Nondestructive testing device and method for magnetic stealth coating defects and non-metal base material damage

Abstract

The invention relates to the technical field of non-destructive testing, and discloses a non-destructive testing device and method for magnetic stealth coating defects and non-metal base material damage, which are used for surface / internal defect detection of a magnetic stealth coating and non-metal base material damage integrated detection, and are combined with multi-physical field fusion sensing including eddy current, magnetic leakage and residual magnetism. Through an intelligent imaging algorithm, multi-physical field signals of coating defects and matrix damage are synchronously collected. A shielding cover and an active demagnetization unit are arranged, mutual interference of magnetic leakage and residual magnetism signals is restrained, and the signal-to-noise ratio is increased. Through multi-physical field sensing fusion and anti-interference magnetic circuit design, the problem of synchronous detection of magnetic coating defects and non-metal base material damage is solved, real-time defect imaging is achieved, and a high-precision nondestructive evaluation method is provided for full-life-cycle health management of stealth materials.

Description

Technical Field

[0001] The present invention relates to the technical field of non-destructive testing, and in particular to a non-destructive testing device and method for detecting defects in a magnetic stealth coating and damage to a non-metallic substrate. Background Art

[0002] In modern warfare, air superiority is a crucial factor in determining victory or defeat. As core equipment in the fight for air superiority, fighter aircraft rely heavily on advanced stealth capabilities for their survivability and penetration effectiveness. Radar stealth technology is particularly crucial, driving the continued development and application of efficient, lightweight, and durable high-performance stealth coatings. However, during high-speed flight, fighter aircraft are subjected to severe vibration loads, drastic temperature fluctuations, and high-speed airflow. These defects can significantly degrade the coating's electromagnetic properties, leading to a dramatic increase in its radar cross section (RCS), severely weakening the aircraft's stealth performance and directly threatening its combat effectiveness and flight safety. Therefore, conducting regular or on-demand, rapid, and highly reliable nondestructive testing (NDT) on stealth coatings on in-service fighter aircraft to promptly detect and assess coating damage is crucial for ensuring their continued stealth capability and combat readiness.

[0003] Currently, in the research and application of non-destructive testing technologies for stealth coatings and substrates, non-contact, high-precision, imaging technologies represented by infrared thermal imaging and eddy current testing have become a hot topic. However, existing detection technologies for stealth coatings mostly focus on the coating itself, and lack mature solutions for simultaneous and effective detection of internal damage to non-metallic substrates (such as composite fuselage / wing structures) that support stealth coatings. Damage to the substrate (such as fatigue cracks and delamination) can also undermine structural integrity and stealth performance, but its detection often requires additional specialized equipment and methods. Therefore, there is an urgent need to provide technical means for comprehensive, rapid, and reliable assessment of the overall integrity of stealth materials. Summary of the Invention

[0004] To solve the above problems, the present invention provides a non-destructive detection device for magnetic stealth coating defects and non-metallic substrate damage. The present invention is implemented as follows:

[0005] A nondestructive testing device for defects in magnetic stealth coatings and damage to non-metallic substrates, comprising an intelligent multifunctional electromagnetic detector 10 and a dedicated electromagnetic detection probe 20. The intelligent multifunctional electromagnetic detector 10 is configured to have at least three detection functions: eddy current, magnetic flux leakage, and residual magnetism. It is also equipped with a multi-signal synchronous processing and imaging unit.

[0006] The dedicated electromagnetic detection probe 20 includes a dual magnetic roller module 100, an eddy current coil module 200, a magnetic sensor module 300, an active degaussing module 400 and a magnetic shielding unit 500;

[0007] The dual magnetic roller module 100 includes a first magnetic roller 101, a second magnetic roller 102 and a U-shaped magnetic yoke 103;

[0008] The first magnetic roller 101 and the second magnetic roller 102 are arranged at intervals along the travel direction of the probe and are fixedly connected by the U-shaped magnetic yoke 103;

[0009] The magnetic poles of the first magnetic roller 101 are arranged as an inner core N pole and an outer surface S pole, and the magnetic poles of the second magnetic roller 102 are arranged as an inner core S pole and an outer surface N pole;

[0010] The magnetic pole of the U-shaped magnetic yoke 103 at the connection end with the first magnetic roller 101 is configured as an N pole, and the magnetic pole of the U-shaped magnetic yoke 103 at the connection end with the second magnetic roller 102 is configured as an S pole;

[0011] The eddy current coil module 200 is disposed between the first magnetic roller 101 and the second magnetic roller 102 and includes an array excitation coil 201 and a differential receiving coil 202;

[0012] The magnetic sensor module 300 includes a magnetic leakage sensor array 301 and a residual magnetic sensor array 302;

[0013] The magnetic flux leakage sensor array 301 is disposed at a first predetermined distance behind the second magnetic roller 102 and is used to detect the dynamic magnetic flux leakage field in real time;

[0014] The residual magnetic sensor array 302 is arranged at a second predetermined distance behind the magnetic leakage sensor array 301 and is used to detect the static residual magnetic field distribution;

[0015] The active degaussing module 400 is arranged between the magnetic flux leakage sensor array 301 and the residual magnetism sensor array 302, and includes a reverse pulse coil 401 and a magnetic field monitoring unit 402, which is used to eliminate the residual magnetic field in the residual magnetism detection area at a predetermined time;

[0016] The magnetic field monitoring unit 402 feeds back the residual magnetic field strength of the residual magnetic detection area to be detected to the intelligent multifunctional electromagnetic detector 10 in real time;

[0017] The magnetic shielding unit is configured as a shielding cover structure, covering the dual magnetic roller module 100 , the eddy current coil module 200 and the magnetic flux leakage sensor array 301 .

[0018] The present invention also discloses a non-destructive detection method for defects in magnetic stealth coatings and damage to non-metallic substrates, which uses the above-mentioned device to perform time-sharing within a single detection cycle:

[0019] S1, magnetic coating

[0020] The dual magnetic roller module 100 is used to magnetize the stealth material coating 601 of the current test area, so that the stealth material coating 601 is in a saturated magnetization state;

[0021] S2. Eddy current testing

[0022] Starting the eddy current coil module 200 in the S1 magnetization state to obtain a defect eddy current response signal of the stealth material coating 601;

[0023] S3, magnetic flux leakage detection

[0024] Maintaining the S1 magnetization state, collecting defect magnetic leakage detection signals of the stealth material coating 601 through the magnetic leakage sensor array 301;

[0025] S4. Demagnetize the current area to be tested

[0026] The detection device moves to the next area to be tested according to the preset step, so that the active demagnetization module 400 covers the current area to be tested, and the active demagnetization module 400 is started to quickly eliminate the residual magnetic field in the current area to be tested;

[0027] S5. Residual magnetism detection

[0028] Measuring the damage residual magnetism detection signal of the stealth material matrix 602 by the residual magnetism sensor array 302;

[0029] S6, Multi-signal Fusion Imaging

[0030] The intelligent multifunctional electromagnetic detector 10 uses a preset algorithm to fuse and analyze the acquired defect eddy current detection signal and leakage magnetic detection signal of the stealth material coating 601 and the damaged residual magnetic detection signal of the stealth material matrix 602, and outputs an imaging result diagram of the integrity information of the stealth material in the test area in real time.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention innovatively combines eddy current, magnetic flux leakage, and residual magnetism detection technologies. By leveraging the complementary advantages of multimodal detection methods, it can not only comprehensively capture subtle surface defects but also effectively detect deep damage, significantly improving the coverage and accuracy of defect detection and overcoming the limitations of traditional single detection methods.

[0033] Second, the use of dynamic demagnetization technology and intelligent scanning solutions realizes a fast and continuous automated inspection process. The innovative demagnetization design ensures the continuity of the inspection process, and the flexible bonding structure perfectly adapts to various complex curved surfaces, improving the feasibility of application.

[0034] 3. Using advanced data fusion algorithms and intelligent analysis technology, we build a complete automated inspection system that generates intuitive defect imaging results in real time and automatically completes defect classification and evaluation, reducing the impact of human factors and improving the objectivity and consistency of inspection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the examples of the present invention or the technical solutions in the prior art or the drawings required for the description of the prior art, a brief introduction is given. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0036] Figure 1 Schematic diagram of the detection method of the present invention.

[0037] Figure 2 Schematic diagram of the detection working condition of an embodiment of the present invention.

[0038] Figure 3 Schematic diagram of the structure of a nondestructive testing device according to an embodiment of the present invention.

[0039] Figure 4 for Figure 3 Structural diagram from another perspective (module decomposition).

[0040] Figure 5 Schematic diagram of the structure of the dual magnetic roller module. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention.

[0042] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0043] Aircraft skin stealth coatings are typically made of conductive materials that absorb or scatter radar waves, reducing the aircraft's potential for detection. During high-speed flight, the aircraft's body temperature rises, posing a significant challenge to the coating's stability. To ensure the stealth skin remains operationally ready, it must be inspected for defects and maintained accordingly. Existing inspection methods typically rely on a single technique, making it difficult to achieve comprehensive inspection requirements.

[0044] The present invention discloses a nondestructive testing device for detecting defects in magnetic stealth coatings and damage to non-metallic substrates, which is used to detect defects in ferromagnetic stealth coatings, especially coatings with non-metallic substrates. Specifically, the device comprises an intelligent multifunctional electromagnetic detector 10 and a dedicated electromagnetic detection probe 20.

[0045] The intelligent multifunctional electromagnetic detector 10 is configured to have at least three detection functions of eddy current, magnetic flux leakage and residual magnetism, and is equipped with a multi-signal synchronous processing and imaging unit;

[0046] The dedicated electromagnetic detection probe 20 includes a dual magnetic roller module 100, an eddy current coil module 200, a magnetic sensor module 300, an active degaussing module 400 and a magnetic shielding unit 500;

[0047] The dual magnetic roller module 100 is used for magnetization and magnetic conduction. It includes a first magnetic roller 101, a second magnetic roller 102 and a U-shaped magnetic yoke 103;

[0048] The first magnetic roller 101 and the second magnetic roller 102 are arranged at intervals along the travel direction of the probe and are fixedly connected by the U-shaped magnetic yoke 103; the magnetic poles of the first magnetic roller 101 are configured as an inner core N pole and an outer surface S pole, and the magnetic poles of the second magnetic roller 102 are configured as an inner core S pole and an outer surface N pole;

[0049] The magnetic pole of the U-shaped magnetic yoke 103 at the connection end with the first magnetic roller 101 is configured as an N pole, and the magnetic pole of the U-shaped magnetic yoke 103 at the connection end with the second magnetic roller 102 is configured as an S pole;

[0050] The two magnetic rollers are configured with opposite inner and outer magnetic poles, and adjacent magnetic rollers have opposite poles, forming a closed magnetic circuit that enhances magnetization sensitivity to minute surface defects in the coating. The U-shaped magnetic yoke efficiently guides magnetic lines of force through the workpiece, enabling precise location of defects in ferromagnetic materials. The roller structure supports continuous rolling inspection of the probe on curved surfaces or complex substrates. The dual magnetic roller module utilizes a magnetic-mechanical collaborative design to achieve high-strength, mobile magnetization of ferromagnetic equipment.

[0051] The eddy current coil module 200 is used for near-surface defect detection and is arranged between the first magnetic roller 101 and the second magnetic roller 102, and includes an array excitation coil 201 and a differential receiving coil 202; when the magnetic roller magnetizes the stealth material coating 601 and reaches a saturated magnetization state, the eddy current coil module 200 synchronously collects the eddy current disturbance signal caused by the defect.

[0052] In this embodiment, the detection sensitivity is further enhanced by the following steps:

[0053] Multi-frequency excitation optimization: The arrayed excitation coil 201 can emit multiple characteristic frequencies simultaneously or in time-sharing mode, corresponding to defect detection at different depths under the coating;

[0054] Differential signal processing: The receiving coil 202 adopts a differential layout to suppress common mode noise and extract the eddy current phase offset caused by defects;

[0055] Magnetic eddy current collaborative analysis: Combined with the leakage magnetic field distribution data after the dual magnetic roller module is magnetized, magnetic-electric coupling compensation is performed on the eddy current signal to improve the signal-to-noise ratio of small cracks.

[0056] The magnetic sensor module 300 is used to obtain the leakage magnetic and residual magnetic signals of the area to be measured, and includes a leakage magnetic sensor array 301 and a residual magnetic sensor array 302;

[0057] The magnetic flux leakage sensor array 301 is arranged at a first predetermined distance behind the second magnetic roller 102. In this embodiment, a high-sensitivity magnetic flux leakage detection sensor is used to capture dynamic magnetic field leakage signals caused by defects in a moving state in real time.

[0058] The residual magnetic sensor array 302 is arranged at a second predetermined distance behind the magnetic flux leakage sensor array 301. In this embodiment, a giant magnetoresistive sensor is used and arranged behind the magnetic flux leakage sensor to detect the static residual magnetic field after the active demagnetization module eliminates the residual magnetic field, so as to identify deep defects.

[0059] The active demagnetization module 400 is arranged between the leakage magnetic sensor array 301 and the residual magnetic sensor array 302, and includes a reverse pulse coil 401 and a magnetic field monitoring unit 402, which is used to eliminate the residual magnetic field in the residual magnetic detection area at a predetermined time; in this embodiment, the active demagnetization module 400 is arranged to be connected in anti-phase series with the excitation coil and the reverse pulse coil, and equal reverse current is passed through to generate a forward incident magnetic field and a local reverse shielding magnetic field, and the magnetic fields cancel each other at the axis center, thereby avoiding the residual magnetic field interfering with subsequent detection.

[0060] The reverse shielding magnetic field forms a uniform field in the detection area, optimizing the uniformity of the magnetic field distribution in the depth direction of the material.

[0061] By jointly analyzing the dynamic leakage magnetic field signal and the static residual magnetic field, a three-dimensional characteristic model of the defect is formed to achieve comprehensive detection of the coating and substrate.

[0062] Furthermore, a magnetic field monitoring unit 402 is provided to provide real-time feedback of the residual magnetic field strength of the residual magnetism detection area to be inspected to the intelligent multifunctional electromagnetic detector 10; the magnetic field monitoring unit senses and collects the residual magnetic field strength in real time, and works in conjunction with the central control system to determine whether the residual magnetic field meets the magnetic field strength of the residual magnetism detection, and then controls the residual magnetic field strength through the demagnetization effect applied by the active demagnetization module.

[0063] Furthermore, a magnetic shielding unit is provided, employing a shielding cover structure, covering the dual magnetic roller module 100, eddy current coil module 200, and magnetic flux leakage sensor array 301. The magnetic shielding unit suppresses stray magnetic field interference. In this embodiment, the shielding cover is coated on the outer surfaces of the dual magnetic roller module, eddy current coil module, and magnetic flux leakage sensor array. It adopts a multi-layer composite structure with an anti-saturation outer layer, a high-shielding inner layer, and a gradient layer design at the junction to prevent magnetic leakage. The outer layer can be made of an FeCo-based amorphous alloy, the middle layer of a nanocrystalline alloy, and the inner layer of an annealed μ alloy.

[0064] Since the coating and substrate should theoretically bond well, any cracks, debonding, flaking, or fiber breakage within the substrate caused by vibration or abrasion during flight can be memorized by the surface magnetic coating. Therefore, by comparing the magnetic images of different defects or discontinuities, it is possible to quickly detect the integrity of the stealth materials of in-service aircraft or ships. Based on this, a non-destructive detection method for magnetic stealth coating defects and non-metallic substrate damage is implemented using the above-mentioned device, which is executed in a time-sharing manner within a single detection cycle:

[0065] S1, magnetic coating

[0066] The dual magnetic roller module 100 is used to magnetize the stealth material coating 601 of the current test area, so that the stealth material coating 601 is in a saturated magnetization state;

[0067] S2. Eddy current testing

[0068] Starting the eddy current coil module 200 in the S1 magnetization state to obtain a defect eddy current response signal of the stealth material coating 601;

[0069] S3, magnetic flux leakage detection

[0070] Maintaining the S1 magnetization state, collecting defect magnetic leakage detection signals of the stealth material coating 601 through the magnetic leakage sensor array 301;

[0071] S4. Demagnetize the current area to be tested

[0072] The detection device moves to the next area to be tested according to the preset step, so that the active demagnetization module 400 covers the current area to be tested, and the active demagnetization module 400 is started to quickly eliminate the residual magnetic field in the current area to be tested;

[0073] S5. Residual magnetism detection

[0074] Measuring the damage residual magnetism detection signal of the stealth material matrix 602 by the residual magnetism sensor array 302;

[0075] S6, Multi-signal Fusion Imaging

[0076] The intelligent multifunctional electromagnetic detector 10 uses a preset algorithm to fuse and analyze the acquired defect eddy current detection signal and leakage magnetic detection signal of the stealth material coating 601 and the damaged residual magnetic detection signal of the stealth material matrix 602, and outputs an imaging result diagram of the integrity information of the stealth material in the test area in real time.

[0077] Cross-verification of surface coating test results based on eddy current testing and magnetic flux leakage testing;

[0078] The residual magnetic field gradient obtained by residual magnetism detection is used to detect stress concentration areas and microcracks.

[0079] Combining signal processing, feature engineering, data fusion, machine learning, and image generation to build algorithms;

[0080] The eddy current detection signal and magnetic flux leakage detection signal of the stealth material coating and the damaged residual magnetism detection signal of the stealth material substrate are input, and a real-time imaging structure diagram is output to intuitively display the defect type, defect location, size, depth and other defect conditions of the coating and substrate.

[0081] The specific construction steps include:

[0082] S61, Signal Preprocessing and Synchronization

[0083] The three original signals are filtered separately to remove electromagnetic interference and environmental noise; ensure that the three signals are strictly synchronized in time and space, and then unify the signals of different dimensions to the same scale.

[0084] S62. Feature extraction of three signals

[0085] Eddy current signal characteristics include impedance amplitude / phase change, resonant frequency shift, and edge effect area characteristics;

[0086] The magnetic flux leakage signal characteristics include magnetic flux leakage, magnetic field gradient distribution, peak width and peak symmetry;

[0087] The residual magnetic signal characteristics include residual magnetic field intensity distribution, magnetic domain distortion characteristics, and local hysteresis loop parameters.

[0088] S63. Multimodal Data Fusion

[0089] Select feature-level fusion to extract the features of each signal and merge them into a high-dimensional feature vector, which is then input into the classification / regression model.

[0090] S64, Defect Identification and Quantification

[0091] The task is split into classification and regression. The classification task involves defect types, including cracks, corrosion, debonding, and inclusions; the regression task involves defect size, depth, and location. A lightweight deep learning model is selected for rapid identification to ensure real-time performance.

[0092] S65, real-time imaging generation

[0093] Perform pixel-level mapping to map the detection position to image coordinates, and convert defect parameters into pixel attributes. For example, different colors are used to display different defect types, with red representing cracks, yellow representing debonding, and brightness representing the severity of the defect. Contours are generated through the segmentation network to represent the defect shape.

[0094] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A non-destructive detection device for magnetic stealth coating defects and non-metallic substrate damage, characterized in that: It comprises an intelligent multifunctional electromagnetic detector (10) and a special electromagnetic detection probe (20), The intelligent multifunctional electromagnetic detector (10) is configured to have at least three detection functions of eddy current, magnetic flux leakage and residual magnetism, and is equipped with a multi-signal synchronous processing and imaging unit; The dedicated electromagnetic detection probe (20) comprises a dual magnetic roller module (100), an eddy current coil module (200), a magnetic sensor module (300), an active demagnetization module (400) and a magnetic shielding unit (500); The dual magnetic roller module (100) comprises a first magnetic roller (101), a second magnetic roller (102) and a U-shaped magnetic yoke (103); The first magnetic roller (101) and the second magnetic roller (102) are arranged at intervals along the travel direction of the probe and are fixedly connected via the U-shaped magnetic yoke (103); The magnetic pole configuration of the first magnetic roller (101) is inner core N pole-outer surface S pole, and the magnetic pole configuration of the second magnetic roller (102) is inner core S pole-outer surface N pole; The magnetic pole of the U-shaped magnetic yoke (103) at the connection end with the first magnetic roller (101) is configured as an N pole, and the magnetic pole of the U-shaped magnetic yoke (103) at the connection end with the second magnetic roller (102) is configured as an S pole; The eddy current coil module (200) is arranged between the first magnetic roller (101) and the second magnetic roller (102), and comprises an array excitation coil (201) and a differential receiving coil (202); The magnetic sensor module (300) comprises a magnetic leakage sensor array (301) and a residual magnetic sensor array (302); The magnetic flux leakage sensor array (301) is arranged at a first predetermined distance behind the second magnetic roller (102) and is used for real-time detection of a dynamic magnetic flux leakage field; The residual magnetic sensor array (302) is arranged at a second predetermined distance behind the magnetic flux leakage sensor array (301) and is used to detect static residual magnetic field distribution; The active demagnetization module (400) is arranged between the magnetic flux leakage sensor array (301) and the residual magnetism sensor array (302), and comprises a reverse pulse coil (401) and a magnetic field monitoring unit (402), and is used to eliminate the residual magnetic field of the residual magnetism detection area at a predetermined time; The magnetic field monitoring unit (402) feeds back the residual magnetic field strength of the residual magnetic detection area to be detected to the intelligent multifunctional electromagnetic detector (10) in real time; The magnetic shielding unit is configured as a shielding cover structure, covering the dual magnetic roller module (100), the eddy current coil module (200), and the magnetic flux leakage sensor array (301).

2. A non-destructive detection method for magnetic stealth coating defects and non-metallic substrate damage, using the device according to claim 1, characterized in that: Executed in a single detection cycle: S1, magnetic coating The stealth material coating (601) in the current area to be tested is magnetized by the dual magnetic roller module (100), so that the stealth material coating (601) is in a saturated magnetization state; S2. Eddy current testing Starting the eddy current coil module (200) in the S1 magnetization state to obtain a defect eddy current response signal of the stealth material coating (601); S3, magnetic flux leakage detection Maintaining the S1 magnetization state, collecting defect magnetic leakage detection signals of the stealth material coating (601) through the magnetic leakage sensor array (301); S4. Demagnetize the current area to be tested The detection device moves to the next area to be tested according to a preset step, so that the active demagnetization module (400) covers the current area to be tested, and the active demagnetization module (400) is started to quickly eliminate the residual magnetic field in the current area to be tested; S5. Residual magnetism detection Measuring a damage residual magnetism detection signal of the stealth material matrix (602) by using the residual magnetism sensor array (302); S6, Multi-signal Fusion Imaging The intelligent multifunctional electromagnetic detector (10) performs fusion analysis on the acquired defect eddy current detection signal and magnetic flux leakage detection signal of the stealth material coating (601) and the damaged residual magnetism detection signal of the stealth material substrate (602) through a preset algorithm, and outputs an imaging result diagram of the integrity information of the stealth material in the test area in real time.

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