Coating under metal substrate damage detection device and method based on multi-frequency eddy current excitation and magnetic field detection

Abstract

The application provides a coating-under metal base damage detection device and method based on multi-frequency eddy current excitation and magnetic field detection, which comprises a multi-frequency eddy current excitation signal generator, an excitation coil, a magnetic field data collector, a linear array magnetic field detection sensor and a data processing module and a display, and the linear array magnetic field detection sensor is located in the excitation coil; the detection method comprises selecting a frequency gear for detection, acquiring magnetic field data under multiple excitation frequencies, performing three-dimensional reconstruction on magnetic field data graphs obtained by scanning under all frequencies, obtaining a three-dimensional image of a measured part, and analyzing damages shown in the image. The application can acquire damage data under multiple excitation frequencies through one scanning, can realize nondestructive detection and analysis of metal base cracks, corrosion and other damages without removing an organic coating or a thin metal covering layer on the surface of a metal material, and has the advantage of high detection efficiency.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology, specifically relating to a device and method for detecting damage to a metal substrate under a coating based on multi-frequency eddy current excitation and magnetic field detection.

[0002] Background Techniques

[0003] Alternating current can generate eddy currents on the surface of metal materials. When cracks or corrosion damage exist on the metal surface, the eddy currents change, and the magnetic field generated by the eddy currents also changes. Detecting these changes in the magnetic field generated by the eddy currents using a magnetic field sensor can determine damage to the surface and subsurface of the metal material. However, existing eddy current excitation detection devices all use a single frequency for excitation. Each acquired magnetic field data is generated by a single frequency excitation, resulting in low damage detection efficiency, a tendency to miss damage on the workpiece, and a long process time required to determine the appropriate test parameters for different samples and damage types. Therefore, it is necessary to provide an eddy current magnetic field detection device and method that can improve damage detection efficiency and accuracy. More importantly, existing eddy current excitation detection methods cannot accurately and quickly determine the depth range of the damage. Summary of the Invention

[0004] The purpose of this invention is to provide a device and method for detecting damage to metal substrates under coatings based on multi-frequency eddy current excitation and magnetic field detection, which has high damage detection efficiency and high detection accuracy.

[0005] The technical solution adopted in this invention is as follows.

[0006] A device for detecting damage to a coated metal substrate based on multi-frequency eddy current excitation and magnetic field detection includes a multi-frequency eddy current excitation signal generator, an excitation coil, a magnetic field data acquisition unit, a linear array magnetic field detection sensor, a data processing module, and a display. The linear array magnetic field detection sensor is fixedly connected to the excitation coil and located within the excitation coil. The multi-frequency eddy current excitation signal generator generates a multi-frequency excitation signal and forms a magnetic field at the measured location, simultaneously generating a frequency marker signal and transmitting it synchronously to the magnetic field data acquisition unit. The linear array magnetic field detection sensor detects magnetic field data at different excitation frequencies, records and extracts the magnetic field data at different excitation frequencies, and transmits the magnetic field data to the magnetic field data acquisition unit. The magnetic field data acquisition unit acquires the magnetic field data and the frequency marker signal, matches and stores the magnetic field data and the frequency marker signal, and feeds it back to the data processing module. The data processing module generates a magnetic field data graph from the read magnetic field data and outputs it.

[0007] In this invention, the multi-frequency excitation signal includes a first frequency emitted during a first millisecond time period T1, a second frequency emitted during a second millisecond time period T2, and so on during a K-millisecond time period T... K The Kth frequency emitted within the range has a total duration of all millisecond-level time intervals controlled within one second; the detection thickness range corresponding to the first frequency is 0-h1 mm, the detection thickness range corresponding to the second frequency is 0-h2 mm, and the detection thickness range corresponding to the Kth frequency is 0-h... K mm, 0mm indicates the detection reference surface, h1 mm indicates the depth h below the detection reference surface. K The position of mm, h1 < h2 < h K .

[0008] Preferably, the linear array magnetic field detection sensor is a giant magnetoresistive sensor or a tunnel magnetoresistive sensor.

[0009] The invention also includes a position sensor installed on the excitation coil. The position sensor is used to acquire the position of the detection part in real time and feed the position data back to the magnetic field data acquisition unit. The magnetic field data acquisition unit matches the position information with the magnetic field data and frequency marker signal.

[0010] In this invention, when the metal substrate is aluminum alloy, the corresponding frequency range is 1kHz-40kHz, and each frequency range belongs to an arithmetic sequence; when the metal substrate is carbon steel, the corresponding frequency range is 0.5kHz-30kHz, and each frequency range belongs to an arithmetic sequence.

[0011] A detection method using the aforementioned metal substrate damage detection device includes the following steps:

[0012] Step 1: Place the excitation coil and linear array magnetic field detection sensor at the starting position on the surface of the metal substrate to be tested;

[0013] Step 2: Based on the material of the metal substrate being tested, set the frequency range of the excitation signal of the multi-frequency eddy current excitation signal generator;

[0014] Step 3: Select a frequency range containing K frequency bands, and move the excitation coil and linear array magnetic field detection sensor at a constant speed along the detection path to complete the detection of thickness ranges 0-h1 mm, 0-h2 mm, ... 0-h k mm scan;

[0015] A single scan acquires magnetic field data for multiple frequency ranges corresponding to thickness intervals. The first frequency range corresponds to a thickness interval of 0-h1 mm, the second frequency range corresponds to a thickness interval of 0-h2 mm, and the Kth frequency range corresponds to a thickness interval of 0-h... K mm;

[0016] Step 4: Perform three-dimensional reconstruction on the magnetic field data obtained from scanning at all frequencies to obtain a three-dimensional image of the tested area, and analyze the damage shown in the three-dimensional image.

[0017] The damage analysis process in step 4 is as follows:

[0018] If no damage features are shown in the magnetic field data graph corresponding to the first frequency, it means that the first region with a thickness range of 0-h1mm is undamaged.

[0019] If no damage characteristics are shown in the magnetic field data graph corresponding to the second frequency, it means that the second region with a thickness range of 0-h2mm is undamaged.

[0020] If no damage characteristics are shown in the magnetic field data graph corresponding to the K-1 frequency range, it indicates that the thickness range is 0-h. K-1 mm of the h K-1 No damage to the area;

[0021] If the magnetic field data graph corresponding to the Kth frequency shows damage characteristics, it indicates that the damage exists within the thickness range.

[0022] h K-1 ~h K The area is mm.

[0023] Beneficial effects: By adopting the solution of the present invention, damage data under multiple excitation frequencies can be obtained in a single scan. It can achieve non-destructive testing and analysis of damage such as cracks and corrosion in metal substrates without removing organic coatings or thin metal coverings on the surface of metal materials, and has the advantage of high detection efficiency. More importantly, the solution of the present invention can accurately and quickly determine the depth range of the damage, and can identify damage with a depth range of 0.2-2mm. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a coating-based metal substrate damage detection device based on multi-frequency eddy current excitation and magnetic field detection in the embodiment.

[0025] Figure 2 This is a flowchart of the metal substrate damage detection device based on multi-frequency eddy current excitation and magnetic field in the embodiment.

[0026] Figure 3 This is a graph showing the magnetic field data acquired by the detection device at different frequency levels in the embodiment.

[0027] Figure 4 This is a schematic diagram of the three-dimensional image of the measured part obtained after three-dimensional reconstruction. Detailed Implementation

[0028] The present invention will be further described below with reference to the embodiments and accompanying drawings. Example

[0029] A device for detecting damage to a coated metal substrate based on multi-frequency eddy current excitation and magnetic field detection, such as... Figure 1 and Figure 2 As shown, the system includes a multi-frequency eddy current excitation signal generator, an excitation coil 4, a magnetic field data acquisition unit, a linear array magnetic field detection sensor 5, a data processing module, and a display 2. The linear array magnetic field detection sensor 5 is fixedly connected to the excitation coil 4 and located inside the excitation coil 4. The multi-frequency eddy current excitation signal generator and the magnetic field data acquisition unit are installed in the same housing 1. The multi-frequency eddy current excitation signal generator generates a multi-frequency excitation signal and forms a magnetic field at the measured location, and simultaneously generates a frequency marker signal, which is transmitted synchronously to the magnetic field data acquisition unit. The linear array magnetic field detection sensor 5 detects magnetic field data at different excitation frequencies, records and extracts the magnetic field data at different excitation frequencies, and transmits the magnetic field data to the magnetic field data acquisition unit. The magnetic field data acquisition unit acquires the magnetic field data and the frequency marker signal, matches and stores the magnetic field data and the frequency marker signal, and feeds it back to the data processing module. The data processing module generates a magnetic field data graph from the read magnetic field data and outputs it. The linear array magnetic field detection sensor 5 is a giant magnetoresistive sensor. In use, the linear array magnetic field detection sensor 5 and the excitation coil 4 are placed together on the surface of the workpiece 3 to be measured. During detection (scanning), the operator manipulates the linear array magnetic field detection sensor 5 and the excitation coil 4 along the detection path. Figure 1 The device moves at a constant speed (in the direction indicated by arrow 6) to detect damage 7 (damage) on the metal substrate.

[0030] The multi-frequency eddy current excitation signal generator can continuously generate multiple different frequencies within a second-level time period. It can be a programmable signal generator, and these required frequency levels can be set by those skilled in the art through programming. In this embodiment, the multi-frequency excitation signal generated by the multi-frequency eddy current excitation signal generator includes a first frequency (40kHz) emitted in the first millisecond-level time period T1 (0-100ms), a second frequency (30kHz) emitted in the second millisecond-level time period T2 (100-200ms), ... and a fourth frequency (10kHz) emitted in the fourth millisecond-level time period T4 (300-400ms). The total duration of all millisecond-level time periods (400ms) is within one second. The detection thickness range corresponding to the first frequency is 0-h1 mm (h1=0.4mm), the detection thickness range corresponding to the second frequency is 0-h2 mm (h2=0.8mm), and the detection thickness range corresponding to the fourth frequency is 0-h... Kmm (h4=1.6mm), the position of 0mm represents the detection reference surface, and the position of h1 mm represents the depth h below the detection reference surface. K The position of mm, h1 < h2 < h K .

[0031] In this embodiment, a position sensor is also included, which is installed on the excitation coil 4. The position sensor is used to obtain the position of the detection part in real time (the detection path is pre-calibrated with coordinate information) and feed the position data back to the magnetic field data acquisition unit. The magnetic field data acquisition unit matches its position information with magnetic field data and frequency marker signal.

[0032] In this invention, the frequency of the multi-frequency eddy current excitation signal generator is adjustable, and each frequency level belongs to an arithmetic sequence (0.5kHz, 1kHz, 1.5kHz, 1.5kHz...100kHz), with a frequency range of 0.5kHz-100kHz.

[0033] A detection method using the metal substrate damage detection device in this embodiment includes the following steps:

[0034] Step 1, as follows Figure 1 As shown, the excitation coil 4 and the linear array magnetic field detection sensor 5 are placed at the starting position on the surface of the metal substrate 3 to be tested;

[0035] Step 2: Based on the material of the metal substrate being tested, set the excitation signal frequency of the multi-frequency eddy current excitation signal generator;

[0036] Step 3: Select a frequency range (containing K frequency bands; theoretically, the more frequency bands, the smaller the difference in thickness intervals). Move the excitation coil 4 and the linear array magnetic field detection sensor 5 at a constant speed along the detection path to complete the thickness intervals of 0-h1mm, 0-h2mm, ..., 0-h k mm scan; Figure 3 In the diagram, the gray area represents the morphology of the damaged plane obtained from the scan, the X-axis of the two-dimensional coordinate system represents the length, the Y-axis represents the width, and the curve represents the cross-sectional data curve of the damaged magnetic field strength.

[0037] Step 4: Perform three-dimensional reconstruction on the magnetic field data obtained from scanning at all frequencies to obtain a three-dimensional image of the measured part (e.g., Figure 4 As shown in the figure, the damage displayed in the 3D image is analyzed. This example combines... Figure 3 Analysis shows that the magnetic field data graphs corresponding to the first to fourth frequencies all show damage characteristics, indicating that the area with a thickness range of 0-h4 mm is damaged.

[0038] In practical applications, the damage analysis process in step 4 is as follows:

[0039] If no damage features are shown in the magnetic field data graph corresponding to the first frequency, it means that the first region with a thickness range of 0-h1mm is undamaged.

[0040] If no damage characteristics are shown in the magnetic field data graph corresponding to the second frequency, it means that the second region with a thickness range of 0-h2mm is undamaged.

[0041] If no damage characteristics are shown in the magnetic field data graph corresponding to the K-1 frequency range, it indicates that the thickness range is 0-h. K-1 mm of the h K-1 No damage to the area;

[0042] If the magnetic field data graph corresponding to the Kth frequency shows damage characteristics, it indicates that the damage exists within the thickness range.

[0043] h K-1 ~h K The area in mm;

[0044] If the magnetic field data map corresponding to the first frequency shows damage characteristics, it indicates that there is damage in the area with a thickness range of 0-h1mm or below that area. Further analysis of the magnetic field data map corresponding to the next frequency is required until the depth region of the damage is found.

[0045] This approach allows for the acquisition of damage data at multiple excitation frequencies in a single scan. It enables non-destructive testing and analysis of damage such as cracks and corrosion in metal substrates without removing organic coatings or thin metal overlays (0-3 mm thick) from the surface of metal materials, offering the advantage of high detection efficiency. More importantly, this approach can accurately and quickly determine the depth range of the damage.

Claims

1. A device for detecting damage to a metal substrate under a coating based on multi-frequency eddy current excitation and magnetic field detection, characterized in that: The device comprises a multi-frequency eddy current excitation signal generator, an excitation coil, a magnetic field data collector, a linear array magnetic field detection sensor and a data processing module and display, the linear array magnetic field detection sensor is fixedly connected to the excitation coil and located in the excitation coil; wherein the multi-frequency eddy current excitation signal generator is used to generate a multi-frequency excitation signal and form a magnetic field at the measured position, and synchronously generate a frequency marker signal and transmit the marker signal to the magnetic field data collector; the linear array magnetic field detection sensor is used to detect the magnetic field data under different excitation frequencies, and record and extract the magnetic field data under different excitation frequencies, and transmit the magnetic field data to the magnetic field data collector; the magnetic field data collector is used to acquire the magnetic field data and the frequency marker signal, match the magnetic field data with the frequency marker signal, store and feed back to the data processing module; the data processing module is used to generate a magnetic field data graph from the read magnetic field data and output the graph. The multi-frequency excitation signal includes a first frequency emitted in a first millisecond period T1, a second frequency emitted in a second millisecond period T2,..., and a Kth frequency emitted in a Kth millisecond period T K K; the total duration of all the millisecond periods is controlled within one second; the detection thickness interval corresponding to the first frequency is 0-h1 mm, the detection thickness interval corresponding to the second frequency is 0-h2 mm, and the detection thickness interval corresponding to the Kth frequency is 0-h K K mm; the position at 0 mm represents a detection reference surface, the position at h1 mm represents a position with a depth of h1 mm below the detection reference surface, and the position at h2 mm represents a position with a depth of h2 mm below the detection reference surface K ; h1 K ​ The device further comprises a position sensor installed on the excitation coil, which is used to acquire the position of the detection position in real time and feed back the position data to the magnetic field data collector, and the magnetic field data collector matches the position information with the magnetic field data and the frequency marker signal.

2. The metal matrix damage detection apparatus of claim 1, wherein: The linear array magnetic field detection sensor is a giant magnetoresistance sensor or a tunnel magnetoresistance sensor.

3. The metal matrix damage detection apparatus of claim 2, wherein: When the metal base is an aluminum alloy, the corresponding frequency is 1 kHz-50 kHz, and the frequencies of each gear are arranged in equal steps; when the metal base is a carbon steel, the corresponding frequency is 0.5 kHz-50 kHz, and the frequencies of each gear are arranged in equal steps.

4. A method of detecting a defect in a metal matrix using the apparatus of claim 3, the method comprising the steps of: The device comprises: Step 1: placing the excitation coil and the linear array magnetic field detection sensor at the starting position on the surface of the measured metal base; Step 2: setting the excitation signal frequency of the multi-frequency eddy current excitation signal generator according to the material of the measured metal base; Step 3, select the frequency range, containing K frequency bands, along the detection path, uniform speed moving excitation coil and linear array magnetic field detection sensor, complete the scanning of thickness interval 0-h1 mm, 0-h2 mm…0-h k mm Step 4: three-dimensional reconstruction is performed on the magnetic field data graphs obtained by scanning under all frequencies to obtain a three-dimensional image of the measured position, and the damage shown in the three-dimensional image is analyzed.

5. The method of claim 4, wherein the metal matrix damage detection apparatus is configured to detect the presence of a defect in the metal matrix by detecting a change in the electrical impedance of the metal matrix. The process of analyzing the damage in step 4 is as follows: If the magnetic field data graph corresponding to the first frequency does not show damage characteristics, it indicates that the first region with a thickness interval of 0-h1 mm is damage-free; If the magnetic field data graph corresponding to the second frequency does not show damage characteristics, it indicates that the second region with a thickness interval of 0-h2 mm is damage-free; If the K-1th gear frequency corresponding to the magnetic field data diagram does not show damage characteristics, it means that the thickness interval is 0-h K-1 mm of the h K-1 region is damage-free; If the Kth gear frequency corresponds to a magnetic field data graph showing a damage feature, it indicates that the damage exists in the region with a thickness interval of h K-1 ~ h K mm.

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