Method and device for detecting buried depth of metal buried crack and medium

Abstract

The invention discloses a method and a device for detecting the burial depth of a metal burial crack and a medium. Relates to the field of electromagnetic nondestructive testing, and solves the problem of insufficient precision in quantitative calculation of the buried crack burial depth by using single-frequency excitation in the traditional alternating current electromagnetic detection technology. Firstly, pre-scanning is carried out through single frequency, preliminary positioning of the buried crack edge can be carried out by utilizing a magnetic field distortion characteristic generated by induced current bypassing at the crack edge, and then a frequency sweep alternating current excitation signal of which the frequency linearly changes along with time is applied to the preliminarily positioned edge. Induced current with different frequencies covers the whole range from the surface layer to the deep layer, due to the fact that a stable mapping relation exists between the excitation frequency of an alternating-current excitation signal and the crack burial depth, the induced current with the different frequencies is distributed at different depths through a frequency sweeping signal, the correlation between the frequency and the depth is converted into a quantifiable characteristic frequency-burial depth mapping relation, and the burial depth of the crack is obtained. And the practicability and the precision level of the alternating-current electromagnetic detection technology in deep defect identification are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic nondestructive testing, in particular to a metal buried crack depth detection method, device and medium. BACKGROUND

[0002] In the field of nondestructive testing of metal materials, alternating current electromagnetic detection technology is widely used in crack detection of metal components due to its convenient operation and rapid response.

[0003] However, the traditional alternating current electromagnetic detection technology has significant limitations in the detection of the depth of a metal buried crack: it uses a single fixed frequency excitation signal, which is limited by the skin effect and cannot balance the penetration depth and sensitivity of the detection. Specifically, although a low-frequency excitation signal can penetrate deep into the interior of a metal test piece, its disturbance response to a buried crack is weak, resulting in blurred crack edge positioning and low feature signal recognition. Although a high-frequency excitation signal has high sensitivity to crack disturbance, its penetration depth is limited and can only cover the surface or near-surface region, making it impossible to effectively detect deep buried cracks. The inherent defects of this single frequency excitation make the traditional alternating current electromagnetic detection technology insufficient in the quantitative calculation of the depth of a buried crack, and it is difficult to meet the needs of risk assessment of deep defects in engineering practice.

[0004] Therefore, the traditional alternating current electromagnetic detection technology using a single frequency excitation has insufficient accuracy in the quantitative calculation of the depth of a buried crack, which is a technical problem that needs to be solved by personnel in the field. SUMMARY

[0005] The purpose of the present application is to provide a metal buried crack depth detection method, device and medium, which solves the problem of insufficient accuracy in the quantitative calculation of the depth of a buried crack by using a single frequency excitation in the traditional alternating current electromagnetic detection technology.

[0006] To solve the above technical problems, the present application provides a metal buried crack depth detection method applied to a sweep frequency alternating current electromagnetic detection probe with controllable excitation frequency, which comprises:

[0007] controlling the sweep frequency alternating current electromagnetic detection probe to scan the surface of a metal test piece with an alternating excitation signal at a preset frequency;

[0008] obtaining a magnetic field vertical component waveform graph perpendicular to the surface of the metal test piece, and determining the edge position of a buried crack according to the magnetic field vertical component waveform graph;

[0009] controlling the sweep frequency alternating current electromagnetic detection probe to apply a sweep frequency alternating excitation signal at the edge position, wherein the sweep frequency alternating excitation signal is an alternating current signal with a linearly changing frequency over time;

[0010] acquiring a magnetic field vertical component perpendicular to a surface of the metal sample to be tested under the excitation of the sweep-frequency alternating-current excitation signal, and obtaining a response curve of a magnitude of the magnetic field vertical component varying with the excitation frequency;

[0011] obtaining a characteristic frequency of a preset characteristic point according to the response curve;

[0012] determining the buried crack depth according to the characteristic frequency.

[0013] As an optional solution, in the metal buried crack depth detection method, the sweep-frequency alternating-current electromagnetic detection probe is controlled to scan the surface of the metal sample to be tested with the alternating-current excitation signal of the preset frequency, including:

[0014] determining the size of the preset frequency according to the material characteristics of the metal sample to be tested, wherein the preset frequency is less than 100 Hz;

[0015] controlling the sweep-frequency alternating-current electromagnetic detection probe to move along a first direction according to a preset step size, and scanning the surface of the metal sample to be tested with the alternating-current excitation signal of the preset frequency;

[0016] in the scanning process, the magnetic field vertical component perpendicular to the surface of the metal sample to be tested is collected every time a preset step size is moved;

[0017] after the first direction scanning, the sweep-frequency alternating-current electromagnetic detection probe is moved along a second direction perpendicular to the first direction, and the step of returning to scan the surface of the metal sample to be tested with the alternating-current excitation signal of the preset frequency is performed until the scanning covers a preset detection area of the metal sample to be tested.

[0018] As an optional solution, in the metal buried crack depth detection method, the determination of the edge position of the buried crack according to the magnetic field vertical component waveform includes:

[0019] determining effective peaks and troughs according to the magnetic field vertical component waveform, wherein when the amplitude difference between the peak and the trough is greater than a preset threshold, it is determined to be effective;

[0020] taking the peak and the trough position as the boundary point of the edge of the buried crack, and recording the spatial coordinates of the boundary point.

[0021] As an optional solution, in the metal buried crack depth detection method, the control of the sweep-frequency alternating-current electromagnetic detection probe to apply the sweep-frequency alternating-current excitation signal at the edge position includes:

[0022] determining a frequency range and a sweep time interval of the sweep-frequency alternating-current excitation signal, wherein the frequency range contains the preset frequency;

[0023] aligning a detection center of the swept-frequency AC electromagnetic detection probe with the spatial coordinates of the boundary point;

[0024] controlling the swept-frequency AC electromagnetic detection probe to switch the excitation frequency in a linearly increasing manner from the lower limit of the frequency range according to a swept-frequency time interval, and output an AC excitation signal.

[0025] As an optional solution, in the metal buried crack depth detection method, the obtaining of the vertical component of the magnetic field perpendicular to the surface of the metal test piece under the excitation of the swept-frequency AC excitation signal and the obtaining of the response curve of the amplitude of the vertical component of the magnetic field changing with the excitation frequency, comprises:

[0026] collecting the real-time response signal of the vertical component of the magnetic field perpendicular to the surface of the test piece by the TMR magnetic sensitive chip of the swept-frequency AC electromagnetic detection probe;

[0027] extracting the amplitude of the vertical component of the magnetic field for each excitation frequency point to obtain the response amplitude of the vertical component of the magnetic field of the current real-time response signal;

[0028] recording the response amplitude of the vertical component of the magnetic field corresponding to all excitation frequencies;

[0029] fitting the response curve of the response amplitude of the vertical component of the magnetic field changing with the excitation frequency according to the excitation frequencies and the corresponding response amplitudes of the vertical component of the magnetic field.

[0030] As an optional solution, in the metal buried crack depth detection method, the characteristic frequency of the preset characteristic point is obtained according to the response curve, comprising:

[0031] taking the zero point of the response curve where the response amplitude of the vertical component of the magnetic field is zero as the preset characteristic point;

[0032] determining the excitation frequency of the preset characteristic point in the response curve;

[0033] taking the excitation frequency of the preset characteristic point as the characteristic frequency.

[0034] As an optional solution, in the metal buried crack depth detection method, the buried crack depth is determined according to the characteristic frequency, comprising:

[0035] calling a preset characteristic equation, wherein the preset characteristic equation is constructed based on a simulation modeling system of a frequency domain electromagnetic field control equation, and is obtained by fitting experimental data of a plurality of standard crack test pieces with known depths;

[0036] substituting the characteristic frequency into the preset characteristic equation as an input parameter;

[0037] taking the output result of the preset characteristic equation as the buried crack depth of the current boundary point.

[0038] To solve the above problems, the application further provides a metal buried crack depth detection device, comprising:

[0039] A pre-scanning module is configured to control the swept-frequency alternating electromagnetic detection probe to scan the surface of the metal test piece with an alternating excitation signal at a preset frequency.

[0040] A positioning module is configured to obtain a magnetic field vertical component waveform perpendicular to the surface of the metal test piece and determine the edge position of the buried crack according to the magnetic field vertical component waveform.

[0041] A scanning module is configured to control the swept-frequency alternating electromagnetic detection probe to apply a swept-frequency alternating excitation signal at the edge position, wherein the swept-frequency alternating excitation signal is an alternating current signal with a linearly changing frequency over time.

[0042] A curve generation module is configured to obtain the magnetic field vertical component perpendicular to the surface of the metal test piece under the excitation of the swept-frequency alternating excitation signal and obtain a response curve of the amplitude of the magnetic field vertical component changing with the excitation frequency.

[0043] An analysis module is configured to obtain the characteristic frequency of a preset characteristic point according to the response curve.

[0044] An output module is configured to determine the buried crack depth according to the characteristic frequency.

[0045] To solve the above problems, the application further provides a metal buried crack depth detection device, comprising:

[0046] A memory is configured to store a computer program.

[0047] A processor is configured to implement the steps of the metal buried crack depth detection method when the computer program is executed.

[0048] To solve the above problems, the application further provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the metal buried crack depth detection method.

[0049] The metal buried crack depth detection method provided in the application first performs pre-scanning through a single frequency, utilizes the magnetic field distortion characteristics generated by the circumnavigation of the induction current at the crack edge, and can preliminarily position the crack edge, then applies a sweep-frequency alternating excitation signal with a frequency that linearly changes over time at the preliminarily positioned edge, so that the induction currents of different frequencies cover the full range from the surface layer to the deep layer, since there is a stable mapping relationship between the excitation frequency of the alternating excitation signal and the crack depth, the low-frequency component can penetrate to a deeper area inside the test piece, realizing the detection of the deep crack; the high-frequency component is concentrated in the surface layer, ensuring a high sensitivity response to crack disturbance. By means of the sweep-frequency signal, the induction currents of different frequencies are distributed at different depths, the correlation between the frequency and the depth is converted into a quantifiable mapping relationship between the characteristic frequency and the depth, and the controllable utilization of the skin effect is realized. The application utilizes the characteristic frequency in the sweep-frequency process to invert the buried depth of the buried crack, breaks through the resolution bottleneck of the traditional single-frequency excitation method in crack depth identification, and significantly improves the practicability and precision level of the alternating electromagnetic detection technology in deep defect identification.

[0050] In addition, the application also provides a device and a medium, which correspond to the metal buried crack depth detection method described above, and have the same effects. BRIEF DESCRIPTION OF DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0052] Figure 1 A flow chart of a metal buried crack depth detection method is provided for the embodiments of the application.

[0053] Figure 2 A schematic diagram of a sweep-frequency alternating electromagnetic detection probe is provided for the embodiments of the application.

[0054] Figure 3 A crack detection result waveform diagram under single-frequency excitation is provided for the embodiments of the application.

[0055] Figure 4 A sweep-frequency excitation detection result response curve diagram is provided for the embodiments of the application.

[0056] Figure 5 A simulation finite element model is provided for the embodiments of the application.

[0057] Figure 6 A structural diagram of a metal buried crack depth detection device is provided for the embodiments of the application.

[0058] Figure 7 Another structure diagram of a metal buried crack buried depth detection device provided by an embodiment of the present application is provided. DETAILED DESCRIPTION

[0059] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0060] The core of the present application is to provide a metal buried crack buried depth detection method, device and medium.

[0061] In order to enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0062] The present method is suitable for buried depth detection of internal buried cracks of metal components (such as steel, aluminum alloy, titanium alloy, etc.) in the fields of aerospace, mechanical manufacturing, pressure vessels, etc. It solves the problem that the penetration depth and sensitivity cannot be considered in the traditional single frequency detection, and realizes quantitative and accurate measurement of the buried depth of the buried crack.

[0063] The present application provides a metal buried crack buried depth detection method, which is applied to a sweep frequency alternating current electromagnetic detection probe with controllable excitation frequency, such as shown in the figure. Figure 1 The method comprises the following steps.

[0064] S11: controlling the sweep frequency alternating current electromagnetic detection probe to scan the surface of the metal test piece with the alternating excitation signal of the preset frequency;

[0065] S12: obtaining a magnetic field vertical component waveform diagram perpendicular to the surface of the metal test piece to be measured, and determining the edge position of the buried crack according to the magnetic field vertical component waveform diagram;

[0066] S13: controlling the sweep frequency alternating current electromagnetic detection probe to apply a sweep frequency alternating excitation signal at the edge position, wherein the sweep frequency alternating excitation signal is an alternating current signal with a linear change of frequency over time;

[0067] S14: obtaining the magnetic field vertical component perpendicular to the surface of the metal test piece to be measured under the excitation of the sweep frequency alternating excitation signal, and obtaining a response curve of the amplitude of the magnetic field vertical component changing with the excitation frequency;

[0068] S15: obtaining the characteristic frequency of the preset characteristic point according to the response curve;

[0069] S16: determining the buried depth of the buried crack according to the characteristic frequency.

[0070] The preset frequency in step S11 refers to an alternating current signal output by the sweep-frequency alternating current electromagnetic detection probe. The preset frequency can be determined according to the material properties (magnetic permeability and electrical conductivity) of the metal workpiece to be detected. The preset frequency is usually selected to be less than 100 Hz (for example, 20-50 Hz).

[0071] The embodiment provides an implementation scheme of a sweep-frequency alternating current electromagnetic detection probe, as shown in the accompanying drawings. Figure 2 The sweep-frequency alternating current electromagnetic detection probe includes a U-shaped magnetic core, an excitation coil, a tunnel magnetoresistance (TMR) circuit board, a signal generation module, and a power amplification module.

[0072] The signal generation module outputs an alternating current excitation signal with adjustable frequency and amplitude. The frequency range of the excitation signal covers the characteristic frequency band of crack response.

[0073] The power amplification module amplifies the excitation signal to ensure that the excitation coil obtains sufficient driving current to excite a stable and controllable alternating current electromagnetic field.

[0074] The excitation coil is wound around the middle part of the U-shaped magnetic core and is used to load an alternating current signal to excite an induced magnetic field on the surface of the workpiece. The U-shaped magnetic core is used to guide the excitation magnetic field to form a local concentrated magnetic flux. The core of the TMR circuit board is a TMR magnetic sensitive chip used to detect the magnetic field component perpendicular to the surface of the workpiece.

[0075] The signal generation module and the power amplification module of the sweep-frequency alternating current electromagnetic detection probe are used to output the alternating current signal. The embodiment does not limit the size of the preset frequency. For example, 20 Hz can be selected when detecting an aluminum plate, and 15 Hz can be selected when detecting high magnetic permeability steel.

[0076] The alternating current excitation signal is loaded to the excitation coil, which excites an induced current on the surface and inside of the workpiece. According to the skin effect, as shown in the following formula (1), the lower the frequency of the alternating current excitation signal, the stronger the penetration ability of the induced current, which can penetrate to a deeper area inside the workpiece. The penetration depth can be calculated by the skin depth.

[0077] (1)

[0078] wherein, represents the skin depth, represents the excitation angular frequency, represents the magnetic permeability, represents the electrical conductivity, represents the excitation frequency of the alternating current excitation signal.

[0079] The scanning needs to be realized by a mechanical moving mechanism of a swept-frequency alternating electromagnetic detection probe, moving in a first direction (such as a horizontal direction) by a preset step (0.1-1 mm), collecting data once per step, and then offsetting in a second direction (such as a vertical direction) until a preset detection area (such as a key stress position of a component) is covered.

[0080] It should be noted that the reason for selecting a low frequency as the preset frequency is based on the skin effect, and the induced current of a low-frequency signal has a large penetration depth and can penetrate to the deep layer of the test piece, so that even a crack with a large buried depth can be disturbed. This step realizes preliminary positioning of the approximate area of the crack by low-frequency scanning, and provides a range reference for subsequent accurate detection.

[0081] In step S12, a magnetic field vertical component waveform graph perpendicular to the surface of the metal test piece to be detected is obtained, and the edge position of the buried crack is determined according to the waveform graph. The magnetic field vertical component (denoted as Bz) perpendicular to the surface of the test piece is collected by a TMR magnetic sensitive chip built in the probe.

[0082] The peak-valley response is the magnetic field distortion caused by the induced current around the crack edge: Bz approaches zero in the crack-free area, and the current around the crack edge causes Bz to form a wave peak (current aggregation) and a wave valley (current sparsity) on both sides.

[0083] Figure 3 A crack detection result waveform graph under single-frequency excitation provided for an embodiment of the present application is shown in FIG. 6. Figure 3 As shown in FIG. 6, by analyzing the waveform graph, it can be determined that when the amplitude difference between the wave peak and the wave valley is greater than a preset threshold (such as 5 times the reference noise), it is determined as an effective crack, and the spatial coordinates (such as x=+15 mm) corresponding to the wave peak and the wave valley are recorded as the crack edge.

[0084] The boundary profile of the crack is accurately locked by using the distortion characteristics of Bz, the problem of ambiguous crack position in the traditional technology is solved, and an explicit spatial measurement reference is provided for subsequent swept-frequency detection. Only the edge is detected, and invalid data is reduced.

[0085] In step S13, a swept-frequency alternating excitation signal is applied to the edge position by controlling the swept-frequency alternating electromagnetic detection probe. The swept-frequency alternating excitation signal is an alternating current signal with a linearly increasing frequency from a lower limit to an upper limit, and the frequency range includes the preset frequency (such as 20-100 Hz) in step S11. The linear frequency modulation function of the signal generation module is used to realize the swept-frequency alternating excitation signal.

[0086] The detection center of the probe is aligned with the boundary coordinates recorded in step S12, the posture of the probe can be fixed by a mechanical positioning mechanism, and the stability of the detection point is ensured.

[0087] The purpose of linearly changing the sweep frequency is to utilize the frequency dependence of the skin effect, with low-frequency components (such as 20 Hz) penetrating to deep layers and high-frequency components (such as 150 Hz) concentrating on the surface layer, so that the induced current at different frequencies covers the full range from the surface layer to the deep layer. This step converts the limitation of a single frequency into the advantage of full-band, laying a foundation for subsequent extraction of depth-related features.

[0088] Step S14 obtains a response curve of the amplitude of the magnetic field vertical component varying with the excitation frequency, the amplitude of the magnetic field vertical component referring to the fundamental wave amplitude of the Bz signal at each excitation frequency, and the response curve being obtained by Fourier transform of the original signal collected by the TMR chip (noise and harmonic interference are filtered out).

[0089] Figure 4 A sweep excitation detection result response curve provided by the embodiment of the present application, the response curve being a continuous curve fitted from the excitation frequency-amplitude data pairs, for example, the response amplitude of the magnetic field vertical component is large in the low-frequency stage (deep current disturbance is strong), the amplitude decreases in the high-frequency stage (current concentrates on the surface layer), and phase inversion (amplitude zero crossing) occurs at a specific frequency.

[0090] Specifically, the frequency and amplitude can be recorded synchronously by a data acquisition module (the sampling rate is more than 20 times the highest frequency), and the fitted curve directly presents the variation rule of the Bz response with the frequency, clearly reflecting the disturbance difference of the current by cracks at different depths, and providing a visual data carrier for feature frequency extraction.

[0091] Step S15 obtains the feature frequency of a preset feature point according to the response curve, the preset feature point referring to a key position with clear physical meaning, such as the zero point of the response amplitude of the magnetic field vertical component (phase inversion point, sudden change of the current circumnavigation direction), the maximum amplitude point (the frequency of the strongest crack disturbance), and the like, and the amplitude zero point is preferentially selected (high stability).

[0092] The feature frequency is the excitation frequency corresponding to the feature point, for example, the frequency corresponding to the amplitude zero point, which is determined by linear fitting of the intersection point of the curve and the horizontal axis (error ≤0.5 Hz).

[0093] The feature frequency is stably associated with the crack depth, and the deeper the depth, the deeper the induced current needs to penetrate to be disturbed, and the lower the phase inversion frequency (for example, about 49 Hz for a depth of 5 mm, and about 69 Hz for a depth of 2 mm).

[0094] Step S16: Determine the buried crack depth according to the characteristic frequency. A fitting relationship between the characteristic frequency and the crack depth needs to be constructed in advance according to standard data, which can be in the form of an equation or a table. The present embodiment does not make specific limitations. For example, a model can be constructed in advance, and the characteristic equation is also a kind of preset mathematical model, which is constructed based on the frequency domain electromagnetic field control equation (Maxwell equation set) and obtained by fitting a plurality of standard test blocks (known depth 0.5-20mm) experimental data.

[0095] The characteristic frequency extracted in step S15 is substituted into the characteristic equation, and the corresponding depth value is calculated to realize the quantitative mapping of frequency-depth through the characteristic equation.

[0096] The metal buried crack depth detection method provided in the embodiment first performs pre-scanning through a single frequency, uses the magnetic field distortion characteristics generated by the induced current around the crack edge, and can preliminarily locate the buried crack edge. Then, a sweep frequency alternating excitation signal with a frequency that changes linearly with time is applied at the preliminarily located edge, so that the induced current at different frequencies covers the full range from the surface to the deep layer. Since there is a stable mapping relationship between the excitation frequency of the alternating excitation signal and the crack depth, the low-frequency component can penetrate to a deeper area inside the test piece, realizing the detection of deep cracks; the high-frequency component is concentrated on the surface, ensuring a high sensitivity response to crack disturbance. By using the sweep signal, the induced current at different frequencies is distributed at different depths, and the correlation between frequency and depth is converted into a quantifiable mapping relationship between characteristic frequency and depth, realizing the controllable use of the skin effect. The present application uses the characteristic frequency in the sweep process to invert the buried crack depth, breaks through the resolution bottleneck of the traditional single frequency excitation method in crack depth identification, and significantly improves the practicality and precision level of alternating electromagnetic detection technology in deep defect identification.

[0097] According to the above embodiment, specifically, the surface of the metal test piece to be measured is scanned by the sweep frequency alternating electromagnetic detection probe with an alternating excitation signal at a preset frequency, including:

[0098] The size of the preset frequency is determined according to the material characteristics of the metal test piece to be measured, wherein the preset frequency is less than 100Hz;

[0099] The sweep frequency alternating electromagnetic detection probe is controlled to move along the first direction according to a preset step size, and the surface of the metal test piece to be measured is scanned with an alternating excitation signal at a preset frequency;

[0100] During the scanning process, the magnetic field vertical component perpendicular to the surface of the metal test piece to be measured is collected once every preset step size;

[0101] After the first direction scanning, the swept-frequency alternating electromagnetic detection probe is moved along a second direction perpendicular to the first direction, and the step of returning to scan the surface of the metal test piece with the alternating excitation signal at the preset frequency is repeated until the preset detection area of the metal test piece is covered.

[0102] According to the material characteristics such as the magnetic permeability and the electrical conductivity of the metal to be tested, a low-frequency signal of <100 Hz is selected in the embodiment. The core is to use the strong penetration of the low-frequency signal (weak skin effect) to ensure that the deep buried crack can be disturbed by the induced current. The probe is moved along the first direction (for example, horizontally) by a preset step (for example, 0.5 mm), and the magnetic field vertical component (Bz) is collected once per step to realize the ordered detection of the linear region. After the first direction scanning is completed, the second direction (for example, vertically) is offset, and the scanning is repeated until the preset detection area (for example, the stress concentration area of the component) is covered, so as to ensure that there is no omission in the detection range.

[0103] The moving step is strictly corresponding to the data collection, and the data is collected once per step to ensure the accurate matching of the spatial coordinates and the Bz data. According to formula (1) and the magnetic permeability and the electrical conductivity of the material, the critical penetration frequency is calculated to make the penetration depth of the induced current greater than the estimated maximum buried depth. For example, if the preset detection buried depth is 5 mm, the frequency needs to satisfy ≥5 mm.

[0104] Preferably, a larger step (for example, 1 mm) is used in the initial scanning stage to quickly cover the area. When a slight fluctuation (for example, the amplitude exceeds 30% of the noise threshold) of the Bz signal is detected, it is determined as a "suspected crack area", and the scanning is automatically switched to a small step (for example, 0.1 mm) for fine scanning.

[0105] Preferably, after moving one step, the Bz signal of multiple cycles (for example, 5-10 cycles) is continuously collected at the same position, and the stable peak-valley characteristics are retained by mean filtering or wavelet denoising to eliminate transient interference. For example, N=5 cycles of Bz signal is collected per step (N is adjusted according to the preset frequency, for example, the period of 20 Hz signal is 0.05 s, and 5 cycles only need 0.25 s, which does not significantly affect the efficiency); the mean value of the response amplitude of the magnetic field vertical component of N cycles is calculated, the abnormal value deviating from the mean value by ±3 times of the standard deviation is removed, and the filtered value is taken as the effective data of the step.

[0106] According to the above embodiment, specifically, the edge position of the buried crack is determined according to the magnetic field vertical component waveform diagram, which comprises:

[0107] According to the magnetic field vertical component waveform diagram, the effective peak and the valley are determined, wherein when the amplitude difference between the peak and the valley is greater than a preset threshold, it is determined that the peak and the valley are effective;

[0108] The peak and the valley positions are taken as the boundary points of the edges of the buried crack, and the spatial coordinates of the boundary points are recorded.

[0109] Based on the theory of electromagnetic induction, the buried crack will cause the induced current to bypass at the edge, causing the local distortion of the magnetic field perpendicular to the surface of the specimen (Bz), and the magnetic field enhancement zone (peak) and weakening zone (valley) are formed on both sides of the crack. The effective signal is screened by the amplitude difference of the peak and the valley > the preset threshold value, and the noise interference (such as the slight fluctuation caused by the non-uniformity of the material, environmental electromagnetic interference, etc.) is excluded. The threshold value is usually set according to the noise level of the detection environment, for example, 3-5 times the amplitude of the background noise is selected.

[0110] The spatial position of the effective peak and valley is directly corresponding to the boundary point of the crack edge (for example, the peak corresponds to one side of the crack edge, and the valley corresponds to the other side), and the coordinates (such as x = 15 mm, y = 30 mm) are recorded by the displacement sensor of the probe, which provides an accurate spatial reference for subsequent sweep frequency detection, and ensures that the sweep frequency signal can be focused on the crack edge which is the most sensitive area to magnetic field disturbance.

[0111] It should be noted that the preset threshold value is mostly set by experience, if the threshold value is too high, the shallow or small crack (with small peak-valley amplitude difference) may be missed; if the threshold value is too low, the noise may be misjudged as a crack signal, resulting in incorrect edge judgment. Preferably, the threshold value is calculated based on the background noise in real time, rather than selecting a fixed threshold value.

[0112] Specifically, before scanning, the Bz signal is collected in the area without cracks, and the amplitude standard deviation is calculated to reflect the background noise level.

[0113] The dynamic threshold value is set to 3 times the amplitude standard deviation; if there is strong electromagnetic interference in the detection area, the threshold value is modified to 5 times the amplitude standard deviation to avoid misjudgment of interference signals.

[0114] In addition, the peak and valley of the real crack have "symmetry" (the width and slope of the peak and valley are similar), while the interference peak and valley are mostly asymmetric; specifically, the slope ratio of the peak and valley is calculated to screen the peak and valley with obvious symmetry characteristics.

[0115] Preferably, the suspected peak and valley position is scanned for 3 times, if the peak and valley coordinate deviation of 3 times scanning is ≤0.3 mm, it is judged as a stable signal (the peak and valley position of the real crack is fixed), otherwise it is considered as interference.

[0116] According to the above embodiment, specifically, the sweep frequency alternating current electromagnetic detection probe is controlled to apply a sweep frequency alternating current excitation signal at the edge position, comprising:

[0117] The frequency range and sweep time interval of the sweep frequency alternating current excitation signal are determined, wherein the frequency range contains a preset frequency;

[0118] The spatial coordinates of the detection center of the sweep frequency alternating current electromagnetic detection probe and the boundary point are aligned;

[0119] The control swept-frequency alternating electromagnetic detection probe switches the excitation frequency in a linearly increasing manner from the lower limit of the frequency range according to the swept-frequency time interval, and outputs an alternating excitation signal.

[0120] It should be noted that the frequency range needs to contain a preset frequency (such as 20 Hz) and expand to a high frequency (such as 15-150 Hz), the purpose is to utilize the frequency dependence of the skin effect, the low frequency signal penetrates to the deep layer, and the high frequency signal concentrates on the surface layer, so that the induced current of different frequencies covers the full range from the crack depth to the surface layer.

[0121] The swept-frequency time interval refers to the time difference between adjacent frequency points, which determines the rate of frequency switching and ensures that the magnetic field response is stable before data acquisition at each frequency point.

[0122] The detection center (sensitive area of TMR chip) of the probe is aligned with the boundary point coordinates through a mechanical positioning mechanism (such as a precision guide rail or laser positioning), and precise alignment ensures that the swept-frequency signal acquisition obtains the most sensitive response signal, reducing signal attenuation caused by edge deviation.

[0123] Starting from the lower limit of the frequency range, the frequency is linearly increased by time interval (such as 1 Hz per second), and the upper limit (such as 150 Hz) is reached, and a continuous alternating excitation signal is output through the linear frequency modulation function of the signal generation module. This method can ensure uniform frequency coverage and avoid response curve distortion caused by frequency jumping, facilitating subsequent extraction of continuous characteristic frequencies.

[0124] However, it is difficult for a fixed frequency range to adapt to cracks of different depths: shallow cracks (such as 1 mm) may not require high frequencies (high frequency data is redundant), and deep cracks (such as 10 mm) may require lower starting frequencies (existing low frequency range is insufficient), resulting in low data efficiency or insufficient response. Preferably, the crack depth is estimated according to the peak-to-valley amplitude difference of the pre-scan (the larger the amplitude difference, the shallower the buried depth), and the frequency range is dynamically adjusted.

[0125] Specifically, after pre-scanning, the amplitude difference of the effective peak-to-valley is calculated, and a larger amplitude difference corresponds to a shallow crack, and the frequency range is set to 50-200 Hz (high frequency range is dominant); a smaller amplitude difference corresponds to a deep crack, and the frequency range is set to 10-100 Hz (low frequency range is dominant); ensure that the adjusted range still contains the preset frequency, and ensure the continuity with the pre-scan.

[0126] For irregular cracks (different depths at different positions), set the frequency range at multiple edge points (such as 50-200 Hz for shallow cracks on one side and 10-100 Hz for deep cracks on the other side).

[0127] According to the above embodiments, specifically, obtaining the vertical component of the magnetic field perpendicular to the surface of the metal specimen under test under frequency sweep AC excitation signal excitation, and obtaining the response curve of the amplitude of the vertical component of the magnetic field changing with the excitation frequency, includes:

[0128] The TMR magnetic sensor chip of the frequency sweeping AC electromagnetic detection probe acquires the real-time response signal of the vertical component of the magnetic field perpendicular to the surface of the specimen.

[0129] The amplitude of the vertical component of the magnetic field at each excitation frequency point is extracted to obtain the amplitude of the vertical component response of the current real-time response signal.

[0130] Record the amplitude of the vertical component response of the magnetic field corresponding to all excitation frequencies;

[0131] The response curve of the vertical component response amplitude of the magnetic field as a function of the excitation frequency is obtained by fitting the response amplitude of each excitation frequency and the corresponding vertical component response amplitude of the magnetic field.

[0132] The TMR magnetic sensor is a highly sensitive magnetic sensor whose resistance changes significantly with the strength of an external magnetic field, allowing it to accurately capture minute fluctuations in the vertical component of the magnetic field perpendicular to the sample surface. The TMR sensor works synchronously with a swept frequency signal for sampling, converting analog signals into digital signals.

[0133] The Bz signal at each excitation frequency point contains a fundamental wave (consistent with the excitation frequency) and noise. The fundamental wave amplitude needs to be extracted through signal processing to reflect the core parameter of the crack's influence on the magnetic field at that frequency.

[0134] In addition, when collecting data at a single frequency point, Fourier transform (FFT) can be performed to extract the amplitude of the frequency component that is the same as the excitation frequency (e.g., when the excitation frequency is 50Hz, extract the amplitude of the 50Hz component) and filter out noise interference from other frequencies.

[0135] The excitation frequency is correlated with the corresponding vertical component response amplitude of the magnetic field to form data pairs, which are stored in the database to ensure a one-to-one correspondence during subsequent curve fitting.

[0136] By using least squares or polynomial fitting, discrete data pairs are transformed into continuous curves, visually presenting the trend of the amplitude of the vertical component response of the magnetic field with frequency (e.g., high amplitude in the low-frequency range, low amplitude in the high-frequency range, with the amplitude crossing zero at a certain intermediate frequency point). Figure 4 As shown, continuous curves can clearly identify feature points (such as zero amplitude points), avoiding misjudgment of feature frequencies caused by discrete data.

[0137] Preferably, 2-3 TMR magnetic sensing chips are integrated into the probe to synchronously acquire the same magnetic field and remove outliers by mean filtering.

[0138] According to the above embodiment, specifically, the characteristic frequency of the preset feature point is obtained according to the response curve, comprising:

[0139] The zero point of the response amplitude of the vertical component of the magnetic field in the response curve is taken as the preset feature point;

[0140] The excitation frequency of the preset feature point in the response curve is determined;

[0141] The excitation frequency of the preset feature point is taken as the characteristic frequency.

[0142] The zero point of the response amplitude of the vertical component of the magnetic field is the intersection point of the transition of the vertical component of the magnetic field from positive (or negative) to negative (or positive) in the response curve, corresponding to the sudden change of the circumferential direction of the induced current, when the excitation frequency reaches a certain value, the disturbance of the crack to the deep and surface induced current cancels out, resulting in zero vertical magnetic field component. The frequency of this point has a stable mathematical correlation with the crack depth (the greater the depth, the lower the zero frequency).

[0143] Compared with the maximum amplitude point and other feature points, the zero point is less affected by noise (the signal change rate is high when the amplitude is close to zero, and the recognition is more stable), and has a stronger linear correlation with the depth.

[0144] In the fitted continuous response curve, the frequency value when the response amplitude of the vertical component of the magnetic field is 0 is found. The excitation frequency corresponding to the zero point is directly taken as the characteristic frequency, without additional conversion, simplifying the calculation process.

[0145] According to the above embodiment, specifically, the crack depth is determined according to the characteristic frequency, comprising:

[0146] The preset characteristic equation is called, wherein the preset characteristic equation is constructed based on a simulation modeling system of a frequency domain electromagnetic field control equation, and is obtained by fitting experimental data of a plurality of standard crack specimens with known depths;

[0147] The characteristic frequency is taken as an input parameter and substituted into the preset characteristic equation;

[0148] The output result of the preset characteristic equation is taken as the crack depth of the current boundary point.

[0149] The characteristic equation is constructed based on a frequency domain electromagnetic field control equation (a frequency domain form of Maxwell's equation set), and the electromagnetic response of cracks with different depths under sweep excitation is simulated by a finite element simulation system to establish a theoretical mapping relationship between the depth and the characteristic frequency.

[0150] Figure 5 A simulation finite element model provided by the embodiment of the application is shown in Figure 5 The frequency domain Maxwell equation set is used as the control equation:

[0151] ;

[0152] wherein, denotes the electric field strength, denotes the curl operator, denotes the angular frequency, denotes the magnetic permeability, is the magnetic field strength, denotes the electric conductivity, denotes the dielectric constant, denotes the imaginary unit;

[0153] The mathematical model is constructed as follows:

[0154] Skin depth Definition: ;

[0155] Induced current distribution changes with depth: ;

[0156] wherein, denotes the current intensity at depth under the alternating excitation signal, denotes the current intensity on the surface of the metal sample, denotes the natural constant.

[0157] The corresponding magnetic field vertical component under the disturbance of the buried crack at depth h is:

[0158] ;

[0159] wherein, denotes the magnetic field vertical component in the z-axis direction of the magnetic field under the excitation of the alternating excitation signal, denotes the line element vector.

[0160] Further combined with multiple sets of simulation data and experimental measurements, the following crack depth inversion formula is constructed: based on experimental data fitting, the empirical fitting equation between crack depth and characteristic frequency can be obtained as: wherein, denotes the characteristic frequency, denotes the crack depth.

[0161] For example, the value of the characteristic frequency of 49.09 Hz is substituted into the equation to obtain the crack depth of about 5.04 mm. It should be noted that the fitting equation mentioned in the embodiment is a realizable scheme, but not the only selectable scheme. Different characteristic points can be selected for modeling and fitting according to actual needs to obtain a suitable fitting equation.

[0162] The output result is the crack depth corresponding to the current detection boundary point, reflecting the vertical distance between the crack and the surface of the sample at this position.

[0163] In the above embodiment, the metal buried crack depth detection method is described in detail, and the application also provides a corresponding embodiment of a metal buried crack depth detection device. It should be noted that the embodiments of the device part are described from two angles, one is based on the functional module angle, and the other is based on the hardware angle.

[0164] Based on the functional module angle, Figure 6 The structural diagram of a metal buried crack depth detection device provided by an embodiment of the application is shown in FIG. 1. The metal buried crack depth detection device comprises: Figure 6 As shown in FIG. 1, a metal buried crack depth detection device comprises:

[0165] A pre-scanning module 21 is configured to control a swept-frequency alternating-current electromagnetic detection probe to scan the surface of a metal test piece with an alternating-current excitation signal at a preset frequency.

[0166] A positioning module 22 is configured to obtain a magnetic field vertical component waveform perpendicular to the surface of the metal test piece, and determine the edge position of the buried crack according to the magnetic field vertical component waveform.

[0167] A scanning module 23 is configured to control the swept-frequency alternating-current electromagnetic detection probe to apply a swept-frequency alternating-current excitation signal at the edge position, wherein the swept-frequency alternating-current excitation signal is an alternating-current signal with a frequency that changes linearly with time.

[0168] A curve generation module 24 is configured to obtain the magnetic field vertical component perpendicular to the surface of the metal test piece under the excitation of the swept-frequency alternating-current excitation signal, and obtain a response curve of the amplitude of the magnetic field vertical component changing with the excitation frequency.

[0169] An analysis module 25 is configured to obtain the characteristic frequency of a preset characteristic point according to the response curve.

[0170] An output module 26 is configured to determine the buried crack depth according to the characteristic frequency.

[0171] Since the embodiments of the device part correspond to the embodiments of the method part, the embodiments of the device part are described in the description of the embodiments of the method part, which will not be described here.

[0172] Figure 7 The structural diagram of another metal buried crack depth detection device provided by an embodiment of the application is shown in FIG. 2. The metal buried crack depth detection device comprises: Figure 7 As shown in FIG. 2, the metal buried crack depth detection device comprises a memory 30 configured to store a computer program.

[0173] A processor 31 is configured to implement the steps of the method for obtaining user operation habit information according to the above-described embodiment (metal buried crack depth detection method) when executing the computer program.

[0174] The metal buried crack depth detection device provided by the embodiment can include, but is not limited to, a mobile terminal, a personal computer, a workstation, and the like.

[0175] The processor 31 can include one or more processing cores, such as a 4-core processor, an 8-core processor, and the like. The processor 31 can be implemented in at least one of a hardware form of a Digital Signal Processor (DSP), a Field-Programmable Gate Array (FPGA), a Programmable Logic Array (PLA). The processor 31 can also include a main processor and a coprocessor. The main processor is a processor for processing data in an awake state, also known as a Central Processing Unit (CPU). The coprocessor is a low-power processor for processing data in a standby state. In some embodiments, the processor 31 can be integrated with a Graphics Processing Unit (GPU). The GPU is responsible for rendering and drawing the content required to be displayed on the display screen. In some embodiments, the processor 31 can also include an Artificial Intelligence (AI) processor for processing machine learning-related computing operations.

[0176] The memory 30 can include one or more computer-readable storage media, which can be non-transitory. The memory 30 can also include a high-speed random access memory, and a non-volatile memory such as one or more disk storage devices, flash storage devices. In the embodiment, the memory 30 is at least used to store the following computer program 301, wherein the computer program is loaded and executed by the processor 31, and can implement the related steps of the metal buried crack depth detection method disclosed in any of the preceding embodiments. In addition, the resources stored by the memory 30 can also include an operating system 302 and data 303, and the storage mode can be temporary storage or permanent storage. The operating system 302 can include Windows, Unix, Linux, and the like. The data 303 can include, but is not limited to, data related to the metal buried crack depth detection method, and the like.

[0177] In some embodiments, the metal buried crack depth detection device can also include a display screen 32, an input / output interface 33, a communication interface 34, a power supply 35, and a communication bus 36.

[0178] Those skilled in the art can understand that, Figure 7The structure shown in the figure does not constitute a limitation on the metal buried crack depth detection device, and can include more or fewer components than shown.

[0179] The metal buried crack depth detection device provided by the embodiment of the present application comprises a memory and a processor. When the processor executes a program stored in the memory, the following method can be realized: a metal buried crack depth detection method.

[0180] Finally, the present application also provides an embodiment corresponding to a computer readable storage medium. The computer readable storage medium stores a computer program. When the computer program is executed by a processor, the steps described in the above metal buried crack depth detection method embodiment are realized.

[0181] It can be understood that if the method in the above embodiment is realized in the form of a software function unit and sold or used as an independent product, it can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application essentially or say the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and executes all or part of the steps of the method described in each embodiment of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various media that can store program codes.

[0182] The computer readable storage medium provided by the embodiment of the present application stores a computer program. When the processor executes the program, the following method can be realized: a metal buried crack depth detection method.

[0183] The metal buried crack depth detection method, device and medium provided by the present application are described in detail above. The embodiments in the specification are described in a progressive manner, and each embodiment mainly describes the differences from other embodiments. The same or similar parts of each embodiment can be referred to. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part. It should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, some improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

[0184] It also needs to be explained that in the present specification, the relational terms such as first and second and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

Claims

1. A method for buried crack depth detection of a metal, characterized by, The method is applied to a sweep frequency AC electromagnetic detection probe with controllable excitation frequency, and the method comprises the following steps: controlling the sweep frequency AC electromagnetic detection probe to scan the surface of a metal test piece with an AC excitation signal of a preset frequency; obtaining a waveform diagram of a magnetic field vertical component perpendicular to the surface of the metal test piece, and determining the edge position of a buried crack according to the waveform diagram of the magnetic field vertical component; controlling the sweep frequency AC electromagnetic detection probe to apply a sweep frequency AC excitation signal at the edge position, wherein the sweep frequency AC excitation signal is an AC signal with a linearly changing frequency over time; obtaining the magnetic field vertical component perpendicular to the surface of the metal test piece under the excitation of the sweep frequency AC excitation signal, and obtaining a response curve of the amplitude of the magnetic field vertical component changing with the excitation frequency; obtaining a characteristic frequency of a preset characteristic point according to the response curve; determining the buried depth of the buried crack according to the characteristic frequency.

2. The method of claim 1, wherein, controlling the sweep frequency AC electromagnetic detection probe to scan the surface of a metal test piece with an AC excitation signal of a preset frequency, comprising: determining the size of the preset frequency according to the material characteristics of the metal test piece, wherein the preset frequency is less than 100 Hz; controlling the sweep frequency AC electromagnetic detection probe to move along a first direction at a preset step length, and scan the surface of the metal test piece with an AC excitation signal of a preset frequency; in the scanning process, collecting the magnetic field vertical component perpendicular to the surface of the metal test piece once every preset step length; after scanning in the first direction, moving the sweep frequency AC electromagnetic detection probe along a second direction perpendicular to the first direction, and returning to the step of scanning the surface of the metal test piece with an AC excitation signal of a preset frequency until the preset detection area of the metal test piece is covered.

3. The method for detecting the burial depth of embedded cracks in metal according to claim 1, characterized in that, the method for determining the edge position of the buried crack according to the waveform diagram of the magnetic field vertical component, comprising: determining the effective wave peaks and wave troughs according to the waveform diagram of the magnetic field vertical component, wherein when the amplitude difference between the wave peaks and wave troughs is greater than a preset threshold, the wave peaks and wave troughs are determined as effective; taking the positions of the wave peaks and wave troughs as the boundary points of the edges of the buried crack, and recording the spatial coordinates of the boundary points.

4. The method for detecting the burial depth of embedded cracks in metal according to claim 3, characterized in that, the method for controlling the sweep frequency AC electromagnetic detection probe to apply a sweep frequency AC excitation signal at the edge position, comprising: determining the frequency range and sweep time interval of the sweep frequency AC excitation signal, wherein the frequency range contains the preset frequency; controlling the detection center of the sweep frequency AC electromagnetic detection probe to align with the spatial coordinates of the boundary points; controlling the sweep frequency AC electromagnetic detection probe to switch the excitation frequency in a linearly increasing manner from the lower limit of the frequency range according to the sweep time interval, and output the AC excitation signal.

5. The method for detecting the burial depth of embedded cracks in metal according to claim 4, characterized in that, the method for obtaining the magnetic field vertical component perpendicular to the surface of the metal test piece under the excitation of the sweep frequency AC excitation signal, and obtaining the response curve of the amplitude of the magnetic field vertical component changing with the excitation frequency, comprising: collecting the real-time response signal of the magnetic field vertical component perpendicular to the surface of the test piece through the TMR magnetic sensitive chip of the sweep frequency AC electromagnetic detection probe; extracting the amplitude of the magnetic field vertical component at each excitation frequency point to obtain the response amplitude of the magnetic field vertical component of the current real-time response signal; record the magnetic field vertical component response amplitude corresponding to each excitation frequency; fit the magnetic field vertical component response amplitude with respect to the excitation frequency to obtain a response curve of the magnetic field vertical component response amplitude with respect to the excitation frequency.

6. The method of claim 1, wherein, obtain a characteristic frequency of a preset characteristic point according to the response curve, including: taking a zero point of the response curve, at which the magnetic field vertical component response amplitude is zero, as the preset characteristic point; determining the excitation frequency of the preset characteristic point in the response curve; taking the excitation frequency of the preset characteristic point as the characteristic frequency.

7. The method for detecting the burial depth of embedded cracks in metal according to claim 6, characterized in that, determine the buried crack depth according to the characteristic frequency, including: calling a preset characteristic equation, wherein the preset characteristic equation is constructed based on a simulation modeling system of a frequency domain electromagnetic field control equation and is obtained by fitting experimental data of a plurality of standard crack specimens with known depths; substituting the characteristic frequency as an input parameter into the preset characteristic equation; taking an output result of the preset characteristic equation as the buried crack depth of the current boundary point.

8. A metal buried crack buried depth detection device, characterized in that, applied to a sweep frequency alternating current electromagnetic detection probe with controllable excitation frequency, including: a pre-scanning module configured to control the sweep frequency alternating current electromagnetic detection probe to scan the surface of a metal specimen to be measured with an alternating excitation signal at a preset frequency; a positioning module configured to obtain a magnetic field vertical component waveform perpendicular to the surface of the metal specimen to be measured and determine the edge position of a buried crack according to the magnetic field vertical component waveform; a scanning module configured to control the sweep frequency alternating current electromagnetic detection probe to apply a sweep frequency alternating excitation signal at the edge position, wherein the sweep frequency alternating excitation signal is an alternating current signal with a frequency varying linearly with time; a curve generation module configured to obtain a magnetic field vertical component perpendicular to the surface of the metal specimen to be measured under the excitation of the sweep frequency alternating excitation signal and obtain a response curve of the amplitude of the magnetic field vertical component with respect to the excitation frequency; an analysis module configured to obtain a characteristic frequency of a preset characteristic point according to the response curve; an output module configured to determine the buried crack depth according to the characteristic frequency.

9. A metal buried crack buried depth detection device characterized by, including: a memory configured to store a computer program; a processor configured to execute the computer program to implement the steps of the metal buried crack depth detection method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and the computer program is executed by the processor to implement the steps of the metal buried crack depth detection method according to any one of claims 1 to 7.

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