Method for detecting internal defects of tube bundle brazing for nuclear fusion

Abstract

The application discloses a kind of nuclear fusion with tube bundle brazing internal defect detection method, and the circumferential phased array probe is inserted into the internal of the tube bundle to be detected, and liquid coupling area is established by elastic water-retaining component;According to the curvature of tube bundle and brazing interface position, the delay time of array element excitation is determined, so that the ultrasonic wave forms focusing area at brazing interface;The circumferential direction electronic scanning is combined with the way of axial linear movement to complete the full-circle continuous detection of brazing interface, and the coupling state compensation is carried out based on the inner wall echo;Interface echo, outer boundary reflection echo and multiple reflection echo are comprehensively judged to determine the position, extension direction and coverage of brazing internal defect.The detection result is mapped to the two-dimensional detection matrix of circumferential and axial direction, so as to determine the position, extension direction and coverage of brazing internal defect.The application can improve the detection efficiency, coverage and defect identification accuracy.

Description

Technical Field

[0001] This invention relates to the field of non-destructive testing technology for nuclear fusion components, and in particular to a method for detecting internal defects in the brazing of tube bundles used in nuclear fusion. Background Technology

[0002] Key nuclear fusion components such as divertors in fusion reactors typically have multi-layered composite structures composed of tungsten, alloy materials, and tube bundles. These tube bundles are connected to external components via brazing. The quality of the brazed interface directly affects the structural integrity and operational reliability of the component; therefore, non-destructive testing is necessary to detect potential defects within the interface, such as debonding, porosity, and lack of fusion. Currently used X-ray inspection methods suffer from low imaging contrast for minute defects at thin-layer brazed interfaces due to the attenuation of X-ray energy by high-density materials like tungsten. Furthermore, X-ray inspection presents challenges, including high radiation protection requirements, difficulty in in-situ detection, and low efficiency in segmented inspection of long tube bundles.

[0003] While conventional ultrasonic testing avoids ionizing radiation issues, for tube bundles with small inner diameters and large lengths, it typically requires circumferential mechanical scanning of the probe along the inner wall of the bundle, which is prone to jamming, misalignment, and missed detections. Furthermore, the coupling fluid is easily lost during probe movement, causing echo signal fluctuations, and the curved surface structure of the bundle affects the incident and focusing effect of the acoustic beam, reducing the ability to identify minute brazing defects. Existing testing methods cannot simultaneously meet the requirements of full circumferential coverage, stable coupling, efficient continuous scanning, and accurate defect localization. Therefore, it is necessary to provide a method for detecting internal defects at the brazing interface of tube bundles used in nuclear fusion. Summary of the Invention

[0004] The technical problem to be solved by this invention is to improve the full-circumference coverage, coupling stability, micro-defect identification capability, and continuous scanning efficiency of the internal defect detection of the brazing interface of tube bundles used in nuclear fusion.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for detecting internal defects in the brazing of tube bundles used in nuclear fusion includes the following steps: S1. Obtain the inner diameter, wall thickness, and radial position parameters of the brazing interface relative to the inner wall of the tube bundle to be tested. Insert the circumferential phased array probe with multiple array elements distributed along the circumferential direction into the tube bundle to be tested and establish a liquid coupling region between the circumferential phased array probe and the inner wall. S2. Based on the inner diameter of the tube bundle to be tested, the thickness of the tube wall, the radial position of the brazing interface, and the spatial position of each array element, determine the ultrasonic propagation path from each array element to the brazing interface, and determine the excitation delay time of each array element based on the ultrasonic propagation path, so that the ultrasonic waves emitted by each array element enter the tube wall from the inner wall and form a focusing area at the brazing interface. S3. Control different array element combinations to transmit and receive ultrasonic waves according to the excitation delay time. Scan the circumferential direction of the brazing interface by electronic scanning. At the same time, make the circumferential phased array probe move linearly along the axis of the tube bundle to be tested, and record the circumferential scanning position and the axial scanning position simultaneously to obtain the ultrasonic echo signal corresponding to different spatial positions. S4. Extract the inner wall echo formed by the inner wall, the interface echo formed by the brazing interface, and the outer boundary reflected echo formed by the outer alloy block located outside the brazing interface from the ultrasonic echo signal. Characterize the coupling state of the liquid coupling region based on the inner wall echo, and compensate for the coupling state of the interface echo and the outer boundary reflected echo based on the coupling state. S5. Based on the ultrasonic echo signal after coupling state compensation, obtain the interface reflection characteristics of the interface echo, the transmission reflection characteristics of the outer boundary reflected echo, and the multiple reflection characteristics of the multiple reflected echo formed by the sound wave reciprocating between the inner wall and the internal defects of the brazing through the pipe wall, and determine whether there are internal defects of the brazing at the corresponding scanning position based on the combination of at least two characteristics. S6. Map the detection results of different scanning positions to the detection matrix according to the circumferential scanning position and the axial scanning position. The detection matrix includes multiple circumferential detection units and multiple axial detection units. Form a defect area based on the spatial continuity of the defect judgment results of adjacent detection positions, and determine the position, extension direction and coverage of the internal defects of the brazing according to the defect area.

[0006] Preferably, in step S2, delay compensation is performed on each element of the circumferential phased array probe according to the curvature of the tube bundle to be tested; taking the focusing area on the brazing interface as the target, the excitation delay time of each element is determined according to the difference between the ultrasonic propagation time of each element to the focusing area, so that the ultrasonic waves emitted by each element participating in the current ultrasonic wave emission arrive at the focusing area at the same time or within the preset time deviation range. The focusing area and the excitation delay time of each array element are updated as the scanning position changes in the circumferential direction, so that the ultrasonic beam is focused at different circumferential positions of the brazing interface.

[0007] Preferably, the excitation delay time of each array element (201) is determined according to the following formula: ; In the formula, Let be the excitation delay time for the i-th array element (201). The actual ultrasound propagation time from the i-th array element (201) to the current focusing region (10) is given. The maximum value of the actual ultrasonic propagation time corresponding to each array element (201) participating in the current ultrasonic emission; the actual ultrasonic propagation time is calculated based on the propagation distance and corresponding propagation speed of the ultrasonic wave in the liquid coupling region (4) and the pipe wall (102).

[0008] Preferably, in step S4, the amplitude and / or energy of the inner wall echo are used as the coupling state evaluation parameters, and the coupling state evaluation parameters corresponding to the current scanning position are compared with the reference coupling state evaluation parameters to obtain the coupling correction coefficient. The amplitude of the interface echo and outer boundary reflected echo corresponding to the current scanning position is compensated based on the coupling correction coefficient to reduce the impact of the coupling state change in the liquid coupling region on the determination result of internal defects in brazing.

[0009] Preferably, when the coupling state evaluation parameter corresponding to the inner wall echo is lower than the preset coupling threshold, the corresponding scanning position is marked as a low-confidence detection position, and the circumferential phased array probe is controlled to re-acquire ultrasonic data at the low-confidence detection position; When the coupling state evaluation parameters reach the preset coupling threshold, defect features are extracted from the interface echo, outer boundary reflection echo, and multiple reflection echo at the corresponding scanning position.

[0010] Preferably, the interface reflection characteristics include the amplitude and / or energy of the interface echo; Transmission and reflection characteristics include the amplitude and / or energy of the reflected echo from the outer boundary; Multiple reflection characteristics include at least one of the following: the number of multiple reflected echoes, the time interval between adjacent multiple reflected echoes, and the cumulative energy of the multiple reflected echoes.

[0011] Preferably, a defect evaluation value D is established based on the interface reflection characteristics of the interface echo (12), the transmission and reflection characteristics of the outer boundary reflected echo (13), and the multiple reflection characteristics of the multiple reflected echo (14). The defect evaluation value D satisfies: ; In the formula, The interface reflection characteristics are after normalization. The transmission and reflection characteristics are obtained and normalized based on the signal attenuation of the reflected echo (13) at the outer boundary. The multiple reflection characteristics are after normalization. , and These are the weighting coefficients of the corresponding features; when the defect evaluation value D reaches the preset defect threshold, the corresponding scan position is determined to have an internal brazing defect (9).

[0012] Preferably, the identification of multiple reflected echoes (14) includes the following steps: S81. Determine the interface echo (12) corresponding to the brazing interface (7); S82. Identify multiple candidate reflected echoes that appear consecutively within a preset time window after the interface echo (12); S83. Calculate the time interval between adjacent candidate reflected echoes; S84. Based on the thickness of the pipe wall (102), the position of the brazing interface (7) and the ultrasonic propagation speed in the corresponding material, determine the theoretical reflection period corresponding to the reciprocating propagation of the sound wave between the inner wall (101) and the internal defect (9) of the brazing through the pipe wall (102). S85. When the time interval between multiple candidate reflected echoes matches the theoretical reflection period, the corresponding candidate reflected echo is identified as a multiple reflected echo (14).

[0013] Preferably, in step S6, the circumferential direction of the tube bundle to be tested is divided into multiple circumferential detection units, and the axial direction of the tube bundle to be tested is divided into multiple axial detection units, with one circumferential detection unit and one axial detection unit jointly determining a detection grid; The defect determination results corresponding to each scanning position are assigned to the corresponding detection grid. When multiple detection grids that are determined to have internal defects in the brazing are consecutively adjacent in the circumferential direction and / or axial direction, the multiple consecutively adjacent detection grids are merged to form the defect region. The circumferential and axial extension ranges of the internal brazing defects are determined based on the number of circumferential detection units and the number of axial detection units covered by the defect area.

[0014] Preferably, elastic water-retaining components are respectively provided on both sides of the axial direction of the circumferential phased array probe. The two elastic water-retaining components respectively cooperate with the inner wall of the tube bundle to be tested, and together with the inner wall, they define a liquid coupling area that contains the coupling fluid. The circumferential phased array probe is connected to a push rod, which is used to drive the circumferential phased array probe to move along the axis of the tube bundle to be tested. The circumferential phased array probe is connected to a signal cable to transmit ultrasonic excitation signals and ultrasonic echo signals. During the testing process, the circumferential phased array probe does not mechanically rotate along the circumference of the tube bundle under test. Instead, it performs electronic scanning of the brazing interface in the circumferential direction by switching the array elements and controlling the delay. The probe is then moved linearly along the axial direction of the tube bundle under test by a push rod, thereby performing continuous full-circumferential testing of the brazing interface.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. A circumferential phased array probe is used for electronic scanning in the circumferential direction. During the detection process, there is no need for the probe to mechanically rotate along the circumference of the tube bundle. It can achieve continuous detection of the brazing interface by moving only along the axial direction of the tube bundle, thereby improving the detection coverage and detection efficiency. 2. Delay compensation is performed on each array element according to the curvature of the tube bundle and the position of the brazing interface to make the ultrasonic beam form a stable focus at the brazing interface. Combined with compensation for the liquid coupling region and coupling state, the influence of changes in the curved structure and coupling state on the detection results is reduced. 3. Defect judgment is made by combining interface echo, outer boundary reflected echo and multiple reflected echo, which improves the ability to identify internal brazing defects such as debonding, porosity and lack of fusion and improves the reliability of detection. 4. Construct a detection matrix by combining the circumferential and axial scanning positions. Determine the defect area based on the spatial continuity of the defect detection results to achieve accurate characterization of the location, extension direction, and coverage of internal defects in brazing. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 A schematic diagram of the overall structure of a device for detecting internal defects in brazed tube bundles used in nuclear fusion. Figure 2 This is a schematic diagram illustrating the principle of focusing and detecting the brazing interface of a tube bundle using a circumferential phased array probe. Figure 3 Flowchart of a method for detecting internal defects in brazing tube bundles used in nuclear fusion; Figure 4 A schematic diagram comparing the ultrasonic echo characteristics of a normal brazed interface and a defective brazed interface. Figure 5 This is a schematic diagram of the internal defect detection matrix and defect area reconstruction for brazing.

[0017] In the figure: 1. Tube bundle to be tested, 101. Inner wall, 102. Circumferential phased array probe, 2. Array element, 201. Elastic water-retaining component, 3. Liquid coupling area, 4. Push rod, 5. Signal cable, 6. Brazing interface, 7. External alloy block, 8. Internal brazing defect, 9. Focusing area, 10. Inner wall echo, 11. Interface echo, 12. Outer boundary reflected echo, 13. Multiple reflected echo, 14. Circumferential detection unit, 15. Axial detection unit, 16. Defect area, 17. Detailed Implementation

[0018] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0019] like Figure 1 As shown, this embodiment provides a method for detecting internal defects in the brazing of a nuclear fusion tube bundle, used to detect internal defects in the brazing interface 7 formed between the tube bundle 1 to be tested and the external alloy block 8 in a nuclear fusion component. The tube bundle 1 to be tested has an inner wall 101 and a tube wall 102. The external alloy block 8 is disposed on the outside of the tube bundle 1 to be tested and is connected to the tube bundle 1 to be tested by brazing, thereby forming a brazing interface 7 between the tube wall 102 and the external alloy block 8. During testing, the circumferential phased array probe 2 is inserted into the tube bundle 1 under test. The circumferential phased array probe 2 includes multiple array elements 201 arranged along the circumference of the tube bundle 1 under test. Each array element 201 can transmit and receive ultrasonic waves according to a set excitation sequence and excitation delay time. By changing the combination of array elements 201 involved in transmission and reception and the excitation delay time of each array element 201, an electronic scan of the circumferential direction of the tube bundle 1 under test can be completed without rotating the circumferential phased array probe 2. Elastic water-retaining components 3 are respectively provided on both sides of the axial direction of the circumferential phased array probe 2. The elastic water-retaining components 3 can be rubber rings, elastic sealing rings, or other water-retaining structures that can elastically contact the inner wall 101. The two elastic water-retaining components 3 and the inner wall 101 together form a partially closed liquid coupling region 4. The liquid coupling region 4 is filled with water or other coupling fluid suitable for ultrasonic testing, so that the circumferential phased array probe 2 maintains a relatively stable acoustic coupling state as it moves along the tube bundle 1 to be tested. The circumferential phased array probe 2 is connected to a push rod 5, which enables the circumferential phased array probe 2 to move linearly along the axis of the tube bundle 1 under test. The circumferential phased array probe 2 is also connected to a signal cable 6, which is used to transmit ultrasonic excitation signals and ultrasonic echo signals received by array elements 201. Thus, during the detection process, the circumferential phased array probe 2 only needs to move mechanically along the axis of the tube bundle 1 under test, while the circumferential detection is completed by electronic scanning by multiple array elements 201, eliminating the need for a circumferential rotation drive mechanism.

[0020] The method for detecting internal defects in the brazing of nuclear fusion tube bundles in this embodiment specifically includes the following steps.

[0021] S1. Obtain the structural dimensions of the tube bundle 1 to be tested, and insert the circumferential phased array probe 2 into the tube bundle 1. A stable liquid coupling region 4 is constructed between the probe and the inner wall 101 using an elastic water-retaining component 3. S1.1. Before testing, obtain the inner diameter of the tube bundle 1, the thickness of the tube wall 102, and the radial position parameters of the brazing interface 7 relative to the inner wall 101. These parameters can be obtained based on the design dimensions of the component to be tested, or they can be obtained through measurement before testing. S1.2. Insert the circumferential phased array probe 2 into the tube bundle 1 to be tested from one end, so that each array element 201 faces the inner wall 101, and make the two elastic water-retaining components 3 contact the inner wall 101 respectively. S1.3 Add coupling fluid between the two elastic water-retaining components 3 to establish a liquid coupling region 4 between the circumferential phased array probe 2 and the inner wall 101; S1.4 The elastic water-retaining component 3 can slide along the inner wall 101 with the circumferential phased array probe 2 while retaining the coupling fluid. Therefore, during the continuous axial movement of the circumferential phased array probe 2, the detection area can still maintain a stable liquid coupling state, reducing the attenuation of ultrasonic signals caused by the loss of coupling fluid.

[0022] S2. Combining the curvature of the tube bundle 1 to be tested with the radial position of the brazing interface 7, calculate the excitation delay time of each array element 201 so that the ultrasonic wave forms a focused area 10 at the brazing interface 7, and dynamically update the focusing parameters with the circumferential scanning position. S2.1, such as Figure 2 As shown, the inner wall 101 of the tube bundle 1 to be tested is arc-shaped, and the distance between each array element 201 and the target detection position on the brazing interface 7 varies. The corresponding ultrasonic propagation path is determined based on the inner diameter of the tube bundle 1 to be tested, the thickness of the tube wall 102, the position of the brazing interface 7, and the spatial position of each array element 201, so as to reduce the influence of the tube bundle curvature on the ultrasonic beam propagation direction and focusing position. S2.2 Select the target detection position on the brazing interface 7 as the focusing area 10. Based on the ultrasonic propagation path from each array element 201 participating in the current transmission to the focusing area 10, determine the propagation distance of the ultrasonic wave in the liquid coupling area 4 and the pipe wall 102 respectively, and calculate the actual ultrasonic propagation time from each array element 201 to the focusing area 10 in combination with the propagation speed of the ultrasonic wave in the corresponding medium. S2.3 In one embodiment, the excitation delay time of the i-th array element 201 is determined according to the following formula: ; In the formula, Let be the excitation delay time for the i-th array element 201; The actual ultrasound propagation time from the i-th array element 201 to the current focused region 10; The maximum value of the actual ultrasonic propagation time corresponding to each array element 201 participating in the current ultrasonic emission; S2.4 When the ultrasonic propagation path passes sequentially through the liquid coupling region 4 and the pipe wall 102, the actual ultrasonic propagation time corresponding to the i-th array element 201 can be calculated based on the ratio of the propagation distance to the propagation speed of the ultrasonic wave in the liquid coupling region 4 and the ratio of the propagation distance to the propagation speed in the pipe wall 102, and the two propagation times are added together. This method can account for the influence of differences in sound velocity between different propagation media on the focusing delay. S2.5. Through the above-mentioned delay control, the ultrasonic waves emitted by different array elements 201 can reach the focusing area 10 at approximately the same time after passing through the liquid coupling area 4 and the pipe wall 102, thereby forming a focused sound field at the brazing interface 7. S2.6 As the electronic scanning position changes along the circumferential direction of the tube bundle 1 to be tested, the position of the focusing area 10 is changed accordingly, and the array element 201 participating in the emission and its excitation delay time are re-determined, so that the ultrasonic beam can be focused sequentially on different circumferential positions of the brazing interface 7.

[0023] S3. According to the excitation delay time, control the array element 201 to complete the circumferential electronic scanning of the brazing interface 7, and at the same time drive the circumferential phased array probe 2 to move continuously along the axial direction, synchronously record the scanning position and collect the corresponding ultrasonic echo signal. S3.1 After completing the calculation of the delay parameters corresponding to the current focusing area 10, control the different array elements 201 combinations to transmit and receive ultrasonic waves in the set order, and complete the electronic scanning of the brazing interface 7 in the circumferential direction through the switching and delay control between array elements 201. S3.2 After completing the data acquisition for one circumferential position or one circumferential detection cycle, the push rod 5 drives the circumferential phased array probe 2 to move along the axis of the tube bundle 1 to be tested, and continues to perform circumferential electronic scanning. S3.3 During the detection process, the circumferential scanning position and axial scanning position corresponding to each group of ultrasonic echo signals are recorded simultaneously. Thus, the circumferential phased array probe 2 does not need to be mechanically rotated along the circumference of the tube bundle 1 under test. It can achieve continuous full-circumference detection of the brazing interface 7 by combining axial linear movement with circumferential electronic scanning.

[0024] S4. Extract the inner wall echo 11, interface echo 12 and outer boundary reflected echo 13 from the acquired ultrasonic echo signal. Evaluate the coupling state based on the inner wall echo 11 and compensate for the coupling state of the interface echo and the outer boundary reflected echo. S4.1, such as Figure 4 As shown, the ultrasonic waves emitted by the array element 201 first propagate to the inner wall 101 through the liquid coupling region 4. Some of the ultrasonic waves form an inner wall echo 11 at the inner wall 101, and the remaining ultrasonic waves continue to pass through the pipe wall 102 and propagate to the brazing interface 7. S4.2 Extract the inner wall echo 11, the interface echo 12 corresponding to the brazing interface 7, and the outer boundary reflected echo 13 formed at the boundary of the outer alloy block 8 after the ultrasonic wave passes through the brazing interface 7, according to the echo arrival time. S4.3 Since the inner wall echo 11 is mainly affected by the coupling state between the circumferential phased array probe 2 and the inner wall 101, the amplitude and / or energy of the inner wall echo 11 are used as the coupling state evaluation parameters. S4.4. Before detection or at a position where coupling is normal, acquire the reference inner wall echo and obtain the reference coupling state evaluation parameters. During detection, compare the inner wall echo 11 at the current scanning position with the reference inner wall echo to obtain the corresponding coupling correction coefficient; S4.5 When the amplitude of the inner wall echo 11 is used as the coupling state evaluation parameter, the coupling correction coefficient can be determined according to the ratio of the reference inner wall echo amplitude to the current inner wall echo amplitude, and the coupling correction coefficient can be used to compensate for the amplitude of the interface echo 12 and the outer boundary reflected echo 13, so as to reduce the signal amplitude fluctuation caused by the change in coupling state. S4.6 When the amplitude or energy of the inner wall echo 11 is lower than the preset coupling threshold, it indicates that there may be insufficient coupling fluid, local bubbles, or abnormal adhesion of the elastic water-retaining component 3 in the current liquid coupling area 4. Mark the scanning position as a low confidence detection position and control the circumferential phased array probe 2 to re-acquire data at the corresponding position. S4.7 When the coupling state evaluation parameters reach the preset coupling threshold, the ultrasonic echo signal at the corresponding position is used to extract defect features, thereby reducing the misjudgment of defects caused by coupling anomalies.

[0025] S5. Extract interface reflection features, transmission reflection features and multiple reflection features, construct a multi-feature fusion defect evaluation value, and determine whether there are internal brazing defects at the corresponding scanning position. S5.1, such as Figure 2 and Figure 4 As shown, when the brazing interface 7 is in good bonding condition, most of the ultrasonic waves can pass through the brazing interface 7 and enter the outer alloy block 8, forming a more obvious outer boundary reflection echo 13 at the boundary of the outer alloy block 8, while the interface echo 12 formed by the brazing interface 7 itself is relatively weak. S5.2 When there is debonding, porosity, lack of fusion or other internal brazing defects 9 in the brazing interface 7, the acoustic impedance at the internal brazing defect 9 changes significantly, causing the ultrasonic wave to be strongly reflected at the internal brazing defect 9. Therefore, the interface echo 12 is enhanced, and the ultrasonic energy that continues to propagate outward through the brazing interface 7 is reduced, causing the outer boundary reflected echo 13 to be weakened accordingly. S5.3. Due to the small thickness of the pipe wall 102, some of the reflected sound waves formed by the internal brazing defect 9 can propagate back and forth between the inner wall 101 and the internal brazing defect 9 through the pipe wall 102, thereby generating multiple consecutive reflected echoes 14. Therefore, this embodiment does not use a single echo amplitude as the basis for defect judgment, but rather makes a judgment by comprehensively considering the interface echo 12, the outer boundary reflected echo 13, and the multiple reflected echoes 14. S5.4 Interface reflection characteristics can be represented by the amplitude, energy, or a combination of the two of the interface echo 12; transmission reflection characteristics can be represented by the amplitude, energy, or attenuation of the outer boundary reflected echo 13 relative to the normal detection position; multiple reflection characteristics can be represented by one or more of the following: the number of multiple reflected echoes 14, the time interval between adjacent echoes, and the cumulative energy. S5.5 In one embodiment, the above three types of features are normalized to obtain interface reflection feature F1, transmission reflection feature F2, and multiple reflection feature F3, and a defect evaluation value D is established: ; In the formula, , and These are the weighting coefficients corresponding to the interface reflection feature F1, the transmission reflection feature F2, and the multiple reflection feature F3, respectively. S5.6 The weighting coefficients can be determined based on standard defect samples, historical test data, or test calibration results, and each weighting coefficient must be a non-negative number. In one embodiment, it can be made This is to facilitate the normalization and comparison of the defect evaluation value D; S5.7 When the defect evaluation value D is less than the preset defect threshold, the corresponding scanning position is determined to be a normal area; when the defect evaluation value D reaches or exceeds the preset defect threshold, the corresponding scanning position is determined to have an internal brazing defect 9. S5.8 To improve the reliability of identifying multiple reflected echoes 14, with interface echo 12 as the starting reference, continuously appearing candidate reflected echoes are identified within a preset time window after interface echo 12, and the time interval between adjacent candidate reflected echoes is calculated. S5.9. Based on the thickness of the pipe wall 102, the position of the brazing interface 7, and the propagation speed of the ultrasonic wave in the corresponding material, determine the theoretical reflection period corresponding to the reciprocating propagation of the sound wave between the inner wall 101 and the brazing internal defect 9 through the pipe wall 102; when the time interval between multiple candidate reflected echoes matches the theoretical reflection period, the corresponding candidate reflected echoes are identified as multiple reflected echoes 14. S5.10 By judging the periodicity of the multiple reflected echoes 14, the multiple reciprocating reflections generated by the internal brazing defect 9 can be distinguished from random noise or other structural echoes, thereby improving the accuracy of identifying the internal brazing defect 9.

[0026] S6. Map the detection results to the detection matrix composed of the circumferential detection unit 15 and the axial detection unit 16, and merge them into a defect region 17 based on spatial continuity to determine the location and extension range of the internal brazing defect 9. S6.1, such as Figure 5 As shown, in order to further determine the location and spatial extension range of the internal brazing defect 9, the circumferential direction of the tube bundle 1 to be tested is divided into multiple circumferential detection units 15, and the axial direction of the tube bundle 1 to be tested is divided into multiple axial detection units 16. S6.2 A circumferential detection unit 15 and an axial detection unit 16 jointly determine a detection grid. The defect judgment results obtained at each scanning position are assigned to the corresponding detection grid according to the corresponding circumferential and axial positions, thereby forming a detection matrix with the circumferential direction and axial direction of the tube bundle 1 to be inspected as two dimensions. S6.3 The detection grid may include at least a normal state and a defect state, and may also be further set to a low confidence state. When the defect evaluation value D at the detection location reaches the preset defect threshold, the corresponding detection grid is assigned a defect state; when the defect evaluation value D does not reach the preset defect threshold, the corresponding detection grid is assigned a normal state. S6.4. Perform spatial continuity judgment on the defect state grid in the detection matrix. When multiple defect state grids are continuously adjacent in the circumferential direction, axial direction, or both directions, merge the multiple continuous defect state grids to form a defect region 17; S6.5. Based on the position of the defect area 17 in the detection matrix, the axial position and circumferential position of the brazing internal defect 9 can be determined; based on the number of circumferential detection units 15 covered by the defect area 17, the extension range of the brazing internal defect 9 along the circumferential direction can be determined; based on the number of axial detection units 16 covered by the defect area 17, the extension range of the brazing internal defect 9 along the axial direction can be determined. S6.6 For multiple defect regions 17 that are spaced apart from each other and not connected to each other, they can be identified as different internal brazing defects 9, thereby realizing the differentiation and location of multiple defects. S6.7 In actual testing, the division dimensions of the circumferential testing unit 15 and the axial testing unit 16 can be determined according to the dimensions of the tube bundle 1 to be tested, the width of the brazed interface 7, and the minimum detection size of the target defect. The smaller the size of the testing unit, the higher the characterization accuracy of the spatial range of the internal brazed defect 9.

[0027] In summary, this invention completes the circumferential detection of the tube bundle 1 under test by electronic scanning of the circumferential phased array probe 2, and completes continuous axial scanning by driving the circumferential phased array probe 2 to move linearly along the axial direction through the push rod 5, thereby avoiding the need to set up a circumferential rotation mechanism inside the narrow tube bundle; a locally stable liquid coupling region 4 is formed by the elastic water-retaining component 3, and the coupling state is evaluated and compensated by the inner wall echo 11; at the same time, by combining curvature adaptive time delay focusing, interface echo 12, outer boundary reflected echo 13 and multiple reflected echo 14 multi-feature fusion judgment, and the detection matrix composed of circumferential detection unit 15 and axial detection unit 16, the invention realizes full-circumferential continuous detection, identification and spatial range characterization of internal defects 9 in brazing.

[0028] It should be noted that the number of array elements 201, operating frequency, element spacing, focusing depth, axial movement step distance, weighting coefficient of defect evaluation value D and corresponding threshold in the circumferential phased array probe 2 can be determined according to the size of the tube bundle 1 to be tested, the material of the tube wall 102, the position of the brazing interface 7 and the detection accuracy requirements, and do not constitute a limitation on the scope of protection of this invention.

Claims

1. A method for detecting internal defects in the brazing of tube bundles used in nuclear fusion, characterized in that, Includes the following steps: S1. Obtain the inner diameter of the tube bundle (1), the thickness of the tube wall (102), and the radial position parameters of the brazing interface (7) relative to the inner wall (101) of the tube bundle (1) to be tested. Insert the circumferential phased array probe (2) with multiple array elements (201) distributed along the circumferential direction into the tube bundle (1) to be tested, and establish a liquid coupling region (4) between the circumferential phased array probe (2) and the inner wall (101). S2. Based on the inner diameter of the tube bundle (1) to be tested, the thickness of the tube wall (102), the radial position of the brazing interface (7) and the spatial position of each array element (201), determine the ultrasonic propagation path from each array element (201) to the brazing interface (7), and determine the excitation delay time of each array element (201) based on the ultrasonic propagation path, so that the ultrasonic waves emitted by each array element (201) enter the tube wall (102) from the inner wall (101) and form a focusing area (10) at the brazing interface (7). S3. Control the different array elements (201) combinations according to the excitation delay time to transmit and receive ultrasonic waves. Scan the circumferential direction of the brazing interface (7) by electronic scanning. At the same time, make the circumferential phased array probe (2) move linearly along the axis of the tube bundle (1) to be tested, and record the circumferential scanning position and the axial scanning position simultaneously to obtain the ultrasonic echo signal corresponding to different spatial positions. S4. Extract the inner wall echo (11) formed by the inner wall (101), the interface echo (12) formed by the brazing interface (7), and the outer boundary reflection echo (13) formed by the outer alloy block (8) located outside the brazing interface (7) from the ultrasonic echo signal. Characterize the coupling state of the liquid coupling region (4) based on the inner wall echo (11), and perform coupling state compensation on the interface echo (12) and the outer boundary reflection echo (13) based on the coupling state. S5. Based on the ultrasonic echo signal after coupling state compensation, obtain the interface reflection characteristics of the interface echo (12), the transmission reflection characteristics of the outer boundary reflection echo (13), and the multiple reflection characteristics of the multiple reflection echo (14) formed by the sound wave reciprocating between the inner wall (101) and the brazed internal defect (9) through the pipe wall (102), and determine whether there is a brazed internal defect (9) at the corresponding scanning position based on the combination of at least two characteristics. S6. Map the detection results of different scanning positions to the detection matrix according to the circumferential scanning position and the axial scanning position. The detection matrix includes multiple circumferential detection units (15) and multiple axial detection units (16). Based on the spatial continuity of the defect judgment results of adjacent detection positions, a defect area (17) is formed. Based on the defect area (17), the position, extension direction and coverage of the internal defects (9) of the brazing are determined.

2. The method for detecting internal defects in brazing tube bundles for nuclear fusion according to claim 1, characterized in that: In step S2, delay compensation is performed on each element (201) of the circumferential phased array probe (2) according to the curvature of the tube bundle (1) to be tested; taking the focusing area (10) on the brazing interface (7) as the target, the excitation delay time of each element (201) is determined according to the difference between the ultrasonic propagation time of each element (201) and the focusing area (10), so that the ultrasonic waves emitted by each element (201) participating in the current ultrasonic wave emission reach the focusing area (10) at the same time or within the preset time deviation range. The focusing area (10) and the excitation delay time corresponding to each array element (201) are updated as the scanning position changes in the circumferential direction, so that the ultrasonic beam is focused at different circumferential positions of the brazing interface (7).

3. The method for detecting internal defects in brazing tube bundles for nuclear fusion according to claim 2, characterized in that, The excitation delay time of each array element (201) is determined according to the following formula: ； In the formula, Let be the excitation delay time for the i-th array element (201). The actual ultrasound propagation time from the i-th array element (201) to the current focusing region (10) is given. The maximum value of the actual ultrasonic propagation time corresponding to each array element (201) participating in the current ultrasonic emission; the actual ultrasonic propagation time is calculated based on the propagation distance and corresponding propagation speed of the ultrasonic wave in the liquid coupling region (4) and the pipe wall (102).

4. The method for detecting internal defects in brazing tube bundles for nuclear fusion according to claim 1, characterized in that: In step S4, the amplitude and / or energy of the inner wall echo (11) are used as the coupling state evaluation parameters, and the coupling state evaluation parameters corresponding to the current scanning position are compared with the reference coupling state evaluation parameters to obtain the coupling correction coefficient. The amplitude of the interface echo (12) and the outer boundary reflected echo (13) corresponding to the current scanning position is compensated according to the coupling correction coefficient, so as to reduce the influence of the coupling state change of the liquid coupling region (4) on the determination result of the internal defects (9) of the brazing.

5. The method for detecting internal defects in brazing of tube bundles for nuclear fusion according to claim 4, characterized in that: When the coupling state evaluation parameter corresponding to the inner wall echo (11) is lower than the preset coupling threshold, the corresponding scanning position is marked as a low confidence detection position, and the circumferential phased array probe (2) is controlled to re-acquire ultrasonic data at the low confidence detection position; When the coupling state evaluation parameters reach the preset coupling threshold, defect features are extracted from the interface echo (12), outer boundary reflection echo (13), and multiple reflection echo (14) at the corresponding scanning position.

6. The method for detecting internal defects in brazing of tube bundles for nuclear fusion according to claim 1, characterized in that: Interface reflection characteristics include the amplitude and / or energy of the interface echo (12); Transmission and reflection characteristics include the amplitude and / or energy of the outer boundary reflected echo (13); The multiple reflection characteristics include at least one of the following: the number of multiple reflected echoes (14), the time interval between adjacent multiple reflected echoes (14), and the cumulative energy of the multiple reflected echoes (14).

7. The method for detecting internal defects in brazing tube bundles for nuclear fusion according to claim 6, characterized in that, Based on the interface reflection characteristics of the interface echo (12), the transmission and reflection characteristics of the outer boundary reflection echo (13), and the multiple reflection characteristics of the multiple reflection echo (14), a defect evaluation value D is established, which satisfies: ; In the formula, The interface reflection characteristics are after normalization. The transmission and reflection characteristics are obtained and normalized based on the signal attenuation of the reflected echo (13) at the outer boundary. The multiple reflection characteristics are after normalization. , and These are the weight coefficients for the corresponding features; When the defect evaluation value D reaches the preset defect threshold, the corresponding scan position is determined to have an internal brazing defect (9).

8. The method for detecting internal defects in brazing tube bundles for nuclear fusion according to claim 7, characterized in that, The identification of multiple reflected echoes (14) includes the following steps: S81. Determine the interface echo (12) corresponding to the brazing interface (7); S82. Identify multiple candidate reflected echoes that appear consecutively within a preset time window after the interface echo (12); S83. Calculate the time interval between adjacent candidate reflected echoes; S84. Based on the thickness of the pipe wall (102), the position of the brazing interface (7) and the ultrasonic propagation speed in the corresponding material, determine the theoretical reflection period corresponding to the reciprocating propagation of the sound wave between the inner wall (101) and the internal defect (9) of the brazing through the pipe wall (102). S85. When the time interval between multiple candidate reflected echoes matches the theoretical reflection period, the corresponding candidate reflected echo is identified as a multiple reflected echo (14).

9. The method for detecting internal defects in brazing of tube bundles for nuclear fusion according to claim 1, characterized in that: In step S6, the circumferential direction of the tube bundle (1) to be tested is divided into multiple circumferential detection units (15), and the axial direction of the tube bundle (1) to be tested is divided into multiple axial detection units (16). A detection grid is determined by one circumferential detection unit (15) and one axial detection unit (16). The defect determination results corresponding to each scanning position are assigned to the corresponding detection grid. When multiple detection grids that are determined to have the internal brazing defect (9) are continuously adjacent in the circumferential direction and / or axial direction, the multiple continuously adjacent detection grids are merged to form the defect area (17). The circumferential and axial extension ranges of the brazing internal defect (9) are determined based on the number of circumferential detection units (15) and the number of axial detection units (16) covered by the defect area (17).

10. The method for detecting internal defects in brazing of tube bundles for nuclear fusion according to any one of claims 1 to 9, characterized in that: Elastic water-retaining components (3) are respectively provided on both sides of the axial direction of the circumferential phased array probe (2). The two elastic water-retaining components (3) cooperate with the inner wall (101) of the tube bundle (1) to be tested, and together with the inner wall (101), they define a liquid coupling area (4) that contains the coupling liquid. The circumferential phased array probe (2) is connected to the push rod (5). The push rod (5) is used to drive the circumferential phased array probe (2) to move along the axis of the tube bundle (1) to be tested. The circumferential phased array probe (2) is connected to a signal cable (6) to transmit ultrasonic excitation signals and ultrasonic echo signals through the signal cable (6). During the testing process, the circumferential phased array probe (2) does not mechanically rotate along the circumferential direction of the tube bundle (1) to be tested. The electronic scanning of the brazing interface (7) in the circumferential direction is completed by the element switching and delay control of each array element (201). The circumferential phased array probe (2) is driven to move linearly along the axial direction of the tube bundle (1) to be tested by the push rod (5), thereby performing continuous full-circumferential testing on the brazing interface (7).

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