Bending test apparatus

Abstract

To provide a test apparatus capable of appropriately performing a bending test even on a test piece or the like having a hat-shaped cross section.SOLUTION: A test apparatus (S) according to the present invention includes a pivot shaft (1), a pair of wing bodies (2) that rotates about the pivot shaft, and driving means (3) that actuates the wing bodies. The pair of wing bodies, which is simply supported by a pair of support bodies (4) arranged substantially symmetrically with respect to the pivot shaft, closes or opens when the pivot shaft is pushed or pulled in a substantially-orthogonal vertical direction. By the closing or opening motion of the wing bodies, a test piece attached to the wing bodies is bent. In a case where the test piece has a hat-shaped cross section, when a lower surface of a flange portion thereof is fixed in contact with attachment surfaces of the wing bodies, a bending test can be performed with the lower surface of the flange portion as a neutral surface. The bending test may be performed in a state where end portions are regulated by engagement portions provided on left and right sides of the wing bodies.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bending test device and the like. [Background technology]

[0002] The basic mechanical properties of materials and components are evaluated not only by tensile tests but also by bending tests, which are specified in various standards (e.g., JIS K7171, ISO 178, ASTM D790, etc.).

[0003] However, in many cases, existing standards cannot be applied directly to bending tests using test pieces based on the actual shape of the product. For example, if standardized three-point or four-point bending tests are performed on thin plate molded products used in automobile frames, the part pressed by the indenter will locally deform (collapse), causing the cross-sectional shape of the molded product to collapse, making it impossible to properly evaluate its bending properties.

[0004] Therefore, bending test methods and devices suited to the shape of actual components have been proposed separately from the standard, and relevant descriptions are found in the following patent documents. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2023-49754 [Patent Document 2] Patent Publication No. 2013-217829 [Patent Document 3] Patent Publication No. 2020-85710 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Documents 1 and 2 merely perform conventional three-point bending tests or four-point bending tests by changing the support form of the test piece.

[0007] In Patent Document 3, a compression bending test is performed on a hollow columnar test piece with a closed cross section by pressing both ends of the test piece. In this case, the test piece loses its cross section before buckling, so it is difficult to perform an appropriate evaluation. Furthermore, neither patent document describes the neutral plane that occurs due to bending.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a bending test device or the like having a new structure different from conventional ones. [Means for solving the problem]

[0009] As a result of extensive research, the inventor came up with the idea of ​​using a hinge mechanism to bend the test piece, and by realizing this idea, he succeeded in conducting bending tests appropriately. By expanding on this result, he has completed the present invention, which will be described below.

[0010] Bending test equipment (1) The present invention is a testing device that includes a pivot, a pair of wing bodies that rotate around the pivot, and a driving means for operating the wing bodies, and that can bend a test piece attached to the wing bodies by closing or opening the wing bodies.

[0011] (2) In the bending test device of the present invention (simply referred to as the "test device"), a test specimen attached to a pair of wing bodies that rotate around a pivot is bent by the rotation (closing or opening) of the wing bodies. Therefore, bending tests can be performed on test specimens of various shapes that are difficult to perform three-point bending tests on while suppressing local deformation of the test specimen and collapse of the cross-sectional shape.

[0012] Furthermore, when a bending test is performed by fixing a test specimen to a wing body, the fixing surface of the test specimen does not move relative to the wing body (i.e., displacement or strain is substantially zero), so the fixing surface becomes the neutral plane of bending. Therefore, the testing device of the present invention can also perform bending tests with a preset neutral plane. Therefore, even when evaluating the mechanical properties (bending properties) of approximately symmetrical components (e.g., components whose mating surface is the neutral plane) formed by joining materials of the same shape, it is possible to evaluate the joined structural components by simply performing a bending test on the materials before joining (e.g., one of the materials).

[0013] <Bending test method> The present invention can be understood as a testing method using the above-mentioned testing apparatus. The bending test may be performed by simply bending the test piece with the blade body, or by applying a compressive force or a tensile force (especially a longitudinal load) to the test piece.

[0014] "others" (1) In this specification, unless otherwise specified, the direction in which the pivot axis extends is referred to as the axial direction, and the direction perpendicular to the axial direction is referred to as the left-right direction or the up-down direction. Usually, the horizontal direction is referred to as the left-right direction, and the vertical direction is referred to as the up-down direction.

[0015] For the test specimen attached to the wing body, the axial direction is also called the width direction, the left-right direction is also called the longitudinal direction, and the up-down direction is also called the height direction, and the dimensions in each direction are also called the width, length, or height, respectively.

[0016] (2) Unless otherwise specified, "x to y" in this specification includes a lower limit of x and an upper limit of y. Any numerical value included in the various numerical values ​​or ranges described in this specification may be used as a new lower limit or upper limit to create a new range such as "a to b." [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is an exploded perspective view of a bending test device (one example). [Figure 2] FIG. 2 is a perspective view showing the operation of the bending test device. [Figure 3]This is a photograph showing the state of an actual bending test of a test piece using the bending test device. [Figure 4] 1 is a graph showing an example of the relationship between stroke and load measured by the bending test device. [Figure 5] This is an example of an analysis diagram using CAE for a bending test. DETAILED DESCRIPTION OF THE INVENTION

[0018] The contents described in this specification may apply not only to the test apparatus but also to the test method using the same. One or more components arbitrarily selected from this specification may be added to the components of the present invention. Components related to a method may also be components related to a product. Which embodiment is best depends on the target, required performance, etc.

[0019] Test Equipment The testing device includes a pivot and a pair of blades (wings) that constitute a hinge mechanism, and a driving means for rotating (closing or opening) the blades. These components will be described in detail below.

[0020] (1) Hinge mechanism It is preferable that the pair of wings can rotate symmetrically about the pivot axis. The shape (shape, size, etc.) and structure of the wings are not important, and they do not necessarily have to be symmetrical about the pivot axis.

[0021] The wing body has a mounting surface with which the test piece contacts. The test piece can be attached to the wing body by being fixed so as not to move relative to the wing body, or by being gripped or restrained so as to allow relative movement (sliding, etc.).

[0022] When the test specimen is fixed to the mounting surface of the wing body, the mounting surface can be set (adjusted) as the neutral plane of bending. If the mounting surface of the wing body is on a plane that passes through the approximate center of the pivot, it becomes easier to evaluate (calculate) the load (stress) and deformation (strain).

[0023] The mounting surface is not limited to a flat surface, but may be a curved surface according to the test piece. Furthermore, "fixing" as used in this specification may mean being detachable using a jig (screw) or directly attached (joined by welding or the like).

[0024] The wing body may have engaging portions that restrict the longitudinal ends of the test specimen (on the left and right sides approximately perpendicular to the pivot axis). The engaging portions may hold the test specimen stably in a predetermined position, or may apply additional compressive or tensile forces to the ends of the test specimen when the wing body closes or opens. In the latter case, in addition to the bending moment around the pivot axis, compressive or tensile stresses may act in the longitudinal direction of the test specimen. The engaging portions of the wing body and the ends of the test specimen may be fixed (including joined), or may be gripped or restrained in a way that allows them to slide in a specific direction.

[0025] (2) Driving means The driving means can be any mechanism or driving source as long as it can rotate the wing body around the pivot (closing or opening). For example, if a robot arm or the like is used, the wing body can be precisely driven while adjusting and controlling the displacement (angle) and load.

[0026] The driving means may be a means for pushing or pulling the pivot in a substantially perpendicular vertical direction while restricting the upward or downward movement of the wing body. For example, the driving means may be realized by moving (stroking) the pivot directly using hydraulics or electricity (drive source) or indirectly using a jig or the like. In this case, it is advisable to analytically or experimentally determine in advance the relationship between the stroke and the applied load.

[0027] The support configuration of the wing bodies can be various, for example, a pair of wing bodies may simply be supported by a pair of supports. The supports may be, for example, pillars, spheres, wedges, etc. One or more supports may be provided for each wing body depending on the configuration. When the supports are arranged (i.e., placed) in positions approximately symmetrical with respect to the pivot axis, the mechanical relationship is also symmetrical with respect to the pivot axis, simplifying evaluation and analysis.

[0028] Test piece The test specimen may be any form (shape, size), solid, hollow, or thin plate. The testing device of the present invention can perform an appropriate bending test on a test specimen made of a hat-shaped cross-section, avoiding local deformation (such as collapse of the cross-sectional shape) caused by an indenter or the like. Therefore, the mechanical properties of such a structure can be appropriately evaluated even in a bending test using only one of the hat-shaped cross-sections as the test specimen, without requiring the structure itself to be made of hat-shaped cross-sections joined together with a flange (gripping portion).

[0029] If the test specimen has a gripping portion protruding on the extension side of the pivot, a bending test can be performed with the underside of the gripping portion fixed in contact with the mounting surface of the wing body, allowing bending evaluation with the underside of the gripping portion as the neutral plane. The gripping portion may be fixed to the wing body using a detachable fixture, or may be directly attached to the wing body by joining (welding, adhesive, etc.). Note that for a test specimen with a hat-shaped cross section, the flange portion (the collar portion extending from the end of the open groove) usually serves as the gripping portion. [Example]

[0030] The present invention will be specifically described with reference to examples of a bending test device and test results using the same.

[0031] [Bending test equipment] "composition" FIG. 1 shows an exploded perspective view of a bending test apparatus S (simply referred to as "apparatus S") according to one embodiment of the present invention. FIG. 2 shows a bending test performed on a test piece T, which is a thin plate formed into a hat-shaped cross section, attached to apparatus S. For ease of explanation, in this embodiment, the orthogonal directions indicated by arrows in the figure are referred to as the front-to-back direction (X direction / axial direction), the left-to-right direction (Y direction / horizontal direction), and the up-to-down direction (Z direction / vertical direction).

[0032] The device S comprises a pivot 1, a pair of wing bodies 21 and 22 (together referred to as the "wing body 2"), a driver 3, support columns 41 and 42 (together referred to as the "support column 4"), and a base 5.

[0033] The wings 21 and 22 are generally flat plates extending in the left-right direction from the center where they are fitted onto the pivot 1 extending in the front-rear direction. The pivot 1 and the wing 2 fitted around it so as to be rotatable form a hinge mechanism.

[0034] The mounting surfaces 2163 and 2164 of the wing body 21 (together referred to as the "mounting surface 216") and the mounting surfaces 2263 and 2264 of the wing body 22 (together referred to as the "mounting surface 226") are on a plane passing through the center of the pivot 1.

[0035] The left end of the wing body 21 and the right end of the wing body 22 are provided with an engaging portion 231 and an engaging portion 232 that protrude perpendicularly from the mounting surface 216 and the mounting surface 226, respectively.

[0036] The driver 3 (jig) is gate-shaped and has a main body 30 extending in the front-rear direction, and rods 33, 34 extending downward from the underside of the front and rear ends of the main body 30. The lower surfaces of the rods 33, 34 are formed with semicircular arc-shaped recessed pressing portions 335, 345 that fit into the receiving portions 13, 14 of the pivot 1. The driver 3 and a press device (not shown) that presses the driver 3 downward with a predetermined load (F) correspond to the driving means of the present invention.

[0037] The pillars 41 and 42 are made of round bars extending parallel to each other in the front-to-rear direction and are arranged at the same height (same position in the up-down direction) on the base 5. The pivot 1 is arranged at a position equidistant from the pillars 41 and 42, and the wing bodies 21 and 22 are simply supported on their undersides by the pillars 41 and 42, respectively.

[0038] "test" The test piece T, which has a hat-shaped cross section, is fixed on the wing body 2 with the front-to-rear direction as the width direction, the left-to-right direction as the length direction, and the up-to-down direction as the height direction. The test piece T is bent along its length direction.

[0039] (1) Installation The test piece T is mounted on the apparatus S as follows: First, the underside of the flange portion on the front side of the test piece T is fixed onto the mounting surface 2163 of the wing body 21 and the mounting surface 2263 of the wing body 22. Specifically, the spacers 613, 623 arranged above the flange portion are pressed down by the levers 713, 723 extending from the wing body 21 and the wing body 22, and the levers 713, 723 are fixed with bolts.

[0040] Similarly, the underside of the flange portion on the rear side of the test piece T is fixed onto the mounting surface 2164 of the wing body 21 and the mounting surface 2264 of the wing body 22. Specifically, the spacers 614, 624 arranged above the flange portions are pressed down by levers 714, 724 extending from the wing body 21 and the wing body 22, and the levers 714, 724 are fixed with bolts.

[0041] Next, the inner wall surface (right end surface) of the engaging portion 231 and the inner wall surface (left end surface) of the engaging portion 232 are brought into contact with the left end surface and the right end surface of the test piece T, respectively. As a result, the test piece T is subjected to a bending load corresponding to the rotation of the wing body 2 while its longitudinal movement is restricted (restrained).

[0042] (2) Operation The device S operates as follows to bend the test piece T (see Figure 2). When the test piece T is attached (fixed) to the upper surface of the wing body 2 fitted to the pivot 1, its underside is simply supported by the support 4. From this state, when a downward load is applied to the driver 3 by operating a press or compression testing machine, which serves as the driving source, the pushing parts 331 and 341 of the driver 3 press downward against the receiving parts 13 and 14 of the pivot 1. The wing body 2, which was simply supported by the support 4, closes due to the hinge mechanism, and a bending moment (M) is applied to the test piece T.

[0043] The load applied to the driver 3 is determined from a load cell or the like installed on the driver side, and the bending moment acting from the wing body 2 to the test piece T is also determined analytically. The deformation (strain) of the test piece T is determined by analyzing images taken of the test situation.

[0044] In this way, the apparatus S can perform a bending test on a test piece T having a hat-shaped cross section while avoiding local deformation.

[0045] <Experimental Example> As shown in Figure 3, when an actual bending test was conducted using device S and test piece T, test piece T deformed (buckled) approximately symmetrically around pivot axis 1 as a whole near the center in the longitudinal direction.

[0046] As shown in Figure 4, even when the test was repeated (N=3), there was a stable correlation between the downward movement (stroke) of pivot 1 and the load applied to test piece T. This also showed that the load or bending moment acting on test piece T can be evaluated based on the stroke (movement of pivot 1).

[0047] Incidentally, prior to the experiment, the bending test was analyzed in advance using CAE (Computer Aided Engineering). The model shape of test piece T was a forming depth of 30 mm, length (L): 75 to 150 mm (total length: 150 to 300 mm), and stroke: 0 to 10 mm. An example of the analysis (L: 75 mm, D: 10 mm) is shown in Figure 5. The analysis results showed that large localized deformation occurred at the ridge on the top plate side near the center of the longitudinal direction of test piece T (part A in Figure 5). This result was consistent with the deformation of the actual object shown in Figure 3.

[0048] In this way, it was confirmed that the use of the testing device of the present invention makes it possible to appropriately perform bending tests on test pieces with hat-shaped cross sections, etc. [Explanation of symbols]

[0049] S Test Equipment T test piece 1. Axis 2 wing body 3. Driver (driving means) 4 Pillar (Support)

Claims

1. Axis and a pair of wing bodies that rotate around the pivot axis; and a drive means for actuating the wing body; A test device in which a test piece attached to the wing body can be bent by closing or opening the wing body.

2. The bending test device according to claim 1 , further comprising a pair of supports that simply support the pair of wing bodies, respectively.

3. 3. The bending test device of claim 2, wherein the supports are disposed substantially symmetrically about the pivot axis.

4. 4. A bending test device according to claim 2, wherein said driving means pushes or pulls said pivot shaft in substantially perpendicular vertical directions.

5. 2. The bending test device according to claim 1, wherein the neutral plane of bending can be set or adjusted.

6. 2. The bending test device according to claim 1, wherein the wing body has a mounting surface for mounting the test piece on a plane passing through the approximate center of the pivot shaft.

7. 7. The bending test apparatus according to claim 6, wherein the test piece has a gripping portion that protrudes toward the extension side of the pivot, and the lower surface of the gripping portion is fixed in contact with the mounting surface.

8. The test piece has a hat-shaped cross section, 8. The bending test device according to claim 7, wherein the gripping portion is a flange portion of the test piece.

9. 2. A bending test device according to claim 1, wherein the wing body has engagement portions for restricting the end of the test piece on the left and right sides of the pivot shaft, which are approximately perpendicular to each other.

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