Planar coil / TMR composite electromagnetic sensor, probe and application method for crack depth detection

Abstract

The present invention discloses a planar coil / TMR composite electromagnetic sensor, a probe and an application method for crack depth detection. The planar coil / TMR composite electromagnetic sensor for crack depth detection of the present invention comprises a support structure, an upper excitation coil, a lower excitation coil and a TMR magnetic sensitive element. Both the upper excitation coil and the lower excitation coil are planar coils, and the upper excitation coil and the lower excitation coil are arranged in parallel and symmetrically fixed on the support structure respectively. The TMR magnetic sensitive element is arranged between the upper excitation coil and the lower excitation coil, and the measurement direction of the TMR magnetic sensitive element coincides with the center line connecting the upper excitation coil and the lower excitation coil. The present invention can effectively detect characteristic information characterizing the crack depth of the metal surface, has the characteristics of high signal-to-noise ratio, high sensitivity and sensitivity not changing with the excitation frequency, and has the advantages of simple structure and convenient manufacturing.

Description

Technical Field

[0001] The present invention relates to a crack depth detection technology for metal components, and in particular to a planar coil / TMR (Tunnel Magneto Resistance) composite electromagnetic sensor, a probe and an application method for crack depth detection. Background Art

[0002] Metal components are subjected to alternating stress during use, and cracks are easily formed on their surfaces and inside. Cracks occur throughout the life cycle of metal components and are difficult to predict. The failure process of metals is composed of crack initiation, metastable expansion, and unstable expansion. Among them, the metastable expansion process accounts for a large proportion and is an important component that determines the failure process of metals. Effectively detecting cracks through technical means during the crack initiation period and performing technical repairs in a timely manner are of great significance for extending the service life of metal components. At present, the main method for repairing cracks in important metal parts is welding. Before welding, it is necessary to know the crack shape, size, depth and other parameters. The crack shape and size are easy to obtain through detection, but quantitative detection methods for crack depth are relatively lacking. Summary of the invention

[0003] Technical problem to be solved by the present invention: In view of the above-mentioned problems in the prior art, a planar coil / TMR composite electromagnetic sensor, probe and application method for crack depth detection are provided. The present invention can effectively detect characteristic information characterizing the crack depth on the metal surface, has the characteristics of high signal-to-noise ratio, high sensitivity and sensitivity that does not change with the excitation frequency, and has the advantages of simple structure and easy manufacturing.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A planar coil / TMR composite electromagnetic sensor for crack depth detection comprises a support structure, an upper excitation coil, a lower excitation coil and a TMR magnetic sensitive element, wherein both the upper excitation coil and the lower excitation coil are planar coils, and the upper excitation coil and the lower excitation coil are arranged in parallel and symmetrically fixed on the support structure, respectively, and the TMR magnetic sensitive element is arranged between the upper excitation coil and the lower excitation coil, and the measuring direction of the TMR magnetic sensitive element coincides with the center line connecting the upper excitation coil and the lower excitation coil.

[0006] Optionally, the upper excitation coil and the lower excitation coil are connected in series and reversely connected, so that when the input excitation signal is a sinusoidal alternating current, the upper excitation coil and the lower excitation coil excite excitation magnetic fields of equal magnitude and opposite direction in the direction of the center line.

[0007] Optionally, the supporting structure is a cylindrical structure.

[0008] Optionally, the upper excitation coil and the lower excitation coil are in the shape of spiral lines diverging from the center of a circle, and the centers of the spiral lines coincide with the centers of the circular end surfaces of the support structure.

[0009] Optionally, the upper excitation coil, the lower excitation coil and the circular end surface of the support structure are bonded and fixed by glue.

[0010] Optionally, the support structure is made by 3D printing.

[0011] A probe for crack depth detection comprises a shell and a crack depth detection sensor installed in the shell. The crack depth detection sensor is the aforementioned planar coil / TMR composite electromagnetic sensor for crack depth detection.

[0012] A preamplifier circuit unit is also arranged in the shell, and the preamplifier circuit unit is connected in series to the output end of the crack depth detection sensor.

[0013] A sinusoidal alternating current generator for generating sinusoidal alternating current is also arranged in the shell, and the output end of the sinusoidal alternating current generator is connected to the upper excitation coil and the lower excitation coil.

[0014] An application method of the above-mentioned planar coil / TMR composite electromagnetic sensor for crack depth detection, comprising: 1) inputting an excitation signal of a sinusoidal alternating current into an upper excitation coil and a lower excitation coil, so that the upper excitation coil and the lower excitation coil excite excitation magnetic fields of equal magnitude and opposite direction in the direction of a center line; 2) attaching the planar coil / TMR composite electromagnetic sensor for crack depth detection to the surface of a metal component to be detected, detecting the output signal amplitude of a TMR magnetic sensitive element, and querying a preset output signal amplitude-crack depth mapping table according to the output signal amplitude of the TMR magnetic sensitive element to obtain the crack depth on the surface of the metal component to be detected.

[0015] Compared with the prior art, the present invention mainly has the following advantages:

[0016] 1. The present invention can eliminate the influence of the excitation magnetic field and improve the signal-to-noise ratio of the sensor. By using two identical planar excitation coils (upper excitation coil and lower excitation coil) and applying anti-phase excitation, the magnetic fields generated by the upper excitation coil and the lower excitation coil at the midpoint of the line connecting the centers of the coils theoretically cancel each other out. Compared with other crack detection methods, the present invention can suppress the influence of the excitation magnetic field of the excitation coil itself, improve the signal-to-noise ratio of the sensor, and improve the ability to detect crack depth.

[0017] 2. The present invention uses TMR magnetic sensitive elements to measure the magnetic field at the center point. Compared with the coil as the detection unit, it has the characteristics of high sensitivity and the sensitivity does not change with the excitation frequency. At the same time, it simplifies the complexity of subsequent inversion of crack depth based on measuring the magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the three-dimensional structure of an electromagnetic sensor according to an embodiment of the present invention.

[0019] Figure 2 It is a schematic cross-sectional structure diagram of an electromagnetic sensor according to an embodiment of the present invention.

[0020] Figure 3 This is a magnetic field distribution diagram of the electromagnetic sensor after being excited in Example 1 of the present invention;

[0021] Figure 4 The actual effect of the electromagnetic sensor of the first embodiment of the present invention Figure 1 .

[0022] Figure 5 The actual effect of the electromagnetic sensor of the first embodiment of the present invention Figure 2 .

[0023] Legend: 1. Support structure; 2. Upper excitation coil; 3. Lower excitation coil; 4. TMR magnetic sensitive element. DETAILED DESCRIPTION

[0024] Embodiment 1:

[0025] like Figure 1 and Figure 2 As shown, this embodiment provides a planar coil / TMR composite electromagnetic sensor for crack depth detection, including a support structure 1, an upper excitation coil 2, a lower excitation coil 3 and a TMR magnetic sensitive element 4, wherein the upper excitation coil 2 and the lower excitation coil 3 are both planar coils, and the upper excitation coil 2 and the lower excitation coil 3 are arranged in parallel and symmetrically fixed on the support structure 1, respectively, and the TMR magnetic sensitive element 4 is arranged between the upper excitation coil 2 and the lower excitation coil 3, and the measuring direction of the TMR magnetic sensitive element 4 coincides with the center line connecting the upper excitation coil 2 and the lower excitation coil 3.

[0026] In this embodiment, the upper excitation coil 2 and the lower excitation coil 3 are reversely connected in series, so that when the input excitation signal is a sinusoidal alternating current, the upper excitation coil 2 and the lower excitation coil 3 excite excitation magnetic fields of equal magnitude and opposite directions in the direction of the center line. In this way, the excitation circuit structure of the upper excitation coil 2 and the lower excitation coil 3 can be simplified. Undoubtedly, different reverse excitations can be used for the upper excitation coil 2 and the lower excitation coil 3 as needed, so that the upper excitation coil 2 and the lower excitation coil 3 excite excitation magnetic fields of equal magnitude and opposite directions in the direction of the center line.

[0027] See also Figure 1 In this embodiment, the support structure 1 is a cylindrical structure. As an optional embodiment, the support structure 1 is made by 3D printing. For example, the 3D printing material used in this embodiment is photosensitive resin, and the center position is also marked on the upper and lower surfaces for easy alignment and positioning.

[0028] See also Figure 1 In this embodiment, the upper excitation coil 2 and the lower excitation coil 3 are spiral lines diverging from the center of the circle, and the centers of the circles coincide with the centers of the circular end faces of the support structure 1, ensuring that the upper excitation coil 2 and the lower excitation coil 3 excite excitation magnetic fields of equal magnitude and opposite directions in the direction of the center line. Figure 3 The example is simulated and analyzed by COMSOL simulation software in this embodiment. The excitation magnetic field of the coil after the excitation is added is shown in the figure. At the center point, there is no magnetic field component along the direction of the line connecting the center points of the coil. In this embodiment, the upper excitation coil 2, the lower excitation coil 3 and the circular end surface of the support structure 1 are fixed by glue. In addition, other methods can be used for fixing as needed.

[0029] When preparing the support structure 1, it is necessary to reserve space in the support structure 1 according to the size of the TMR magnetic sensitive element 4. The measurement direction of the TMR magnetic sensitive element 4 coincides with the line connecting the centers of the upper excitation coil 2 and the lower excitation coil 3, and the midpoint of the line is the measurement point of the TMR magnetic sensitive element 4. The upper excitation coil 2 and the lower excitation coil 3 are symmetrically attached to the upper and lower surfaces of the support structure 1, and are tightly attached with glue. The center of the coil strictly coincides with the center position of the mark of the support structure 1. The upper excitation coil 2 and the lower excitation coil 3 are connected in series and reversely, and the excitation signal is a sinusoidal alternating current. The upper excitation coil 2 and the lower excitation coil 3 excite equal and opposite excitation magnetic fields in the direction of the line connecting the centers of the two coils, and cancel each other out at the midpoint of the line. At this time, the magnetic field measured by the TMR magnetic sensitive element is zero.

[0030] In summary, the planar coil / TMR composite electromagnetic sensor for crack depth detection in this embodiment includes a support structure, an upper excitation coil, a lower excitation coil and a TMR magnetic sensitive element. Both the upper excitation coil and the lower excitation coil are planar coils, and the upper excitation coil and the lower excitation coil are arranged in parallel and symmetrically fixed on the support structure respectively. The TMR magnetic sensitive element is arranged between the upper excitation coil and the lower excitation coil (similar to a sandwich structure), and the measuring direction of the TMR magnetic sensitive element coincides with the center line connecting the upper excitation coil and the lower excitation coil, so that the upper excitation coil and the lower excitation line are aligned. The induced eddy currents generated by the two excitation coils in the metal being tested are superimposed at the center, and the change in magnetic field intensity at this point is detected by the TMR magnetic sensitive element to reflect the depth of the crack. The magnetic field component of the magnetic field generated by the upper excitation coil and the lower excitation coil at this point in the direction of the line connecting the center points of the two coils is zero. The TMR measuring the magnetic field in the direction of the line connecting the center points of the two coils is arranged at this point, which can reduce the influence of the background magnetic field, improve the signal-to-noise ratio, and effectively detect the characteristic information characterizing the depth of the crack on the metal surface. It has the characteristics of high signal-to-noise ratio, high sensitivity and sensitivity that does not change with the excitation frequency. It also has the advantages of simple structure and easy manufacturing.

[0031] In addition, this embodiment also provides a probe for crack depth detection, including a housing and a crack depth detection sensor installed in the housing, and the crack depth detection sensor is the aforementioned planar coil / TMR composite electromagnetic sensor for crack depth detection.

[0032] In addition, this embodiment also provides an application method of the aforementioned planar coil / TMR composite electromagnetic sensor for crack depth detection, including: 1) inputting an excitation signal of a sinusoidal alternating current into the upper excitation coil 2 and the lower excitation coil 3, so that the upper excitation coil 2 and the lower excitation coil 3 excite excitation magnetic fields of equal magnitude and opposite directions in the direction of the center line; 2) attaching the planar coil / TMR composite electromagnetic sensor for crack depth detection to the surface of the metal component to be detected, detecting the output signal amplitude of the TMR magnetic sensitive element 4, and querying a preset output signal amplitude-crack depth mapping table according to the output signal amplitude of the TMR magnetic sensitive element 4 to obtain the crack depth on the surface of the metal component to be detected.

[0033] Figure 4 and Figure 5 The following are the detection results (the output signal amplitude of the TMR magnetic sensitive element 4) of two metal components with different crack depths using the planar coil / TMR composite electromagnetic sensor for crack depth detection of this embodiment. Figure 4 and Figure 5It can be seen that the planar coil / TMR composite electromagnetic sensor for crack depth detection of this embodiment can intuitively detect defects of different depths. Different defect depths will cause the output signal amplitude to change significantly. The above relationship means that there is a corresponding mapping relationship between the output signal amplitude of the TMR magnetic sensitive element 4 and the crack depth. Based on the above mapping relationship, an output signal amplitude-crack depth mapping table can be pre-generated through experiments to detect the crack depth on the surface of the detected metal component.

[0034] Embodiment 2:

[0035] This embodiment is a further improvement on the probe of embodiment 1. In order to further improve the integration of the probe, a preamplifier circuit unit is further provided in the housing of this embodiment, and the preamplifier circuit unit is connected in series to the output end of the crack depth detection sensor, so that the preamplified signal can be directly output.

[0036] Embodiment three:

[0037] This embodiment is a further improvement of the probes of Embodiments 1 and 2. In order to further improve the integration of the probe, a sinusoidal alternating current generator for generating sinusoidal alternating current is further provided in the housing of this embodiment, and the output end of the sinusoidal alternating current generator is connected to the upper excitation coil 2 and the lower excitation coil 3, so that the probe integration is higher and the portability is further enhanced.

[0038] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A planar coil / TMR composite electromagnetic sensor for crack depth detection, characterized in that: The invention comprises a support structure (1), an upper excitation coil (2), a lower excitation coil (3) and a TMR magnetic sensitive element (4), wherein both the upper excitation coil (2) and the lower excitation coil (3) are planar coils, and the upper excitation coil (2) and the lower excitation coil (3) are arranged in parallel and symmetrically fixed on the support structure (1), and the TMR magnetic sensitive element (4) is arranged between the upper excitation coil (2) and the lower excitation coil (3), and the measurement direction of the TMR magnetic sensitive element (4) is parallel to the upper excitation coil (2) and the lower excitation coil (3). The center lines of the upper excitation coil (2) and the lower excitation coil (3) coincide with each other, and the upper excitation coil (2) and the lower excitation coil (3) are connected in series and reversely connected, so that when the input excitation signal is a sinusoidal alternating current, the upper excitation coil (2) and the lower excitation coil (3) excite excitation magnetic fields of equal magnitude and opposite directions in the direction of the center line; the upper excitation coil (2) and the lower excitation coil (3) are in the shape of spiral lines that diverge from the center of the circle, and the centers of the circles coincide with the centers of the circular end faces of the support structure (1).

2. The planar coil / TMR composite electromagnetic sensor for crack depth detection according to claim 1, characterized in that: The support structure (1) is a cylindrical structure.

3. The planar coil / TMR composite electromagnetic sensor for crack depth detection according to claim 2, characterized in that: The upper excitation coil (2), the lower excitation coil (3) and the circular end surface of the support structure (1) are bonded and fixed by glue.

4. The planar coil / TMR composite electromagnetic sensor for crack depth detection according to claim 3, characterized in that: The support structure (1) is made by 3D printing.

5. A probe for crack depth detection, comprising a housing and a crack depth detection sensor installed in the housing, characterized in that: The crack depth detection sensor is a planar coil / TMR composite electromagnetic sensor for crack depth detection as described in any one of claims 1 to 4.

6. The crack depth detection probe according to claim 5, characterized in that: A preamplifier circuit unit is also arranged in the shell, and the preamplifier circuit unit is connected in series to the output end of the crack depth detection sensor.

7. The crack depth detection probe according to claim 6, characterized in that: A sinusoidal alternating current generator for generating sinusoidal alternating current is also provided in the housing, and an output end of the sinusoidal alternating current generator is connected to the upper excitation coil (2) and the lower excitation coil (3).

8. A method for using the planar coil / TMR composite electromagnetic sensor for crack depth detection according to any one of claims 1 to 4, characterized in that: include: 1) An excitation signal of a sinusoidal alternating current is input to an upper excitation coil (2) and a lower excitation coil (3), so that the upper excitation coil (2) and the lower excitation coil (3) excite excitation magnetic fields of equal magnitude and opposite direction in the direction of a center line; 2) A planar coil / TMR composite electromagnetic sensor for crack depth detection is attached to the surface of a metal component to be detected, and the output signal amplitude of a TMR magnetic sensitive element (4) is detected. According to the output signal amplitude of the TMR magnetic sensitive element (4), a preset output signal amplitude-crack depth mapping table is queried to obtain the crack depth on the surface of the metal component to be detected.

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