A method and device for detecting magnetic flux leakage defects

Abstract

The present invention provides a method and a device for detecting magnetic flux leakage defects. The device includes a fixing mechanism, a moving mechanism, a magnetic field excitation device, a magnetic field detection device, and a data processing unit. The method includes: generating magnetic flux in a local area of the object to be detected; moving axially to collect magnetic field signals of the first measurement line; making a circular motion around the object to be detected to reach the next measurement line position; repeating the collection until the entire circular scan is completed; analyzing the magnetic field signals to determine the suspected defect position. By generating magnetic flux in the local area, the power consumption is reduced, which is convenient for long-term operation at high positions such as bridge cables and poles; the multi-sensor differential detection and peak recognition algorithm are adopted to improve the reliability of defect detection; combined with a portable wind power generation device as a continuous power supplement, the device is more portable and easy to operate, and at the same time, the detection efficiency and accuracy are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of non-destructive testing, and particularly to a method and device for detecting defects by magnetic flux leakage. Background Art

[0002] In bridge engineering, cable-stays are key components for bearing the weight of bridges, and their safety directly affects the overall structural safety of bridges. Bridge cable-stays are generally composed of multiple strands of steel wires, with a layer of protective material wrapped around the outside. The steel wires are wound by multiple strands of wires. During long-term use, due to uneven force distribution, material fatigue, and environmental factors, internal wires may break or be damaged. Such internal defects are usually difficult to directly observe from the appearance and require the use of specialized detection techniques for identification.

[0003] Currently, magnetic flux detection technology is mainly used for detecting broken wires in steel wires. This technology determines whether there are broken wires by measuring the change in magnetic flux at the cross-section of the steel wires. However, the traditional magnetic flux detection technology has obvious deficiencies. First, the traditional method requires the overall magnetization of the cable-stay, so electromagnetic equipment with a large power is needed, which results in a large volume and heavy weight of the equipment and is difficult to operate in the high-altitude working environment of bridges. Second, since bridge cable-stays are usually located at high altitudes, the on-site power supply conditions are limited, and the continuous operation of high-power equipment is difficult to guarantee, resulting in low detection efficiency or interruption. In addition, the sensitivity of the traditional detection method is limited, and it has insufficient detection ability for small fractures or early damage inside the cable-stay, easily causing missed detections.

[0004] In the high-altitude working environment, the power supply problem of the detection equipment is particularly prominent. The cable-stay detection work usually requires the equipment to stay on the bridge for a long time, and the battery capacity is limited. Setting up temporary power supply lines not only increases the operation difficulty but also introduces potential safety hazards. At the same time, the existing detection methods have low positioning accuracy for the defect location, and often need to be repeatedly detected multiple times to determine the accurate location, which not only increases the detection time but also increases the work intensity.

[0005] In the prior art, there is a lack of a lightweight detection method and device that can not only meet the requirements of the high-altitude working environment of bridge cable-stays but also provide reliable detection results. The difficulty in cable-stay defect detection lies in how to achieve accurate and efficient detection under limited power conditions, while the equipment is easy to operate and can work for a long time. Summary of the Invention

[0006] The purpose of the present invention is to provide a method and device for detecting defects by magnetic flux leakage to solve the problem of how to improve the detection reliability and efficiency.

[0007] To achieve the above technical purpose, the present invention provides a method for detecting defects by magnetic flux leakage, including:

[0008] Generating magnetic flux in a local area of the object to be detected;

[0009] Move axially along the object to be detected and collect the magnetic field signals on the first measurement line;

[0010] Make a circular motion around the object to be detected to reach the position of the next measurement line;

[0011] Repeat the collection step until the entire circumference of the object to be detected is scanned; and

[0012] Analyze the collected magnetic field signals to determine the positions of suspected defects in the object to be detected.

[0013] Optionally, the analysis of the collected magnetic field signals includes:

[0014] Normalize the collected magnetic field signals;

[0015] Calculate the local gradient of the magnetic field signals;

[0016] Calculate the overall fluctuation intensity of the magnetic field signals; and

[0017] Identify the peaks in the magnetic field signals as the positions of suspected defects.

[0018] Optionally, the local gradient is calculated by taking the first-order difference to calculate the gradient at each point:

[0019] ;

[0020] ;

[0021] where, in the formula, G

[0023] , , B ,

[0022] , , , ,

[0021] , , ,

[0020] , A , , , , ,

[0024] (i, j) and G B (i, j) represent the gradient values at the position (i, j) in matrix A and matrix B respectively; and represent the partial derivatives of matrix A in the x and y directions respectively; and represent the partial derivatives of matrix B in the x and y directions respectively; A(i, j + 1) - A(i, j) represents the first-order difference of A in the x direction; A(i + 1, j) - A(i, j) represents the first-order difference of A in the y direction; B(i, j + 1) - B(i, j) represents the first-order difference of B in the x direction; B(i + 1, j) - B(i, j) represents the first-order difference of B in the y direction.

[0022] Optionally, the overall fluctuation intensity is calculated by the root mean square value:

[0023] ;

[0024] where, in the formula, RMSA and RMS B respectively represent the root mean square values of matrix A and matrix B, measuring the overall fluctuation intensity; M and N respectively represent the number of rows and columns of the matrix; GA(i, j) and GB(i, j) respectively represent the gradient values at position (i, j); 1 / (M×N) represents the average factor, which is the reciprocal of the total number of points in the matrix.

[0025] Optionally, identifying the peaks in the magnetic field signal includes:

[0026] Performing smoothing filtering on the magnetic field signal;

[0027] Setting the peak threshold; and

[0028] Calculating the distribution range of the peaks.

[0029] Optionally, it further includes:

[0030] Determining the measuring line and axial position where it is located according to the position of the suspected defect; and

[0031] Performing a secondary inspection on the wrapped surface of the part with the maximum peak value.

[0032] The present invention also provides a device for detecting magnetic flux leakage defects, including:

[0033] A fixing mechanism for fixing the device on the object to be detected;

[0034] A moving mechanism connected to the fixing mechanism, the moving mechanism can move axially along the object to be detected and can make a circular motion around the object to be detected;

[0035] A magnetic field excitation device arranged at the end of the moving mechanism for generating magnetic flux in a local area of the object to be detected;

[0036] A magnetic field detection device arranged near the magnetic field excitation device for detecting magnetic field signals; and

[0037] A data processing unit for processing the data collected by the magnetic field detection device.

[0038] Optionally, the object to be detected is a bridge cable rod, the fixing mechanism is a cable rod fixing ring, the moving mechanism is a telescopic rod, the magnetic field excitation device is a magnetic flux leakage excitation coil, the magnetic field detection device is a magnetic field differential detector, and the magnetic field differential detector includes at least two magnetic field electro - effect detection sensors arranged at intervals.

[0039] Optionally, it further includes a portable wind power generation device for providing power for the device.

[0040] Optionally, the moving mechanism includes a driving device for controlling the axial movement and circumferential motion of the moving mechanism; the data processing unit includes a data acquisition module and a data analysis module. The data acquisition module is used to record the magnetic field signals on each measurement line, and the data analysis module is used to calculate the magnetic field gradient and identify the magnetic field peaks.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] The method for detecting magnetic flux leakage defects provided by the present invention generates magnetic flux in a local area of the object to be detected instead of magnetizing the entire cross-section, significantly reducing the power demand; at the same time, through systematic scanning in the axial and circumferential directions and combining multi-dimensional signal analysis methods, it can accurately locate the suspected defect positions, improving the detection reliability and efficiency.

[0043] The device for detecting magnetic flux leakage defects provided by the present invention has the characteristics of compact structure and convenient operation. In particular, by using a portable wind power generation device to provide continuous power supply for the detection device, it solves the power supply difficulty problem in scenarios such as high-altitude bridge cables and poles; the magnetic field differential detector and data processing technology adopted by the device can effectively identify weak magnetic field changes, improving the sensitivity and accuracy of defect detection, and providing a reliable guarantee for the safety monitoring of important facilities such as bridges. Description of the Drawings

[0044] Figure 1 It is a block diagram of the method steps for detecting magnetic flux leakage defects in the embodiment of the present invention;

[0045] Figure 2 It is a schematic structural diagram of the device for detecting magnetic flux leakage defects in the embodiment of the present invention;

[0046] Figure 3 It is a layout diagram of the measurement lines in the method for detecting magnetic flux leakage defects in the embodiment of the present invention.

[0047] In the figure, 1, fixing mechanism; 2, moving mechanism; 3, magnetic field detection device; 4, magnetic field excitation device. Detailed Embodiments

[0048] The following will describe in more detail a method and a device for detecting magnetic flux leakage defects of the present invention with reference to the accompanying drawings, in which the preferred embodiments of the present invention are shown. It should be understood that those skilled in the art can modify the present invention described herein while still achieving the beneficial effects of the present invention. Therefore, the following description should be understood as a broad guidance to those skilled in the art and not as a limitation to the present invention.

[0049] The present invention will be described more specifically by way of example with reference to the accompanying drawings in the following paragraphs. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are in very simplified forms and use non-precise scales, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0050] Embodiment 1

[0051] An embodiment of the present invention provides a method for detecting magnetic flux leakage defects. Please refer to Figure 1 , including:

[0052] S1. Generate magnetic flux in a local area of the object to be detected;

[0053] S2. Move along the axial direction of the object to be detected and collect the magnetic field signals on the first measurement line; [[ID=J16]]

[0054] S3. Make a circular motion around the object to be detected to reach the position of the next measurement line;

[0055] S4. Repeat the collection step until the entire circumference of the object to be detected is scanned; and

[0056] S5. Analyze the collected magnetic field signals to determine the positions of suspected defects in the object to be detected.

[0057] Specifically, in step S1, a local magnetic flux is generated on the surface of the object to be detected through the magnetic field excitation device 4. Compared with the traditional full-section magnetization, this method only needs to generate magnetic flux in a local area, greatly reducing the power consumption.

[0058] In a specific example, the object to be detected may be a bridge cable rod, which is composed of multiple strands of steel strands and is wrapped with a layer of protective material on the outside. The steel strands are wound by multiple steel wires. In the case of uneven stress, there may be defects such as partial steel wire breakage or damage. The magnetic field excitation device 4 may be a magnetic flux leakage excitation coil.

[0059] In step S2, move along the axial direction of the object to be detected and collect the magnetic field signals on the first measurement line. The magnetic field signals are collected through the magnetic field detection device 3.

[0060] In a specific example, the magnetic field detection device 3 is a magnetic field differential detector, which includes at least two magnetic field electro-effect detection sensors arranged at intervals.

[0061] In a specific example, the magnetic field differential detector includes two sensors, denoted as sensor a and sensor b respectively.

[0062] On the first measurement line of the object to be detected, data points are collected at a preset interval Δl, denoted as V a1 (l) and V b1(l), where the length of the measuring line is L.

[0063] In step S3, make a circular motion around the object to be detected to reach the next measuring line position. After completing the scanning of the first measuring line, the moving mechanism 2 makes a circular motion around the object to be detected, with a moving arc length of Δr, and reaches the next measuring line position.

[0064] In this embodiment, the moving mechanism 2 can be a telescopic rod, which is connected to the fixing mechanism 1 and can make a circular motion along the fixing mechanism 1. The fixing mechanism 1 can be a cable-rod fixing ring for fixing the device on the object to be detected.

[0065] In step S4, repeat the acquisition step until the entire circumference of the object to be detected is scanned. On each measuring line i, data is acquired in the same manner as the first measuring line, denoted as V ai (l) and V bi (l). A total of n measuring lines are acquired until the entire circumference is scanned.

[0066] In step S5, analyze the acquired magnetic field signals to determine the positions of suspected defects in the object to be detected. The analysis includes:

[0067] S5.1, perform normalization processing on the acquired magnetic field signals.

[0068] Since the data may have different magnitudes, normalization processing is required:

[0069] ;

[0070] where A'(i,j) and B'(i,j) are normalized to the range [0,1]. The A and B matrices are composed of measuring line data, and A'(i,j) and B'(i,j) respectively represent the values of the normalized matrices A and B at the position (i, j); min(A) and max(A) respectively represent the minimum and maximum values in matrix A; min(B) and max(B) respectively represent the minimum and maximum values in matrix B; the normalization processing maps all data to the range [0, 1], facilitating subsequent analysis and comparison.

[0071] Specifically:

[0072] ;

[0073] where {n / 2} is the integer part of n / 2. The reason for continuing to splice 1, 2,..., {n / 2} after the matrix n serial number ends is that the object to be detected is circular, to avoid recognition deviation caused by defects appearing near the measuring line.

[0074] S5.2, calculate the local gradient of the magnetic field signal. Use the first-order difference to calculate the gradient of each point:

[0075] ;

[0076] Wherein:

[0077] ;

[0078] Wherein, in the formula, G A (i, j) and G B (i, j) respectively represent the gradient values at the position (i, j) in matrix A and matrix B; and respectively represent the partial derivatives of matrix A in the x - direction and y - direction; and respectively represent the partial derivatives of matrix B in the x - direction and y - direction; A(i, j + 1)-A(i, j) represents the first - order difference of A in the x - direction; A(i + 1, j)-A(i, j) represents the first - order difference of A in the y - direction; B(i, j + 1)-B(i, j) represents the first - order difference of B in the x - direction; B(i + 1, j)-B(i, j) represents the first - order difference of B in the y - direction.

[0079] The gradient matrices GA and GB represent the fluctuation intensity at each position.

[0080] S5.3, calculate the overall fluctuation intensity of the magnetic field signal. The root - mean - square (RMS) is used to measure the overall fluctuation intensity:

[0081] ;

[0082] Wherein, in the formula, RMS A and RMS B respectively represent the root - mean - square values of matrix A and matrix B, measuring the overall fluctuation intensity; M and N respectively represent the number of rows and columns of the matrix; GA(i, j) and GB(i, j) respectively represent the gradient values at the position (i, j); 1 / (M×N) represents the average factor, which is the reciprocal of the total number of points in the matrix.

[0083] S5.4, identify the peaks in the magnetic field signal as suspected defect positions. A peak is a local maximum point that satisfies:

[0084] ;

[0085] Among them, the peak recognition is based on the principle of local maximum. A(i, j)>A(i-1, j), A(i, j)>A(i+1, j), A(i, j)>A(i, j-1), and A(i, j)>A(i, j+1) indicate that the value at position (i, j) is greater than the values at its four adjacent positions above, below, left, and right; the judgment condition for B(i, j) is similar, jointly realizing that the detected points are real local maximum points rather than fluctuations caused by noise.

[0086] Since noise may affect peak recognition, the following additional steps are required:

[0087] S5.4.1, perform smoothing filtering on the magnetic field signal. Use Gaussian filtering to remove local high-frequency noise:

[0088] ;

[0089] Among them, A s (i, j) and B s (i, j) respectively represent the values of the smoothed matrix A and matrix B at position (i, j); ω(m, n) represents the Gaussian weight function; m and n are the relative coordinates of the filtering window, ranging from -k to k.

[0090] Gaussian weight:

[0091] ;

[0092] Usually, σ≈1.5 is selected for smoothing.

[0093] S5.4.2, set the peak threshold. The screening criteria for peaks are:

[0094] ;

[0095] Among them, μA and σA are the mean and standard deviation of A s (i,j), μB and σB are the mean and standard deviation of matrix B s respectively; α is an adjustment parameter, usually taking a value of 1.5, used to select peaks within a certain range above the mean.

[0096] S5.4.3, calculate the distribution range of peaks. The distribution range of peaks can be determined by the region growing algorithm:

[0097] Take the local maximum point (i,j) as the seed point;

[0098] If the adjacent points satisfy , they are classified into the same peak region;

[0099] Calculate the center point, area, and average height of each peak region.

[0100] In the formula, |As(i', j') - As(i, j)| < ε indicates that the difference between the adjacent point and the seed point is less than the threshold ε, which is used to determine the boundary of the peak region.

[0101] Furthermore, it further includes the step: S6. Determine the measuring line and the axial position where the suspected defect is located according to the position of the suspected defect.

[0102] According to the matrix position where the peak is located, it can be determined which measuring line the defect is located on and which axial position on the measuring line.

[0103] S7. Perform a secondary inspection on the wrapped surface of the part with the maximum peak value.

[0104] Select the part with the maximum signal peak value and perform a more detailed inspection to confirm the defect situation. For bridge cables and rods, it may be necessary to cut open the wrapped surface to check whether the steel strands are broken or damaged.

[0105] The method for detecting defects by magnetic flux leakage provided in this embodiment can comprehensively capture the defect information on the surface and inside of the object to be detected by generating magnetic flux in a local area of the object to be detected and adopting a scanning strategy combining the axial direction and the circumference. This method consumes less power and is suitable for environments with difficult power supply; through multi-sensor differential detection and complex data processing algorithms, the reliability of defect detection is improved; by using peak recognition and analysis techniques, the defect position can be accurately located, providing precise guidance for subsequent maintenance. It is especially suitable for the detection of structures such as bridge cables and rods where it is difficult to directly observe the internal state.

[0106] Embodiment 2

[0107] The embodiment of the present invention provides a device for detecting defects by magnetic flux leakage. Please refer to Figure 2 , the device for detecting defects by magnetic flux leakage includes: a fixing mechanism 1, a moving mechanism 2, a magnetic field excitation device 4, a magnetic field detection device 3, and a data processing unit.

[0108] The fixing mechanism 1 is used to fix the device on the object to be detected. In this embodiment, when the object to be detected is a bridge cable and rod, the fixing mechanism 1 is a cable and rod fixing ring. The cable and rod fixing ring can firmly fix the device at a specific position of the cable and rod, realizing the stability of the device position during the detection process.

[0109] The moving mechanism 2 is connected to the fixed mechanism 1, and the moving mechanism 2 can move axially along the object to be detected and can perform circular motion around the object to be detected. In this embodiment, the moving mechanism 2 is a telescopic rod. The telescopic rod can be shortened and elongated, facilitating the device to scan along the axial direction of the object to be detected. At the same time, the telescopic rod can perform circular motion along the fixed ring, facilitating the scanning of the entire side of the object to be detected. In a specific example, the moving mechanism 2 includes a driving device for controlling the axial movement and circular motion of the moving mechanism 2.

[0110] The driving device can adopt driving methods such as motors, stepper motors or servo motors to achieve precise control, which belongs to the common means of those skilled in the art and will not be elaborated herein.

[0111] The magnetic field excitation device 4 is arranged at the end of the moving mechanism 2 for generating magnetic flux in a local area of the object to be detected. In this embodiment, the magnetic field excitation device 4 is a magnetic flux leakage excitation coil. The magnetic flux leakage excitation coil is closely attached to the surface of the object to be detected to generate local magnetic flux. Since it is not necessary to magnetize the entire cross-section of the object to be detected, the power of the magnetic flux leakage excitation coil is relatively small, and compared with traditional full cross-section magnetization, the weight of the device is significantly reduced.

[0112] In a specific example, the magnetic flux leakage excitation coil can be wound with a copper wire with 500 - 1000 turns and a wire diameter of 0.5 - 1.0 mm. The specific parameters can be adjusted according to the material and size of the object to be detected, which belongs to the common means of those skilled in the art and will not be elaborated herein.

[0113] The magnetic field detection device 3 is arranged near the magnetic field excitation device 4 for detecting magnetic field signals. In this embodiment, the magnetic field detection device 3 is a magnetic field differential detector, and the magnetic field differential detector includes at least two magnetic field electro-effect detection sensors arranged at intervals. When the amplitude of the alternating magnetic field is strong, the voltage peak value output by the magnetic field electro-effect detection sensor is higher, corresponding to the appearance of magnetic flux leakage characteristics.

[0114] In a specific example, the magnetic field electro-effect detection sensor can adopt Hall elements, magnetoresistive sensors, giant magnetoresistive sensors or tunneling magnetoresistive sensors, etc. Different sensors have different sensitivities and applicable ranges, and the appropriate sensor type can be selected according to specific application requirements.

[0115] The data processing unit is used to process the data collected by the magnetic field detection device 3. In this embodiment, the data processing unit includes a data acquisition module and a data analysis module. The data acquisition module is used to record the magnetic field signals on each measurement line, and the data analysis module is used to calculate the magnetic field gradient and identify the magnetic field peaks. The data processing unit can process the collected data in real time or store the data for offline analysis. In a specific example, the data processing unit can adopt an embedded processor such as ARM, DSP, etc., and cooperate with necessary storage and communication modules to implement the functions of data acquisition, processing, and transmission.

[0116] In addition, the device may further include a portable wind power generation device, which is used to provide power for the device. There is natural ventilation above the bridge all year round. Using the wind power generation device can supplement electrical energy for the detection device when it is on standby, and improve the working time of the device above the bridge. In a specific example, the portable wind power generation device can adopt a small wind turbine, and cooperate with necessary voltage stabilization and energy storage devices to provide continuous and stable power supply for the detection device.

[0117] During the operation of the device, first fix the device on the object to be detected through the fixing mechanism 1, start the magnetic field excitation device 4 to generate magnetic flux, and then control the moving mechanism 2 to move along the axis of the object to be detected, and collect the magnetic field signals on the first measurement line through the magnetic field detection device 3. After completing the scanning of the first measurement line, the moving mechanism 2 makes a circular motion around the object to be detected to the next measurement line position, and repeats the collection step until the scanning of the entire circle is completed. Finally, the data processing unit analyzes the collected magnetic field signals to determine the position of the suspected defect.

[0118] The device for detecting magnetic flux leakage defects provided in this embodiment adopts the principle of local magnetization, which greatly reduces the power demand; through the collaborative work of the fixing mechanism 1 and the moving mechanism 2, it realizes the omnidirectional scanning of the object to be detected; uses the portable wind power generation device to solve the power supply problem, and is suitable for working in high-altitude environments such as bridges for a long time; adopts the magnetic field differential detection technology to improve the detection sensitivity and anti-interference ability; the data processing unit can perform complex signal analysis to accurately identify the defect position. The overall design is light and practical, and is especially suitable for structures such as bridge cables and poles that are difficult to access and detect.

[0119] Embodiment Three

[0120] Based on Embodiment One and Embodiment Two, this embodiment provides an example description applied to the detection of bridge cables and poles.

[0121] Bridge cables are generally composed of multiple strands of steel wires, with a layer of protective material wrapped around the outside. Due to the multi-layer winding of the steel wires in the strand, uneven force distribution may occur, and in extreme cases, the steel wires may break or be damaged. The local fracture of the strand is difficult to detect externally and requires special detection methods for diagnosis.

[0122] The traditional method for detecting bridge cables diagnoses broken wires in the strand by the difference in magnetic flux, but there are problems such as difficult power supply and heavy and difficult-to-operate equipment on bridge cables. The magnetic flux leakage detection method and device provided in this embodiment only generate magnetic flux for local steel wires and require less power consumption. At the same time, by arranging a portable wind power generation device below the equipment, continuous replenishment is provided for the power supply to ensure long-term stay and work on bridge cables.

[0123] In specific operations, first fix the cable fixing ring on the bridge cable, and then drive the magnetic flux leakage excitation coil and the magnetic field differential detector to move along the axial direction of the cable through the telescopic rod to collect magnetic field signals. Please refer to Figure 3 , after completing the first measurement line Ⅰ, the telescopic rod makes a circular motion around the cable to the next position to perform the second measurement line Ⅱ, and then the telescopic rod makes a circular motion around the cable to the next position, and so on until the entire circumference is scanned.

[0124] Data processing includes steps such as signal normalization, gradient calculation, fluctuation intensity calculation, and peak recognition. Through these processes, the possible fracture or damage positions of the strands in the cable can be identified. For the part with the largest peak value, the cable wrapping surface can be cut open for inspection to see if repair is needed.

[0125] This method can accurately detect the broken wire defects in the strand, with high detection sensitivity and low false alarm rate. Compared with the traditional method, the detection efficiency is increased by about 30%, the equipment weight is reduced by about 50%, and the power consumption is reduced by about 60%.

[0126] In summary, a magnetic flux leakage detection defect method and device provided by the present invention, while improving the detection sensitivity and accuracy, significantly reduce the energy consumption and equipment weight, and improve the operation convenience, providing a practical and efficient technical solution for the field of structural safety monitoring.

[0127] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A method for detecting magnetic flux leakage defects, characterized in that, Including: Generating magnetic flux in a local area of the object to be detected; Moving along the axial direction of the object to be detected and collecting magnetic field signals on the first measurement line; Making a circular motion around the object to be detected to reach the position of the next measurement line; Repeating the collection step until the entire circumference of the object to be detected is scanned; And Analyzing the collected magnetic field signals to determine the positions of suspected defects in the object to be detected; Wherein, the analysis of the collected magnetic field signals includes: Performing normalization processing on the collected magnetic field signals; Calculating the local gradient of the magnetic field signals; Calculating the overall fluctuation intensity of the magnetic field signals; and Identifying the peaks in the magnetic field signals as the positions of suspected defects; Wherein, the calculation of the local gradient calculates the gradient of each point through first-order difference: ； ； Among them, G in the formula A (i, j) and G B (i, j) represent the gradient values at positions (i, j) in matrix A and matrix B, respectively; and represent the partial derivatives of matrix A in the x - direction and y - direction, respectively; and represent the partial derivatives of matrix B in the x - direction and y - direction, respectively; A(i, j + 1)-A(i, j) represents the first - order difference of A in the x - direction; A(i + 1, j)-A(i, j) represents the first - order difference of A in the y - direction; B(i, j + 1)-B(i, j) represents the first - order difference of B in the x - direction; B(i + 1, j)-B(i, j) represents the first - order difference of B in the y - direction; Wherein, the overall fluctuation intensity is calculated by the root mean square value: ； Among them, RMS in the formula A and RMS B respectively represent the root mean square values of matrix A and matrix B, measuring the overall fluctuation intensity; M and N respectively represent the number of rows and columns of the matrix; GA(i, j) and GB(i, j) respectively represent the gradient values at position (i, j); 1 / (M×N) represents the average factor, which is the reciprocal of the total number of points in the matrix.

2. The method according to claim 1, wherein The identification of the peaks in the magnetic field signals includes: Performing smoothing filtering processing on the magnetic field signals; Setting a peak threshold; and Calculating the distribution range of the peaks.

3. The method according to claim 1, characterized in that, It also includes: Determining the measurement line and axial position where the suspected defect is located according to the position of the suspected defect; and Performing a secondary inspection on the wrapped surface of the part with the largest peak value.

4. An apparatus for detecting magnetic flux leakage defects, which is used to implement the method described in any one of claims 1-3, and is characterized in that, Including: A fixing mechanism for fixing the device on the object to be detected; A moving mechanism connected to the fixing mechanism, the moving mechanism can move axially along the object to be detected and can make a circular motion around the object to be detected; A magnetic field excitation device arranged at the end of the moving mechanism for generating magnetic flux in a local area of the object to be detected; A magnetic field detection device arranged near the magnetic field excitation device for detecting magnetic field signals; And A data processing unit for processing the data collected by the magnetic field detection device; Wherein, the object to be detected is a bridge cable rod, the fixing mechanism is a cable rod fixing ring, the moving mechanism is a telescopic rod, the magnetic field excitation device is a magnetic flux leakage excitation coil, the magnetic field detection device is a magnetic field differential detector, and the magnetic field differential detector includes at least two magnetic field electro-effect detection sensors arranged at intervals.

5. The device according to claim 4, characterized in that, It also includes a portable wind power generation device for providing power for the device.

6. The device according to claim 4, characterized in that The moving mechanism includes a driving device for controlling the axial movement and circular motion of the moving mechanism; the data processing unit includes a data acquisition module and a data analysis module, the data acquisition module is used to record the magnetic field signals on each measurement line, and the data analysis module is used to calculate the magnetic field gradient and identify the magnetic field peaks.

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