Magnetic sheet crack detection method and system

Abstract

The present invention relates to the field of magnetic material detection technology, and in particular to a magnetic sheet crack detection method and system, the method comprising: placing a magnetic sheet to be detected in a uniform magnetic field generating device for magnetization, wherein the magnetic field strength of the magnetic field is selected according to the characteristics of the magnetic sheet to be detected; after the magnetization is completed, independent Hall effect sensors are placed around the magnetic sheet to be detected to simultaneously measure the magnetic field strength of the magnetic sheet in all directions; the obtained magnetic field strength is normalized and mapped to the grayscale value of the image pixel to construct a magnetic field strength image, the magnetic field gradient is calculated, and the magnetic field gradient amplitude image is determined based on the calculated magnetic field gradient; a judgment threshold is set based on the magnetic field gradient amplitude image, and the portion greater than the threshold is marked to determine the crack area and calculate the crack parameters. The present invention accurately detects the distribution of the magnetic field of the magnetic sheet and the crack condition of the magnetic sheet through a method combining data processing with magnetic field characteristics, thereby improving the efficiency, accuracy and automation level of magnetic sheet detection.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic material detection, and in particular to a magnetic sheet crack detection method and system. Background Art

[0002] Magnetic sheets are widely used in numerous fields, including electronics, electricity, and communications. During the production and use of magnetic sheets, cracks may develop on their surfaces due to various stresses, temperature fluctuations, and mechanical shock. These cracks can seriously affect the performance of the sheet, such as reducing magnetic permeability and increasing magnetic losses. They can even cause the sheet to fail, impacting the normal operation of the entire device or system.

[0003] Currently, commonly used methods for detecting cracks in magnetic disks include visual inspection, ultrasonic testing, and eddy current testing. Visual inspection is simple and easy to use, but has low accuracy and difficulty detecting small cracks. Ultrasonic testing requires specialized equipment and skilled operators, and is slow. Eddy current testing requires high surface flatness and is ineffective for complex-shaped magnetic disks. Therefore, it is necessary to develop a new magnetic disk crack detection method that improves detection accuracy, speed, and adaptability. Summary of the Invention

[0004] In view of the above-mentioned technical deficiencies, the present invention provides a magnetic sheet crack detection method and system.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for detecting cracks in a magnetic sheet is provided, the method comprising the following steps:

[0007] Step S10: placing the magnetic sheet to be tested in a uniform magnetic field generating device for magnetization, wherein the magnetic field strength is selected according to the characteristics of the magnetic sheet to be tested;

[0008] Step S20: After the magnetization is completed, independent Hall effect sensors are placed around the magnetic piece to be tested to simultaneously measure the magnetic field strength of the magnetic piece in all directions to obtain magnetic field strength data;

[0009] Step S30: normalizing the obtained magnetic field intensity data, calculating the magnetic field gradient, determining the magnetic field gradient amplitude based on the calculated magnetic field gradient, and mapping it to the grayscale value of the image pixel to construct a magnetic field amplitude image;

[0010] Step S40: setting a determination threshold according to the magnetic field gradient amplitude image, marking the portion greater than the threshold to determine the crack area and calculating the crack parameters;

[0011] The magnetic field strength in step S10 is selected based on the characteristics of the magnetic sheet to be tested, and the selected range is 1000 to 5000 A / m, including 1000 A / m and 5000 A / m.

[0012] In step S20, independent Hall effect sensors are placed around the magnetic sheet to be tested and simultaneously measure the magnetic field strength of the magnetic sheet in various directions. The Hall effect sensors are controlled by a program to start working synchronously, and a rectangular coordinate system is constructed with the magnetic sheet to be tested as the origin, including an x-axis and a y-axis. The magnetic field strength of the magnetic sheet in various directions is measured as the magnetic field strength in the x-axis and y-axis directions.

[0013] The magnetic sheet crack detection result output in step S40 includes no crack and crack presence; when the magnetic sheet crack detection result is crack presence, the position of the crack area on the magnetic sheet is marked and the calculated crack parameters are displayed.

[0014] Preferably, in step S10, the magnetic sheet to be tested is placed in a uniform magnetic field generating device for magnetization, and the steps include:

[0015] Magnetic sheet material analysis: Analyze the material composition or crystal structure of the magnetic sheet to be tested, determine the material composition to obtain the magnetic characteristic parameters, and determine the magnetic field strength of the magnetizing magnetic field based on the magnetic characteristic parameters;

[0016] Preparation of magnetic field generating device: Select electromagnetic magnetizer as the magnetic field generating device, use magnetic field strength meter to measure and calibrate the magnetic field strength generated by the device, and control the magnetic field error within ±5%;

[0017] Magnetization: Place the magnetic piece to be tested in the center of the uniform magnetic field area of ​​the uniform magnetic field generator, fix the magnetic piece with a magnetic piece fixing fixture, keep the surface of the magnetic piece to be tested perpendicular to the direction of the magnetic field, turn on the magnetic field generator, and make its magnetic field strength reach the magnetic field strength determined in the magnetic piece material analysis, and magnetize the magnetic piece to be tested.

[0018] Preferably, after the magnetization is completed in step S20, the input current of the magnetic field generating device is reduced so that the magnetic field strength is reduced to 0 A / m, and the reduction rate of the input current is 50 A / m·s. When the magnetic field strength is reduced to 0 A / m, the power supply of the magnetic field generating device is turned off, the magnetic sheet fixing fixture is moved to remove the magnetized magnetic sheet from the magnetic field generating device, and the magnetic field strength of the magnetic sheet after magnetization is measured.

[0019] Preferably, the step of normalizing the obtained magnetic field strength in step S30 is:

[0020] Traverse the obtained magnetic field strength data, select the maximum and minimum values ​​in the magnetic field strength data, and the normalization formula is shown in formula (1):

[0021]

[0022] Among them, B norm (x, y) is the normalized value of the point (x, y) in the magnetic field intensity data, B(x, y) is the magnetic field intensity at the point (x, y) in the magnetic field intensity data, and B min is the minimum value in the magnetic field strength data, B max is the maximum value in the magnetic field strength data, B norm The value range of (x, y) is between 0 and 1, excluding 0 and 1. All data in the magnetic field intensity data are traversed to complete the normalization operation.

[0023] Preferably, the step of calculating the magnetic field gradient in step S30, determining the magnetic field gradient amplitude according to the calculated magnetic field gradient, and mapping it into grayscale values ​​of image pixels to construct a magnetic field gradient amplitude image includes:

[0024] Determine the step size: The step size is determined based on the resolution of the Hall effect sensor and the size of the magnetic sheet, and the value range is 0.1 to 1 mm, including 0.1 mm and 1 mm;

[0025] Calculate the magnetic field gradient: Calculate the magnetic field gradient in the x-direction and y-direction respectively. The calculation formula of the magnetic field gradient in the x-direction is shown in formula (2):

[0026]

[0027] Among them, G x (x, y) is the magnetic field gradient at point (x, y) in the x-direction, Δx is the step length in the x-direction, and the gradient of the point in the x-direction, i.e., the rate of change of the magnetic field, is obtained by calculating the ratio of the difference in magnetic field intensity between two adjacent points on the x-axis to the step length. The formula for calculating the magnetic field gradient in the y-direction is shown in Equation (3):

[0028]

[0029] Among them, G y (x,y) is the magnetic field gradient at point (x,y) in the y direction, Δy is the step size in the y direction, and the gradient of the point in the x direction, i.e. the rate of change of the magnetic field, is obtained by calculating the ratio of the difference in magnetic field intensity between two adjacent points on the x-axis to the step size.

[0030] Calculate the gradient amplitude: Calculate the magnetic field gradient amplitude based on the calculated gradients in the x-direction and y-direction. The calculation formula is shown in formula (4):

[0031]

[0032] Where G(x,y) is the calculated magnetic field gradient amplitude, which reflects the overall change of the magnetic field intensity at that point in the plane;

[0033] Normalization: Normalize the calculated magnetic field gradient amplitude G(x,y), and traverse G(x,y) to determine the minimum magnetic field gradient amplitude G min and the maximum value of the magnetic field gradient amplitude G max , the calculation formula is shown in formula (5):

[0034]

[0035] Among them G norm (x,y) is the normalized magnetic field gradient amplitude at point (x,y);

[0036] Generate amplitude image: According to the calculated G norm (x, y) is mapped to grayscale values ​​using a linear mapping method. The minimum value of the magnetic field gradient amplitude is set to correspond to a grayscale value of 0, and the maximum value corresponds to a grayscale value of 255. The intermediate values ​​are mapped proportionally. The calculation formula is shown in Equation (6):

[0037] Gray(x,y)=G norm (x,y)×255 (6)

[0038] Gray(x,y) is the gray value mapped to the point (x,y). All normalized data are traversed to complete the image gray value mapping and obtain the magnetic field amplitude grayscale map.

[0039] Preferably, the step of setting a determination threshold according to the magnetic field gradient amplitude image, marking the portion greater than the threshold to determine the crack area, and calculating the crack parameters in step S40 includes:

[0040] Judgment threshold setting: According to the maximum and minimum values ​​of the magnetic disk crack size in the historical detection data and the characteristics of the magnetic disk to be detected, the judgment threshold T is set. The pixel point where G(x,y)>T is marked as the starting point of the crack area and marked as 1. The remaining pixel points are marked as 0, where G(x,y) is the calculated magnetic field gradient amplitude;

[0041] Region growing algorithm: Select one starting point from the starting points marked as crack regions as the starting point for region growth, start from the first starting point in the starting points marked as crack regions, and add them to a queue. When performing cyclic growth, select one pixel point from the queue as the current processing pixel point, and for each adjacent pixel point (x n ,y n ), calculate the difference ΔG between the magnetic field gradient amplitude and the current processing pixel point, and the calculation formula is shown in formula (7):

[0042] ΔG=|G(x n ,y n )-G(x,y)| (7)

[0043] Among them, G(x n ,y n ) is the point (x n ,y n ) at the magnetic field gradient amplitude; setting the growth area criterion, that is, setting the threshold of the difference in the magnetic field gradient amplitude of adjacent pixel points to ΔT, when ΔG<ΔT, the adjacent pixel points are merged into the crack area until no more growth occurs;

[0044] Repeated growth: Select the next starting point from the starting point marked as the crack area, and repeat the region growing algorithm steps until all the starting points marked as crack areas have completed region growth, and the crack area is determined;

[0045] Crack parameter calculation: Calculate crack parameters based on the determined crack area.

[0046] The step of calculating crack parameters according to the determined crack area includes:

[0047] Calculate the crack length: extract all pixel coordinates (x i ,y i ), i = 1, 2, ..., n, n is the number of pixels in the crack area, and the distance between any two points is calculated as shown in formula (8):

[0048]

[0049] Where d is the point (x i ,y i ) and point (x j ,y j ) between them, and select the maximum value d max as crack length;

[0050] Calculate the crack width: Based on the calculated crack length, determine the corresponding straight line direction as the length direction. For each pixel point on the crack area, calculate its perpendicular distance to the length direction straight line, and take the average value to obtain the crack width.

[0051] Calculate the crack area: Count the number of pixels N in the crack area, determine the area A corresponding to each pixel in the actual magnetic disk, and calculate the crack area using the formula S=N×A.

[0052] In addition, to achieve the above-mentioned object, the present invention further provides a magnetic sheet crack detection system, the magnetic sheet crack detection system comprising:

[0053] Magnetization module for the magnetic piece to be tested: the magnetic piece to be tested is placed in a uniform magnetic field generating device for magnetization. The magnetic field strength is selected according to the characteristics of the magnetic piece to be tested.

[0054] Magnetic field strength acquisition module for the magnetic piece to be tested: After magnetization is completed, independent Hall effect sensors are placed around the magnetic piece to be tested and simultaneously measure the magnetic field strength of the magnetic piece in all directions to obtain magnetic field strength data;

[0055] The magnetic field strength data preprocessing module of the magnetic disk to be tested is used to normalize the obtained magnetic field strength data, calculate the magnetic field gradient, determine the magnetic field gradient amplitude based on the calculated magnetic field gradient, and map it to the grayscale value of the image pixel to construct a magnetic field amplitude image;

[0056] The magnetic sheet crack detection and calculation module to be tested sets the judgment threshold according to the magnetic field gradient amplitude image, marks the part greater than the threshold to determine the crack area and calculates the crack parameters;

[0057] The magnetic field strength of the magnetic field in the magnetization module of the magnetic piece to be tested is selected according to the characteristics of the magnetic piece to be tested, and the selected range is 1000 to 5000 A / m, including 1000 A / m and 5000 A / m;

[0058] In the magnetic field strength acquisition module for the magnetic piece to be tested, independent Hall effect sensors are placed around the magnetic piece to be tested and simultaneously measure the magnetic field strength of the magnetic piece in various directions. The Hall effect sensors are controlled by a program to start working synchronously, and a rectangular coordinate system is constructed with the magnetic piece to be tested as the origin, including an x-axis and a y-axis. The magnetic field strength of the magnetic piece in various directions is measured as the magnetic field strength in the x-axis and y-axis directions.

[0059] The magnetic disk crack detection and calculation module outputs the magnetic disk crack detection results including no crack and crack presence; when the magnetic disk crack detection result is crack presence, the position of the crack area on the magnetic disk is marked and the calculated crack parameters are displayed.

[0060] In addition, to achieve the above-mentioned purpose, the present invention also proposes a magnetic sheet crack detection device, which includes: a memory, a processor, and programs such as a magnetic sheet crack detection algorithm stored on the memory and capable of running on the processor. The magnetic sheet crack detection algorithm and other programs are steps for implementing a magnetic sheet crack detection method as described above.

[0061] In addition, to achieve the above-mentioned purpose, the present invention also provides a computer program product, which includes programs such as a magnetic sheet crack detection algorithm. When the magnetic sheet crack detection algorithm and other programs are executed by a processor, a magnetic sheet crack detection method as described above is implemented.

[0062] The advantages and effects of the present invention are:

[0063] The proposed magnetic disk crack detection method and system utilizes data processing combined with magnetic field characteristics to quickly and accurately detect cracks on the disk surface and calculate relevant parameters. This method can be widely used for quality inspection and fault diagnosis during the production and use of magnetic disks. Automated image processing eliminates the need for human intervention, significantly saving time and labor costs, shortening the detection time for magnetic disk surface cracks, and improving detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0065] Figure 1 The present invention is a flow chart of a magnetic sheet crack detection method.

[0066] Figure 2 This is a structural schematic diagram of a magnetic sheet crack detection system of the present invention.

[0067] Figure 3 This is a schematic block diagram of the structure of an electronic device for detecting cracks in a magnetic sheet according to the present invention. DETAILED DESCRIPTION

[0068] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0069] The present invention provides a method for detecting cracks in a magnetic sheet, such as Figure 1 As shown, the following steps are included:

[0070] Step S10: placing the magnetic piece to be tested in a uniform magnetic field generating device for magnetization, wherein the magnetic field strength is selected according to the characteristics of the magnetic piece to be tested.

[0071] The magnetic field strength of the magnetic field in step S10 is selected according to the characteristics of the magnetic piece to be detected, and the selected range is 1000 to 5000 A / m, including 1000 A / m and 5000 A / m.

[0072] Specifically, in step S10, the magnetic sheet to be tested is placed in a uniform magnetic field generating device for magnetization, and the steps include:

[0073] Magnetic sheet material analysis: Analyze the material composition or crystal structure of the magnetic sheet to be tested, determine the material composition to obtain the magnetic characteristic parameters, and determine the magnetic field strength of the magnetizing magnetic field based on the magnetic characteristic parameters;

[0074] Preparation of magnetic field generating device: Select electromagnetic magnetizer as the magnetic field generating device, use magnetic field strength meter to measure and calibrate the magnetic field strength generated by the device, and control the magnetic field error within ±5%;

[0075] Magnetization: Place the magnetic piece to be tested in the center of the uniform magnetic field area of ​​the uniform magnetic field generator, fix the magnetic piece with a magnetic piece fixing fixture, keep the surface of the magnetic piece to be tested perpendicular to the direction of the magnetic field, turn on the magnetic field generator, and make its magnetic field strength reach the magnetic field strength determined in the magnetic piece material analysis, and magnetize the magnetic piece to be tested.

[0076] Step S20: After the magnetization is completed, independent Hall effect sensors are placed around the magnetic piece to be tested to simultaneously measure the magnetic field strength of the magnetic piece in all directions to obtain magnetic field strength data.

[0077] In step S20, independent Hall effect sensors are placed around the magnetic piece to be tested and the magnetic field strength of the magnetic piece in various directions is measured simultaneously. The Hall effect sensors are controlled by the program to start working synchronously, and a rectangular coordinate system is constructed with the magnetic piece to be tested as the origin, including the x-axis and the y-axis. The magnetic field strength of the magnetic piece in various directions is measured as the magnetic field strength in the x-axis and y-axis directions.

[0078] Specifically, after the magnetization is completed in step S20, the input current of the magnetic field generating device is reduced so that the magnetic field strength is reduced to 0 A / m, and the reduction rate of the input current is 50 A / m·s. When the magnetic field strength is reduced to 0 A / m, the power supply of the magnetic field generating device is turned off, and the magnetic sheet fixing fixture is moved to remove the magnetized magnetic sheet from the magnetic field generating device, and the magnetic field strength of the magnetic sheet after magnetization is measured.

[0079] Step S30: normalizing the obtained magnetic field intensity data, calculating the magnetic field gradient, determining the magnetic field gradient amplitude based on the calculated magnetic field gradient, and mapping it to the grayscale value of the image pixel to construct a magnetic field amplitude image.

[0080] Specifically, the step of normalizing the obtained magnetic field strength in step S30 is as follows:

[0081] Traverse the obtained magnetic field strength data, select the maximum and minimum values ​​in the magnetic field strength data, and the normalization formula is shown in formula (1):

[0082]

[0083] Among them, B norm(x, y) is the normalized value of the point (x, y) in the magnetic field intensity data, B(x, y) is the magnetic field intensity at the point (x, y) in the magnetic field intensity data, and B min is the minimum value in the magnetic field strength data, B max is the maximum value in the magnetic field strength data, B norm The value range of (x, y) is between 0 and 1, excluding 0 and 1. All data in the magnetic field intensity data are traversed to complete the normalization operation.

[0084] Specifically, the steps of calculating the magnetic field gradient in step S30, determining the magnetic field gradient amplitude according to the calculated magnetic field gradient, and mapping it to the grayscale value of the image pixel to construct the magnetic field gradient amplitude image include:

[0085] Determine the step size: The step size is determined based on the resolution of the Hall effect sensor and the size of the magnetic sheet, and the value range is 0.1 to 1 mm, including 0.1 mm and 1 mm;

[0086] Calculate the magnetic field gradient: Calculate the magnetic field gradient in the x-direction and y-direction respectively. The calculation formula of the magnetic field gradient in the x-direction is shown in formula (2):

[0087]

[0088] Among them, G x (x, y) is the magnetic field gradient at point (x, y) in the x-direction, Δx is the step length in the x-direction, and the gradient of the point in the x-direction, i.e., the rate of change of the magnetic field, is obtained by calculating the ratio of the difference in magnetic field intensity between two adjacent points on the x-axis to the step length. The formula for calculating the magnetic field gradient in the y-direction is shown in Equation (3):

[0089]

[0090] Among them, G y (x,y) is the magnetic field gradient at point (x,y) in the y direction, Δy is the step size in the y direction, and the gradient of the point in the x direction, i.e. the rate of change of the magnetic field, is obtained by calculating the ratio of the difference in magnetic field intensity between two adjacent points on the x-axis to the step size.

[0091] Calculate the gradient amplitude: Calculate the magnetic field gradient amplitude based on the calculated gradients in the x-direction and y-direction. The calculation formula is shown in formula (4):

[0092]

[0093] Where G(x,y) is the calculated magnetic field gradient amplitude, which reflects the overall change of the magnetic field intensity at that point in the plane;

[0094] Normalization: Normalize the calculated magnetic field gradient amplitude G(x,y), and traverse G(x,y) to determine the minimum magnetic field gradient amplitude G min and the maximum value of the magnetic field gradient amplitude G max , the calculation formula is shown in formula (5):

[0095]

[0096] Among them G norm (x,y) is the normalized magnetic field gradient amplitude at point (x,y);

[0097] Generate amplitude image: According to the calculated G norm (x, y) is mapped to grayscale values ​​using a linear mapping method. The minimum value of the magnetic field gradient amplitude is set to correspond to a grayscale value of 0, and the maximum value corresponds to a grayscale value of 255. The intermediate values ​​are mapped proportionally. The calculation formula is shown in Equation (6):

[0098] Gray(x,y)=G norm (x,y)×255 (6)

[0099] Gray(x,y) is the gray value mapped to the point (x,y). All normalized data are traversed to complete the image gray value mapping and obtain the magnetic field amplitude grayscale map.

[0100] Step S40: setting a determination threshold according to the magnetic field gradient amplitude image, marking the portion greater than the threshold to determine the crack area and calculate the crack parameters.

[0101] In step S40, the magnetic sheet crack detection result output includes no crack and crack presence; when the magnetic sheet crack detection result is crack presence, the position of the crack area on the magnetic sheet is marked and the calculated crack parameters are displayed.

[0102] Specifically, the steps of setting a determination threshold according to the magnetic field gradient amplitude image in step S40, marking the portion greater than the threshold to determine the crack area, and calculating the crack parameters include:

[0103] Judgment threshold setting: According to the maximum and minimum values ​​of the magnetic disk crack size in the historical detection data and the characteristics of the magnetic disk to be detected, the judgment threshold T is set. The pixel point where G(x,y)>T is marked as the starting point of the crack area and marked as 1. The remaining pixel points are marked as 0, where G(x,y) is the calculated magnetic field gradient amplitude;

[0104] Region growing algorithm: Select one starting point from the starting points marked as crack regions as the starting point for region growth, start from the first starting point in the starting points marked as crack regions, and add them to a queue. When performing cyclic growth, select one pixel point from the queue as the current processing pixel point, and for each adjacent pixel point (x n ,y n ), calculate the difference ΔG between the magnetic field gradient amplitude and the current processing pixel point, and the calculation formula is shown in formula (7):

[0105] ΔG=|G(x n ,y n )-G(x,y)| (7)

[0106] Among them, G(x n ,y n ) is the point (x n ,y n ) at the magnetic field gradient amplitude; setting the growth area criterion, that is, setting the threshold of the difference in the magnetic field gradient amplitude of adjacent pixel points to ΔT, when ΔG<ΔT, the adjacent pixel points are merged into the crack area until no more growth occurs;

[0107] Repeated growth: Select the next starting point from the starting point marked as the crack area, and repeat the region growing algorithm steps until all the starting points marked as crack areas have completed region growth, and the crack area is determined;

[0108] Crack parameter calculation: Calculate crack parameters based on the determined crack area.

[0109] The step of calculating crack parameters according to the determined crack area includes:

[0110] Calculate the crack length: extract all pixel coordinates (x i ,y i ), i = 1, 2, ..., n, n is the number of pixels in the crack area, and the distance between any two points is calculated as shown in formula (8):

[0111]

[0112] Where d is the point (x i ,y i ) and point (x j ,y j ) between them, and select the maximum value d max as crack length;

[0113] Calculate the crack width: Based on the calculated crack length, determine the corresponding straight line direction as the length direction. For each pixel point on the crack area, calculate its perpendicular distance to the length direction straight line, and take the average value to obtain the crack width.

[0114] Calculate the crack area: Count the number of pixels N in the crack area, determine the area A corresponding to each pixel in the actual magnetic disk, and calculate the crack area using the formula S=N×A.

[0115] In addition, the present invention also proposes a magnetic sheet crack detection system, please refer to Figure 2 , the magnetic sheet crack detection system comprises:

[0116] Magnetization module for the magnetic piece to be tested: the magnetic piece to be tested is placed in a uniform magnetic field generating device for magnetization. The magnetic field strength is selected according to the characteristics of the magnetic piece to be tested.

[0117] Magnetic field strength acquisition module for the magnetic piece to be tested: After magnetization is completed, independent Hall effect sensors are placed around the magnetic piece to be tested and simultaneously measure the magnetic field strength of the magnetic piece in all directions to obtain magnetic field strength data;

[0118] The magnetic field strength data preprocessing module of the magnetic disk to be tested is used to normalize the obtained magnetic field strength data, calculate the magnetic field gradient, determine the magnetic field gradient amplitude based on the calculated magnetic field gradient, and map it to the grayscale value of the image pixel to construct a magnetic field amplitude image;

[0119] The magnetic sheet crack detection and calculation module to be tested sets the judgment threshold according to the magnetic field gradient amplitude image, marks the part greater than the threshold to determine the crack area and calculates the crack parameters;

[0120] The magnetic field strength of the magnetic field in the magnetization module of the magnetic piece to be tested is selected according to the characteristics of the magnetic piece to be tested, and the selected range is 1000 to 5000 A / m, including 1000 A / m and 5000 A / m;

[0121] In the magnetic field strength acquisition module for the magnetic piece to be tested, independent Hall effect sensors are placed around the magnetic piece to be tested and simultaneously measure the magnetic field strength of the magnetic piece in all directions. The Hall effect sensors are controlled by a program to start working synchronously, and a rectangular coordinate system is constructed with the magnetic piece to be tested as the origin, including the x-axis and the y-axis. The magnetic field strength of the magnetic piece in all directions is measured as the magnetic field strength in the x-axis and y-axis directions.

[0122] Among them, the magnetic sheet crack detection and calculation module outputs the magnetic sheet crack detection results including no crack and crack presence; when the magnetic sheet crack detection result is crack presence, the position of the crack area on the magnetic sheet is marked and the calculated crack parameters are displayed.

[0123] The present application provides a magnetic sheet crack detection system that utilizes a magnetic sheet crack detection method described in the aforementioned embodiment, thereby resolving the technical issues of low efficiency and accuracy associated with conventional magnetic sheet crack detection methods. Compared to the prior art, the present application provides the same beneficial effects as the magnetic sheet crack detection method described in the aforementioned embodiment, and the remaining technical features of the present application are the same as those disclosed in the aforementioned embodiment, which are not further detailed here.

[0124] The present application provides a magnetic sheet crack detection device, which includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute a magnetic sheet crack detection method in the above-mentioned embodiment one.

[0125] Reference below Figure 3 , which shows a schematic structural diagram of a magnetic sheet crack detection device suitable for implementing an embodiment of the present application. A magnetic sheet crack detection device in an embodiment of the present application may include, but is not limited to, mobile terminals such as mobile phones, laptop computers, digital broadcast receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Descriptions), PMPs (Portable Media Players), and the like, as well as fixed terminals such as digital TVs and desktop computers. Figure 3 The magnetic sheet crack detection device shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present application.

[0126] Figure 3The magnetic disk crack detection device shown may include a processing system 1001 (e.g., a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes based on programs stored in a read-only memory (ROM) 1002 or programs loaded from a storage system 1003 into a random access memory (RAM) 1004. Various programs and data required for the operation of the magnetic disk crack detection device are also stored in RAM 1004. Processing system 1001, ROM 1002, and RAM 1004 are connected to each other via a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to the I / O interface 1006: an input system 1007 including, for example, a touch screen, a touchpad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; an output system 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; a storage system 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication system 1009. The communication system 1009 can allow a magnetic sheet crack detection device to communicate with other devices wirelessly or by wire to exchange data. Although the figure shows a magnetic sheet crack detection device with various systems, it should be understood that it is not required to implement or have all of the systems shown. More or fewer systems may be implemented or have instead.

[0127] In particular, according to the embodiments disclosed in the present application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, the embodiments disclosed in the present application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program comprising program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network via a communication system, or installed from a storage system 1003, or installed from a ROM 1002. When the computer program is executed by the processing system 1001, the above-mentioned functions defined in the method of the embodiment disclosed in the present application are executed.

[0128] The present application provides a magnetic sheet crack detection device that utilizes a magnetic sheet crack detection method described in the aforementioned embodiment, thereby resolving the technical issues of low efficiency and accuracy associated with conventional magnetic sheet crack detection methods. Compared to the prior art, the present application provides the same beneficial effects as the magnetic sheet crack detection method described in the aforementioned embodiment, and the remaining technical features of the present application are the same as those disclosed in the aforementioned embodiment, which are not further detailed here.

[0129] The various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any appropriate manner in any one or more embodiments or examples.

[0130] The present application also provides a computer program product, including a computer program, which implements the steps of the magnetic sheet crack detection method as described above when the computer program is executed by a processor.

[0131] The computer program product provided in this application can address the technical issues of low efficiency and low accuracy of conventional magnetic disk crack detection methods. Compared with the prior art, the beneficial effects of the computer program product provided in this application are the same as those of the magnetic disk crack detection method provided in the above embodiment, and are not further elaborated here.

[0132] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for detecting cracks in a magnetic sheet, characterized in that: The method comprises the following steps: Step S10: placing the magnetic sheet to be tested in a uniform magnetic field generating device for magnetization, wherein the magnetic field strength is selected according to the characteristics of the magnetic sheet to be tested; Step S20: After the magnetization is completed, independent Hall effect sensors are placed around the magnetic piece to be tested to simultaneously measure the magnetic field strength of the magnetic piece in all directions to obtain magnetic field strength data; Step S30: normalizing the obtained magnetic field intensity data, calculating the magnetic field gradient, determining the magnetic field gradient amplitude based on the calculated magnetic field gradient, and mapping it to the grayscale value of the image pixel to construct a magnetic field gradient amplitude image; Step S40: setting a determination threshold according to the magnetic field gradient amplitude image, marking the portion greater than the threshold to determine the crack area, calculating the crack parameters, and outputting the magnetic sheet crack detection result; The magnetic field strength of the magnetic field in step S10 is selected according to the characteristics of the magnetic piece to be detected, and the selected range is 1000A / m to 5000A / m, inclusive; In step S20, independent Hall effect sensors are placed around the magnetic piece to be tested and simultaneously measure the magnetic field strength of the magnetic piece in various directions. The Hall effect sensors are controlled by a program to start working synchronously, and a rectangular coordinate system is constructed with the magnetic piece to be tested as the origin, including an x-axis and a y-axis. The magnetic field strength of the magnetic piece in various directions is measured as the magnetic field strength in the x-axis and y-axis directions. The magnetic sheet crack detection result output in step S40 includes no crack and crack presence; when the magnetic sheet crack detection result is crack presence, the position of the crack area on the magnetic sheet is marked and the calculated crack parameters are displayed.

2. A magnetic sheet crack detection method according to claim 1, characterized in that: In step S10, the magnetic sheet to be tested is placed in a uniform magnetic field generating device for magnetization, and the steps include: Magnetic sheet material analysis: Analyze the material composition or crystal structure of the magnetic sheet to be tested, determine the material composition to obtain the magnetic characteristic parameters, and determine the magnetic field strength of the magnetizing magnetic field based on the magnetic characteristic parameters; Preparation of magnetic field generating device: Select electromagnetic magnetizer as the magnetic field generating device, use magnetic field strength meter to measure and calibrate the magnetic field strength generated by the device, and control the magnetic field error within ±5%; Magnetization: Place the magnetic piece to be tested in the center of the uniform magnetic field area of ​​the uniform magnetic field generator, fix the magnetic piece with a magnetic piece fixing fixture, keep the surface of the magnetic piece to be tested perpendicular to the direction of the magnetic field, turn on the magnetic field generator, and make its magnetic field strength reach the magnetic field strength determined in the magnetic piece material analysis, and magnetize the magnetic piece to be tested.

3. A magnetic sheet crack detection method according to claim 1, characterized in that: After the magnetization is completed in step S20, the input current of the magnetic field generating device is reduced to reduce the magnetic field strength to 0 A / m, and the reduction rate of the input current is 50 A / m·s. When the magnetic field strength is reduced to 0 A / m, the power supply of the magnetic field generating device is turned off, and the magnetic sheet fixing fixture is moved to remove the magnetized magnetic sheet from the magnetic field generating device, and the magnetic field strength of the magnetic sheet after the magnetization is completed is measured.

4. A magnetic sheet crack detection method according to claim 1, characterized in that: The step of normalizing the obtained magnetic field strength in step S30 is as follows: Traverse the obtained magnetic field strength data, select the maximum and minimum values ​​in the magnetic field strength data, and the normalization formula is shown in formula (1): Among them, B norm (x, y) is the normalized value of the point (x, y) in the magnetic field intensity data, B(x, y) is the magnetic field intensity at the point (x, y) in the magnetic field intensity data, and B min is the minimum value in the magnetic field strength data, B max is the maximum value in the magnetic field strength data, B norm The value range of (x, y) is between 0 and 1, excluding 0 and 1. All data in the magnetic field intensity data are traversed to complete the normalization operation.

5. The method for detecting cracks in a magnetic sheet according to claim 1, wherein: The steps of calculating the magnetic field gradient in step S30, determining the magnetic field gradient amplitude according to the calculated magnetic field gradient, and mapping it to the grayscale value of the image pixel to construct the magnetic field gradient amplitude image include: Determine the step size: The step size is determined based on the resolution of the Hall effect sensor and the size of the magnetic sheet, and the value range is 0.1 to 1 mm, including 0.1 mm and 1 mm; Calculate the magnetic field gradient: Calculate the magnetic field gradient in the x-direction and y-direction respectively. The calculation formula of the magnetic field gradient in the x-direction is shown in formula (2): Among them, G x (x, y) is the magnetic field gradient at point (x, y) in the x-direction, Δx is the step length in the x-direction, and the gradient of the point in the x-direction, i.e., the rate of change of the magnetic field, is obtained by calculating the ratio of the difference in magnetic field intensity between two adjacent points on the x-axis to the step length. The formula for calculating the magnetic field gradient in the y-direction is shown in Equation (3): Among them, G y (x,y) is the magnetic field gradient at point (x,y) in the y direction, Δy is the step size in the y direction, and the gradient of the point in the x direction, i.e. the rate of change of the magnetic field, is obtained by calculating the ratio of the difference in magnetic field intensity between two adjacent points on the x-axis to the step size. Calculate the gradient amplitude: Calculate the magnetic field gradient amplitude based on the calculated gradients in the x-direction and y-direction. The calculation formula is shown in formula (4): Where G(x,y) is the calculated magnetic field gradient amplitude, which reflects the overall change of the magnetic field intensity at that point in the plane; Normalization: Normalize the calculated magnetic field gradient amplitude G(x,y), and traverse G(x,y) to determine the minimum magnetic field gradient amplitude G min and the maximum value of the magnetic field gradient amplitude G max , the calculation formula is shown in formula (5): Among them G norm (x,y) is the normalized magnetic field gradient amplitude at point (x,y); Generate amplitude image: According to the calculated G norm (x, y) is mapped to grayscale values ​​using a linear mapping method. The minimum value of the magnetic field gradient amplitude is set to correspond to a grayscale value of 0, and the maximum value corresponds to a grayscale value of 255. The intermediate values ​​are mapped proportionally. The calculation formula is shown in Equation (6): Gray(x,y)=G norm (x,y)×255 (6) Gray(x,y) is the gray value mapped to the point (x,y). All normalized data are traversed to complete the image gray value mapping and obtain the magnetic field amplitude grayscale map.

6. A magnetic sheet crack detection method according to claim 1, characterized in that: The steps of setting a determination threshold according to the magnetic field gradient amplitude image, marking the portion greater than the threshold to determine the crack area, and calculating the crack parameters in step S40 include: Judgment threshold setting: According to the maximum and minimum values ​​of the magnetic disk crack size in the historical detection data and the characteristics of the magnetic disk to be detected, the judgment threshold T is set. The pixel point where G(x,y)>T is marked as the starting point of the crack area and marked as 1. The remaining pixel points are marked as 0, where G(x,y) is the calculated magnetic field gradient amplitude; Region growing algorithm: Select one starting point from the starting points marked as crack regions as the starting point for region growth, start from the first starting point in the starting points marked as crack regions, and add them to a queue. When performing cyclic growth, select one pixel point from the queue as the current processing pixel point, and for each adjacent pixel point (x n ,y n ), calculate the difference ΔG between the magnetic field gradient amplitude and the current processing pixel point, and the calculation formula is shown in formula (7): ΔG=|G(x n ,y n )-G(x,y)| (7) Among them, G(x n ,y n ) is the point (x n ,y n ) at the magnetic field gradient amplitude; setting the growth area criterion, that is, setting the threshold of the difference in the magnetic field gradient amplitude of adjacent pixel points to ΔT, when ΔG<ΔT, the adjacent pixel points are merged into the crack area until no more growth occurs; Repeated growth: Select the next starting point from the starting point marked as the crack area, and repeat the region growing algorithm steps until all the starting points marked as crack areas have completed region growth, and the crack area is determined; Crack parameter calculation: Calculate crack parameters based on the determined crack area.

7. A magnetic sheet crack detection method according to claim 6, characterized in that: The step of calculating crack parameters according to the determined crack area includes: Calculate the crack length: extract all pixel coordinates (x i ,y i ), i = 1, 2, ..., n, n is the number of pixels in the crack area, and the distance between any two points is calculated as shown in formula (8): Where d is the point (x i ,y i ) and point (x j ,y j ) between them, and select the maximum value d max as crack length; Calculate the crack width: Based on the calculated crack length, determine the corresponding straight line direction as the length direction. For each pixel point on the crack area, calculate its perpendicular distance to the length direction straight line, and take the average value to obtain the crack width. Calculate the crack area: Count the number of pixels N in the crack area, determine the area A corresponding to each pixel in the actual magnetic disk, and calculate the crack area using the formula S=N×A.

8. A magnetic sheet crack detection system, characterized in that: The magnetic sheet crack detection system comprises: Magnetization module for the magnetic piece to be tested: the magnetic piece to be tested is placed in a uniform magnetic field generating device for magnetization. The magnetic field strength is selected according to the characteristics of the magnetic piece to be tested. Magnetic field strength acquisition module for the magnetic piece to be tested: After magnetization is completed, independent Hall effect sensors are placed around the magnetic piece to be tested and simultaneously measure the magnetic field strength of the magnetic piece in all directions to obtain magnetic field strength data; The magnetic field strength data preprocessing module of the magnetic disk to be tested is used to normalize the obtained magnetic field strength data, calculate the magnetic field gradient, determine the magnetic field gradient amplitude based on the calculated magnetic field gradient, and map it to the grayscale value of the image pixel to construct a magnetic field amplitude image; The magnetic sheet crack detection and calculation module to be tested sets the judgment threshold according to the magnetic field gradient amplitude image, marks the part greater than the threshold to determine the crack area and calculates the crack parameters; The magnetic field strength of the magnetic field in the magnetization module of the magnetic piece to be tested is selected according to the characteristics of the magnetic piece to be tested, and the selected range is 1000 to 5000 A / m, including 1000 A / m and 5000 A / m; In the magnetic field strength acquisition module for the magnetic piece to be tested, independent Hall effect sensors are placed around the magnetic piece to be tested and simultaneously measure the magnetic field strength of the magnetic piece in various directions. The Hall effect sensors are controlled by a program to start working synchronously, and a rectangular coordinate system is constructed with the magnetic piece to be tested as the origin, including an x-axis and a y-axis. The magnetic field strength of the magnetic piece in various directions is measured as the magnetic field strength in the x-axis and y-axis directions. The magnetic disk crack detection and calculation module outputs the magnetic disk crack detection results including no crack and crack presence; when the magnetic disk crack detection result is crack presence, the position of the crack area on the magnetic disk is marked and the calculated crack parameters are displayed.

9. A magnetic sheet crack detection device, characterized in that: The magnetic sheet crack detection device comprises: A memory, a processor, and a magnetic sheet crack detection program stored in the memory and executable on the processor, wherein the magnetic sheet crack detection program, when executed by the processor, implements a magnetic sheet crack detection method as claimed in any one of claims 1 to 7.

10. A computer program product, characterized in that The computer program product includes a magnetic sheet crack detection program, and when the magnetic sheet crack detection program is executed by a processor, a magnetic sheet crack detection method according to any one of claims 1 to 7 is implemented.

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