Laser phased array ultrasonic composite detection system and method for internal interface defects of GIS insulator metal insert

Abstract

This invention discloses a laser phased array ultrasonic composite detection system and method for internal interface defects in GIS insulator metal inserts. The system includes a pulsed laser, an ultrasonic array probe, a control computer equipped with ultrasonic signal acquisition and processing software, and a two-dimensional laser scanning galvanometer. The detection method utilizes a pulsed laser to generate ultrasonic waves on the metal insert side. When the ultrasonic waves propagate to the interface, they are differentiated by the physical mechanism that internal defects completely reflect the ultrasonic waves, while defect-free areas allow ultrasonic waves to pass through. The ultrasonic array probe acquires the ultrasonic signal at the inner wall surface. The computer-controlled two-dimensional laser scanning galvanometer rapidly scans the entire interface of the epoxy resin-metal insert to obtain full matrix data. After the overall scan is completed, the corresponding ultrasonic array probe element is selected, and the computer, with a fixed rotation angle, uses a full-focusing algorithm to perform high-resolution imaging of the interface, thus detecting internal interface defects. This invention reduces the cost of detection equipment while improving the evaluation efficiency of internal defects in the epoxy resin-metal insert interface of GIS insulators.

Description

Technical Field

[0001] This invention relates to the field of non-destructive testing technology for electrical equipment, and in particular to a laser phased array ultrasonic composite testing system and method for internal interface defects of GIS insulator metal inserts. Background Technology

[0002] Gas-insulated metal-enclosed switchgear (GIS) is widely used in modern power grids. Insulators are typically made by casting metal inserts from epoxy resin composite materials. Under the thermal stress of production or operation, defects such as micro-gaps, debonding, and layering can easily occur at the interface between the epoxy resin and the metal inserts, seriously threatening power grid safety. Currently, conventional X-ray methods are insensitive to thin-layer debonding defects; conventional ultrasonic testing is difficult to achieve high signal-to-noise ratio detection due to the large attenuation of epoxy resin and the large difference in acoustic impedance, resulting in some internal interface defects becoming "undetectable" blind spots. Summary of the Invention

[0003] The purpose of this invention is to solve the problem of difficulty in detecting internal defects at the epoxy resin-metal insert interface of gas-insulated metal-enclosed switchgear (GIS) insulators using conventional methods. This invention provides a laser phased array ultrasonic composite detection system and method for internal interface defects in GIS insulator metal inserts, reducing the cost of detection equipment and improving the evaluation efficiency of internal defects at the epoxy resin-metal insert interface of GIS insulators.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A laser-ultrasonic reflection phased array full-focusing imaging system for detecting internal defects at the interface of epoxy resin metal inserts in GIS insulators includes a pulsed laser 1, an optical fiber 2, an optical fiber-coupled laser focusing lens 3, an ultrasonic array probe 4, a preamplifier 7, a bandpass filter 8, a signal acquisition card 9, a control computer 10 equipped with signal acquisition and processing software, and a two-dimensional laser scanning galvanometer 11. The optical fiber-coupled laser focusing lens 3 is connected to the pulsed laser 1 via the optical fiber 2. The pulsed laser 1 is used to excite ultrasonic waves on the side surface of the metal insert of the insulator under test. The ultrasonic array probe 4 is positioned on the opposite side of the laser excitation surface of the metal insert of the insulator under test, and is used for... The system collects ultrasonic signals propagating from within the metal insert and reflected through the epoxy resin-metal insert interface. A control computer 10, equipped with ultrasonic signal acquisition and processing software, is connected to the pulsed laser 1, ultrasonic array probe 4, signal acquisition card 9, and two-dimensional laser scanning galvanometer 11. After receiving a trigger signal from the pulsed laser 1, the signal acquisition card 9 begins acquiring the time-domain signal measured by the ultrasonic array probe 4 after passing through a preamplifier 7 and a bandpass filter 8. The control computer 10, equipped with the signal acquisition and processing software, is responsible for acquiring and storing the signals from the signal acquisition card 9, and simultaneously controlling the two-dimensional laser scanning galvanometer 11 for imaging processing. The two-dimensional laser scanning galvanometer 11 is used to control the relative movement of the laser beam on the surface of the metal insert of the insulator under test, thereby achieving full-interface scanning.

[0005] When inspecting the epoxy resin-metal insert interface, a pulsed laser 1 emits a Gaussian pulsed laser beam that travels through an optical fiber 2 to a fiber-coupled laser focusing lens 3. The focused pulsed spot is then irradiated onto the metal insert side surface of the insulator by a two-dimensional laser scanning galvanometer 11, and multimode ultrasonic waves 5 are excited inside the metal insert. Defects 6 inside the insulator interface reflect the multimode ultrasonic waves and propagate them towards the metal insert side, thus forming local ultrasonic signal characteristics on the reverse side of the laser-excited surface of the metal insert of the insulator under test. The out-of-plane displacement ultrasonic signal of this area is collected by an ultrasonic array probe 4, thereby realizing the detection at this location. The fiber-coupled laser focusing lens 3 and the ultrasonic array probe 4 are scanned and collected by the two-dimensional laser scanning galvanometer 11, thus realizing the detection of the epoxy resin-metal insert interface quality of the insulator.

[0006] The detection method of the laser-ultrasonic reflection phased array full-focusing imaging system for detecting internal defects at the interface of epoxy resin metal inserts in GIS insulators includes the following steps: Step 1: Install the detection system using a reflective arrangement scheme, placing the ultrasonic excitation end and detection end on opposite sides of the metal insert. First, adjust the fiber-coupled laser focusing lens 3 and the two-dimensional laser scanning galvanometer 11 to align the pulsed laser with one side of the metal insert, while simultaneously attaching the ultrasonic array probe 4 to the other side of the metal insert. Then, adjust the relative positions of the fiber-coupled laser focusing lens 3, the ultrasonic array probe 4, and the two-dimensional laser scanning galvanometer 11 to ensure that the incident area of ​​the pulsed laser and the detection area of ​​the ultrasonic array probe 4 spatially overlap. Adjust to the initial scanning position and set the system parameters. Step 2: Based on the structural dimensions of the test piece, set the two-dimensional scanning area along the circumference and axis and the scanning step spacing, and plan the reciprocating scanning array path of the laser spot to prepare for subsequent ultrasonic point-by-point excitation and interface reflection ultrasonic full matrix (FMC) data acquisition. Step 3: The control computer 10, equipped with signal acquisition and processing software, drives the two-dimensional laser scanning galvanometer 11 to scan and excite ultrasonic waves at the initial position. When the ultrasonic waves propagate to the internal interface, they generate near total reflection by utilizing the huge acoustic impedance difference between the defect (gas / vacuum) and the metal medium. This results in a difference in reflected energy between the partial transmission at the defect-free junction and the reflected waves. The ultrasonic array probe 4 simultaneously acquires the time-domain signals of the reflected echoes containing the above-mentioned energy difference characteristics at each scanning point, and sequentially constructs the full matrix signal data of the interface reflected ultrasonic waves. Step 4: The control computer 10 equipped with signal acquisition and processing software receives the interface reflection ultrasound full matrix signal data synchronously acquired by the ultrasound array probe 4; then, the data is sequentially subjected to translation alignment, digital filtering and normalization preprocessing operations to eliminate interference noise and unify the signal reference. Finally, the processed interface reflection ultrasound full matrix data is stored in the control computer to provide a data source for subsequent imaging. Step 5: The control computer 10 equipped with signal acquisition and processing software drives the two-dimensional laser scanning galvanometer 11 to move to the next detection position according to the scanning step interval set in Step 2, and repeats Step 3 and Step 4 in a loop until all the pre-planned two-dimensional scanning areas are traversed, and all interface reflection ultrasound full matrix signal data of the entire detection interface are acquired and stored. Step 6: All acquired scanning data are classified and extracted according to the step position, and then processed centrally using the Total Focusing (TFM) algorithm. The TFM algorithm is based on the principle of delay summation and wave superposition. It grids the predefined region of interest and calculates the acoustic path delay time from the array element to each grid pixel. By extracting the corresponding amplitude of each grid point in the entire echo signal and performing time-delay superposition focusing, a high-resolution interface TFM image containing the defect location and size is generated, thereby achieving accurate evaluation of internal defects.

[0007] Compared with the prior art, the present invention has the following beneficial effects: By utilizing a reflective detection mechanism that involves "laser excitation on one side of the metal insert, physical discrimination of total reflection / perfect transmission at the defect, phased array reception on the other side, and TFM high-resolution imaging," the problem of undetectable parts is effectively solved, and the imaging resolution and evaluation efficiency are greatly improved. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the internal defect detection system for the epoxy resin-metal insert interface of the insulator of the present invention, wherein: (a) is a schematic diagram of the main components of the detection system, (b) is a schematic diagram of the cross-section of the basin insulator, (c) is a top view of the laser excitation interface, and (d) is a bottom view of the ultrasonic array probe acquisition interface.

[0009] Figure 2 This is a flowchart illustrating the specific implementation steps of the detection method of the present invention.

[0010] Figure 3 (a) is a schematic diagram of the ultrasonic interface reflection principle. Figure 3 Image (b) is a defect imaging image created by the Total Focusing (TFM) algorithm of this invention. Detailed Implementation

[0011] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0012] like Figure 1As shown in (a), (b), (c), and (d), the present invention discloses a laser phased array ultrasonic composite detection system for internal interface defects of GIS insulator metal inserts, comprising a pulsed laser 1, an optical fiber 2, an optical fiber-coupled laser focusing lens 3, an ultrasonic array probe 4, a preamplifier 7, a bandpass filter 8, a signal acquisition card 9, a control computer 10 equipped with signal acquisition and processing software, and a two-dimensional laser scanning galvanometer 11; wherein the optical fiber-coupled laser focusing lens 3 is connected to the high-frequency pulsed laser 1 via the optical fiber 2; the pulsed laser 1 is used to excite ultrasonic waves on the side surface of the metal insert of the insulator under test; the ultrasonic array probe 4 is positioned on the laser-excited side surface of the metal insert of the insulator under test. The reverse side of the insulator is used to collect ultrasonic signals propagating from inside the metal insert and reflected through the epoxy resin-metal insert interface. The control computer 10, equipped with signal acquisition and processing software, is connected to the pulsed laser 1, ultrasonic array probe 4, signal acquisition card 9, and two-dimensional laser scanning galvanometer 11. After receiving the trigger signal from the pulsed laser 1, the signal acquisition card 9 begins to acquire the time-domain signal measured by the ultrasonic array probe 4 after passing through the preamplifier 7 and bandpass filter 8. The control computer 10, equipped with signal acquisition and processing software, is responsible for acquiring and storing the signals from the signal acquisition card 9, and simultaneously controlling the two-dimensional laser scanning galvanometer 11 for imaging processing. The two-dimensional laser scanning galvanometer 11 is used to control the relative movement of the laser beam on the surface of the metal insert of the insulator under test, so as to achieve full interface scanning.

[0013] When inspecting the epoxy resin-metal insert interface of an insulator, a pulsed laser 1 emits a Gaussian pulsed laser beam that travels through an optical fiber 2 to a fiber-coupled laser focusing lens 3. The focused pulsed spot illuminates the metal insert side of the insulator and excites multimode ultrasonic waves 5 inside the metal insert. Defects 6 inside the insulator interface reflect the multimode ultrasonic waves and propagate them towards the metal insert side, thus forming local ultrasonic signal characteristics on the reverse side of the laser-excited surface of the metal insert of the insulator under test. The out-of-plane displacement ultrasonic signal of this area is collected by an ultrasonic array probe 4 to achieve detection at this location. The fiber-coupled laser focusing lens 3 and the ultrasonic array probe 4 are scanned and collected by a two-dimensional laser scanning galvanometer 11, thereby realizing the detection of the epoxy resin-metal insert interface quality of the insulator.

[0014] The detection method of the laser phased array ultrasonic composite detection system for internal interface defects of GIS insulator metal inserts described in this invention includes the following steps: Figure 2 As shown, the details are as follows: Step 1: Install the insulator epoxy resin-metal insert interface internal defect detection system using a reflective arrangement scheme, placing the ultrasonic excitation end and detection end on the two sides of the metal insert respectively; first, adjust the fiber-coupled laser focusing lens 3 and the two-dimensional laser scanning galvanometer 11 to align the pulsed laser with one side of the metal insert, while attaching the ultrasonic array probe 4 to the other side of the metal insert; then adjust the relative positions of the above components so that the incident area of ​​the pulsed laser and the detection area of ​​the ultrasonic array probe 4 spatially coincide, adjust to the initial scanning position and set the system parameters; Step 2: First, set the scanning angle along the θ axis to θ1, the scanning interval to Δθ, and the number of scanning points to d = θ1 ÷ Δθ + 1. Set the scanning length along the x axis to L1, the interval to Δx, and the number of scanning points to m = L1 ÷ Δx + 1. Set the total area of ​​the scanning region to L1 × L2 (L2 is the arc length corresponding to the scanning angle θ1) and the total number of points in the scanning region to m × d. Based on this, pre-plan the scanning area and perform two-dimensional scanning detection by adjusting the reciprocating movement of the excitation spot along the two-dimensional laser scanning galvanometer 11. Step 3: The control computer 10 equipped with signal acquisition and processing software drives the two-dimensional laser scanning galvanometer (11) to be positioned at the initial position of the θ axis and to scan along the x axis to excite ultrasonic waves; the ultrasonic waves propagate to the epoxy resin-metal insert interface, and by utilizing the large acoustic impedance difference between the gas / vacuum and the metal medium at the defect, a near total reflection is formed at the defect, and a significant energy difference is formed with the weak reflection / partial transmission at the defect-free and intact interface, thereby realizing the physical identification of the defect; at the same time, the ultrasonic array probe (4) synchronously acquires the interface reflection echo time domain signals S1,1(t), S1,2(t), ..., S1,n(t), S2,1(t), S2,2(t)...S2,n(t), ...Sm,1(t), Sm,2(t)...Sm,n(t) at each measuring point with the above energy difference characteristics, and sequentially forms the full matrix (FMC) signal data S f1 (t, m×n), where n is the number of array elements of the ultrasonic array probe (4); Step 4: The control computer 10, equipped with signal acquisition and processing software, receives the interface reflection ultrasound full matrix (FMC) signal data S synchronously acquired and transmitted by the ultrasonic array probe 4. f1 (t, m×n); In order to eliminate low-frequency structural noise and improve subsequent imaging quality, the control computer uses processing software to process the original full matrix data S. f1 (t, m×n) are sequentially translated, aligned, bandpass filtered, and normalized to obtain the preprocessed interface reflection ultrasound full matrix signal data S. f1 Finally, the processed high-quality data is stored in a control computer equipped with signal acquisition and processing software.

[0015] Step 5: The control computer 10, equipped with signal acquisition and processing software, drives the two-dimensional laser scanning galvanometer 11 to perform spatial stepping according to the scanning interval Δθ set in Step 2; after each stepping, Steps 3 and 4 are repeated cyclically to sequentially obtain the preprocessed full matrix signal data S at each subsequent detection position. f2 ′(t,m×n), …,S fd ′(t,m×n), until the two-dimensional laser scanning galvanometer (11) completes full coverage of the preset m×d scanning points, and acquires data of all interface scanning areas.

[0016] Step 6: For all the scanning data stored in the control computer 10 equipped with signal acquisition and processing software, classify and organize them according to the corner stepping pattern into S. f1 ′(t,m×n), …,S fd The full matrix data of (t, m×n) is then processed using the Total Focusing (TFM) algorithm. The specific process of the TFM algorithm is as follows: First, a Cartesian coordinate system is established with the excitation laser center as the origin. The predefined region of interest on the interface is divided into a pixel grid. Let the coordinates of any point on the grid be... The acoustic path delay time from the array element to the grid pixel is calculated. This path delay follows the actual physical propagation path from the laser excitation side of the insulator metal insert to the epoxy resin-metal insert interface, and then to the ultrasonic array probe after ultrasonic reflection. Based on the principle of delay summation and wave superposition, the actual distance from the grid point to the detection laser and the receiving array element is calculated to determine the acoustic path, thereby extracting the corresponding amplitude of that point in each column of preprocessed echo signals. Finally, the signal amplitudes representing the information of that point in all scan data are delayed, superimposed, and focused to obtain the superimposed acoustic wave amplitude of the pixels inside the test piece. This process enables image representation of the entire scanning area. The final output is a high-resolution, fully focused imaging image containing the precise location and size of defects in the test piece, thus completing the evaluation of interface defects.

[0017] In the formula: —The laser excitation, and the echo signal received by the phased array transducer Amplitude information of the point; —sound waves emitted to The time it takes for the echo to be received by the phased array transducer elements after the point is defined as: In the formula: —The speed at which sound waves propagate inside the test piece; It is the acoustic amplitude value of the superimposed pixels inside the test piece, which thus characterizes the defects inside the test piece.

Claims

1. A GIS insulator metal insert internal interface defect laser phased array ultrasonic composite detection system, characterized in that: It includes a pulsed laser (1), an optical fiber (2), an optical fiber coupled laser focusing lens (3), an ultrasonic array probe (4), a preamplifier (7), a bandpass filter (8), a signal acquisition card (9), a control computer (10) equipped with signal acquisition and processing software, and a two-dimensional laser scanning galvanometer (11). The fiber-coupled laser focusing lens (3) is connected to the pulsed laser (1) via an optical fiber (2); the pulsed laser (1) is used to excite ultrasonic waves on the metal insert side surface of the insulator under test; the ultrasonic array probe (4) is set on the opposite side of the laser excitation surface of the metal insert of the insulator under test, and is used to collect ultrasonic signals propagating from inside the metal insert and reflected by the epoxy resin-metal insert interface; the control computer (10) equipped with signal acquisition and processing software is connected to the pulsed laser (1), the ultrasonic array probe (4), the signal acquisition card (9), and the two-dimensional laser scanning galvanometer (11); the laser beam originates from the fiber-coupled laser. The laser focusing lens (3) transmits the laser beam onto the two-dimensional laser scanning galvanometer (11). After receiving the trigger signal from the pulsed laser (1), the signal acquisition card (9) begins to acquire the time domain signal measured by the ultrasonic array probe (4) after passing through the preamplifier (7) and the bandpass filter (8). The control computer (10) equipped with signal acquisition and processing software is responsible for acquiring and storing the signal from the signal acquisition card (9), and simultaneously controlling the two-dimensional laser scanning galvanometer (11) and performing imaging processing. The two-dimensional laser scanning galvanometer (11) is used to control the relative movement of the laser beam on the surface of the metal insert of the insulator under test, so as to realize the scanning of the entire interface.

2. The detection system of claim 1, wherein: Under the instruction of the control computer (10) equipped with signal acquisition and processing software, the two-dimensional laser scanning galvanometer (11) performs a 360-degree automatic scan of the insulator through the reflection of the galvanometer group; after all data acquisition is completed, the data is extracted along the axial direction to form the data matrix required for full-focus imaging and perform imaging calculation.

3. The detection method of the laser phased array ultrasonic composite detection system for internal interface defects of a metal insert of a GIS insulator of claim 1, characterized in that, Includes the following steps: Step 1: Install the detection system using a reflective arrangement scheme, placing the ultrasonic excitation end and detection end on the two sides of the metal insert respectively; first, adjust the fiber-coupled laser focusing lens (3) and the two-dimensional laser scanning galvanometer (11) to align the pulsed laser with one side of the metal insert, while attaching the ultrasonic array probe (4) to the other side of the metal insert; then adjust the relative positions of the fiber-coupled laser focusing lens (3), the ultrasonic array probe (4) and the two-dimensional laser scanning galvanometer (11) so that the incident area of ​​the pulsed laser and the detection area of ​​the ultrasonic array probe (4) spatially coincide, adjust to the initial scanning position and set the system parameters; Step 2: Based on the structural dimensions of the test piece, set the two-dimensional scanning area along the circumferential and axial directions and the scanning step spacing, and plan the reciprocating scanning array path of the laser spot to prepare for subsequent point-by-point ultrasonic excitation and interface reflection ultrasonic full matrix data acquisition. Step 3: The control computer (10) equipped with signal acquisition and processing software drives the two-dimensional laser scanning galvanometer (11) to scan and excite ultrasonic waves at the initial position; when the ultrasonic waves propagate to the internal interface, they generate near total reflection by utilizing the huge acoustic impedance difference between the defect and the metal medium, and form a difference in reflected energy with the partial transmission at the defect-free junction; the ultrasonic array probe (4) synchronously acquires the time-domain signals of the reflected echoes containing the above-mentioned energy difference characteristics at each scanning point, and sequentially constructs the full matrix signal data of the interface reflected ultrasonic waves; Step 4: The control computer (10) equipped with signal acquisition and processing software receives the interface reflection ultrasound full matrix signal data synchronously acquired by the ultrasound array probe (4); then, the data is sequentially subjected to translation alignment, digital filtering and normalization preprocessing operations to eliminate interference noise and unify the signal reference. Finally, the processed interface reflection ultrasound full matrix data is stored in the control computer equipped with signal acquisition and processing software to provide a data source for subsequent imaging. Step 5: The control computer (10) equipped with signal acquisition and processing software drives the two-dimensional laser scanning galvanometer (11) to move to the next detection position according to the scanning step interval set in Step 2, and repeats Step 3 and Step 4 in a loop until all the pre-planned two-dimensional scanning areas are traversed, and all interface reflection ultrasound full matrix signal data of the entire detection interface are acquired and stored. Step 6: All acquired scanning data are classified and extracted according to the step position, and then processed centrally using the full focusing algorithm; The full-focusing algorithm is based on the principle of delay summation and wave superposition. It grids the predefined region of interest and calculates the acoustic path delay time from the array element to each grid pixel. By extracting the corresponding amplitude of each grid point in the entire echo signal and performing time-delay superposition focusing, a high-resolution interface full-focusing image containing the defect location and size is generated, thereby realizing the accurate evaluation of internal defects.

4. The detection method according to claim 3, characterized in that: When inspecting the epoxy resin-metal insert interface, the pulsed laser (1) emits a Gaussian pulsed laser beam that reaches the fiber-coupled laser focusing lens (3) via the optical fiber (2). The focused pulsed spot is irradiated onto the metal insert side surface of the insulator by the two-dimensional laser scanning galvanometer (11), and multimode ultrasonic waves (5) are excited inside the metal insert. The defects (6) inside the insulator interface reflect the multimode ultrasonic waves and propagate to the metal insert side, thereby forming local ultrasonic signal characteristics on the opposite side of the laser excitation surface of the metal insert of the insulator under test. The out-of-plane displacement ultrasonic signal of this area is collected by the ultrasonic array probe (4) to realize the detection at this position. The fiber-coupled laser focusing lens (3) and the ultrasonic array probe (4) are scanned and collected by the two-dimensional laser scanning galvanometer (11), thus realizing the detection of the epoxy resin-metal insert interface quality of the insulator.

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