JPH0781939B2 - Rubber-like sample tensile tester - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a tensile test device for measuring the tensile properties of a rubber-like sample using a scanning device such as a television camera and a line sensor camera.

[Prior art]

Eliminates the complexity and error when measuring the tensile change of a test piece with the naked eye in a tensile tester that measures tensile properties such as elastic modulus, elongation stress, and elongation at break of rubber-like samples such as rubber, resin, and fiber. Therefore, it is already known from the present inventor that the test mark is provided with measurement marks having different optical characteristics and the measurement mark is automatically measured by using a scanning device such as a television camera (hereinafter, simply referred to as a TV camera). The proposal was made in Japanese Patent Publication No. 56-19882, Japanese Patent Publication No. 56-18086, etc.

On the other hand, for samples that undergo large deformation 5 to 10 times before breaking, such as rubber, it is necessary to investigate not only the characteristics of elongation at the time of large deformation but also the characteristics of minute deformation in the small deformation region. There is a case. However, in each of the above-mentioned conventional tensile testing devices, one TV camera measures the elongation of one or more test pieces. Therefore, if the TV camera is brought close to the test piece, it is possible to read even a small amount of extension, but it becomes impossible to measure a large amount of extension because it is out of the field of view of the TV camera. On the other hand, if the TV camera is moved away from the test piece, the elongation of large deformation can be detected, but this has a problem that the accuracy of reading the minute elongation is lowered. Such a problem also occurs when a line sensor camera is used as the scanning device.

[Object of the Invention]

An object of the present invention is to provide a tensile test device for a rubber-like sample that can measure a minute elongation of a rubber-like sample having a large amount of tensile deformation with high accuracy and can simultaneously measure a large elongation in one test. To do.

[Structure of Invention]

The present invention to achieve the above object, a rubber-like test piece provided with a measurement mark having different ground color and optical characteristics, while deforming by applying a tensile load in the longitudinal direction, the deformation of the measurement mark is scanned by a scanning device. In the device for measuring the tensile property of the test piece from the electric signal output depending on the difference in optical property, the scanning device is composed of either a non-contact type television camera or a line sensor camera, and as the scanning device, At least two scanners, a scanning device having a large deformation area of the test piece as the entire visual field and a scanning device having a small deformation area of the test piece as the entire visual field and having a zoom lens attached to improve the measurement accuracy, are provided side by side. It is characterized in that at least two scanning devices can be switched.

Further, in the present invention, in order to enable high-precision reading, it is preferable to configure the pulling speed when pulling the test piece to be variable, and pulling at a low speed in the small deformation region,
In a large deformation region that exceeds a preset elongation rate, it is preferable to pull at a normal speed higher than this. The low speed region at this time is in the range of 0.5 to 50 mm / min, although it depends on the type of test piece, and the normal speed is preferably in the range of 50 to 500 mm / min. In addition, it is preferable to set the extension rate in the range of 1.0 to 50.0% as a boundary region when switching such a pulling speed.

Such a pulling speed should be linked to the operation of at least two scanning devices, the scanning device that operates the small deformation region as the entire field of view at low speed, and the large deformation region as the entire field of view at the normal speed. It is preferred to activate the scanning device and to switch it automatically.

There are two types of scanning devices, one that makes a small deformation area of a piece of paper the entire field of view and another that makes a large deformation area of the test piece the entire field of view.
It is sufficient to have a table, but if necessary, three or more can be used. This scanning device can be a non-contact type consisting of a known TV camera or line sensor camera used for industrial or broadcasting, and a camera with a small deformation area as the entire field of view. A scanning device with a zoom lens attached to improve the measurement accuracy has been used for the. Such a camera includes, for example, a commercially available CCD camera TJ-22 with an effective pixel count of 378 × 485.
AII type (NEC) etc. can be effectively used.

A tensile test piece as specified in JIS is used for the test piece of the rubber-like sample. An example thereof is illustrated in FIG. 2A. On the surface of the test piece S, marked lines Q, Q are attached as measurement marks at two positions separated in the longitudinal direction (pulling direction). The test piece S is made such that the ground color and the color of the marked line Q have different optical characteristics, and it is particularly preferable that the lightness of the marked line Q is higher than that of the ground color. For example, choose a black or dark color as the ground color of the test piece S,
It is advisable to choose a white or bright color.

FIGS. 2A and 2B are principle diagrams for explaining a method of measuring the tensile characteristics by a scanning device while pulling such a test piece S in the longitudinal direction.

As shown in the drawing, when the test piece S is imaged by, for example, a TV camera while being stretched by applying a tensile load to the test piece S,
When the direction of the scanning line HS is orthogonal to the tensile direction of the test piece S as shown in FIG. 2A, the output signal is a portion P _o corresponding to the marked lines Q, Q as shown in FIG. 2B. , P _o appears at a higher level than other parts. Therefore, of the output signals of this TV camera, only the signals of a constant level E ₁ or higher are taken out by the processing circuit, and only the signals of the time intervals corresponding to the interval L between the marked lines Q and Q are obtained, and the marker line is obtained from the signals. The distance L may be calculated.

The present invention will be described below with reference to a rubber-like sample tensile test apparatus of the embodiment shown in FIG.

In FIG. 1, reference numerals 1a and 1b denote an upper chuck and a lower chuck for gripping both ends of the test piece S, respectively. The upper chuck 1a is installed at a fixed position, and a load cell 2 for detecting a tensile load is connected to the upper end side. And
The tensile load detected by the load cell 2 is input to the central processing unit 9 via the amplifier 12. on the other hand,
The lower chuck 1b is vertically moved by driving a motor 4 via a gear box 3 to apply a tensile load to the test piece S. This motor 4 has a motor controller 13
It is driven by a command from the central processing unit 9 via the.

The pulling mechanism including the upper and lower chucks 1a and 1b has a cooling coil 5
It is stored in a constant temperature bath 6 having. Further, a double glass see-through portion 7 is provided on the side surface of the constant temperature bath 6 so that it can be seen from the outside. Dry hot air is passed through the space portion 8 of the see-through portion 7 so that cloudiness due to condensation does not occur on the glass surface. The constant temperature bath 6 is attached to measure the characteristics of the sample at low temperature, and is not necessarily required to measure the characteristics under normal temperature conditions.

Two TV cameras 10 and 11 are installed outside the see-through part 7 so as to face the inner pulling mechanism. Each camera processes an electric signal detected as shown in FIGS. 2A and 2B by the video circuit 14 and inputs it to the central processing unit 9. The output signal processed by the video circuit 14 can be monitored by the monitor TV15.

One of the two cameras, the TV camera 10 is equipped with a zoom lens, and its entire field of view is limited to the small deformation region in the initial stage of tension and enlarged scanning is performed, so that the low elongation region of the test piece S is mainly detected. It has become. Since the entire visual field is limited to the small deformation area in this way, even minute deformations can be read with high accuracy.

For example, the CCD camera TJ-22 described above as this TV camera 10.
It is assumed that the AII type is used, its entire field of view is limited by a zoom lens to a small deformation area of, for example, 25 mm, and the number of effective pixels in the vertical number of pixels is 450. Further, it is assumed that a normal tensile test piece according to JIS No. 3 is used as the test piece S, and this test piece is pulled to add 25% of extension to a distance of 20 mm between the initial marked lines Q and 25 up to the upper total visual field limit of 25 mm. Then, the displacement that can be read by this TV camera is 25mm / 450
Extremely high precision of up to 0.05 mm / piece.

The other TV camera 11 of the two cameras is not equipped with a zoom lens, and its entire field of view faces the entire tensile deformation region until the test piece S breaks. The large deformation area of is detected.

The above-mentioned two TV cameras 10 and 11 are the former TV camera 10 in the small deformation area at the start of the tensile test according to the instruction of the central processing unit 9.
Scans, but when the test piece S exceeds the preset expansion rate and extends to the large deformation area, the operation of the camera is switched and the latter TV camera 11 scans. The central processing unit 9 also controls the motor control unit 13 to change the pulling speed of the lower chuck 1b. Then, the speed is set low in the small deformation area, but in the large deformation area that exceeds a preset expansion rate, the speed is switched to a normal speed higher than this.

The result of the tensile property of the test piece measured by such an operation is output from the central processing unit 9 to the printer 16.
Reference numeral 17 is a keyboard for inputting data required for measurement.

As described above, the tensile tester has at least two TV cameras installed side by side, one of which is a high-precision extensometer exclusively for the small deformation area, and the other one is a normal extensometer. Automatically when S reaches the preset expansion rate
The TV camera is switched from a high-precision extensometer to a normal extensometer. Therefore, it becomes possible to accurately read the elongation rate from the start of pulling to cutting of the test piece, and especially the elongation rate (0.2 to 20%) in the small deformation region can be read to an accuracy of ± 0.2%. .

When the tensile speed is also switched at a preset elongation rate as in the above example, the low elongation modulus is measured in the low speed small deformation area, and then the high elongation modulus is measured in the normal speed large deformation area. You can Therefore, it becomes possible to simultaneously measure a plurality of tensile properties in one test.

〔The invention's effect〕

As described above, the tensile test device of the rubber-like sample of the present invention,
An electrical tester that scans the deformation of the measurement mark with a scanning device while deforming a rubber-like test piece with a measurement mark having different ground color and optical characteristics by applying a tensile load in the longitudinal direction, and outputs it according to the difference in optical characteristics. In a device for measuring the tensile properties of the test piece from a signal, the scanning device is composed of either a non-contact type television camera or a line sensor camera, and the large deformation area of the test piece is used as the scanning device. At least two scanning devices, one with the field of view and the other with a small deformation area of the test piece as the total field of view, and with a zoom lens attached to improve the measurement accuracy, can be switched between the at least two scanning devices. Since it is configured as described above, it has the following excellent effects.

That is, as the scanning device, at least two scanning devices having a large deformation area of the test piece as the entire field of view and a scanning device having the small deformation area of the test piece as the entire field of view are arranged side by side to perform switching operation. Since the scanning device for small deformation area can trace a minute extension deformation and the scanning device for large deformation area can reliably trace a large extension deformation, it is possible to perform a single test from a minute extension to a large extension. It is possible to measure simultaneously, and as a result, it is possible to efficiently and easily measure a plurality of tensile properties at respective elongations, which is extremely useful particularly in the analysis of rubber properties having completely different viscoelastic behaviors.

In addition, since the scanning device with a zoom lens attached to the scanning device that has a small deformation area as the entire field of view to improve measurement accuracy
It is possible to accurately measure even elongation deformation of a minute rubber-like sample, and to obtain more reliable tensile properties.

Also, since the scanning device is composed of either a non-contact type television camera or a line sensor camera, it is possible to measure minute extension deformation of the test piece with high accuracy by increasing the number of pixels or scanning lines of the camera. In addition, it is possible to easily track the expansion change of the test piece that expands at high speed, and since the position of the scanning device can be fixed and used, the device is simpler and cheaper than the method of moving the scanning device. can do.

In addition, since the measurement is performed in a non-contact manner, it is possible to put the test piece in a constant temperature bath and measure it under various boundaries from high temperature to low temperature, for example from tropical to polar in the development of automobile tires. It is extremely effective in simulating the above environment, and the work of attaching and detaching the test piece for each measurement can be easily performed without being disturbed by the scanning device.

In addition to the above configuration, the tensile speed of the test piece is variable, and the at least 2
By configuring the scanning devices of the table to be switchable, it becomes possible to perform the measurement and analysis of the rubber showing the viscoelastic behavior of the rubber in each region with high efficiency due to the difference in the extension speed. By satisfying the requirements, it is possible to measure a substance test of a rubber having viscoelastically complex and delicate properties with high efficiency and little variation.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a rubber-like sample tensile test device according to an embodiment of the present invention, and FIGS. 2A and 2B are principle explanatory diagrams of a rubber-like sample tensile test device using an operating device. 1a …… Upper chuck, 1b …… Lower chuck, 9 …… Central processing unit, 10 …… (with zoom lens) TV camera, 11 ……
TV camera (scanning device), 14 ... video circuit, S ... test piece, Q ... marked line (measurement mark).

Claims (2)

[Claims] 1. A rubber-shaped test piece provided with a measurement mark having different ground color and optical characteristics is deformed by applying a tensile load in the longitudinal direction, and the deformation of the measurement mark is scanned by a scanning device,
In the device for measuring the tensile properties of the test piece from the electrical signal output depending on the difference in optical properties, the scanning device is constituted by either a non-contact type television camera or a line sensor camera, and the scanning device is At least two scanning devices, one having a large deformation area of the test piece as the entire visual field and the other having a small deformation area of the test piece as the entire visual field and having a zoom lens attached to improve the measurement accuracy, are provided side by side. A tensile test device for a rubber-like sample, characterized in that two scanning devices can be switched. 2. A rubber-shaped test piece provided with a measurement mark having different ground color and optical characteristics is deformed by applying a tensile load in the longitudinal direction, and the deformation of the measurement mark is scanned by a scanning device,
In the device for measuring the tensile properties of the test piece from the electrical signal output depending on the difference in optical properties, the scanning device is constituted by either a non-contact type television camera or a line sensor camera, and the scanning device is At least two scanners, a scanning device having a large deformation area of the test piece as the entire visual field and a scanning device having a small deformation area of the test piece as the entire visual field and having a zoom lens attached to improve the measurement accuracy, are provided side by side. Configured so that the pulling speed of one piece can be changed,
A tensile test device for a rubber-like sample, characterized in that the at least two scanning devices can be switched in conjunction with the pulling speed.