KR101993545B1 - Evaluation method of forming shear edge - Google Patents

Abstract

The object of the present invention is to provide a technique for evaluating the moldability of a material edge shearing after molding with higher accuracy. EXAMPLE By a hole expansion test on a metal plate after molding, a plurality of pieces of data of strain amount equivalent to the strain limit with respect to the strain gradient is obtained by changing the strain gradient at the shearing edge, and a plurality of pieces of data of the strain amount equivalent strain amount The strain flange deformation limit equivalent strain is obtained. From the found relationship, the forming margin of the shearing edge with respect to the metal plate subjected to the preliminary deformation by the preforming is evaluated from the forming limit line L and the formable region R of the front edge.

Description

Evaluation method of forming shear edge

The present invention relates to a technique for evaluating moldability of a material edge sheared after primary molding. For example, the present invention relates to a technique for evaluating moldability in FEM simulation at a leading edge of an automotive press product or the like.

As a method for evaluating a molded part after a deformation state in the vicinity of a shearing edge having a large degree of influence on the deformation limit at the front end edge of the press product, there is a determination method described in, for example, Patent Documents 1 to 3.

However, all of the forming ability judging methods at the front edge of the above-mentioned press product are for evaluating the material edge sheared without subjected to the preliminary deformation (primary molding), and for the application to the material edge sheared after the preliminary deformation, Not considered.

As described above, there is a problem in the accuracy of determination of moldability at the shearing edge after the primary molding has been done in the past, and there has been a problem that molding ability is unclear unless the mold is manufactured.

Patent Document 1: Japanese Patent Publication No. 4935713 Patent Document 2: Japanese Patent Publication No. 5561203 Patent Document 3: Japanese Patent Publication No. 5472518

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a technique for more accurately evaluating the forming ability of a material edge sheared after molding.

In order to solve the problem, one aspect of the present invention is an evaluation method for evaluating the possibility of forming a shearing edge by press forming on a metal plate subjected to preliminary deformation by the preliminary forming, The deformation limit at the front edge is obtained, and the deformation limit at the found shear edge is expressed as the deformation limit equivalent strain amount, and the deformation amount equivalent to the deformation limit equivalent to the deformation degree at the shear edge in the radial direction A plurality of pieces of data having different distortion gradients are obtained as data on the metal plate after the preforming, and a substantial amount of distortion applied to the metal plate in the preforming is defined as a pre-deformation equivalent distortion amount, Is defined as a strain equivalent to the extension flange deformation limit, and in the above example Based on the shape-equivalent strain amount and the plurality of pieces of data, a relationship of a distortion equivalent to the extension flange deformation limit with respect to the distortion gradient is obtained, and the formable region of the front edge is specified from the obtained relationship, And evaluating the forming ability of the shearing edge with respect to the metal plate.

According to one aspect of the present invention, it is possible to more easily evaluate the moldability of the material edge of the metal sheet sheared after the molding in the molded article formed through primary molding (e.g., molding) and secondary molding.

That is, evaluation of moldability and forming allowance at the extension flange portion in the secondary molding can be predicted with high precision without preparing the mold several times, and as a result, defects due to cracking can be prevented early .

Fig. 1 is a diagram showing the relationship between the strain equivalent strain and the secondary strain limit strain when the strain gradient in Experiment 1 is large. Fig.
Fig. 2 is a diagram showing the relationship between the strain equivalent to the strain in the case where the distortion gradient in Experiment 1 is large and the total deformation amount.
3 is a diagram showing the relationship between the strain equivalent strain and the secondary strain minimum strain when the distortion gradient in Experiment 1 is small.
4 is a graph showing the relationship between the strain equivalent to the strain in the case where the distortion gradient in Experiment 1 is small and the total deformation amount.
5 is a graph showing the relationship between the distortion equivalent to the example strain and the distortion of the secondary strain limit in the case where the distortion gradient in Experiment 2 is large.
6 is a graph showing the relationship between the strain equivalent to the strain in the case where the distortion gradient in Experiment 2 is large and the total deformation amount.
7 is a diagram showing the relationship between the strain equivalent strain and the secondary strain limit strain in the case where the distortion gradient in Experiment 2 is small.
8 is a diagram showing the relationship between the strain equivalent to the strain in the case where the distortion gradient in Experiment 2 is small and the total deformation amount.
9 is a diagram showing the relationship between the distortion equivalent to the example strain and the distortion of the secondary strain limit in the case where the distortion gradient in Experiment 3 is large.
10 is a graph showing the relationship between strain equivalent to the strain in the case where the distortion gradient in Experiment 3 is large and the total deformation amount.
11 is a diagram showing the relationship between the strain equivalent strain and the secondary strain minimum strain when the distortion gradient in Experiment 3 is small.
12 is a diagram showing the relationship between the strain equivalent to the strain in the case where the distortion gradient in Experiment 3 is small and the total deformation amount.
Fig. 13 is a view for explaining a processing step according to the first embodiment based on the present invention. Fig.
Fig. 14 is a view for explaining a molding limit line and a moldable area according to the first embodiment of the present invention. Fig.
Fig. 15 is a view for explaining a molding limit line and a moldable area according to a modified example of the present invention. Fig.
16 is a view for explaining a processing step according to the second embodiment based on the present invention.
Fig. 17 is a view for explaining a molding limit line and a moldable area according to the second embodiment of the present invention. Fig.

(Knowledge leading to the present invention)

The evaluation of the method of determining whether or not the shear edge can be formed by the above-described conventional technique is based on the assumption that only the deformation limit of the shear edge from the state of not receiving the pre-deformation (primary molding) is assumed. For this reason, it is not clear whether the above-described evaluation method of the prior art can be directly developed by the judgment of the moldability of the shearing edge after the primary molding. This is because it can not be asserted that the damage caused by shearing does not depend on the amount of primary deformation caused by preform formation.

Then, the inventor conducted a detailed investigation to clarify quantitatively the influence of the amount of primary strain (primary strain) on the deformation limit in the secondary molding.

Hereinafter, the contents thereof will be described.

Here, using the specimens A to E shown in Table 1, various hole enlargement tests were conducted on the metal plate subjected to primary molding (pre-strain). As the hole enlargement test, a cone hole enlargement test using a conical punch and a cylindrical hole enlargement test using a cylindrical punch were performed.

[Table 1]

In the above-described hole expansion test, after a metal plate as a target is subjected to primary shaping in a truncated cone shape, a portion serving as a sample is cut around the upper surface of the truncated cone, and the cut sample is planarized. Thereafter, a hole is formed in the center of the sample, and a hole is enlarged in the hole by a punch. The conical punch used was a 60 degree conical punch, and the cylindrical punch was a cylindrical punch having a diameter of 50 mm.

Further, the distortion gradient in the radial direction can be adjusted by changing the shape of the punch to be used or the diameter of the extraction hole after molding.

<Experiment 1>

The conical hole enlargement test was conducted on the metal plate made of the specimen A.

Example of distortion due to preliminary deformation by preliminary molding As a result of summarizing the secondary deformation limit distortion of the metal plate after molding, the results shown in Fig. 1 were obtained. The results shown in Fig. 2 were obtained as a result of summarizing the total deformation amount, which is the sum of the equivalent deformation equivalent strain and the secondary deformation limiting strain, against the equivalent deformation equivalent strain by the preforming.

Next, a cylindrical hole enlargement test was conducted on the metal plate made of the specimen A.

The results are shown in Fig. 3 as a result of summarizing the secondary strain limit strain on the metal plate after the molding for the example strain equivalent strain by the preforming. The result shown in Fig. 4 was obtained by summarizing the total strain amount, which is the sum of the strain equivalent strain and the secondary strain limit strain with respect to the strain equivalent to the example strain by the preforming.

In the drawings,

○: Distortion due to the axis of the back

□: Distortion due to axis

Δ: Distortion due to plane distortion

to be.

When the cone hole enlargement is carried out, the distortion gradient at the front edge becomes larger as compared with the case of enlarging the cylindrical hole.

Therefore, as shown in Fig. 1, when the distortion gradient is large in the disclosure material A, the secondary strain limit strain becomes smaller as the strain equivalent strain increases, but as can be seen from Fig. 2, As the amount of significant distortion increases.

On the other hand, in the case where the distortion gradient at the front edge is small, as can be seen from Fig. 3, the secondary strain limit distortion becomes smaller as the amount of strain equivalent strain increases. However, as can be seen from Fig. 4, It does not depend much on the amount of significant distortion and has a low correlation with the amount of strain equivalent strain.

As can be seen from Figs. 1 to 4, the influence of the strain amount equivalent to the example strain (the amount of strain, the amount of primary strain) on the secondary strain limit strain does not depend much on the strain form of the strain. Therefore, it was found that the secondary strain limit distortion can be sorted into significant distortions.

<Experiment 2>

The same experiment as in Experiment 1 was carried out for Dispersion D. The results are shown in Figs. 5 to 8. Fig.

As can be seen from FIGS. 5 to 8, this disclosure item D also has a tendency similar to that of the disclosure item A.

<Experiment 3>

The same test as in Experiment 1 was carried out for Dispersion E. The results are shown in Figs.

As can be seen from Figs. 9 to 12, even in the case of the disclosure material E, there is a tendency similar to that of the disclosure material A, but there is also the following tendency.

That is, when the distortion gradient is large, the secondary deformation limit does not substantially decrease due to the pre-deformation amount in the predetermined deformation area. On the other hand, when the distortion gradient is small, the total deformation amount is dependent on the amount of the deformation, and decreases with the increase of the deformation amount. In other words, it is adversely affected to give the example strain.

<Summary of experimental results>

The same tests as in Experiment 1 were also conducted on the disclosures B and C.

The results are summarized in the ratio of the amount of deformation (amount of deformation of the deformation limit amount in the secondary molding) to the amount of deformation (equivalent deformation amount equivalent to deformation) in Table 2.

[Table 2]

As can be seen from Table 2, it can be seen that when the distortion gradient is large as compared with the case where the distortion gradient is small, the amount of forming allowance (molding allowance) with respect to the metal plate after preforming may be underestimated. In addition, it can be seen that there is a possibility that unnecessary frame correction may occur when the amount is underestimated.

<Knowledge>

From the above experiments, the inventors obtained the following findings.

(1) The degree of influence of the primary strain on the deformation limit strain after shearing does not depend much on the deformation form of the deformation limit strain after shearing (such as the axis, the uniaxial axis, and the plane strain).

Therefore, in the present invention, evaluation is made with considerable distortion.

(2) When the distortion gradient is large, the influence of the primary strain on the strain limit strain of only the secondary strain is small. Therefore, the deformation limit of the final material edge including the distortion in the primary deformation increases with the increase of the primary deformation amount. On the other hand, when the distortion gradient is small, the deformation limit of the final material edge is not changed or greatly decreased as the deformation limit strain of the secondary deformation only increases with the increase of the primary deformation amount.

That is, the final deformation limit distortion of the extension flange portion by secondary forming including the pre-deformation is dependent on both the primary deformation amount and the distortion gradient.

In addition, the dependency of the primary strain is different between a case where the distortion gradient is large and a case where the distortion gradient is small. That is, the evaluation accuracy is improved by evaluating the shearing edge by dividing the case where the distortion gradient is small and the case where the distortion gradient is large, for a predetermined distortion gradient. Also, this tendency does not depend on the thickness.

The present invention has been made based on the new knowledge as described above.

Hereinafter, each embodiment based on this finding will be described.

(First Embodiment)

Next, a method for evaluating the forming ability of the front edge of the present embodiment will be described with reference to the drawings.

The method for evaluating the forming ability of the front end edge of the present embodiment is a technique for evaluating the forming ability of the shearing edge with respect to the primary formed (preformed) metal plate.

<Configuration>

As shown in Fig. 13, the moldability evaluating method according to the present embodiment is characterized in that the test data acquiring step (1), the pre-strain equivalent amount setting step (2), the moldable area specifying step (3) 4) and an allowance judging step (5).

In the experimental data acquisition step (1), the hole enlargement test is performed on the metal plate subjected to the preliminarily set example forming. In the hole enlargement test, two or more kinds of hole expanding tests having different radial distortion grades at the front edge are performed by changing the diameter of the punch shape used or the diameter of the cutout hole before the enlargement.

The hole expanding test for the metal plate subjected to the preforming and preforming to obtain the data may be carried out by the method described in Experiment 1 above. In this case, it is easy to perform primary molding so that a considerable amount of distortion due to preforming is applied to a place where hole enlargement is carried out.

Here, the distortion gradient of the hole after the diameter enlargement by the hole enlargement test is specified by the analysis of the molded product by the test or the molding analysis (FEM analysis calculation) performed separately. Further, from the hole enlargement ratio by the hole enlargement test, the deformation limit strain amount generated at the front edge of each hole by the secondary molding is found. In this embodiment, the deformation limit equivalent distortion amount is adopted as the deformation limit distortion amount to be acquired.

The hole enlargement ratio [lambda] can be expressed by the following equation when the minus hole diameter is d0 and the hole diameter after diameter enlargement is d.

? = ((d-d0) / d0) x100

In the present embodiment, the distortion gradient is expressed as an average gradient of the maximum principal distortion in a predetermined section along the radial direction from the edge of the hole (for example, a section from edge to 5 mm). In the present embodiment, the value of the distortion gradient is represented by an absolute value.

By the above processing, the experimental data acquisition step (1) acquires a plurality of pieces of data having different distortion gradients as data consisting of a distortion gradient in the diametrical direction at the front edge and a distortion amount equivalent to the distortion limit in the metal plate after the preliminary molding . The location to acquire is specified by the user.

The example strain equivalent strain amount setting step (2) is a step of setting the strain equivalent strain amount setting step (2) in the part subjected to hole enlargement test by the preformed molded article or a separately performed molding analysis (FEM analysis calculation) And the equivalent distortion amount is acquired as the example distortion-equivalent distortion amount. The strain equivalent strain amount may be obtained by setting the acquisition or primary machining conditions at the hole enlargement test.

The moldable region specifying step 3 is a step for obtaining a plurality of pieces of data having different distortion gradients acquired by the experiment data acquiring step 1 and a plurality of pieces of data having different height gradients Obtain the relationship of the distortion equivalent to the flange deformation limit.

Here, the stretch flange strain limit equivalent distortion is the sum of the distortion limit equivalent strain amount and the example strain equivalent distortion amount. That is, the strain equivalent strain amount obtained in the strain correcting equivalent strain amount setting step (2) is added to the strain amount equivalent strain amount obtained in the experiment data obtaining step (1), and this strain amount is added to the stretch flange strain limit.

As a result, two or more pieces of data can be obtained as data for relation generation, in which two parameters, i.e., a distortion gradient and a stretch flange distortion limit equivalent distortion, are set as parameters (variables).

Then, as shown in Fig. 14, data of a plurality of (distortion gradient, strain equivalent to the stretch flange deformation limit) obtained by taking a distortion gradient on the abscissa and a distortion equivalent to the strain flange deformation limit on the ordinate axis are plotted, Let the line be the forming limit L. Then, with the forming limit line L as a boundary, the lower region thereof is specified as the formable region R. [

Here, if the data to be acquired is data of two points, as shown in Fig. 14, a straight line passing through the two points is defined as a molding limit line L. [ In this case, for example, it is preferable that the distortion gradient of one data is less than 0.03 and the distortion gradient of the other data is 0.06 or more. Alternatively, if the range of the distortion gradient likely to occur in the secondary molding is determined, two pieces of data having a distortion gradient in the range may be employed. In either case, it is preferable that the distances between the two points are at least 0.03 apart.

It is preferable that the data to be acquired is three data or more. In this case, it is preferable that the data include three data of a distortion gradient of 0.03 or less, a distortion gradient of 0.06 or more, and a data of 0.03 or more and less than 0.06. By doing so, it is possible to obtain the molding limit line L by taking into consideration the difference in tendency between the case of a large distortion gradient and the case of a small distortion gradient.

When the data to be plotted is three points or more, a line connecting each adjacent point with a straight line is defined as a molding limit line L. A curve passing through the plurality of data is defined as a molding limit line L.

Here, the molding limit line L obtained in the moldable region specifying step (3) may be obtained as a relational expression using a parameter (distortion gradient, distortion equivalent to extension flange deformation limit) as a parameter.

The formable region specifying step 3 is a step of inputting data of a plurality of pieces of data having different distortion gradients acquired by the experiment data acquiring step 1 and data of the equivalent strain equivalent amount obtained by the preliminary strain equivalent amount setting step 2 , The calculation of the processing is executed by a computer, and at least one of the forming limit line L and the formable region R is output and generated. The molding limit line L may be expressed by the formula, and the coefficient of the formula may be stored.

Here, the calculation processing portion other than the hole enlargement test in the experimental data acquisition step (1) may be executed in a computer using a program such as FEM analysis calculation.

With the above process, the acquisition of the basic information for evaluating the forming possibility of the shearing edge by the press forming on the metal plate subjected to the preliminary deformation by the preforming is completed.

In the molding specification data acquisition step (4), the molding specifications of the molded products produced in at least two steps of the primary molding and the secondary molding are preliminarily tentatively subjected to the FEM analysis calculation for the preliminary molding specification, The deformation amount and the distortion gradient of the shearing edge after the completion of the molding are found and the amount of distortion equivalent to the pre-deformation equivalent strain is calculated by the preliminary molding in the vicinity of the shearing edge. In this molding specification data acquisition step (4), the FEM analysis calculation may be added, and the data may be acquired by carrying out experiments as appropriate.

Here, in the molding specification of the molded product, the magnitude of the distortion corresponding to the preliminary deformation differs depending on the shape imparted to the preliminary molding, and is often different depending on the position of the stretch flange. Therefore, . In the case where the width of the distortion corresponding to the preliminary strain generated at each shearing edge at the time of molding is small, the representative value may be employed.

In the impossibility judgment step (5), the deformation amount of the total at the shearing edge after completion of molding, which is obtained in the molding specification data acquisition step (4), is output as a significant amount of distortion at the molding possibility judgment target site. Then, it is determined whether or not the data set of the total deformation amount and the distortion gradient exists in the formable region R specified by the output information of the forming possible region specifying step (3). In the case where it is present in the moldable region R, it is evaluated as moldable. Otherwise, it is evaluated that molding is impossible. The evaluation may be performed automatically by a computer. Then, the evaluation is displayed on the display section 6.

Here, the acquired data for the evaluation of the shearing edge in the provisional molding specification is not limited to one place, but may be obtained at a plurality of places on the leading edge, and evaluation of the above molding may be carried out.

If there is a non-forming shear edge, provisional molding specifications (eg, molding specifications and example molding specifications) obtained by changing the specification near the front edge of the mold can not be formed are re- The acquisition step (4) and the necessity determination step (5) are repeated. Then, the final shaping specification for the preformed metal sheet is determined from the provisional shaping specifications that can be formed at all of the set shear edge positions.

Here, the forming limit line L may be determined for each steel type of the metal plate to be used.

In the above-described molding evaluation, the determination as to whether or not an abutment has been made is exemplified.

&Lt; Effect of the present embodiment &

The present embodiment has the following effects.

(1) Example of distortion gradient at the shearing edge A plurality of data of the distortion limit equivalent to the deformation limit in the metal plate after molding is acquired, and based on the plurality of data, the relationship of the distortion equivalent to the expansion flange deformation limit And specifies the forming limit line L from the obtained relationship, thereby specifying the formable region R of the front edge. Based on the specific forming limit line L and the formable region R, the moldability is evaluated with respect to the total deformation amount against the distortion gradient at the shearing edge obtained from the provisional molding specification.

According to this configuration, it is possible to more easily evaluate the moldability of the material edge of the metal plate sheared after the preforming in the molded product formed through primary molding (preforming) and secondary molding.

That is, evaluation of moldability and forming allowance at the extension flange portion in the secondary molding can be predicted with high precision without preparing the mold several times, and as a result, defects due to cracking can be prevented early .

In addition, by evaluating the distortion considerably, it is not necessary to consider the difference in distortion type.

<Modifications>

Here, the case of obtaining one continuous forming limit line L is described in the above embodiment. On the other hand, in this modification, the distortion gradient of the reference is set within the reference distortion gradient range of the distortion gradient of 0.03 or more and 0.06 or less, the distortion gradient of the reference is divided into two regions, and the molding limit lines L1 and L2 .

Here, as confirmed by the inventor, the stretch flange distortion limit equivalent distortion, which is the sum of the strain limit equivalent strain amount and the example strain equivalent distortion amount, is not much dependent on the magnitude of the strain equivalent strain amount when the distortion gradient is small. On the other hand, when the distortion gradient is large, the distortion equivalent to the expansion flange deformation limit tends to increase with the increase of the distortion equivalent strain. As a result of confirming the existence of the boundary between the two distortion gradients, the inventor confirmed that the boundary exists between 0.03 and 0.06, so that the reference distortion gradient range was 0.03 or more and 0.06 or less. And preferably 0.04 or more and 0.05 or less.

For example, in a variety of automobile press products, the distortion gradient of the portion where the elongation flange molding is judged to be a problem in the secondary molding was investigated, and it was largely divided into 0.03 or more and 0.06 or more.

In most cases, depending on the hole diameter, the distortion gradient is 0.06 or more in the cone hole enlargement test and the distortion gradient is 0.03 or less in the cylindrical hole expansion test.

From the above, the distortion gradient of the reference as the boundary is defined as the above range.

The evaluation method in this modified example will be described in detail.

First, a reference distortion gradient is selected from a reference distortion gradient range of 0.03 or more and 0.06 or less. In the present embodiment, for example, 0.05 is set as a reference distortion gradient.

The first region is divided into a first region where the distortion gradient is less than the reference distortion gradient and a second region where the distortion gradient is greater than or equal to the reference distortion gradient.

In the experimental data acquisition step (1), as in the above, a plurality of data having a distortion gradient in the diametrical direction at the leading edge and a distortion gradient equivalent to the distortion limit equivalent to the strain limit of the metal plate after the preliminary molding are obtained as parameters. However, as a plurality of data, two or more first data having a distortion gradient smaller than the reference distortion gradient and two or more second data having a distortion gradient larger than the reference distortion gradient are separately acquired.

Then, the pre-strain equivalent distortion amount setting step (2) and the moldable area specifying step (3) are performed for each of the first data and the second data.

As a result, as the output of the moldable region specifying step 3, a pattern having a distortion gradient of at least one of the first molding limit line L1 and the first moldable region R1, 1 information and at least one of the second shaping limit line L2 and the second moldable region R2 that targets the second region of the distortion gradient of the reference distortion gradient or more (see Fig. 15).

In the molding specification data acquisition step (4), similarly to the above, the molding specifications of the molded article to be formed by performing the primary molding and the secondary molding are preliminarily tentatively subjected to the FEM analysis calculation for the preliminary molding specification, The deformation amount and the distortion gradient of the shearing edge after completion of forming the metal plate are obtained and the amount of distortion equivalent to the pre-deformation equivalent strain is calculated by the preliminary molding in the vicinity of the shearing edge. That is, the distortion gradient generated at the shearing edge to be the object by press molding is estimated by a molded product or molding analysis.

Then, in the provisional judgment step (5), the amount of deformation of the shearing edge after completion of the molding obtained in the molding specification data acquisition step (4) is obtained as a significant amount of distortion at the molding possibility judgment area, It is judged whether or not it exists in the formable area specified by the output information of the area specifying step (3). At this time, if the target distortion gradient is the first area, the first information is used to perform the robust determination, and if the target distortion gradient is the second region, the robustness determination is performed using the second information .

Other configurations, processes, and the like are the same as those of the first embodiment.

The effect of the evaluation method of the present modification example is the same as that of the first embodiment, but is divided into two areas according to a distortion gradient and evaluated. Therefore, it is possible to evaluate by considering the tendency difference between the case where the distortion gradient is large and the case where the distortion gradient is small.

(Second Embodiment)

Next, a second embodiment will be described with reference to the drawings. The same reference numerals as in the first embodiment denote the same components.

As shown in Fig. 16, the method for evaluating moldability according to the present embodiment is characterized in that the test data acquisition step 7 without preforming, the moldable region specifying step 8 without preforming, 9), a molding specification data acquisition step (4), and a possibility judgment step (5).

In the test data acquiring step (7) in the case of no shaping, a hole expanding test is carried out on a metal plate (for example, a metal plate before forming) in the preforming step so that a distortion gradient in the radial direction at the front edge and a deformation limit A plurality of data having different distortion gradients with a significant amount of distortion as a parameter are obtained.

The moldable region specifying process 8 in the case of no mold is different from the plurality of pieces of data obtained in the experimental data obtaining process 7 in the case where no mold is formed. .

For example, on the basis of a plurality of data, a plurality of pieces of data (a distortion gradient, distortion equivalent to a distortion limit) are plotted by taking a distortion gradient on the abscissa and a distortion equivalent to the distortion limit on the ordinate as shown in Fig. 17, Let the line connecting the plotted points be the forming limit line L0 in the case of no preforming.

The forming limit line L0 in the case of no preforming may be obtained by the method described in Japanese Patent Publication No. 4935713. [ By the forming limit line L0 in this preforming, the formable region in the case of no preforming is specified.

In the post-forming conversion process (9), for the forming limit line L0 in the above-described preforming with the distortion gradient as a parameter, conversion for converting the deformation limit equivalent distortion without preforming into the expansion flange deformation equivalent equivalent distortion equivalent The values k1 and k2 are added for each region to obtain the molding limit line Lx in the preforming corresponding to the tensile strain equivalent to the expansion flange deformation limit with respect to the distortion gradient at the shearing edge of the metal plate after the preliminary molding.

Here, as in the first embodiment, the equivalent strain amount applied to the metal plate in the preforming is defined as the strain amount equivalent to the preliminary strain, and the sum of the strain amount equivalent to the preliminary strain and the strain amount equivalent to the strain limit in the post- Flange deformation limit is defined as equivalent distortion.

A region below the forming limit line Lx in the case of the pre-deformation obtained in the conversion step (9) after the preform formation is defined as the formable region R.

The converted values k1 and k2 are values obtained by using a distortion gradient as a variable and are set so that the conversion value k2 when the distortion gradient is larger than the reference distortion gradient is larger than the conversion value k1 when the distortion gradient is less than the reference distortion gradient .

This is because, based on the above knowledge, it is considered that, when the distortion gradient is large, the distortion gradient tends to increase as the distortion increases.

The reference distortion gradient is selected from within the reference distortion range of 0.03 to 0.06, as described above. In the present embodiment, for example, 0.05 is set as a reference distortion gradient.

In the molding specification data acquisition step (4), the molding specifications of the molded product produced by performing the primary molding and the secondary molding are preliminarily evaluated, and the FEM analysis calculation is executed for the preliminary molding specification, The deformation amount and the distortion gradient of the shearing edge are found and the deformation equivalent strain amount generated in the vicinity of the front end edge is calculated as the deformation amount equivalent to the preliminary deformation.

In the provisional judgment step (5), the deformation amount of the shearing edge after completion of the molding obtained in the molding specification data acquisition step (4) is determined as a significant amount of distortion at the molding possibility judgment area, and the obtained data amount and distortion grade data set Is within the formable area R specified by the output information of the conversion step (9). In the case where it is present in the moldable region R, it is evaluated as moldable. Otherwise, it is evaluated that molding is impossible.

Here, the processing of the molding specification data acquisition step (4) and the impossibility judgment step (5) may be similar to those of the first embodiment.

<About converted value>

The converted values k1 and k2 are obtained by arbitrarily setting a representative point from within a region of a distortion gradient with a boundary of a reference distortion gradient as a boundary, and at the representative point, And the difference may be the converted values k1 and k2 in the respective regions.

Next, an example of a method of determining a conversion value will be described.

From the molding specification data acquisition step (4), the amount of strain equivalent strain due to preforming at the position of the front edge to be evaluated is acquired, and the distortion gradient of the front edge is obtained.

When the acquired distortion gradient is less than the reference distortion gradient, the obtained distortion-equivalent distortion amount is multiplied by a coefficient selected in a range of -0.5 to 0.5, and converted into a conversion value. When the acquired distortion gradient is equal to or greater than the reference distortion gradient, the obtained distortion-equivalent distortion amount is multiplied by the selected coefficient in the range of? = 0.5 to 1.0 to obtain the conversion value.

In other words,

k1 =? x? _eq1

k2 =? x? _eq1

.

However, epsilon _eq1 is the strain equivalent strain.

Then, the allowance determining step (5) determines the forming limit value in the preforming using the obtained conversion value for the distortion gradient to be evaluated, and determines whether or not the forming limit exists in the formable region R.

Here, when the amount of strain equivalent strain at the time of molding is constant at the time of forming a molded article, the selected strain is multiplied by a coefficient in the range of? = -0.5 to 0.5, , And multiplies a selected coefficient in a range of? = 0.5 to 1.0 with respect to a distortion-equivalent amount at the time of a certain preliminary molding so as to obtain, as a conversion value for a distortion gradient greater than or equal to a reference distortion gradient, .

Since this embodiment is a simple evaluation method, an arbitrary value may be selected from within the above range. However, in order to further increase the accuracy, the coefficients? And? Are determined as follows.

Here, it is preferable to determine α and β by the following equation.

α = 1-R

β = 1-R

For example, the coefficient to be multiplied may be determined by the ratio of "deformation limit lowering amount / secondary deformation amount in secondary forming" = R as shown in Table 2. In Table 2, for example, the case where the distortion gradient obtained is equivalent to the case where the obtained distortion gradient is less than the reference distortion gradient, and the case of the "distortion gradient band" corresponds to the case where the obtained distortion gradient is not less than the reference distortion gradient.

In the present embodiment, it is possible to easily evaluate the formability of the shearing edge from the experimental data obtained without the preform.

In this case, the precision of the forming limit line may be lower than that of the first embodiment.

Here, in the entire embodiment, when the amount of strain equivalent to the strain at the time of molding is changed in the molding specification, the final molding specification can also be obtained by changing the amount of distortion equivalent strain.

The entire contents of Japanese Patent Application No. 2015-95861 (filed on May 8, 2015), the contents of which are hereby claimed, are hereby incorporated by reference into this disclosure.

While the present invention has been described with reference to a limited number of embodiments, the scope of rights is not limited thereto, and modification of each embodiment based on the above disclosure is obvious to the relevant contractor.

One; Experimental data acquisition process
2; Example Deformation equivalent strain amount setting step
3; Moldable Area Specific Process
4; Mold specification data acquisition process
5; Judgment process
6; Display portion
7; Example Experimental data acquisition process without molding
8; Example Possible Moldability in No Molding Specified Process
9; Example Post-molding conversion process
k1, k2; Conversion value
L; Molding limit line
L0; Example Molding Limit at No Molding
L1, L2; Molding limit line
Lx; Molding limit line
R; Formable region
R1; Formable region
R2 is; Formable region

Claims (6)

An evaluation method for evaluating the possibility of forming a shearing edge by press forming on a metal plate subjected to preliminary deformation by molding,
Example The deformation limit at the shearing edge is found by the hole expansion test on the metal plate after the forming, and the deformation limit amount at the obtained shearing edge is expressed by the deformation amount equivalent to the deformation limit, A plurality of pieces of data having different distortion gradients are obtained as data consisting of a strain amount equivalent to a deformation limit obtained by an enlargement test,
The amount of strain equivalent strain applied to the metal plate in the preforming is defined as the strain amount equivalent to the preliminary strain and the sum of the amount of strain equivalent strain equivalent to the deformation limit in the metal plate after the preliminary forming is made equal to the strain flange deformation limit equivalent strain Lt; / RTI &gt;
A relationship of distortion equivalent to extension flange deformation limit with respect to a distortion gradient is obtained on the basis of the amount of distortion equivalent to the preliminary deformation and the plurality of data,
Wherein the formable region of the front edge is specified from the obtained relationship and the formability of the shearing edge to the metal plate subjected to the preliminary deformation by the preliminary molding is evaluated. An evaluation method for evaluating the possibility of forming a shearing edge by press forming on a metal plate subjected to preliminary deformation by molding,
Example The deformation limit at the shearing edge is found by the hole expansion test on the metal plate after the forming, and the deformation limit amount at the obtained shearing edge is expressed by the deformation amount equivalent to the deformation limit, A plurality of data consisting of distortion amounts equivalent to the deformation limit obtained by the magnification test are acquired,
Wherein the plurality of data includes at least two pieces of first data having a distortion gradient smaller than a distortion gradient of a preset reference and at least two pieces of second data having a distortion gradient larger than a distortion gradient of the reference,
The amount of strain equivalent strain applied to the metal plate in the preforming is defined as the strain amount equivalent to the preliminary strain and the sum of the amount of strain equivalent strain equivalent to the deformation limit in the metal plate after the preliminary forming is made equal to the strain flange deformation limit equivalent strain Lt; / RTI &gt;
A first relationship which is a relationship of distortion equivalent to a stretch flange deformation limit with respect to a distortion gradient is obtained on the basis of the pre-strain equivalent distortion amount and the at least two first data,
A second relationship which is a relationship of distortion equivalent to the expansion flange deformation limit with respect to the distortion gradient is obtained on the basis of the above-mentioned pre-strain equivalent distortion amount and the above-mentioned second or more second data,
A distortion gradient generated in the shearing edge to be a target is estimated by the above press molding,
And if the estimated distortion gradient is less than the distortion gradient of the reference, the first formability region of the front end edge is specified by the first relationship to evaluate molding ability of the front end edge by press molding, and the estimated distortion gradient And the second forming region of the front edge is specified by the second relationship when the difference is equal to or larger than the distortion gradient of the reference, and the forming possibility of the front edge by press forming is evaluated. 3. The method of claim 2,
And the distortion gradient of the reference is selected in the range of 0.03 or more to 0.06 or less. An evaluation method for evaluating the possibility of forming a shearing edge by press forming on a metal plate subjected to preliminary deformation by molding,
The deformation limit at the shearing edge is found by the hole enlargement test on the metal plate without forming, and the deformation limit amount at the found shear edge is expressed by the deformation amount equivalent to the deformation limit, A plurality of pieces of data having different distortion gradients are obtained as data consisting of a strain amount equivalent to a deformation limit obtained by the hole expansion test for a distortion gradient in a radial direction at a front end edge,
From the plurality of data, the relationship between the distortion of the metal plate in the case of no preforming and the case of no preforming, which is the relationship of the amount of strain equivalent to the strain limit in the case of no preforming,
The amount of distortion equivalent to the preform is defined as the amount of distortion equivalent to the preform, and the sum of the amount of distortion equivalent to the preform and the amount of distortion equivalent to the deformation limit in the metal plate after the preform formation is defined as distortion equivalent to the expansion flange deformation limit Define,
The converted value for converting the amount of distortion equivalent to the deformation limit equivalent to the expansion flange deformation equivalent distortion in the relationship in the obtained no-shaping relation to the deformation amount equivalent to the deformation limit is added to the expansion flange deformation limit The relationship in the case of the pre-shaping, which is a significant distortion,
Wherein the formable region of the shearing edge is specified from the relationship in the obtained preformed shape and the formability of the shearing edge to the metal plate subjected to the preliminary deformation by the preforming is evaluated. 5. The method of claim 4,
Wherein the conversion value is set to a value larger than a conversion value when the distortion value is equal to or larger than a predetermined reference distortion value and less than a distortion gradient of the reference. The method according to claim 4 or 5,
Wherein when the conversion value is less than a predetermined reference distortion curve, a value selected from a range of -0.5 times to 0.5 times the amount of distortion equivalent to the preliminary strain at the front edge to be evaluated is regarded as a conversion value, , A value selected from a range of 0.5 times or more and 1.0 times or less the amount of distortion equivalent to the preliminary strain at the front edge to be evaluated is regarded as a conversion value.

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