JP2000333157A - Video type elongation meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a video type elongation meter that can continuously accurately measure an elongation even when a mark marked on a test piece is moved laterally in a direction orthogonal to a tensile load direction during a test. SOLUTION: A movement in a direction orthogonal (x direction) to a tensile direction (y direction) of marks M1, M2 is detected from image data an image processing area set to video data from a video camera 1 and continuous searching of a position in the y direction is attained even when the marks M1, M2 are laterally moved by moving an image processing area on the video data in the x direction so that the marks are contained within the image processing area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of obtaining the instantaneous position information of each mark from a video signal obtained by photographing a plurality of marks attached to the surface of a sample with a video camera, and measuring the extension of the sample without contact. To a video extensometer that measures at a time.

[0002]

2. Description of the Related Art A video extensometer using a video camera is known as an extensometer for measuring the elongation of a sample during a tensile test without contact. In this video extensometer, marks M1 and M2 corresponding to, for example, two mark lines are attached to the surface of the sample W before the start of the test, as shown in FIG. A video signal obtained by photographing W with a video camera C during a test is digitized through an image capturing circuit S such as a capture board,
The data is captured as video data by a data processing device D mainly composed of a computer and is subjected to image processing.
2 to obtain the marks M1 and M
The elongation between the two is calculated.

In order to obtain the position information of the marks M1 and M2 in the pulling direction by performing image processing on the video data by the video camera C, generally, image processing is performed on all of the video data from the video camera C over a relatively wide range. Then, the processing time becomes longer and the time resolution of elongation is reduced, or a high-speed arithmetic processing device is required and the device cost is greatly increased.
M2 or a limited area including both M2
Two limited areas individually including M1 and M2 are set in advance, and image data in the image area is subjected to image processing.

An example of a specific method for obtaining position information of the marks M1 and M2 in the pulling direction by image processing is as follows. As a mark M1 and M2, a mark body m having a black linear mark on a white background is used. In the case of sticking to the sample surface, as shown in FIG. 4, in the set image processing area P, the density information of each pixel is expressed by x
Integrate in the direction. Thereby, as illustrated in the graph of FIG. 5, a black peak appears corresponding to the position of the mark M1 (and M2). The position of this peak in the y direction is
For example, the y-coordinates y _a and y _b at the two intersections of the predetermined threshold value Th and the graph are obtained as the center coordinates y _c of the y-coordinates y _a and y _b , and that y _c is the position (coordinate) of the mark M1 (M2) in the y-direction. Recognize. As described above, the elongation of the sample W is determined for each of the marks M1 and M2 during the test as described above, and the position in the y direction is determined every moment, and the distance between M1 and M2 is determined from the change from the beginning of the test.

[0005]

However, depending on the sample subjected to the tensile test, the mark may be formed during the process of elongating the sample by a tensile load due to some cause such as anisotropy of the material and mechanical properties. It may be shifted in the x direction orthogonal to the tensile direction. When such a lateral movement of the mark occurs, as shown in FIGS. 4 and 5, only the positional information of each mark in the tensile direction is detected by the conventional video extensometer, as shown in FIGS. There has been a problem that it becomes impossible to search for marks, and it is impossible to continue elongation measurement.

The present invention has been made in view of such circumstances, and it is intended to continuously and accurately measure elongation even when a mark on a sample is displaced in a direction perpendicular to a tensile direction during a tensile test. It aims to provide a video extensometer that can be used.

[0007]

In order to achieve the above object, a video extensometer according to the present invention is obtained by photographing a sample having a plurality of marks on its surface and applying a tensile load with a camera. In a video extensometer which calculates the elongation of a sample by obtaining the position information of each mark in the tensile direction (y direction) by performing image processing of the video data to be obtained in a preset image area, From the image data in the image processing area, the movement of each mark in a direction perpendicular to the pulling direction is detected, and the image processing area on the video data is orthogonal to the pulling direction so that each mark fits in the area. It is characterized by having mark lateral movement tracking means for moving in the direction.

The present invention obtains, from image data of a sample by a camera, instantaneous positional information of each mark in a tensile load direction (y direction) and instantaneous positional information in a direction orthogonal to the same (x direction). Based on the position information of each mark in the x direction, the image processing area is moved in the x direction to track each mark, thereby trying to cope with the lateral movement of each mark.

That is, since the image processing area is set to include the image of each mark at the beginning of the test,
At the beginning of the test, instantaneous positional information of each mark in the y direction and the x direction can be obtained in the image processing area. When each mark moves in the x direction as the test progresses, the image processing area is automatically shifted in the x direction following the movement, so that each mark deviates from the image processing area to measure the elongation. It can be prevented from becoming impossible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention.

A sample W having two marks M1 and M2 on its surface has both ends, for example, grippers G of a material testing machine.
By holding the lower gripping tool G1 and displacing the upper gripping tool G2 upward in the state of being gripped by 1, G2, a tensile load is applied in the vertical direction (y direction) in the figure. For each of the marks M1 and M2, for example, a mark body m (not shown in FIG. 1; see FIG. 2) composed of a label or the like having a black horizontal line as a mark on a white background is attached to the surface of the sample W. Thereby, it is attached to the sample W.

The video camera 1 has marks M1 and M2.
Are set within the field of view from the start to the end of the test. The output from the video camera 1 is captured by the data processing device 3 via an image capturing circuit 2 such as a capture board. The data processing device 3
A memory 31 for temporarily storing instantaneous video data from the video camera 1 captured via the image capturing circuit 2;
An image processing unit 32 that performs image processing on image data in two image processing areas set to include the images of the marks M1 and M2 at the beginning of the test among the video data stored in the memory 31. The elongation of the sample W is continually determined based on the position information of the marks M1 and M2 in the instantaneous tensile direction (y direction) obtained by the image processing unit 32 using the method illustrated in FIG. The calculated elongation of the sample W is displayed on the display 4 and printed on the printer 5. The initial setting of the image processing area is performed by operating, for example, the keyboard 6 or the like.

As described above, the image processing section 32 is a mark y-direction position search section 32 for obtaining instantaneous y-direction position information of each of the marks M1 and M2 from the image data in each image processing area.
In addition to a, when moving from the image data in each image processing area in the direction (x direction) orthogonal to the pulling direction of each mark, this is detected, and according to the detection result, the image of each mark M1 and M2 is detected. A mark y-direction position search unit 32a and a mark lateral movement tracking unit 32b for moving the image processing region in the x direction by the mark lateral movement tracking unit 32b so as to always fall within each image processing region are provided. In addition,
The data processing unit 3 is actually composed of a computer and its peripheral devices, and a program for performing each of the above functions. However, in FIG. 1, for simplification of description, the data processing unit 3 is shown in a block diagram for each function. I have.

The mark M by the mark lateral movement tracking unit 32b
The method of tracking 1 and M2 can be realized, for example, as follows. FIG. 2 is an explanatory diagram thereof. Assuming that both ends in the x direction of the image processing area P used up to the previous time are A1 and B1, first, one area end A is fixed, and the other area end is changed to B1 to B3. Then, in the vicinity of the mark M1 (M2), the density information of the pixel is integrated in the x direction over each range from A1 to B1, B2 and B3. As a result, a black peak as shown in FIG. 5 appears at the time of integration in each range. The black peak value that appears due to the simple integration of the pixel density information in each range indicates that B3 of the other region end portion has a part of the image of the mark M1 (M2) protruding outside the region. This is lower than B2, which indicates that B3 crosses the image of the mark M1 (M2).
Further, although there is no difference in the black peak value obtained by the simple integration of the density information for B1 and B2, the degree of black, that is, the average blackness of the pixels used for integration of the peak portion, is higher in B1. As a result, it is found that B2 extends to an unnecessary portion, and it turns out that B1 is optimal as the other region end. By performing the same processing with the other area end fixed to B1 and the one area end changed, the one area end can also be set to the optimum position.

By performing such a process each time video data from the video camera 1 is captured, even if the marks M1 and M2 are shifted in the x direction as the test proceeds, each image processing area follows the shift. Move in the x direction and mark M
Image processing by the mark y-direction position search unit 32a can be performed in a state where 1, 1 and M2 are always positioned substantially at the center in the x-direction of the image processing area.

The method of tracking the marks M1 and M2 is not limited to the above example.
When any one of the areas B3 to B3 is to be adopted, another arbitrary method such as employing the one closest to A1 among the ones in which the simple integrated value of the grayscale information of the pixel at the peak position does not change is adopted. Can be.

In the above embodiment, the mark M1
An example in which individual image processing areas are set for M2 and M2 has been described. However, for a sample or the like in which the distance between marks M1 and M2 is relatively short, an image processing area including both marks M1 and M2 can be set. In this case, when the image processing area is moved in the x direction, both marks M1,
By performing the above-described processing on M2, a method may be adopted in which an optimum area end is obtained for each of the marks M1 and M2, and an average area end is used.

[0018]

As described above, according to the present invention, of the image data from the video camera, the image processing area set to include the image of each mark marked as a mark on the surface of the sample. By image processing the image data of
In a video extensometer that calculates the elongation of the sample by obtaining the instantaneous position information of each mark in the tensile load direction, the movement of each mark in the direction perpendicular to the tensile direction is detected, and each mark is processed in the image processing area. Since the image processing area is automatically moved in the direction perpendicular to the tensile direction so that it fits within, even if each mark moves in the direction perpendicular to the tensile direction as the test progresses, accurate measurement of elongation can be performed. It has become possible to continue.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation of a mark lateral movement tracking unit 32b according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration example of a conventional video extensometer.

FIG. 4 is an explanatory diagram of an example of an image processing area set in a conventional video extensometer and a method of obtaining position information of a mark in a tensile load direction based on image data in the area.

FIG. 5 is an explanatory diagram of an example of a method of obtaining position information of a mark in a tensile load direction in a conventional video extensometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Video camera 2 Image capture circuit 3 Data processing device 31 Memory 32 Image processing unit 32a Mark y-direction position search unit 32b Mark lateral movement tracking unit 33 Elongation calculation unit 4 Display 5 Printer 6 Keyboard G1, G2 Gripping tool M1, M2 Mark W Sample

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2F065 AA03 AA65 BB27 FF04 FF28 JJ03 JJ19 JJ26 QQ24 QQ31 QQ35 QQ36 SS06 SS13 UU05 2G061 AA01 AB01 EA02 EB07 EC04 5C022 AA01 AB63 AC01 AC13 AC69 5C05 AE01 FF03 HA05

Claims (1)

[Claims] 1. A method in which a plurality of marks are attached to a surface and image data obtained by photographing a sample to which a tensile load is applied with a camera is processed in a predetermined image processing area by image processing. In a video extensometer that calculates the elongation of a sample by obtaining instantaneous position information in the tensile direction of the mark, the movement of each mark in the direction perpendicular to the tensile direction is detected from the image data in the image processing area. And a mark lateral movement tracking means for moving an image processing area in the video data in a direction orthogonal to the pulling direction so that each mark falls within the area.