JP3236088B2 - Tensile test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a television camera.
La, to a tensile testing machine to measure the tensile properties of Using Multiple to materials scanning device, such as a record over Heather scanner camera.

[0002]

2. Description of the Related Art A tensile tester for measuring tensile properties of materials such as rubber, resin, fiber, etc., such as tensile strength, elongation stress, or elongation at break, uses a chuck to hold both ends of a test piece made of the above material. The test piece is configured to be grasped, one of the chucks is moved, and the test piece is pulled to give elongation deformation. With such a tensile tester, for example, 100
In order to measure the elastic modulus at% elongation, the tester must confirm the point at which the test piece has been stretched to 100% while constantly observing how the test piece elongates with the naked eye. For this reason, the measurement operation requires a high level of skill of the tester, and when the level of skill is low, a measurement error may occur.

In order to solve the problem of a measurement error that occurs depending on the skill level of a person in charge of testing, the inventors of the present invention provide measurement marks having different optical characteristics on a test piece and display the mark on a television. Japanese Patent Publication No. 56-19882 and Japanese Patent Publication No. 56-19882 disclose a tensile tester for automatically measuring by using a scanning device such as a camera (hereinafter simply referred to as a TV camera).
It has already been proposed by, for example, -18086.

[0004] On the other hand, it takes 5 to break such as rubber.
For a material that undergoes a large deformation of up to 10 times, it may be necessary to examine not only the elongation characteristics at the time of the large deformation but also the characteristics at the time of a minute deformation in a low elongation region. However, since the measurement of the tensile properties at the time of such minute deformation requires more and more skill, a tensile test apparatus using the TV camera is suitable for measuring the minute deformation.

[0005] However, in the tensile test apparatus using the above-mentioned conventionally proposed TV camera, if the TV camera is brought close to the test piece, a minute elongation change can be accurately read, but there is a limit in one TV camera. On the other hand, a large extension area deviates from the field of view of the TV camera, so that it cannot be measured, and there is a problem that the reading accuracy when the distance is increased is reduced.

That is, there is an inconvenience that the measurement at the time of minute deformation and the measurement at the time of large deformation cannot be performed at the same time by a single measurement operation, and there is a problem that the working efficiency is not improved. Such a problem is the same not only when using a TV camera but also when using a line sensor camera or a laser scanner camera as a scanning device.

[0007]

Therefore, to solve the above-mentioned problems, the present inventors have detected the elongation of a test specimen from a small deformation to a large deformation with high accuracy (within ± 0.2 elongation). As a way to do this, install two or more TV cameras,
According to the elongation of the test piece, for example, a zoom lens attached to a TV camera has been proposed (JP-A-63-269040, JP-A-1-250006). However, as a result of repeating various experiments, in the case of adjusting the zoom lens according to the elongation of the test piece, it takes a long time to automatically adjust the focus of the lens, and the elongation of the test piece during that time increases the accuracy of elongation measurement. It turned out that there was a problem and it was difficult to make high-precision measurements.

The present invention has been devised in view of such a conventional problem, and is intended to move a scanning device in accordance with a pulling direction of a test piece without using a zoom lens attached to the scanning device. Accordingly, the present invention provides a tensile test apparatus capable of detecting and measuring the elongation of a test specimen with high accuracy from a small deformation to a large deformation.

[0009]

In order to achieve the above object, according to the present invention, a scanning device includes a measurement mark provided on the upper side in the tension direction of the test piece and a measurement mark provided on the lower side in the tension direction. Scanning, constituted by a plurality of scanning devices movable in the tensile direction of the test piece, of the plurality of scanning devices, a driving device of a scanning device that scans at least a measurement mark attached to the lower side in the tensile direction, The scanning device is moved in accordance with the movement of the chuck in the pulling direction in conjunction with the driving device in the pulling direction of the chuck for gripping both ends of the test piece, and the measurement mark of the test piece is moved to the reference line of the position reference plate. The point is that the elongation is detected based on the relationship with

[0010] Further, a plurality of scanning devices movable in the tensile direction of the test piece for scanning a measurement mark provided on the upper side in the tensile direction of the test piece and a measurement mark provided on the lower side in the tensile direction of the test piece. , And each of the measurement marks can be scanned, and the movement of the scanning device is counted by the number of rotation pulses of the moving shaft to detect elongation. Further, the plurality of scanning devices is to employ television cameras, one of the record over <br/> Heather scanner camera.

[0011]

According to the present invention, a test piece having a measurement mark of a color having a different optical property from the ground color is used as a test piece, and a test piece is provided near the test piece. A standard brightness plate having the same brightness as the measured mark and a standard dark plate having the same darkness as the ground color of the test piece are provided to facilitate determination of the measurement mark.

[0012] Both ends of the test piece are gripped by chucks, and one of the chucks is moved by a guide member such as a screw rod and a driving device such as a motor to apply a tensile load to the test piece while pulling the test mark. Based on a tensile test device that scans the change in direction with a scanning device, and that measures the tensile characteristics of the test piece with an electrical signal output from the difference in optical characteristics between the measurement mark and the ground color. Is what you do.

In such a tensile test apparatus, the T
At least a plurality of scanning devices such as V-cameras are provided side by side, one of which scans the measurement mark attached to the upper side in the tension direction of the test piece, and the other scanning device is attached to the lower side in the tension direction. It is constituted by a so-called local area scanning device which scans the measured measurement mark. The local area scanning device is a scanning device that individually has a field of view near each measurement mark of a test piece, and a local area scanning device that has a full field of view near each measurement mark in a low extension area. Due to the resolution, it is possible to measure minute elongation changes of the material with high accuracy.

At the same time, a large extension change causes at least one of the local area scanning devices to move following the movement in the tensile direction for chucking both ends of the test piece, so that the resolution of the present scanning device in a low extension region is increased. High-precision measurement is possible up to the extension range. As the scanning device used in the present invention,
Known used in industrial and broadcast such as a TV camera (image pickup tube), some had the like laser scanner camera (camera light source side in combination laser scanner and receiver to line scan) are used.

[0015] In the scanning apparatus, in the case of TV cameras, the number of effective scanning lines is using 512 or 1024 of the camera, in the case of or laser scanner camera, the vibration rate of 1 / 15,000 sec / Use as a scanning camera. Further, in order to make the scanning device having the entire field of view of the low-extension region capable of performing the enlarged scanning, a zoom lens may be attached to the camera.

On the other hand, JIS (Japanese Indust
rial Standard), a tensile test piece was used, and an example is shown in FIG. On the surface of the test piece S, two mark lines Q, Q are attached as measurement marks at two places separated in the longitudinal direction (tensile direction). This marker line Q
Of the test piece S is different from the ground color of the test piece S in optical characteristics. In particular, it is preferable to make the lightness of the mark line Q higher than that of the ground color. For example, a black color or a dark color is selected as the ground color of the test piece S, and a white color or a bright color is selected as the mark line Q. Distance L between two marked lines Q, Q
In JIS, three types of 10 mm, 20 mm, 25 mm, and 40 mm are defined, and it is defined to select from these.

FIG. 5 shows the markings applied to the test pieces.
As shown in (a), the distance L between the two marked lines Q, Q is L
The test piece S ′ provided with the marker region Q ′ in which the entire portion corresponding to the above is applied may be used. In the case of the test piece S 'of this example, the boundary lines at both edges of the marker area Q' correspond to the marked lines. The above-described scanning device scans the test piece S or S 'in the longitudinal direction while scanning the change in the distance L defined by the measurement marks such as the marked lines Q and Q and the marked area Q' to measure. I do. (A) and (b) of FIG.
FIG. 1 shows a principle of a method of measurement by this scanning device.

In order to further improve the accuracy of the measurement operation, a standard brightness plate having the same brightness as the measurement mark attached to the test piece S, and a ground color of the test piece are provided near the test piece S. A standard dark plate having the same darkness and a standard length plate may be provided. As shown in FIGS. 4A and 4B, a test piece S to which a tensile load is being applied is, for example, T
When taking an image with the V camera, the scanning line HS of the TV camera
Is made to scan in the direction perpendicular to the tensile direction of the test piece S, the output signal is as shown in FIG. 4 (b), where the portions P _O and P _O corresponding to the marked lines Q and Q are the other. It appears as a higher level signal than the part.

Therefore, of this output signal, a constant level E
Only _one or more signals are taken out by the processing circuit, and the above marked lines Q,
If only signals at time intervals corresponding to the intervals L of Q are extracted, the distance L between the reference marks can be obtained from the signals. FIGS. 5A and 5B show scanning lines HS of the scanning device.
Shows the principle of the case where the line scanning is performed so that the direction of the line becomes the same as the tensile direction of the test piece S ′. In this case, FIG.
Portion of the P ₁ corresponding to the label area Q 'appears as a high level output signal as compared with other portions as. Therefore,
As in the cases of (a) and (b) of FIG. 4, if only a signal having a certain level E ₁ or more is extracted from the output part of P ₁ by the processing circuit, the distance between both ends of the marker area Q ′ is obtained. it is as possible out to determine the L.

In the tensile test apparatus according to the present invention, at least one of the scanning devices moves following the movement in the tensile direction for chucking both ends of the test piece, so that the tensile characteristics of the test piece in a large elongation region are measured. In addition to this, it is possible to easily and accurately measure the tensile properties when the test piece in the low elongation region is in the initial minute elongation state.

Since the resolution l of the scanning device is represented by the ratio (H / A) of the scanning range H and the number A of elements, which are the entire field of view, the scanning device having the low extension region as the full field of view is as follows. Since the scanning range H is narrow and the number of elements is large, the resolution is very high. Therefore, according to the scanning device in which the low elongation region has a full field of view, the tensile characteristics of the test piece at the time of minute elongation can be measured with high accuracy, and the tensile characteristics of the test piece in the large elongation region are measured. Can do that.

The above-described scanning device having a low-elongation region as a whole field of view allows two cameras to simultaneously view two marked lines on the test piece simultaneously, and details will be described later in the embodiments of FIGS. 1 and 3. In this way, the two reference lines on the test piece are each compared with the reference line of the substrate provided separately, and these reference lines are independently viewed using two cameras. As described above, by independently viewing each mark line with one camera, it is possible to perform measurement with higher accuracy as described later.

The stretching speed in the above elongation region is generally constant from low elongation to large elongation and is generally in the range of 100 to 500 mm / min.
It is preferable that the stretching speed be in the range of 0 mm / min and the stretching speed in the stretching region beyond the low stretching region be in the range of 50 to 500 mm / min. As described above, as the boundary area when the tensile speed is switched, the elongation rate of the test piece is 10 to 10.
It is preferable to select the time when it is in the range of 500%. Further, it is preferable that the switching of the pulling speed be performed in conjunction with at least two scanning devices and automatically performed.

[0024]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a first embodiment of a tensile test apparatus according to the present invention. In FIG.
Is an upper chuck for gripping the upper end of the test piece 1b.
Is a lower chuck for gripping a lower end of the lower chuck.

In the vicinity of the test piece S, a standard brightness plate X having the same brightness as the marking line Q (measurement mark) attached to the test piece S as shown in FIG. If a standard dark plate Y having the same darkness as the ground color and a standard length plate Z are provided, it is possible to clarify the difference in optical characteristics and facilitate the measurement operation. Note that the standard length plate Z does not necessarily need to be provided. When the number and position of the TV cameras are fixed, the T length corresponding to the number of scales engraved on the standard length plate Z is set.
It is also possible to set the number of scanning lines of the V camera as a constant in a control device in advance and control the number of scanning lines.

The upper chuck 1a is installed so as to be stationary at a fixed position, and has a load cell 2 for detecting a tensile load connected to the upper end thereof. The tensile load detected by the load cell 2 is transmitted via the amplifier 12 to the central processing unit 1.
9 (CPU). On the other hand, the lower chuck 1b is connected to a gear box 3 via a guide member 3a such as a screw bar, and the gear box 3 is connected to a motor 4 (drive device). Lower chuck 1b
Moves vertically by the drive of the motor 4 via the gear box 3 and the guide member 3a, and applies a tensile load to the test piece S when moving downward. The motor 4 is connected to the central processing unit 19 via a motor control unit 13, and is driven by a command from the central processing unit 19 to change the pulling speed.

The upper chuck 1a and the lower chuck 1
The pulling mechanism b may be housed in a thermostatic bath 6 containing the cooling coil 5. In this case, two T-tubes are provided on the side of the thermostat 6 so as to face the internal tension mechanism.
V cameras 7a and 7b are installed as a scanning device, and two TV cameras 7a and 7b are provided for a test piece S so that the extension area is the entire field of view. The upper TV camera 7a looks at the upper mark line Qa (measurement mark) on the test piece S, and the lower TV camera 7b looks at the lower mark line Qb independently. Also, two TV cameras 7a,
7b is a view of the marked lines Qa, Qb facing each other.
Is formed in a narrow region H.

Among the scanning devices composed of the two TV cameras 7a and 7b, the TV camera 7b (scanning device) for scanning the measurement mark Qb attached to the lower side in the pulling direction is a base plate 11 for supporting the TV camera 7b. A guide member 8a such as a screw rod is screwed in parallel with the guide member 3a, and the guide member 8a is connected to a motor 9 (drive device) via a gear box 8. When the motor 9 is driven, the gear box 8 and the guide member 8 are driven.
The TV camera 7b is configured to be able to move in the vertical direction via a.

The motor 9 is connected to the central processing unit 19 via a motor control unit 10. The central processing unit 19 moves the driving force of the motor 4 for driving the lower chuck 1b and the TV camera 7b. The operation control is performed so that the driving force of the lower chuck 1 is equal to the driving force of the motor 9, and the calculated value is output to the motor control unit 10 of the motor 9.
The moving speed and the distance b moves downward, and the TV camera 7
The control is performed so that the moving speed and the distance at which b moves are synchronized.

Accordingly, when the lower chuck 1b grips the lower end of the test piece S and moves downward while applying a tensile load to the test piece S, the marking line Q displayed on the lower side of the test piece S is naturally obtained. Also moves downward due to the elongation of the test piece S,
Normally, the TV camera 7b moves out of the field of view of the TV camera 7b or is biased. However, in the present invention, the TV camera 7b is also moved by following the movement of the lower chuck 1b in the pulling direction.
In the center of the visual field of the camera 7b, a marked line Qb displayed on the lower side of the test piece S which is always extended is included, and the marked line Qb is compared with the number of graduations engraved on the standard length plate Z. Thus, the elongation of the test piece S can be detected.

A position reference plate 2 is located near the test piece S gripped by the upper chuck 1a and the lower chuck 1b.
0a and 20b are arranged, and the position reference plate 20a is fixed to the machine frame side so as not to move. The position reference plate 20b is fixed to the lower chuck 1b, and moves with the extension of the test piece S. The position reference plates 20a, 20
Reference marks q and q are marked on b, respectively, so as to correspond to the two marked lines Qa and Qb on the test piece S, respectively.

Although the position reference plates 20a and 20b are divided into two position reference plates 20a and 20b in this embodiment, they may be constituted by only one plate. However, in this case, the position reference plates 20a and 20b are fixed to the machine frame side, and need many reference lines. Also,
The position reference plates 20a and 20b are not necessarily provided as long as the standard length plate Z of FIG. 3 is provided.

As shown in FIG. 3, the TV cameras 7a and 7b constituting the above-mentioned local area scanning device are the former cameras 7a and 7b.
a measures the change in the distance b between the upper reference line Qa of the test piece S and the reference line q of the position reference plate 20a, and the latter camera 7b uses the lower reference line Qb and the reference line of the position reference plate 20b. The change in the distance c between q is measured. In order to determine the elongation rate of the test piece by these measurements, when the position reference plates 20a and 20b are fixed, it is performed based on the following formula. That is, when the test piece S is slightly extended, the upper mark line Qa moves by elongation of the length α, and the lower mark line Qb moves by elongation of the length β.

Assuming that the distance between the two reference lines q, q is a, the initial length L ₀ between the reference lines Qa, Qb is L ₀ = a−b−c. length L _1, since it is _{L 1 = a-b-α} -c + β, the elongation _{ε ε = (L 1 -L 0} ) / L 0 = a (β-α) / a- b-c It will be calculated by the formula. Lower position reference plate 2
When 0b moves, if the movement amount is a ', then a +
a ′ may be newly set to a.

Therefore, the marked lines Qa, Q
By reading the deformation amounts α and β between b and the reference line q, the expansion rate ε is calculated by the central processing unit 19 according to the above equation, and can be output to the printer 16.
That is, each camera TV 7a, 7b detects the distance L between the marked lines Q, Q of the test piece S, for example, as electric signals shown in FIGS. And input it to the central processing unit 19.

The output signal processed by the video circuit 14 can be monitored by the monitor display unit 15. Reference numeral 16 denotes a printer for outputting a measurement result, and 17 denotes a keyboard for inputting data necessary for the measurement. In the embodiment shown in FIG. 3, the upper mark line Qa
The reference line q with respect to the reference line q is positioned on the upper side, and the reference line q with respect to the lower standard line Qb is positioned on the lower side. However, the upper and lower relative relationship is not limited to this embodiment, and is arbitrary. May be. The moving distance of the TV camera 7b is not only compared with the position reference plate, but also the guide member 8a.
The number of rotations may be measured from the number of pulses using a rotary encoder or the like.

The TV cameras 7a and 7b in the above-described tensile tester have their entire fields of view marked with the marked lines Qa and Qb of the test piece S.
It can be set without being restricted by the distance L between them. That is, the length can be arbitrarily set to a length shorter than the minimum distance 10 mm between the marked lines Q, Q specified by JIS. Therefore, the entire field of view can be made as small as possible, so that the measurement accuracy of the TV cameras 7a and 7b can be significantly improved.

For example, it is assumed that the number of effective scanning lines of the TV cameras 7a and 7b is 400, and the entire field of view is set to 15 mm shorter than the minimum mark line distance of 20 mm using a zoom lens. At this time, the resolution l of the TV cameras 7a and 7b is l =
H / A = 15/400 = 0.0375 mm. Therefore, the measurement accuracy of the TV cameras 7a and 7b is ± 0.18% for a test piece having a distance L of 20 mm, ± 0.15% for a test piece of 25 mm, and a test piece of 40 mm. , The measurement accuracy of the TV camera becomes much higher.

FIG. 2 shows a second embodiment of the tensile test apparatus. In this embodiment, in order to further improve the measurement accuracy of the first embodiment, a reference line Qa (measurement mark) on the upper side of the test piece S is used. ), The upper TV camera 7a for scanning the lower mark line Qb and the lower TV camera 7b for scanning the lower marked line Qb are respectively moved by following the movement in the pulling direction of the lower chuck 1b.

That is, base plates 21a and 21b supporting a scanning device including two TV cameras 7a and 7b
A guide member 22a, 22b such as a screw bar is screwed into the guide member 3a in parallel with the guide member 3a.
b is connected to servomotors 24a and 24b via spur gears 23a and 23b, and further to the servomotors 24a and 24b.
4b is connected to the central processing unit 19 via servo motor amplifiers 25a and 25b.

Rotary encoders 26a and 26b are provided at the lower ends of the guide members 22a and 22b, and are configured to detect the number of rotations of the guide members 22a and 22b and output the detected rotation speed to the central processing unit 19. . This second
In the case of the embodiment, as described above, the driving force of the motor 4 for driving the lower chuck 1b and the TV cameras 7a and 7b so as to follow the movement of the lower chuck 1b in the pulling direction.
The central processing unit 19 controls the driving force of the servo motors 24a and 24b to move the upper and lower sides of the test piece S in the center of the visual field of the TV cameras 7a and 7b. Marked lines Qa and Qb displayed in
Further, by comparing the marked lines Qa and Qb with the number of graduations engraved on the standard length plate Z, the elongation of the test piece S can be accurately detected.

That is, in the second embodiment, the guide members 22a, 22b for guiding the two TV cameras 7a, 7b
The position of the terminal section is always set to the rotary encoders 26a, 26
6b, the detected value is input to the central processing unit 19, and based on the positions of the terminal portions of the guide members 22a, 22b, the central processing unit 19 outputs the servo motor amplifiers 25a, 25b.
5b is fed back to the servo motors 24a and 24b.

While controlling the rotational driving force of the servo motors 24a and 24b so as to correspond to the moving distance of the lower chuck 1b, two TV cameras are connected via the spur gears 23a and 23b and the guide members 22a and 22b. 7a, 7
b is moved to the center of the field of view of the two TV cameras 7a and 7b, and the marking lines Q displayed on the upper side and the lower side of the test piece S.
Control is performed while making small adjustments so that a and Qb always enter accurately, and measurement can be performed by comparing the marked lines Qa and Qb with the number of scales engraved on the standard length plate Z. is there.

Since other structures are the same as those of the first embodiment, the same reference numerals are given and the description is omitted. As another embodiment for controlling the two TV cameras 7a and 7b so as to follow the movement of the lower chuck 1b in the pulling direction, a video circuit for inputting images from the two TV cameras 7a and 7b 14 equipped with an image processing function,
If the marking lines Qa, Qb displayed on the upper and lower sides of the test piece S imaged by the cameras 7a, 7b are shifted or deviated from the center of the image, the marking lines Qa, Qb
The position is obtained by calculation, and the calculated value is used as the central processing unit 1
9 to calculate and feed back data corresponding to the positions of the marking lines Qa and Qb to the servo motors 24a and 24b, so that the servo motors 24a and 24b are driven to rotate so as to correspond to the moving distance of the lower chuck 1b. While controlling the force, the spur gears 23a, 23b and the guide members 22a,
It is also possible to move the two TV cameras 7a, 7b via 22b.

As described above, the tensile test apparatus according to the present invention allows the upper mark line Qa and the lower mark line Qb to be viewed by independent TV cameras 7a and 7b, respectively, and the lower chuck 1b. The movement of the TV camera 7a or 7b is controlled so as to follow the movement in the pulling direction.
Even if the minimum distance between marking lines specified by JIS is 20 mm, it is possible to reduce the entire field of view beyond this dimension and measure. Can be measured.

[0046]

According to the present invention, as described above, the scanning device comprises:
A measurement mark attached to the upper side in the tensile direction of the test piece,
Scanning the measurement mark attached to the lower side in the pulling direction, comprising a plurality of scanning devices movable in the pulling direction of the test piece, of the plurality of scanning devices, at least the measurement attached to the lower side in the pulling direction The driving device of the scanning device that scans the mark is interlocked with the driving device in the pulling direction of the chuck that grips both ends of the test piece, and the scanning device is moved following the movement of the chuck in the pulling direction. The scanning device is tested without using a zoom lens attached to the scanning device because the extension is detected by measuring the measurement mark of one piece with the reference line of the position reference plate or measuring the rotation pulse counter of the rotary encoder. By moving the test piece in the tensile direction, the elongation of the test piece can be detected and measured with high accuracy from a small deformation to a large deformation.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a tensile test apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic view showing a tensile test apparatus according to a second embodiment of the present invention.

FIG. 3 is an enlarged front view showing a test piece mounted on the apparatus of FIG. 1;

FIGS. 4A and 4B are explanatory diagrams showing the principle of a tensile test device using a scanning device, respectively.

5 (a) and (b) is an explanatory view showing another example of the principles of the tensile testing apparatus using each Re its Re scanning device.

[Explanation of symbols]

1a Upper chuck 1b Lower chuck 2 Load cell 3 Gear box 3a Guide member 4 Motor 6 Constant temperature bath 7a, 7b TV camera (scanning device) 8 Gear box 8a Guide member 9 Motor 19 Central processing unit 20a, 20b Position reference plate S Test piece Qa , Qb Measurement mark (marked line) q Reference line

Continuation of front page (56) References JP-A-1-250006 (JP, A) JP-A-3-226613 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 3 / 00-3/62 G01L 1/00 JICST file (JOIS)

Claims (7)

(57) [Claims] 1. A test piece provided with at least one measurement mark of a color different in ground color and optical properties is gripped at both ends by chucks, and one chuck is moved via a guide member and a driving device, While applying a tensile load to the test piece, a change in the tensile direction of the measurement mark is scanned by at least one scanning device, and the test piece is obtained by an electrical signal output due to a difference in optical characteristics between the measurement mark and the ground color. In a tensile test apparatus that is configured to measure the tensile properties, the scanning device scans the measurement mark attached to the upper side in the tensile direction of the test piece, and the measurement mark attached to the lower side in the tensile direction, Consisting of a plurality of scanning devices that can move in the tensile direction of the test piece, of the plurality of scanning devices,
The driving device of the scanning device that scans at least the measurement mark attached to the lower side in the pulling direction is linked with the driving device in the pulling direction of the chuck that grips both ends of the test piece, and follows the movement of the chuck in the pulling direction. A tensile tester, wherein a scanning device is moved to detect elongation based on a relationship between a measurement mark of the test piece and a reference line of a position reference plate. 2. A plurality of scanning devices movable in a tensile direction of a test piece for scanning a measurement mark attached to a lower side in a tension direction of a test piece and a measurement mark attached to a lower side in a tension direction of the test piece, The tensile test apparatus according to claim 1, wherein each measurement mark is scanned independently. 3. The tensile test apparatus according to claim 1, wherein the elongation is detected by counting the movement of the scanning device by the number of rotation pulses of the moving shaft. Wherein said plurality of scanning devices, a tensile test apparatus according to the television Ca <br/> ra, claim 1 is any one of record over Heather scanner camera. 5. The tensile test apparatus according to claim 1, wherein a standard length plate is provided instead of the position reference plate. 6. The tensile test apparatus according to claim 1, wherein a scanning device that scans the measurement mark on the upper side is fixed. 7. The pulling device according to claim 1, wherein both the scanning device for scanning the upper-side measurement mark and the scanning device for scanning the lower-side measurement mark are moved in conjunction with a driving device for driving the chuck in the pulling direction. Testing equipment.