JP7435569B2 - Punch for 3-point bending evaluation test and 3-point bending evaluation test method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a three-point bending evaluation test method for parts for evaluating the collision performance of automobile parts, and a punch used in the method.

In recent years, in the automobile field, collision safety standards have become stricter from the perspective of passenger protection, and there is a strong demand for the expansion of the application of high-strength steel and the development of vehicles with excellent collision safety performance. In order to design car bodies with excellent collision safety, each automobile company conducts actual vehicle crash tests using one car body. At the stage of designing module parts, evaluations are often performed by bending tests on each part in order to reduce cost and delivery time, or to simplify the evaluation target. When performing a bending evaluation test on a part-by-part basis, it is important that the test method tests the target part under the same restraint conditions and deformation mode as in the actual vehicle crash test.

The types of collisions in automobile parts can be roughly divided into bending crushing, which involves bending deformation in the axial direction of the part, and axial crushing, in which the part deforms under load in the axial direction. Of the above two types of collisions, bending crushing is a deformation mode in which a collision load is applied to the side surface of a structural member and bends it into a dogleg shape, and occurs in parts such as the B-pillar and side sill in a side collision. For example, when conducting a test to evaluate side collisions of the B-pillar, in the event of an actual vehicle collision, restraint is applied due to deformation resistance from surrounding parts such as roof rails and lockers that connect to the B-pillar. Therefore, a simple three-point bending evaluation test in which a punch is pushed between two supports often fails to reproduce the boundary conditions in an actual vehicle collision.
Therefore, when performing the above-mentioned bending test on a part-by-part basis, it is necessary to perform the test using a test method that appropriately applies translational and rotational restraints to both ends of the part in the axial direction. The simplest method is a test method in which both ends of the evaluation member are completely fixed and a punch is pushed into an arbitrary location on the evaluation member. It is thought that if the above-described three-point bending evaluation test with complete fixation is performed, a certain evaluation can be performed at least in the low stroke region at the initial stage of deformation. Regarding the deformation mode, when testing is performed using a simple punch with only a flat plate or a convex curved surface, the buckling deformation of the vertical wall progresses significantly immediately after the punch hits the top plate, and the mode is mainly composed of cross-sectional collapse. There are likely to be many cases where this happens.
However, some actual parts are designed to prevent cross-section collapse by applying reinforcement or patches to the hollow cross-section. For such parts, in order to reproduce the bending deformation mode that does not cause cross-sectional collapse using a simple hat member, it is necessary to devise a testing method.

In Patent Document 1, a three-point bending evaluation test is conducted on a hat component in which a patch is provided on a bending ridgeline in order to improve collision load. Patent Document 2 proposes a test method in which the tensile load applied to both ends of a component during three-point bending deformation is controlled in accordance with the stroke of an indenter such as an actuator.

JP2014-87848A Japanese Patent Application Publication No. 2018-194446

The above conventional technology has the following problems.
The three-point bending evaluation test method of Patent Document 1 is a simple three-point bending test, and there is no description of a test method for suppressing cross-sectional collapse. Furthermore, although the three-point bending evaluation test method of Patent Document 2 has a high degree of freedom in adjusting each translational and rotational constraint and is likely to be able to reproduce the target boundary conditions, there is no mention of measures to suppress cross-sectional collapse. , large-scale equipment is required, the cost of introduction is high, and opportunities for implementation are likely to be limited.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a three-point bending evaluation test method that realizes a bending deformation mode that suppresses cross-sectional collapse in a hat member, and a punch used therein.

The inventors conducted extensive experiments and studies in order to solve the above problems. As a result, by using a bending test punch with a concave cross-sectional shape that is hollowed out with the same dimensions as the cross-sectional shape of the outside of the hat-shaped part of the evaluation member, it is possible to perform a three-point bending evaluation test in a bending deformation mode that suppresses cross-sectional collapse. I found out.

The three-point bending evaluation test punch according to the present invention, which advantageously solves the above problems, is constructed as follows.
[1] The punch according to the present invention is a punch having a concave cross-sectional shape along the outer surface of the evaluation member, and includes a top plate contact portion forming the bottom of the recess, and a pair of side wall pressing portions forming the side walls of the recess. The top plate contact portion is configured to apply a load to the top plate portion of the evaluation member, and the side wall pressing portion is configured to apply a load to each of the side wall portion of the evaluation member and the flange portion of the evaluation member. is configured to multiply.
[2] In the above [1], the surface of the top plate contact portion that contacts the top plate portion has a curved surface having a convex circular arc cross section in the longitudinal direction of the evaluation member, and the side wall holding portion is connected to the flange portion. The contacting surface may have a curved surface having a convex arc cross section in the longitudinal direction of the evaluation member.
[3] In the above [1] or [2], the punch having the concave cross-sectional shape may have a structure in which the width, depth, or opening angle of the concave portion can be adjusted.
[4] In [1] to [3] above, the evaluation member includes a top plate portion, a pair of side wall portions that are present on both sides of the top plate portion in the width direction, and a flange that is present at the ends of the side wall portions in the width direction. A hollow member having a closed cross-sectional shape can be formed by a hat-shaped member consisting of a hat-shaped member and a bottom plate portion disposed opposite to the top plate portion and overlapping with the flange portion.

The three-point bending evaluation test method according to the present invention, which advantageously solves the above problems, is configured as follows.
[5] A three-point bending evaluation test method in which the punch for three-point bending evaluation test according to any one of [1] to [4] above is used, and a load is applied by making the recessed part of the punch straddle the evaluation member. be.
[6] In [5] above, using any two locations in the longitudinal direction of the evaluation member as fulcrums, move any one location between the two fulcrums from the top plate to the bottom plate of the evaluation member. A load can be applied to the evaluation member with the punch in the direction of .

According to an aspect of the present invention, a three-point bending evaluation test is performed to determine a bending deformation mode that suppresses cross-sectional collapse of a hat member, which is simpler and more in line with actual conditions than conventional methods in evaluating the collision performance of automobile parts. Since it can be realized by the method and the punch used in the method, it can lead to the development of automobile parts with excellent collision performance.

It is an example of the test piece shape of the evaluation member used in the three-point bending evaluation tester, (a) represents a side view of the hat-shaped evaluation member, and (b) represents the A-A of the hat-shaped evaluation member in the diagram (a). Represents a cross-sectional view. (a) is a schematic side view showing an example of a test mechanism suitable for use in the three-point bending evaluation test method of the present invention, (b) is a BB sectional view of (a), and (c) is a concave cross section. FIG. 3(d) shows a perspective view of the shaped punch, and (d) shows a front view of the concave cross-sectional shaped punch. 1 is an example of the structure of a punch with a concave cross-section according to an embodiment of the present invention, in which (a) represents a schematic front view showing a component configuration, and (b) represents a top view of a fixing part. It is an explanatory view of a hat-shaped evaluation member. It is an explanatory view of the concave cross section of the concave cross-sectional shape punch. FIG. 3 is a schematic side view showing a comparison of bending deformation modes in a three-point bending evaluation test, in which (a) is a test No. 1 using a concave cross-sectional punch; 1, and (b) shows test No. 1 using an R100 convex punch. The case of 9 is shown. It is a schematic sectional view showing the deformation state of the evaluation member at a test stroke of 30 mm by a punch with a changed cross-sectional shape, and is a schematic cross-sectional view showing the deformation state of the evaluation member with a test stroke of 30 mm. Cases 2 to 6 are shown. It is a schematic sectional view showing the deformation state of the evaluation member at a test stroke of 30 mm by a punch with a changed cross-sectional shape, and is a schematic cross-sectional view showing the deformation state of the evaluation member with a test stroke of 30 mm. Cases 7, 8, 10 and 11 are shown.

Embodiments of the present invention will be described in detail below.
The three-point bending evaluation test method of this embodiment has a closed cross-sectional shape with a top plate 1, a pair of side walls 2 continuous on both sides of the top plate 1 in the width direction, and a bottom plate X disposed opposite to the top plate. Assuming that the hollow member that constitutes the evaluation member S (Fig. 1) is the evaluation member S (Fig. 1), any two points in the longitudinal direction of the hollow member (fixed part in Fig. 2 (a)) are fulcrums, and any point between the two fulcrums is This is a test method using a punch 3 with a concave cross-section, in which the punch 3 is pushed into one location from the top plate part 1 toward the bottom plate part X.
As the evaluation member S, for example, a hat-shaped hollow member is shown in FIG.
An example of the test mechanism is shown in Figure 2(a). In the three-point bending evaluation test, the evaluation member ends 4 joined to both ends of the evaluation member S are completely fixed to the testing machine 5, and a location of the evaluation member S is punched in the direction from the top plate part 1 to the bottom plate part X. Push it in.

Concave cross-sectional punch In the example of FIG. 2, the punch 3 has a concave cross-sectional shape hollowed out with the same dimensions as the cross-sectional shape of the outside of the hat portion of the evaluation member S. As shown in FIG. 2, the concave cross-sectional punch 3 is designed to be set so as to sandwich and straddle the hat portion of the evaluation member S for testing. The top plate contacting part 6 of the concave cross-sectional shape punch 3 constitutes the bottom of the recess, and the punch 3 is pushed in the direction from the top plate part 1 of the hat-shaped test piece toward the bottom plate part X, that is, in the bending evaluation test, the hat-shaped test piece is This is the part that applies a load to the top plate part 1 of. The surface of the top plate contact portion 6 that comes into contact with the top plate portion 1 is a curved surface having a convex arc cross section in the longitudinal direction of the evaluation member S (FIGS. 2(a) and 2(c)).
The side wall holding portions 7 of the concave cross-sectional punch 3 constitute the side walls of the recess, and are a pair of portions that apply loads to the side wall portion 2 and the flange portion F of the hat-shaped test piece, respectively, in the bending test. The surface 8 where the side wall pressing portion 7 contacts the flange portion F is a curved surface having a convex arc cross section in the longitudinal direction of the evaluation member S (FIGS. 2(a) and 2(c)). Here, the flange portion F refers to the portion of the hat-shaped test piece shown in FIG. 1 that overlaps with the bottom plate portion X. Regardless of the length of the flange in the width direction, even if there is no flange and the part is warped, that part is considered to be the flange part F.

The concave cross-sectional shape punch 3 has a structure in which the depth, width, opening angle, etc. of the concave portion of the cross-sectional shape can be adjusted to match the cross-sectional shape of the evaluation member S, or to allow for the amount of cross-sectional collapse. It is preferable that there be. FIG. 3 shows an example of the structure of the punch 3 having a concave cross-section. The depth 10 of the recess can be adjusted by the thickness of the depth adjustment spacer 13 used at the lower part of the top plate contact portion 6. In addition, by adjusting the fixing position between the side wall holding parts 7 and the fixing part 11 on both sides using the elongated holes 14 of the fixing part 11, and using the width adjustment spacer 12 in the gap with the top plate contact part 6, the concave part can be adjusted. Width 9 can be adjusted. If the width adjustment spacer 12 is tapered, the opening angle of the recess can be changed.

The cross-sectional shape of the concave cross-sectional punch 3 is preferably such that when the punch 3 contacts the top plate portion 1 of the evaluation member S during the test, the gap between the side wall portion 2 and the punch 3 is 1 mm or less. Further, it is preferable that the depth 10 of the concave cross section is 50% or more of the height of the evaluation member S. In addition, when it is desired to conduct a test in a deformation mode that intentionally causes a certain amount of cross-sectional collapse of the evaluation member S during the test, the depth 10 of the gap or recess between the side wall portion 2 and the punch 3 may be adjusted. It is preferable that the cross-sectional shape is In addition, the length of the punch 3 having a concave cross-sectional shape in the longitudinal direction of the evaluation member S is set together with the curvature of the arcuate cross section of the curved surface of the top plate contact portion 6 and side wall holding portion 7 to prevent cross-sectional collapse from occurring during the bending evaluation test. .

3-Point Bending Evaluation Test Method As shown in FIG. 2, the end portion 4 of the evaluation member is fixed to the testing machine 5 and completely restrained. In the middle of the evaluation member S supported at two points in this way, the top plate contacting part 6 and the side wall pressing part of the concave cross-sectional punch 3 are placed in the direction from the top plate part 1 to the bottom plate part X, which is the punching direction of the testing machine 5. At step 7, the concave cross-sectional punch 3 is set so as to straddle the evaluation member S so as to cover the evaluation member S.
Bending test of concave cross-sectional punch 3 A bending evaluation test is carried out by moving the punch 3 from the top plate part 1 to the bottom plate part X direction, which is the operating direction.

A three-point bending evaluation test using a concave cross-sectional punch was conducted.
A hat-shaped member was used as the evaluation member.
L (longitudinal length of evaluation member) = 600mm
H (height of evaluation member) = 60mm
W1 (width of top plate part of evaluation member) = 60mm
W2 (width of the bottom plate part of the evaluation member) = 104mm
It is the size of

A three-point bending CAE (Computer Aided Engineering) analysis was performed based on the above embodiment. The punch speed was 2 m/s. The hat shape and punch of the evaluation member S were set to the conditions shown in Table 1 and analyzed. FIG. 4 shows an explanatory diagram of the width 16 and side wall angle 15 in the hat-shaped row of evaluation members in Table 1. Width 16 is the distance between the outsides of the side walls on both sides (when the side wall angle 15 is 90°) or the distance between the round ends of the side wall chamfers on the ridge line between the top plate and the side wall (when the side wall angle 15 is other than 90°). (case). The side wall angle 15 is determined by the angle between the side wall and the top plate. FIG. 5 shows an explanatory diagram of terms in the punch column of Table 1. "Concave" in the row of punches means a concave punch that is hollowed out to match the hat-shaped cross-sectional shape of the evaluation member S. In addition, the "opening angle 17" is determined by the angle between the top plate contact part 6 and the inner surface of the side wall holding part 7, that is, the opening angle of the recess, and the "width" is the shortest distance between the straight parts of the recessed part of the side wall holding part, In other words, it is determined by the recess width 9. The "depth" is determined by the hollowed-out recess depth 10. "R100 punch" means a punch having a convex partially cylindrical surface with a radius of curvature R=100 mm. "Only the side wall holding part" means that the punch has only the side wall holding part, that is, no load is applied to the top plate part of the evaluation member S. “Only the flange portion + top plate contact portion” means a punch having only the portion that contacts the flange portion and the top plate contact portion, that is, does not restrict the deformation of the side wall portion of the evaluation member.

FIG. 6 shows a side view of the bending deformation of the evaluation member at test strokes of 0 mm and 30 mm, obtained by analysis of the invention example (Test No. 1) and the comparative example (Test No. 9). In addition, in the punch shown in the figure of the invention example (Test No. 1), the side wall pressing part on the near side of the paper was hidden. As shown in the comparative example (Test No. 9), in the case of a punch with only an R shape, cross-sectional collapse progressed significantly at a stroke of 30 mm, and only the top plate area was deformed, and sufficient bending deformation did not occur in the bottom plate area. . On the other hand, as shown in the invention example (Test No. 1), by using a punch with a concave cross-section, the entire evaluation member from the top plate to the bottom plate was bent and deformed without collapsing the cross section.
7 and 8 show the cross-sectional shape of the evaluation member at the punch position when the test stroke was 30 mm under punching conditions other than those shown in FIG. 6. As shown in Figures 7 and 8, when punching only the side wall holding part in the comparative example (Test No. 10) or only the flange part and top plate contact part in the comparative example (Test No. 11), cross-sectional collapse occurred. On the other hand, in the case of the invention examples (Test Nos. 2 to 8), bending deformation was achieved in which cross-sectional collapse was suppressed.

The punch for three-point bending evaluation test and the three-point bending evaluation test method of the present invention can be used for the development of steel plates, parts, and steel plate forming methods that require excellent crash performance for automobile parts.

S: Evaluation member X: Bottom plate portion F: Flange portion of evaluation member L: Longitudinal length of evaluation member H: Height of evaluation member W1: Width of top plate portion of evaluation member W2: Width of bottom plate portion of evaluation member 1: Top plate part of the evaluation member 2: Side wall part of the evaluation member 3: Punch with concave cross-sectional shape 4: End part of the evaluation member 5: Testing machine 6: Top plate contact part of the punch 7: Punch side wall holding part 8: Flange of the punch Contact surface 9: Punch recess width 10: Punch recess depth 11: Fixed part
12: Width adjustment spacer 13: Depth adjustment spacer
14: Elongated hole for width adjustment 15: Side wall angle of evaluation member 16: Width of evaluation member 17: Punch recess opening angle

Claims (6)

A punch having a concave cross-sectional shape along the outer surface of the evaluation member,
a top plate contact portion forming a bottom of the recess; a pair of side wall holding portions forming side walls of the recess;
Equipped with
The top plate contact portion is configured to apply a load to the top plate portion of the evaluation member,
The side wall pressing part is a three-point bending evaluation test punch configured to apply a load to each of the side wall part of the evaluation member and the flange part of the evaluation member. The surface of the top plate contact portion that contacts the top plate portion has a curved surface having a convex circular arc cross section in the longitudinal direction of the evaluation member, and the surface of the side wall presser portion that contacts the flange portion has a curved surface that is a convex arc cross section in the longitudinal direction of the evaluation member. The punch for three-point bending evaluation test according to claim 1, having a curved surface having a convex arc cross section in the longitudinal direction. The punch for three-point bending evaluation test according to claim 1 or 2, wherein the punch having the concave cross-sectional shape has a structure in which the width, depth, or opening angle of the concave portion can be adjusted. The evaluation member includes a hat-shaped member consisting of a top plate, a pair of side walls located on both sides of the top plate in the width direction, and a flange part located at the ends of the side walls in the width direction, and the top plate part. The three-point bending evaluation test punch according to any one of claims 1 to 3, wherein the punch is a hollow member having a closed cross-sectional shape with a bottom plate portion that is arranged opposite to the bottom plate portion and overlaps with the flange portion. A three-point bending evaluation test method, using the punch for three-point bending evaluation test according to any one of claims 1 to 4, and applying a load by making the recessed part of the punch straddle the evaluation member. The evaluation is performed using the punch in the direction from the top plate portion of the evaluation member to the bottom plate portion of the evaluation member, using any two points in the longitudinal direction of the evaluation member as fulcrums, and an arbitrary point between the two fulcrums. The three-point bending evaluation test method according to claim 5, wherein a load is applied to the member.

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