JP7485956B2 - Method for calculating fracture limit line of welded part, program for calculating fracture limit line of welded part, and device for calculating fracture limit line of welded part - Google Patents

Description

The present invention relates to the calculation of the fracture limit line of a weld when simulating the strength evaluation of an arc welded joint using finite element method analysis (hereinafter sometimes referred to as "FEM analysis").

Arc welding is used as a method of joining automotive components for closed cross-section areas and chassis components where spot welding is difficult. On the other hand, FEM analysis is often used to evaluate the strength of automotive components, and it is desirable to use FEM analysis to evaluate the strength of parts joined by arc welding. However, when doing so, it is important to precisely set the fracture limit line of the weld in order to improve the accuracy of the analysis.

As a technique for precisely setting the fracture limit line of a weld, Non-Patent Document 1 discloses a technique for predicting fracture of spot welds for automotive steel sheets. By applying this technique, the fracture limit line and fracture criteria of a weld can also be obtained in the strength evaluation of arc welds. However, this technique requires a lot of manual intervention, as it is necessary to take a test piece from the weld, and then machine an ultra-small test piece with a test area of 0.3 mm from this, take the fracture reduction by a tensile test, and then perform an FEM analysis simulating this test.

Patent Document 1 also discloses a method for estimating the fracture limit line of a laser welded part using the cooling rate as a parameter from the fracture limit line of a spot welded part derived in advance. However, this method does not take into account the influence of the welding wire, which is specific to arc welded parts, and it is not possible to properly determine the fracture limit line of an arc welded part where the welding wire and steel plate are mixed.

Hideki Ueda and 3 others, "Study on Spot Weld Fracture Prediction Technology Considering Stress Triaxiality (1st Report)", Transactions of the Society of Automotive Engineers of Japan, Vol. 44, No. 2, p. 727 (2013)

JP 2017-062206 A

The present invention aims to provide a method for calculating the fracture limit line of a weld that can easily calculate the fracture limit line of a weld created by arc welding where the fracture limit line has not yet been measured. It also provides a calculation program for this purpose, and a device for calculating the fracture limit line of a weld.

Since the arc weld is produced by melting and solidifying the welding wire and the steel sheet, the fracture limit line of the arc weld is a mixture of the fracture limit line of the molten solidified structure of the welding wire and the fracture limit line of the molten solidified structure of the steel sheet (which can also be replaced with the structure of the spot weld). Therefore, the inventors came up with the idea that the fracture limit line of the arc weld can be obtained by deriving the fracture limit line of the molten solidified structure of the welding wire and the fracture limit line of the spot weld using a tensile test technique for ultra-small test pieces and mixing them at a ratio corresponding to the arc welding conditions (hereinafter sometimes referred to as the "fracture limit mixing ratio"). The arc welding conditions described here are the welding current, voltage, feed speed, and torch tilt angle, and the fracture limit mixing ratio varies depending on the arc welding conditions and the strength of the steel sheet and the welding wire.
An example of the fracture limit line when a 590 MPa class welding wire is used for a 980 class steel plate is shown in Figure 1. In Figure 1, the ◇ mark is the fracture limit line of the molten solidified structure of the steel plate, i.e., the spot weld, the ● mark is the fracture limit line of the arc weld, and the △ mark is the fracture limit line of the molten solidified structure of the welding wire.

Incidentally, it has been found that even if the arc welding conditions are the same, the fracture limit mixture ratio also changes when the strength of the welding wire is changed. For example, Fig. 2 shows an example of the fracture limit line of an arc weld using a 950 MPa class welding wire for a 980 MPa class steel plate, and compared to the case shown in Fig. 1 where a 590 MPa class welding wire is used, the fracture limit line of the arc weld approaches the fracture limit line of the molten solidified structure of the welding wire, the fracture limit mixture ratio R _A described later increases, and the fracture limit mixture ratio R _B tends to decrease slightly.
Therefore, it was thought that the fracture limit mixing ratio is affected by the strength of the welding wire, and that if the strength of the welding wire is used as a parameter, it would be possible to calculate the fracture limit line of the arc weld.

The present invention was completed based on these findings. The present invention is described below.

One aspect of the present invention is a method for calculating the fracture limit line of an arc weld, which includes an individual fracture limit line derivation process for deriving the fracture limit line of the molten solidified structure of the steel sheet, the fracture limit line of the arc weld, and the fracture limit line of the molten solidified structure of the welding wire; a fracture limit mixture ratio calculation process for calculating the fracture limit mixture ratio using the coefficient of the fracture limit line of the molten solidified structure of the steel sheet, the coefficient of the fracture limit line of the arc weld, and the coefficient of the fracture limit line of the molten solidified structure of the welding wire, and formulating the relationship between the welding wire and the fracture limit mixture ratio; and a fracture limit line calculation process for calculating the fracture limit mixture ratio from an equation formulated from the tensile strength of the welding wire used in the arc weld to be evaluated, and calculating the fracture limit line of the arc weld from the fracture limit line of the molten solidified structure of the steel sheet, the fracture limit line of the molten solidified structure of the welding wire, and the fracture limit mixture ratio.

In the above method for calculating the fracture limit line of a weld, the molten solidified structure of the steel plate may be the spot weld.

Another aspect of the present invention is a program for calculating the fracture limit line of an arc weld, the program having an individual fracture limit line derivation step for deriving the fracture limit line of the molten solidified structure of the steel sheet, the fracture limit line of the arc weld, and the fracture limit line of the molten solidified structure of the welding wire, a fracture limit mixture ratio calculation step for calculating the fracture limit mixture ratio using the coefficient of the fracture limit line of the molten solidified structure of the steel sheet, the coefficient of the fracture limit line of the arc weld, and the coefficient of the fracture limit line of the molten solidified structure of the welding wire, and formulating the relationship between the welding wire and the fracture limit mixture ratio, and a fracture limit line calculation step for calculating the fracture limit mixture ratio from an equation formulated from the tensile strength of the welding wire used in the arc weld to be evaluated, and calculating the fracture limit line of the arc weld from the fracture limit line of the molten solidified structure of the steel sheet, the fracture limit line of the molten solidified structure of the welding wire, and the fracture limit mixture ratio.

In the program for calculating the fracture limit line of a weld, the molten solidified structure of the steel plate may be regarded as a spot weld.

Another aspect of the present invention is a device for calculating the fracture limit line of an arc weld, comprising a storage means in which a program for calculating the fracture limit line of the weld is stored, a calculation means for performing calculations based on the program, and a display means for displaying the results calculated by the calculation means, and the calculation means performs calculations according to each of the steps described above.

In the present invention, the fracture limit mixing ratio is calculated in association with the welding wire, so that even in the case of calculating the fracture limit line of an arc welded part whose fracture limit line has not been measured, the fracture limit mixing ratio can be used to easily calculate the fracture limit line of the arc welded part.
That is, according to the present invention, even for welded components whose fracture limit lines have not yet been measured, the fracture limit lines of the arc welds can be calculated with high accuracy without conducting tensile tests.

FIG. 1 is a diagram showing an example of a fracture limit line when a 590 MPa class welding wire is used for a 980 class steel plate. FIG. 1 is a diagram showing an example of a fracture limit line when a 950 MPa class welding wire is used for a 980 class steel plate. FIG. 10 is a diagram showing a flow of a method S10 for calculating a fracture limit line of a weld portion. FIG. 1 is a diagram showing the relationship between the fracture limit mixture ratio and the strength of a welding wire. FIG. 1 is a diagram illustrating a configuration of a weld fracture limit line calculation device 10. 1A is an external view of the tensile test model 20, and FIG. 1B is an enlarged view of the vicinity of the welded portion. 13A shows the analysis results, and FIG. 13B shows the test results. FIG. 13 is a graph showing the maximum load of the analysis results and the test results.

[Configuration of the method S10 for calculating the fracture limit line of a welded portion]
The flow of the method S10 for calculating the fracture limit line of a weld according to one embodiment of the present invention is shown in Fig. 3. As can be seen from Fig. 3, the method S10 for calculating the fracture limit line of a weld includes an individual fracture limit line derivation process S11, a fracture limit mixture ratio calculation process S12, and a fracture limit line calculation process S13.

<Individual fracture limit line derivation process S11>
In the individual fracture limit line derivation process S11, the tensile test technique of the ultra-small test piece is used to derive the individual fracture limit lines of the molten solidified structure of the steel plate, i.e., the spot welds, the arc welds, and the molten solidified structure of the welding wire. At this time, the same material of the steel plate and the same arc welding conditions are used, and one case is sufficient for the spot welds, but the fracture limit lines of the arc welds and the molten solidified structure of the welding wire must be derived for two or more cases using different welding wires.
Here, the method of deriving the fracture limit line using the tensile test technique of the ultra-small test piece can be, for example, the method described in Non-Patent Document 1. That is, ultra-small test pieces (with a test part width of 0.3 mm) are taken from each part of the weld, HAZ (heat-affected zone), and base material by wire-cut electric discharge machining or the like, and a static tensile test is performed. The maximum equivalent plastic strain when the cross-sectional area of the test part in the FEM analysis result simulating the tensile test of the ultra-small test piece reaches the actual measured value of the fractured test piece can be defined as the local fracture strain of the test piece. Similarly, the stress triaxiality of the fracture limit can also be defined. By performing this process for each of the weld, HAZ, and base material, it is possible to derive the fracture strain and the stress triaxiality of the fracture limit at each part.

Then, as shown in formula (1), the fracture limit line can be constructed by approximating the relationship between fracture strain and stress triaxiality with a power function. Here, ε _CR represents the fracture limit strain, σ _triax represents the stress triaxiality, and A and B are coefficients. "^" means power.
ε _CR ＝A·σ _triax ^B (1)

In the individual fracture limit line derivation process S11, based on the formula (1), the fracture limit line of the molten solidified structure of at least one steel plate (i.e., the spot weld) is obtained as formula (2), the fracture limit line of the arc weld is obtained as formula (3), and the fracture limit line of the molten solidified structure of the welding wire is obtained as formula (4).
That is, when the coefficients A and B for the spot weld are A _s and B _s , the coefficients A and B for the arc weld are A _a and _Ba , and the coefficients A and B for the welding wire weld solidification structure are A _w and B _w , the individual fracture limit lines ε _CRS , ε _CRai , and ε _CRwi are expressed as shown in equations (2) to (4).
ε _CRs ＝A _s σ _triax ^B _s (2)
ε _CRai = A _s σ _triax ^ B _ai (3)
ε _CRwi = A _s σ _triax ^ _Bwi (4)
For example, if there are three types of welding wire, i takes values from 1 to 3, ε _CRai takes values from ε _CRa1 to ε _CRa3 , and ε _CRwi takes values from ε _CRw1 to ε _CRw3 .

<Fracture limit mixing ratio calculation process S12>
In fracture limit mixture ratio calculation process S12, the fracture limit mixture ratios R Ai of A and R Bi of B are calculated using formulas (5) and (6) from the coefficients A _s and B _s of the fracture limit lines of the spot welds, the coefficients A _ai and B _ai of the fracture limit lines of the arc welds, and the coefficients A _wi and B _wi of the fracture limit lines of the molten solidified structure of the welding wire, _which are obtained in individual fracture limit _{line derivation process S11. Note that R Ai and} R _Bi are the fracture limit mixture ratios of the molten solidified structure of the welding wire, and the fracture limit mixture ratios of the molten solidified structure of the steel plate, i.e., the spot welds, can be obtained by 1-R _Ai and 1-R _Bi , respectively.
R _Ai = (A _s -A _ai ) / (A _s -A _wi ) (5)
R _Bi = (B _s - B _ai ) / (B _s - B _wi ) (6)
Similar calculations are performed for the fracture limit lines of a plurality of arc welds using different welding wires. For example, when three types of welding wire are used, i- will be 1 to 3, and the fracture limit mixture ratios will be R _A1 to R _A3 and R _B1 to R _B3 .

If the fracture limit mixing ratios R _Ai and R _Bi are arranged with the welding wire strength (tensile strength) on the horizontal axis and the fracture limit mixing ratio on the vertical axis for each of the multiple individual fracture limit mixing ratios R _Ai and R Bi, a graph like the one shown in Fig. 4 can be obtained. Then, equation (7), which is the relational equation for the fracture limit mixing ratio R _A , is obtained by linear approximation between the wire strength and the multiple R Ai. Furthermore, equation (8), which is the relational equation for the fracture limit mixing ratio R _B, is obtained by linear approximation between the wire strength and the multiple R _Bi . These linear approximations can be found using a spreadsheet software.
R _A = -s _A · T _S + t _A (7)
_RB = _sB · _TS + _tB (8)
Here, the fracture limit mixing ratios RA _{and RB} are fracture limit mixing ratios associated with the strength of the welding wire. Furthermore, _TS is the tensile strength of the welding wire (welding wire strength). Furthermore, _sA and _sB are the slopes of the approximation equations, and _tA and _tB are so-called y-intercepts in the approximation equations. Usually, these have values of 0.00001 or more.

In this way, the fracture limit mixture ratio calculation process S12 can obtain a fracture limit mixture ratio associated with the strength of the welding wire from the fracture limit lines of the spot welds, arc welds, and the molten and solidified welding wire obtained in the individual fracture limit line derivation process S11.

<Fracture limit line calculation process S13>
In the fracture limit line calculation step S13, the tensile strength T _S of the welding wire used (to be used) in the arc welded portion to be evaluated is substituted into the above formulas (7) and (8) to calculate the fracture limit mixture ratios R _A and R _B.
Based on the obtained breaking limit mixing ratios R _A and R _B and formulas (5) and (6), the following formulas (9) and (10) are obtained.
_R = (A _{- A} ) / (A _{- A} ) (9)
_RB = (Bs _- B _a ) / (Bs _- B _w ) (10)

By modifying this, equations (11) and (12) are obtained.
A _a = A _w · R _A + A _s · (1 - R _A ) (11)
B _a = B _w · R _B + B _s · (1 - R _B ) (12)
As a result, the coefficients A and B of the formula (1) that express the fracture limit line of the arc weld to be evaluated could be obtained as coefficients A _a and _Ba .

Then, by substituting A _a for A and B _a for B in formula (1), the fracture limit line ε _CRa of the arc weld can be obtained, as given by the following formula (13).
ε _CRa = {A _w · R _A + A _s · (1 - R _A )} · σ _triax ^ {B _w · R _B + B _s · (1 - R _B )} (13)
As can be seen from equation (13), the fracture limit line of an arbitrary arc weld can be obtained from the coefficients A _s and B _s of the fracture limit line of a known spot weld and the coefficients A _w and B _w of the fracture limit line of the known molten solidified structure of the welding wire.

[Effects, etc.]
As described above, in the present invention, the fracture limit mixing ratio is calculated based on the tensile strength of the welding wire. As a result, even when performing FEM analysis for strength evaluation on an arc welded portion whose fracture limit line has not been measured, if the tensile strength of the welding wire is specified and the fracture limit lines of the molten solidified structure of the steel sheet, i.e., the spot welded portion and the molten solidified structure of the welding wire, have been measured, the fracture limit mixing ratio can be used to easily calculate and predict the fracture limit line of the arc welded portion.
According to the present invention, it is possible to accurately calculate the fracture limit line of an arc weld without performing a tensile test, even for a member made of a welding wire whose fracture limit line of an arc weld has not yet been measured.

[Break Limit Line Calculation Device 10]
5 is a conceptual diagram showing the configuration of a weld fracture limit line calculation device 10 according to one embodiment that specifically performs calculations according to the above-mentioned arc weld fracture limit line calculation method S10. The weld fracture limit line calculation device 10 has an input means 11, a calculation device 12, and a display means 18. The calculation device 12 has a calculation means 13, a RAM 14, a storage means 15, a receiving means 16, and an output means 17. The input means 11 also includes a keyboard 11a, a mouse 11b, and an external storage device 11c that functions as one of the storage media.

The calculation means 13 is composed of a so-called CPU (central processor), and is connected to each of the above-mentioned components and is capable of controlling them. The calculation means 13 also executes various programs 15a stored in the storage means 15, which functions as a storage medium, and performs calculations based on these programs as a means for generating data for each process of the above-mentioned weld fracture limit line calculation method S10 and selecting data from a database.

RAM 14 is a component that functions as a working area for the calculation means 13 and a temporary data storage means. RAM 14 can be composed of SRAM, DRAM, flash memory, etc., and is similar to known RAM.

The storage means 15 is a member that functions as a storage medium in which programs and data that are the basis for various calculations are stored. The storage means 15 may also be capable of storing various intermediate and final results obtained by executing the programs. More specifically, the storage means 15 stores (stores) programs. Other information may also be stored therein.

The stored programs include programs that are the basis for calculating each process of the above-mentioned method S10 for calculating the fracture limit line of a welded part. That is, the programs include an individual fracture limit line derivation step, a fracture limit mixture ratio calculation step, and a fracture limit line calculation step, so as to correspond to each process of the method S10 for calculating the fracture limit line of a welded part shown in FIG. 3. The specific calculation contents of this program are as described in the above-mentioned method S10 for calculating the fracture limit line of a welded part.

More specifically, in the individual fracture limit line derivation step, the test results of the tensile test of the micro-test piece are input and the formulas (2) to (4) are calculated.
In the step of calculating the breaking limit mixing ratio, the formulas (5) to (8) are calculated based on the obtained formulas (2) to (4). At this time, a spreadsheet software incorporated in the breaking limit line calculation device 10 as a program may be used.
In the fracture limit line calculation step, the fracture limit mixture ratio obtained in the fracture limit mixture ratio calculation step is used to obtain equations (11) and (12), making it possible to calculate the fracture limit line of any arc weld.

The receiving means 16 is a component that has the function of appropriately inputting information from the outside into the computing device 12, and is connected to the input means 11. This also includes so-called input ports, input connectors, etc.

The output means 17 is a component that has the function of appropriately outputting information that should be output from among the obtained results to the outside, and is connected to a display means 18 such as a monitor and various devices. This also includes so-called output ports, output connectors, etc.

The input device 11 includes, for example, a keyboard 11a, a mouse 11b, an external storage device 11c, etc. The keyboard 11a and the mouse 11b may be well-known devices, and therefore a description thereof will be omitted.
The external storage device 11c is a known storage means that can be connected externally and also functions as a storage medium. There is no particular limitation on the storage means, and various programs and data required can be stored here. For example, the same programs and data as those in the storage means 15 described above may be stored here.
The external storage device 11c may be a known device, such as a CD-ROM and a CD-ROM drive, a DVD and a DVD drive, a hard disk, or various types of memory.

In addition, information may be provided to the computing device via the receiving means 16 via a network or communication. Similarly, information may be transmitted to an external device via the output means 17 via a network or communication.

Such a weld fracture limit line calculation device 10 makes it possible to efficiently and accurately perform the above-described method S10 for calculating the fracture limit line of a weld by arc welding. A computer, for example, can be used as such a weld fracture limit line calculation device 10.

The following describes in more detail the method for calculating the fracture limit line of a weld using an example. This example is based on the method S10 for calculating the fracture limit line of a weld.

[Calculation of the breaking limit line]
<Individual fracture limit line derivation process S11>
In the individual fracture limit line derivation step S11, each fracture limit line was derived as follows.
The steel plate to be evaluated was of 980 MPa class, and the fracture limit line (ε _CRs ) of the spot weld was obtained by the formula (2).
Next, the fracture limit lines (ε _CRw1 to ε _CRw3 ) of the molten solidified structures of the welding wires were determined for each of the 590 MPa class, 780 MPa class, and 950 MPa class welding wires by formula (4).
In the arc welding, the welding conditions were welding current = 120 A, voltage = 22 V, feed rate = 0.95 m/min, and torch tilt angle = 60°, and three types of welding wires, 590 MPa class, 780 MPa class, and 950 MPa class, were used, and the fracture limit lines (ε _CRa1 to ε _CRa3 ) of the arc welded portion were calculated using formula (3).

<Fracture limit mixing ratio calculation step S12>
In the fracture limit mixture ratio calculation process S12, fracture limit mixture ratios R _Ai and R _Bi for the 590 MPa class, 780 MPa class, and 950 MPa class welding wires were calculated from formulas (5) and (6). That is, fracture limit mixture ratios R _A1 and R _B1 for the 590 MPa class welding wire, fracture limit mixture ratios R _A2 and R _B for the 780 MPa class welding wire, and individual fracture limit mixture ratios R _A3 and R _B3 for the 950 MPa class welding wire conditions were calculated.

Next, using a spreadsheet software, the coefficients of approximation formula (7) and approximation formula (8) were calculated as s _A =0.0007, t _A =0.9333, s _B =0.0001, and t _B =0.5868. That is, the following formula was obtained.
R _A = -0.0007 · T _S +0.9333
R _B = 0.0001 · T _S + 0.5868

In the fracture limit line calculation step S13, the fracture limit line of the arc welded portion using a 490 MPa class welding wire was calculated. To this end, the tensile strength T _S of the welding wire was substituted into the formulas (7) and (8) to calculate the fracture limit mixture ratios R _A and R _B.
Next, the coefficients A _a and B _a of the fracture limit line of the arc welded portion using a 490 MPa class welding wire were calculated from equations (11) and (12), and the fracture limit line was obtained from these values using equation (13) (equation (1)).
ε _CRa = 0.46 · σ _triax ^ - 0.77

[verification]
The fracture limit line of the arc welded portion obtained above (ε _CRa = 0.46·σ _triax ^-0.77) was applied to a tensile test FEM analysis model of an arc welded joint to verify accuracy. Figure 6 shows a tensile test analysis model 20 of a lap fillet welded joint. Figure 6(a) shows the entire model, and Figure 6(b) shows an enlarged view of the vicinity of an arc welded portion 21. The fracture limit line obtained above (ε _CRa = 0.46·σ _triax ^-0.77) was set for this arc welded portion 21.

The tensile test analysis model 20 is modeled in a symmetrical shape in the plate width direction of 1/2. Existing fracture limit lines were also set for the heat-affected zone 22 and base material zone 23. The entire model had a Young's modulus of 206 GPa and a Poisson's ratio of 0.3, and each part (arc welded zone 21, heat-affected zone 22, base material zone 23) had a corresponding fracture limit line. One end 24 of the steel plate was fully restrained, and a tensile load was applied to the other end 25.

Figure 7 shows the fracture location of the analysis result (a) and the tensile test result (b) under the same conditions. In this analysis, the elements that reached the fracture limit line were deleted to reproduce the loss of rigidity due to fracture, and the fracture location of the analysis result matched that of the test result.
The maximum load of the tensile test results under the same conditions as the analysis results is shown in Figure 8. The analysis results correspond well to the test results, and it was found that according to the present invention, even for welding wires whose fracture limit lines of arc welds have not been measured, the fracture limit lines can be calculated with high accuracy without using the tensile test technique for ultra-small test pieces.

REFERENCE SIGNS LIST 10 Weld fracture limit line calculation device 11 Input means 12 Calculation device 18 Display means 20 Tensile test analysis model 21 Arc weld 22 Heat-affected zone 23 Base metal S10 Weld fracture limit line calculation method S11 Fracture limit line derivation process S12 Fracture limit mixture ratio calculation method S13 Fracture limit line calculation process

Claims (5)

A method for calculating a fracture limit line of an arc weld to be evaluated, comprising the steps of :
An individual fracture limit line derivation process for deriving a fracture limit line of a molten solidified structure of a steel plate, a fracture limit line of an arc weld, and a fracture limit line of a molten solidified structure of a welding wire;
a fracture limit mixture ratio calculation process for calculating a fracture limit mixture ratio by using a coefficient of a fracture limit line of a molten solidified structure of the steel plate, a coefficient of a fracture limit line of the arc welded portion, and a coefficient of a fracture limit line of a molten solidified structure of the welding wire, and formulating a relationship between the welding wire and the fracture limit mixture ratio;
a fracture limit line calculation process for calculating a fracture limit mixture ratio from the tensile strength of a welding wire used in the arc welded portion to be evaluated by the formulated formula, and calculating a fracture limit line of the molten solidified structure of the steel plate, a fracture limit line of the molten solidified structure of the welding wire, and a fracture limit line of the arc welded portion to be evaluated from the fracture limit mixture ratio;
A method for calculating the fracture limit line of a weld having the following structure. The fracture limit line calculation method according to claim 1, in which the molten solidified structure of the steel plate is a spot weld. A program for calculating a fracture limit line of an arc weld to be evaluated ,
An individual fracture limit line deriving step of deriving a fracture limit line of a molten solidified structure of a steel plate, a fracture limit line of an arc weld, and a fracture limit line of a molten solidified structure of a welding wire;
a fracture limit mixture ratio calculation step of calculating a fracture limit mixture ratio by using a coefficient of a fracture limit line of a molten solidified structure of the steel plate, a coefficient of a fracture limit line of the arc welded portion, and a coefficient of a fracture limit line of a molten solidified structure of the welding wire, and formulating a relationship between the welding wire and the fracture limit mixture ratio;
a fracture limit line calculation step of calculating a fracture limit mixture ratio from the tensile strength of a welding wire used in the arc welded portion to be evaluated by the formulated formula, and calculating a fracture limit line of the molten solidified structure of the steel plate, a fracture limit line of the molten solidified structure of the welding wire, and a fracture limit line of the arc welded portion to be evaluated from the fracture limit mixture ratio;
A program for calculating the fracture limit line of a weld having the above structure. The fracture limit line calculation program according to claim 3, wherein the molten solidified structure of the steel plate is a spot weld. An apparatus for calculating a fracture limit line of an arc weld to be evaluated ,
A storage means for storing the weld fracture limit line calculation program according to claim 3 or 4;
A calculation means for performing calculations based on the program;
A display means for displaying the result calculated by the calculation means,
The calculation means performs calculations according to the steps of claim 3 or 4.

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