CN109636800B - Method for measuring size of internal defect of object - Google Patents

Method for measuring size of internal defect of object Download PDF

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CN109636800B
CN109636800B CN201910080527.2A CN201910080527A CN109636800B CN 109636800 B CN109636800 B CN 109636800B CN 201910080527 A CN201910080527 A CN 201910080527A CN 109636800 B CN109636800 B CN 109636800B
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size
sample
internal defect
gray value
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CN109636800A (en
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杨晓
刘桂玲
刘学建
杨金晶
姚秀敏
黄政仁
陈忠明
陈健
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Shanghai Institute of Ceramics of CAS
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    • G06T2207/10081—Computed x-ray tomography [CT]
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Abstract

The invention provides a method for measuring the size of a defect in an object, which comprises the following steps: reconstructing the sample after detection to obtain an image of the internal defect; in the direction that the size of the internal defect needs to be measured, drawing a straight line in a mode that one end of a line segment is positioned outside the sample and the other end of the line segment is positioned in the internal defect, wherein one end of the line segment, which is positioned in the internal defect, is a defect end, and the other end of the line segment is a sample end; a gray value curve in the extending direction of the line segment is called, and gray values G2, G0 and G1 are respectively obtained; g3= G2- | G2-G1| × 10% is calculated when G2 is the peak value, and G3= G2+ | G2-G1| × 10% is calculated when G2 is the valley value; two points with the gray value G3 are selected near the wave crest or the wave trough of the gray value curve, and the displayed size between the two points is the actual size of the internal defect. According to the invention, the accurate measurement of the size of the tiny defect can be realized, the method has the characteristics of high sensitivity, reliable data and the like, and the error does not exceed the size of one pixel generally.

Description

Method for measuring size of internal defect of object
Technical Field
The invention belongs to the technical field of material performance detection, and particularly relates to a method for measuring the size of an internal defect of an object.
Background
At present, the basic principles of industrial CT detection are as follows: according to different attenuation coefficients when X-rays pass through different substances, attenuation functions of the different substances are obtained by utilizing a computer based on a mathematical physical equation through ray measurement, image processing technology and the like, so that internal information of the substances is obtained. Specifically, the sample to be examined is divided into a plurality of voxel units small enough, and the attenuation coefficient of each voxel unit can be regarded as a constant.
Then, by performing a CT imaging scan from multiple angles, the attenuation coefficient corresponding to each voxel unit can be obtained. In practical application, the CT value is introduced by taking the attenuation coefficient of water as a reference, and the CT value =
Figure 583447DEST_PATH_IMAGE001
. And the CT value of the voxel unit is corresponding to the gray value on the image, so called CT image can be obtained.
In the CT image obtained as described above, different materials are reflected by different gray values, the defect existing in the sample is reflected on the gray curve and appears as a peak or a trough on the smooth curve, and the size measurement of the defect can be realized by using the gray value difference of the peak or the trough on the gray curve.
Based on this, each industrial CT system produced by a large company is equipped with a dedicated dimension measurement software to realize manual/automatic measurement, and the basic principle of automatic measurement is a "full width at half maximum" method based on a CT image pixel 0, but when the defect size is close to or smaller than the effective beam width of a ray, automatic measurement is basically impossible. In contrast, the manual analysis determines the position of the two end points of the measured position by the analyst through the difference in gray levels of the reconstructed images. However, the manual measurement mode completely depends on the experience of an analyst and the judgment of naked eyes, has poor repeatability and low reliability, and has very large detection error especially for small defects of critical detection limit. In addition, the existing literature discloses a measurement method for identifying small defects based on image processing, but the measurement method generally extracts feature boundaries of images based on different algorithms, so that the measurement method has respective limitations, and cannot be widely and indiscriminately applied to actual engineering application.
Disclosure of Invention
The problems to be solved by the invention are as follows:
in view of the above problems, an object of the present invention is to provide a method for measuring the size of an internal defect of an object, which can accurately measure the size of the internal defect of the object by using an industrial X-ray CT nondestructive testing method, and has the characteristics of high sensitivity, reliable data, wide application, etc.
The technical means for solving the problems are as follows:
the invention provides a method for measuring the size of a defect in an object, which comprises the following steps:
after a panel detector is adopted to detect a sample by an industrial CT nondestructive detection method, a computer is used for reconstructing and obtaining an image of the internal defect of the sample;
after the position of the internal defect is determined, drawing a straight line in a mode that one end of a line segment is positioned outside the sample and the other end of the line segment is positioned in the internal defect in the direction in which the dimension of the internal defect needs to be measured by an image measuring tool of computer software, wherein one end of the line segment positioned in the internal defect is a defect end, and the other end of the line segment is a sample end;
a gray value curve in the extending direction of the line segment is taken, the gray value of the wave crest or the wave trough corresponding to the defect end is selected as G2, and the gray value corresponding to the sample end is G0;
moving the sample end from the outside to the inside of the sample along the extending direction of the line segment, and enabling the gray value corresponding to the sample end to be located in a region which is close to the wave crest or the wave trough and has a stable amplitude, wherein the gray value corresponding to the sample end is G1;
g3= G2- | G2-G1| × 10% is calculated when G2 is the peak value, and G3= G2+ | G2-G1| × 10% is calculated when G2 is the valley value;
selecting two points with the gray value G3 near the peak or the trough of the gray value curve, wherein the displayed size between the two points is the actual size of the internal defect.
Compared with the existing detection method, the method is particularly suitable for measuring the dimension of the fine defect when the dimension of the fine defect approaches the detection limit of equipment, and has the characteristics of high sensitivity, reliable data and the like, and the error usually does not exceed the dimension of one pixel.
In the present invention, the sample end is moved to select G1 as close as possible to G2. Thus, the measurement result is more accurate.
In the present invention, it is also possible that the internal defect is considered to be resolvable when | G1-G2| > (G1-G0) × 10%, and not resolvable otherwise. Thereby, it is possible to determine whether or not an internal defect exists on the inspection image.
In the present invention, the volume of the internal defect may be less than 1X 1mm 3 . Thus, the defect size detection error in different directions does not exceed the size of one pixel.
In the present invention, the detected sample may be detected by a small-angle digital linear scanning detection method. Thus, the internal defect size of a large flat-plate-shaped sample can be detected.
In the present invention, G0 may be a low value on the gray scale value curve and may also be a background value of air.
It is also possible in the present invention that the panel detector can be replaced with a line array detector when measuring the planar size of the internal defect.
The invention has the following effects:
the invention can provide a method for measuring the size of the internal defect of the object, can accurately measure the size of the internal defect of the object by an X-ray industrial CT nondestructive testing method, and has the characteristics of high sensitivity, reliable data, wide application and the like.
Drawings
Fig. 1 is a CT image of pore defects in the ceramic of example 1 and its corresponding gray scale value curve: wherein, (a) and (b) are to obtain a background value g0, a gray value g1 of the ceramic and a valley value g2 of the defect; (c) is the distance between two gray values g3 for confirming the defect;
FIG. 2 is an SEM observation of the dissection of embedded defects inside the ceramic;
FIG. 3 is a CT image of the ceramic weld of example 2 and its corresponding gray value curve: wherein, (a) and (b) are used for obtaining a background value g0, a gray value g1 of ceramic and a peak value g2 at a welding seam; (c) confirming the distance between two gray values g3 of the welding seam;
FIG. 4 is an anatomical SEM view of a weld;
fig. 5 is a CT image of inclusion defects inside the bulk sample of example 3 and its corresponding gray value curve: wherein, (a) and (b) are used for obtaining a background value g0, a gray value g1 of the ceramic and a peak value g2 of an inclusion defect; (c) Is the distance between two gray values g3 for confirming inclusion defects;
FIG. 6 is a dissected SEM view of inclusion defects;
FIG. 7 is a CT image of a solder joint inside a certain battery material of example 4 and its corresponding gray value curve: wherein, (a) and (b) are used for obtaining a back bottom value g0, a gray value g1 of the battery and a peak value g2 at a welding point; (c) confirming the distance between two gray values g3 of the welding spot;
FIG. 8 is a schematic of a caliper measurement of a weld spot.
Detailed Description
The present invention is further described below in conjunction with the following embodiments, which are to be construed as merely illustrative, and not limitative, of the present invention. The same or corresponding reference numerals denote the same components in the respective drawings, and redundant description is omitted.
A method of measuring the size of a defect within an object is disclosed. Specifically, after a panel detector is adopted to detect a sample to be detected by an industrial CT nondestructive detection method, an image of the internal defect of the sample to be detected is reconstructed and obtained by a computer. After the location of the defect is determined, the line is drawn in such a way that the line segment crosses the internal defect by means of an image measuring tool of the computer software. Specifically, drawing a line in the direction in which the defect needs to be measured in size, enabling one end of the line segment to be located outside the sample (namely, equivalently located in an air region) and the other end of the line segment to be located in an internal defect region, and then calling a gray value curve corresponding to each position in the extending direction of the line segment, wherein the value of the gray value curve is at least larger than the length of the line segment.
Then, on the gray value curve, the gray value of the peak or the trough corresponding to the defect end is selected as G2, and the gray value corresponding to the sample end is G0. And moving the sample end from the outside to the inside of the sample along the extension direction of the line segment, and enabling the gray value corresponding to the sample end to be located in an area which is close to the wave crest or the wave trough and has stable amplitude, wherein the gray value corresponding to the sample end is G1. When the gray value corresponding to the defect end is a peak (i.e., G2 is a peak), G3= G2- | G2-G1| × 10% is calculated, and when the gray value corresponding to the defect end is a trough (i.e., G2 is a trough), G3= G2+ | G2-G1| × 10% is calculated. Two points with the gray value G3 are selected near the wave crest or the wave trough of the gray value curve, and the displayed size between the two points is the actual size of the internal defect.
Further, when the absolute value of the difference between G1 and G2 (i.e., | G1-G2 |) > (G1-G0) × 10%, it is considered that the internal defect can be resolved and is detectable by the above operation. Otherwise, the internal defect is not resolved and detection is not needed. In the present invention, the volume of the internal defect is preferably less than 1X 1mm 3 The detected sample can also be detected by a small-angle digital linear scanning detection method.
In addition, since the scanning interval of each layer of the line array detector is large (usually 1 mm) in the detection process, the detection precision in the z direction is 1mm, and the measurement error is large. Therefore, if the line array detector is adopted in the method provided by the invention, the method can only be suitable for measuring the size of an x-y plane, in other words, when only the plane size of the defect needs to be acquired, either the panel detector or the line array detector can be used.
According to the invention, the difference between the gray scale curve of the object and the defect and the gray scale values of the object and the defect obtained by industrial CT nondestructive testing is used for realizing the accurate measurement of the size of the small defect, and the error is usually not more than the size of one pixel. Compared with the existing detection method, the method is particularly suitable for measuring the dimension of the fine defect close to the detection limit of the equipment, and has the characteristics of high sensitivity, reliable data and the like.
The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also merely one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.
(example 1)
The present embodiment is used for accurately measuring the size of the ceramic pre-buried internal defect as a test sample, and for confirming that the final measurement error is less than the size of one pixel. Fig. 1 is a CT image of pore defects in the ceramic of example 1 and its corresponding gray scale value curve: wherein, (a) and (b) are to obtain a background value g0, a gray value g1 of the ceramic and a valley value g2 of the defect; and (c) is the distance between two gray values g3 for confirming defects. FIG. 2 is an SEM image of the dissection of embedded defects inside the ceramic. As shown in fig. 1, the defect appears as a valley on the gray scale curve.
Firstly, a conventional panel detector is adopted to carry out CT nondestructive detection on the detected ceramic, and an image of the internal defect of the ceramic is obtained. As described above, the image measuring tool using software draws a line in the direction in which the defect needs to be measured, and the line crosses the defect part that needs to be measured, and simultaneously retrieves the gray value curve corresponding to each position on the line. As shown in fig. 1 (a), the line segment has an initial length of 5.51mm, but is by no means limited thereto as long as the line segment satisfies the above requirements.
Then, on the gray value curve corresponding to the line segment, the gray value of the valley corresponding to the defect end is selected as the valley value g2, and the gray value of the read point a is 1574. At this time, a point 5.51mm away from the valley g2 is a point corresponding to the sample end, and the gray value of the point B is read to be 126, i.e., the background value g0 of the entire detection. Then, the sample end is moved from the outside to the inside of the sample along the extending direction of the line segment, and accordingly, the point corresponding to the sample end on the gray scale value curve is also moved toward the valley g2, and when the point is located in the region where the amplitude of the wave near the valley g2 is stable, the point is the gray scale value g1 corresponding to the sample end, as shown in (B) of fig. 1, in this embodiment 1, a point 1.82mm away from the peak g2 is selected, and the gray scale value of the point B' is read as 1984. The gray value g1 may be selected as a gray value corresponding to a point located in a region where the amplitude of the wave near the bottom g2 is stable, for example, in embodiment 1, a gray value corresponding to any point in a region where the amplitude fluctuation is slight (gentle) from 0.6mm to 3.0mm may be selected as the gray value g1.
Then, the difference in gray level between the ceramic and the internal defect was calculated as g1-g2, and further calculated as g1-g 2= 410 > (g 1-g 0) × 10% = 186, so that the defect was regarded as being conspicuous and recognizable. A grayscale value g3= g2+41=1615 is calculated by 10% of the difference between the two values, i.e., | g1-g2| × 10% = 41. Next, two points with a gray-level value of 1615 are selected near the valley g2 on the gray-level curve and labeled as the gray-level value g3, and at this time, as shown in fig. 1 (c), the size displayed between the two gray-level values g3 is 0.21mm, which is the measured size of the internal defect.
And finally, observing the internal defects by adopting an SEM scanning electron microscope after the internal defects are dissected, wherein the measurement precision is about 1 mu m. As shown in fig. 2, the internal defect size is 237 μm, i.e., 0.237mm, which can be considered as the actual size of the internal defect. The industrial CT measurement result of this embodiment is 0.21mm with an error of about 0.027mm, while the length × width of the pixel size detected by the present CT is 0.08mm × 0.08mm, and therefore the error is smaller than the size of one pixel. As can be seen from this, according to embodiment 1, the industrial CT can accurately measure the size of the internal defect without damaging the ceramic to be inspected, and the final measurement error is smaller than the size of one pixel.
(example 2)
The present embodiment is used for accurately measuring the size of a weld of a ceramic sample as a test sample, and for confirming that the final measurement error is less than the size of one pixel. Fig. 3 is a CT image of the ceramic weld of example 2 and its corresponding gray value curve: wherein, a) and b are used for obtaining a background value g0, a gray value g1 of ceramic and a peak value g2 at a welding seam; and (c) determining the distance between two gray values g3 of the welding seam. FIG. 4 is an SEM image of the weld seam. As shown in fig. 3, the weld exhibits a peak on the gray curve.
Firstly, a conventional panel detector is adopted to carry out CT nondestructive detection on the detected ceramic, and an image of the internal defect of the ceramic is obtained. As described above, the image measuring tool using software draws a line in the direction in which the defect needs to be measured, and the line segment crosses over the defect portion that needs to be measured, and simultaneously extracts the gray scale value curve corresponding to each position on the line. As shown in fig. 3 (a), the line segment has an initial length of 25.94mm, but is by no means limited thereto as long as the line segment satisfies the above requirements.
Then, on the gray scale value curve corresponding to the line segment, the gray scale value of the trough corresponding to the defect end is selected as the peak value g2, and the gray scale value of the point a is read to be 3832. At this time, a point 25.94mm away from the peak g2 is a point corresponding to the sample end, and the gray value of the point B is read to be 54, i.e., the background value g0 of the entire detection. Then, the sample end is moved from the outside to the inside of the sample along the extending direction of the line segment, and accordingly, the point corresponding to the sample end on the gray scale value curve is also moved toward the peak value g2, and when the point is located in the region near the peak value g2 where the amplitude is stable, the point is the gray scale value g1 corresponding to the sample end, as shown in (B) of fig. 3, in this embodiment 2, a point 1.70mm away from the peak value g2 is selected, and the gray scale value of the point B' is read as 1906. The gray value g1 may be selected as a gray value corresponding to a point located in a region where the amplitude of the wave near the peak value g2 is stable, for example, in embodiment 2, a gray value corresponding to any point in a region where the amplitude fluctuation is slight (gentle) from 0.5mm to 20.0mm may be selected as the gray value g1.
Then, next, the difference in the gray level between the bead and the ceramic sample was calculated as g2-g1, and further calculated as g2-g1= 1922 > (g 1-g 0) × 10% = 185, so that it was considered that this defect was conspicuous and recognizable. The gray value g3= g2-192=3640 is calculated by 10% of the difference between the two values, i.e., | g1-g2| × 10% = 192. Next, two points with the gray value 3640 are selected near the peak value g2 on the gray value curve and marked as the gray value g3, and at this time, as shown in (c) of fig. 3, the size displayed between the gray values g3 of the two points is 0.13mm, which is the measured size of the weld.
And finally, observing the internal defect by adopting an SEM scanning electron microscope after the internal defect is dissected, wherein the measurement precision is about 1 mu m. As shown in fig. 4, the solder width is 117 μm, i.e. 0.117mm, which can be considered as the actual size of the weld. The industrial CT measurement is 0.13mm with an error of about 0.013mm, while the present CT detects pixel sizes with a length x width of 0.08mm x 0.08mm, and therefore with an error of less than one pixel size. As can be seen from this, according to embodiment 1, the industrial CT can accurately measure the size of the internal defect without damaging the ceramic to be inspected, and the final measurement error is smaller than the size of one pixel.
(example 3)
The present embodiment is used for accurately measuring the size of an inclusion defect in a bulk sample as a test sample, and for confirming that the final measurement error is less than the size of one pixel. Fig. 5 is a CT image of inclusion defects inside the bulk sample of example 3 and its corresponding gray value curve: wherein, (a) and (b) are used for obtaining a background value g0, a gray value g1 of the ceramic and a peak value g2 of an inclusion defect; (c) Is the distance between two gray values g3 for confirming inclusion defects. Figure 6 anatomical SEM observations of inclusion defects. As shown in fig. 5, the inclusion defect appears as a peak on the gray scale curve, and the complex background gray scale value of the sample is high.
Firstly, a conventional panel detector is adopted to carry out CT nondestructive testing on the tested ceramic, and an image of the internal defect of the ceramic is obtained. As described above, the image measuring tool using software draws a line in the direction in which the defect needs to be measured, and the line crosses the defect part that needs to be measured, and simultaneously retrieves the gray value curve corresponding to each position on the line. As shown in fig. 5 (a), the line segment has an initial length of 8.34mm, but is by no means limited thereto as long as the line segment satisfies the above requirements.
Then, on the gray value curve corresponding to the line segment, the gray value of the trough corresponding to the defect end is selected as the peak value g2, and the gray value of the point a is read to be 55622. At this time, a point 8.34mm away from the peak value g2 was a point corresponding to the sample end, and the gray value of the point B was read as 52483, i.e., the background value g0 of the entire detection. Then, the sample end is moved from the outside to the inside of the sample along the extending direction of the line segment, and accordingly, the point corresponding to the sample end on the gray scale value curve is also moved toward the peak value g2, and when the point is located in the region where the amplitude of the wave near the peak value g2 is stable, the point is the gray scale value g1 corresponding to the sample end, as shown in (B) of fig. 5, in this embodiment 3, a point 1.37mm away from the peak value g2 is selected, and the gray scale value of the point B' is read as 53784. The gray value g1 may be selected as a gray value corresponding to a point located in a region where the amplitude of the wave near the peak value g2 is stable, for example, in embodiment 3, a gray value corresponding to any point in a region where the amplitude fluctuation is slight (gentle) of about 0.8mm to 6.5mm may be selected as the gray value g1.
Next, the difference in gray level between the inclusion defect and the bulk sample was calculated as g2-g1, and further calculated as g2-g1= 1838 > (g 1-g 0) × 10% = 130, so that the defect was considered to be conspicuous and recognizable. The grayscale value g3= g2-184=55438 is calculated by taking | g1-g2| × 10% =184, which is 10% of the difference between the two values. Next, two points with a gray value of 55438 are selected near the peak value g2 on the gray value curve and labeled as the gray value g3, and at this time, as shown in fig. 5 (c), the size displayed between the gray values g3 of the two points is 0.11mm, which is the measured size of the inclusion defect.
And finally, observing the inclusion defect by adopting an SEM (scanning electron microscope) after the inclusion defect is dissected, wherein the measurement precision is about 1 mu m. As shown in fig. 6, the size of the inclusion defect is 109 μm, i.e., 0.109mm, and the size can be considered as the actual size of the inclusion defect. The industrial CT measurement is 0.11mm with an error of about 0.001mm, while the present CT detects pixel sizes with a length x width of 0.08mm x 0.08mm, and therefore with an error of less than one pixel size. As can be seen from this, according to embodiment 1, the industrial CT can accurately measure the size of the internal defect without damaging the ceramic to be inspected, and the final measurement error is smaller than the size of one pixel.
(example 4)
The present embodiment is used for accurately measuring the size of any solder joint in a certain battery sample as a sample to be tested, and for confirming that the measurement error is smaller than the size of one pixel. FIG. 7 is a CT image of a solder joint inside a certain battery material of example 4 and its corresponding gray value curve: wherein, (a) and (b) are used for obtaining a back bottom value g0, a gray value g1 of the battery and a peak value g2 at a welding point; and (c) the distance between two gray values g3 for confirming the welding spot. FIG. 8 is a schematic diagram of caliper measurements of a weld. As shown in fig. 7, the welding point appears as a peak on the gray scale curve.
Firstly, a conventional panel detector is adopted to carry out CT nondestructive detection on the detected ceramic, and an image of the internal defect of the ceramic is obtained. As described above, the image measuring tool using software draws a line in the direction in which the defect needs to be measured, and the line crosses the defect part that needs to be measured, and simultaneously retrieves the gray value curve corresponding to each position on the line. As shown in fig. 7 (a), the line segment has an initial length of 16.15mm, but is by no means limited thereto as long as the line segment satisfies the above requirements.
Then, on the gray value curve corresponding to the line segment, the gray value of the trough corresponding to the defect end is selected as the peak value g2, and the gray value of the read point a is 2782. The point at 16.15mm distance from the peak g2 is the point corresponding to the sample end, and the gray value at the point B is read as 113, i.e., the background value g0 of the entire test. Then, the sample end is moved from the outside to the inside of the sample along the extending direction of the line segment, and accordingly, the point corresponding to the sample end on the gray scale value curve is also moved toward the peak value g2, and when the point is located in the region where the amplitude of the wave near the peak value g2 is stable, the point is the gray scale value g1 corresponding to the sample end, as shown in (B) of fig. 7, in this embodiment 4, a point 2.86mm away from the peak value g2 is selected, and the gray scale value of the point B' is read as 1166. The gray-scale value g1 may be selected as long as it corresponds to a point located in a region where the amplitude near the peak value g2 is stable, and for example, in embodiment 4, a gray-scale value corresponding to any point in a region where the amplitude fluctuation is slight (gentle) from 1.8mm to 5.0mm may be selected as the gray-scale value g1.
Next, the gray scale difference g2-g1 between the solder joint and the battery sample was calculated, and further, g2-g1= 1616 > (g 1-g 0) × 10% = 105 was calculated, so that the solder joint was regarded as being distinct and recognizable. The gray value g3= g2-162=2620 is calculated by 10% of the difference between the two values, | g1-g2| × 10% =162, and then two points with the gray value 2620 are selected near the peak value g2 on the gray value curve and labeled as the gray value g3, and at this time, as shown in fig. 7 (c), the size 0.44mm displayed between the gray values g3 of the two points is the measured size of the welding point.
Finally, the battery sample was dissected and the size of the weld was measured by a micrometer, which was accurate to 0.001mm. As shown in fig. 8, the size of the weld spot was measured to be 0.476mm, which can be considered as the actual size of the weld spot. The industrial CT measurement is 0.44mm with an error of about 0.036mm, while the present CT detects pixel sizes of 0.08mm x 0.08mm in length by width, and therefore errors of less than one pixel size. As can be seen from this, according to embodiment 1, the industrial CT can accurately measure the size of the internal defect without damaging the ceramic to be inspected, and the final measurement error is smaller than the size of one pixel.
In conclusion, the method provided by the invention has the advantages of higher repeatability, high reliability, very small detection error especially for the internal defects of critical detection limit, and wide and undifferentiated application in practical engineering application.
The above embodiments are intended to illustrate and not to limit the scope of the invention, which is defined by the claims, but rather by the claims, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (7)

1. A method of measuring the size of a defect within an object, comprising:
after a panel detector is adopted to detect a sample by an industrial CT nondestructive detection method, a computer is used for reconstructing and obtaining an image of the internal defect of the sample;
after the position of the internal defect is determined, drawing a straight line in a mode that one end of a line segment is positioned outside the sample and the other end of the line segment is positioned in the internal defect in the direction in which the dimension of the internal defect needs to be measured by an image measuring tool of computer software, wherein one end of the line segment positioned in the internal defect is a defect end, and the other end of the line segment is a sample end;
a gray value curve in the extending direction of the line segment is taken, the gray value of the wave crest or the wave trough corresponding to the defect end is selected as G2, and the gray value corresponding to the sample end is G0;
moving the sample end from the outside to the inside of the sample along the extension direction of the line segment, and enabling the gray value corresponding to the sample end to be located in a region which is close to the wave crest or the wave trough and has a stable amplitude, wherein the gray value corresponding to the sample end is G1;
g3= G2- | G2-G1| × 10% is calculated when G2 is the peak value, and G3= G2+ | G2-G1| × 10% is calculated when G2 is the valley value;
selecting two points with the gray value G3 near the peak or the trough of the gray value curve, wherein the displayed size between the two points is the actual size of the internal defect.
2. The method of claim 1, wherein the sample end is moved as close to G2 as possible to pick G1.
3. The method of claim 1, wherein the size of the internal defect is determined by considering the internal defect as being resolvable when | G1-G2| > (G1-G0) × 10%, and otherwise, as being indistinguishable.
4. A method of measuring the size of an internal defect in an object according to claim 1, wherein the internal defect has a volume of less than 1 x 1mm 3 。
5. The method of claim 1, wherein the inspection of the inspected sample is performed by a small angle digital linear scanning inspection method.
6. The method of claim 1, wherein G0 is a low value on the gray value curve and is also a background value of air.
7. A method of measuring the size of a defect in an object according to claim 1, wherein the panel detector is replaced by a line array detector when measuring the planar size of the internal defect.
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