Sheet edge elongation evaluation device

Abstract

To enable proper evaluation of elongation characteristic of an edge part of a plate regardless of an edge shape thereof.SOLUTION: An evaluation device 10 of an edge W1 elongation of a plate W comprises a convex type 11 and a concave type 12. The concave type 12 includes an insertion hole 16 into which a push-in part 15 of the convex type 11 can be inserted. The insertion hole 16 is a notch configuration where a peripheral edge part 17 of the insertion hole 16 at the insertion start side is a convex surface over the whole area. Curvature of the peripheral edge part 17 is relatively small at the portion near the notch part 16a of the insertion hole 16, and relatively large at the portion far from the notch part 16a.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an edge elongation evaluation device for a sheet material. [Background technology]

[0002] For example, in the manufacturing process of automobile parts, a metal plate is pressed multiple times to form the plate into a desired shape. At this time, attention should be paid to the elongation that occurs at the edge of the plate during the press processing. That is, if the elongation of the edge of the plate exceeds an allowable amount, there is a high possibility that defects such as cracks will occur at the end face of the edge, so attention should be paid to the elongation characteristics of the edge when designing the product.

[0003] 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 predetermined size is prepared, and a punch with a tapered surface at a predetermined angle on the outer periphery of the tip is pressed into the hole of the plate material, bending the peripheral part of the hole all around and expanding the hole. This causes elongation in the peripheral part of the hole. Therefore, it is possible to evaluate the elongation characteristics of the edge of the plate material by evaluating, for example, the limit elongation amount at which cracks occur on the end face of the peripheral part of the hole (in Patent Document 1, the height of the peripheral part after bending). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Re-tabled publication 2016 / 92657 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when evaluating the elongation characteristics of the above-mentioned sheet 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 Figs. 9 and 10, the sheet W is placed so as to cover half of an insertion hole 53 of a punch 52 provided in a die 51, and the punch 52 is pressed toward the sheet W. In this case, a semicircular portion Wa including the edge W1 of the sheet W is pressed and bent with a predetermined elongation (see Fig. 11). However, in such a method, the elongation (strain) is concentrated at both ends Wa1 of the pressed and bent portion (semicircular portion Wa), and the portion that is really to be evaluated (in Fig. 11, the edge W1 at the circumferential center of the semicircular portion Wa) hardly elongates. This makes it difficult to generate differences in elongation between sheets, making it difficult to properly evaluate the elongation characteristics of the sheet.

[0006] In view of the above circumstances, the technical problem to be solved in this specification is to be able to properly evaluate the elongation characteristics of an edge of a plate material regardless of the edge shape. [Means for solving the problem]

[0007] The above-mentioned problems are solved by the edge elongation evaluation device for sheet material according to the present invention. That is, in the evaluation device for evaluating edge elongation of sheet material, which includes a convex mold and a concave mold, and which evaluates the elongation of the edge when the edge of a sheet material placed between the convex mold and the concave mold is pressed in by 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.

[0008] In this way, the present invention focuses on the shape of the peripheral portion of the insertion hole formed in the shape of a notch in the concave mold, and the peripheral portion is made to have a convex curved shape over its entire area, and the curvature of the peripheral portion is made to differ 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 insertion hole and relatively large on the side farther away. With this configuration, when the plate material is pressed and bent by pressing the convex mold, both ends of the portion to be pressed and bent are deformed while being pressed against the area of ​​the peripheral portion of the insertion hole formed in the concave mold with a relatively small curvature. Meanwhile, the portion away from both ends of the portion to be pressed and bent (for example, the center side in the width direction on the base end side of the portion to be pressed and bent) is deformed while being pressed against the area of ​​the peripheral portion of the insertion hole with a relatively large curvature. Therefore, while the plate material can be easily bent by pressing the punch, the elongation occurring at both ends of the bent portion of the plate material can be suppressed compared to the case where the curvature of the peripheral portion 54 of the insertion hole 53 is constant in the circumferential direction, for example as shown in Figure 10. This allows the regions other than both ends of the edge to be relatively stretched, so that the edge elongation is prevented from concentrating at a specific point, and the elongation characteristics of the edge can be properly evaluated. Effect of the Invention

[0009] As described above, the sheet material edge elongation evaluation device according to the present invention makes it possible to properly evaluate the elongation characteristics of the edge of the sheet material regardless of the edge shape. [Brief description of the drawings]

[0010] [Figure 1] 1 is a front view of an apparatus for evaluating edge elongation of a plate material according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view of the evaluation device shown in FIG. [Diagram 3] 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. [Figure 4] 3A is a cross-sectional view taken along line B1-B1 of the evaluation device shown in FIG. 2, FIG. 3B is a cross-sectional view taken along line B2-B2 of the evaluation device shown in FIG. 2, and FIG. 3C is a cross-sectional view taken along line B3-B3 of the evaluation device shown in FIG. [Diagram 5]FIG. 3 is a diagram for explaining an example of a method for evaluating the edge elongation of 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. [Figure 6] FIG. 3 is a diagram for explaining an example of a method for evaluating the edge elongation of sheet material using the evaluation device shown in FIG. 1 and FIG. 2, and shows (a) a view taken along 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 B1-B1. [Figure 7] FIG. 3 is a diagram for explaining an example of a method for evaluating the edge elongation of 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 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 cross-sectional view taken along the line B1-B1. [Figure 8] 8 is a view of the bent portion of the plate material shown in FIG. 7 as viewed from an oblique direction. [Figure 9] FIG. 2 is a front view of an edge elongation evaluation device for a plate material for comparison with the present invention. [Figure 10] FIG. 10 is a plan view of the evaluation device shown in FIG. [Figure 11] 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. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the details of an edge elongation evaluation device for a plate material according to one embodiment of the present invention will be described with reference to the drawings.

[0012] FIG. 1 shows a front view of an edge elongation evaluation device 10 for sheet material according to one embodiment of the present invention. FIG. 2 shows a plan view of the evaluation device 10 shown in FIG. 1. As shown in these figures, the evaluation device 10 includes a punch 11 as a convex mold, a die 12 as a concave mold, and a pad 13. Details of each element will be described below, focusing on the configuration of the die 12. Note that the pad 13 is omitted in the figures other than FIG. 1 for the purpose of making it easier to understand the contents shown in the figures.

[0013] In addition, in Figures 1 and 2, in order to equalize the pushing mode of the punch 11, two dies 12 are installed adjacent to each other for one punch 11, and a plate material W is placed on each die 12.

[0014] The punch 11 is used to press and bend the sheet material W to be evaluated, and in this embodiment, has a main body 14 having an oval cross section and a pressing part 15 located at the tip of the main body 14. Here, the outer circumferential surface of the main body 14 is composed of a pair of flat surfaces 14a and semi-cylindrical surfaces 14b continuous with each flat surface 14a, and the pressing part 15 is composed of a semi-cylindrical surface 15a and ellipsoidal surfaces 15b, 15b continuous with both ends of the semi-cylindrical surface 15a. The radii of curvature R1, R2 (see Figs. 1 to 3) of the curved surfaces 15a, 15b will be described later.

[0015] The die 12 has an insertion hole 16 through which the body 14 and the push-in portion 15 of the punch 11 can be inserted. This insertion hole 16 has a notch shape, as shown in Fig. 2. Furthermore, a peripheral edge portion 17 of this insertion hole 16 on the side where the punch 11 starts to pass has a convex curved shape over its entire circumferential range, and the curvature of the peripheral edge portion 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.

[0016] In this embodiment, as shown in Fig. 2, the peripheral portion 17 is composed of a constant curvature region 17a having 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 portion on the cutout side of the peripheral portion 17, and are minimum (radius of curvature R3 shown in Fig. 4(a)) on the side farthest from the cutout portion 16a, here, in the constant curvature region 17a of the peripheral portion 17.

[0017] Here, the relationship between the radii of curvature R1 and R2 of the respective curved surfaces 15a and 15b in the pushing portion 15 of the punch 11 and the radii of curvature R3 to R6 of the respective curved surfaces 17a and 17b in the peripheral portion 17 of the die 12 will be described.

[0018] For example, as shown in FIG. 1, when comparing the radius of curvature R1 of the contour when viewed from the front direction of the rotating elliptical surface 15b provided in the pushing portion 15 of the punch 11 with the radius of curvature R3 (see FIG. 4(a)) in the constant-curvature region 17a of the peripheral portion 17 of the die 12, the magnitudes of the respective radii of curvature R1 and R3 are set such that R1 > R3.

[0019] Also, for example, as shown in FIG. 3, when comparing the radius of curvature R2 of the contour when viewed from the side direction of the rotating elliptical surface 15b provided in the pushing portion 15 of the punch 11 with the radius of curvature R6, which is the maximum value of the radius of curvature in the curvature-varying region 17b of the peripheral portion 17 of the die 12, the magnitudes of the respective radii of curvature R2 and R6 are set such that R2 < R6.

[0020] The pad 13 is disposed above the die 12 and outside the punch 11. By pressing the plate material W placed on the die 12 toward the die 12, the pad 13 enables the plate material W to be held at a predetermined position on the die 12.

[0021] Next, an example of a method for evaluating the edge elongation of the plate material W using the evaluation apparatus 10 having the above configuration will be mainly described with reference to FIGS. 5 to 7.

[0022] 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.

[0023] After the punch 11 starts bending the sheet material W as described above, the punch 11 is pressed further in to continue bending the sheet material W. Figures 6(a) and 6(b) show the state in which the punch 11 continues to be pressed in and the sheet material W is further bent from the state shown in Figure 5. As shown in these figures, as the punch 11 is pressed deeper, the sheet material W is deformed into a shape following a predetermined contour of the pressing part 15 of the punch 11, and the pressed and bent part Wa gradually changes to an upright orientation relative to the non-deformed part of the sheet material W. Therefore, the edge part W1 of the pressed and bent part Wa gradually changes its posture from the horizontal direction to a downward direction. In Figure 6, the edge part W1 is in a state of being directed obliquely downward. At this point, the sheet material W is mainly pressed against the pressing part 15 of the punch 11 (semi-cylindrical surface 15a and spheroidal surface 15b), and the sheet material W has not yet been pressed against the region of the peripheral part 17 where the curvature is relatively small. On the other hand, a part of the plate material W is pressed against the region of the peripheral portion 17 where the curvature is relatively large (constant curvature region 17a), and this allows the plate material W to be bent relatively easily.

[0024] 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 following 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 region of the peripheral portion 17 where the curvature is relatively small, but since the sheet material W has already been pressed and bent to its final state, the portion pressed against the region of the relatively small curvature, here both end portions Wa1 of the pressed and bent portion Wa, do not stretch significantly. On the other hand, the edge portion W1 of the pressed and bent portion Wa is curved and deformed following the predetermined contour of the pressing portion 15 of the punch 11 as shown in Fig. 8, so that the edge portion W1 as a whole is stretched significantly along the longitudinal direction of the edge portion W1.

[0025] 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 provided 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 different 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 close to the notch portion 16a of the insertion hole 16 and relatively large on the side far from it. According to this configuration, when the sheet material W is pressed and bent by the pressing of the punch 11, both ends Wa1 of the portion Wa to be pressed and bent or the portions nearby are deformed while being pressed against the region of the peripheral portion 17 of the insertion hole 16 provided in the die 12 with a relatively small curvature (here, the notch portion 16a side of the curvature variable region 17b). In this embodiment, the sheet material W is pressed and bent without substantially contacting each other until the middle of the pressing process. On the other hand, the portions of the bent portion Wa away from both ends Wa1 are deformed while being pressed against the region of the peripheral portion 17 of the insertion hole 16 having a relatively large curvature. Therefore, while the sheet material W can be easily bent by pressing the punch 11, the elongation occurring at both ends Wa1 of the bent portion Wa of the sheet 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 shown in Figures 9 and 10. As a result, the region other than the circumferential ends of the edge portion W1 (substantially equal to both ends Wa1 of the bent portion Wa) can be relatively elongated, so that the elongation of the edge portion W1 is prevented from concentrating at the circumferential ends, and the elongation characteristics of the edge portion W1 can be properly evaluated.

[0026] In addition, by forming the insertion hole 16 in an elongated hole shape 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 pushing and bending (bending and stretching) the plate material W, and allows the plate material W to be pushed and bent without difficulty, thereby more reliably preventing uneven stretching of the edge portion W1 and enabling more appropriate evaluation of the stretch characteristics of the edge portion W1.

[0027] The above describes one embodiment of the present invention, but the sheet material edge elongation evaluation device and sheet material edge elongation evaluation method using this device according to the present invention can also have configurations other than those described above as long as they do not deviate from the spirit of the device.

[0028] For example, in the present embodiment, as shown in Figures 2 and 4, a portion of the circumferential region far from the cutout portion 16a is set as the constant curvature region 17a, and the remaining circumferential region close to the cutout portion 16a is set as the 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 approaches the cutout portion 16a, with the boundary being the widthwise center position farthest from the cutout portion 16a.

[0029] In addition, in the present 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 acceptable. 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 appropriate shapes according to the shape of the insertion hole 16. [Explanation of symbols]

[0030] 10 Evaluation equipment 11 Punch 12 Die 13 Pad 14 Main body 14a flat surface 14b Semi-cylindrical surface 15 Push-in section 15a Semi-cylindrical surface 15b Spheroid 16 Insertion hole 16a Cutout part 17 Periphery 17a Constant curvature region 17b Curvature change area 50 Evaluation device 51 Die 52 Punch 53 Insertion hole 54 Periphery R1~R6 Radius of curvature W plate material W1 Edge Wa Bent part Wa1 End

Claims

[Claim 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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