Tensile tester and benchmark fixture

Abstract

To provide a tensile tester and benchmark fixtures that can easily and appropriately fix benchmark lines to a test piece.SOLUTION: A tensile tester includes a test machine body that applies a test force to a test piece to perform a tensile test, and an extensometer that measures the elongation of the test piece, the extensometer having a pair of benchmark fixtures that fix benchmark lines to the test piece, and a camera that photographs the benchmark lines, the benchmark line fixture includes a first member and a second member that sandwich the test piece and are arranged apart from each other, a support member that is fixed to the second member and supports the first member so as to be movable in a direction approaching and moving away from the second member, and a biasing member that biases the first member toward the second member, and the benchmark line is provided along at least a portion of the outer periphery of the first member and the second member.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a tensile tester and a gauge fixture. [Background technology]

[0002] There is known a material testing machine equipped with a video extensometer that measures the elongation of a test specimen by marking the specimen with a benchmark mark and identifying the displacement of the benchmark mark using a video camera during a tensile test. For example, Patent Document 1 describes that a benchmark member with a benchmark mark drawn on it is attached to a linear test specimen such as a wire by a clip member or a set screw. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Registered Utility Model No. 3125889 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned tensile testing machine, when the cross-sectional area of ​​the test specimen is reduced by the application of a test force, the benchmark fixing device may come off the test specimen, and the benchmark may not be properly fixed to the test specimen.

[0005] The present invention has been made in consideration of the above circumstances, and has an object to provide a tensile tester and a benchmark fixing device that can easily and appropriately fix a benchmark to a test specimen whose cross-sectional area decreases during testing. [Means for solving the problem]

[0006] A first aspect of the present invention relates to a tensile testing machine comprising: a testing machine body that applies a test force to a test specimen to perform a tensile test; and an extensometer that measures the elongation of the test specimen, the extensometer having a pair of benchmark line fixtures that fix a benchmark line to the test specimen, and a camera that photographs the benchmark line, the benchmark line fixture comprising a first member and a second member that sandwich the test specimen and are arranged apart from each other, a support member that is fixed to the second member and supports the first member so as to be movable in a direction toward and away from the second member, and a biasing member that biases the first member toward the second member, and the benchmark line is provided along the outer periphery of at least a portion of the first member and the second member.

[0007] A second aspect of the present invention relates to a benchmark fixture that fixes a benchmark for measuring the elongation of a test specimen for a tensile test, the benchmark fixture comprising: a first member and a second member that sandwich the test specimen and are arranged spaced apart from each other; a support member that is fixed to the second member and supports the first member so as to be movable in directions toward and away from the second member; and a biasing member that biases the first member toward the second member, the benchmark fixture being provided along the outer periphery of the first member and the second member.

[0008] A third aspect of the present invention relates to a benchmark line fixture that fixes a benchmark line for measuring the elongation of a test specimen for a tensile test to the test specimen, the benchmark line fixture comprising: a support member that clamps the test specimen and has a separation portion, a part of which is spaced apart in a direction perpendicular to the elongation direction of the test specimen, and that supports the separation portion movably in directions narrowing and widening the separation portion; and a biasing member that biases the separation portion in the direction narrowing the separation portion, the benchmark line being provided along the outer periphery of the benchmark line fixture. Effect of the Invention

[0009] According to the first and second aspects of the present invention, as the cross-sectional area of ​​the test specimen decreases due to the application of a test force, the biasing member narrows the gap between the first and second members, making it easier to maintain the benchmark fixture fixed to the test specimen. This makes it possible to provide a tensile tester and benchmark fixture that can easily and appropriately fix the benchmark to a test specimen whose cross-sectional area decreases during testing.

[0010] According to the third aspect of the present invention, the separating portion can easily continue to clamp the test object by utilizing the biasing force of the biasing member. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram showing the configuration of a tensile tester. [Diagram 2] FIG. 2 is a front view of the benchmark fixture fixed to the test specimen. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 4 is a view showing a cross section similar to that of FIG. 3 after a tensile test. [Diagram 5] FIG. [Figure 6] 5 is a cross-sectional view of a modified mark line fixture corresponding to FIG. 3. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] [1. Overall configuration of the tensile testing machine] FIG. 1 is a diagram showing the configuration of a tensile testing machine 1. The tensile testing machine 1 of this embodiment applies a test force to a test specimen T that is the subject of the tensile test, and performs a tensile test to measure mechanical properties such as the tensile strength, yield point, elongation, and reduction in area of ​​the test specimen T. In this embodiment, the test specimen T is a wire rope formed by twisting together multiple strands. Note that the strands may be made of a single wire, or may be made by twisting together multiple wires.

[0014] The tensile tester 1 includes a tester body 10 and an extensometer 30 . The testing machine body 10 has a base 11. A table 12 is provided on the top of the base 11. A pair of pillars 13 are erected on the table 12. A cross yoke 14 is suspended on the top of the pillars 13. A threaded rod (not shown) is provided inside the pillar 13. The threaded rod is composed of a ball screw, and both ends of a crosshead 15 are connected to the threaded rod. The crosshead 15 rises and falls relative to the table 12 by rotation of the threaded rod. The threaded rod is rotated by an electric motor (not shown). A load cell 16 is installed on the crosshead 15.

[0015] An upper chuck 18 is attached to the load cell 16 via a joint. A lower chuck 19 is disposed below the upper chuck 18. The lower chuck 19 is fixed to the upper surface of the table 12. Each chuck 18, 19 opens and closes by the operation of a cylinder device (not shown) to grip the test piece T. The upper chuck 18 grips the upper end of the test piece T. The lower chuck 19 grips the lower end of the test piece T.

[0016] The testing machine body 10 raises and lowers the crosshead 15 with the test specimen T gripped by the chucks 18, 19. As a result, the upper chuck 18 rises and lowers relative to the lower chuck 19 together with the crosshead 15, and a test force is applied to the test specimen T. At this time, the load cell 16 measures the test force applied by the upper chuck 18. That is, in this embodiment, the tensile direction, which is the direction of the test force, is the up-down direction.

[0017] The extensometer 30 has a camera 31 and a benchmark line fixture 50. A benchmark line M is provided to the benchmark line fixture 50. The benchmark line fixture 50 is fixed to the test piece T, thereby fixing the benchmark line M to the test piece T. The camera 31 photographs the test piece T and the benchmark line fixture 50 fixed to the test piece T. In this embodiment, one benchmark line fixture 50 is fixed to each of two locations, top and bottom, of the test piece T.

[0018] The tensile tester 1 is provided with a control device 100. The control device 100 is communicatively connected to the tester body 10 and the camera 31 via communication connection means such as a signal cable. The control device 100 includes a computer, which includes a processor such as a central processing unit (CPU) or a micro-processing unit (MPU), a memory device such as a read only memory (ROM) or a random access memory (RAM), a storage device such as a hard disk drive (HDD) or a solid state drive (SSD), and an interface circuit for connecting the control device 100 to various peripheral devices. The processor executes computer programs stored in the memory device or the storage device to realize various functions of the tensile tester 1.

[0019] In this embodiment, when the control device 100 receives an input operation to start a test, it controls the tensile tester 1. That is, the control device 100 controls the testing machine body 10 to apply a test load to the test piece T, and starts the tensile test. During the tensile test, the control device 100 receives a measurement value of the test force by the load cell 16.

[0020] The control device 100 also calculates the elongation of the test piece T. Specifically, the control device 100 acquires a video signal from the camera 31, i.e., the photographed data. The control device 100 detects the position of each marked line M based on the photographed data. The control device 100 calculates the displacement of each marked line M based on the position of each marked line M and the position of each marked line M at the start of the test. The control device 100 also calculates the displacement of the marked line distance, i.e., the elongation of the test piece T, based on the initial marked line distance, the displacement of the upper marked line M, and the displacement of the lower marked line M.

[0021] In addition, when using a test specimen T that is prone to slack, such as a wire rope formed by twisting strands together, as in this embodiment, the test specimen T is gripped by each chuck 18, 19, and then the crosshead 15 is moved until the slack in the test specimen T is eliminated, and then the test is started. For this reason, the position of the crosshead 15 at the start of the test and the length of the test specimen T stretched between each chuck 18, 19 tend to vary for each test. Therefore, when measuring the elongation of the test specimen T from the displacement of the crosshead 15, it is difficult to measure the elongation based on the test specimen T of the same length for each test. In contrast, in this embodiment, the elongation of the test specimen T is measured by the displacement of the benchmark M instead of the displacement of the crosshead 15. That is, for the test specimen T from which the slack has been eliminated, the benchmark fixture 50 is fixed to the test specimen T at the same distance interval for each test, making it easier to measure the elongation based on a uniform standard.

[0022] [2. Configuration of the marking fixture] Fig. 2 is a front view of the benchmark fixture 50 fixed to the test piece T. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. Fig. 3 shows the state before the start of the tensile test.

[0023] The marking line fixing tool 50 has a fixing tool body 51 and a marking line tape 53. The fixing tool body 51 is a substantially cylindrical tool attached to the test piece T. The marking line tape 53 is a tape wound around the outer periphery of the fixing tool body 51. A marking line M is provided on the outer periphery of the marking line tape 53. The fixing tool body 51 is attached to the test piece T in such a manner that the bottom surface of the cylindrical shape of the fixing tool body 51 is substantially perpendicular to the tensile direction. In the following, the direction around the test piece T stretched along the tensile direction is defined as the circumferential direction, and the direction perpendicular to the tensile direction and the circumferential direction, approaching or moving away from the test piece T, is defined as the radial direction. In the radial direction, the side closer to the test piece T is the inner side, and the side farther from the test piece T is the outer side.

[0024] 3, the fixing device main body 51 has a first member 60 and a second member 70 disposed opposite the first member 60. The first member 60 and the second member 70 each have a shape similar to a cylinder with a semicircular bottom. The bottom of the cylinder formed by the first member 60 and the second member 70 is approximately perpendicular to the tensile direction. In this embodiment, the first member 60 and the second member 70 are made of a metal such as aluminum or stainless steel.

[0025] The first member 60 has a first outer peripheral surface 61, which is a curved surface. The first outer peripheral surface 61 is curved in an arc shape in a cross section perpendicular to the tensile direction. Specifically, the first outer peripheral surface 61 in this embodiment has a semicircular arc shape in the cross section. The first member 60 has a first opposing surface 63, which is the surface opposite to the first outer peripheral surface 61. The first opposing surface 63 has a flat shape and is connected to both ends of the first outer peripheral surface 61 in the circumferential direction. The first outer peripheral surface 61 and the first opposing surface 63 correspond to the side surfaces of the column formed by the first member 60. The first outer peripheral surface 61 corresponds to an example of the "outer periphery of the first member" in this embodiment.

[0026] The first opposing surface 63 has a first groove 64 formed on the side of the first outer circumferential surface 61, i.e., recessed toward the outside in the radial direction. The first groove 64 is approximately parallel to the tensile direction and is formed over the entire first opposing surface 63 in the tensile direction. The first groove 64 is formed in the center of the first opposing surface 63. In this embodiment, the shape of the first groove 64 in a cross section perpendicular to the tensile direction is a right-angled isosceles triangle whose base is flush with the first opposing surface 63.

[0027] The second member 70 is formed with a second outer peripheral surface 71 having a shape similar to that of the first outer peripheral surface 61. The second member 70 is formed with a second opposing surface 73, which is the surface opposite to the second outer peripheral surface 71. The second opposing surface 73 has a shape similar to that of the first opposing surface 63. The second opposing surface 73 is formed with a second groove portion 74 that is recessed toward the second outer peripheral surface 71. The second groove portion 74 has a shape similar to that of the first groove portion 64. The first groove portion 64 and the second groove portion 74 correspond to an example of a "groove portion" in this embodiment. The second outer peripheral surface 71 corresponds to an example of the "outer periphery of the second member" in this embodiment.

[0028] The first member 60 and the second member 70 are disposed in a position in contact with the test specimen T, with the first opposing surface 63 and the second opposing surface 73 facing each other and sandwiching the test specimen T between them. In other words, the first member 60 and the second member 70 sandwich the test specimen T between the first opposing surface 63 and the second opposing surface 73. At this time, the first member 60 and the second member 70 are disposed apart from each other. More specifically, the first member 60 and the second member 70 are disposed in a position where the test specimen T passes through the inside of the first groove portion 64 and the second groove portion 74.

[0029] In this embodiment, the wire rope as the test specimen T can be regarded as having a generally circular cross section. For this reason, in this embodiment, in a cross section perpendicular to the tensile direction, the length L of the equilateral sides of the right-angled isosceles triangle formed by the grooves 64, 74 is set to be greater than the radius R of the circumscribing circle of the test specimen T. This makes it easier for the test specimen T to come into contact with the inner surface 64a of the first groove portion 64 and the inner surface 74a of the second groove portion 74. In addition, the length L is set to be less than twice the radius R. This causes the first opposing surface 63 and the second opposing surface 73 to be separated from each other when the test specimen T comes into contact with the inner surfaces 64a, 74a before the start of the test.

[0030] The first member 60 is supported by a support member 81 fixed to the second member 70. In this embodiment, the support member 81 is a bolt having a head portion 81a and a shaft portion 81b, and two support members 81 are provided on one benchmark line fixture 50. In this embodiment, the two support members 81 are provided at positions sandwiching the test specimen T between them.

[0031] The support member 81 is disposed so as to penetrate the first member 60 through the through hole 65. The through hole 65 is a hole penetrating the first member 60 from the first outer peripheral surface 61 to the first opposing surface 63. The through holes 65 are provided in the same number as the support members 81. The through holes 65 extend in a direction substantially perpendicular to the first opposing surface 63. The through hole 65 is composed of a large diameter portion 65a located on the first outer peripheral surface 61 side and a small diameter portion 65b located on the first opposing surface 63 side of the large diameter portion 65a. The large diameter portion 65a is a hole-shaped portion having a larger diameter than the head portion 81a of the support member 81 in a cross section parallel to the first opposing surface 63. The small diameter portion 65b is a hole-shaped portion having a smaller diameter than the head portion 81a and a larger diameter than the shaft portion 81b including the screw thread in a cross section parallel to the first opposing surface 63.

[0032] The second member 70 has the same number of fastening holes 75 as the support members 81. The fastening holes 75 are female threads, and the shaft portions 81b of the support members 81 are fastened to the fastening holes 75. The fastening holes 75 are recessed from the second opposing surface 73 toward the second outer peripheral surface 71, and extend in a direction approximately perpendicular to the second opposing surface 73. The fastening holes 75 are located at positions overlapping with the small diameter portions 65b of the through holes 65 when viewed from a direction perpendicular to the opposing surfaces 63, 73 when the opposing surfaces 63, 73 are overlapped.

[0033] The support member 81 is inserted into the through hole 65 from the side of the first outer circumferential surface 61 with the shaft portion 81b in a position substantially perpendicular to the first opposing surface 63 and the second opposing surface 73. The support member 81 penetrates the first member 60 with the head portion 81a located inside the large diameter portion 65a and the shaft portion 81b passing through the small diameter portion 65b. A part of the tip side of the shaft portion 81b that penetrates the small diameter portion 65b is fastened to the fastening hole 75. As a result, the support member 81 is fixed to the second member 70. In addition, since the head portion 81a cannot pass through the small diameter portion 65b, the movement range of the first member 60 is restricted by the head portion 81a. As a result, the first member 60 is supported by the support member 81 so as to be movable in a direction approaching and moving away from the second member 70.

[0034] Further, a biasing member 83 is provided between the first member 60 and each support member 81. The biasing member 83 biases (presses) the first member 60 toward the second member 70. In this embodiment, the biasing member 83 is a coil spring and is used as a compression spring. In detail, the biasing member 83 is sandwiched between the seat surface 81c of the support member 81 and the step surface 65c, which is a surface formed at the boundary between the large diameter portion 65a and the small diameter portion 65b, with the shaft portion 81b passing through the inside. When the mark line fixture 50 is attached to the test piece T, the support member 81 is tightened to the maximum, so that the biasing member 83 is in a compressed state at the start of the test.

[0035] Since the biasing member 83 biases the first member 60 toward the second member 70, the inner surfaces 64a, 74a of the first groove portion 64 and the second groove portion 74 are pressed against the test piece T arranged inside the first groove portion 64 and the second groove portion 74. Therefore, the first member 60 and the second member 70 are fixed to the test piece T by the frictional force between the test piece T and the inner surfaces 64a, 74a. This makes it possible to easily fix the benchmark line fixing device 50 to the test piece T, such as a wire rope, which has an uneven surface and therefore is difficult to attach a sticker or the like to.

[0036] FIG. 4 is a diagram showing a cross section similar to that shown in FIG. 3 after a tensile test. The test specimen T becomes thinner due to lateral strain, squeezing, etc., associated with the application of the test force. Therefore, compared to the state before the start of the test in FIG. 3, the cross-sectional area of ​​the test specimen T during the test and after the test shown in FIG. 4 is smaller. In contrast, in this embodiment, the biasing member 83 biases the first member 60 toward the second member 70. Therefore, even if the cross-sectional area of ​​the test specimen T decreases due to the application of the test force, the first member 60 and the second member 70 can continue to clamp the test specimen T in accordance with the decrease in the cross-sectional area, and the fixation of the benchmark fixture 50 to the test specimen T is unlikely to come off. In particular, in the case of the test specimen T in which multiple strands are twisted together as in this embodiment, the cross section of the test specimen T is easily deformed due to breakage of each strand or the wires constituting the strands, but the biasing member 83 can continue to clamp the test specimen T between the first member 60 and the second member 70. In addition, in this embodiment, since the cross-sectional shape of the groove portions 64, 74 is triangular, even if the cross-sectional area of ​​the test piece T is reduced, the test piece T and the inner surfaces 64a, 74a tend to maintain contact at four points, making it difficult for the benchmark fixing device 50 to come loose from the test piece T.

[0037] Fig. 5 is a perspective view of the marking tape 53. Note that Fig. 5 shows the marking tape 53 in a state in which it is wrapped around the fixing device main body 51, and the fixing device main body 51 is omitted.

[0038] The marking tape 53 is a flexible strip-shaped tape. The marking tape 53 has a first surface 53a on which a marking line M is provided. The marking tape 53 also has a second surface 53b which is the surface on the reverse side of the first surface 53a.

[0039] The marked line M is provided on the first surface 53a over the entire circumferential direction, i.e., the longitudinal direction of the marked line tape 53. In detail, the first surface 53a is a white surface, and the marked line M is a black straight line passing through the center of the marked line tape 53 in the pulling direction, i.e., the center of the marked line tape 53 in the lateral direction.

[0040] The marking tape 53 is wound around the first outer peripheral surface 61 and the second outer peripheral surface 71 of the fixing device main body 51 with the first surface 53a facing outward. The marking tape 53 is adhered by an adhesive member 53c with the first surface 53a at a first end in the longitudinal direction of the marking tape 53 and the second surface 53b at a second end opposite to the first end being overlapped. This connects the marking tape 53 in a ring shape. In this embodiment, the adhesive member 53c is a double-sided tape.

[0041] By connecting the marking tape 53 in a ring shape, the marking line M is provided seamlessly along the first outer peripheral surface 61 and the second outer peripheral surface 71 all around the outer periphery of the fixing device main body 51 even if the first member 60 and the second member 70 are separated from each other. Therefore, even if the marking line fixing device 50 rotates together with the test piece T due to the application of a test force, it becomes easier for the camera 31 to continue to photograph the marking line M. However, as long as the camera can continue to photograph the marking line M, the marking line M does not have to be provided all around the first outer peripheral surface 61 and the second outer peripheral surface 71.

[0042] In particular, when a tensile test is performed on a test specimen T such as a wire rope formed by twisting strands together as in this embodiment, the test specimen T may unravel as a test force is applied, causing the benchmark line fixing device 50 to rotate significantly. In contrast, by providing the benchmark line M seamlessly around the entire circumference of the benchmark line fixing device 50, the camera 31 is less likely to stop photographing the benchmark line M even if the benchmark line fixing device 50 rotates many times.

[0043] As shown in Figs. 2 to 4, the first outer peripheral surface 61 and the second outer peripheral surface 71 are formed with ribs 61a and 71a for preventing the marking tape 53 from falling off. The ribs 61a are protrusions that protrude radially outward from the first outer peripheral surface 61. The ribs 61a are formed on both ends of the first outer peripheral surface 61 in the pulling direction, over the entire circumferential direction. The ribs 71a are formed on the second outer peripheral surface 71 in the same manner as the ribs 61a. The marking tape 53 is wound around the ribs 61a and 71a formed on both ends of the outer peripheral surfaces 61 and 71 in the pulling direction. This restricts the movement of the marking tape 53 in the pulling direction by the ribs 61a and 71a, making it difficult for the marking tape 53 to fall off.

[0044] In this embodiment, the total circumferential length of the ribs 61a, 71a is set to be greater than the circumferential length of the annularly connected marked line tape 53. This makes it easier to prevent the marked line tape 53 from falling off. That is, even if the cross-sectional area of ​​the test piece T is reduced by application of a test force and the opposing surfaces 63, 73 are in contact with each other, the marked line tape 53 is caught by the ribs 61a, 71a, so that the marked line tape 53 is prevented from falling off from the fixing device main body 51.

[0045] As described above, the tensile testing machine 1 of this embodiment includes a testing machine main body 10 that applies a test force to a test specimen T to perform a tensile test, and an extensometer 30 that measures the elongation of the test specimen T. The extensometer 30 has a benchmark line fixture 50 that fixes a benchmark line M to the test specimen T, and a camera 31 that photographs the benchmark line M. The benchmark line fixture 50 clamps the test specimen T and includes a first member 60 and a second member 70 that are arranged spaced apart from each other, a support member 81 fixed to the second member 70 and supports the first member 60 so that it can move in directions toward and away from the second member 70, and a biasing member 83 that biases the first member 60 toward the second member 70. The benchmark line M is provided along the outer periphery of the first member 60 and the second member 70. As a result, as the cross-sectional area of ​​the test piece T decreases due to the application of the test force, the biasing member 83 narrows the gap between the first member 60 and the second member 70, making it easier to maintain the mark line fixing device 50 fixed to the test piece T. This makes it easier to appropriately fix the mark line M to the test piece T whose cross-sectional area decreases during testing.

[0046] [3. Modifications] The above-described embodiment is merely an example of one aspect of the present invention, and any modification and application can be made without departing from the spirit and scope of the present invention.

[0047] In the above-described embodiment, the test specimen T is described as a wire rope formed by twisting together a plurality of strands, but the configuration of the test specimen T is not limited to this. The strands may be made of fibers such as synthetic fibers, natural fibers, or glass fibers, and the test specimen T may be, for example, a stranded wire that constitutes a fishing net. The strands may also be twisted together with a fiber rope as a core. The test specimen T is not limited to being formed by twisting together strands, and may be in the shape of a rod, a wire, a plate, or any other arbitrary shape.

[0048] In the above-described embodiment, the tensile direction of the testing machine body 10 is described as being vertical. However, the tensile direction is not limited to this. For example, the tensile direction of the testing machine body 10 may be horizontal. Also, it has been described that the testing machine body 10 applies a test force to the test specimen T by rotating the threaded rod with an electric motor and displacing the crosshead 15. However, the configuration of the testing machine body 10 is not limited to this, and may be configured to apply a test force to the test specimen T by any method such as hydraulic control.

[0049] In the above-described embodiment, the first member 60 and the second member 70 are described as being made of metal, but the configuration of the benchmark fixing device 50 is not limited to this. For example, the first member 60 and the second member 70 may be made of resin or the like. In addition, the cross-sectional shape of each of the grooves 64, 74 is not limited to a right-angled isosceles triangle, and may be any shape that matches the shape of the test piece T. In addition, the biasing member 83 is not limited to a coil spring, and may be made of a leaf spring, rubber, or the like.

[0050] In the above-mentioned embodiment, the ribs 61a, 71a are provided on both ends of the first outer peripheral surface 61 and the second outer peripheral surface 71 in the pulling direction. However, the configuration of the ribs 61a, 71a is not limited thereto. For example, when the pulling direction is the vertical direction, the ribs 61a, 71a may be provided only below the marking tape 53 on the first outer peripheral surface 61 and the second outer peripheral surface 71. In this case, since the marking tape 53 is unlikely to move upward due to gravity, the ribs 61a, 71a below the marking tape 53 can prevent the marking tape 53 from falling off. In addition, the ribs 61a, 71a do not have to be configured over the entire circumferential direction of each outer peripheral surface 61, 71. In the above-mentioned embodiment, the ribs 61a, 71a are separate members, but the ribs 61a, 71a may be an integral structure, for example, a C-shaped structure.

[0051] That is, the fixing device main body 51 is not limited to a configuration having two members, the first member 60 and the second member 70, as in the above embodiment. Fig. 6 is a cross-sectional view of a benchmark fixing device 150 according to a modified example, and shows a cross section corresponding to Fig. 3. In the benchmark fixing device 150 according to the modified example, the fixing device main body 151 may be configured to be made of one member. In the modified example, the fixing device main body 151 is a substantially cylindrical member whose bottom surface is perpendicular to the tensile direction, and an outer circumferential surface 161 corresponding to the side surface of the cylinder is formed.

[0052] The fixture body 151 of the modified example is provided with a separation portion 154 that holds the test specimen T and is partly separated in a direction perpendicular to the elongation direction (tensile direction) of the test specimen T. The separation portion 154 includes a first half portion 160 and a second half portion 170. The first half portion 160 and the second half portion 170 are separated in the circumferential direction via a gap 154a, which is a space extending radially inward from the outer circumferential surface 161. The first half portion 160 and the second half portion 170 are also separated in the tensile direction perpendicularly via a support groove 154b formed on the radial inner side of the gap 154a. The support groove 154b is a groove in which the test specimen T is placed. The support groove 154b has a shape that combines the first groove portion 64 and the second groove portion 74 of the embodiment. The test specimen T comes into contact with the two inner surfaces 164a on the first half 160 side and the two inner surfaces 174a on the second half 170 side at four points. That is, the separating portion 154 holds the test specimen T. The outer peripheral surface 161 of the modified example is formed with a rib 161a for holding the marking tape 53, similar to the ribs 61a and 71a of the embodiment. As described above, the outer peripheral surface 161 is partially interrupted by the formation of the gap 154a, and the rib 161a of the modified example is C-shaped in the cross section of FIG. 6. Since the marking tape 53 is held by the C-shaped rib 161a, the marking line M is provided along the outer periphery of the marking fixture 150, i.e., along the outer peripheral surface 161.

[0053] In the modified example, the first half 160 is formed with a through hole 65 as in the embodiment, and the support member 81 is inserted through the through hole 65. The second half 170 is formed with a fastening hole 75 as in the embodiment, and the support member 81 is fastened. As a result, the support member 81 supports the spaced portion 154 so as to be movable in the direction of narrowing and widening. Therefore, the spaced portion 154 can clamp the test specimen T by using the fastening force of the support member 81. Also, as in the embodiment, in the modified example, a biasing member 83 is sandwiched between the seat surface 81c and the step surface 65c of the support member 81. The biasing member 83 biases the first half 160 in a direction approaching the second half 170. That is, the biasing member 83 biases the spaced portion 154 in a direction of narrowing. As a result, the spaced portion 154 can easily continue to clamp the test specimen T by using the biasing force of the biasing member 83.

[0054] In the above embodiment, the adhesive member 53c is described as a double-sided tape, but a hook-and-loop fastener, adhesive, or the like may be used as the adhesive member 53c. The marking tape 53 may be configured without the adhesive member 53c. For example, the marking tape 53 may be configured similarly to a wristband or the like having a wound leaf spring (spiral spring) that is stretched linearly by curving the cross section in an arch shape, and that wraps around the arm by the force of the wound leaf spring when pressed against the arm. In this case, when the marking tape 53 is pressed against each outer peripheral surface 61, 71, the cross section of the wound leaf spring is deformed linearly, and the linearly stretched wound leaf spring is wound around each outer peripheral surface 61, 71, and the marking tape 53 is deformed into an annular shape. The marking tape 53 may be eliminated, and the marking line M may be directly engraved or written on the first outer peripheral surface 61 and the second outer peripheral surface 71.

[0055] In the above embodiment, the marked line M is described as a black straight line provided on the white first surface 53a, but the configuration of the first surface 53a and the marked line M is not limited to this. The color combination of the marked line M and the first surface 53a may be any combination that allows the position of the marked line M to be identified from the photographed data of the camera 31. The shape and position of the marked line M can be changed as desired.

[0056] [4. Aspects] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0057] (Section 1) A tensile testing machine according to one embodiment includes a testing machine main body that applies a test force to a test specimen to perform a tensile test, and an extensometer that measures the elongation of the test specimen, the extensometer having a pair of benchmark fixtures that fix a benchmark to the test specimen, and a camera that photographs the benchmark, the benchmark fixture including a first member and a second member that sandwich the test specimen and are spaced apart from each other, a support member fixed to the second member and supporting the first member so as to be movable in a direction toward and away from the second member, and a biasing member that biases the first member toward the second member, and the benchmark is provided along the outer periphery of at least a portion of the first member and the second member.

[0058] According to the tensile testing machine of paragraph 1, as the cross-sectional area of ​​the test specimen decreases due to the application of the test force, the biasing member narrows the gap between the first member and the second member, making it easier to maintain the mark line fixture fixed to the test specimen. This makes it easier to properly fix the mark line to a test specimen whose cross-sectional area decreases during testing.

[0059] (Section 2) In the tensile tester described in paragraph 1, the test piece may be formed by twisting together strands.

[0060] According to the tensile testing machine of paragraph 2, the test specimen is sandwiched between the first member and the second member biased by the biasing member, so that it is easy to fix the benchmark line fixing device to a test specimen on which it is difficult to attach a sticker or the like due to the unevenness of the surface caused by the strands.

[0061] (Section 3) In the tensile testing machine described in paragraph 1 or 2, the first member may have a first outer peripheral surface curved in an arc shape and a first opposing surface opposite the first outer peripheral surface, the second member may have a second outer peripheral surface curved in an arc shape and a second opposing surface opposite the second outer peripheral surface, the first member and the second member may sandwich the test specimen between the first opposing surface and the second opposing surface, and the benchmark line may be provided along the first outer peripheral surface and the second outer peripheral surface.

[0062] According to the tensile testing machine of paragraph 3, the benchmark line is provided along the first outer peripheral surface and the second outer peripheral surface which are curved in an arc shape. Therefore, even if the benchmark line fixing device rotates as the test force is applied, it becomes easy to continue photographing the benchmark line with the camera.

[0063] (Section 4) In the tensile testing machine described in paragraph 3, a band-shaped marking tape having the marking line may be provided, the marking tape may be wrapped around the first outer peripheral surface and the second outer peripheral surface in a circular shape, and the first outer peripheral surface and the second outer peripheral surface may be provided with ribs protruding outward.

[0064] According to the tensile tester described in paragraph 4, by using a marking tape with marking lines, the marking lines can be arranged even between the first and second components that are separated from each other while the ribs prevent the marking lines from falling off, making it easier to continue photographing the marking lines with the camera.

[0065] (Section 5) In the tensile testing machine described in paragraph 3 or 4, a groove portion in which the test specimen is placed may be formed in each of the first opposing surface and the second opposing surface, and each of the groove portions may be configured to extend in a tensile direction of the test specimen and have a triangular cross-sectional shape.

[0066] According to the tensile tester described in item 5, even if the cross-sectional area of ​​the test specimen is reduced, the test specimen and the inner surface of the groove tend to continue to be in contact with each other, and the benchmark fixture is less likely to come loose from the test specimen T.

[0067] (Section 6) A benchmark fixture according to one embodiment is a benchmark fixture that fixes a benchmark for measuring the elongation of a test specimen for a tensile test, and includes a first member and a second member that clamp the test specimen and are arranged at a distance from each other, a support member that is fixed to the second member and supports the first member so that the first member can move in directions toward and away from the second member, and a biasing member that biases the first member toward the second member, and the benchmark is provided along the outer periphery of the first member and the second member.

[0068] According to the benchmark fixture of paragraph 6, as the cross-sectional area of ​​the test specimen decreases due to the application of the test force, the biasing member narrows the gap between the first member and the second member, making it easier to maintain the benchmark fixture fixed to the test specimen. This makes it easier to properly fix the benchmark to a test specimen whose cross-sectional area decreases during testing.

[0069] (Section 7) A benchmark line fixture in one embodiment is a benchmark line fixture that fixes a benchmark line for measuring the elongation of a test specimen for a tensile test to the test specimen, and is provided with a support member that clamps the test specimen and has a separation portion, a portion of which is spaced apart in a direction perpendicular to the elongation direction of the test specimen, and that movably supports the separation portion in directions narrowing and widening, and a biasing member that biases the separation portion in the direction narrowing, and the benchmark line is provided along the outer periphery of the benchmark line fixture.

[0070] According to the mark line fixing device of claim 7, the spaced apart portion can easily continue to clamp the test piece by utilizing the biasing force of the biasing member. [Explanation of symbols]

[0071] 1 Testing Machine 10 Testing machine body 30 Extensometer 31 Camera 50 Mark line fixture 53 Marking tape 60 First member 61 1st outer peripheral surface 61a Rib 63 First opposing surface 64 First groove (groove) 70 Second member 71 Second outer peripheral surface 71a Rib 73 Second opposing surface 74 Second groove (groove) 81 Support member 83 Pressing member 150 Mark line fixture 154 Separation part M mark line T test specimen

Claims

1. A testing machine body for performing a tensile test by applying a test force to a test specimen; An extensometer for measuring the elongation of the test specimen; The extensometer has a pair of mark line fixing devices that fix a mark line to the test piece and a camera that photographs the mark line, the marked line fixing device includes a first member and a second member that sandwich the test piece and are arranged spaced apart from each other, a support member that is fixed to the second member and supports the first member movably in a direction approaching and moving away from the second member, and a biasing member that biases the first member toward the second member, The markings are provided along the outer periphery of at least a portion of the first member and the second member. Tensile testing machine.

2. The test specimen is formed by twisting strands together. The tensile testing machine according to claim 1.

3. The first member has a first outer circumferential surface curved in an arc shape and a first opposing surface opposite to the first outer circumferential surface, The second member has a second outer circumferential surface curved in an arc shape and a second opposing surface opposite to the second outer circumferential surface, The first member and the second member sandwich the test object between the first opposing surface and the second opposing surface, The marking lines are provided along the first outer peripheral surface and the second outer peripheral surface. The tensile testing machine according to claim 2.

4. A band-shaped marking tape having the marking lines is provided, The marking tape is wound around the first outer peripheral surface and the second outer peripheral surface in an annular shape, The first outer circumferential surface and the second outer circumferential surface are provided with ribs protruding outward. The tensile testing machine according to claim 3.

5. A groove in which the test body is placed is formed on each of the first opposing surface and the second opposing surface, Each of the grooves extends in the tensile direction of the test specimen and has a triangular cross-sectional shape. The tensile testing machine according to claim 3.

6. A gauge fixture for fixing a gauge for measuring the elongation of a test specimen for a tensile test, comprising: a first member and a second member that sandwich the test specimen and are disposed apart from each other; a support member fixed to the second member and supporting the first member movably in a direction approaching and moving away from the second member; a biasing member that biases the first member toward the second member, The marking lines are provided along the outer periphery of the first member and the second member. Mark line fixture.

7. A gauge fixture for fixing a gauge for measuring the elongation of a test specimen for a tensile test, comprising: The test specimen is sandwiched between the test pieces, and a part of the test pieces has a separation portion that is separated in a direction perpendicular to the elongation direction of the test specimen, a support member that supports the spaced portion so as to be movable in a direction narrowing the spaced portion and a direction widening the spaced portion; a biasing member that biases the spaced portion in a narrowing direction, The mark line is provided along the outer periphery of the mark line fixture. Mark line fixture.

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