JP7806463B2 - Video-type non-contact extensometer and material testing machine - Google Patents

Description

The present invention relates to a video-type non-contact extensometer and a materials testing machine.

BACKGROUND ART Conventionally, a video-type non-contact extensometer for measuring the elongation of a test specimen in a material testing machine has been known (see, for example, Patent Document 1).
In such a video-type non-contact extensometer, for example, marked lines are placed at a predetermined interval on the surface of a test specimen, and the marked lines are photographed with a camera when a test load is applied to the test specimen. The displacement of the gauge line distance is calculated based on the photographic data of the marked lines photographed by the camera, thereby measuring the elongation of the test specimen. Here, the position of the marked lines in the photographic data is based on the position on the camera's image sensor where the marked lines are imaged by the camera lens. Therefore, if the distance between the camera and the test specimen changes, the position of the marked lines in the photographic data also changes. Therefore, a video-type non-contact extensometer is generally calibrated based on a predetermined distance, and the marked lines are photographed with the camera positioned so that the distance between the camera and the test specimen is the predetermined distance.
Regarding the adjustment of the camera position, Patent Document 1 discloses that the camera is positioned relative to the test piece by adjusting the fixing position of the arm on the support and the bending degree of the arm.

JP 2012-47465 A

However, even if a test specimen is formed to a specified standard, there will actually be variations based on significant figures. For example, consider a case where a steel bar, as an example of a test specimen, has a specified diameter. In this case, when the steel bar is set in the testing machine body, the center position of the steel bar can be considered constant regardless of the steel bar, but the diameter of the steel bar will have variations based on significant figures. For this reason, the distance between the surface of the steel bar and the camera will likely vary for each steel bar, which will easily lead to errors in measuring elongation. Therefore, when measuring the elongation of a test specimen, it is desirable to measure the test specimen for each specimen and adjust the position of the camera according to the measurement results.

However, in the configuration described in Patent Document 1, the camera position is adjusted by moving the camera in accordance with the graduations on a scale, etc. Therefore, the work of measuring each test object and adjusting the camera position in accordance with the graduations can easily become cumbersome.
Furthermore, in a configuration where the camera is adjusted to a scale, some workers may easily misread the scale, which may prevent them from adjusting the camera position with high precision.
The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a video-type non-contact extensometer that makes it easy for anyone, regardless of the operator, to easily and accurately adjust the position of the camera so that the distance between the camera and the test piece is a predetermined distance.

A first aspect of the present invention relates to a video non-contact extensometer that includes a camera that photographs a test specimen having marked lines at predetermined intervals, and measures the elongation of the test specimen from the displacement of the marked lines based on the photographic data captured by the camera when the camera is positioned so that the distance to the test specimen is a predetermined distance. The video non-contact extensometer includes: a support bar having a longitudinal shape that extends in a direction toward or away from the test specimen; a moving mechanism supported by the support bar, the moving mechanism including a moving member supported so as to be movable in the longitudinal direction of the support bar; the camera fixed to the moving member; a rangefinder that is provided integrally with the camera and that measures the distance to the test specimen in a non-contact manner; and a display unit that is provided integrally with the camera and that displays the measured distance , and the moving mechanism includes a position adjustment screw that moves the moving member relative to the support bar in a direction toward or away from the test specimen .

A second aspect of the present invention relates to a materials testing machine comprising: a testing machine main body that applies a test load to a test specimen; and a video non-contact extensometer that is equipped with a camera that photographs the test specimen, which has marked lines at predetermined intervals, and that measures the elongation of the test specimen from the displacement of the marked lines based on the photographic data captured by the camera when the camera is positioned so that the distance to the test specimen is a predetermined distance. The video non-contact extensometer comprises: a support bar having a longitudinal shape that extends in a direction toward or away from the test specimen; a moving mechanism supported by the support bar, the moving mechanism comprising a moving member supported so as to be movable in the longitudinal direction of the support bar; the camera fixed to the moving member; a rangefinder that is integral with the camera and that measures the distance to the test specimen in a non-contact manner ; and a display unit that is integral with the camera and that displays the measured distance ; and the moving mechanism comprises a position adjustment screw that moves the moving member relative to the support bar in a direction toward or away from the test specimen .

In the first and second aspects of the present invention, a rangefinder is integrated into the camera, making it easy for any operator to easily and accurately align the camera position so that the distance between the camera and the test piece is the specified distance.

FIG. 1 is a front view of a material testing machine according to an embodiment. FIG. 1 is a plan view of a material testing machine according to an embodiment. FIG. 1 is a diagram showing the main parts of a video-type non-contact extensometer. FIG. 1 is a view of the main parts of a video-type non-contact extensometer as seen from the test specimen side. FIG. 2 is a diagram schematically illustrating an X-axis stage.

Embodiments of the present invention will be described below with reference to the drawings.

1. Embodiment
Fig. 1 is a front view of a material testing machine 1 according to an embodiment. Fig. 2 is a plan view of the material testing machine 1 according to an embodiment.
The material testing machine 1 according to the embodiment is a material testing machine capable of applying a test load to a test specimen T whose ends are gripped by upper and lower gripping tools 18 and 19 in a tensile direction, which is the direction in which the distance between the upper and lower gripping tools 18 and 19 widens.

The material testing machine 1 of this embodiment includes a testing machine main body 10 that applies a test load to a test specimen T, a video-type non-contact extensometer 30 that measures the elongation of the test specimen T to which the test load is applied by the testing machine main body 10, and a control device 100 that controls the testing machine main body 10 and other components.

The testing machine main body 10 has a base 11 that is installed on the floor. A ram cylinder 12 is placed on the base 11. The ram cylinder 12 has a ram 12A that can be raised and lowered hydraulically. A hydraulic source (not shown) is connected to the ram cylinder 12. The hydraulic pressure inside the ram cylinder 12 is measured by a pressure cell (not shown) and input to the control device 100. A rectangular plate-shaped table 13 is fixed to the upper end of the ram 12A. The table 13 can be raised and lowered by the ram cylinder 12.

As shown in Figure 2, a pair of support columns 14 are arranged in the first diagonal direction on the table 13. An upper crosshead 15 extending in the width direction is supported across the top of the pair of support columns 14. The pair of support columns 14 and the upper crosshead 15 rise and fall together with the table 13.

A pair of through-holes (not shown) are formed in the table 13 in the second diagonal direction, penetrating the thickness direction. Threaded rods 16 extending in the vertical direction are inserted into the through-holes, respectively. The threaded rods 16 are erected on the base 11 below the table 13. A lower crosshead 17 extending in the width direction is suspended above the threaded rods 16 above the table 13. The lower crosshead 17 is supported by the threaded rods 16 via a nut (not shown). When this nut is rotated by a drive source (not shown), the lower crosshead 17 rises and falls along the threaded rods 16. This allows the height of the lower crosshead 17 to be set.

The upper crosshead 15 and the lower crosshead 17 are provided with grippers 18 and 19 for gripping the test specimen T, respectively.
With the lower crosshead 17 set to a predetermined height and both ends of the test specimen T gripped by the grippers 18 of the upper crosshead 15 and the grippers 19 of the lower crosshead 17, the table 13 is moved upward, whereby the upper crosshead 15 rises relative to the lower crosshead 17 and a tensile load is applied to the test specimen T. As the test specimen T, for example, a test piece, a steel bar, a deformed steel bar, etc. may be used.

In the testing machine main body 10 according to this embodiment, an upper platen 20 is provided on the underside of the lower crosshead 17, and a lower platen 21 is provided on the upper surface of the table 13. A test specimen T, such as concrete, is sandwiched between the upper platen 20 and the lower platen 21, and a compressive load can be applied to the test specimen T by moving the table 13 upward.

Fig. 3 is a diagram showing the main parts of the video non-contact extensometer 30. In Fig. 3, the main parts of the video non-contact extensometer 30 are viewed from the side of the materials testing machine 1. Fig. 4 is a diagram showing the main parts of the video non-contact extensometer 30 as viewed from the side of the test piece T.
The video-type non-contact extensometer (hereinafter referred to as "extensometer") 30 is equipped with cameras 51 and 52 that photograph a test specimen T, which has marked lines M1 and M2 spaced a predetermined distance apart. When a load is applied to the test specimen T by the testing machine main body 10, the extensometer 30 photographs the marked lines M1 and M2 of the test specimen T using the cameras 51 and 52, detects the positions of the marked lines based on the photographic data captured by the cameras 51 and 52, and measures the elongation of the test specimen T from the displacement of the marked lines M1 and M2.
The benchmark lines M1 and M2 are provided on the test piece T by attaching a sticker bearing a mark indicating the benchmark lines M1 and M2 to the test piece T.

The extensometer 30 according to this embodiment has a pole 31 that extends vertically. The pole 31 is fixed to, for example, the floor. A support bar 32 that extends horizontally is supported on the pole 31. The support bar 32 is formed in a rectangular cylindrical shape. The support bar 32 is fixed to the pole 31 via a clamper 33. The clamper 33 is configured to be movable vertically along the pole 31 and rotatable around the pole 31. The support bar 32 is also slidable horizontally relative to the clamper 33. The clamper 33 is fixed to the pole 31 by operating the lever 33A of the clamper 33. This fixes the vertical position of the support bar 32 while preventing it from rotating relative to the pole 31. The support bar 32 is also fixed to the pole 31 at a predetermined longitudinal position.

The camera unit 50 is supported at the first longitudinal end of the support bar 32. The weight 34 is supported at the second longitudinal end of the support bar 32. The weight 34 allows the center of gravity of the weight applied to the support bar 32 to be closer to the pole 31. The weight 34 allows the longitudinal support bar 32 to extend horizontally, making it easier to secure the bar to the pole 31 in a stable manner.

FIG. 5 is a diagram showing a schematic diagram of the X-axis stage 40. As shown in FIG.
4 and 5, an X-axis stage 40, which is an example of a movement mechanism, is provided at a first longitudinal end of the support bar 32. The X-axis stage 40 is configured to be movable in a linear direction in the horizontal direction toward and away from the test piece T. In the following, the horizontal direction toward and away from the test piece T will be referred to as the front-to-rear direction. Furthermore, the direction in which the cameras 51, 52 move away from the test piece T will be referred to as the front, and the direction in which the cameras 51, 52 approach the test piece T will be referred to as the rear.

The X-axis stage 40 has a housing 41. The housing 41 is fixed to the underside of the support bar 32. A moving stage 42, which is an example of a moving member, is supported on the housing 41 so that it can move in the front-to-rear direction. In this embodiment, a dovetail groove 41A (see Figure 4) is formed in the housing 41, and the moving stage 42 is configured to move in the front-to-rear direction along the dovetail groove 41A.

A position adjustment screw 43 is provided on the housing 41. The position adjustment screw 43 has a knob 43A and a threaded shaft 43B extending forward from the knob 43A. The position adjustment screw 43 is rotatably supported on the housing 41. The position adjustment screw 43 is supported so as to be immovable relative to the housing 41 in the axial direction of the position adjustment screw 43, i.e., the front-to-rear direction. The threaded shaft 43B of the position adjustment screw 43 is fitted into a threaded hole 42B of the moving stage 42. The threaded hole 42B is formed in a columnar threaded hole 42A provided on the moving stage 42. When an operator grips the knob 43A and rotates the position adjustment screw 43 forward or backward, the moving stage 42 moves forward or backward.

A position fixing screw 44 is provided on the housing 41. The position fixing screw 44 has a knob 44A and a threaded shaft 44B extending from the knob 44A. The threaded shaft 44B extends in a direction intersecting the threaded shaft 43B of the position adjustment screw 43. The threaded shaft 44B is threaded into the housing 41, and the tip of the threaded shaft 44B is configured to be able to move toward and away from the moving stage 42. When an operator grips the knob 44A and screws in the position fixing screw 44, the threaded shaft 44B abuts against the moving stage 42, fixing the position of the moving stage 42 in the front-to-rear direction.

A camera unit 50 is integrally supported on the moving stage 42. The camera unit 50 integrally includes cameras 51 and 52 and a range finder 53 that measures the distance to the test piece T in a non-contact manner.
3 and 4, the camera unit 50 of this embodiment has a pair of upper and lower cameras 51, 52. The pair of upper and lower cameras 51, 52 are fixed to the moving stage 42 via a frame 54 extending in the vertical direction. The cameras 51, 52 are supported at both upper and lower ends of the frame 54, respectively.

In this embodiment, the pair of upper and lower cameras 51, 52 have the same configuration. The cameras 51, 52 are positioned with their lenses 51A, 52A facing the test specimen T. The pair of upper and lower cameras 51, 52 are positioned so that the distances from the lenses 51A, 52A to the test specimen T are the same distance D1. By moving the moving stage 42 using the position adjustment screw 43, the distances to the test specimen T for the pair of upper and lower cameras 51, 52 can be set to the same distance D1. Furthermore, the cameras 51, 52 can capture images of the marked lines M1, M2 when they are separated by the same distance D1 from the test specimen T. Note that the extensometer 30 in this embodiment is calibrated based on a predetermined distance D0. In other words, when the cameras 51, 52 are positioned so that the distance D1 between the cameras 51, 52 and the test specimen T is the predetermined distance D0, the positions of the marked lines M1, M2 can be detected with high accuracy.

The upper camera 51 captures an image of the test piece T within a predetermined range, including the upper marked line M1. The lower camera 52 captures an image of the test piece T within a predetermined range, including the lower marked line M2. As a result, even if the test piece T extends and the marked lines M1 and M2 move, each marked line M1 and M2 is captured by each camera 51, 52. The captured data from cameras 51 and 52 is transmitted to the control device 100 via a signal cable (not shown).

The camera unit 50 has a rangefinder 53. The rangefinder 53 measures the distance to the test piece T in a non-contact manner. The rangefinder 53 is fixed to the moving stage 42 via a folded plate-shaped frame 55. More specifically, the frame 55 has a side surface 55A extending along the frame 54. The side surface 55A is positioned to the side of the frame 54, which extends vertically. The rangefinder 53 is fixed to the side surface 55A by a pair of front and rear square frame-shaped fixing members 56, 56. The rangefinder 53 is positioned centrally between the upper camera 51 and the lower camera 52. The rangefinder 53 is integral with the cameras 51, 52 and is located near the cameras 51, 52. In this embodiment, the rangefinder 53 is a laser rangefinder. The rangefinder 53 irradiates the test piece T with laser light L having a small spot diameter and measures the distance to the test piece T based on the reflected laser light L.

The camera unit 50 is equipped with a digital display 57. The digital display 57 digitally displays the distance measured by the rangefinder 53. The digital display 57 is configured with an LCD display or the like. The digital display 57 is provided integrally with the cameras 51 and 52. In this embodiment, the digital display 57 is provided on the rangefinder 53. The digital display 57 is exposed on the side between the fixing members 56. The operator can recognize the distance from the test specimen T to the camera 51 from the digitally displayed distance. Furthermore, because the digital display 57 is integrated with the cameras 51 and 52, it is easy to align the positions of the cameras 51 and 52 while looking at the digital display 57. In particular, because the position adjustment screw 43 is located near the digital display 57, it is possible to operate the position adjustment screw 43 while looking at the digital display 57. Furthermore, this makes it easier to reduce operator misreadings compared to adjusting the positions of the cameras 51 and 52 according to the scale.

In this embodiment, the rangefinder 53 is positioned offset forward by a distance D2 relative to the cameras 51 and 52. Here, the digital display unit 57 displays the distance D1+D2 from the rangefinder 53 to the test piece T, but the digital display unit 57 may also be configured to subtract the distance D2 from the distance D1+D2 and display the resulting distance D1.

The camera unit 50 of this embodiment is made up of cameras 51 and 52, rangefinder 53, frames 54 and 55, fixing member 56, digital display unit 57, etc. The cameras 51 and 52, rangefinder 53, and digital display unit 57 can move together in the forward and backward directions along with the moving stage 42. Because the moving stage 42 is mounted on the underside of the support bar 32, the camera unit 50, which tends to be heavy, is mounted below the support bar 32.

A lighting fixture 60 is provided on the opposite side of the support bar 32 from the camera unit 50. The lighting fixture 60 is fixed via a frame 61. The frame 61 is fixed to the upper surface of the support bar 32. The lighting fixture 60 extends in the vertical direction. The lighting fixture 60 illuminates the marked lines M1 and M2 of the test piece T. Because the lighting fixture 60 is provided on the opposite side of the support bar 32 from the camera unit 50, the light from the lighting fixture 60 is less likely to be blocked regardless of the positions of the cameras 51 and 52 of the camera unit 50.
A light shielding plate 62 (see FIG. 2) is disposed on the back of the testing machine main body 10. The light shielding plate 62 can, for example, prevent indoor illumination light from entering the cameras 51 and 52, thereby preventing erroneous detection of the positions of the marked lines M1 and M2.

1, a control device 100 that controls each part of the material testing machine 1 is arranged next to the testing machine main body 10. The control device 100 is a device that centrally controls the material testing machine 1, and is connected to the testing machine main body 10 and the extensometer 30 so that signals can be transmitted and received between them.
The signals received by the control device 100 from the testing machine main body 10 and the extensometer 30 include measurement signals for the oil pressure of the ram cylinder 12, video signals from the cameras 51 and 52, and appropriate signals required for control and testing.
The signals sent by the control device 100 to the testing machine main body 10 and the extensometer 30 include control signals for the hydraulic cylinder, control signals for a drive source (not shown) for raising and lowering the lower crosshead 17, and other appropriate signals required for control and testing.

The control device 100 includes a computer that includes a processor such as a CPU (Central Processing Unit) or MPU (Micro-Processing Unit), a memory device such as a ROM (Read Only Memory) or RAM (Random Access Memory), a storage device such as an HDD (Hard Disk Drive) or SSD (Solid State Drive), and an interface circuit for connecting the control device 100 and various peripheral devices. The processor executes computer programs stored in the memory device or storage device to realize the various functions of the materials testing machine 1.

In this embodiment, the control device 100 controls the materials testing machine 1 upon receiving an input operation to start a test. That is, the control device 100 controls the testing machine main body 10 to apply a test load to the test specimen T. The control device 100 also calculates the elongation of the test specimen T. Specifically, the control device 100 acquires video signals, i.e., image data, from the cameras 51 and 52. The control device 100 detects the positions of the marking lines M1 and M2 based on the image data. The control device 100 calculates the displacement of the marking lines M1 and M2 based on the positions of the marking lines M1 and M2 and the positions of the marking lines M1 and M2 at the start of the test. The control device 100 also calculates the displacement of the marking line distance, i.e., the elongation of the test specimen T, based on the initial marking line distance, the displacement of the upper marking line M1, and the displacement of the lower marking line M2.

Next, the operation of this embodiment will be described.
When measuring elongation with the extensometer 30, the test specimen T is set with its upper and lower ends gripped by the grippers 18 and 19. Also, the test specimen T is marked with benchmark lines M1 and M2 spaced a predetermined distance apart.
The operator adjusts the positions of the cameras 51 and 52 so that the distance D1 between the test piece T and the cameras 51 and 52 becomes the preset distance D0.

Here, with the extensometer 30, the distance D1 between the test specimen T and the cameras 51, 52 has a significant effect on measurement accuracy. For example, if the preset distance D0 is set to 500 mm and the distance D1 between the test specimen T and the cameras 51, 52 deviates from the distance D0 by 1 mm, an error of approximately 1/500, or 0.2%, will occur. Therefore, in order to minimize errors in measurements with the extensometer 30, it is important to accurately align the distance D1 between the test specimen T and the cameras 51, 52 with the calibrated preset distance D0.

In this embodiment, the rangefinder 53 is integrated with the cameras 51 and 52. This allows the operator to easily and accurately determine the distance D1 between the cameras 51 and 52 and the test specimen T using the rangefinder 53. Therefore, the operator can easily align the cameras 51 and 52 while checking whether the distance D1 between the cameras 51 and 52 and the test specimen T is equal to distance D0 based on the rangefinder 53, making it easier to adjust the positions of the cameras 51 and 52 so that the distance D1 between the cameras 51 and 52 and the test specimen T is equal to distance D0. In particular, the rangefinder 53 measures the distance D1 between the test specimen T and the cameras 51 and 52 after it has been set in the testing machine main body 10. Therefore, there is no need to measure the size of the test specimen T to align the cameras 51 and 52 before setting them, making testing easier.

In addition, in this embodiment, digital display units 57 are provided integrally with cameras 51 and 52, and the distance D1 is displayed digitally near cameras 51 and 52. This makes it easy to adjust the positions of cameras 51 and 52 while viewing the digitally displayed distance D1.

In addition, in this embodiment, the camera unit 50 is configured to be movable by the X-axis stage 40. This allows the positions of the cameras 51 and 52 to be moved in the forward and backward directions with high precision. Furthermore, for example, large adjustments to the positions of the cameras 51 and 52 can be made by changing the clamp position of the support bar 32, and fine adjustments to the positions of the cameras 51 and 52 can be made using the position adjustment screws 53. Therefore, when continuously testing test specimens T of a specified standard, the positions of the cameras 51 and 52 can be roughly adjusted by changing the clamp position of the support bar 32 to match the specified standard, and the positions of the cameras 51 and 52 can be fine-tuned using the position adjustment screws 53 to match variations in the size of the test specimens T.

In addition, in this embodiment, the distance meter 53 is a laser distance meter. Therefore, the distance D1 to the test piece T is measured with high precision using the laser light L, which has a small spot diameter, making it easier to align the camera position with high precision. In particular, when the test piece T has an uneven surface, such as a deformed steel bar, the small spot diameter of the laser distance meter makes it easy to determine which of the uneven surfaces of the uneven surface is being measured. Therefore, elongation can be measured with higher precision than when it is difficult to determine which of the uneven surfaces is measuring the distance D1. The distance meter 53, which is a laser distance meter, is suitable as the distance meter in the extensometer 30 of the materials testing machine 1.

When the operator adjusts the positions of the cameras 51 and 52 so that the distance D1 between the test specimen T and the cameras 51 and 52 is the preset distance D1 using the distance meter 53, the operator inputs an operation to start the test into the control device 100. This causes the testing machine main body 10 to apply a tensile load to the test specimen T. Additionally, the extensometer 30 measures the elongation based on the photographic data of the benchmark lines M1 and M2. Because the distance D1 between the test specimen T and the cameras 51 and 52 is accurately matched to the distance D0, the elongation of the test specimen T can be easily detected with minimal measurement error.

Therefore, in this embodiment, it is easier to suppress dimensional errors in the test specimen T and adjustment errors by the operator, making it possible to significantly reduce elongation errors compared to when the rangefinder 53 is not integrated into the cameras 51 and 52.

2. Modifications
The above-described embodiment merely exemplifies one aspect of the present invention, and any modifications and applications are possible without departing from the spirit of the present invention.

In the above-described embodiment, the testing machine main body 10 of the material testing machine 1 is configured to apply a load to the test specimen T by hydraulic control. However, the configuration of the extensometer 30 of this embodiment can be applied to material testing machines that apply a load to the test specimen T by any method, such as a configuration in which a threaded rod is driven by an electric motor to apply a load to the test specimen T.

In the above-described embodiment, a pair of cameras 51, 52 are provided, one above the other, but the number of cameras is not limited to two. It may be one camera, or three or more cameras. Furthermore, in the above-described embodiment, the upper camera 51 photographs the vicinity of the upper marked line M1, and the lower camera 52 photographs the vicinity of the lower marked line M2. However, the cameras may photograph both the upper and lower marked lines M1, M2. Furthermore, the cameras may be configured to photograph using cameras with different angles of view and different field of view. In other words, the camera configuration is not particularly limited as long as they are capable of measuring the elongation of the test specimen using the marked lines.

In the above-described embodiment, the distance meter 53 is a laser distance meter. Laser distance meters are desirable for extensometers because the spot diameter of the laser light is small, but instead, non-contact distance meters such as ultrasonic distance meters or infrared distance meters may also be used.

In the above-described embodiment, the position adjustment screw 43 is configured to be operated by an operator, but the position adjustment screw 43 may also be configured to be electrically controlled. For example, the distance data measured by the rangefinder 53 may be input to the control device 100, and the control device 100 may control the electric motor to rotate the position adjustment screw 43 based on the distance data so that the distance D1 between the cameras 51, 52 and the test piece T becomes a predetermined distance D0.

In the above-described embodiment, the camera unit 50 is described as being supported by a pole 31 fixed to the floor, but it may also be fixed to the testing machine main body 10. For example, the support bar 32 may be clamped to the threaded rod 16.

In the above-described embodiment, the calculation of the elongation of the extensometer 30 is performed by the control device 100 that controls the testing machine main body 10. However, the extensometer 30 may also be equipped with its own control device separate from the control device 100, and the image data captured by the cameras 51 and 52 may be sent to the extensometer 30's own control device, which may then calculate the elongation.

It will be understood by those skilled in the art that the exemplary embodiments and variations described above are specific examples of the following aspects:

(Section 1)
A video-type non-contact extensometer according to one embodiment includes a camera that photographs a test specimen having markings at predetermined intervals, and measures the elongation of the test specimen from the displacement of the markings based on the photographic data captured by the camera when the camera is positioned so that the distance to the test specimen is a predetermined distance. The video-type non-contact extensometer may also include a rangefinder that is integral with the camera and measures the distance to the test specimen non-contact.

With the video-type non-contact extensometer described in paragraph 1, a distance meter is integrated into the camera, making it easy for any operator to easily and accurately align the camera position so that the distance between the camera and the test specimen is the specified distance.

(Section 2)
The video type non-contact extensometer described in paragraph 1 may further include a display unit that digitally displays the measured distance, and the display unit may be provided integrally with the camera.

The video-type non-contact extensometer described in paragraph 2 makes it easy to align the camera while looking at the display. Furthermore, the digital display makes it easier to prevent operators from misreading the data.

(Section 3)
The video-type non-contact extensometer described in paragraph 1 or 2 may further comprise a moving member to which the camera is fixed, a position adjustment screw that moves the moving member in a direction toward or away from the test piece, and a position fixing screw that fixes the position of the moving member.

The video-type non-contact extensometer described in paragraph 3 allows the camera position to be adjusted with a simple configuration, and the distance between the test specimen and the camera can be set with high precision.

(Section 4)
In the video type non-contact extensometer according to any one of paragraphs 1 to 3, the distance meter may be a laser distance meter.

With the video-type non-contact extensometer described in paragraph 4, the laser distance meter has a small laser light spot diameter, making it easy to determine which surface of the test piece is being measured. Therefore, compared to when this determination is not possible, the elongation of test pieces of various shapes can be measured with greater accuracy.

(Section 5)
One embodiment of a materials testing machine is a materials testing machine comprising: a testing machine main body that applies a test load to a test specimen; a camera that photographs the test specimen, which has markings at predetermined intervals, and a video non-contact extensometer that measures the elongation of the test specimen from the displacement of the markings based on the photographic data captured by the camera when the camera is positioned so that the distance to the test specimen is a predetermined distance; and the video non-contact extensometer may also comprise a distance meter that is integral with the camera and measures the distance to the test specimen non-contact.

In the materials testing machine described in paragraph 5, a rangefinder is integrated into the camera, making it easy for any operator to easily and accurately align the camera position so that the distance between the camera and the test piece is the specified distance.

1 Material testing machine 10 Testing machine body 30 Extensometer (video type non-contact extensometer)
42 moving stage (moving member)
43 Position adjustment screw 44 Position fixing screw 51, 52 Camera 53 Rangefinder (laser rangefinder)
57 Display unit D0 Predetermined distance D1 Distance to test piece M1, M2 Marked lines T Test piece

Claims (7)

A video-type non-contact extensometer is provided with a camera that photographs a test specimen having marked lines at predetermined intervals, and measures the elongation of the test specimen from the displacement of the marked lines based on photographic data taken by the camera while the camera is positioned so that the distance to the test specimen is a predetermined distance,
a support bar having a longitudinal shape extending in a direction approaching and separating from the test body;
a movement mechanism supported by the support bar, the movement mechanism including a movement member supported so as to be movable in a longitudinal direction of the support bar;
the camera fixed to the moving member;
a range finder that is provided integrally with the camera and that measures the distance to the test piece in a non-contact manner;
a display unit that is provided integrally with the camera and that displays the measured distance ,
the moving mechanism includes a position adjustment screw that moves the moving member toward and away from the test piece relative to the support bar.
Video type non-contact extensometer. A pole extending in the vertical direction;
the horizontally extending support bar supported by the pole;
the moving mechanism supported on a first end side of the support bar in the longitudinal direction;
a weight supported on a second end side of the support bar in the longitudinal direction to shift the center of gravity of the weight applied to the support bar toward the pole;
10. The video non-contact extensometer of claim 1, comprising: The display unit digitally displays the distance .
3. The video type non-contact extensometer according to claim 1 or 2 . a position fixing screw for fixing the position of the moving member;
4. The video type non-contact extensometer according to claim 1. The rangefinder is a laser rangefinder.
5. The video type non-contact extensometer according to claim 1. a testing machine main body that applies a test load to a test specimen;
A material testing machine comprising: a camera that photographs the test specimen having marked lines at predetermined intervals; and a video non-contact extensometer that measures the elongation of the test specimen from the displacement of the marked lines based on photographic data taken by the camera while the camera is positioned so that the distance to the test specimen is a predetermined distance;
a support bar having a longitudinal shape extending in a direction approaching and separating from the test body;
a movement mechanism supported by the support bar, the movement mechanism including a movement member supported so as to be movable in a longitudinal direction of the support bar;
the camera fixed to the moving member;
a range finder that is provided integrally with the camera and that measures the distance to the test piece in a non-contact manner;
The video non-contact extensometer includes a display unit that is integrated with the camera and displays the measured distance ,
the moving mechanism includes a position adjustment screw that moves the moving member toward and away from the test piece relative to the support bar.
Material testing machine. A pole extending in the vertical direction;
the horizontally extending support bar supported by the pole;
the moving mechanism supported on a first end side of the support bar in the longitudinal direction;
The video type non-contact extensometer includes a weight supported on a second end side of the support bar in the longitudinal direction to shift the center of gravity of the weight applied to the support bar toward the pole.
7. A material testing machine according to claim 6.