A defect depth positioning method and detection device for radiographic detection

Abstract

The present invention discloses a method and device for depth positioning of defects in radiographic detection, comprising: step S1: measuring the actual size of the defect; step S2: placing a ruler on the source side and the detector side surface of the inspected part where the defect is located, and measuring the distance between the rulers to capture an image; step S3: calculating the magnification ratio of the ruler; step S4: calculating the distance between the ray source and the detector, and further calculating the distance from the defect to the ray source measuring ruler or the detector side ruler. The present invention utilizes the magnification ratio and spacing of the two rulers to obtain the distance from the ray source to the actual imaging area of ​​the detector, which is difficult to measure accurately, and combines the magnification ratio of the defect to obtain the distance from the defect to the source side surface ruler or the detector side surface ruler, thereby achieving depth positioning. The present invention has low use conditions, strong operability, and good applicability, and can provide assistance for the polishing and trimming of defects in the material forming process.

Description

Technical Field

[0001] The present invention relates to the field of ray detection, and in particular to a defect depth positioning method and a detection device for ray detection. Background Art

[0002] Radiographic testing, with its advantages of high sensitivity, intuitive results, and mature technology, is widely used for internal defect detection in the industrial sector. Its basic principle is to use radiation to penetrate the inspection area and form a projection on film. Defects are determined based on changes in the blackness of the projected image. Because the resulting image is a projection of a three-dimensional structure onto a two-dimensional plane, depth-wise density variations are overlapped and compressed onto the same plane, making it impossible to obtain depth-wise density variation information. This has long been a limitation of radiographic testing for defect location.

[0003] To address the problem of defect depth positioning, patent document CN114965519A (patent number 202210570837.4) discloses a method and system for positioning the internal structure of an object based on digital X-ray imaging. This method provides a method for positioning defects in the depth direction, but has two limitations: First, the positions of the detector and the ray source need to be converted once, which is not possible for a rod anode X-ray machine that penetrates deep into an annular part; second, this method requires accurate measurement of the distance from the ray emission position to the detector imaging plane. During actual detection, the actual emission position of the X-ray and the actual imaging area of ​​the detector are encapsulated in the equipment, making it difficult to accurately measure. Patent document CN105092614B (patent number 201510554183.6) discloses a system and method for detecting the depth of point defects in castings using X-rays. This method determines the defect depth by moving the defect and combining it with the principle of similar triangles, providing another defect depth location method. However, this method is only applicable to smaller point defects. For large or large defects, the defect image may undergo significant deformation during movement, thereby affecting the location accuracy. On the other hand, the actual emission position of the X-rays is difficult to accurately determine, which may affect the measurement results. Summary of the Invention

[0004] The purpose of the present invention is to address the issues raised in the aforementioned background and the limitations of defect depth calculation by providing a defect depth location method for radiographic inspection. This method first uses the defect's displacement distance on the defect plane as a scale to calculate the pixel size and obtain an accurate defect size. Scales of similar defect size are then placed on the detector side and the radiation source side of the defect, respectively. The defect's depth is determined by the magnification ratio of the two scales and the distance between them.

[0005] To solve this technical problem, the technical solution of the present invention is:

[0006] In one aspect, a method for locating the depth of a defect by radiographic inspection is provided, comprising the following steps:

[0007] Step S1: measuring the size of the defect in the workpiece;

[0008] Step S2: placing a first ruler and a second ruler on the ray source side and the detector side of the defect respectively, measuring the distance between the first ruler and the second ruler, and capturing an image;

[0009] Step S3: measuring the image sizes of the first scale, the second scale, and the defect, and calculating the magnification ratio between the image size and the actual size respectively;

[0010] Step S4: Calculate the distance between the ray source and the detector imaging plane using the magnification ratio of the first scale and the second scale, and calculate the distance from the defect to the first scale and the second scale using the distance and the magnification ratio of the defect.

[0011] The size of the defect in step S1 can be measured in one of the following two ways:

[0012] In step S1, the defect in the workpiece is measured by moving it. Specifically, the defect is first moved to the detector imaging area to capture the result image, and the number of pixels of the defect image is counted in the result image. Secondly, the defect is moved. When the difference between the number of pixels moved by the defect and the number of pixels of the defect itself is the smallest, the movement distance of the defect is recorded at this time. The pixel size is calculated based on the movement distance of the defect and the number of moved pixels, and then the actual size of the defect is obtained.

[0013] In step S1 , a ruler may also be used to measure defects in the workpiece.

[0014] In step S1, the detector is first calibrated. Once a defect is detected, the motion control module is used to move the defect to the center of the detector's imaging area, and an image is captured. A grayscale distribution of the defect is obtained in the resulting image, and the number of pixels in the defect image is counted. The motion control module is then used to move the defect image. When the difference between the number of pixels moved by the defect and the number of pixels in the defect itself is minimized, the distance the defect has moved is recorded.

[0015] Minimum difference means that when moving, the number of moving pixels of the defect image will gradually approach the number of pixels of the defect image itself, and then the difference between the two will increase. Therefore, there is a step distance that minimizes the difference between the number of moving pixels of the defect image and the number of pixels of the defect image itself. This step distance is an integer multiple of the minimum step accuracy.

[0016] The actual size of the defect is calculated using the following formula:

[0017]

[0018] in, is the actual size of the defect, is the moving distance of the defect, is the number of moving pixels of the defect, is the number of pixels of the defect in the center area of ​​the detector.

[0019] In step S2, the selection of the scale material, size, and placement position are as follows:

[0020] The first and second scales are made of the same material as the workpiece;

[0021] The difference between the actual size of the first ruler and the second ruler and the defect size measured in step 1 is as small as possible. "As small as possible" means that among the series of rulers with gradient sizes, the two rulers closest to the defect size measured in step S1 should be selected;

[0022] The first scale and the second scale are preferably placed on the ray source side surface and the detector side surface where the defect is located.

[0023] Preferably, the first scale and the second scale are flat plate hole type image quality meters.

[0024] In step S3, the calculation formula for the magnification ratio of the first scale and the second scale is:

[0025]

[0026]

[0027] in, is the magnification ratio of the first scale, is the distance from the ray emission position to the actual imaging plane of the detector, is the distance from the ray emission position to the first scale, is the size of the image of the first ruler, is the actual size of the first ruler, is the distance between the first scale and the second scale, is the size of the image of the second ruler, is the actual size of the second ruler.

[0028] In step S4, the distance between the ray emission position and the detector imaging plane is calculated as follows:

[0029]

[0030] in, is the distance from the ray emission position to the actual imaging plane of the detector, is the distance between the first scale and the second scale, is the size of the image of the first ruler, is the size of the image of the second ruler, is the actual size of the second ruler, is the actual size of the first ruler.

[0031] The calculation formulas for the distance from the defect to the first scale and the second scale are:

[0032]

[0033]

[0034] in, is the distance from the defect to the first scale, is the distance between the first scale and the second scale, is the size of the defect image in the image obtained in step S2, is the size of the image of the second ruler, is the defect size measured in step S1, is the size of the image of the first ruler, is the actual size of the first ruler, is the actual size of the second ruler.

[0035] On the other hand, the present invention also provides a device for detecting the depth of a defect by radiographic detection, comprising a ray excitation module, a workpiece clamping module, an imaging module, a motion control module, a data processing module, and a display module;

[0036] The ray excitation module is used to generate rays; the workpiece clamping module is used to clamp the inspected workpiece; the imaging module is used to receive ray radiation signals and generate images; the motion control module is used to control the movement of the ray excitation module, imaging module and workpiece clamping module, and display the movement distance; the data processing module is used to calculate and process the various data obtained to obtain calculation results including defect depth; the display module is used to control the parameters of the ray excitation module and imaging module, and display the imaging results and calculation results;

[0037] The imaging module is typically a digital detector array or film.

[0038] The beneficial effects of the present invention are:

[0039] This depth positioning method for radiographic defect detection has the following advantages:

[0040] 1. The depth of the defect is accurately located. The placement of the first and second scales and their approximation to the defect size make the difference in the magnification ratio between the scales and the defect very small, which in principle has a good depth positioning effect.

[0041] 2. Low usage conditions. Since the X-ray digital imaging system usually operates in an automated manner, the flat-panel detector, X-ray source and workpiece mounting device controlled by the motion module are easy to meet. At the same time, the measuring scale flat-panel hole image quality meter is a common X-ray detection tool.

[0042] 3. It has a wide range of applications, not only suitable for common X-ray sources, but also for rod anode X-ray sources, and not only suitable for point defects, but also for other larger defects.

[0043] 4. Simple operation. The defect depth positioning method provided by the present invention can accurately locate the depth direction of the defect. Combined with the fast imaging characteristics of radiographic digital imaging, it can efficiently locate the defect in three dimensions, providing support for defect polishing and improving defect treatment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the difference in the distance from the radiation source to the detector measured by the method of the present invention and other invention methods;

[0045] Figure 2 This is a schematic diagram of the principle of the method for locating the depth of a defect by radiographic detection according to the present invention;

[0046] Figure 3 It is a principle block diagram of the detection device of the present invention. DETAILED DESCRIPTION

[0047] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0048] The features of various aspects of the embodiments of the present invention will be described in detail below. In the detailed description below, many specific details are provided to provide a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can also be implemented without these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is not limited to any specific settings and methods provided below, but rather covers all product structures, any improvements, replacements, etc. of the methods covered without departing from the spirit of the present invention. In the various drawings and the following description, well-known structures and technologies are not shown to avoid unnecessary ambiguity in the present invention.

[0049] Example:

[0050] The present invention will be further described below with reference to the accompanying drawings and examples. Figure 1 and Figure 2 , Figure 2 This is a schematic diagram of the principle of the method for locating the depth of defects detected by ray detection according to the present invention. The distance from the ray emission position to the detector imaging plane is calculated. f ,like Figure 1 The conventional method calculates the distance between the radiation source packaging surface and the detector packaging surface. f *, f and f Differences in * may result in deviations in defect depth positioning.

[0051] The detailed process of the radiographic defect depth positioning method of the present invention is as follows:

[0052] 1. Measure the actual size of the defect. First, calibrate the detector according to the method recommended by the detector manufacturer. Then, use the motion control module to make the detected defect located in the center of the image to prevent the defect image from being significantly deformed in length during the subsequent measurement process. Collect the detected image at this time and use image analysis software to obtain the grayscale distribution map of the longest direction of the defect. Determine the boundary between the defect image and the background image on the grayscale map and record the number of pixels representing the defect image at this time. Then, the motion control module is used to move the inspected part where the defect is located relative to the ray source and the detector. At this time, the image of the defect moves in the opposite direction. During the movement, the pixels at the defect boundary are observed and the pixel distance of the defect boundary pixels is calculated. As the moving distance increases, the number of pixels moved in the defect image also increases. The number of pixels moved in the defect image is proportional to the distance. The difference shows a trend of decreasing first and then increasing. If there is a moving distance , when the moving distance is or hour( is the minimum step accuracy of the motion system), the number of pixel movements of the defect image is The difference between the two increases, then the moving distance At The gap is the smallest, record the moving distance at this time , the size of the defect can be expressed as:

[0053] (1)

[0054] in, is the measured size of the defect, is the moving distance of the defect, is the number of moving pixels of the defect, is the number of pixels of the defect in the center area of ​​the detector.

[0055] This measurement method calculates pixel size based on the distance a defect moves within the defect plane. This distance is approximately equal to the defect itself, avoiding measurement errors caused by a large size difference between the scale and the defect, or by the defect and scale not being at the same depth plane. This method offers high accuracy and can keep defect measurement errors within the minimum step accuracy of the motion module.

[0056] Other high-precision non-destructive testing methods can also be used to measure the size of defects, such as microfocus CT.

[0057] 2. From the flat-plate hole-type image quality meter made of the same material as the inspected part, select two flat-plate hole-type image quality meters with 4T hole diameters closest to the defect size measured in step 1 as the first and second scales, and place them on the source side surface and detector side surface of the inspected part respectively to collect images. If the scale on the result image overlaps with the defect image, the position of the first or second scale should be readjusted so that the three images do not overlap.

[0058] When acquiring images, the images of the defect, the first scale, and the second scale should be as close as possible but not overlap, so that the magnification ratios of the three are closest without affecting the pixel count statistics of their respective images.

[0059] 3. Measure the image size of the first scale, the second scale, and the defect, and calculate the magnification ratio between the image size and the actual size. Since the actual sizes of the first scale and the second scale are known, the image size is obtained by multiplying the number of pixels by the detector element size. Therefore, the formula for calculating the magnification ratio of the first scale and the second scale is:

[0060] (2)

[0061] (3)

[0062] in, is the magnification ratio of the first scale, is the distance from the ray emission position to the actual imaging plane of the detector, is the distance from the ray emission position to the first scale, is the size of the image of the first ruler, is the actual size of the first ruler, is the distance between the first scale and the second scale, is the size of the image of the second ruler, is the actual size of the second ruler.

[0063] 4. Calculate the distance between the ray emission position and the detector imaging plane using the magnification ratio of the first and second scales , calculated using Calculate the distance from the defect to the first scale based on the defect magnification ratio or the distance of the second ruler Combining the magnification ratio formulas of the first and second scales, the distance between the ray emission position and the detector imaging plane can be obtained. The calculation formula is:

[0064] (4)

[0065] in, is the distance from the ray emission position to the actual imaging plane of the detector, is the distance between the first scale and the second scale, is the size of the image of the first ruler, is the size of the image of the second ruler, is the actual size of the second ruler, is the actual size of the first ruler.

[0066] Since the actual location of the ray and the actual imaging plane of the detector cannot be determined in engineering applications, the distance from the ray emission location to the detector, the distance from the ray emission location to the workpiece surface, or the distance from the workpiece surface to the detector cannot be accurately measured. The only distance that can be accurately measured in the position relationship is the distance from the first scale to the second scale. , which is the distance between the source side surface of the workpiece and the detector surface. Therefore, when measuring the actual depth position of the defect, the distance between the defect and the workpiece surface is obtained. or It is more practical than measuring the distance between the defect and the radiation source or detector, and is also more convenient for polishing and trimming the defect.

[0067] The calculation formulas for the distance from the defect to the first scale and the second scale are:

[0068] (5)

[0069] (6)

[0070] in, is the distance from the defect to the first scale, is the distance between the first scale and the second scale, is the size of the defect image in the image obtained in step 2, is the size of the image of the second ruler, is the defect size measured in step 1, is the size of the image of the first ruler, is the actual size of the first ruler, is the actual size of the second ruler.

[0071] In a specific embodiment, the defect is a 4T hole in an aluminum flat-plate image quality indicator, numbered 25. The first and second scales are flat-plate image quality indicators (4T holes), numbered 20 and 32, respectively, placed on the source-side and detector-side surfaces of the inspected part. To verify error and validity, the actual value of the defect relative to scale 2 is preset to 38.44 mm. The results of the calculations in each step using the method of the present invention are as follows:

[0072] According to formula (1), mm, where , obtained by reading the moving distance of the workpiece clamping module, , calculated by observing the pixel coordinates of the defect boundary before and after the movement, , obtained by measuring the pixel coordinates of the defect boundary and calculating the distance between the two boundary coordinates;

[0073] Calculate the magnification ratio of the first scale according to formula (2): =4.2224, where , obtained by the detector pixel size (0.1mm) and the number of pixels of the first scale (85.8), , is a known quantity, which can be obtained by consulting the instruction manual of the flat-plate aperture image quality meter;

[0074] Calculate the magnification ratio of the second scale according to formula (3): ,in , obtained by the detector pixel size (0.1mm) and the number of pixels of the second scale (72.6), , is a known quantity, which can be obtained by consulting the instruction manual of the flat-plate aperture image quality meter;

[0075] The distance between the ray emission position and the detector imaging plane is calculated according to formula (4): =415.56mm, where , obtained by measuring the distance between the first ruler and the second ruler, , , , ;

[0076] Calculate the distance from the defect to the first scale and the second scale according to formula (5) (6) 、 They are

[0077] =49.54mm;

[0078] =38.14mm.

[0079] The actual value of the preset defect to scale 2 is 38.44 mm. The defect depth value obtained by this method is only 0.3 mm different from the actual value, which shows that this method has good accuracy.

[0080] Conventional calculation methods can only measure Figure 2 Distance from the center ray tube to the detector surface f * (measured as 400mm in this embodiment), the distance from the ray emission position to the detector imaging plane cannot be calculated f (The calculated value is 415mm). The difference of 15mm between the two will increase the error in defect depth positioning.

[0081] From the final numerical comparison, it can be seen that compared with the conventional calculation method, the accuracy of the method of the present invention is improved by one order of magnitude.

Claims

1. A method for locating the depth of defects in radiographic inspection; characterized in that: The method comprises the following steps: Step S1: measuring the size of the defect in the workpiece; Step S2: placing a first ruler and a second ruler on the source-side surface and detector-side surface of the defect, respectively, measuring the distance between the first ruler and the second ruler, and capturing an image. The images of the defect, the first ruler, and the second ruler in the image should be as close as possible but not overlap. Step S3: Measure the image sizes of the first scale, the second scale, and the defect, and calculate the magnification ratio between the image size and the actual size. The calculation formula for the magnification ratio between the first scale and the second scale is: in, is the magnification ratio of the first scale, is the distance from the ray emission position to the actual imaging plane of the detector, is the distance from the ray emission position to the first scale, is the size of the image of the first ruler, is the actual size of the first ruler, is the distance between the first scale and the second scale, is the size of the image of the second ruler, is the actual size of the second ruler; Step S4: Calculate the distance between the ray source and the detector imaging plane using the magnification ratio of the first scale and the second scale, and calculate the distance from the defect to the first scale and the second scale using the distance and the magnification ratio of the defect. The distance calculation formula between the ray emission position and the detector imaging plane is: ； The calculation formulas for the distance from the defect to the first scale and the second scale are: in, is the distance from the defect to the first scale, is the size of the defect image in the image obtained in step S2, is the defect size measured in step S1.

2. The method according to claim 1, wherein: In step S1, the defect in the workpiece is measured by moving it. Specifically, the defect is first moved to the detector imaging area to capture the result image, and the number of pixels of the defect image is counted in the result image. Secondly, the defect is moved. When the difference between the number of pixels moved by the defect and the number of pixels of the defect itself is the smallest, the movement distance of the defect is recorded at this time. The pixel size is calculated based on the movement distance of the defect and the number of moved pixels, and then the actual size of the defect is obtained.

3. The method according to claim 1, wherein: In step S1, a ruler is used to measure defects in the workpiece.

4. The method according to claim 2, wherein: In step S1, the actual size of the defect is calculated using the following formula: in, is the actual size of the defect, is the moving distance of the defect, is the number of moving pixels of the defect, is the number of pixels of the defect in the center area of ​​the detector.

5. The method according to claim 1, wherein: In step S2, the selection of scale material and size is as follows: The first and second scales are made of the same material as the workpiece; The difference between the actual size of the first ruler and the second ruler and the defect size measured in step 1 is as small as possible; as small as possible means that: among the series of rulers with gradient sizes, the two rulers closest to the defect size measured in step S1 should be selected.

6. The method according to claim 5, characterized in that: The first and second scales use a flat-plate hole-type image quality meter.

7. A device for detecting the depth of a defect detected by radiography, using the method according to claim 1, characterized in that: It includes ray excitation module, workpiece clamping module, imaging module, motion control module, data processing module and display module; The ray excitation module is used to generate rays; the workpiece clamping module is used to clamp the inspected workpiece; the imaging module is used to receive ray radiation signals and generate images; the motion control module is used to control the movement of the ray excitation module, imaging module and workpiece clamping module, and display the movement distance; the data processing module is used to calculate and process the various data obtained to obtain calculation results including defect depth; the display module is used to control the parameters of the ray excitation module and imaging module, and display the imaging results and calculation results; The imaging module is a digital detector array or film.

Images