A laser ultrasonic testing device and method for a plate

Abstract

The application belongs to the technical field of nondestructive testing and imaging, and particularly relates to a laser ultrasonic testing device and method for plates, which comprises a conveying assembly for conveying plates, a ring-shaped guide rail assembly arranged on one side of the conveying assembly, a plurality of front detection assemblies and rear detection assemblies mounted on the ring-shaped guide rail assembly, the front detection assemblies and the rear detection assemblies being identical in structure, the front detection assembly comprising a sliding seat slidingly mounted on the ring-shaped guide rail assembly, a y-direction linear module mounted on the sliding seat, a module connecting plate fixedly mounted on the sliding block of the y-direction linear module, an x-direction linear module fixedly mounted on the lower surface of the module connecting plate, and a laser detection module fixedly mounted on the sliding block of the x-direction linear module. The application is applicable to plates with coatings, rough surfaces and production line working conditions, and can realize continuous online testing of the plates.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing and imaging technology, specifically relating to a laser ultrasonic testing device and method for sheet metal. Background Technology

[0002] Sheet metal is one of the most basic and widely used forms of materials in equipment manufacturing and structural components, extensively used in aerospace skins and load-bearing components, rail transit car bodies, pressure vessels and heat exchanger tube sheets, automotive body panels, and battery casings. Sheet metal is often subjected to coupled environments of cyclic loads, impact loads, corrosive media, and thermal cycling, and its quality stability directly affects structural safety and life-cycle cost. Common defects in sheet metal include inclusions, porosity, voids, rolling folds, and incomplete welding / penetration introduced by manufacturing and processes; delamination, debonding, interlayer failure, and voids in adhesive layers in multi-layer or adhesive structures; and fatigue cracks, stress corrosion cracks, pitting / corrosion thinning, and impact-induced hidden damage formed during service. These defects can lead to reduced load-bearing capacity, stiffness degradation, shortened service life, and sealing pressure failure, and in severe cases, may cause sudden fractures or leakage accidents. Therefore, efficient, repeatable, and quantifiable non-destructive testing and evaluation of sheet metal is necessary.

[0003] Currently, non-destructive testing of sheet metal mainly includes contact ultrasonic testing, water immersion ultrasonic testing, phased array ultrasonic testing, eddy current testing, magnetic particle testing, and radiographic testing. While these methods have been applied in sheet metal defect detection, they still have limitations in large-area continuous testing, testing stability, and quantitative spatial characterization of defects. These limitations are mainly reflected in the following aspects:

[0004] 1. Poor coupling dependence and surface adaptability

[0005] Contact / immersion ultrasonic testing requires a coupling medium, but factors such as surface roughness, coatings, temperature fluctuations, and on-site maintenance in actual working conditions can easily lead to unstable coupling states. This instability introduces amplitude and phase fluctuations, reducing the amplitude-phase consistency of the test results and weakening the traceability of the data.

[0006] 2. Large-area surface scanning places extremely high demands on motion control and synchronization.

[0007] To achieve rapid scanning of large-area panels, it is essential to ensure that the position encoding, excitation pulses, and data acquisition of the motion system form a strict closed-loop control. If any link in this chain malfunctions, problems such as missed scans, positioning drift, and poor repeatability will occur.

[0008] 3. Traditional two-dimensional imaging methods struggle to achieve three-dimensional quantitative analysis.

[0009] Conventional A / B scans or amplitude C scans only provide two-dimensional projection information, which cannot accurately interpret the three-dimensional morphology of inclined cracks, near-surface defects, and complex situations where multiple defects overlap. The results are often "detectable but difficult to quantify," making it difficult to give the true depth, size, and spatial connectivity of the defects. Summary of the Invention

[0010] This invention provides a laser ultrasonic testing device and method for sheet materials to address the above-mentioned problems.

[0011] To achieve the above objectives, the present invention employs the following technical solution:

[0012] A laser ultrasonic testing device for sheet metal includes a conveying assembly for conveying the sheet metal. An annular guide rail assembly is disposed on one side of the conveying assembly. Multiple pre-detection components and post-detection components are mounted on the annular guide rail assembly. The number of pre-detection components and post-detection components are equal, and they are spaced apart from each other. The number of pre-detection components is not less than five. The pre-detection components and post-detection components have identical structures. Each pre-detection component includes a slide block slidably mounted on the annular guide rail assembly. A y-axis linear module is mounted on the slide block. A module connecting plate is fixedly mounted on the slider of the y-axis linear module. An x-axis linear module is fixedly mounted on the lower surface of the module connecting plate. A laser detection module is fixedly mounted on the slider of the x-axis linear module. The x-axis linear modules in the pre-detection components and post-detection components are arranged in a staggered manner.

[0013] Furthermore, the annular guide rail assembly includes multiple brackets, on which an annular guide rail is mounted. An annular rack is fixedly disposed in the middle of the outer side of the annular guide rail. Annular guide grooves are provided at the upper and lower parts of both the inner and outer sides of the annular guide rail. Two pairs of guide wheel groups are rotatably mounted in the slide, and there are four groups of guide wheels, which are respectively fitted into the four annular guide grooves of the annular guide rail. The annular rack is meshed with a drive gear, which is fixedly mounted on a rotating shaft. The rotating shaft is rotatably mounted in the slide. A transmission gear is also fixedly mounted on the rotating shaft. The transmission gear meshes with an intermediate gear, which is rotatably mounted on the slide. A motor gear is meshed with the other side of the intermediate gear. The motor gear is fixedly mounted on the output shaft of the drive motor, and the drive motor is fixedly mounted on the slide.

[0014] A laser ultrasonic testing method for sheet metal includes the following steps:

[0015] S1. Eight stations are set on the side of the annular guide rail near the conveying component, sequentially named the initial station, station 1, station 2, station 3, station 4, station 5, station 6, and exit station along the material feeding direction. The distance between adjacent stations is dx, where dx < L, and L is the maximum stroke of the x-direction linear module. In the initial state, the distance between the x-direction linear modules in the front detection component and the rear detection component is dy. When the rear detection component is located at the initial station, the horizontal distance between the x-direction linear module in the rear detection component and the material is dy. When the front detection component is located at the initial station, the horizontal distance between the x-direction linear module in the front detection component and the material is 0.

[0016] S2, Sheet Metal Inspection: During the inspection process, the sheet metal maintains a constant speed of v. The pre-inspection component and the post-inspection component maintain a constant speed of v from the initial station to the exit station. The movement time of the pre-inspection component and the post-inspection component between adjacent stations is T. The pre-inspection component starts inspecting the sheet metal from the initial station. The post-inspection component follows the pre-inspection component and performs the same displacement action from station one. It starts inspecting the sheet metal from station three. When the pre-inspection component and the post-inspection component are inspecting, the laser detection module is first driven by the x-axis linear module to move in the x-axis by a step distance Δd, thus completing one x-axis inspection. The inspection stroke in the x-axis is equal to dx. The time required for a single x-axis inspection is t. The value of Δd ranges from 1 mm to 5 mm. mm, then the y-axis linear module drives the x-axis linear module to move in the y-axis with a step distance of Δy. After each y-axis step, the x-axis linear module drives the laser detection module to perform an x-axis detection. The value of Δy ranges from 1 mm to 5 mm. Let the width to be detected in the y-axis of the board be W, and W = 2dy. The x-axis linear module moves dy / 2 in the y-axis every time T elapses. The time required for the x-axis linear module to complete the coverage in the width direction of the board is 4T. When the front detection component is at station number four, the x-axis linear module on it reaches the front side of the board. When the rear detection component exits the station, the x-axis linear module on it reaches the front side of the board. After the x-axis linear module in the front detection component reaches the front side of the board and completes the last x-axis detection, it continues to move in the y-axis linear module to make the front detection component... The x-axis linear module leaves the detection area and enters the reset preparation position. When the front detection component reaches station number six, the x-axis linear module in the front detection component stops its y-axis stepping movement along the y-axis linear module. After the front detection component and the rear detection component reach the exit station and are delayed for time t, they begin to reset along the circular guide rail towards the initial station to allow time for the final x-axis detection of the rear detection component. The time required for the reset movement is 2T-t. When the front detection component or the rear detection component reaches the initial station, the laser detection module, the x-axis linear module, and the y-axis linear module all return to their initial state.

[0017] S3, Data Processing: After the front-end or rear-end detection component completes the detection task for the corresponding detection area, the three-dimensional detection signal data of the detection area is obtained. ,in, Indicates the horizontal dimension. Represents the vertical dimension. Indicates the time dimension;

[0018] Three-dimensional detection signal data The data is truncated to obtain the truncated 3D detection signal data. The truncated time period is [time period missing]. ; The start time point of the valid signal. This is the termination time point of a valid signal;

[0019] The captured 3D detection signal data is bandpass filtered to obtain the preprocessed data volume. ;

[0020] For the preprocessed data volume Performing a Fourier transform along the time dimension yields... :

[0021] ;

[0022] At each discrete frequency Perform a two-dimensional Fourier transform on the xy-plane to construct the frequency-wavenumber domain:

[0023] ;

[0024] For each discrete frequency With transverse wavenumber Calculate the longitudinal wavenumber :

[0025] ;

[0026] in, The speed at which ultrasound propagates within the board material;

[0027] Calculate the phase shift term and perform the downconversion at any depth layer:

[0028] ;

[0029] in The depth value Δz is a single-layer depth value, determined based on the plate thickness and imaging accuracy, and ranges from 0.0001 mm to 0.001 mm. The count value represents the number of... layer, , The number of data points in the time dimension of the 3D detection signal data; The depth to be extended;

[0030] The focusing result in the spatial domain is obtained through two-dimensional inverse Fourier transform:

[0031] ;

[0032] in, It is a phase term in complex exponential form. Represents the imaginary unit;

[0033] Amplitude imaging is performed using a method of in-band complex field superposition and modulus extraction.

[0034] ;

[0035] in, For the effective frequency band set, The detection results for the detection area;

[0036] The test results from each testing area are combined in sequence to obtain the test results for the entire board.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. This invention does not require a coupling medium, avoiding the amplitude and phase inconsistency problems caused by coupling fluctuations in contact / water immersion ultrasound, while reducing maintenance costs; it is suitable for coated surfaces, rough surfaces and production line conditions, and can realize continuous online inspection of materials.

[0039] 2. The front-end detection component and the rear-end detection component of this invention are arranged in a staggered manner on the annular guide rail according to distance constraints, and a cyclic compensation mechanism is adopted to ensure that there is no missed scan in the length direction of the plate and full coverage in the width direction. At the same time, the positioning consistency and repeatability are improved through synchronous movement. This invention is well matched with the laser ultrasonic detection method, and can reduce coupling dependence while taking into account detection efficiency and characterization ability, making it more suitable for engineering applications with large areas and complex working conditions of plates.

[0040] 3. Unlike the strongly coupled transmission method of "one chain driving the whole vehicle to synchronize", this invention integrates an independent drive motor and gear transmission chain on each slide, so that each slide has independent speed planning and motion control capabilities, and can realize "on-demand scheduling and misalignment compensation" according to the detection rhythm; while meeting the coverage and synchronization requirements, it improves the robustness to speed fluctuations and operating condition disturbances.

[0041] 4. This invention integrates the data acquired by two-dimensional surface scanning into a three-dimensional data volume, performs frequency domain wave field migration and phase compensation, supports layered sound velocity correction and layer-by-layer recursion, and finally outputs slices, profiles and three-dimensional volume data of arbitrary depth, which significantly enhances the quantitative characterization ability of near-surface defects, tilted cracks and multiple defect superposition cases. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the present invention;

[0043] Figure 2 This is a cross-sectional view of the annular guide rail of the present invention;

[0044] Figure 3This is a schematic diagram of the structure of the pre-detection component of the present invention;

[0045] Figure 4 This is a schematic diagram of the detection conditions of the present invention;

[0046] Figure 5 A three-dimensional imaging view of a copper / aluminum corrugated plate, parallel to the YZ plane.

[0047] Figure 6 A cross-sectional image of a copper / aluminum corrugated plate parallel to the XZ plane in three-dimensional imaging;

[0048] In the diagram, the components are: 1. Conveying component; 2. Plate; 3. Annular guide rail assembly; 4. Pre-detection component; 5. Post-detection component; 6. Initial station; 7. Station 1; 8. Station 2; 9. Station 3; 10. Station 4; 11. Station 5; 12. Station 6; 13. Exit station; 301. Bracket; 302. Annular guide rail; 303. Annular rack; 304. Annular guide groove; 401. Slide; 402. Y-axis linear module; 403. X-axis linear module; 404. Laser detection module; 405. Guide wheel assembly; 406. Drive gear; 407. Rotating shaft; 408. Transmission gear; 409. Intermediate gear; 410. Motor gear; 411. Drive motor; 412. Module connecting plate. Detailed Implementation

[0049] To further illustrate the technical solution of the present invention, the present invention will be further described below through embodiments.

[0050] like Figures 1 to 3 As shown, a laser ultrasonic testing device for sheet metal includes a conveying assembly 1 for conveying sheet metal 2. An annular guide rail assembly 3 is disposed on one side of the conveying assembly 1. Multiple pre-detection assemblies 4 and post-detection assemblies 5 are mounted on the annular guide rail assembly 3. The number of pre-detection assemblies 4 and post-detection assemblies 5 is the same, and they are spaced apart from each other. The number of pre-detection assemblies 4 is not less than five, and the structures of the pre-detection assemblies 4 and post-detection assemblies 5 are similar. Similarly, the front detection component 4 includes a slide block 401 slidably mounted on the annular guide rail component 3, a y-axis linear module 402 mounted on the slide block 401, a module connecting plate 412 fixedly mounted on the slider of the y-axis linear module 402, an x-axis linear module 403 fixedly mounted on the lower surface of the module connecting plate 412, and a laser detection module 404 fixedly mounted on the slider of the x-axis linear module 403. The x-axis linear modules 403 in the front detection component 4 and the rear detection component 5 are arranged in a staggered manner.

[0051] The annular guide rail assembly 3 includes multiple brackets 301, on which an annular guide rail 302 is mounted. An annular rack 303 is fixedly disposed in the middle of the outer side of the annular guide rail 302. Annular guide grooves 304 are provided on the upper and lower parts of both the inner and outer sides of the annular guide rail 302. Two pairs of guide wheel sets 405 are rotatably mounted in the slide block 401. There are four sets of guide wheel sets 405, each corresponding to one of the four annular guide grooves 304 of the annular guide rail 302. The annular rack 303 is engaged with a drive mechanism. Gear 406, the drive gear 406 is fixedly mounted on the rotating shaft 407, the rotating shaft 407 is rotatably mounted in the slide 401, a transmission gear 408 is also fixedly mounted on the rotating shaft 407, the transmission gear 408 meshes with an intermediate gear 409, the intermediate gear 409 is rotatably mounted on the slide 401, a motor gear 410 is meshed and connected on the other side of the intermediate gear 409, the motor gear 410 is fixedly mounted on the output shaft of the drive motor 411, and the drive motor 411 is fixedly mounted on the slide 401.

[0052] like Figure 4 As shown, a laser ultrasonic testing method for sheet metal includes the following steps:

[0053] S1. Eight workstations are set on the side of the annular guide rail 302 near the conveying component 1, sequentially arranged along the feeding direction of the plate 2 as initial workstation 6, workstation 1 7, workstation 2 8, workstation 3 9, workstation 4 10, workstation 5 11, workstation 6 12 and exit workstation 13. The distance between adjacent workstations is dx, dx < L, where L is the maximum stroke of the x-direction linear module 403. In the initial state, the distance between the x-direction linear modules 403 in the front detection component 4 and the rear detection component 5 is dy. When the rear detection component 5 is located on the initial workstation 6, the horizontal distance between the x-direction linear module 403 in the rear detection component 5 and the plate 2 is dy. When the front detection component 4 is located on the initial workstation 6, the horizontal distance between the x-direction linear module 403 in the front detection component 4 and the plate 2 is 0.

[0054] S2, Plate Inspection: During the inspection process, plate 2 maintains a constant speed of v. The pre-inspection component 4 and the post-inspection component 5 maintain a constant speed of v from the initial station 6 to the exit station 13. The movement time of the pre-inspection component 4 and the post-inspection component 5 between adjacent stations is T. The pre-inspection component 4 starts inspecting plate 2 from the initial station 6. The post-inspection component 5 starts from station 1 7 and performs the same displacement action as the pre-inspection component 4. It starts inspecting plate 2 from station 3 9. When the pre-inspection component 4 and the post-inspection component 5 are inspecting, they first move through the x-axis... Line module 403 drives laser detection module 404 to move in the x-direction with a step distance of Δd, thereby completing one x-direction detection. The detection stroke of the x-direction detection is equal to dx, and the time required for a single x-direction detection is t. Then, y-direction linear module 402 drives x-direction linear module 403 to move in the y-direction with a step distance of Δy. After each y-direction step, x-direction linear module 403 drives laser detection module 404 to perform one x-direction detection. Let the width to be detected in the y-direction of the board 2 be W, and W = 2dy. The x-direction linear module 403 moves dy / 2 in the y-direction every time time T elapses. The time required for the x-direction linear module 403 to complete coverage in the width direction of the board is 4T; when the front detection component 4 is at station 4 10, the x-direction linear module 403 located on it reaches the front side of the board 2; when the rear detection component 5 exits station 13, the x-direction linear module 403 located on it reaches the front side of the board 2; after the x-direction linear module 403 in the front detection component 4 reaches the front side of the board 2 and completes the last x-direction detection, it continues to move step by step along the y-direction linear module 402, so that the x-direction linear module 403 in the front detection component 4 leaves the detection area and enters the reset preparation position, until the front detection... When the detection component 4 reaches station 12, the x-direction linear module 403 in the front detection component 4 stops its y-direction stepping movement along the y-direction linear module 402; after the front detection component 4 and the rear detection component 5 reach the exit station 13 and are delayed for time t, they begin to move back to the initial station 6 along the circular guide rail 302 to allow time for the last x-direction detection of the rear detection component 5. The time required for the reset movement is 2T-t. When the front detection component 4 or the rear detection component 5 reaches the initial station 6, the laser detection module 404, the x-direction linear module 403 and the y-direction linear module 402 all return to their initial state.

[0055] S3, Data Processing: After the front detection component 4 or the rear detection component 5 completes the detection task of the corresponding detection area, the three-dimensional detection signal data of the detection area is obtained. ,in, Indicates the horizontal dimension. Represents the vertical dimension. Indicates the time dimension;

[0056] Three-dimensional detection signal data The data is truncated to obtain the truncated 3D detection signal data. The truncated time period is [time period missing]. ; The start time point of the valid signal. This is the termination time point of a valid signal;

[0057] The captured 3D detection signal data is bandpass filtered to obtain the preprocessed data volume. ;

[0058] For the preprocessed data volume Performing a Fourier transform along the time dimension yields... :

[0059] ;

[0060] At each discrete frequency Perform a two-dimensional Fourier transform on the xy-plane to construct the frequency-wavenumber domain:

[0061] ;

[0062] For each discrete frequency With transverse wavenumber Calculate the longitudinal wavenumber :

[0063] ;

[0064] in, The speed at which ultrasound propagates within the board material;

[0065] Calculate the phase shift term and perform the downconversion at any depth layer:

[0066] ;

[0067] in This represents the depth value of a single layer. The count value represents the number of... layer, , The number of data points in the time dimension of the 3D detection signal data; The depth to be extended;

[0068] The focusing result in the spatial domain is obtained through two-dimensional inverse Fourier transform:

[0069] ;

[0070] in, It is a phase term in complex exponential form. Represents the imaginary unit;

[0071] Amplitude imaging is performed using a method of in-band complex field superposition and modulus extraction.

[0072] ;

[0073] in, For the effective frequency band set, The detection results for the detection area;

[0074] The test results from each testing area are combined in sequence to obtain the test results for the entire board.

[0075] The foregoing has shown and described the main features and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0076] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A laser ultrasonic testing method for sheet metal, characterized in that: A laser ultrasonic testing device for sheet metal includes a conveying assembly (1) for conveying sheet metal (2). An annular guide rail assembly (3) is provided on one side of the conveying assembly (1). Multiple pre-detection assemblies (4) and post-detection assemblies (5) are mounted on the annular guide rail assembly (3). The number of pre-detection assemblies (4) and post-detection assemblies (5) is the same, and they are spaced apart. The number of pre-detection assemblies (4) is not less than five. The structure of the pre-detection assemblies (4) and post-detection assemblies (5) is as follows: Similarly, the front detection component (4) includes a slide block (401) slidably mounted on the annular guide rail component (3), a y-direction linear module (402) mounted on the slide block (401), a module connecting plate (412) fixedly mounted on the slider of the y-direction linear module (402), an x-direction linear module (403) fixedly mounted on the lower surface of the module connecting plate (412), and a laser detection module (404) fixedly mounted on the slider of the x-direction linear module (403). The x-direction linear modules (403) in the front detection component (4) and the rear detection component (5) are arranged in an alternating manner. The annular guide rail assembly (3) includes multiple brackets (301), on which an annular guide rail (302) is mounted. An annular rack (303) is fixedly arranged in the middle of the outer side of the annular guide rail (302). Annular guide grooves (304) are provided on the upper and lower parts of the inner and outer sides of the annular guide rail (302). Two pairs of guide wheel sets (405) are rotatably installed in the slide (401). There are four sets of guide wheel sets (405), which are respectively fitted into the four annular guide grooves (304) of the annular guide rail (302). The annular rack (303) is meshed with a drive gear. 406), the drive gear (406) is fixedly mounted on the rotating shaft (407), the rotating shaft (407) is rotatably mounted in the slide (401), a transmission gear (408) is also fixedly mounted on the rotating shaft (407), the transmission gear (408) meshes with an intermediate gear (409), the intermediate gear (409) is rotatably mounted on the slide (401), a motor gear (410) meshes with the other side of the intermediate gear (409), the motor gear (410) is fixedly mounted on the output shaft of the drive motor (411), and the drive motor (411) is fixedly mounted on the slide (401); The laser ultrasonic testing method includes the following steps: S1, on the side of the annular guide rail (302) near the conveying component (1), eight stations are set up in sequence along the feeding direction of the plate (2): initial station (6), station 1 (7), station 2 (8), station 3 (9), station 4 (10), station 5 (11), station 6 (12), and exit station (13). The distance between adjacent stations is dx, dx < L, where L is the maximum stroke of the linear module (403) in the x-direction. In the initial state, the front... The distance between the x-direction linear module (403) in the front detection component (4) and the rear detection component (5) is dy; when the rear detection component (5) is located at the initial station (6), the horizontal distance between the x-direction linear module (403) in the rear detection component (5) and the plate (2) is dy; when the front detection component (4) is located at the initial station (6), the horizontal distance between the x-direction linear module (403) in the front detection component (4) and the plate (2) is 0; S2, Plate Inspection: During the inspection process, the plate (2) always maintains a uniform speed of v. The pre-inspection component (4) and the post-inspection component (5) maintain a uniform speed of v from the initial station (6) to the exit station (13). The movement time of the pre-inspection component (4) and the post-inspection component (5) between adjacent stations is T. The pre-inspection component (4) starts to inspect the plate (2) from the initial station (6). The post-inspection component (5) starts from station 1 (7) and performs the same displacement action as the pre-inspection component (4). It starts to inspect the plate (2) from station 3 (9). When the pre-inspection component (4) and the post-inspection component (5) are inspecting, they first... The x-axis linear module (403) drives the laser detection module (404) to move in the x-axis with a step distance of Δd, thereby completing one x-axis detection. The detection stroke of the x-axis detection is equal to dx, and the time required for a single x-axis detection is t. Then, the y-axis linear module (402) drives the x-axis linear module (403) to move in the y-axis with a step distance of Δy. After each y-axis step, the x-axis linear module (403) drives the laser detection module (404) to perform one x-axis detection. Let the width to be detected of the board (2) in the y-axis be W, and W = 2dy. The x-axis linear module (403) moves dy / 2 in the y-axis every time time T passes. 403) The time required to complete the coverage in the width direction of the board is 4T; when the front detection component (4) is at station 4 (10), the x-direction linear module (403) located on it reaches the front side of the board (2); when the rear detection component (5) exits station (13), the x-direction linear module (403) located on it reaches the front side of the board (2); after the x-direction linear module (403) in the front detection component (4) reaches the front side of the board (2) and completes the last x-direction detection, it continues to move step by step along the y-direction linear module (402) so that the x-direction linear module (403) in the front detection component (4) leaves the detection area and enters the reset preparation position, until the front detection component (4) When the device reaches station 6 (12), the x-direction linear module (403) in the front detection component (4) stops moving in the y-direction along the y-direction linear module (402); after the front detection component (4) and the rear detection component (5) reach the exit station (13) and are delayed for time t, they begin to move along the circular guide rail (302) to the initial station (6) to allow time for the last x-direction detection of the rear detection component (5). The time required for the reset movement is 2T-t. When the front detection component (4) or the rear detection component (5) reaches the initial station (6), the laser detection module (404), the x-direction linear module (403) and the y-direction linear module (402) all return to their initial state. S3, Data Processing: After the front detection component (4) or the rear detection component (5) completes the detection task of the corresponding detection area, the three-dimensional detection signal data of the detection area is obtained. ,in, Indicates the horizontal dimension. Represents the vertical dimension. Indicates the time dimension; Three-dimensional detection signal data The data is truncated to obtain the truncated 3D detection signal data. The truncated time period is [time period missing]. ; The start time point of the valid signal. This is the termination time point of a valid signal; The captured 3D detection signal data is bandpass filtered to obtain the preprocessed data volume. ; For the preprocessed data volume Performing a Fourier transform along the time dimension yields... : ； At each discrete frequency Perform a two-dimensional Fourier transform on the xy-plane to construct the frequency-wavenumber domain: ； For each discrete frequency With transverse wavenumber Calculate the longitudinal wavenumber : ； in, The speed at which ultrasound propagates within the board material; Calculate the phase shift term and perform the downconversion at any depth layer: ； in This represents the depth value of a single layer. The count value represents the number of... layer, , The number of data points in the time dimension of the 3D detection signal data; The depth to be extended; The focusing result in the spatial domain is obtained through two-dimensional inverse Fourier transform: ； in, It is a phase term in complex exponential form. Represents the imaginary unit; Amplitude imaging is performed using a method of in-band complex field superposition and modulus extraction. ； in, For the effective frequency band set, The detection results for the detection area; The test results from each testing area are combined in sequence to obtain the test results for the entire board.

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