Method for measuring defect depth by using digital imaging detection image quality indicator

Abstract

The invention belongs to the technical field of nondestructive testing, and discloses a method for measuring defect depth by using a digital imaging detection image quality indicator, which comprises the following steps: S1, preparing; s2, determining a detection method; s3, starting the X-ray; s4, performing transillumination; s5, image quality and evaluation; s6, verification is carried out; and S7, evaluating the defect depth. Defect depth quantification can be conveniently and quickly realized, so that the defect detection capability is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of nondestructive testing, and particularly relates to a method for measuring the depth of a defect by using a digital imaging detection image quality indicator. Background Art

[0002] During the use of missiles, potential safety hazards may be caused by defects in the raw materials of components. Therefore, nondestructive testing of missiles is extremely important. Missile components are generally manufactured by processes such as casting, forging, stamping, powder metallurgy, and welding, and the processes are complex. To ensure their surface and internal quality, nondestructive testing procedures must be arranged at different manufacturing process stages of the components. In recent years, with the development of informatization and intelligent technologies, digital ray detection technology will tend to be automated, lean, and fast. Through digital means, a large number of films are electronically archived, providing a large amount of data basis for defect detection. Since visual information has the characteristics of being convenient, intuitive, having a large amount of information, and being easy to process, it has a broad application space in defect detection using digital ray detection technology. However, when evaluating digital ray films, it is impossible to achieve precise and efficient detection of the depth of defects.

[0003] Therefore, there is an urgent need to develop a brand-new method for measuring the depth of defects to overcome the problems existing in the prior art. Summary of the Invention

[0004] The technical problem to be solved by the present invention is the problem that digital ray detection cannot achieve precise and efficient positioning of the depth of defects.

[0005] To solve the above technical problem, the specific technical solution of the present invention is as follows:

[0006] A method for measuring the depth of a defect by using a digital imaging detection image quality indicator, comprising the following steps:

[0007] S1. Preparation: Train the machine and debug the performance of the DR system;

[0008] S2. Determine the detection method: Determine the irradiation method, imaging geometric parameters, irradiation parameters, and markings, and complete the layout;

[0009] S3. Start the X-ray: Set the irradiation parameters, X-ray energy, and exposure amount in the DR control software, and start the X-ray;

[0010] S4. Irradiate: The X-ray irradiates the specimen standard, the imaging plate records the attenuated ray photons, the detector converts the ray intensity into visible light, and finally the visible light is digitally processed and transmitted to the computer to form an image for display;

[0011] S5. Image quality and evaluation: The image sensitivity is measured by a linear image quality indicator, and the image resolution is measured by a double-linear image quality indicator. After recording the corresponding image grayscales at the upper, middle, and lower parts of each wire of the linear image quality indicator and taking the average value, with the diameter of the linear image quality indicator as the X-axis and the image grayscale corresponding to the diameter of the linear image quality indicator as the Y-axis, the corresponding function Y(h) is fitted by the least squares method;

[0012] S6. Verification: Taking the known thickness of the specimen standard as the standard value, recording the grayscale value at the defect-free part of the specimen, substituting it into the Y(h) fitting function, and performing error confirmation;

[0013] S7. Evaluating the defect depth: Recording 3 grayscale values at the edge position of the defect and 3 grayscale values at the middle position of the defect. After averaging the grayscale values, substituting them into the fitting formula Y(h) to obtain the defect depth h. Finally, complete the quantification, qualification, and location of the defect.

[0014] Among them, the defect quantification includes depth measurement and geometric dimensions. After the image quality meets the requirements, the quality assessment of the test specimen can be carried out. Observed in a soft environment, the display screen should be clean and have no obvious light reflection. Observe the negative film through negative display.

[0015] Among them, for geometric dimension measurement, the characteristics of the test piece are compared with a known and observable dimension, and the entire dimension is within the detection image range. The measurement is carried out by reading the number of pixels on the characteristic length. The final calibration value is obtained by averaging not less than 3 calibrations. The steps are as follows:

[0016] (1) Collect the X-ray digital image of the standard specimen to calibrate its geometric dimensions. The calculation formula for the geometric scale factor: α = L / N i , where α is the geometric scale factor, L is the specimen size, and N i is the number of pixels obtained by the software measuring the size image of the standard specimen;

[0017] (2) The system measures the geometric dimensions of the defect: A = α × N s , where A is the geometric dimension, α is the geometric scale factor, and N s is the number of pixels obtained by the software measuring the defect image size.

[0018] Among them, the metal wire of the linear image quality indicator should be the same as the material of the test piece.

[0019] Among them, the recorded grayscale values of the linear image quality indicator are not less than 3.

[0020] The present invention has the following advantages: It can conveniently and quickly realize the quantification of the defect depth, thereby improving the defect detection ability. Description of the Drawings

[0021] Figure 1Flowchart of the method for measuring the depth of defects by the digital imaging detection image quality meter of the present invention. Specific embodiments

[0022] To better understand the purpose, structure and function of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0023] As Figure 1 shown, a method for measuring the depth of defects by a digital imaging detection image quality meter of the present invention specifically includes the following steps:

[0024] S1 Preparation: Train the machine and debug the performance of the DR system;

[0025] S2 Determine the detection method: Penetration method, imaging geometric parameters, penetration parameters, markings, and complete the layout;

[0026] S3 Start the X-ray: The DR control software sets the penetration parameters, X-ray energy, and exposure, and starts the X-ray;

[0027] S4 Penetration: The X-ray penetrates the specimen standard, the imaging plate records the attenuated ray photons, the detector converts the ray intensity into visible light, and finally the visible light is digitally processed and transmitted to the computer to form an image display;

[0028] S5 Image quality and evaluation: Adjust the control software parameters; The linear image quality meter measures the image sensitivity, and the double linear image quality meter measures the image resolution; Record the corresponding image gray levels at the upper, middle and lower parts of each wire of the linear image quality meter, and then take the average value. Take the diameter of the linear image quality meter as the X-axis and the corresponding image gray level of the diameter of the linear image quality meter as the Y-axis, and fit the corresponding function Y(h) by the least square method;

[0029] S6 Verification: Taking the known thickness of the specimen standard as the standard value, record the gray level value at the defect-free part of the specimen, substitute it into the Y(h) fitting function, and confirm the error;

[0030] S7 Evaluate the defect depth: Record 3 gray level values at the edge position of the defect and 3 gray level values at the middle position of the defect. After averaging the gray level values, substitute them into the fitting formula Y(h) to obtain the defect depth h, and finally complete the defect quantification, qualification and location.

[0031] Preferably, the defect quantification includes depth measurement and geometric dimensions. After the image quality meets the requirements, the quality assessment of the specimen to be tested can be carried out. Observe in a soft environment. The display screen should be clean and there should be no obvious light reflection. Observe the negative film through negative display.

[0032] Preferably, for geometric dimension measurement, the feature of the test piece to be tested is compared with a known and observable dimension that is entirely within the range of the detection image. The measurement is carried out by reading out the number of pixels along the length of the feature. The final calibration value is obtained by averaging not less than 3 calibrations. The steps are as follows:

[0033] (1) Collect the X-ray digital image of the standard specimen to calibrate its geometric dimensions. The calculation formula for the geometric scale factor: α = L / N i , where α is the geometric scale factor (mm / pixel), L is the specimen size (mm), and N i is the number of pixels (pixel) obtained by the software measuring the size image of the standard specimen;

[0034] (2) The system measures the geometric dimensions of the defect: A = α × N s , where A is the geometric dimension (mm), α is the geometric scale factor (mm / pixel), and N s is the number of pixels (pixel) obtained by the software measuring the size image of the defect.

[0035] Preferably, the size of the specimen standard is calibrated by a professional metrology department.

[0036] Preferably, the wire of the linear image quality indicator should be the same as or similar to the material of the test piece to be tested.

[0037] Preferably, the recorded gray values of the linear image quality indicator should not be less than 3 to ensure the uniformity and accuracy of the gray values.

[0038] Preferably, there are 2 types of specimens. One is an artificial standard specimen, and the other is a natural defect specimen. First, use the artificial standard specimen to fit the function, then verify it, and finally use the natural defect specimen to verify the effectiveness of the design method.

[0039] Preferably, the X-ray vertically (or aligns with) penetrates the test piece to be tested and reaches the effective area of the detector.

[0040] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, for those skilled in the art, without departing from the principle of the present invention, several modifications and improvements can still be made, and these should also be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for a digital imaging detection image quality meter to measure the depth of a defect, characterized in that, It includes the following steps: S1. Preparation: Train the machine and debug the performance of the DR system; S2. Determine the detection method: Determine the radiographic method, imaging geometric parameters, radiographic parameters, and markings, and complete the layout; S3. Start the X-ray: The DR control software sets the radiographic parameters, X-ray energy, and exposure, and starts the X-ray; S4. Radiograph: The X-ray radiographs the specimen standard piece, the imaging plate records the attenuated ray photons, the detector converts the ray intensity into visible light, and finally the visible light is digitally processed and transmitted to the computer to form an image display; S5. Image quality and evaluation: The linear image quality indicator measures the image sensitivity, the double linear image quality indicator measures the image resolution, records the average value of the image gray levels corresponding to the upper, middle, and lower parts of each wire of the linear image quality indicator, takes the diameter of the linear image quality indicator as the X-axis, and the image gray level corresponding to the diameter of the linear image quality indicator as the Y-axis, and fits the corresponding function Y(h) by the least squares method; S6. Verification: Take the known thickness of the specimen standard piece as the standard value, record the gray level value at the defect-free part of the specimen, substitute it into the Y(h) fitting function, and confirm the error; S7. Evaluate the defect depth: Record 3 gray level values at the edge position of the defect and 3 gray level values at the middle position of the defect. After averaging the gray level values, substitute them into the fitting formula Y(h) to obtain the defect depth h. Finally, complete the defect quantification, qualification, and localization.

2. The method for measuring the depth of a defect by the digital imaging detection image quality meter according to claim 1, characterized in that, The defect quantification includes depth measurement and geometric dimension. After the image quality meets the requirements, the quality evaluation of the specimen to be tested can be carried out. Observe in a soft environment. The display screen should be clean and have no obvious light reflection. Observe the negative film through negative display.

3. The method for measuring the depth of a defect by using the digital imaging detection image quality meter according to claim 2, wherein The geometric dimension measurement compares the characteristics of the specimen to be tested with a known and observable dimension, and the whole of this dimension is within the detection image range. The measurement is carried out by reading the number of pixels on the characteristic length. The final calibration value is obtained by averaging not less than 3 calibrations. The steps are as follows: (1) Calibrate the geometric dimensions by collecting X-ray digital images of standard specimens. The calculation formula for the geometric scale factor: α = L / N i , where α is the geometric scale factor, L is the specimen size, and N i is the number of pixels obtained by the software measuring the size image of the standard sample; (2) The system measures the geometric size of the defect: A = α × N s , where A is the geometric size, α is the geometric scale factor, and N s is the number of pixels obtained by the software measuring the size of the defect image.

4. The method for measuring the depth of a defect by the digital imaging detection image quality meter according to claim 3, characterized in that, The metal wire of the linear image quality indicator should be the same as the material of the specimen to be tested.

5. The method for measuring the depth of a defect by the digital imaging detection image quality meter according to claim 4, wherein, The recorded gray level values of the linear image quality indicator are not less than 3.

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