining a deformation resistance calculation method in an embodiment of the present invention. It is a figure which shows the test piece used for the edge restraint compression test. FIG. 5 is a view of the test piece shown in FIG. 4 from another perspective. FIG. 3 is a diagram showing a jig used for an end face restraint compression test. 3 is a graph showing a deformation resistance curve obtained in Example 1 of the present invention. 2 is a graph showing a deformation resistance curve obtained in Comparative Example 1 of the present invention. 2 is a graph showing a deformation resistance curve obtained in Example 2 of the present invention. 2 is a graph showing a deformation resistance curve obtained in Comparative Example 2 of the present invention. It is a graph comparing the relationship between the compression ratio and load calculated by FEM analysis applying the results of Example 1 and Comparative Example 1 of the present invention with the results of actual testing. It is a graph comparing the relationship between the compression ratio and load calculated by FEM analysis applying the results of Example 1 and Comparative Example 1 of the present invention with the results of actual testing. It is a graph comparing the relationship between the compression ratio and the load calculated by FEM analysis applying the results of Example 2 and Comparative Example 2 of the present invention with the results of an actual test. It is a graph comparing the relationship between the compression ratio and the load calculated by FEM analysis applying the results of Example 2 and Comparative Example 2 of the present invention with the results of an actual test.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that, in this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals and redundant explanation will be omitted.

FIG. 1 is a diagram showing a schematic configuration example of an end face restraint compression testing machine used in an embodiment of the present invention. In the illustrated example, the end face restraint compression testing machine 1 includes jigs 11A and 11B that clamp both end faces of a cylindrical test piece 10, and actuators 12A and 12B connected to the jigs 11A and 11B, respectively. . The actuators 12A and 12B apply pressure in a direction that causes the jig 11A to approach the jig 11B, thereby compressing the test piece 10 in the axial direction. A conical concave portion 101 is formed at the center of both end faces of the test piece 10, a conical convex portion 111 is formed at the center of the clamping surfaces of the jigs 11A and 11B, and a concentric protrusion 112 is formed around the conical convex portion 111. As a result, displacement of the end face of the test piece 10 in the radial direction is restrained.

In the end face restraint compression testing machine 1 as described above, the test piece 10 is compressed in the axial direction by the actuators 12A and 12B applying pressure to the jigs 11A and 11B, respectively, according to the control signal from the control device 20. The amount of displacement of the end surface of 10 is measured using the stroke sensor 13 attached to the actuator 12A. On the other hand, the magnitude of the load applied to the test piece 10 is measured using the load sensor 14 attached to the actuator 12B. The measured displacement amount and load magnitude data are sent to the deformation resistance calculation device 30 via the control device 20. The data may be transmitted by wired or wireless communication, or the control device 20 may write the data on a recording medium, and the deformation resistance calculation device 30 may read the data from the recording medium.

FIG. 2 is a diagram showing an example of the configuration of the deformation resistance calculating device shown in FIG. 1 as an example. The deformation resistance calculation device 30 is a computer that executes various calculations according to a program, and includes a CPU (Central Processing Unit) 31, a RAM (Random Access Memory) 32, a ROM (Read Only Memory) 33, an interface 34, and a driver 35. . The deformation resistance calculation program 331 is stored in the ROM 33 of the deformation resistance calculation device 30 as in the illustrated example, or is read from a recording medium connected to the driver 35. The CPU 31 functions as a deformation resistance calculation section 311, a constraint coefficient calculation section 312, a strain calculation section 313, a hardening function regression section 314, and a difference determination section 315 by executing a deformation resistance calculation program 331. In other examples, these functions may be realized by a circuit configuration such as a PLC (Programmable Logic Controller) or an ASIC (Application Specific Integrated Circuit). The deformation resistance curve or hardening function calculated by the deformation resistance calculation device 30 may be output from a display, a printer, or the like via the interface 34.

FIG. 3 is a diagram for conceptually explaining a deformation resistance calculation method according to an embodiment of the present invention. As shown in the figure, first, an end face restraint compression test is performed using a testing machine as shown in FIG. At this time, the initial height h ₀ of the test piece and the initial diameter D ₀ of the end face of the test piece are measured before the test (step S101). In the test, the relationship between the stroke T measured by the stroke sensor 13 (or the displacement Δh or compression ratio e calculated from the stroke T as described later) and the load P measured by the load sensor 14 is recorded ( Step S102). The compression ratio e (e=(h ₀ −Δh)/h ₀ ) is calculated from the displacement amount Δh, which is obtained by correcting the effects of the testing machine rigidity and initial clearance on the stroke T. _The deformation resistance _σ is determined by _the following _formula ⁽ 1) (step S103).

Here, the constraint coefficient f is a value that changes as the deformation due to compression progresses, and in this embodiment, it is calculated from the compression ratio e using the first polynomial approximation curve shown in the following equation (2) (step S104) . Here, the coefficients B ₀ , B ₁ , B ₂ , B ₃ , B ₄ , B ₅ , B ₆ , and B ₇ are determined by discretization analysis of the end face of a test piece with known deformation resistance, as in the example described later. Conduct a restraint compression test, calculate the calibration curve for calculating the restraint coefficient f from the relationship between the compression ratio e and the load P calculated in the analysis, and regress equation (2) on the back-calculated calibration curve. determined by As a method of discretization analysis, for example, FEM (finite element method) is used. As another method of discretization analysis, for example, a finite difference method can be used. In this embodiment, the first polynomial approximation curve shown in equation (2) does not include the work hardening index n, which will be described later, as a variable. Note that in this embodiment, a seventh-order polynomial approximation curve regarding the compression ratio e as shown in equation (2) is used to calculate the constraint coefficient f, but in other embodiments, a polynomial approximation curve of the sixth order or less, or the eighth order or more is used. A polynomial approximation curve may be used.

On the other hand, in this embodiment, the average equivalent plastic strain ε￣ _p of the test piece in end face restraint compression is determined by the compression ratio e and work hardening using the second polynomial approximation curve shown in equations (3) and (4) below. It is calculated from the index n (also referred to as the first work hardening index) (step S105). Here, equation (3) is a polynomial with the compression ratio e as a variable. Equation (4) is an exponential function equation that defines the coefficients A ₀ , A ₁ , A ₂ , A ₃ , A ₄ , A ₅ , A ₆ , A ₇ of Equation (3) using the work hardening index n as a variable. . In the first calculation of the average equivalent plastic strain ε￣ _p , an appropriate initial value is set for the work hardening index n, specifically, a value of, for example, 0.05 or more and 0.35 or less. When calculating the second average equivalent plastic strain ε￣ _p based on the result of the difference determination described later, the value of the work hardening index n in the above equation is updated. Specifically, for example, the work hardening index n' obtained by hardening function regression may be used as the work hardening index n in equation (4). Alternatively, a value determined based on the relationship between the work hardening index n and the work hardening index n' (specifically, for example, an intermediate value), or another value determined regardless of the work hardening index n', The value of the work hardening index n may be updated. The coefficients C ₁ , C ₂ , and C ₃ in Equation (4) are back-calculated from the results of the end-face restraint compression test performed by discretization analysis on a test piece with known deformation resistance, as in the case of Equation (2) above. It is determined by regressing Equation (3) and Equation (4) on the calculated calibration curve. Note that in this embodiment, a seventh-order polynomial approximation curve regarding the compressibility e as shown in equation (3) is used to calculate the average equivalent plastic strain ε￣ _p , but in other embodiments, a polynomial approximation curve of the sixth order or less, or A polynomial approximation curve of order 8 or higher may be used. Furthermore, in this embodiment, the coefficient of the polynomial approximation curve in equation (3) is defined by the exponential function equation in equation (4), but instead of equation (4), other types of equations in which the work hardening index n is used as a variable may be used. The coefficients of equation (3) may be defined by equations, for example polynomials.

Using Equations (1) to (4) above, it is possible to obtain a deformation resistance curve representing the relationship between the average equivalent plastic strain ε￣ _p and deformation resistance σ￣ for each compression ratio e from the results of the end face restraint compression test. . On the other hand, a hardening function that includes a work hardening index as a variable is known as a function representing the relationship between strain and deformation resistance of a metal material. Generally, a curve obtained by regressing a hardening function on a deformation resistance curve obtained by an end face restraint compression test is used for FEM. As a hardening function, the following Swift equation (5) is exemplified. Here, the coefficient K and the offset value ε ₀ , together with the work hardening index n' (which is also referred to as the second work hardening index because it does not necessarily match the work hardening index n in equation (4)), are used to form the deformation resistance curve into the equation ( 5) is determined by regression (step S106). In addition, instead of formula (5), other hardening functions such as the n-th power hardening law (σ￣=Kε￣ _p ^n' ) or Ludwik's formula (σ￣=σ￣ ₀ +Kε￣ _p ^n' ) can also be used. good.

Furthermore, in this embodiment, the work hardening index n' (second work hardening index) determined as described above and the work hardening index n (first work hardening index) set by equation (4) are The difference is compared with the threshold value δ', and if the difference is less than the threshold value (|n'-n|≦δ'), the deformation resistance curve or the hardening function regressed to the deformation resistance curve is output and processed. (Step S107). The threshold value δ' can be set to a value of, for example, 0.002 or more and 0.01 or less. On the other hand, if the difference exceeds the threshold, the work hardening index may be processed by a method such as substituting the work hardening index n' (second work hardening index) for the work hardening index n (first work hardening index) (n=n'). The hardening index n is updated and the calculation of the average equivalent plastic strain _ε￣p is re-executed using equations (3) and (4) (step S105). For a new deformation resistance curve that expresses the relationship between the recalculated average equivalent plastic strain ε￣ _p and the deformation resistance σ￣ that has already been calculated using the constraint coefficient f, equation (5) is regressed to calculate K , ε ₀ , n' are determined (step S106). This procedure is repeated until the difference between the work hardening indices n and n' becomes equal to or less than the threshold value δ' (step S107).

In the deformation resistance calculation device 30 described above with reference to FIG. The strain calculation unit 313 calculates the average equivalent plastic strain _ε￣p described as step S105, and the hardening function regression unit 314 calculates the deformation resistance curve described as step S106. The regression of the hardening function is executed, and the difference determination unit 315 executes the termination determination of the process based on the difference in the work hardening index described as step S107.

According to the configuration of this embodiment as described above, the dependence on the work hardening index is reflected in the polynomial approximation curve for calculating the average equivalent plastic strain from the compressibility in the end face restraint compression test, and the work hardening index is By obtaining a consistent deformation resistance curve, the accuracy of the calculated deformation resistance can be improved.

An embodiment of the present invention will be described below. First, an end-face restraint compression test was performed on a specimen whose deformation resistance was known using FEM (finite element method) analysis, and from the relationship between the compression ratio e and the load P calculated by the analysis, the restraint coefficient f and the average equivalent plastic strain were determined. The calibration curve for calculating ε￣ _p was back calculated. The above equation (2) was regressed on the calibration curve of the back-calculated constraint coefficient f, and the above equations (3) and (4) were regressed on the calibration curve of the average equivalent plastic strain ε _p . In the analysis, we used Marc as a solver with the metal forming process simulation system "Simufact Forming 16.0" and created a circle with an initial diameter D ₀ of 8 mm and an initial height h ₀ of 12 mm (h ₀ /D ₀ = 1.5). Rigid-plastic analysis of a two-dimensional axisymmetric model was performed on a columnar specimen. It was assumed that the end face of the test piece and the jig were fixed, that is, the displacement of the end face in the radial direction was completely restrained, and the maximum compression stroke was 1.2 times the initial diameter D ₀ of the end face. As mentioned above, since the initial height h ₀ of the test piece is 1.5 times the initial diameter, the maximum value of the compressibility e in this case is 80%. The deformation resistance of the test piece was assumed to follow the n-th power hardening law, and was set as follows within the strain range of 0 to 10.

As a result of the above analysis and regression, as shown in Table 1 below, _the coefficients B ₀ , B ₁ , B 2 , B ₃ , B ₄ , B ₅ , B ₆ , B ₇ in equation (2), and the equation It is possible to determine the values of coefficients A ₀ , A ₁ , A ₂ , A ₃ , A ₄ , A ₅ , A ₆ , A ₇ and coefficients C ₁ , C ₂ , C ₃ in (3) and Equation (4). did it. In addition, in the example shown in Table 1, each coefficient is determined with 6 significant digits, but as a result of other experiments by the present inventors, accurate approximation is possible with 5 or more significant digits. It is possible.

Next, using carbon steel for machine structures S10C (specified in JIS G4051) as Example 1 and high carbon chromium bearing steel SUJ2 (specified in JIS G4805) as Example 2, the end faces shown in FIG. A test was conducted using a restraint compression tester, and a deformation resistance curve was determined using the deformation resistance calculation method shown in FIG. 3 using the deformation resistance calculation device shown in FIG. Further, as Comparative Examples 1 and 2, deformation resistance curves were determined from the results of the same end face restraint compression tests as in Examples 1 and 2 using the calibration curve of Osakata et al. A similar end-face restraint compression test was conducted using FEM analysis applying Swift's equation that was regressed to the deformation resistance curve obtained in each example and comparative example, and the compression ratio e and load P obtained as the analysis results were The accuracy of the calculated deformation resistance was verified by comparing the relationship between the compression ratio e and the load P during the actual test.

The shape of the test piece in the above end face restraint compression test is the same as in the above analysis. However, in the test, a jig 11 was used in which recesses 101 were formed on both end surfaces of the test piece 10 as shown in FIGS. 4 and 5, and convex portions 111 and protrusions 112 were formed as shown in FIG. Pressure was applied to both end faces of the test piece 10. Moreover, the stroke was performed within a range that did not cause cracks in the test piece. The end face restraint compression test was performed twice at strain rates of 0.01 s ⁻¹ and 10 s ⁻¹ . In order to correct the compression ratio deviation δ due to the influence of the testing machine rigidity, etc., the displacement Δh for calculating the compression ratio e was calculated from the stroke T using the following equations (6) and (7). . Here, α and β are constants, and α=0.0029 and β=0.2287.

FIGS. 7 to 10 are graphs showing deformation resistance curves obtained in Examples of the present invention and Comparative Examples, respectively. Figure 7 shows the deformation resistance curves obtained in Example 1 (S10C), Figure 8 in Comparative Example 1 (S10C), Figure 9 in Example 2 (SUJ2), and Figure 10 in Comparative Example 2 (SUJ2). (thick line) is shown together with the approximate curve (thin line) of the regressed Swift equation. As shown in each graph, in the comparative example, the slope of the deformation resistance changes in the region where the average equivalent plastic strain ε￣ _p is 1.0 to 1.5 or more, and as a result, the deformation resistance curve and the approximate curve change in this region. The discrepancy between the values has become larger (indicated by the arrow in the graph). On the other hand, in the example, the change in the slope of the deformation resistance as in the comparative example did not occur, and the deviation in value between the deformation resistance curve and the approximated curve was small. In particular, when the strain rate is 10 s ^-1 , the _deformation resistance curve and the approximated curve in both the example and the comparative example are There is a discrepancy between the values, but this is because the approximation accuracy for the deformation resistance curve is low due to the unevenness and ridges formed on the surface of the jig and test piece during the end face restraint compression test. This is thought to be due to the presence of

FIGS. 11 to 14 are graphs comparing the relationship between compressibility and load calculated by FEM analysis applying the results of the examples and comparative examples of the present invention with the results of actual tests. As mentioned above, in the FEM analysis, Swift's equation is applied which is regression on the deformation resistance curves obtained in the example and the comparative example. FIG. 11 shows Example 1 and Comparative Example 1 (S10C) at a strain rate of 0.01 s ⁻¹ , FIG. 12 shows the same case at a strain rate of 10 s ⁻¹ , and FIG. 13 shows Example 2 and Comparative Example 2 ( FIG. 14 shows the results for SUJ2) at a strain rate of 0.01 s ^-1 and at a strain rate of 10 s ^-1 . In each graph, the curve showing the load P (kN) against the compression ratio e (%) has a wide range of load P, so the FEM analysis results in the examples and comparative examples almost overlap with the actual test results. However, it is clear that the error of the load P calculated as a result of FEM analysis with respect to the load P during the actual test is smaller (closer to 0) in the example than in the comparative example. It is shown.

From the above results, the example of the present invention has higher accuracy than the case of using the calibration curve of Osakata et al. shown as a comparative example, and specifically, the error with respect to the actual test result when applied to FEM analysis is It was confirmed that a smaller deformation resistance curve could be obtained.

Although preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea stated in the claims. It is understood that these also naturally fall within the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1... End face restraint compression tester, 10... Test piece, 101... Recessed part, 11A, 11B... Jig, 111... Convex part, 112... Projection, 12A, 12B... Actuator, 13... Stroke sensor, 14... Load sensor, 20... Control device, 30... Deformation resistance calculation device, 31... CPU, 311... Deformation resistance calculation section, 312... Restraint coefficient calculation section, 313... Strain calculation section, 314... Hardening function regression section, 315... Difference determination section, 32 ...RAM, 33...ROM, 331...deformation resistance calculation program, 34...interface, 35...driver.

Claims (9)

a restraint coefficient calculation unit that calculates a restraint coefficient of the test piece in the end face restraint compression test using a first polynomial approximation curve from the compressibility of the test piece measured in the end face restraint compression test;
a strain calculation unit that calculates an average equivalent plastic strain of the test piece in the end face restraint compression test using a second polynomial approximation curve from the compression ratio and the first work hardening index;
A deformation resistance curve showing the relationship between the deformation resistance of the test piece calculated using the load measured in the end face restraint compression test and the restraint coefficient and the average equivalent plastic strain includes a work hardening index as a variable. a hardening function regression unit that determines a second work hardening index by regressing the hardening function;
If the difference between the second work hardening index and the first work hardening index is less than a threshold value, the deformation resistance curve or the regressed hardening function is output; otherwise, the first work hardening index A deformation resistance calculation device comprising: a difference determination unit that updates a work hardening index and causes the strain calculation unit to recalculate the average equivalent plastic strain. The second polynomial approximation curve is defined by a polynomial with the compression ratio as a variable, and an exponential function formula that defines a coefficient of the polynomial with the first work hardening index as a variable. Deformation resistance calculation device. The deformation resistance calculation device according to claim 1 or 2, wherein the first polynomial approximate curve includes the compression rate as a variable and does not include the work hardening index as a variable. Calculating a restraint coefficient of the test piece in the end face restraint compression test using a first polynomial approximation curve from the compressibility of the test piece measured in the end face restraint compression test;
Calculating the average equivalent plastic strain of the test piece in the end face restraint compression test using a second polynomial approximation curve from the compression ratio and the first work hardening index;
A deformation resistance curve showing the relationship between the deformation resistance of the test piece calculated using the load measured in the end face restraint compression test and the restraint coefficient and the average equivalent plastic strain includes a work hardening index as a variable. determining a second work hardening index by regressing the hardening function;
If the difference between the second work hardening index and the first work hardening index is less than a threshold value, the deformation resistance curve or the regressed hardening function is output; otherwise, the first work hardening index A method for calculating deformation resistance, comprising: updating the work hardening index and re-executing the step of calculating the average equivalent plastic strain. The second polynomial approximate curve is defined by a polynomial with the compression rate as a variable, and an exponential function formula that defines a coefficient of the polynomial with the first work hardening index as a variable. Deformation resistance calculation method. 6. The deformation resistance calculation method according to claim 4, wherein the first polynomial approximation curve includes the compression rate as a variable and does not include the work hardening index as a variable. A function of calculating a restraint coefficient of the test piece in the end face restraint compression test using a first polynomial approximation curve from the compressibility of the test piece measured in the end face restraint compression test;
A function of calculating an average equivalent plastic strain of the test piece in the end face restraint compression test using a second polynomial approximation curve from the compression ratio and the first work hardening index;
A deformation resistance curve showing the relationship between the deformation resistance of the test piece calculated using the load measured in the end face restraint compression test and the restraint coefficient and the average equivalent plastic strain includes a work hardening index as a variable. a function of determining a second work hardening index by regressing the hardening function;
If the difference between the second work hardening index and the first work hardening index is less than a threshold value, the deformation resistance curve or the regressed hardening function is output; otherwise, the first work hardening index A program for causing a computer to realize a function of updating a work hardening index and re-executing the function of calculating the average equivalent plastic strain. The second polynomial approximation curve is defined by a polynomial with the compression ratio as a variable, and an exponential function formula that defines a coefficient of the polynomial with the first work hardening index as a variable. program. 9. The program according to claim 7, wherein the first polynomial approximation curve includes the compression ratio as a variable and does not include the work hardening index as a variable.

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