Test fixture

Abstract

To provide a test jig that is attached to a tensile tester adding one directional load, and overlappingly acts at least two directional loads to a test piece.SOLUTION: A test jig (S) comprises: an upper base (11) that can be mounted to a tester including an upper fitting body and a lower fitting body relatively moving in a vertical direction, and is mounted to the upper fitting body; a lower base (12) that is mounted to the lower fitting body; and a link mechanism (L2) that causes a pressure body (72) pressing a test piece (T) in conjunction with the upper base and lower base to move in a back and forth direction. A use of the test jig can overlappingly act a tensile stress and flexural stress on, for example, a simple-shape test piece. Thus, even a material strength test reproducing a state of a complex stress acting on a shell of a high-pressure container and the like can be easily conducted using a general-purpose tensile tester.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a test jig capable of converting a unidirectional tensile load into a compressive load in the other direction.

Background Art

[0002] A test for applying a load to a test piece and measuring its physical properties (mechanical properties) is essential in product development (especially material development), quality control, etc. Such a test is usually performed using a dedicated testing machine or test jig suitable for the physical property value to be measured. A typical example is a uniaxial tensile test (a test for applying a unidirectional tensile load to a test piece) using a universal testing machine (tensile testing machine).

[0003] However, in actual members, multi-directional stresses often act in a complex manner. Therefore, the material strength, etc. may not be accurately evaluated by only the uniaxial tensile test. For example, in the case of a shell wall (circumferential side wall) constituting a cylindrical pressure vessel, stresses in the longitudinal direction, circumferential direction, and thickness direction act in a complex manner. Also, due to the optimal design of members, anisotropic materials are increasingly used instead of isotropic materials, and it is more preferable that the degree of freedom in adjusting the directionality and magnitude, etc. of the load applied to the test piece is greater.

[0004] Therefore, a test jig (method) that can reproduce a stress state close to that of an actual member while using a universal testing machine has been proposed. Descriptions related to this are, for example, in the following documents.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] Patent Document 1 proposes a test fixture (method) in which a uniaxial tensile force is applied to a test specimen, which is cut from a steel pipe constituting a cylindrical pressure vessel and has pre-indented dents and scratches, at a position eccentric from the central axis of a tensile testing machine. With this test fixture, bending stress can be applied to the test specimen in addition to tensile stress.

[0008] Non-patent document 1 describes a test fixture in which one drive link and four driven links are rotatably mounted on a rotating disc. According to this test fixture, when a uniaxial load is applied to the drive link, a biaxial load is applied to a cross-shaped test piece attached to the other end of the driven links that are linked to it.

[0009] In any of the test fixtures, it is not possible to apply a compressive load in a direction different from the tensile direction of the tensile testing machine.

[0010] This invention was made in view of these circumstances, and aims to provide a test fixture or the like with a new structure different from conventional ones. [Means for solving the problem]

[0011] As a result of diligent research, the inventor conceived and successfully realized a test fixture with a novel link mechanism that can apply a pressing load in a direction different from the tensile direction of a tensile testing machine. By further developing this result, the present invention described below was completed.

[0012] Test fixtures (1) The present invention is a test fixture to be mounted on a testing machine having an upper mounting body and a lower mounting body that move relative to each other in the vertical direction, the test fixture comprising an upper base mounted on the upper mounting body, a lower base mounted on the lower mounting body, and a link mechanism that presses a test piece in the front-rear direction in conjunction with the upper base and the lower base.

[0013] (2) According to the test fixture of the present invention, a pressing load (e.g., vertical load, compressive load) can be applied to the test piece in a different direction (e.g., front-back direction) while using a testing machine that can apply a load in one direction (for convenience, referred to as the "up-down direction").

[0014] By superimposing a load in the front-to-back direction ("front-to-back load") with a load in the up-and-down direction ("up-and-down load") and / or a load in the left-to-right direction ("left-to-right load"), it becomes possible to apply a complex stress state to the test specimen even while using a general-purpose testing machine.

[0015] The link mechanism that applies a pressing load in the front-rear direction may be driven directly by the upper and lower mounting bodies (or upper and lower bases) of the testing machine, or it may be driven indirectly by a separate link (such as the left and right bases described later) that is linked to them.

[0016] 《Examination Method》 The present invention can also be understood as various testing methods using the test fixture described above. The test fixture may be used not only for tensile testing, but also for bending testing, compression testing, and the like.

[0017] "others" (1) The direction of each load applied by the testing machine and test fixture is easier to handle if it is in an orthogonal system (x-axis, y-axis, z-axis). Furthermore, the design and manufacture of the test fixture are easier if it has a substantially symmetrical structure with respect to at least one direction (or even all directions) of the vertical, horizontal, or front-to-back directions.

[0018] Unless otherwise specified, the term "base" as used herein also refers to a component of the link mechanism. Links, bases, chucks, etc., are not limited in shape (plate-shaped, rod-shaped, tubular, straight, curved, etc.), size, material, etc., as long as they have sufficient rigidity, strength, etc., to ensure the desired measurement accuracy. The type and model of the testing machine on which the test fixture is mounted are also not limited, as long as it can apply a load in one direction.

[0019] The test piece only needs to be in a form that allows at least the application of front and rear loads, and it can be planar (such as plate-shaped) or three-dimensional (such as rod-shaped). Its cross-section can also be square, circular, irregular, etc. The test piece can be, for example, straight-shaped extending in one direction or cross-shaped (cross-shaped) extending in multiple directions.

[0020] The measurement object is not limited to the stress acting on the test piece, and it can also be its displacement (strain), etc. The stress acting on the test piece can be tensile stress or compressive stress depending on the observation position (plane).

[0021] (2) The "up / down", "left / right", and "front / rear" mentioned in this specification are for the convenience of explanation, and the up / down direction does not necessarily have to be the vertical direction. Also, each direction does not necessarily have to be an orthogonal system. In this specification, unless otherwise specified, the up / down direction is described as the Y (axis) direction (axis), the left / right direction as the X (axis) direction (axis), and the front / rear direction as the Z (axis) direction (axis).

[0022] The "end side" (one end side, the other end side) mentioned in this specification is also for the convenience of explanation, and it does not necessarily have to be a strict end as long as it is an area (part) where it is possible to connect, join, or interlock with other elements. The same applies to "left side", "right side", "left part", "right part", "front side", "rear side", "front part", "rear part", etc.

[0023] (3) Unless otherwise specified, "x~y" mentioned in this specification includes the lower limit value x and the upper limit value y. Any numerical value included in the various numerical values or numerical ranges described in this specification can be used as a new lower limit value or upper limit value to newly set a range such as "a~b".

Brief Description of the Drawings

[0024] [Figure 1] It is a perspective view showing the whole of a test jig (an example). [Figure 2] It is a cross-sectional view (YZ cross-sectional view) of its central part. [Figure 3A] It is a schematic diagram showing the first link mechanism of the test jig. [Figure 3B]This is a set of mathematical formulas for calculating the forces acting on the test specimen by the first linkage mechanism. [Figure 4A] This is a skeletal diagram illustrating the second linkage mechanism of the test fixture. [Figure 4B] This is a set of mathematical formulas for calculating the stresses and other effects acting on the test specimen by the second linkage mechanism. [Figure 5] This graph shows the relationship between the bending stress acting on the test specimen by the second link mechanism and the spring constant of the elastic body biasing the pressurizing body. [Figure 6A] This image shows a photograph illustrating the maximum principal strain generated when a tensile load is repeatedly applied to a test specimen, and a graph showing its change over time. [Figure 6B] This image shows a photograph of the maximum principal strain generated when compressive and tensile loads are repeatedly applied to a test specimen, and a graph showing its change over time. [Modes for carrying out the invention]

[0025] The contents described herein may apply not only to test fixtures but also to test methods using them. One or more components arbitrarily selected from this specification may be added to the components of the present invention described above. Which embodiment is best will depend on the subject, required performance, etc.

[0026] Test fixtures By adjusting the length of each link (including the base) (pivot length) and the angle between links, it is possible to adjust the direction of the load applied to the test specimen and the ratio of that load (load ratio). The load and direction acting on the test specimen can be determined kinematically.

[0027] (1) The link mechanism (second link mechanism) that presses the test specimen in the front-rear direction is realized by, for example, a front base that is linked to the upper base and the lower base, and a pressurizing body that presses the test specimen in conjunction with the front base. In this case, a direct link mechanism may be configured between the upper base and the lower base, or an indirect link mechanism may be configured via a separate member (for example, the left base and the right base described later) that is linked to the upper base and the lower base. The former direct link mechanism comprises, for example, an upper link pivotally supported at one end on the upper base, a lower link pivotally supported at one end on the lower base, a front base pivotally supported at the other end of the upper link and the other end of the lower link, and a pressurizing body that presses the test specimen in conjunction with the front base.

[0028] If the linkage mechanism connected to the front base is a parallel crank mechanism, the mechanism can be simplified while allowing the pressurized body to move stably in the forward and backward directions.

[0029] (2) The test fixture may further include a link mechanism (first link mechanism) comprising an upper left link pivotally supported at one end on the left side of the upper base, an upper right link pivotally supported at one end on the right side of the upper base, a lower left link pivotally supported at one end on the left side of the lower base, a lower right link pivotally supported at one end on the right side of the lower base, a left base pivotally supported at the other end of the upper left link and the other end of the lower left link, and a right base pivotally supported at the other end of the upper right link and the other end of the lower right link.

[0030] In this case, a second link mechanism may be connected to the first link mechanism. For example, the second link mechanism may further comprise a left link with one end pivotally supported on a left base and a right link with one end pivotally supported on a right base, with the front base pivotally supported on the other end of the left link and the other end of the right link.

[0031] (3) The front base may directly press the test specimen, or it may indirectly press it via a pressurizing body (push rod, rod, etc.). If the front base and the pressurizing body are connected via an elastic body, the load applied to the test specimen can be easily adjusted by adjusting the spring constant (modulus of elasticity), natural length, set length, etc. of the elastic body (spring, etc.). In this case, the number and arrangement of the elastic bodies are not specified. If multiple elastic bodies are evenly arranged around the pressurizing body, the test specimen will be stably pressed by the biased pressurizing body.

[0032] (4) When a left base and a right base are provided, for example, the left outer angle (α) is the angle between the links that the upper left link and the lower left link make outward, and the upper right link and under If the right external angle (β), which is the angle between the links formed by the right link pointing outward, is kept within 180°, tensile loads can be applied to the test specimen in two directions. Specifically, the left external angle (α) and / or the right external angle (β) should be, for example, between 70° and 160°, 80° and 150°, or even 90° and 140°. Furthermore, if both the left and right external angles are greater than 180°, it becomes possible to apply a tensile load in one direction to the test specimen while applying a compressive load in the other direction.

[0033] (5) The test specimen is held by chucks. Chucks are usually provided in pairs in the vertical direction and / or in the left-right direction. Specifically, the test fixture includes, for example, an upper chuck that holds the upper part of the test specimen and is connected to an upper base, and a lower chuck that holds the lower part of the test specimen and is connected to a lower base. The test fixture also includes, for example, a left chuck that holds the left part of the test specimen and is connected to a left base, and a right chuck that holds the right part of the test specimen and is connected to a right base.

[0034] Test specimen The morphology (shape, size) and material of the test specimen may be adjusted as appropriate according to the purpose of the test, and may be isotropic or anisotropic.

[0035] For strength tests simulating the shell wall (circumferential side wall) of a pressure vessel, a flat (strip-shaped, cross-shaped, etc.) test specimen can be held at its end with a chuck, and a pressing load can be applied from the direction normal to its plane (out-of-plane direction). This allows tensile and bending stresses to act superimposed on the test specimen. Incidentally, in addition to biaxial tensile stress (circumferential stress and tangential stress perpendicular to it in the longitudinal direction), bending stress (distributed stress along the wall thickness) can also act on the shell wall of a pressure vessel (for example, a cylindrical hydrogen tank subjected to high internal pressure). Bending stress increases with wall thickness and is usually maximum on the inner wall surface. The superimposed effect of tensile and bending stresses can also occur near the joint between the body and dome sections of the pressure vessel. [Examples]

[0036] The present invention will be specifically explained with reference to an example of a test fixture and an example of measurement using it.

[0037] [Test fixtures] "composition" Figure 1 shows a perspective view of a test jig S (simply referred to as "jig S"), which is one embodiment of the present invention. Figure 2 shows a longitudinal section (YZ section) of jig S cut in the front-to-back direction at its center. In this embodiment, for the sake of explanation, the directions indicated by arrows in the figures are defined as the up-and-down direction (Y-axis direction), the left-to-right direction (X-axis direction), and the front-to-back direction (Z-axis direction).

[0038] (1) The fixture S is mounted between the crosshead (fixed side) and the piston (movable side) of a material testing machine capable of applying a uniaxial load. The fixture S comprises a first link mechanism L1 that applies loads to the test piece in the vertical and horizontal directions, and a second link mechanism L2 that operates in the longitudinal direction and applies a load to the test piece in the longitudinal direction. The details of the first link mechanism L1 are schematically shown in Figure 3A.

[0039] The first link mechanism L1 follows the relative movement of the crosshead and the piston, and the second link mechanism L2 follows the first link mechanism L1. The jig S (first link mechanism L1 and second link mechanism L2) has a symmetrical structure in the vertical and horizontal directions. The specific structure is as follows:

[0040] (2) The first link mechanism L1 comprises an upper base 11 that is detachable from the crosshead (upper mounting body), a lower base 12 that is detachable from the piston (lower mounting body), four upper left links 211, lower left links 221, upper right links 212 and lower right links 222 disposed between the upper base 11 and the lower base 12, four upper chucks 31, lower chucks 32, left chucks 41 and right chucks 42 that grip the upper, lower, left and right parts of the test piece T respectively, a left base 43 that follows the upper left links 211 and lower left links 221 and holds the left chuck 41, and a right base 44 that follows the upper right links 212 and lower right links 222 and holds the right chuck 42. The attachment and detachment (fixing) of each component, gripping (fixing) of the test piece, etc. are done by fastening a plurality of bolts b.

[0041] One end of the upper left link 211 is pivotally connected (supported) to the left end of the upper base 11 by pivot 511, and the other end is pivotally supported to the upper part of the left base 43 by pivot 611. One end of the lower left link 221 is pivotally supported to the left end of the lower base 12 by pivot 521, and the other end is pivotally supported to the lower part of the left base 43 by pivot 621.

[0042] One end of the upper right link 212 is pivotally supported by the right end of the upper base 11 and pivot 512, and the other end is pivotally supported by the upper part of the right base 44 and pivot 612. right One end of link 222 is pivotally supported by pivot 522 to the right end of lower base 12, and the other end is pivotally supported by pivot 622 to the lower part of right base 44.

[0043] When the testing machine is activated and the lower base 12 is moved relative to the upper base 11 (relative movement in the vertical direction away from each other), a tensile load in the vertical direction (Y-axis direction) acts on the test specimen T held by the upper chuck 31 fixed to the upper base 11 and the lower chuck 32 fixed to the lower base 12. In conjunction with this, the left base 43, pivotally supported by the upper left link 211 and the lower left link 221, and the right base 44, pivotally supported by the upper right link 212 and the lower right link 222, move in the horizontal direction away from each other. As a result, a tensile load in the horizontal direction (X-axis direction) also acts on the test specimen T held by the left chuck 41 fixed to the left base 43 and the right chuck 42 fixed to the right base 44.

[0044] (3) The second link mechanism L2 comprises a front base 71, a push rod 72 (pressure body), a left link 81, a right link 82, and a biasing mechanism 9. One end of the left link 81 is rotatably connected (pivoted) to a pivot 451 provided on the right end side of the left base 43, and the other end is pivotally supported to a pivot 452 provided on the left front side of the front base 71. Similarly, one end of the right link 82 is rotatably connected (pivoted) to a pivot 461 (details omitted) provided on the left end side of the right base 44, and the other end is pivotally supported to a pivot 462 (details omitted) provided on the right front side of the front base 71.

[0045] The left link 81 and the right link 82 each consist of two horizontally positioned links. The left link 81, the left base 43, and the front base 71 constitute a parallel crank mechanism. Similarly, the right link 82, the right base 44, and the front base 71 also constitute a parallel crank mechanism.

[0046] The biasing mechanism 9 comprises a base 91, an upper guide 921 and a lower guide 922 made of hexagonal bolts, and an upper spring 941 and a lower spring 942 made of coil springs. The upper guide 921 and the lower guide 922 are inserted from the upper and lower rear ends of the base 91, respectively, and the upper front and lower front ends of the base 91 serve as the rear seating surfaces for the upper spring 941 and the lower spring 942, respectively.

[0047] Furthermore, the upper guide 921 and the lower guide 922 are loosely fitted from the upper and lower rear ends of the front base 71, respectively, and the upper rear surface and the lower rear surface of the front base 71 become the front seating surfaces for the upper spring 941 and the lower spring 942, respectively. The tips of the upper guide 921 and the lower guide 922 are screwed into and held by the upper nut 931 and the lower nut 932 on the upper and lower front ends of the front base 71, respectively.

[0048] The front base 71, which follows the left link 81 and the right link 82, moves back and forth along the upper guide 921 and the lower guide 922. For example, when the front base 71 moves backward, the upper spring 941 and the lower spring 942 contract, biasing the base 91 backward. The pushing force exerted on the base 91 by the upper spring 941 and the lower spring 942 is transmitted to the push rod 72. As a result, the push rod 72, with a pad 722 at its rear end, contacts the central front surface of the test piece, applying a load in the front-rear direction to the test piece.

[0049] The relationship between the amount of movement of the front base 71 and the load applied to the test piece by the push rod 72 is adjusted by the spring constants of the upper spring 941 and the lower spring 942 and their preset loads. The spring constants are adjusted, for example, by changing the coil springs. The preset loads are adjusted, for example, by the tightening amount of the upper nut 931 and the lower nut 932.

[0050] "analysis" (1) Figure 3B shows an example of the analysis of the load applied to the test specimen by the first link mechanism L1 (see Figure 3A). Specifically, it is as follows:

[0051] Links 211, 221, 212, and 222 (collectively referred to as "Link 2") are all pivotally supported by bases 11 and 12 (collectively referred to as "Base 1") and chucks 31 and 32 (collectively referred to as "Chuck 3") or bases 43 and 44 (collectively referred to as "Base 4") in symmetrical positions with respect to the vertical and horizontal directions, with equal distance (L) between pivot points.

[0052] Furthermore, the testing machine applies a tensile load (P0) in the vertical direction (uniaxial direction) above the center between the left and right pivot points of base 1. Let θ (half-external angle) be the angle between link 2 and the left-right direction (horizontal direction), and let Pθ be the tension acting along link 2. The angle between the upper left link 211 and the lower left link 221 (left external angle: α) and the angle between the upper right link 212 and the lower right link 222 (left external angle: β) are expressed as 2θ.

[0053] In the case of a symmetrical jig S, the tensile load (Py) acting between the chucks 3 and the tensile load (Px) acting between the chucks 4 are given by equations (11) and (12) in Figure 3B, based on the balance of forces. From both equations, the relationship between the tensile loads P0, Px, and Py is given by equation (13).

[0054] Let Gx and Gy be the stiffnesses of the specimen T in the left-right direction (x direction) and the up-down direction (y direction), respectively, and let Δθ be the change in the half-external angle (θ) of each link from the initial position when a tensile load P0 is applied. In this case, the elongations δx and δy in each direction are expressed by equations (21) and (22) shown in Figure 3B.

[0055] Here, assuming that the stiffness of the specimen T is isotropic in the left-right and up-down directions (Gx=Gy), the load ratio (Px / Py) is given by equation (31) shown in Figure 3B. From equations (31) and (13), for example, the relationship between tensile loads P0 and Py can be found as shown in equation (32).

[0056] Depending on the material of the test specimen T and the measurement range, if Δθ is sufficiently small (θ≈0), the tensile loads Px and Py can be expressed using equations (31) and (32), respectively, with respect to the tensile load P0 and the half-external angle θ, as shown in equations (41) and (42) in Figure 3B.

[0057] From equations (41) and (42), the relationship between Px / P0, Py / P0, and Px / Py and the half-exterior angle θ (α / 2 = β / 2) is such that, for example, when θ = 45° to 80° and even 45° to 75° (exterior angle 2θ = 90° to 160° and even 90° to 150°), the load acting on the test specimen T from two directions falls within a reasonable range.

[0058] (2) The load applied to the test specimen by the second link mechanism L2 was analyzed. For the sake of convenience in the analysis, as shown in Figure 4A, we will consider the case in which a compressive load is applied from the normal direction (front-back direction / Z direction) to the side surface (plane along the tensile direction) of a strip-shaped test specimen subjected to a uniaxial tensile load, thereby simultaneously applying tensile stress and bending stress to the test specimen. Specifically, it is as follows:

[0059] The initial evaluation section length of the test specimen is L0 (length in the X (left-right) direction), b (width in the Y (up-down) direction), h (thickness in the Z (front-back) direction), E (elastic modulus of Young's modulus), φ (angle between the left and right links 81 and 82 and the left and right bases 43 and 44), k (spring constant between the upper spring 941 and lower spring 942), δx (displacement in the X direction of the left and right bases 43 and 44), and δz (displacement in the Z direction of the front base 71). These values ​​are assumed to be known.

[0060] Load applied to the specimen in the Z direction: Pz, amount of spring contraction: δs, amount of deflection of the specimen (center) (displacement in the Z direction): δt, bending stiffness of the specimen: k TP These values ​​are considered unknown. The test specimen was designed to allow movement in the X direction, while both ends in the X direction were fixedly supported.

[0061] From the link mechanism shown in Figure 4A, the relationship between displacements δx and δz is given by equation (51) shown in Figure 4B. Equations (52) and (53) are derived from Hooke's Law. From equations (51), (52), and (53), Pz is expressed as in equation (54).

[0062] From the analytical solution based on material mechanics, the deflection δt of the test specimen is expressed as shown in equation (55). From equations (52) and (55), the bending stiffness (k) of the test specimen can be expressed. TP ) can be found as shown in equation (56).

[0063] Furthermore, the tensile elongation (2δx) of the specimen can be determined from the initial length (L0) and strain (ε=σx / E) as shown in equation (57). σx is the average tensile stress acting on the cross-section (YZ section) of the specimen when a load (Px) is applied in the X direction. E is the modulus of elasticity (Young's modulus) of the specimen with respect to that cross-section (YZ section).

[0064] The load (Pz) in the Z direction applied to the specimen can be determined from equations (54), (56), and (57). The (maximum) bending stress (σbmax) due to this load (Pz) can be determined from an analytical solution based on material mechanics as shown in equation (58). Figure 5 shows an example of a specific plot of the relationship between the spring constant (k) and the bending stress (σbmax) from equations (54), (56), (57), and (58).

[0065] Thus, it can be seen that the load in the Z direction (Pz) can be adjusted by the spring constant (k). Furthermore, from equation (58), it can be seen that an arbitrary bending stress (σbmax) can be superimposed on the tensile stress (σx) and applied to the test specimen.

[0066] [Example Test] (1) As test specimen T, a sample was prepared in which a tape made of carbon fiber reinforced polymer (CFRP) (referred to as "UD tape") was laminated in a cross shape. The shape of this test specimen T was symmetrical with respect to both left-right and top-bottom.

[0067] (2) The upper and lower parts and left and right sides of the test specimen T were gripped by chucks 31, 32, 41, and 42 of a fixture S mounted on an electrohydraulic material testing machine. At this time, the outer angle (α, β = 2θ) was set to 90°. A marker was pre-applied to the rear side of the central part (cross intersection) of the test specimen T.

[0068] (3) First, with the push rod 72 removed (without pressure on the test specimen T by the pad 722), the material testing machine with the jig S attached was operated to apply tensile loads (Px, Py) in the left-right and up-down directions to the test specimen T (see Figure 3A). While repeatedly increasing and decreasing the load, the strain distribution was analyzed by digital image correlation based on images taken of the surface (marker) of the test specimen T. The change in the maximum principal strain appearing in the test specimen T obtained in this way is shown in Figure 6A. Figure 6A shows both the maximum principal strain in the central part (within the circle) and the average value of the maximum principal strain over the entire field of view of the test specimen T. As is clear from Figure 6A, there was no significant difference between the two.

[0069] (4) Next, with the push rod 72 attached (pad 722 pressing against the test specimen T), the material testing machine with the jig S attached was operated to apply a pressing load (Pz) in the front-rear direction in addition to the two tensile loads (Px, Py) described above to the test specimen T. The change in the maximum principal strain obtained by the method described above while repeatedly increasing and decreasing the load is shown in Figure 6B. As is clear from Figure 6B, the maximum principal strain in the central part (within the circle) of the test specimen T pressed by pad 722 was found to be approximately 25% greater than the average value of the entire field of view, while being synchronized with the average value of the entire field of view. In other words, it was confirmed that bending stress can be superimposed on tensile stress in the desired region of the test specimen T.

[0070] Thus, the test fixture of the present invention allows for the application of loads in at least two directions to a test specimen while using a testing machine that applies a load in one direction. This makes it possible, for example, to perform strength tests on materials subjected to superimposed tensile and bending stresses using a general-purpose tensile testing machine. [Explanation of Symbols]

[0071] S Test fixture T Test specimen 11, 12 Bass Links 211-222 31, 32, 41, 42 Chuck 43, 44, 71 Bass 72 Push bar (pressure body) L1, L2 linkage mechanism

Claims

1. A test fixture to be mounted on a testing machine having an upper mounting body and a lower mounting body that move relative to each other in the vertical direction, An upper base that is attached to the upper mounting body, A lower base attached to the lower mounting body, A link mechanism that works in conjunction with the upper and lower bases to press the test piece in the front-rear direction, An upper left link, with one end pivotally supported on the left side of the upper base, An upper right link, with one end pivotally supported on the right side of the upper base, A lower left link, with one end pivotally supported on the left side of the lower base, A lower right link, with one end pivotally supported on the right side of the lower base, The left base is pivotally supported on the other end of the upper left link and the other end of the lower left link, The upper right link comprises a right base pivotally supported on the other end and the lower right link, The link mechanism is, The left link, with one end pivotally supported on the left base, A right link, with one end pivotally supported on the right base, A front base pivotally supported on the other end of the left link and the other end of the right link, A test fixture comprising a pressurizing body that moves the test piece in conjunction with the front base.

2. The test fixture according to claim 1, wherein the left link and the right link constitute a parallel crank mechanism.

3. A test fixture to be mounted on a testing machine having an upper mounting body and a lower mounting body that move relative to each other in the vertical direction, An upper base that is attached to the upper mounting body, A lower base attached to the lower mounting body, A link mechanism that works in conjunction with the upper and lower bases to press the test piece in the front-rear direction, An upper left link, with one end pivotally supported on the left side of the upper base, An upper right link, with one end pivotally supported on the right side of the upper base, A lower left link, with one end pivotally supported on the left side of the lower base, A lower right link, with one end pivotally supported on the right side of the lower base, The left base is pivotally supported on the other end of the upper left link and the other end of the lower left link, The upper right link comprises a right base pivotally supported on the other end and the lower right link, The link mechanism is, An upper link, with one end pivotally supported on the upper base, A lower link, with one end pivotally supported on the lower base, A front base pivotally supported on the other end of the upper link and the other end of the lower link, A test fixture comprising a pressurizing body that moves the test piece in conjunction with the front base.

4. The test fixture according to claim 3, wherein the upper link and the lower link constitute a parallel crank mechanism.

5. A left chuck that holds the left portion of the test piece and is linked to the left base, A right chuck that holds the right portion of the test piece and is linked to the right base, A test fixture according to claim 1 or 3, comprising:

6. An upper chuck that holds the upper part of the test piece and is linked to the upper base, A lower chuck that holds the lower part of the test piece and is linked to the lower base, A test fixture according to claim 1 or 3, comprising:

7. The test fixture according to claim 1 or 3, wherein the front base and the pressurizing body are connected via an elastic body.

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