JP7624894B2 - Sheet edge elongation evaluation device - Google Patents

Description

The present invention relates to an edge elongation evaluation device for sheet metal.

For example, in the manufacturing process of automobile parts, metal plate material is formed into a desired shape by performing multiple press processes on the plate material. In this case, it is important to take note of the elongation that occurs at the edge of the plate material during press processing. In other words, if the elongation of the edge of the plate material exceeds the allowable amount, there is an increased risk of defects such as cracks occurring at the end surface of the edge, so it is necessary to take note of the elongation characteristics of this edge when designing the product.

Here, a test using so-called burring is known as a means for evaluating the elongation characteristics of the edge of a plate material. That is, in this test, as described in Patent Document 1, a plate material with a hole of a specified size is prepared, and a punch with a tapered surface at a specified angle on the outer periphery of the tip is pressed into the hole of the plate material, bending the entire periphery of the hole and expanding the hole. This causes elongation in the periphery of the hole. Therefore, for example, by evaluating the limit of elongation at which cracks occur on the end face of the periphery of the hole (in Patent Document 1, the height of the periphery after bending), it is possible to evaluate the elongation characteristics of the edge of the plate material.

Re-table 2016/92657 publication

By the way, when evaluating the elongation characteristics of the above-mentioned plate edge, there is a demand to evaluate the elongation characteristics of, for example, a straight edge or a curved edge with a small curvature. Here, when trying to evaluate the elongation characteristics using burring as in Patent Document 1, a method is considered in which, for example, using an evaluation device 50 shown in Figures 9 and 10, the plate W is positioned so as to cover half of the insertion hole 53 of the punch 52 provided in the die 51, and the punch 52 is pressed toward the plate W. In this case, the semicircular part Wa including the edge W1 of the plate W is bent with a predetermined elongation (see Figure 11). However, with such a method, the elongation (strain) is concentrated at both ends Wa1 of the bent part (semicircular part Wa), and the part that is really to be evaluated (for example, the edge W1 at the circumferential center of the semicircular part Wa in Figure 11) hardly elongates. This makes it difficult to accurately evaluate the elongation characteristics of each sheet material, as it is difficult to differentiate between them.

In light of the above, the technical problem to be solved in this specification is to be able to properly evaluate the elongation characteristics of the edge of the sheet material, regardless of the edge shape.

The above problem is solved by the edge elongation evaluation device for sheet material according to the present invention. That is, this evaluation device is equipped with a convex mold and a concave mold, and is used to evaluate the elongation of the edge when the edge of a sheet material placed between the convex mold and the concave mold is pressed in with a pressing part located at the tip of the convex mold to bend the edge. The concave mold has an insertion hole through which the pressing part of the convex mold can be inserted, the insertion hole has a notch shape, the peripheral part of the insertion start side of the insertion hole has a convex curved shape over its entire area, and the curvature of the peripheral part is relatively small on the side close to the notch part of the insertion hole and relatively large on the side far from the notch part.

In this way, the present invention focuses on the shape of the peripheral portion of the through hole formed in the shape of a notch in the concave mold, and gives the peripheral portion a convex curved shape over its entire area, with the curvature of the peripheral portion varying in the circumferential direction. Specifically, the shape of the peripheral portion is set so that the curvature of the peripheral portion is relatively small on the side closer to the notch of the through hole and relatively large on the side farther away. With this configuration, when the plate material is bent by pressing with the convex mold, both ends of the bent portion are deformed while being pressed against the area of the peripheral portion of the through hole in the concave mold with a relatively small curvature. Meanwhile, the portion away from both ends of the bent portion (for example, the center side in the width direction on the base end side of the bent portion) is deformed while being pressed against the area of the peripheral portion of the through hole with a relatively large curvature. Therefore, while the plate material can be easily bent by pressing the punch, the elongation that occurs at both ends of the bent portion of the plate material can be suppressed compared to when the curvature of the peripheral portion 54 of the insertion hole 53 is a constant shape in the circumferential direction, for example as shown in Figure 10. This allows areas other than both ends of the edge to be relatively stretched, preventing the edge elongation from concentrating in a specific location and making it possible to properly evaluate the elongation characteristics of the edge.

As described above, the edge elongation evaluation device for sheet metal according to the present invention makes it possible to properly evaluate the elongation characteristics of the edge of the sheet metal regardless of the edge shape.

1 is a front view of an apparatus for evaluating edge elongation of a plate material according to an embodiment of the present invention. FIG. 2 is a plan view of the evaluation device shown in FIG. 1 . 2 is a side view of an insertion hole of the evaluation device shown in FIG. 1 as viewed in the direction of arrow A. 3A is a cross-sectional view taken along B1-B1 of the evaluation device shown in FIG. 2, FIG. 3B is a cross-sectional view taken along B2-B2, and FIG. 3C is a cross-sectional view taken along B3-B3. FIG. 3 is a diagram for explaining an example of a method for evaluating the edge elongation of a sheet material using the evaluation device shown in FIG. 1 and FIG. 2, and shows (a) a view taken along the arrow A of the sheet material immediately after starting to press the punch, and (b) a cross-sectional view taken along the line B1-B1. FIG. 3 is a diagram for explaining an example of a method for evaluating the edge elongation of a sheet material using the evaluation device shown in FIG. 1 and FIG. 2, and shows (a) a view taken along the arrow A of the sheet material at a point in the middle of a portion of the sheet material being bent by pressing in with a punch, and (b) a cross-sectional view taken along the line B1-B1. FIG. 3 is a diagram for explaining an example of a method for evaluating the edge elongation of a sheet material using the evaluation device shown in FIG. 1 and FIG. 2, and shows (a) an arrow A view of the sheet material in a state in which a portion of the sheet material has been bent to a predetermined position by pressing in with a punch, and (b) a B1-B1 cross-sectional view. 8 is a view of the pressed and bent portion of the plate material shown in FIG. 7 as viewed from an oblique direction. FIG. 2 is a front view of an edge elongation evaluation device for a plate material for comparison with the present invention. FIG. 10 is a plan view of the evaluation device shown in FIG. 9 . FIG. 11 is a view of a bent portion of a plate material obtained when the evaluation device shown in FIGS. 9 and 10 is used, as viewed from an oblique direction.

The details of the edge elongation evaluation device for sheet metal according to one embodiment of the present invention are explained below with reference to the drawings.

Figure 1 shows a front view of a sheet material edge elongation evaluation device 10 according to one embodiment of the present invention. Also, Figure 2 shows a plan view of the evaluation device 10 shown in Figure 1. As shown in these figures, this evaluation device 10 comprises a punch 11 as a convex mold, a die 12 as a concave mold, and a pad 13. Below, the details of each element will be explained, focusing on the configuration of the die 12. Note that the pad 13 has been omitted from figures other than Figure 1 in order to make it easier to understand the contents shown in the figures.

In addition, Figures 1 and 2 show an example in which two dies 12 are installed butted against each other for one punch 11, and a sheet material W is placed on each die 12, in order to equalize the pushing pattern of the punch 11.

The punch 11 is used to press and bend the plate material W to be evaluated, and in this embodiment, has an integral body 14 having an elliptical cross section and a pressing portion 15 located at the tip of the body 14. Here, the outer circumferential surface of the body 14 is composed of a pair of flat surfaces 14a and semi-cylindrical surfaces 14b that are continuous with each flat surface 14a, while the pressing portion 15 is composed of a semi-cylindrical surface 15a and ellipsoidal surfaces 15b, 15b that are continuous with the semi-cylindrical surface 15a at both ends. The radii of curvature R1, R2 of the curved surfaces 15a, 15b (see Figures 1 to 3) will be described later.

The die 12 has an insertion hole 16 through which the body 14 and the pushing portion 15 of the punch 11 can be inserted. This insertion hole 16 has a notch shape as shown in FIG. 2. In addition, the peripheral edge 17 on the side of this insertion hole 16 where the punch 11 begins to pass has a convex curved shape over its entire circumferential area, and the curvature of the peripheral edge 17 is relatively small on the side closer to the notch portion 16a of the insertion hole 16 and relatively large on the side farther from the notch portion 16a.

In this embodiment, as shown in FIG. 2, the peripheral portion 17 is composed of a constant curvature region 17a with a constant curvature, and a variable curvature region 17b that is continuous with the constant curvature region 17a and is located closer to the cutout portion 16a than the constant curvature region 17a. The curvature in the variable curvature region 17b decreases as it approaches the cutout portion 16a of the insertion hole 16, in other words, increases as it moves away from the cutout portion 16a. Therefore, the radii of curvature R3 to R6 of the peripheral portion 17 are maximum (radius of curvature R6 shown in FIG. 3) on the side closest to the cutout portion 16a, i.e., the end of the cutout side of the peripheral portion 17, and are minimum (radius of curvature R3 shown in FIG. 4(a)) on the side furthest from the cutout portion 16a, here in the constant curvature region 17a of the peripheral portion 17.

Here, we will explain the relationship between the radii of curvature R1, R2 of the curved surfaces 15a, 15b in the pushing portion 15 of the punch 11 and the radii of curvature R3 to R6 of the curved surfaces 17a, 17b in the peripheral portion 17 of the die 12.

For example, as shown in FIG. 1, when comparing the radius of curvature R1 of the contour of the ellipsoidal surface 15b of the pressing portion 15 of the punch 11 when viewed from the front direction with the radius of curvature R3 of the constant curvature region 17a of the peripheral portion 17 of the die 12 (see FIG. 4(a)), the magnitudes of the radii of curvature R1 and R3 are set so that R1>R3.

For example, as shown in FIG. 3, when the radius of curvature R2 of the contour of the ellipsoidal surface 15b of the pressing portion 15 of the punch 11 is viewed from the side direction, the radius of curvature R6, which is the maximum radius of curvature in the curvature variable region 17b of the peripheral portion 17 of the die 12, is compared, the magnitudes of the radii of curvature R2 and R6 are set so that R2 < R6.

The pad 13 is disposed above the die 12 and on the outside of the punch 11. This pad 13 presses the plate material W placed on the die 12 toward the die 12, thereby making it possible to hold the plate material W at a predetermined position on the die 12.

Next, an example of a method for evaluating edge elongation of a sheet material W using the evaluation device 10 configured as described above will be described mainly with reference to Figures 5 to 7.

First, as shown in FIG. 1, the plate material W to be evaluated is placed at a predetermined position on the die 12, and the plate material W is held at the position by the pad 13. Then, the punch 11 is lowered to press the pressing portion 15 against the plate material W. As a result, as shown in FIG. 5(a) and (b), a part of the plate material W starts to deform according to the tip shape of the pressing portion 15 (more precisely, the shape of each curved surface 15a, 15b). At this point, the plate material W is mainly pressed against the pressing portion 15 (semi-cylindrical surface 15a and ellipsoidal surface 15b) of the punch 11, and is not substantially in contact with the peripheral portion 17 of the die 12, particularly the side of the curvature variation region 17b with a smaller curvature (the side close to the notch portion 16a). In other words, the plate material W is not yet pressed against the region of the peripheral portion 17 with a relatively smaller curvature.

After the punch 11 starts bending the plate material W as described above, the punch 11 is continued to be pressed in, and the plate material W continues to be bent. Figures 6(a) and (b) show the state in which the punch 11 is pressed in and the plate material W is further bent from the state shown in Figure 5. As shown in these figures, as the punch 11 is pressed in deeper, the plate material W is deformed into a shape that follows the predetermined contour of the pressing portion 15 of the punch 11, and the pressed and bent portion Wa gradually changes to an upright orientation relative to the non-deformed portion of the plate material W. Therefore, the edge portion W1 of the pressed and bent portion Wa gradually changes its posture from the horizontal direction to a downward direction. In Figure 6, the edge portion W1 is in a state of being directed diagonally downward. At this point, the plate material W is mainly pressed against the pressing portion 15 of the punch 11 (semi-cylindrical surface 15a and spheroidal surface 15b), and the plate material W has not yet been pressed against the area of the peripheral portion 17 where the curvature is relatively small. On the other hand, a portion of the plate material W is pressed against the area of the peripheral portion 17 where the curvature is relatively large (constant curvature area 17a), which allows the plate material W to be bent relatively easily.

Then, the punch 11 continues to press the sheet material W, and the pressing portion 15 located at the tip of the punch 11 completely presses the sheet material W, so that the sheet material W separates from the pressing portion 15 and is pressed against the outer circumferential surface of the body portion 14 of the punch 11. Thus, the sheet material W is finally formed into a shape that conforms to the outer circumferential surface of the body portion 14 (particularly the semi-cylindrical surface 14b), and is bent in a direction perpendicular to the non-deformed portion of the sheet material W (see FIG. 7(b)). At this point, the edge W1 of the bent portion Wa is directed downward, so that when the bent portion Wa of the sheet material W is viewed from the horizontal direction, the edge W1 is not visible (see FIG. 7(a)). At this point, the sheet material W is also pressed against the area of the peripheral edge 17 where the curvature is relatively small, but since the sheet material W has already been pressed and bent to its final state, the part pressed against the area of the relatively small curvature, in this case both ends Wa1 of the bent part Wa, does not stretch significantly. On the other hand, the edge W1 of the bent part Wa is curved and deformed to follow the specified contour of the pressing part 15 of the punch 11 as shown in Figure 8, so the edge W1 as a whole is stretched significantly along the longitudinal direction of the edge W1.

As described above, according to the sheet material edge elongation evaluation device 10 of this embodiment, attention is paid to the shape of the peripheral portion 17 of the through hole 16 formed in the shape of a notch in the die 12 as a concave mold, and the peripheral portion 17 is made to have a convex curved shape over its entire area, and the curvature of the peripheral portion 17 is made to differ in the circumferential direction. Specifically, the shape of the peripheral portion 17 is set so that the curvature of the peripheral portion 17 is relatively small on the side closer to the notch portion 16a of the through hole 16 and relatively large on the far side. According to this configuration, when the sheet material W is bent by pressing the punch 11, both ends Wa1 of the bent portion Wa or the portions nearby are deformed while being pressed against the area of the peripheral portion 17 of the through hole 16 formed in the die 12 with a relatively small curvature (here, the notch portion 16a side of the curvature variable area 17b). In this embodiment, the plate material W is bent without substantial contact until halfway through the pressing process. On the other hand, the portion of the bent portion Wa away from both ends Wa1 is deformed while being pressed against the area of the peripheral portion 17 of the insertion hole 16 with a relatively large curvature. Therefore, while the plate material W can be easily bent by pressing the punch 11, as shown in Figures 9 and 10, the elongation occurring at both ends Wa1 of the bent portion Wa of the plate material W can be suppressed compared to the case where the curvature of the peripheral portion 54 of the insertion hole 53 is a constant shape in the circumferential direction. As a result, the area other than the circumferential end of the edge portion W1 (substantially equal to both ends Wa1 of the bent portion Wa) can be relatively stretched, so that the elongation of the edge portion W1 is prevented from concentrating at the circumferential end, and the elongation characteristics of the edge portion W1 can be properly evaluated.

In addition, by making the insertion hole 16 elongated as in this embodiment, the peripheral portion 17 of the insertion hole 16 also has a shape similar to that of an elongated hole. This ensures the dimensions required for bending (bending and stretching) the plate material W and allows the plate material W to be bent effortlessly, which more reliably avoids uneven stretching of the edge portion W1 and makes it possible to more accurately evaluate the stretch characteristics of the edge portion W1.

Although one embodiment of the present invention has been described above, the sheet material edge elongation evaluation device and sheet material edge elongation evaluation method using this device according to the present invention can have configurations other than those described above, as long as they do not deviate from the spirit of the device.

For example, in the present embodiment, as shown in Figures 2 and 4, the curvature of the peripheral portion 17 is a constant curvature region 17a in the circumferential direction far from the cutout portion 16a, and the remaining circumferential region close to the cutout portion 16a is a variable curvature region 17b, but of course this is not limited to this. For example, the peripheral portion 17 may be configured only with the variable curvature region 17b, so that the curvature decreases as the peripheral portion 17 approaches the cutout portion 16a, with the boundary being the widthwise center position farthest from the cutout portion 16a.

In addition, in this embodiment, the shape of the insertion hole 16 is illustrated as an elongated hole having a portion with a constant width dimension and semicircular portions continuing from both ends of the portion (see FIG. 2), but of course other shapes are also possible. For example, as shown in FIG. 10, the insertion hole 16 may be a perfect circle. In this case, the body portion 14 and the pushing portion 15 of the punch 11 are set to an appropriate shape according to the shape of the insertion hole 16.

10 Evaluation device 11 Punch 12 Die 13 Pad 14 Main body 14a Flat surface 14b Semi-cylindrical surface 15 Pressed portion 15a Semi-cylindrical surface 15b Spheroidal surface 16 Insertion hole 16a Cutout portion 17 Peripheral edge portion 17a Constant curvature region 17b Variable curvature region 50 Evaluation device 51 Die 52 Punch 53 Insertion hole 54 Peripheral edge portion R1 to R6 Radius of curvature W Plate material W1 Edge portion Wa Pressed and bent portion Wa1 End portion

Claims (1)

A plate material edge elongation evaluation device includes a convex mold and a concave mold, and is configured to evaluate the elongation of a plate material edge when the edge of the plate material is bent by pressing an edge of the plate material between the convex mold and the concave mold with a pressing part located at a tip of the convex mold,
the concave mold has an insertion hole into which the pushing portion of the convex mold can be inserted, and the insertion hole has a notch shape;
A device for evaluating the edge elongation of a sheet material, characterized in that the peripheral portion of the insertion hole on the insertion start side has a convex curved shape over its entire area, and the curvature of the peripheral portion is relatively small on the side closer to the cutout portion of the insertion hole and relatively large on the side farther from the cutout portion.

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