JP6758062B2 - Specimen stretch tracking device and tensile test device - Google Patents

Description

The present invention relates to a test piece elongation tracking device and a tensile test device.

A tensile test device is used to obtain the elongation characteristics (characteristics that are related to the load and the elongation amount) of a test piece such as a synthetic resin. In a tensile test, the test piece is usually pulled at a constant speed (while pulling so that the amount of elongation per unit time is constant), and a predetermined interval determined by a standard or the like is provided in the longitudinal direction. This is done by measuring the displacement of two specific positions on the test piece. That is, the amount of elongation of the test piece under a certain load can be known by observing the difference in the amount of displacement at the two specific locations.

Since the above two specific points on the test piece change from time to time according to the progress of tension, it is necessary to track these specific points. Patent Document 1 discloses a test piece using a laser beam for tracking a specific portion. That is, a set body of a laser emitting device and a camera that are integrally moved with each other is provided, the laser light from the laser emitting device is irradiated toward a specific portion of the test piece, and the light reflected from this specific portion (specs). The pattern is imaged by a camera. Then, the speckle pattern of the image obtained by the camera is made to follow, and the set body is moved. That is, by tracking the speckle pattern, it is possible to know the displacement of a specific part of the test piece.

Japanese Unexamined Patent Publication No. 2001-201320

As described in Patent Document 1, tracking of a specific portion of a test piece using a laser beam is required to have the brightness of an image acquired by a camera within a predetermined range. That is, if the brightness is too low, the image becomes dark as a whole, and it becomes impossible to recognize the speckle pattern. On the other hand, if the brightness is too high, the image becomes whitish as a whole (halation occurs), and it becomes impossible to recognize the speckle pattern.

Therefore, it is also considered to adjust the shutter speed or gain of the camera according to the brightness of the image. However, in adjusting the shutter speed, there is a problem that the responsiveness may deteriorate and a measurement delay occurs. Further, in the adjustment by changing the gain, the brightness changes too much by changing the gain in one step (occurrence of overshoot), and the problem that the speckle pattern cannot be recognized tends to occur.

The present invention has been made in consideration of the above circumstances, and the first object thereof is to change the brightness of an image acquired by a camera when tracking a specific part of a test piece by using a laser beam. It is an object of the present invention to provide a test piece elongation tracking device capable of performing the above-mentioned responsiveness and finely adjusting the brightness thereof. A second object of the present invention is to provide a tensile test device having an elongation tracking device for the test piece.

In order to achieve the first object, the following solution method is adopted in the present invention. That is, as described in claim 1,
It has a set body of a laser light emitting device and a digital camera, and the laser light from the laser light emitting device is reflected by a test piece that receives a tensile force to enter the digital camera, so that the image is captured by the digital camera. An extension tracking device for a test piece that drives the set body so as to follow the speckle pattern of the image.
A luminance detecting means for detecting the luminance of an image acquired by the digital camera, and
An output adjusting means for adjusting the output of the laser emitting device and
A preset lower limit brightness and an upper limit brightness higher than the lower limit brightness by a predetermined amount are set, and the brightness is controlled by controlling the output adjusting means when the set body follows the speckle pattern. The output of the laser light emitting device is increased when the brightness detected by the detection means is equal to or lower than the lower limit brightness, while the laser light emission is performed when the brightness detected by the brightness detection means is equal to or higher than the upper limit brightness. Output control means to reduce the output of the device and
It is designed to be equipped with.

According to the above-mentioned solution method, since the brightness of the image acquired by the camera is adjusted by adjusting the output of the laser light emitting device, the brightness adjustment can be performed responsively and finely. As a result, it becomes possible to measure the elongation characteristics of the test piece while preventing the occurrence of measurement delay and overshoot. Further, since the adjustment range of the image brightness by adjusting the output of the laser beam is large and the brightness can be finely adjusted, it is possible to correspond to the colors of various test pieces.
Further, the lower limit brightness and the upper limit brightness which is higher than the lower limit brightness by a predetermined amount are set in advance, and when the brightness detected by the brightness detection means becomes equal to or less than the lower limit brightness, the output of the laser light emitting device is output. On the other hand, the output of the laser light emitting device is reduced when the upper limit brightness is exceeded. Therefore, the brightness of the image is set in a desired range by using two thresholds, the lower limit brightness and the upper limit brightness. be able to.

A preferred embodiment based on the above-mentioned solution method is as described in claims 2 to 6 . That is,
The output adjusting means is supposed to adjust the driving voltage supplied to the laser emitting device (corresponding to claim 2). In this case, the output of the laser light emitting device can be adjusted by a simple method of voltage adjustment.

The brightness detecting means detects the total value of the brightness of all the pixels of the digital camera (corresponding to claim 3). In this case, the brightness of the image can be detected with extremely high accuracy.

The brightness detecting means detects the total value of the brightness of a specific part of the pixels of the digital camera.
(Corresponding to claim 4). In this case, it is preferable in reducing the burden on the control system for detecting the brightness of the image.

When the minimum brightness in the allowable brightness range required for following the set is β1 and the maximum brightness is β2 (β1 <β2), the lower limit brightness α1 is higher than the minimum brightness β1 (β1 <α1). ), And the upper limit brightness α2 is lower than the maximum brightness β2 (α2 <β2) (corresponding to claim 5 ). In this case, it is preferable to surely prevent the situation where the brightness of the image deviates from the permissible range.

When the actual brightness detected by the brightness detecting means is smaller than the lower limit brightness, the output control means increases the output of the laser light emitting device as the deviation between the actual brightness and the lower limit brightness increases. On the other hand, when the actual brightness detected by the brightness detecting means is larger than the upper limit brightness, the larger the deviation between the actual brightness and the upper limit brightness, the larger the output reduction of the laser light emitting device. , (Corresponding to claim 6 ). In this case, it is preferable to quickly converge the brightness of the image within the range between the lower limit brightness and the upper limit brightness.

In order to achieve the second object, the following solution method is adopted in the present invention. That is, as described in claim 7 .
The test piece elongation tracking device according to any one of claims 1 to 6 is provided. According to the above-mentioned solution method, a test piece tensile test device including the test piece elongation tracking device according to any one of claims 1 to 6 is provided.

According to the present invention, since the brightness of the image acquired by the camera can be responsively and finely adjusted, the speckle pattern can always be recognized appropriately, and the speckle pattern is followed by the laser emitting device and the camera. It is preferable for moving the set body of.

The main part perspective view which shows the part which tracks two specific parts of a test piece by a laser light emitting device and a camera. The figure which shows the example of the control system of this invention. The figure which shows the relationship between the permissible level of the brightness of a speckle pattern, and the increase / decrease of a laser output to make it a permissible level.

In FIG. 1, 1 is a test piece extending in the vertical direction. The test piece 1 is, for example, a synthetic resin plate or a metal plate, and is formed in a predetermined standard shape for a tensile test. Among the test pieces 1, for example, the lower part is sandwiched by the lower sandwiching device 2 having a fixed lower portion, and the upper portion is sandwiched by the upper sandwiching portion (not shown). In this state, the test piece 1 is pulled by moving the upper holding portion upward at a constant speed. Contrary to the case shown in the drawing, the upper part of the test piece 1 may be fixed and the lower part of the test piece 1 may be pulled downward. Since the mechanism itself for pulling the test piece 1 is well known from the past, detailed description thereof will be omitted.

A pair of upper and lower set bodies S1 and S2 are arranged on the side of the test piece 1. The set bodies S1 and S2 are a laser light emitting device 10 and a camera 11 (in the embodiment, a C-MOS camera as a digital camera is used, but a CCD camera may be used), and both 10 It is composed of a fixing member 12 that integrates the and 11. The fixing member 12 has a tubular female screw portion 12a.

Focusing on the set body S1, the tubular female screw portion 12a provided on the fixing member 12 is screwed into the screw rod 21 extending in the vertical direction. The screw rod 21 is held by a support frame (not shown) so that it can rotate and cannot be displaced in the vertical direction. As a result, the female screw portion 12a, that is, the set body S1 is moved in the vertical direction as a whole by rotating the screw rod 21 in the forward and reverse directions.

The set body S2 is also moved in the vertical direction by using the screw rod 22 (corresponding to 21) as in the set body S1.

In the set body S1 located above, the laser light emitting device 10 irradiates a specific upper portion of the test piece 1 with a laser beam. Then, the camera 11 receives the laser beam reflected at a specific location on the upper part of the test piece 1.

In the set body S2 located below, the laser light emitting device 10 irradiates the lower specific portion of the test piece 1 with the laser beam. Then, the camera 11 receives the laser beam reflected at a specific location below the test piece 1.

The distance between the upper specific portion and the lower specific portion described above is, for example, 50 mm. Further, the irradiation range of the laser beam irradiated to each specific portion of the upper part and the lower part is, for example, about 5 mm in width and 2 mm in length. The imaging range of the camera 11 includes the irradiation range of the laser beam on the test piece 1 and is set to be a range sufficiently larger than this irradiation range.

Next, an example of a control system for tracking the specific location will be described with reference to FIG. 2, but FIG. 2 focuses on the set body S1. In FIG. 2, 31 is a motor for driving the screw rod 21, and 32 is a sensor for detecting the rotation position of the motor 31 (displacement position of the set body S1). The sensor 32 can also directly detect the amount of rotation of the screw rod 21.

Reference numeral 33 denotes a power source, and the voltage from the power source 33 is adjusted by the voltage adjusting unit 34 and then supplied to the laser light emitting device 10. That is, the voltage adjusting unit 34 is the output adjusting unit of the laser light emitting device 10.

Reference numeral 35 denotes an image processing unit, which identifies the speckle pattern from the image captured by the camera 11 and detects the brightness thereof. As is known, the speckle pattern is a pattern in which a large number of bright dots appear on a black background, and a pattern having an aggregate of a large number of bright dots is drawn. If the brightness of the speckle pattern is too high or too low, it becomes impossible to recognize the pattern by the speckle pattern.

When the test piece 1 is stretched, the speckle pattern (pattern) changes upward in the embodiment, so that the set body S1 is moved upward in accordance with the change in the speckle pattern. Therefore, when the image processing unit 35 detects the amount of movement of the speckle pattern upward, the detection result is output to the drive control unit 36, and the drive control unit 36 drives and controls the motor 31 to constantly image. It is assumed that the speckle pattern is detected by the processing unit 35.

On the other hand, the brightness of the speckle pattern obtained by the image processing unit 35 is output to the output control unit 37. The output control unit 37 controls the voltage adjustment unit 34 so that the brightness (actual brightness) output from the image processing unit 35 is within a predetermined range. The point of output adjustment (luminance adjustment) will be described later.

FIG. 3 schematically shows a method of output adjustment by the output control unit 37. In FIG. 3, ideal ranges of α1 and α2 (α1 <α2) are set as the brightness required for the set body S1 to follow the speckle pattern as the tension of the test piece 1 progresses. The low (small) brightness α1 is the lower limit brightness, and the high (large) brightness α2 is the upper limit brightness.

The minimum brightness β1 whose brightness is lower than the lower limit brightness α1 by a predetermined amount indicates a brightness at which it is difficult to sufficiently recognize the speckle pattern at a brightness lower than this. Further, the brightness β2, which is a predetermined amount higher than the upper limit brightness α2, indicates a brightness at which it is difficult to sufficiently recognize the speckle pattern at a brightness higher than this. That is, the brightness in the range between β1 and β2 is defined as the allowable brightness range (allowable level) required for tracking using the speckle pattern.

The output control unit 37 controls the output adjustment unit 34 so that the actual brightness does not become lower than β1 and not higher than β2. Specifically, when the actual brightness becomes lower than the lower limit brightness α1, the supply voltage to the laser light emitting device 10 is increased (increased). Further, when the actual brightness becomes larger than the upper limit brightness α2, the supply voltage to the laser light emitting device 10 is lowered (decreased). In this way, the actual luminance is controlled so as to be within the allowable level range of at least the minimum luminance β1 and the maximum luminance β2.

In the above-mentioned luminance adjustment, when the actual luminance is smaller than the lower limit luminance α1, it is preferable that the larger the deviation between the actual luminance and the lower limit luminance α1, the larger the output increase. Similarly, when the actual brightness is larger than the upper limit brightness α2, it is preferable that the larger the deviation between the actual brightness and the upper limit brightness α2, the larger the output reduction amount.

Since the speckle pattern brightness adjustment by adjusting the output of the laser light emitting device 10 is extremely responsive, it is possible to reliably prevent the speckle pattern brightness from being out of the permissible level range. Further, since the brightness adjustment range by the output adjustment can be finely adjusted, the problem of overshoot does not occur. In addition to the above, the required brightness of the image may differ greatly depending on the difference in color of the test piece 1, but the brightness can be adjusted in response to the difference in various colors of the test piece 1. , The test can be performed without considering the color of the test piece 1.

In the set body S2, the same control system as in FIG. 2 is configured, and the control is independent of the set body S1 (independently from the set body S1, the speckle pattern brightness control and the drive following the control body S1). control).

Here, the tensile property of the test piece 1 is determined by the tensile property determining unit 38. That is, while the load at a certain time point is input from the tensioning device side, the amount of movement from the sensor 32 in each set body S1 and S2 at that time is input. As a result, the tensile property determining unit 38 calculates the elongation amount, which is the difference between the movement amounts detected by each sensor 32, and obtains the relationship of the elongation amount with respect to the load. Such tensile properties are acquired at time and time as the test piece 1 is stretched and stored in a storage means, and after the tensile test is completed, the relationship of the elongation amount for each load is collectively acquired (output). It is possible to do.

Here, the brightness determined by the image processing unit 35 is, in the embodiment, the total value of the brightness for all the pixels. By individually observing the brightness of all the pixels of the image captured by the camera 11, it is possible to determine whether or not the speckle pattern can be recognized with extremely high accuracy. When determining the brightness in the image processing unit 35, the total value of the brightness for the pixels in a part of the specific region can be used instead of determining the brightness for all the pixels. For example, at least the total value of the brightness of the central region of the image and the peripheral regions of the four corners of the image, or the total value of two sets of narrow specific regions set on the two diagonal lines of the image. It can be appropriately selected as including the central region and the peripheral region.

Although the embodiments have been described above, the present invention is not limited to the embodiments, and appropriate modifications can be made within the scope of the claims. Of course, an object of the present invention is not limited to what is specified, but also implicitly includes providing what is expressed as substantially preferable or advantageous.

According to the present invention, it is possible to appropriately track the elongation of a test piece using a laser beam.

S1, S2: Set body α1: Lower limit brightness α2: Upper limit brightness β1: Minimum brightness β2: Maximum brightness 1: Test piece 2: Lower holding part 10: Laser light emitting device 11: Camera 12: Fixing member 12a: Female threaded parts 21, 22 : Screw rod 31: Motor (for driving the set body)
32: Sensor (for measuring displacement)
33: Power supply 34: Voltage adjustment unit (output adjustment unit)
35: Image processing unit 36: Drive control unit 37: Output control unit 38: Tensile characteristic determination unit

Claims (7)

It has a set body of a laser light emitting device and a digital camera, and the laser light from the laser light emitting device is reflected by a test piece that receives a tensile force to enter the digital camera, so that the image is captured by the digital camera. An extension tracking device for a test piece that drives the set body so as to follow the speckle pattern of the image.
A luminance detecting means for detecting the luminance of an image acquired by the digital camera, and
An output adjusting means for adjusting the output of the laser emitting device and
A preset lower limit brightness and an upper limit brightness higher than the lower limit brightness by a predetermined amount are set, and the brightness is controlled by controlling the output adjusting means when the set body follows the speckle pattern. The output of the laser light emitting device is increased when the brightness detected by the detection means is equal to or lower than the lower limit brightness, while the laser light emission is performed when the brightness detected by the brightness detection means is equal to or higher than the upper limit brightness. Output control means to reduce the output of the device and
A test piece elongation tracking device characterized by being equipped with. In claim 1,
An extension tracking device for a test piece, wherein the output adjusting means adjusts a driving voltage supplied to the laser emitting device. In claim 1 or 2,
A test piece elongation tracking device, wherein the luminance detecting means detects the total luminance of all the pixels of the digital camera. In claim 1 or 2,
A test piece elongation tracking device, wherein the luminance detecting means detects the total luminance of a specific part of the pixels of the digital camera. In claim 1,
When the minimum brightness in the allowable brightness range required for following the set is β1 and the maximum brightness is β2 (β1 <β2), the lower limit brightness α1 is higher than the minimum brightness β1 (β1 <α1). ), And the maximum brightness α2 is lower than the maximum brightness β2 (α2 <β2) . In claim 1 or 5,
When the actual brightness detected by the brightness detecting means is smaller than the lower limit brightness, the output control means increases the output of the laser light emitting device as the deviation between the actual brightness and the lower limit brightness increases. On the other hand, when the actual brightness detected by the brightness detecting means is larger than the upper limit brightness, the larger the deviation between the actual brightness and the upper limit brightness, the larger the output reduction of the laser light emitting device. , A test piece elongation tracking device. A test piece tensile test device comprising the test piece elongation tracking device according to any one of claims 1 to 6.

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