Crack direction determination method based on bidirectional excitation weak magnetic detection device

Abstract

The present invention discloses a method for determining the direction of cracks based on a bidirectional excitation weak magnetic detection device, which belongs to the field of non-destructive testing technology. The device comprises a probe and a host computer; the probe comprises an excitation module, a signal acquisition and processing module, a shielding cover, and a shell; the excitation module comprises a cross-shaped magnetic yoke and an excitation coil, and the signal acquisition and processing module comprises a first circuit board and a second circuit board, with a magnetic sensor array arranged on the first circuit board; the excitation module, the signal acquisition and processing module, and the shielding cover are all arranged in the shell. The method for determining the direction of cracks comprises: (1) obtaining the distribution of three-dimensional magnetic field signals; (2) locating cracks according to the distortion of the magnetic field signals; and (3) determining the direction of cracks according to the relative position relationship of the magnetic field signals and a calculation formula. The purpose of the present invention is to perform bidirectional excitation magnetization on components, strengthen defect signals, and realize the detection of surface and internal crack directions in any direction.

Description

Technical Field

[0001] The present invention relates to the technical field of nondestructive testing, and in particular to a crack direction determination method based on a bidirectional excitation weak magnetic detection device. Background Art

[0002] Weak magnetic testing is a non-destructive testing method based on the metal magnetic memory effect. Unlike conventional metal magnetic memory testing, weak magnetic testing uses a low-intensity magnetic field to achieve local magnetization of ferromagnetic components, thereby enhancing defect signals and improving the signal-to-noise ratio.

[0003] Chinese patent CN118937469A provides a weak magnetic detection device for a component with a coating layer and a method for determining its excitation conditions. The weak magnetic detection signal is enhanced by a U-shaped magnetic yoke wound with an excitation coil, but the device can only apply an excitation magnetic field in one direction, making it difficult to detect cracks parallel to the direction of the magnetic field. At the same time, the device is only equipped with a set of sensors at the center, and multiple two-dimensional grid scans are required to determine the direction of the crack, which is a relatively cumbersome process. Chinese patent CN113092576A provides a metal magnetic memory detection device under weak magnetic field excitation and a method for using the device. It uses a cross-shaped magnetic yoke wound with an excitation coil to achieve bidirectional excitation, and is provided with a three-axis magnetoresistive sensor array with an oblique offset arrangement, which can expand the effective coverage area of ​​a single scan. However, the device can only obtain the approximate direction of the crack through a two-dimensional image, and has high requirements for the device and subsequent data processing. Chinese patent CN112964777A provides a dual-excitation detection method for surface crack direction. It uses an eddy current field that rotates with time to detect crack signals and uses an empirical formula to determine the crack direction. Due to the skin effect of eddy current detection, this method can only detect surface cracks, and the excitation conditions are complex, requiring high phase control of the excitation currents of the two-axis coils.

[0004] Therefore, there is currently a lack of a device and corresponding determination method that can detect the direction of surface and internal cracks and has a simple structure and easy operation. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a method for determining crack direction based on a bidirectional excitation weak magnetic detection device.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A bidirectional excitation weak magnetic detection device comprises a probe and a host computer; the probe comprises an excitation module, a signal acquisition and processing module, a shielding cover, and a housing; the excitation module comprises a cross-shaped magnetic yoke and an excitation coil, wherein the excitation coil is evenly wound around four crossbeam sections of the cross-shaped magnetic yoke; the signal acquisition and processing module comprises a first circuit board and a second circuit board, wherein a magnetic sensor array is arranged on the first circuit board, and the magnetic sensor array comprises five magnetic sensors, namely, a Z-direction magnetic sensor arranged in the center; two X-direction magnetic sensors X1 and X3; and two Y-direction magnetic sensors Y2 and Y4, which are arranged in pairs in a square shape around the Z-direction magnetic sensor across the mid-span.

[0008] Furthermore, the crack direction determination method based on the bidirectional excitation weak magnetic detection device includes the following steps:

[0009] Step 1: Obtain the distribution of three-dimensional magnetic field signals; place the probe on the surface of the workpiece to be measured, and use the host computer to control the application of direct current to the excitation coil, so that the workpiece to be measured is partially magnetized by the bidirectional excitation magnetic field, and the probe is pushed to scan at a uniform speed along the Y direction; the host computer records the magnetic field signals collected by the five magnetic sensors; the magnetic field signals collected by the five magnetic sensors are filtered; and the distribution curves of the magnetic field signals in the X, Y, and Z directions are drawn respectively;

[0010] Step 2: Locate the crack based on the magnetic field signal distortion. When the distribution curves of the X-, Y-, and Z-direction magnetic field signals show significant peak-to-valley changes at a certain point, it indicates that a crack defect exists there.

[0011] Step 3: Determine the crack direction based on the relative position relationship of the magnetic field signals and the calculation formula; define the peak or valley positions of the magnetic field signals of the magnetic sensors X1, X3, Y2 and Y4 as L X1 、 L X3 、 L Y2 and L Y4 ;when L Y2 ≤ L Y4 , indicating that the angle between the crack direction and the probe moving direction is -30 o ~30 o between; when L Y2 > L Y4 and L X1 ≤ L X3 , indicating that the angle between the crack direction and the probe moving direction is -45 o ~-30 obetween; when L Y2 > L Y4 and L X1 > L X3 , the angle between the crack direction and the probe moving direction can be calculated using the following formula:

[0012] ;

[0013] Where, α is the angle between the crack direction and the probe moving direction; H Xmax and H Ymax are the maximum values ​​of the magnetic field signals of the X-direction and Y-direction magnetic sensors respectively; H Xmin and H Ymin They are the minimum values ​​of the magnetic field signals of the X-direction and Y-direction magnetic sensors respectively.

[0014] Furthermore, the excitation module, shielding cover and signal acquisition and processing module are all centrally arranged in the shell, specifically: the shielding cover, cross-shaped magnetic yoke and circuit board 1 are all fixed on the bottom plate of the shell, and the shielding cover is kept at the bottom center of the cross-shaped magnetic yoke, and circuit board 1 is located at the bottom center of the shielding cover; circuit board 2 is arranged above the cross-shaped magnetic yoke.

[0015] Furthermore, a signal amplifier, a power conversion chip, a D / A converter, an A / D converter, a serial port chip and a single-chip microcomputer are arranged on the second circuit board.

[0016] Furthermore, the excitation coil and the first circuit board are electrically connected to the second circuit board respectively; and the second circuit board is electrically connected to the host computer.

[0017] Furthermore, the shell is made of non-metallic material, and the shielding cover is made of Permalloy material.

[0018] The beneficial effects of the present invention are:

[0019] (1) The cross-shaped magnetic yoke plus coil excitation method can apply a bidirectional excitation magnetic field to avoid the problem of missed detection caused by unidirectional magnetization; the coil is used for direct current excitation, which is simple and easy to control;

[0020] (2) The square array arrangement of magnetic sensors takes into account both spatial scanning and probe volume; the five magnetic sensors can independently collect three-dimensional magnetic field signals, eliminating redundant information and reducing equipment costs;

[0021] (3) The relative position relationship between two X-direction magnetic sensors and two Y-direction magnetic sensors and the empirical calculation formula are used to preliminarily determine the angle between the crack direction and the scanning direction. The method is simple, has low requirements for data processing, and is highly operational. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is an overall schematic diagram of the present invention.

[0023] Figure 2 It is a schematic diagram of the probe structure of the present invention.

[0024] Figure 3 is a schematic diagram of a magnetic sensor array.

[0025] Figure 4 is the distribution curve of the X-direction magnetic field signal.

[0026] Figure 5 It is the distribution curve of the Y-direction magnetic field signal.

[0027] Figure 6 is the distribution curve of the Z-direction magnetic field signal.

[0028] Among them, 1. probe, 2. host computer, 3. shielding cover, 4. shell, 5. cross-shaped magnetic yoke, 6. excitation coil, 7. circuit board 1, 8. circuit board 2, 9. magnetic sensor array, 10. workpiece to be measured, 11. signal amplifier, 12. power conversion chip, 13. D / A converter, 14. A / D converter, 15. serial port chip, 16. single-chip microcomputer. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0030] like Figure 1 、 Figure 2 and Figure 3 As shown, a bidirectional excitation weak magnetic detection device includes a probe 1 and a host computer 2; the probe 1 includes an excitation module, a signal acquisition and processing module, a shielding cover 3 and a housing 4; the excitation module consists of a cross-shaped magnetic yoke 5 and an excitation coil 6, and the excitation coil 6 is evenly wound on the four cross beams of the cross-shaped magnetic yoke 5; the signal acquisition and processing module consists of a circuit board 1 7 and a circuit board 2 8, and a magnetic sensor array 9 is arranged on the circuit board 1 7. Figure 3 As shown, the magnetic sensor array 9 includes five magnetic sensors, namely one Z-direction magnetic sensor, which is arranged in the center; two X-direction magnetic sensors X1 and X3, and two Y-direction magnetic sensors Y2 and Y4, which are arranged in pairs in a square across the center around the Z-direction magnetic sensor;

[0031] The crack direction determination method based on the bidirectional excitation weak magnetic detection device includes the following steps:

[0032] Step 1: Obtain the distribution of three-dimensional magnetic field signals; place the probe 1 on the surface of the workpiece 10 to be measured, and control the upper computer 2 to pass direct current to the excitation coil 6, so that the workpiece 10 to be measured is partially magnetized by the bidirectional excitation magnetic field, and the probe 1 is pushed to scan at a uniform speed along the Y direction; the upper computer 2 records the magnetic field signals collected by the five magnetic sensors; the magnetic field signals collected by the five magnetic sensors are filtered; and the distribution curves of the magnetic field signals in the X direction, Y direction and Z direction are drawn respectively, as shown in FIG. Figure 4 、 Figure 5 and Figure 6 shown.

[0033] Step 2: Locate the crack based on the magnetic field signal distortion; Figure 4 、 Figure 5 and Figure 6 As shown in FIG, when the distribution curves of the X-direction, Y-direction, and Z-direction magnetic field signals show a significant peak-to-valley change at a certain location, it indicates that a crack defect exists at this location.

[0034] Step 3: Determine the crack direction based on the relative position relationship of the magnetic field signals and the calculation formula; define the peak or valley positions of the magnetic field signals of the magnetic sensors X1, X3, Y2 and Y4 as L X1 、 L X3 、 L Y2 and L Y4 ;when L Y2 ≤ L Y4 , indicating that the angle between the crack direction and the probe moving direction is -30 o ~30 o between; when L Y2 > L Y4 and L X1 ≤ L X3 , indicating that the angle between the crack direction and the probe moving direction is -45 o ~-30 o between; when L Y2 > L Y4 and L X1 > L X3 , the angle between the crack direction and the probe moving direction can be calculated using the following formula:

[0035] ;

[0036] Where, α is the angle between the crack direction and the probe moving direction; H Xmax and H Ymax are the maximum values ​​of the magnetic field signals of the X-direction and Y-direction magnetic sensors respectively; H Xmin and H Ymin They are the minimum values ​​of the magnetic field signals of the X-direction and Y-direction magnetic sensors respectively.

[0037] like Figure 2 As shown, the excitation module, shielding cover 3 and signal acquisition and processing module are all centrally arranged in the shell 4. Specifically, the shielding cover 3, the cross-shaped magnetic yoke 5 and the circuit board 1 7 are all fixed on the bottom plate of the shell 4, and the shielding cover 3 is kept at the bottom center of the cross-shaped magnetic yoke 5, and the circuit board 1 7 is located at the bottom center of the shielding cover 3; the circuit board 2 8 is arranged above the cross-shaped magnetic yoke 5.

[0038] like Figure 2 As shown, circuit board 2 8 is equipped with a signal amplifier 11, a power conversion chip 12, a D / A converter 13, an A / D converter 14, a serial port chip 15, and a single-chip microcomputer 16. The excitation coil 6 and circuit board 1 7 are electrically connected to circuit board 2 8, which is in turn electrically connected to the host computer 2. The host computer 2 supplies power to the D / A converter 13 on circuit board 2 8 via a USB connection and controls the current delivered to the excitation coil 6 by the D / A converter 13. The serial port chip 15 on circuit board 2 8 is specifically a USB-to-serial port chip, used for data transmission and communication with the host computer 2.

[0039] The housing 4 is made of non-metallic material to avoid interference with the signals collected by the magnetic sensor array 9, and the shielding cover 3 is made of permalloy material to effectively shield a large amount of background magnetic field.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A crack direction determination method based on a bidirectional excitation weak magnetic detection device, characterized in that: The bidirectional excitation weak magnetic detection device includes a probe and a host computer; the probe includes an excitation module, a signal acquisition and processing module, a shielding cover and a shell; the excitation module consists of a cross-shaped magnetic yoke and an excitation coil, and the excitation coil is evenly wound on the four crossbeams of the cross-shaped magnetic yoke; the signal acquisition and processing module consists of a circuit board 1 and a circuit board 2, and a magnetic sensor array is arranged on the circuit board 1, and the magnetic sensor array includes 5 magnetic sensors, namely, a Z-direction magnetic sensor arranged in the center; two X-direction magnetic sensors X1 and X3, and two Y-direction magnetic sensors Y2 and Y4, which are arranged in pairs in a square shape around the Z-direction magnetic sensor in the middle of the span; the crack direction determination method includes the following steps: Step 1: Obtain the distribution of three-dimensional magnetic field signals; place the probe on the surface of the workpiece to be measured, and use the host computer to control the application of direct current to the excitation coil, so that the workpiece to be measured is partially magnetized by the bidirectional excitation magnetic field, and the probe is pushed to scan at a uniform speed along the Y direction; the host computer records the magnetic field signals collected by the five magnetic sensors; the magnetic field signals collected by the five magnetic sensors are filtered; and the distribution curves of the magnetic field signals in the X, Y, and Z directions are drawn respectively; Step 2: Locate the crack based on the magnetic field signal distortion. When the distribution curves of the X-, Y-, and Z-direction magnetic field signals show significant peak-to-valley changes at a certain point, it indicates that a crack defect exists there. Step 3: Determine the crack direction based on the relative position relationship of the magnetic field signals and the calculation formula; define the peak or valley positions of the magnetic field signals of the magnetic sensors X1, X3, Y2 and Y4 as L X1 、 L X3 、 L Y2 and L Y4 ;when L Y2 ≤ L Y4 , indicating that the angle between the crack direction and the probe moving direction is -30 o ~30 o between; when L Y2 > L Y4 and L X1 ≤ L X3 , indicating that the angle between the crack direction and the probe moving direction is -45 o ~-30 o between; when L Y2 > L Y4 and L X1 > L X3 , the angle between the crack direction and the probe moving direction can be calculated using the following formula: ； Where, α is the angle between the crack direction and the probe moving direction; H Xmax and H Ymax are the maximum values ​​of the magnetic field signals of the X-direction and Y-direction magnetic sensors respectively; H Xmin and H Ymin They are the minimum values ​​of the magnetic field signals of the X-direction and Y-direction magnetic sensors respectively.

2. The crack direction determination method based on the bidirectional excitation weak magnetic detection device according to claim 1 is characterized in that: The excitation module, the shielding cover and the signal acquisition and processing module are all centrally arranged in the shell. Specifically, the shielding cover, the cross-shaped magnetic yoke and the circuit board 1 are all fixed on the bottom plate of the shell, and the shielding cover is kept at the bottom center of the cross-shaped magnetic yoke, and the circuit board 1 is located at the bottom center of the shielding cover; the circuit board 2 is arranged above the cross-shaped magnetic yoke.

3. The crack direction determination method based on the bidirectional excitation weak magnetic detection device according to claim 1 is characterized in that: The second circuit board is provided with a signal amplifier, a power conversion chip, a D / A converter, an A / D converter, a serial port chip and a single chip microcomputer.

4. The crack direction determination method based on the bidirectional excitation weak magnetic detection device according to claim 1 is characterized in that: The excitation coil and the first circuit board are electrically connected to the second circuit board respectively; the second circuit board is electrically connected to the host computer.

5. The crack direction determination method based on the bidirectional excitation weak magnetic detection device according to claim 1 is characterized in that: The shell is made of non-metallic material, and the shielding cover is made of Permalloy material.

Images