JP2016211962A - Method for evaluating possibility of formation of shear edge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique to evaluate possibility of formation of a material edge that is sheared after preforming precisely.SOLUTION: A plurality of data on the amount of shear equivalent to a deformation limit relative to distortion inclination by changing the distortion inclination at a shear edge by a hole extension test for a metal plate after preforming. From the plurality of data and the amount of shear equivalent to predeformation, the relationship of the distortion inclination to shear equivalent to an elongation flange deformation limit is obtained. From the formation limit line L and the formable range R of the shear edge obtained from the relationship, the possibility of formation of the shear edge relative to a predeformed metal plate by preforming is evaluated.SELECTED DRAWING: Figure 13

Description

  The present invention relates to a technique for evaluating whether or not a material edge that is sheared after primary forming can be formed. For example, the present invention relates to a technique for evaluating the feasibility of molding by FEM simulation at a shearing edge of an automobile press product or the like.

As a method for evaluating the possibility of forming based on the deformation state in the vicinity of the shearing edge, which has a large influence on the deformation limit at the shearing edge of the press product, for example, there are determination methods described in Patent Documents 1 to 3.
However, each of the above-mentioned methods for determining whether or not a sheared edge of a press product can be formed evaluates a material edge that has been sheared without undergoing predeformation (primary molding), and has been sheared after undergoing predeformation. No consideration is given to the application to the material edge.
As described above, there has been a problem with the accuracy of determining whether or not forming is possible at the shearing edge after undergoing primary deformation, and there has been a problem that whether or not forming is possible is not clear until after the mold is manufactured.

Japanese Patent No. 4935713 Japanese Patent No. 5561203 Japanese Patent No. 5472518

  The present invention pays attention to the above points, and an object of the present invention is to provide a technique for more accurately evaluating whether or not a material edge to be sheared after preforming can be formed.

  In order to solve the problem, one aspect of the present invention is an evaluation method for evaluating whether or not a shear edge can be formed by press forming on a metal plate that has been pre-deformed by pre-forming, and includes a hole in the metal plate after pre-forming. The deformation limit at the shear edge is obtained by the expansion test, the deformation limit at the shear edge is expressed in terms of the deformation limit equivalent strain, and the deformation determined by the above hole expansion test for the radial strain gradient at the shear edge. A plurality of data with different strain gradients are acquired as data consisting of the limit equivalent strain amount, and the equivalent strain amount applied to the metal plate in the preforming is defined as the predeformation equivalent strain amount. The sum of the deformation limit equivalent strain in the metal sheet after pre-forming is defined as the stretch flange deformation limit equivalent strain, and based on the pre-deformation equivalent strain amount and the plurality of data. Obtain the relationship between the strain equivalent to the stretch flange deformation limit and the strain gradient, identify the formable region of the shear edge from the obtained relationship, and evaluate whether or not the shear edge can be formed on a pre-deformed metal plate. It is characterized by.

According to one aspect of the present invention, in a molded product formed through primary molding (pre-molding) and secondary molding, whether or not the material edge of the metal plate to be sheared after preforming is molded can be more easily and accurately evaluated. You will be able to
That is, it is possible to prevent defects due to cracks at an early stage as a result of accurately predicting the possibility of molding at the stretch flange portion in the secondary molding and the molding margin without creating a mold many times. .

It is a figure which shows the relationship between the pre-deformation equivalent distortion | strain and the secondary deformation limit strain in the case where the strain gradient is large in Experiment 1. It is a figure which shows the relationship between the predeformation equivalent distortion | strain and the total deformation amount in the case where the strain gradient is large in Experiment 1. In Experiment 1, it is a figure which shows the relationship between the predeformation equivalent distortion | strain and secondary deformation | transformation limit distortion | strain in case a strain gradient is small. It is a figure which shows the relationship between the predeformation equivalent distortion | strain and the total deformation amount in Experiment 1, when a strain gradient is small. In Experiment 2, it is a figure which shows the relationship between the predeformation equivalent distortion | strain and secondary deformation limit distortion | strain in case a strain gradient is large. It is a figure which shows the relationship between the predeformation equivalent distortion | strain and the total deformation amount in Experiment 2, when a strain gradient is large. In Experiment 2, it is a figure which shows the relationship between the predeformation equivalent distortion | strain and secondary deformation limit distortion | strain in case a strain gradient is small. It is a figure which shows the relationship between the predeformation equivalent distortion | strain and the total deformation amount in Experiment 2, when a strain gradient is small. In Experiment 3, it is a figure which shows the relationship between the predeformation equivalent distortion | strain and secondary deformation limit distortion | strain in case a strain gradient is large. In Experiment 3, it is a figure which shows the relationship between the predeformation equivalent distortion | strain and the total deformation amount in case a strain gradient is large. It is a figure which shows the relationship between the predeformation equivalent distortion | strain and secondary deformation | transformation limit distortion | strain in case the strain gradient is small in Experiment 3. FIG. It is a figure which shows the relationship between the pre-deformation equivalent distortion | strain and the total deformation amount in Experiment 3, when a strain gradient is small. It is a figure explaining the processing process concerning a 1st embodiment based on the present invention. It is a figure explaining the shaping | molding limit line and moldable area | region which concern on 1st Embodiment based on this invention. It is a figure explaining the shaping | molding limit line and moldable area | region which concern on the modification based on this invention. It is a figure explaining the process process which concerns on 2nd Embodiment based on this invention. It is a figure explaining the shaping | molding limit line and moldable area | region which concern on 2nd Embodiment based on this invention.

(Knowledge to the present invention)
The evaluation of the method for determining whether or not a shear edge can be formed by processing according to the above-described prior art assumes only the evaluation of the deformation limit relating to the shear edge from a state where no pre-deformation (primary forming) has been applied. For this reason, it has been unclear whether the above-described conventional evaluation method can be directly applied to the determination of whether or not forming is possible with respect to the shearing edge after undergoing primary deformation. This is because it cannot be said that damage due to shear does not depend on the amount of primary deformation caused by preforming.

The inventor conducted a detailed investigation for quantitatively elucidating the influence of the pre-deformation amount (primary deformation amount) on the deformation limit during secondary molding.
The contents will be described below.
Here, using the test materials A to E shown in Table 1, various hole expansion tests were performed on the metal plate to which primary forming (predeformation) was applied. As the hole expansion test, a conical hole expansion test using a conical punch and a cylindrical hole expansion test using a cylindrical punch were performed.

In the above hole expansion test, after subjecting a target metal plate to a truncated cone shape, the sample is centered on the upper surface of the truncated cone, and the cut sample is flattened. Thereafter, a test is performed in which a punch hole is formed in the center of the sample and the punch hole is widened by a punch. The cone-shaped punch used is a 60-degree cone punch, and the cylindrical punch is a cylindrical punch having a diameter of 50 mm.
The strain gradient in the radial direction can be adjusted by changing the shape of the punch used or the diameter of the punched hole after preforming.

<Experiment 1>
A conical hole expansion test was performed on the metal plate made of the test material A.
And when it summarized by the secondary deformation | transformation limit distortion | strain in the metal plate after pre-forming with respect to the pre-deformation equivalent distortion | strain by preforming, the result shown in FIG. 1 was obtained. Further, when the total deformation amount, which is the sum of the pre-deformation equivalent strain and the secondary deformation limit strain, is summarized with respect to the pre-deformation equivalent strain by the pre-forming, the result shown in FIG. 2 was obtained.

Next, a cylindrical hole expansion test was performed on the metal plate made of the test material A.
And when it summarized by the secondary deformation | transformation limit distortion | strain in the metal plate after pre-forming with respect to the pre-deformation equivalent distortion | strain by preforming, the result shown in FIG. 3 was obtained. Further, when the total deformation amount, which is the sum of the pre-deformation equivalent strain and the secondary deformation limit strain, is summarized with respect to the pre-deformation equivalent strain due to the pre-forming, the result shown in FIG. 4 was obtained.

Here, in each figure,
●: Strain due to equal biaxial ■: Strain due to unequal biaxial ▲: Strain due to plane strain

When conical hole expansion is performed, the strain gradient at the shear edge becomes larger than when cylindrical hole expansion is performed.
Therefore, in the specimen A, when the strain gradient is large, as can be seen from FIG. 1, the secondary deformation limit strain decreases as the amount of pre-deformation equivalent strain increases, but as can be seen from FIG. The amount of deformation tends to increase as the amount of pre-deformation equivalent strain increases.

On the other hand, when the strain gradient at the shearing edge is small, as can be seen from FIG. 3, the secondary deformation limit strain decreases as the amount of pre-deformation equivalent strain increases, but as can be seen from FIG. However, it does not depend much on the amount of pre-deformation equivalent strain, and its correlation with the amount of pre-deformation equivalent strain is low.
Further, as can be seen from FIGS. 1 to 4, the influence of the pre-deformation equivalent strain amount (pre-deformation amount, primary deformation amount) on the secondary deformation limit strain does not depend much on the pre-deformation deformation mode. For this reason, it was found that the secondary deformation limit strain can be arranged by the equivalent strain.

<Experiment 2>
For the test material D, an experiment similar to the experiment 1 was performed. The results are shown in FIGS.
It can be seen that this sample material D also has the same tendency as the sample material A, as can be seen from FIGS.
<Experiment 3>
The test material E was subjected to the same experiment as the experiment 1. The results are shown in FIGS.
As can be seen from FIG. 9 to FIG. 12, the specimen E has a tendency similar to that of the specimen A, but also has the following tendency.
That is, when the strain gradient is large, the secondary deformation limit hardly decreases depending on the amount of pre-deformation in a predetermined deformation region. On the other hand, when the strain gradient is small, the total deformation amount depends on the pre-deformation amount and decreases as the pre-deformation amount increases. That is, applying the pre-deformation has an adverse effect.

<Summary of experimental results>
Experiments B and C were also performed in the same manner as Experiment 1.
When the above results are summarized by the ratio of (the amount of decrease in deformation limit amount in secondary molding) to the amount of predeformation (predeformation equivalent strain amount), the results shown in Table 2 were obtained.

  As can be seen from Table 2, it can be seen that when the strain gradient is large compared to when the strain gradient is small, the forming margin for the metal plate after pre-forming may be underestimated. And if it is underestimated, it turns out that there is a risk of unnecessary mold correction.

<Knowledge>
From the above experiments, the inventors have obtained the following knowledge.
(1) The degree of influence of the primary deformation amount on the deformation limit strain after shearing does not depend much on the deformation form (equal biaxial, unequal biaxial, plane strain) of the deformation limit strain after shearing, and is organized by the equivalent strain. it can.
For this reason, in this invention, it evaluates by a considerable distortion.

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

That is, the final deformation limit strain of the stretch flange portion by secondary forming including pre-deformation depends on both the primary deformation amount and the strain gradient.
Further, the dependence of the primary deformation differs depending on whether the strain gradient is large or small. That is, the accuracy of the evaluation is improved by evaluating the shear edge separately when the strain gradient is small or large with respect to the predetermined strain gradient. This tendency does not depend on the thickness.
The present invention has been made based on the above new findings.
Each embodiment based on this knowledge will be described below.

(First embodiment)
Next, a method for evaluating whether or not a shear edge can be formed according to this embodiment will be described with reference to the drawings.
The method for evaluating whether or not a shear edge can be formed according to the present embodiment is a technique for evaluating whether or not a shear edge can be formed on a primary-formed (pre-formed) metal plate.

<Constitution>
As shown in FIG. 13, the moldability evaluation method of the present embodiment includes an experimental data acquisition step 1, a pre-deformation equivalent strain amount setting step 2, a moldable region specifying step 3, a molding specification data acquisition step 4, and a propriety determination step. 5 is provided.
In the experimental data acquisition step 1, a hole expansion test is performed on a preliminarily formed metal plate. In the hole expansion test, two or more types of hole expansion tests with different radial strain gradients at the shear edges are performed by changing the punch shape to be used or the diameter of the punched hole before diameter expansion.

The preforming performed on the metal plate to acquire data and the hole expansion test on the preformed metal plate may be performed by the method described in Experiment 1 above. In this case, it is convenient to perform primary molding so that the amount of equivalent strain due to preforming added to the place where hole expansion is performed becomes a constant value.
Here, the strain gradient of the hole after diameter expansion by each hole expansion test is specified by analysis of the molded product by the test or molding analysis (FEM analysis calculation) performed separately. Moreover, the deformation limit strain amount generated at the shearing edge of each hole by secondary forming is obtained from the hole expansion rate obtained by each hole expansion test. In this embodiment, the deformation limit equivalent strain amount is adopted as the deformation limit strain amount to be acquired.

The hole expansion ratio λ can be expressed by the following formula, where d0 is the diameter of the punched hole and d is the diameter of the hole after expansion.
λ = ((d−d0) / d0) × 100
In the present embodiment, the strain gradient is expressed as an average gradient of the maximum main strain in a predetermined section (for example, a section from the edge to 5 mm) along the radial direction from the edge of the hole. In the present embodiment, the value of the strain gradient is expressed as an absolute value.

Through the above processing, the experimental data acquisition step 1 acquires a plurality of data with different strain gradients as data consisting of the radial strain gradient at the shear edge and the deformation limit equivalent strain amount in the pre-formed metal plate. To do. The position to acquire is specified by the user.
Pre-deformation equivalent strain amount setting step 2 was added to the metal plate by pre-forming in the part to be subjected to the hole expansion in the above-mentioned hole expansion test by a preformed molded product or separately performed molding analysis (FEM analysis calculation). The equivalent strain amount is acquired as the pre-deformation equivalent strain amount. The pre-deformation equivalent strain amount may be acquired or the primary processing conditions may be set during the hole expansion test.

The formable region specifying step 3 is a process of expanding flange deformation with respect to a strain gradient from a plurality of data having different strain gradients acquired in the experimental data acquisition step 1 and a pre-deformation equivalent strain amount acquired in the pre-deformation equivalent strain amount setting step 2. Find the limit equivalent strain relationship.
Here, the stretch flange deformation limit equivalent strain is the sum of the deformation limit equivalent strain amount and the predeformation equivalent strain amount. That is, the deformation equivalent to the deformation limit acquired in the experimental data acquisition step 1 is added to the strain equivalent to the pre-deformation obtained in the pre-deformation equivalent strain setting step 2 to obtain an elongation flange deformation limit equivalent strain.

As a result, two or more data having two parameters, ie, strain gradient and stretch flange deformation limit equivalent strain, as parameters (variables) can be obtained as relation generation data.
Then, as shown in FIG. 14, the horizontal axis represents the strain gradient, the vertical axis represents the stretch flange deformation limit equivalent strain, and the obtained data (strain gradient, stretch flange deformation limit equivalent strain) are plotted. A line connecting the plotted points is defined as a forming limit line L. Then, with the forming limit line L as a boundary, the lower region is specified as the moldable region R.

  Here, if the data to be acquired is two data, a straight line passing through the two points is set as a forming limit line L as shown in FIG. In this case, for example, one data preferably has a strain gradient of less than 0.03, and the other data preferably has a strain gradient of 0.06 or more. Or if the range of the strain gradient that may occur in the secondary forming is determined, two data having the strain gradient in the range may be adopted. In any case, it is preferable that the two strain gradients are separated by 0.03 or more.

It is preferable that the data to be acquired is three or more data. In this case, it is preferable to include three data: data having a strain gradient of 0.03 or less, data having a strain gradient of 0.06 or more, and data having a value greater than 0.03 and less than 0.06. If it does in this way, it will become possible to obtain the forming limit line L in consideration of the difference in tendency when the strain gradient is large and small.
When the data to be plotted is three or more points, a line connecting adjacent points with a straight line is defined as a forming limit line L, and a curve passing through the plurality of data is defined as a forming limit line L.

Here, the forming limit line L obtained in the formable region specifying step 3 may be obtained as a relational expression using (strain gradient, stretch flange deformation limit equivalent strain) as a parameter.
In the moldable region specifying step 3, a plurality of data having different strain gradients acquired in the experimental data acquiring step 1 and a predeformation equivalent strain amount data acquired in the predeformation equivalent strain amount setting step 2 are input. The calculation of the above processing may be executed by a computer to output and generate information on at least one of the forming limit line L and the moldable region R. The molding limit line L may be stored as a formula as a formula.

Here, calculation processing parts other than the hole expansion test in the experimental data acquisition step 1 may be executed by a computer using a program such as FEM analysis calculation.
With the above processing, the acquisition of basic information for evaluating whether or not a shear edge can be formed by press forming on a metal plate that has been pre-deformed by pre-forming is completed.
In the molding specification data acquisition process 4, provisional molding specifications of a molded product created in at least two processes of primary molding and secondary molding are provisionally performed, and FEM analysis calculation is performed on the provisional molding specifications to obtain a pre-formed metal plate. The deformation amount and strain gradient of the shearing edge after the completion of the forming are calculated, and the equivalent strain amount generated in the vicinity of the shearing edge by pre-forming is calculated as the predeformation equivalent strain amount. In this molding specification data acquisition step 4, in addition to FEM analysis calculation, data may be acquired by performing experiments as necessary.

Here, in the molding specification of the molded product, the magnitude of the pre-deformation equivalent strain differs depending on the shape applied to the pre-molding and often varies depending on the position of the stretch flange. It is preferable to calculate. When the width of the pre-deformation equivalent strain generated at each shear edge at the time of preforming is narrow, the representative value may be adopted.
In the feasibility determination step 5, the total deformation amount at the shearing edge after completion of molding, which is obtained in the molding specification data acquisition step 4, is output as the equivalent strain amount at the molding possibility determination target portion. Then, it is determined whether the data set of the total deformation amount and the strain gradient exists in the moldable region R specified by the output information of the moldable region specifying step 3. If it exists in the moldable region R, it is evaluated that molding is possible, and if it is not, it is evaluated that molding is not possible. This evaluation may be automatically performed by a computer. Then, the evaluation is displayed on the display unit 6.

Here, the acquisition data for the shear edge evaluation in the provisional molding specification is not limited to one place, but may be obtained at a plurality of shear edges and each of the above-described evaluation of the possibility of forming may be performed.
Then, if there is a molding-impossible shear edge, re-form a provisional molding specification (pre-molding specification and post-molding specification) that changes the specifications in the vicinity of the molding-impossible shear edge, The molding specification data acquisition step 4 and the availability determination step 5 are repeated. Then, the final forming specification for the pre-formed metal plate is determined from the provisional forming specification which can be formed at all the set shear edge portions.
Here, what is necessary is just to obtain | require and use the shaping | molding limit line L for every steel type of the metal plate to be used.
Further, in the above-described molding evaluation, the possibility determination is exemplified, but the degree of allowance may be evaluated or the degree of deformation may be exceeded.

<Effect of this embodiment>
This embodiment has the following effects.
(1) Acquire a plurality of deformation limit equivalent strain data in the pre-formed metal plate with respect to the strain gradient at the shear edge, and obtain the relationship between the strain corresponding to the stretch flange deformation limit and the strain gradient based on the data. By specifying the forming limit line L from the obtained relationship, the formable region R of the shear edge is specified. Then, based on the specified forming limit line L and the formable region R, whether or not forming is possible is evaluated with respect to the total deformation amount with respect to the strain gradient at the shear edge obtained from the provisional forming specification.

According to this configuration, it is possible to more easily and accurately evaluate whether or not the material edge of the metal plate to be sheared after pre-forming in a formed product formed through primary forming (pre-forming) and secondary forming can be formed. become able to do.
That is, it is possible to prevent defects due to cracks at an early stage as a result of accurately predicting the possibility of molding at the stretch flange portion in the secondary molding and the molding margin without creating a mold many times. .
Moreover, it is not necessary to consider the difference of a strain form by evaluating by equivalent strain.

<Modification>
Here, in the above-described embodiment, the case where one continuous forming limit line L is obtained is described. On the other hand, in this modification, the strain gradient is set within a reference strain gradient range of 0.03 or more and 0.06 or less, and is divided into two regions with the reference strain gradient as a boundary, and a forming limit line is set for each division. L1 and L2 are obtained.

  Here, the inventor has confirmed that the strain corresponding to the stretch flange deformation limit, which is the sum of the deformation limit equivalent strain amount and the predeformation equivalent strain amount, is large when the strain gradient is small. It doesn't depend much. On the other hand, when the strain gradient is large, the stretch flange deformation limit equivalent strain tends to increase as the pre-deformation equivalent strain amount increases. When the inventor confirmed the boundary between the two strain gradients, it was confirmed that the boundary exists between 0.03 and 0.06, so the reference strain gradient range was set to 0.03 or more and 0.06 or less. Preferably, it is 0.04 or more and 0.05 or less.

For example, when the strain gradient of the part where the determination of whether or not stretch flange forming in secondary molding is a problem in various automotive press products was examined, it was roughly classified as less than 0.03 or 0.06 or more.
Depending on the hole diameter, in many cases, the strain gradient is 0.06 or more in the conical hole expansion test, and the strain gradient is less than 0.03 in the cylindrical hole expansion test.
From the above, the reference strain gradient as a boundary is set to the above range.

The evaluation method in this modification will be described in detail.
First, a reference strain gradient is selected from a reference strain gradient range of 0.03 or more and 0.06 or less. In the present embodiment, for example, 0.05 is set as the reference strain gradient.
And it divides into two, the 1st field where a strain gradient is less than a standard strain gradient, and the 2nd field where a strain gradient is more than a standard strain gradient.

  In the experimental data acquisition step 1, as described above, a plurality of data with different strain gradients are obtained using the radial strain gradient at the shear edge and the deformation limit equivalent strain amount for the metal plate after the preforming as parameters. To do. However, two or more first data composed of a strain gradient smaller than the reference strain gradient and two or more second data composed of a strain gradient larger than the reference strain gradient are individually used as a plurality of data. get.

Then, for each of the first data and the second data, the pre-deformation equivalent strain amount setting step 2 and the moldable region specifying step 3 are performed.
Thereby, as an output of the moldable region specifying step 3, from at least one of the first molding limit line L1 and the first moldable region R1 that target the first region whose strain gradient is less than the reference strain gradient. And second information consisting of at least one of the second molding limit line L2 and the second moldable region R2 for the second region whose strain gradient is equal to or greater than the reference strain gradient. (See FIG. 15).

  Then, in the molding specification data acquisition step 4, as described above, the molding specifications of the molded product created by performing the primary molding and the secondary molding are provisionally performed, the FEM analysis calculation is performed on the provisional molding specifications, The deformation amount and strain gradient of the shearing edge after completion of forming the pre-formed metal plate are obtained, and the equivalent strain amount generated in the vicinity of the shearing edge by pre-forming is calculated as the predeformation equivalent strain amount. That is, a strain gradient generated at a target shear edge by press molding is estimated by a molded product or molding analysis.

  And in the propriety determination step 5, the deformation amount of the shearing edge after the completion of molding obtained in the molding specification data acquisition step 4 is obtained as an equivalent strain amount in the molding propriety determination portion, and the obtained deformation amount and strain gradient are calculated. It is determined whether the data set exists in the moldable area specified by the output information of the moldable area specifying step 3. At this time, if the target strain gradient is the first region, the first information is used to determine whether the target strain gradient is the second region. If the target strain gradient is the second region, the second information is determined. Use the to determine whether or not.

Other configurations and processes are the same as those in the first embodiment.
Although the effect of the evaluation method of this modification is the same as that of the first embodiment, the evaluation is divided into two regions according to the strain gradient. For this reason, it becomes possible to evaluate in consideration of the difference in tendency between when the strain gradient is large and when the strain gradient is small.

(Second Embodiment)
Next, a second embodiment will be described with reference to the drawings. The same components as those in the first embodiment will be described with the same reference numerals.
As shown in FIG. 16, the moldability evaluation method of the present embodiment includes an experimental data acquisition step 7 without preforming, a moldable region specifying step 8 without preforming, a conversion step 9 after preforming, and molding. A specification data acquisition step 4 and an availability determination step 5 are provided.

In the experimental data acquisition step 7 without pre-forming, a hole expansion test is performed on a metal plate without pre-forming (the metal plate before pre-forming), and the radial strain gradient at the shear edge and the metal plate A plurality of data having different strain gradients with the deformation limit equivalent strain amount as a parameter is obtained.
The process 8 for determining the formable region without preforming is the relationship between the strain limit equivalent strain amount and the strain gradient for the metal plate without preforming from a plurality of data obtained by the experimental data acquisition step 7 without preforming. Ask for.

For example, based on a plurality of data, the horizontal axis indicates the strain gradient and the vertical axis indicates the deformation limit equivalent strain, and the obtained plural data (strain gradient, deformation limit equivalent strain) are plotted. A line connecting the plotted points is defined as a forming limit line L0 without pre-forming.
The molding limit line L0 without pre-molding may be obtained by the method described in Japanese Patent No. 4935713. The formable region without preforming is specified by the molding limit line L0 without preforming.

  In the conversion step 9 after pre-forming, the deformation limit equivalent strain without pre-forming is converted into the equivalent strain corresponding to the stretch flange deformation limit with respect to the forming limit line L0 without pre-forming, using the strain gradient as a parameter. The forming limit line with pre-forming corresponding to the stretch flange deformation limit equivalent strain with respect to the strain gradient at the shear edge in the pre-formed metal plate by adding the converted values k1, k2 for each region Lx is obtained.

Here, as in the first embodiment, the equivalent strain applied to the metal plate in the pre-forming is defined as the pre-deformation equivalent strain, and the pre-deformation equivalent strain and the deformation limit in the metal plate after the pre-forming. The sum of the equivalent strain is defined as the strain equivalent to the stretch flange deformation limit.
And the area | region below the shaping | molding limit line Lx with pre-deformation calculated | required in the conversion process 9 after pre-molding is made into the moldable area | region R. FIG.

The converted values k1 and k2 are values having a strain gradient as a variable. The converted value k2 when the strain gradient is equal to or higher than the reference strain gradient is smaller than the converted value k1 when the strain gradient is less than the reference strain gradient. Is set to be larger.
This is based on the above findings and takes into account that when the strain gradient is large, it tends to increase with an increase in preforming than when the strain gradient is small.

The reference strain gradient is selected from the range of 0.03 or more and 0.06 or less of the reference strain gradient as described above. In the present embodiment, for example, 0.05 is set as the reference strain gradient.
In the molding specification data acquisition step 4, provisional molding specifications of a molded product created by performing primary molding and secondary molding are provisionally performed, and FEM analysis calculation is performed on the provisional molding specifications to obtain a metal plate after preforming. The deformation amount and strain gradient of the shearing edge after forming is calculated for the above, and the deformation equivalent strain amount generated in the vicinity of the shearing edge by pre-forming is calculated as the predeformation equivalent strain amount.

In the propriety determination step 5, the deformation amount of the shear edge after the completion of molding obtained in the molding specification data acquisition step 4 is obtained as an equivalent strain amount in the molding feasibility determination portion, and a data set of the obtained deformation amount and strain gradient is obtained. Is present in the formable region R specified by the output information of the conversion step 9 after pre-molding. If it exists in the moldable region R, it is evaluated that molding is possible, and if it is not, it is evaluated that molding is not possible.
Here, the processing of the molding specification data acquisition step 4 and the availability determination step 5 may be the same processing as in the first embodiment.

<About the conversion value>
These converted values k1 and k2 are set with a representative point arbitrarily from within each strain gradient region with the reference strain gradient as a boundary, and at the representative point, there is a forming limit value and pre-forming without each pre-deformation. It is also possible to obtain the molding limit value at 1 by experiment or the like and use the difference as the converted values k1 and k2 in each region.

Next, an example of another conversion value determination method will be described.
From the molding specification data acquisition step 4, the deformation equivalent strain amount by pre-forming at the shear edge position to be evaluated is acquired, and the strain gradient of the shear edge is acquired.
If the acquired strain gradient is less than the reference strain gradient, the acquired deformation equivalent strain amount is multiplied by a coefficient selected from the range of α = −0.5 to 0.5 to obtain a converted value. If the acquired strain gradient is equal to or greater than the reference strain gradient, the acquired deformation equivalent strain amount is multiplied by a coefficient selected from the range of β = 0.5 to 1.0 to obtain a converted value.

That is,
k1 = α × ε _eq1
k2 = β × ε _eq1
It becomes.
However, ε _eq1 is a _{pre-deformation} equivalent strain amount.

Then, the feasibility determination step 5 determines the molding limit value with preforming by using the calculated conversion value for the strain gradient to be evaluated, and determines whether it exists in the moldable region R.
Here, when the deformation equivalent strain amount at the time of preforming is constant at the time of forming the molded product, α = −0.5 to 0.5 with respect to the constant deformation equivalent strain amount at the time of preforming. Multiply by a coefficient selected from the range of, to obtain a converted value for strain gradients below the standard strain gradient, and select from the range of β = 0.5 to 1.0 for the deformation equivalent strain amount at the time of constant preforming By multiplying the calculated coefficient, the conversion value for the strain gradient equal to or higher than the reference strain gradient is determined in advance.

Since this embodiment is a simple evaluation method, any value may be selected from the above range and used. However, in order to increase the accuracy, the coefficients α and β are determined as follows. .
Here, α and β are preferably determined by the following equations.
α = 1−R
β = 1−R
For example, the coefficient to be multiplied may be determined according to the ratio of “deformation limit reduction amount in secondary molding / predeformation amount” = R as shown in Table 2. In Table 2, for example, the case of “low strain gradient” corresponds to the case where the acquired strain gradient is less than the reference strain gradient, and the case of “large strain gradient” indicates that the acquired strain gradient is greater than or equal to the reference strain gradient. It corresponds to.

In the present embodiment, it is possible to easily evaluate whether or not a shear edge can be formed from experimental data obtained without pre-forming.
In this case, the accuracy of the forming limit line may be lower than in the first embodiment.
Here, in all the embodiments, when the pre-deformation equivalent strain amount in the pre-molding can be changed by the molding specification, the final molding specification is obtained by changing the pre-deformation equivalent strain amount side as well. Is also possible.

1 Experimental data acquisition process 2 Pre-deformation equivalent strain amount setting process 3 Moldable area identification process 4 Molding specification data acquisition process 5 Acceptability determination process 6 Display unit 7 Experimental data acquisition process without pre-molding 8 Molding without pre-molding is possible Region specific process 9 Conversion process k1, k2 after pre-molding Conversion value L Forming limit line L0 Forming limit line L1, L2 without pre-forming Forming limit line Lx Forming limit line R Formable area R1 Formable area R2 Formable region

Claims (6)

An evaluation method for evaluating the possibility of forming a shear edge by press forming on a metal plate pre-deformed by pre-forming,
The deformation limit at the shear edge is obtained by the hole expansion test for the pre-formed metal plate, the deformation limit amount at the shear edge is expressed as a deformation limit equivalent strain amount, and the radial strain gradient at the shear edge is expressed. As data consisting of the deformation limit equivalent strain amount obtained by the above hole expansion test, obtain multiple data with different strain gradients,
The equivalent amount of strain applied to the metal plate in the pre-forming is defined as the pre-deformation equivalent strain amount, and the sum of the pre-deformation equivalent strain amount and the deformation limit equivalent strain amount in the metal plate after the pre-forming is stretched flange It is defined as deformation equivalent strain,
Based on the amount of strain equivalent to the pre-deformation and the plurality of data, the relationship between the strain corresponding to the stretch flange deformation limit and the strain gradient is obtained,
A shear edge formability evaluation method characterized by identifying a formable area of a shear edge from the obtained relationship and evaluating the formability of a shear edge on a metal plate pre-deformed by pre-forming. An evaluation method for evaluating the possibility of forming a shear edge by press forming on a metal plate pre-deformed by pre-forming,
The deformation limit at the shear edge is obtained by the hole expansion test for the pre-formed metal plate, the deformation limit amount at the shear edge is expressed as a deformation limit equivalent strain amount, and the radial strain gradient at the shear edge is expressed. Acquire a plurality of data consisting of the deformation limit equivalent strain obtained by the hole expansion test,
The plurality of data includes two or more first data having a strain gradient smaller than a preset reference strain gradient and two or more second data having a strain gradient larger than the reference strain gradient. Have
The equivalent amount of strain applied to the metal plate in the pre-forming is defined as the pre-deformation equivalent strain amount, and the sum of the pre-deformation equivalent strain amount and the deformation limit equivalent strain amount in the metal plate after the pre-forming is stretched flange It is defined as deformation equivalent strain,
Based on the amount of strain equivalent to pre-deformation and the first data of 2 or more, a first relationship that is a relationship of strain equivalent to the stretch flange deformation limit with respect to the strain gradient is obtained,
Based on the pre-deformation equivalent strain amount and the second data of 2 or more, a second relationship that is a relationship of the strain corresponding to the stretch flange deformation limit with respect to the strain gradient is obtained,
Estimate the strain gradient generated at the target shear edge by the press molding,
When the estimated strain gradient is less than the reference strain gradient, the first formable region of the shear edge is specified according to the first relationship to evaluate whether the shear edge can be formed by press molding, When the estimated strain gradient is equal to or greater than the reference strain gradient, the second formable region of the shear edge is specified by the second relationship, and whether or not the shear edge is formed by press forming is evaluated. A method for evaluating whether or not a shear edge can be formed.   3. The shear edge moldability evaluation method according to claim 2, wherein the reference strain gradient is selected from a range of 0.03 to 0.06. An evaluation method for evaluating the possibility of forming a shear edge by press forming on a metal plate pre-deformed by pre-forming,
The deformation limit at the shear edge is obtained by the hole expansion test for the metal plate without pre-formation, and the deformation limit amount at the shear edge is expressed in terms of the deformation limit equivalent strain amount. , Data consisting of the deformation limit equivalent strain amount obtained by the above-mentioned hole expansion test for the radial strain gradient at the shear edge, obtaining a plurality of data with different strain gradients,
From the plurality of data, in the metal plate without pre-formation, to obtain the relationship without pre-forming, which is the relationship of the deformation limit equivalent strain amount without pre-formation to the strain gradient,
The equivalent strain applied to the metal plate during pre-forming is defined as the pre-deformation equivalent strain amount, and the sum of the pre-deformation equivalent strain amount and the deformation limit equivalent strain amount in the metal plate after pre-forming is stretched flange deformation It is defined as the limit equivalent strain,
By adding the converted value for converting the deformation limit equivalent strain amount to the elongation flange deformation limit equivalent strain in the relationship without the preforming to the deformation limit equivalent strain amount, the elongation flange deformation with respect to the strain gradient Find the relationship with pre-forming, which is the limit equivalent strain relationship,
Determine the shear edge moldable area from the relationship with the pre-formation obtained above, and evaluate whether the shear edge can be formed on a pre-deformed metal plate. Evaluation method.   The shear value according to claim 4, wherein the converted value when the value is equal to or higher than a preset reference strain gradient is set to a value larger than the converted value when the value is less than the reference strain gradient. Edge evaluation method for moldability.   When the converted value is less than a preset standard strain gradient, the converted value is a value selected from the range of −0.5 to 0.5 times the amount of pre-deformation equivalent strain at the shear edge to be evaluated. When the strain gradient is equal to or higher than the reference strain gradient, a value selected from a range of 0.5 to 1.0 times the pre-deformation equivalent strain amount at the shear edge to be evaluated is used as the converted value. Item 6. The method for evaluating the possibility of forming a shear edge according to Item 4 or Item 5.

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