JPH0695065B2 - Crack Growth Tracking Device for Crack Testing Equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is to observe or record the progress of cracks occurring in a test piece under tensile load (often subjected to repeated load) or bending load. The present invention relates to a crack progress tracking device for a crack testing device.

[Conventional technology]

In recent years, in order to observe or record the progress of cracks that occur in a test piece, it has been performed in recent years to image a crack occurrence location and observe or record the information using the imaging information. In other words, in order to capture a crack at a high resolution with a high resolution, a video camera or the like equipped with an optical system that captures images at a predetermined magnification (for example, about 100 times) is provided as the image capturing means, and image capturing information as the crack progress status is provided. For example, each time a set time elapses, it is sequentially recorded on a video tape or the like, and the reproduced image information is used to observe the crack progress.

By the way, the image pickup means is generally not capable of picking up an image of the entire test piece. Therefore, in order to track the crack occurrence point, conventionally, the imaging range of the image pickup means is set to the tip of the crack occurrence point of the test piece. (See, for example, JP-A-56-35006).

[Problems to be Solved by the Invention]

However, in this type of test, the crack range does not always appear on the surface portion of the test piece in the imaging range, and the crack inside the test piece progresses before the surface crack, and further cracks occur. When it progresses, an internal crack may appear on the imaging surface side. That is, the cracks appearing on the surface of the test piece may not be continuous but may appear in a discontinuous state.

In such a case, even if the tip portion of the crack is traced and imaged, the portion where continuous cracks are interrupted is determined to be the crack tip, so it is not possible to accurately capture the exact crack tip. There was an inconvenience.

The present invention has been made in view of the above circumstances, and its purpose is to track the progress of a crack using an imaging unit that cannot image the entire test piece, and if the crack is not continuous. Also, it is to be able to accurately identify and track the actual crack tip.

[Means for Solving the Problems]

A characteristic configuration of a crack progress tracking device of a crack testing apparatus according to the present invention is an image pickup means for picking up an image of a crack occurrence point of a load-applied test piece, and a position changing means for changing an image pickup position of the image pickup means with respect to the test piece. A crack position detecting means for detecting a crack position based on the imaged image information of the imaging means, and a specific point of the imaging field of view of the imaging means is a tip side position of the crack occurrence location of the test piece, In a crack progress tracking device of a crack test apparatus including a crack tracking control unit that operates the position changing unit based on detection information by a crack position detecting unit, the crack position detecting unit is a crack developing direction in an imaging visual field. A means for calculating the histogram of the luminance distribution in the direction intersecting with, and setting the scanning region along the crack propagation direction within the imaging field of view near its maximum value,
With a means for presetting a small range corresponding to a part of the scanning area in the scanning direction as a detection area for crack tip determination, and for all pixels in the detection area for crack tip determination Detects the ratio of pixels that are determined to be cracks, and when the ratio is greater than or equal to a preset ratio, complements the connection between pixels of discontinuous cracks in the detection area. The present invention is provided with a crack range correcting means for outputting as a continuous crack existing portion, and its operation and effect are as follows.

[Work]

That is, the specific point of the image pickup means is automatically changed by automatically changing the image pickup position of the image pickup means with respect to the test piece based on the crack image information so that the specific point of the test piece is located at the tip side position of the crack occurrence point of the test piece. The crack generation location is controlled so as to be positioned within the imaging visual field, and the present invention is as follows in order to specify the tip side position of the crack generation location at this time.

That is, the crack position detecting means calculates a histogram of the luminance distribution in the direction along the crack progressing direction of the imaging visual field, and means for setting the scanning region along the crack developing direction within the imaging visual field near its maximum value. And a means for presetting a small range corresponding to a part of the scanning area in the scanning direction as a detection area for crack tip determination, and scanning the scanning area within the imaging visual field to detect the detection area. For each time, the ratio of the pixels determined as the crack existing portion to all the pixels in the detection area is detected.

Then, when the ratio is equal to or higher than a preset ratio, the connection between the pixels of the discontinuous crack existing portion in the detection area is complemented and output as a continuous crack existing portion. Even when the generated cracks are not continuous on the imaging surface side of the test piece, it is highly possible to detect the virtual crack tip at the most advanced position.

〔The invention's effect〕

Therefore, the crack occurrence location is automatically controlled so as to be located within the imaging field of view, the progress of the crack is automatically tracked, and the crack tip detection accuracy is improved when the cracks are not apparently continuous. As a result, the location of cracks can be traced with high accuracy, and the progress of cracks can be conveniently observed or recorded.

〔Example〕

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

As shown in Fig. 1, the test equipment (1) is equipped with CT and CCT (J
A test piece (2) of IS standard or ASTM standard) is attached with a bolt or the like in a state in which a load is applied to a predetermined tension in the vertical direction.

However, in order to promote the generation of cracks due to the above-mentioned tensile load, the test piece (2) is brought into a vibrating state by repeatedly applying a predetermined load at a set cycle.

Then, the video camera (3) using the solid-state image pickup device as an image pickup means for picking up an image of the cracked portion of the test piece (2) serves as a position changing means for changing the image pickup position for the test piece (2). It is attached to the 3-axis pulse stage (4). Therefore, the imaging position of the video camera (3) with respect to the test piece (2) is
Left and right (X axis), front and back (Y axis), and up and down (Z axis)
The position can be changed in any direction.

Although not shown, the test piece (2) is illuminated from a predetermined angle so that the cracked portion looks brighter than its surroundings.

A crack position detecting means (100) for detecting a crack position based on the imaged image information of the video camera (3), and a visual field center as a specific point of the imaging visual field of the video camera (3) is the test piece (2). ) Crack tracking control means for controlling the controller (5) of the three-axis pulse stage (4) based on the detection information of the crack position detection means (100) so as to be at the tip side position of the crack occurrence point of (). A control device (6) using a microcomputer, which constitutes 101) and controls the operation of the test device (1) (start and stop of tensile load and vibration, and instruction of its value, etc.) is provided.

However, a fiberscope (3a) is attached to the video camera (3), and the cracked portion of the test piece (2) is kept in a non-contact state even under a high temperature or a corrosive atmosphere, and It is designed so that it can be magnified and imaged at a magnification of about 100 times. In other words, while using the video camera (3) having a low resolution (which is set to 512 × 512 dots), the state of the crack occurrence location is highly accurate in the imaging visual field range of 1 to ² cm ^2. It can be observed at.

In the figure, (7) is an image processor using a microcomputer for processing the imaged image information of the video camera (3), which operates according to a command from the control device (6). It is configured. or,
(8) is a system monitor for displaying image information of the video camera (3), (9) is a video monitor for displaying information processed by the image processor (7) and the control device (6), ( 10) is a printer for printing measurement data, (11) is a display for displaying various information such as measurement data and measurement conditions by the control device (6), and (12) is various setting information such as measurement conditions A keyboard for inputting and instructing the control device (6), (1
3) is a storage device for recording various measurement information such as measurement conditions and measurement data. For example, a floppy disk device or the like is used.

First, the outline of the measurement process of the generated cracks in the crack growth test of the test piece (2) will be described.

As shown in FIG. 2, the test piece (2) has a V-shaped notch (2a) formed on the right end side of a substantially intermediate portion in the vertical direction. Then, a preliminary crack (2b) (about 1 mm to 2 mm) is generated in advance to the left by applying a tensile load or a repeated load having a predetermined strength.

Then, while observing the image displayed on the system monitor (8), the position of the video camera (3) is adjusted so that the position where the preliminary crack (2b) is formed is located at the center of the imaging visual field (3b). Artificially adjust. Next, based on the test conditions and the like inputted in advance, the control device (6) operates the test device (1) while the preliminary crack (2
Make sure the position (2c) on the tip side of b) is located at the center of the screen.
Every time the set time elapses, the image processor (7) captures image information captured by the video camera (3) based on a command from the control device (6) (sixth).
(See FIG. 2A), the control device (6) detects a crack occurrence location based on the processed image information,
An operation command is output to the controller (5) of the three-axis pulse stage (4) to automatically track the crack growth, and the length of the generated crack and the displacement of the crack tip are based on the obtained image information. Is automatically measured.

That is, as shown in FIG. 3, before starting the test, an initial data file name for recording the crack development state of the test piece (2) is input to the control device (6) and the display is displayed. Based on the contents of the initial data displayed in (11), various test data such as test conditions are input using the keyboard (12). Then, after confirming the input contents, as described above, the tip position (2c) of the preliminary crack (2b) of the test piece (2) is positioned at the center of the visual field of the video camera (3). , Referring to the image information displayed on the system monitor (8),
The home position as the measurement start position is artificially set and the measurement is started.

Then, while displaying the measured intermediate data (elapsed measurement time, coordinate value of the crack tip side location, its length, etc.), for example, the tip side location of the crack occurrence location is automatically detected until the set time has elapsed. The position of the video camera (3) is automatically changed so that the video camera (3) is positioned at the center of the imaging field of view of the video camera (3), and the length of the crack generated is automatically measured. .

Incidentally, various measured data such as the length of the measured crack will be displayed on the display (11) together with the elapsed time information and will be recorded in the storage device (13), and if necessary. It will be output by the printer (10).

Next, based on the flowchart shown in FIG. 4, while explaining the process of automatically measuring the crack length,
Crack position detection means (100) and crack tracking control means (1
01) will be described in detail.

Every time the set time has elapsed, the vibration for exciting the test apparatus (1) is stopped for the set time (set to about 0.5 seconds), and the video is displayed while the vibration is stopped. After performing the process of automatic focus adjustment so that the focus of the camera (3) matches the position (2c) on the tip side of the crack occurrence portion of the test piece (2), the captured image information of the video camera (3) is taken in. .

After capturing the captured image information, the vibration for vibrating the test apparatus (1) is restarted, and the image processor (7) performs image processing to perform contrast enhancement and image smoothing processing. After that, the luminance levels of all pixels in the horizontal direction on the image, that is, for each line in the X-axis direction are added to calculate a histogram of the luminance distribution in the vertical direction of the screen, that is, the Z-axis direction, Then, the position where the brightness distribution is maximum is estimated as the position of the crack occurrence point on the Z axis (see FIG. 6B). Then, the X-axis near the position where the luminance distribution on the Z-axis is maximum and the X-axis in the imaging visual field are set so that the detection target is near the position where the luminance distribution is maximum on the Z-axis.
Set the scan area over the entire range on the axis. further,
Within the scanning area, a small range corresponding to a part of the scanning area in the scanning direction is preset as a detection area for crack tip determination.

Next, the image information is binarized based on the threshold value of the brightness level set in advance (see FIG. 6C), and based on the binarized image information, the crack range correction means described later. Estimate the tip position (2c) of the generated crack in the X-axis direction.

Therefore, the above-mentioned processing is performed by the crack position detecting means (10
0) and the crack position detecting means (100).
Is configured to detect the tip side position (2c) of the crack occurrence point of the test piece (2) based on the brightness distribution of the imaged image information of the video camera (3) as the image pickup means. It will be.

Then, based on the estimated X-axis and Z-axis values,
The pulse stage (4) is activated until its position coincides with the center of the visual field of the video camera (3). Accordingly, the position is changed based on the detection information by the crack position detection means (100) so that the visual field center as a specific point of the imaging visual field of the imaging means is located at the tip side position of the crack occurrence location of the test piece (2). Crack tracking control means (10)
1) is configured.

After that, based on the difference between the estimated X-axis and Z-axis values and the X-axis and Z-axis values at the time of the previous measurement,
Displacement of the crack tip over time is calculated, and the crack progress state is sequentially recorded while calculating the crack length and the like from the measurement start point based on the displacement.

To explain the contrast enhancement, as shown in FIG. 7, a histogram of the distribution of the brightness levels of all image information is calculated as a distribution of a fixed number of quantized pixels having the same brightness level, and the calculated brightness is the lowest brightness level. The contrast is emphasized by performing processing for extending the maximum brightness level between the maximum and minimum values that can be calculated.

The smoothing process of the image will be described. Since the crack is set so as to propagate in the horizontal direction on the screen, that is, in the X-axis direction, a so-called spatial filter is used to set the brightness level between adjacent pixels. I try to emphasize the change of.

That is, as shown in FIG. 8, the luminance level value of the pixel of interest (e) is calculated based on the following equation using eight pixels vertically, horizontally, and diagonally adjacent to the pixel of interest (e). The entire screen is smoothed by replacing the calculated value with the calculated value.

The processing by the crack range correcting means for estimating the tip position of the generated crack in the X-axis direction based on the binarized image information will be described below.

Two lines, that is, one line of pixels for which the position of the Z axis is estimated and pixels of one line vertically adjacent to the pixel are set as the scanning region, and image information of this scanning region is detected. The target area is set as a detection area for crack tip determination, which is a small area of 3 dots in the horizontal direction (X-axis direction) of 40 dots with 3 dots vertically, and the pixels in this detection area are detected. To do.

Then, the detection area is moved pixel by pixel along the X-axis direction from the right side of the screen toward the left side, that is, in the crack propagation direction. In the present invention, the movement of the detection area for each pixel is defined as the scanning of the detection area within the set scanning area. While scanning the detection area, the detection is performed based on whether or not the number of dots in the binarized bright portion in the detection area is equal to or more than a preset ratio (set to 50%). The connection between pixels located inside the region is complemented.

That is, 50% of the 3 × 40 dots in the detection area.
When more than 60 dots are occupied by a binarized bright area, the entire crack detection area is estimated as the crack existence range, and the discontinuous crack area (see Fig. 6 (c))
It is converted into a continuous linear binarized pixel (see FIG. 6D) in the axial direction.

However, in the process of converting into a linear binary image that is continuous in the X-axis direction described above, if only one line in the estimated Z-axis direction is processed, the generated crack meanders in the Z-axis direction. In such a case, the image information may be interrupted at an intermediate portion, so in reality, several lines are vertically adjacent to the estimated one line pixel in the Z-axis direction. The image information is also subjected to the process of converting it into the continuous linear binarized image described above.

Then, the left end portion of the continuous linear binarized image is
It is obtained as the position on the tip side of the generated crack.

Next, the process of the automatic focus adjustment will be described.

As shown in FIG. 5, every time the vibration of the test apparatus (1) is stopped, the test piece (2) of the video camera (3) is stopped.
While moving the position in the perspective direction, that is, the position in the Y-axis direction, 10 times in the front-back direction for each set distance, the captured image information is captured for each set distance movement, and the set range near the center of the screen (about the entire screen The differential value of the luminance change between adjacent pixels in the range of 256 × 256 dots, which is half, is obtained using a so-called Laplace filter or the like, and as shown in FIG. The distribution of the differential value of the change is obtained as a histogram of the number of differential values, that is, the value of the same density as the density of the contrast.

However, in the process of obtaining this histogram, the use of the image information only in the setting range near the center of the screen is to adjust the focus position near the center of the image, and in order to speed up the image processing. Is based on the fact that the processed image information should be small.

Then, the value of the density at the position where the change in contrast is the largest is set as the parameter (k) indicating the degree of contrast.
Is calculated from the value of the area (A) surrounded by the value of this parameter (k) and the maximum density value that causes the maximum brightness change.

That is, the value of the area (A) is first set to a predetermined value set in advance, the value of the parameter (k) in the area is obtained from the histogram, and the area (A) is sequentially increased or decreased. However, the value of the parameter (k) is calculated by searching for the point at which the value of the parameter (k) changes the most.

Then, the process of calculating the value of the parameter (k) is performed 10
After repeating 10 times, the values of these 10 parameters (k) are approximated as a quadratic curve as shown in FIG. 10 to obtain the maximum value (PK1) at which the value becomes maximum, and
The maximum value (PK2) of 0 parameters (k) is calculated.

Next, it is judged whether or not the difference between the maximum value (PK1) and the maximum value (PK2) is 80 μ or more which can be regarded as a substantially in-focus state. If it is 80 μ or less, the focus position of the video camera (3) is determined. To the maximum value (PK2). On the other hand, when it exceeds 80μ, it is determined that the maximum value (PK2) is wrong due to a malfunction of the image pickup processing, and the focus position of the video camera (3) is determined to the maximum value (PK1).

Then, the pulse stage (4) is operated so that the front-back direction of the video camera (3) with respect to the test piece (2), that is, the position in the Y-axis direction becomes the determined position (PK1 or PK2). By doing so, the focus position of the video camera (3) is controlled so as to coincide with the crack occurrence location of the test piece (2).

[Another embodiment]

In the above embodiment, the case where the length of the generated crack is also obtained is illustrated, but the present invention is merely for observing the progress status of the crack that occurs, in order to automatically track the crack progress. It can also be used, and various data such as obtained measurement values can be changed and set based on test conditions and the like.

Further, in the above-described embodiment, the case where the crack of the test piece propagates in the left-right direction on the screen is illustrated, but it may be in the up-down direction, and the crack propagation direction can be variously changed.

Further, in the above examples, in order to cause cracks in the test piece, an example of applying vibration by repeatedly applying a tensile load was illustrated, but simply by applying a tensile load or by applying a bending load. Good.

Further, in the above-described embodiment, the case where the crack position detecting means (100) is configured to detect the location where the brightness of the captured image information of the video camera (3) is the brightest as the location where the crack is generated has been exemplified. For example, by illuminating from the direction opposite to the test piece (2), the crack occurrence location may be darker than its surroundings, and the crack occurrence location is detected based on the brightness of the captured image information. The specific configuration of can be changed in various ways.

Further, in the above embodiment, the case where the video camera (3) itself is moved in the front-back direction with respect to the test piece (2) in order to automatically adjust the focus position of the video camera (3) has been illustrated. The focus position of the optical system of the video camera (3) may be adjusted, and the configuration of automatic focus adjustment can be variously changed.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

The drawings show an embodiment of the crack progress tracking device of the crack testing device according to the present invention, FIG. 1 is a block diagram showing the device configuration, and FIG. 2 is a plan view of the test piece showing the relationship between the test piece and the imaging visual field. , FIG. 3 is a flow chart showing an outline of the crack length automatic measurement processing, FIG. 4 is a flow chart showing a control operation in crack tracking, FIG. 5 is a flow chart showing a control operation in automatic focus adjustment, and FIG. ), (B),
(C) and (D) are explanatory diagrams of image processing, FIG. 7 is an explanatory diagram of control enhancement processing, FIG. 8 is an explanatory diagram of image smoothing, and FIG. 9 is an explanatory diagram of a histogram of contrast change, FIG. 10 is an explanatory diagram of parameters of contrast change. (2) ... Test piece, (3) ... Imaging means, (4) ... Position changing means, (100) ... Crack position detecting means, (101) ...
… Crack tracking control means.

Claims (2)

[Claims] 1. An image pickup means (3) for picking up an image of a crack generation portion of a test piece (2) to which a load is applied, and a position change for changing an image pickup position of the image pickup means (3) with respect to the test piece (2). A crack position detecting means (100) for detecting a crack position based on the imaged image information of the means (4) and the imaging means (3).
And the position based on the detection information by the crack position detection means (100) so that the specific point of the imaging field of the imaging means (3) becomes the position on the tip side of the crack occurrence location of the test piece (2). In a crack progress tracking device of a crack testing device, which comprises a crack tracking control means (101) for operating a changing means (4), the crack position detecting means (100) is a direction intersecting a crack developing direction in an imaging visual field. The histogram of the luminance distribution at, the means for setting a scanning region along the crack progress direction in the imaging field of view near the maximum value, and a small range corresponding to a part of the scanning region in the scanning direction. With a unit that is preset as a detection region for crack tip determination, the ratio of the pixels that are determined to be the crack existing portion with respect to all the pixels in the detection region for crack tip determination is detected, and the ratio thereof But Therefore, when the ratio is equal to or higher than the set ratio, it is equipped with a crack range correction means that complements the connection between pixels of the discontinuous crack existing portion in the detection area and outputs it as a continuous crack existing portion. The crack progress tracking device of the characteristic crack testing device. 2. The crack position detecting means (100), based on a brightness distribution of imaged image information of the image pickup means (3),
The crack progress tracking device according to claim 1, wherein the crack progress tracking device is configured to detect the position of the tip side of the crack occurrence point of the test piece (2).