Digital imaging detection method and system for rocket box bottom flange weld joint

Abstract

The invention provides a rocket box bottom flange welding seam digital imaging detection method and system, and the method comprises the steps: arranging a ray source at the center of the inner side of a flange welding seam, arranging an imaging plate in the circumferential direction of the outer side of the flange welding seam, and pasting an image quality indicator on the surface of one side, close to the ray source, of the flange welding seam, the ray source and the imaging plate are connected with the imaging control system through cables; relevant parameters are set through an imaging control system; and transilluminating, and enabling the image processing and display system to analyze the obtained negative film to obtain a detection result. Digital ray imaging detection is carried out by adopting a central transillumination method according to the structure of the box bottom flange welding seam, one-time transillumination detection of the box bottom flange welding seam can be realized through the circumferential transillumination line source anode target and the flexible digital ray imaging plate, the working hours of ray detection are shortened, meanwhile, the loss of a negative film is reduced, the detection efficiency is improved, and the detection cost is reduced. The method can be suitable for digital radiographic inspection of tank bottom flange weld joints with various diameters, and has high applicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of nondestructive testing, and specifically, relates to a digital imaging detection method and system for a rocket tank bottom flange weld, and in particular, to a 3800 tank bottom flange digital radiographic imaging detection method. Background Art

[0002] Nondestructive testing of the flange welds of rocket fuel tanks is crucial to ensure the safety of rocket service. At present, the flange welds of the 3800 rocket tank bottom are mainly filmed using a directional radiograph, which uses a directional single-wall single-shadow radiography method. This method is difficult to film. Depending on the length of a radiography, 6-8 exposures are required to complete the full inspection. One flange takes about 2 hours of work. Based on 5 flanges on one tank bottom, a total of 10 hours of work is required, and the radiography efficiency is low. In addition, due to the thickness difference between the flange and the parent material, double films are required for filming, which increases the amount of film consumables.

[0003] The existing technologies all have the above problems. The patent document "Rocket Tank Bottom Weld X-ray Digital Imaging Detection System and Detection Method" (CN105352982A) discloses that two robots and a 2-axis positioner are coordinated and controlled to achieve X-ray digital imaging detection of the ellipsoid bottom weld of the launch vehicle tank in conjunction with a digital detector, an X-ray machine, and a master control unit to improve the detection efficiency. However, it requires multiple imaging of the flange weld, and cannot solve the problem well under the premise of one-time imaging of the flange weld, and the consumption is still high.

[0004] Therefore, there is an urgent need for a nondestructive testing method for the flange weld of a rocket fuel tank with higher penetration efficiency, less consumption and higher adaptability. Summary of the invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a digital imaging detection method and system for the weld of the bottom flange of a rocket box.

[0006] A digital imaging detection method for a rocket tank bottom flange weld provided by the present invention comprises: Step S1: According to the X-ray center transillumination method, a radiation detection system composed of a micro-focus circumferential transillumination radiation source anode target and an imaging plate is arranged and connected, the radiation source is arranged at the inner center of the flange weld, the imaging plate is arranged at the outer circumference of the flange weld, the image quality meter is attached to the surface of the flange weld close to the radiation source, the filament of the image quality meter is placed on the outer surface, and forms an angle of 5° with the imaging plate, and the radiation source and the imaging plate are connected to the imaging control system through cables; According to the material and thickness of the flange weld, a micro-focus anode target with a size of 0.4 mm was selected as the radiation source, and a flexible and reusable digital radiographic imaging plate with a pixel size of 50 μm was selected as the imaging plate; According to the size of the radiation source and the pixel size of the imaging plate, the optimal magnification Mopt=1+(U i / d) 3 / 2 , adjust the relative positions of the imaging plate, the radiation source and the weld; Among them, U i Inherent unclearness of representation; d represents the size of the ray source; Lead characters are arranged near the image quality meter for transillumination marking. The lead characters are placed on the flange weld surface on the radiation source side, at a position greater than or equal to 10 mm away from the weld edge; Step S2: controlling the activation of the radiation source, the current of the X-ray tube and the exposure time through the imaging control system, and setting the relevant parameters including the tube current, tube voltage, focal length, sensitivity and exposure amount according to the thickness, structure and material of the flange weld; The focal length is the distance between the radiation source and the flange weld; Step S3: Transillumination, allowing the image processing and display system to analyze the obtained film to obtain the detection result.

[0007] Preferably, the step S2 comprises: Step S2.1: Setting the focus to 0.4 mm through the imaging control system and selecting the exposure mode to be continuous exposure; Step S2.2: Setting the x-ray tube current and exposure time through the imaging control system.

[0008] The tube current, tube voltage and exposure amount among the related parameters are determined according to the thickness and focal length of the flange weld.

[0009] The step S3 comprises: Step S3.1: Turn on the radiation source, perform digital radiographic imaging on the box bottom flange weld, and form a digital radiographic image of the box bottom flange weld; Step S3.2: Acquire a digital radiographic image using an image processing and display system; Step S3.3: Perform image enhancement processing on the digital radiographic image, and calculate the image unsharpness, image signal-to-noise ratio, and image sensitivity to ensure that the indicators meet the requirements of GB / T 3323.2-2018 national standard; Step S3.4: Qualitatively and quantitatively analyze the defects in the digital radiographic image through the image processing and display system.

[0010] Preferably, the step S3.3 comprises: Step S3.3.1: Perform image enhancement processing on the digital radiographic image, with the line width no greater than 11 pixels and the noise adjusted to 200. Test the unsharpness of the digital radiographic image through the image processing and display system, and measure the horizontal and vertical unsharpness of the image. ; Among them, U g Indicates geometric unclearness; represents the basic spatial resolution; Mopt stands for optimal magnification.

[0011] Step S3.3.2: Determine the normalized signal-to-noise ratio according to 6.1 of ISO 16371-1. Select a 20×55 pixel area in the weld heat affected zone of the digital radiographic image where the base metal thickness and image grayscale are uniform. Calculate the image normalized signal-to-noise ratio SNRN=SNR using the image processing and display system. measured ×88.6 / SR b ; Among them, SNR measured represents the signal-to-noise ratio of the assay; SR b Indicates the basic spatial resolution measured by the image quality meter close to the imaging plate.

[0012] Step S3.3.3: In the area with uniform grayscale, measure the image sensitivity of the image using an image quality meter to ensure that the image sensitivity index meets the standard requirements.

[0013] According to the present invention, a digital imaging detection system for a rocket box bottom flange weld is provided, which is applied to the digital imaging detection method for the rocket box bottom flange weld, and includes: a radiation source, an imaging board, an imaging control system, an image processing and display system, an image quality meter and lead type.

[0014] Arrange the radiation source, imaging plate, image quality meter and lead type and connect the equipment; Imaging control system sets relevant parameters; Through-illumination allows the image processing and display system to analyze the obtained film to obtain the test results.

[0015] Preferably, according to the X-ray central transillumination method, a radiation detection system composed of a micro-focus circumferential transillumination radiation source anode target and a flexible and repeatedly usable digital radiographic imaging plate is arranged and connected for transillumination, including: According to the material and thickness of the flange weld, a micro-focus anode target is selected as the radiation source, and a flexible and reusable digital radiographic imaging plate is selected as the imaging plate; The radiation source is arranged at the inner center of the flange weld, and the imaging plate is arranged close to the outer circumference of the flange weld; Calculate the best magnification according to the size of the radiation source and the pixel size of the imaging plate, and adjust the relative positions of the imaging plate, radiation source and weld; The single-wire image quality meter and the double-wire image quality meter are pasted on the surface of the flange weld close to the radiation source; Lead type is arranged near the image quality meter for transillumination marking, and the lead type is placed on the flange weld surface on the radiation source side.

[0016] Select tube current, tube voltage, focal length, sensitivity and exposure according to the thickness, structure and material of the flange weld; The focal length is the distance between the radiation source and the flange weld.

[0017] Preferably, the size of the microfocus anode target is 0.4 mm.

[0018] The pixel size of the imaging plate is 50 μm.

[0019] The ray source and the imaging plate are connected to the imaging control system via cables.

[0020] The imaging control system is used to control the activation of the ray source, the current size of the X-ray tube and the exposure time.

[0021] The optimal magnification Mopt=1+(U i / d) 3 / 2 , used to adjust the transillumination arrangement; Among them, U i Inherent unclearness of representation; d represents the size of the radiation source.

[0022] The filaments of the double-filament image quality meter are placed on the outer surface, and the filaments of the image quality meter and the imaging plate form an angle of 5°.

[0023] The lead type is placed at a position greater than or equal to 10 mm away from the edge of the weld.

[0024] Preferably, the imaging control system sets relevant parameters including: The imaging control system sets the focus to 0.4 mm and the exposure mode to continuous exposure; The imaging control system sets the x-ray tube current and exposure time.

[0025] The tube current, tube voltage and exposure amount among the related parameters are determined according to the thickness and focal length of the flange weld.

[0026] The transillumination is to turn on the radiation source and perform digital radiographic transillumination on the box bottom flange weld to form a digital radiographic image of the box bottom flange weld.

[0027] The image processing and display system obtains the digital radiographic image of the box bottom flange weld, performs image enhancement processing, and calculates the image unsharpness, image signal-to-noise ratio, and image sensitivity to ensure that the indicators comply with the national standard GB / T 3323.2-2018; The image processing and display system conducts qualitative and quantitative analysis of defects in digital radiographic images.

[0028] Preferably, the image processing and display system performs image enhancement processing on the digital radiographic image, the line width is not greater than 11 pixels, the noise is adjusted to 200, the digital radiographic image is tested for unsharpness, and the horizontal and vertical unsharpness of the image is measured. ; Among them, U g Indicates geometric unclearness; represents the basic spatial resolution; Mopt stands for optimal magnification.

[0029] According to 6.1 of ISO 16371-1, the normalized signal-to-noise ratio is determined. In the heat-affected zone of the weld in the digital radiographic image, a 20×55 pixel area is selected where the base metal thickness and image grayscale are uniform. The image normalized signal-to-noise ratio SNRN=SNR is calculated using the image processing and display system. measured ×88.6 / SR b ; Among them, SNR measured represents the signal-to-noise ratio of the assay; SR b Indicates the basic spatial resolution measured by a two-wire image quality meter close to the imaging plate.

[0030] The image quality meter measures the image sensitivity of an image in an area with uniform grayscale to ensure that the image sensitivity index meets the standard requirements.

[0031] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention can realize one-time radiographic detection of the box bottom flange weld by using the circumferential radiographic source anode target and the flexible digital radiographic imaging plate, thereby shortening the working time of radiographic detection and reducing the loss of film.

[0032] 2. The present invention can be applied to digital radiographic detection of flange welds at the bottom of tanks of various diameters and has high applicability.

[0033] 3. The present invention adopts the central transillumination method to perform digital radiographic detection according to the structure of the box bottom flange weld, which solves the problems of long time consumption and large film consumption of traditional X-ray multiple transilluminations and improves the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 Schematic diagram of the digital imaging detection system for the rocket tank bottom flange weld.

[0035] The figure shows: 1. Radiation source; 2. Flange weld; 3. Imaging plate; 4. Box bottom; 5. Imaging control system; 6. Image processing and display system; 7. Image quality meter; 8. Lead type. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0037] A digital imaging detection method for a rocket tank bottom flange weld provided by the present invention comprises: Step S1: Transillumination arrangement: according to the X-ray center transillumination method, a radiation detection system composed of a micro-focus circumferential transillumination radiation source anode target and a flexible and reusable digital radiographic imaging plate is arranged and connected.

[0038] Specifically, it includes: Step S1.1: Select a micro-focus anode target as a radiation source according to the material and thickness of the flange weld, place the micro-focus anode target at the inner center of the flange weld, and select a flexible and reusable imaging plate; The size of the micro-focus anode target is 0.4 mm; The pixel size of the imaging plate is 50 μm; The micro-focus anode target ray source and the flexible and reusable imaging plate are connected to the imaging control system via cables; The imaging control system is used to control the activation of the micro-focus anode target ray source, the current size of the X-ray tube and the exposure time, thereby controlling the exposure amount.

[0039] The detection system composed of an anode target and a flexible digital radiographic imaging plate was improved from the original multiple exposures with the radiation source outside and the film inside to exposure with the source inside the center, achieving one-time imaging of the flange welds on the bottom of 3,800 boxes, achieving the effect of reducing the number of exposures and saving film.

[0040] Step S1.2: The radiation source is arranged at the center of the flange weld, and the imaging plate is arranged close to the outer circumference of the flange weld; Step S1.3: Calculate the optimal magnification according to the size of the radiation source and the pixel size of the imaging plate, and further adjust the relative positions of the flexible imaging plate, the radiation source and the weld; The optimal magnification Mopt=1+(U i / d) 3 / 2 ; Among them, U i Inherent unclearness of representation; d represents the size of the microfocus anode target radiation source.

[0041] The optimal magnification is used to adjust the transillumination arrangement to obtain the best image resolution; Step S1.4: Paste the single-wire image quality meter and the dual-wire image quality meter on the surface of the flange weld close to the radiation source.

[0042] The filaments of the double-wire image quality meter are placed on the outside, and the metal wires of the image quality meter and the imaging plate form an angle of 5°; Step S1.5: Lead characters are arranged near the image quality meter for transillumination marking. The lead characters are placed on the flange weld surface on the radiation source side and at least 10 mm away from the weld edge.

[0043] Step S2: Preparation before transillumination, selecting appropriate tube current, tube voltage, focal length, sensitivity and exposure according to the thickness, structure and material of the flange weld; The tube current, tube voltage and exposure are determined according to the thickness and focal length of the flange weld; The focal length is the distance between the radiation source and the flange weld.

[0044] Specifically, it includes: Step S2.1: Setting the focus to 0.4 mm through the imaging control system and selecting the exposure mode to be continuous exposure; Step S2.2: setting the x-ray tube current and exposure time through the imaging control system; Step S3: transillumination and film analysis, specifically including: Step S3.1: Turn on the micro-focus anode target radiation source, perform digital radiographic imaging on the box bottom flange weld, and form a digital radiographic image of the box bottom flange weld; Step S3.2: Acquire a digital radiographic image using an image processing and display system; Step S3.3: After the transillumination is completed, image enhancement processing is performed, and image unsharpness, image signal-to-noise ratio, and image sensitivity are calculated to ensure that the above indicators meet the requirements of GB / T 3323.2-2018 national standard; The step S3.3 specifically includes: Step S3.3.1: Perform image enhancement processing, test the image unsharpness through the image processing and display system, ensure that the line width is no more than 11 pixels, adjust the noise to 200, measure the horizontal and vertical unsharpness of the image, and the image unsharpness ; Among them, U g Indicates geometric unclearness; Indicates the basic spatial resolution.

[0045] Step S3.3.2: Select an area with uniform grayscale and determine the normalized signal-to-noise ratio according to 6.1 of ISO 16371-1. Select a 20×55 pixel area in the weld heat affected zone with uniform base metal thickness and image grayscale on the acquired image. Use the image processing and display system to calculate the image normalized signal-to-noise ratio SNRN=SNR in this area. measured ×88.6 / SR b ; Among them, SNR measured represents the signal-to-noise ratio of the measurement; SR b Indicates the basic spatial resolution measured by a two-wire image quality meter close to the imaging plate.

[0046] Step S3.3.3: In the area with uniform grayscale within the image inspection range, measure the image sensitivity of the image using an image quality meter to ensure that the image sensitivity index meets the standard requirements.

[0047] Step S3.4: Qualitatively and quantitatively analyze the defects in the image through the image processing and display system.

[0048] According to the thickness and structure of the box bottom flange weld of the 3800 rocket, the center transillumination method is used to transilluminate the box bottom flange weld. Only one transillumination is required to achieve digital radiographic detection of the entire flange weld, which shortens the working time of radiographic detection and reduces the loss of film.

[0049] According to the present invention, a digital imaging detection system for a rocket tank bottom flange weld is applied to the digital imaging detection method for a rocket tank bottom flange weld. Figure 1 For example, it includes: radiation source, imaging board, imaging control system, image processing and display system, image quality meter and lead type.

[0050] Arrange the radiation source, imaging plate, image quality meter and lead type and connect the equipment; Imaging control system sets relevant parameters; Through-illumination allows the image processing and display system to analyze the obtained film to obtain the test results.

[0051] In more preferred embodiments, according to the X-ray central transillumination method, a radiation detection system composed of a micro-focus circumferential transillumination radiation source anode target and a flexible and repeatedly usable digital radiographic imaging plate is arranged and connected for transillumination, including: According to the material and thickness of the flange weld, a micro-focus anode target is selected as the radiation source, and a flexible and reusable digital radiographic imaging plate is selected as the imaging plate; The radiation source is arranged at the inner center of the flange weld, and the imaging plate is arranged close to the outer circumference of the flange weld; Calculate the best magnification according to the size of the radiation source and the pixel size of the imaging plate, and adjust the relative positions of the imaging plate, radiation source and weld; The single-wire image quality meter and the double-wire image quality meter are pasted on the surface of the flange weld close to the radiation source; Lead type is arranged near the image quality meter for transillumination marking, and the lead type is placed on the flange weld surface on the radiation source side.

[0052] Select tube current, tube voltage, focal length, sensitivity and exposure according to the thickness, structure and material of the flange weld; The focal length is the distance between the radiation source and the flange weld.

[0053] In more preferred examples, the size of the microfocus anode target is 0.4 mm.

[0054] The pixel size of the imaging plate is 50 μm.

[0055] The ray source and the imaging plate are connected to the imaging control system via cables.

[0056] The imaging control system is used to control the activation of the ray source, the current size of the X-ray tube and the exposure time.

[0057] The optimal magnification Mopt=1+(U i / d) 3 / 2 , used to adjust the transillumination arrangement; Among them, U i Inherent unclearness of representation; d represents the size of the radiation source.

[0058] The filaments of the double-filament image quality meter are placed on the outer surface, and the filaments of the image quality meter and the imaging plate form an angle of 5°.

[0059] The lead type is placed at a position greater than or equal to 10 mm away from the edge of the weld.

[0060] In more preferred embodiments, the imaging control system sets relevant parameters including: The imaging control system sets the focus to 0.4 mm and the exposure mode to continuous exposure; The imaging control system sets the x-ray tube current and exposure time.

[0061] The tube current, tube voltage and exposure amount among the related parameters are determined according to the thickness and focal length of the flange weld.

[0062] The transillumination is to turn on the radiation source and perform digital radiographic transillumination on the box bottom flange weld to form a digital radiographic image of the box bottom flange weld.

[0063] The image processing and display system obtains the digital radiographic image of the box bottom flange weld, performs image enhancement processing, and calculates the image unsharpness, image signal-to-noise ratio, and image sensitivity to ensure that the indicators comply with the national standard GB / T 3323.2-2018; The image processing and display system conducts qualitative and quantitative analysis of defects in digital radiographic images.

[0064] In more preferred embodiments, the image processing and display system performs image enhancement processing on the digital radiographic image, the line width is no more than 11 pixels, the noise is adjusted to 200, the digital radiographic image is tested for unsharpness, and the horizontal and vertical unsharpness of the image is measured. ; Among them, U g Indicates geometric unclearness; represents the basic spatial resolution; Mopt stands for optimal magnification.

[0065] According to 6.1 of ISO 16371-1, the normalized signal-to-noise ratio is determined. In the heat-affected zone of the weld in the digital radiographic image, a 20×55 pixel area is selected where the base metal thickness and image grayscale are uniform. The image normalized signal-to-noise ratio SNRN=SNR is calculated using the image processing and display system. measured ×88.6 / SR b ; Among them, SNR measured represents the signal-to-noise ratio of the assay; SR b Indicates the basic spatial resolution measured by a two-wire image quality meter close to the imaging plate.

[0066] The image quality meter measures the image sensitivity of an image in an area with uniform grayscale to ensure that the image sensitivity index meets the standard requirements.

[0067] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0068] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A digital imaging detection method for a rocket tank bottom flange weld, characterized in that: include: Step S1: According to the X-ray center transillumination method, a radiation detection system composed of a micro-focus circumferential transillumination radiation source anode target and an imaging plate is arranged and connected, the radiation source is arranged at the inner center of the flange weld, the imaging plate is arranged at the outer circumference of the flange weld, the image quality meter is attached to the surface of the flange weld close to the radiation source, the filament of the image quality meter is placed on the outer surface, and forms an angle of 5° with the imaging plate, and the radiation source and the imaging plate are connected to the imaging control system through cables; According to the material and thickness of the flange weld, a micro-focus anode target with a size of 0.4 mm was selected as the radiation source, and a flexible and reusable digital radiographic imaging plate with a pixel size of 50 μm was selected as the imaging plate; According to the size of the radiation source and the pixel size of the imaging plate, the optimal magnification Mopt=1+(U i / d) 3 / 2 , adjust the relative positions of the imaging plate, the radiation source and the weld; Among them, U i Inherent unclearness of representation; d represents the size of the ray source; Lead characters are arranged near the image quality meter for transillumination marking. The lead characters are placed on the flange weld surface on the radiation source side, at a position greater than or equal to 10 mm away from the weld edge; Step S2: controlling the activation of the radiation source, the current of the X-ray tube and the exposure time through the imaging control system, and setting the relevant parameters including the tube current, tube voltage, focal length, sensitivity and exposure amount according to the thickness, structure and material of the flange weld; The focal length is the distance between the radiation source and the flange weld; Step S3: Transillumination, allowing the image processing and display system to analyze the obtained film to obtain the detection result.

2. The digital imaging detection method for the rocket box bottom flange weld according to claim 1 is characterized in that: The step S2 comprises: Step S2.1: Setting the focus to 0.4 mm through the imaging control system and selecting the exposure mode to be continuous exposure; Step S2.2: setting the x-ray tube current and exposure time through the imaging control system; The tube current, tube voltage and exposure amount among the related parameters are determined according to the thickness and focal length of the flange weld; The step S3 comprises: Step S3.1: Turn on the radiation source, perform digital radiographic imaging on the box bottom flange weld, and form a digital radiographic image of the box bottom flange weld; Step S3.2: Acquire a digital radiographic image using an image processing and display system; Step S3.3: Perform image enhancement processing on the digital radiographic image, and calculate the image unsharpness, image signal-to-noise ratio, and image sensitivity to ensure that the indicators meet the requirements of GB / T 3323.2-2018 national standard; Step S3.4: Qualitatively and quantitatively analyze the defects in the digital radiographic image through the image processing and display system.

3. The digital imaging detection method for the rocket box bottom flange weld according to claim 2 is characterized in that: The step S3.3 comprises: Step S3.3.1: Perform image enhancement processing on the digital radiographic image, with the line width no greater than 11 pixels and the noise adjusted to 200. Test the unsharpness of the digital radiographic image through the image processing and display system, and measure the horizontal and vertical unsharpness of the image. ; Among them, U g Indicates geometric unclearness; represents the basic spatial resolution; Mopt indicates optimal magnification; Step S3.3.2: Determine the normalized signal-to-noise ratio according to 6.1 of ISO 16371-1. Select a 20×55 pixel area in the weld heat affected zone of the digital radiographic image where the base metal thickness and image grayscale are uniform. Calculate the image normalized signal-to-noise ratio SNRN=SNR using the image processing and display system. measured ×88.6 / SR b ; Among them, SNR measured represents the signal-to-noise ratio of the assay; SR b It represents the basic spatial resolution measured by the image quality meter close to the imaging plate; Step S3.3.3: In the area with uniform grayscale, measure the image sensitivity of the image using an image quality meter to ensure that the image sensitivity index meets the standard requirements.

4. A digital imaging detection system for the weld of a rocket tank bottom flange, characterized in that: The digital imaging detection method for the rocket tank bottom flange weld as described in any one of claims 1 to 5 comprises: a ray source, an imaging plate, an imaging control system, an image processing and display system, an image quality meter and lead type; Arrange the radiation source, imaging plate, image quality meter and lead type and connect the equipment; Imaging control system sets relevant parameters; The film obtained by transillumination, image processing and display system analysis obtains the test results.

5. The digital imaging detection system for the rocket tank bottom flange weld according to claim 4 is characterized in that: According to the X-ray center transillumination method, a radiation detection system composed of a micro-focus circumferential transillumination radiation source anode target and a flexible and repeatedly usable digital radiographic imaging plate is arranged and connected for transillumination, including: According to the material and thickness of the flange weld, a micro-focus anode target is selected as the radiation source, and a flexible and reusable digital radiographic imaging plate is selected as the imaging plate; The radiation source is arranged at the inner center of the flange weld, and the imaging plate is arranged close to the outer circumference of the flange weld; Calculate the best magnification according to the size of the radiation source and the pixel size of the imaging plate, and adjust the relative positions of the imaging plate, radiation source and weld; The single-wire image quality meter and the double-wire image quality meter are pasted on the surface of the flange weld close to the radiation source; Lead characters are arranged near the image quality meter for transillumination marking, and the lead characters are placed on the flange weld surface on the radiation source side; Select tube current, tube voltage, focal length, sensitivity and exposure according to the thickness, structure and material of the flange weld; The focal length is the distance between the radiation source and the flange weld.

6. The digital imaging detection system for the rocket tank bottom flange weld according to claim 5 is characterized in that: The size of the micro-focus anode target is 0.4 mm; The pixel size of the imaging plate is 50 μm; The ray source and the imaging plate are connected to the imaging control system via cables; The imaging control system is used to control the activation of the ray source, the current size of the x-ray tube and the exposure time; The optimal magnification Mopt=1+(U i / d) 3 / 2 , used to adjust the transillumination arrangement; Among them, U i Inherent unclearness of representation; d represents the size of the ray source; The filaments of the double-filament image quality meter are placed on the outer surface, and the filaments of the image quality meter and the imaging plate form an angle of 5°; The lead type is placed at a position greater than or equal to 10 mm away from the edge of the weld.

7. The digital imaging detection system for the rocket tank bottom flange weld according to claim 4 is characterized in that: The imaging control system sets relevant parameters including: The imaging control system sets the focus to 0.4 mm and the exposure mode to continuous exposure; The imaging control system sets the x-ray tube current and exposure time; The tube current, tube voltage and exposure amount among the related parameters are determined according to the thickness and focal length of the flange weld; The transillumination is to turn on the radiation source and perform digital radiographic transillumination on the box bottom flange weld to form a digital radiographic image of the box bottom flange weld; The image processing and display system obtains the digital radiographic image of the box bottom flange weld, performs image enhancement processing, and calculates the image unsharpness, image signal-to-noise ratio, and image sensitivity to ensure that the indicators comply with the national standard GB / T 3323.2-2018; The image processing and display system conducts qualitative and quantitative analysis of defects in digital radiographic images.

8. The digital imaging detection system for the rocket tank bottom flange weld according to claim 7 is characterized in that: The image processing and display system performs image enhancement processing on the digital radiographic image, with the line width no greater than 11 pixels and the noise adjusted to 200. The image unsharpness is tested to measure the horizontal and vertical unsharpness of the image. ; Among them, U g Indicates geometric unclearness; represents the basic spatial resolution; Mopt indicates optimal magnification; According to 6.1 of ISO 16371-1, the normalized signal-to-noise ratio is determined. In the heat-affected zone of the weld in the digital radiographic image, a 20×55 pixel area is selected where the base metal thickness and image grayscale are uniform. The image normalized signal-to-noise ratio SNRN=SNR is calculated using the image processing and display system. measured ×88.6 / SR b ; Among them, SNR measured represents the signal-to-noise ratio of the assay; SR b It represents the basic spatial resolution measured by a two-wire image quality meter close to the imaging plate; The image quality meter measures the image sensitivity of an image in an area with uniform grayscale to ensure that the image sensitivity index meets the standard requirements.

Images