Adaptive eddy current testing probe for curved surfaces, non-destructive testing instrument and its testing method

Abstract

This invention relates to the field of electromagnetic nondestructive testing (NDT), specifically to a surface-adaptive eddy current testing probe, a nondestructive testing instrument, and a testing method. The eddy current testing probe includes a magnetic core bundle, an excitation coil, and an induction coil. The magnetic core bundle is composed of multiple closely packed ferromagnetic needles; the excitation coil and induction coil radially limit the magnetic core bundle. The excitation coil is wound around the end of the magnetic core bundle furthest from the detection surface and is used to connect to an adjustable power supply. The excitation coil uses the adjustable power supply to generate an alternating magnetic field for detection in the target area, and uses the adjustable power supply to magnetize the magnetic core bundle so that the detection surface of the eddy current testing probe is tightly attracted to the target area of ​​the object being tested. The induction coil is wound around the end of the magnetic core bundle closest to the detection surface and is used to sense the signal generated by the object being tested during the testing process. This invention solves the problem that existing electromagnetic NDT probes cannot conform to various complex curved surfaces, leading to signal attenuation and affecting measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic nondestructive testing, and in particular to a surface-adaptive eddy current testing probe, a nondestructive testing instrument, and a corresponding method for testing complex curved surface structures and a paint film thickness measuring instrument. Background Technology

[0002] Eddy current testing is a technique for non-destructive testing of materials. It generates an alternating detection magnetic field in a designated area of ​​the object under test by an excitation coil, and detects this induced magnetic field through an induction coil. The flaw detection is then performed based on the analysis of the electromagnetic properties of the induced magnetic field. Conventional electromagnetic non-destructive testing probes are based on a coil core, typically made of soft magnetic materials such as silicon steel, ferrite, or polonium-mortite. This core has a fixed shape, and when inspecting curved surfaces such as welds, the core cannot fit snugly against the surface, resulting in a large lift-out value for the electromagnetic sensor and severe attenuation of the electromagnetic signal; this also affects the reliability of the final flaw detection results. Summary of the Invention

[0003] To address the problem that existing electromagnetic nondestructive testing probes cannot conform to various complex curved surfaces and are prone to signal attenuation due to large lift-off values, this invention provides a surface-adaptive eddy current testing probe, a nondestructive testing instrument, and a testing method thereof.

[0004] The technical solution provided by this invention is as follows:

[0005] An adaptive eddy current detection probe includes a magnetic core bundle, an excitation coil, and an induction coil. The magnetic core bundle consists of multiple smooth magnetic needles made of ferromagnetic material arranged parallel to each other in a close-packed manner. The excitation coil and the induction coil are wound around the magnetic core bundle to radially confine the magnetic needles into a bundle while allowing them to slide relative to each other axially. The excitation coil is connected to an adjustable power supply; the excitation coil uses the adjustable power supply to generate an alternating magnetic field for detection in the target area, and can also use the adjustable power supply to magnetize the magnetic core bundle so that the detection surface of the eddy current detection probe is tightly attracted to the target area of ​​the object being measured. The induction coil is used to sense and output the signal generated by the object being measured during the detection process.

[0006] As a further improvement of the present invention, the adjustable power supply outputs a DC signal with a preset current intensity before detection to achieve adsorption; and outputs an alternating signal to generate a preset detection magnetic field during detection.

[0007] In another approach, the adjustable power supply can also output a current signal that includes both AC and DC components, so that the magnetic needle is magnetized and attracted to the surface of the object being tested, generating a preset detection magnetic field in the target area of ​​the object being tested.

[0008] As a further improvement of the present invention, the excitation coil is wound in the magnetic core bundle at the end away from the detection surface; the induction coil is wound in the magnetic core bundle at the end close to the detection surface.

[0009] As a further improvement of the present invention, the magnetic needle is a cylindrical magnetic needle with a uniform wire diameter.

[0010] As a further improvement of the present invention, the magnetic needle is a cylindrical magnetic needle.

[0011] As a further improvement of the present invention, the magnetic needle is made of ferrite, polonium-mortite alloy or silicon steel.

[0012] As a further improvement of the present invention, the surface-adaptive eddy current detection probe also includes a limiting member, which has two switchable working states, including a free state that allows the magnetic needles to slide relative to each other, and a limiting state that fixes the relative position of the magnetic needles.

[0013] As a further improvement of the invention, the limiting member includes a retractable sleeve; the sleeve is made of a non-ferromagnetic material and is fitted over the limiting member. The sleeve is loosened before testing to allow relative sliding of the magnetic needles; and the sleeve is tightened during testing to fix the relative positions of the magnetic needles.

[0014] As a further improvement of the present invention, the limiting member includes a mounting base made of flexible material. The mounting base is honeycomb-shaped and contains multiple through holes, the diameter of which matches the outer diameter of the magnetic needles. The magnetic needles are inserted into the through holes. After being deformed under pressure, the mounting base fixes the relative position of each magnetic needle and allows the magnetic needles to slide relative to each other when the mounting base recovers its deformation.

[0015] As a further improvement of the present invention, the limiting member includes an end cap and an elastic film fixed inside it; the end cap is sleeved on the end of the magnetic core bundle; the end of each magnetic needle away from the detection surface is bonded to the elastic film; the elastic film deforms when the magnetic needles slide relative to each other, and the deformation recovery of the elastic film allows each magnetic needle to return to its original position.

[0016] This invention also includes a non-destructive testing instrument, comprising: an eddy current testing probe, an adjustable power supply, a signal receiver, and a data processing module. The eddy current testing probe is the aforementioned surface-adaptive eddy current testing probe. The adjustable power supply is electrically connected to the excitation coil of the eddy current testing probe and is used to output a dynamically adjustable current signal. The current signal output by the adjustable power supply magnetizes the magnetic core bundle, causing the detection surface of the eddy current testing probe to be tightly attracted to the target area of ​​the object being tested; and generating an alternating magnetic field for detection in the target area.

[0017] The signal receiver is electrically connected to the induction coil and senses the signal generated by the object under test during the detection process. The data processing module acquires the signal received by the signal receiver, performs signal analysis and analog-to-digital conversion, and then generates the required detection results.

[0018] As a further improvement of the present invention, the signal receiver includes a conditioning circuit and a sampling circuit; the conditioning circuit is used to filter and amplify the acquired signal; the sampling circuit is used to sample the output of the coil through signal A / D conversion.

[0019] As a further improvement of the present invention, the non-destructive testing instrument also includes a display component, which is electrically connected to the data processing module and is used to visualize the detection results.

[0020] This invention also includes a flaw detection method for complex curved surface structures. This method requires the use of a non-destructive testing instrument as described above to complete the detection task. The method includes two modes:

[0021] The first mode is:

[0022] Before starting the test, switch the limiting device of the eddy current detection probe to the free state; output a current signal containing both AC and DC components through the adjustable power supply, so that the detection surface of the magnetic core bundle is magnetically attracted to the object under test and adaptively deforms. After the test is completed in the magnetic attraction state, turn off the adjustable power supply; finally, after each magnetic needle in the magnetic core bundle is reset, switch the limiting device back to the limiting state.

[0023] The second mode is:

[0024] Before starting the test, switch the limiting device of the eddy current detection probe to the free state. Output a DC signal through the adjustable power supply to magnetically attract the detection surface of the magnetic core bundle to the object under test and allow it to adapt to deformation. Then switch the limiting device to the limiting state to maintain the current shape of the magnetic core bundle. Next, switch the output of the adjustable power supply to an alternating signal to complete the test. Then, turn off the adjustable power supply and switch the limiting device to the free state to reset each magnetic needle in the magnetic core bundle. Finally, switch the limiting device to the limiting state.

[0025] The present invention also includes a paint film thickness measuring instrument, which employs a surface-adaptive eddy current measuring probe as described above.

[0026] The present invention has the following beneficial effects:

[0027] This invention designs an improved eddy current detection probe, which replaces the iron core in the original coil with a magnetic core bundle composed of multiple magnetic needles with magnetic permeability. This allows the shape of the detection surface at the magnetic suction end to adaptively adjust to the surface morphology of the object being measured while retaining the original magnetic field enhancement performance. This eliminates the lift-off zone between the probe and the object being measured, overcomes the magnetic field attenuation problem caused by the lift-off effect in the original probe, and improves the detection accuracy.

[0028] This invention also adjusts the shape, structure, and input signal of the coil in the original eddy current detection probe, enabling the magnetic core bundle to achieve automated and rapid shape switching before detection using magnetic adsorption. Furthermore, it effectively maintains its optimal shape during measurement and remains tightly bonded to the object being measured, thereby enabling continuous measurement of non-uniform surfaces using this eddy current detection probe. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the surface-adaptive eddy current detection probe provided in Embodiment 1 of the present invention.

[0030] Figure 2 This is a schematic diagram of the measurement state of a traditional eddy current detection probe in a curved surface scene.

[0031] Figure 3 This is a schematic diagram of the measurement principle of the surface-adaptive eddy current detection probe provided in Embodiment 1 of the present invention on a curved surface.

[0032] Figure 4 This is a schematic diagram of the eddy current detection probe with curved surface adaptive of the hoop-type limiting component used in Embodiment 1 of the present invention.

[0033] Figure 5 This is a schematic diagram of the curved adaptive eddy current detection probe using a mounting base type limiting component in Embodiment 1 of the present invention.

[0034] Figure 6 This is a schematic diagram of the surface adaptive eddy current detection probe using an end cap-type limiting component in Embodiment 1 of the present invention.

[0035] Figure 7 This is a schematic diagram of the non-destructive testing instrument provided in Embodiment 1 of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0038] Example 1

[0039] Traditional coil-core eddy current testing probes suffer from limitations due to the inability of the core end face to adapt to complex curved surfaces of varying shapes. This results in an uneven gap between the probe and the measured object, leading to a lift-off effect during detection and rapid attenuation of the electromagnetic signal within the lift-off space. This embodiment provides a surface-adaptive eddy current testing probe. The probe uses a bundle of magnetic needles forming the core, which can slide relative to each other along the axial (length) direction. By magnetizing the needles during the measurement phase, each needle can adhere to the curved surface of the workpiece, achieving a close fit to various complex surface structures and realizing zero lift-off, effectively solving the signal attenuation problem of traditional probes.

[0040] Specifically, such as Figure 1 As shown, the surface-adaptive eddy current detection probe provided in this embodiment includes a magnetic core bundle, an excitation coil, and an induction coil. The magnetic core bundle consists of multiple smooth magnetic needles arranged closely together in parallel; the magnetic needles are made of ferromagnetic material. In practical applications, the magnetic needles can be made of ferrite, polonium-mortise alloy, silicon steel, or other common materials with high magnetic permeability.

[0041] The excitation coil and induction coil are wound around the magnetic core bundle to radially confine the individual magnetic needles into a bundle, while allowing the needles to slide relative to each other axially. The excitation coil is used to connect to an adjustable power supply; the excitation coil uses the adjustable power supply to generate an alternating magnetic field for detection in the target area, and can also use the adjustable power supply to magnetize the magnetic core bundle so that the detection surface of the eddy current detection probe is tightly attracted to the target area on the surface of the object being measured. The induction coil is used to sense and output the signal generated by the object being measured during the detection process.

[0042] In the solution provided in this embodiment, the positions of the excitation coil and the induction coil on the magnetic core bundle are not limited. However, in a more optimized solution, the excitation coil is wound around the end of the magnetic core bundle furthest from the detection surface; the induction coil is wound around the end of the magnetic core bundle closest to the detection surface. This allows the induction coil to be closer to the object being measured and enhances the strength of its output signal.

[0043] The schematic diagram of a traditional eddy current testing probe is as follows: Figure 2As shown, the probe consists of a coil and an iron core. When using this eddy current detection probe to perform flaw detection on a sample, the iron core can be attached to the sample surface. Applying an alternating current to the coil generates an alternating magnetic field around it. The iron core in the center of the coil is made of a highly permeable magnetic material, which concentrates and enhances the magnetic field within the coil, significantly increasing the magnetic induction intensity and avoiding magnetic induction intensity loss due to leakage flux. Under the influence of the alternating magnetic field, eddy currents are induced within the sample, simultaneously generating a magnetic field opposite in direction to the original magnetic field, partially canceling the original magnetic field and causing a change in the coil's impedance. Furthermore, since internal defects in the workpiece affect the induced eddy currents and the change in coil impedance, the differences in coil impedance changes in different regions during the detection process can be used to perform inversion analysis of the sample's internal microstructure, thereby achieving non-destructive testing of the workpiece.

[0044] When traditional eddy current testing probes are used for flaw detection on non-uniform surfaces, they may exhibit issues such as localized protrusions or depressions. Figure 2 As shown, an unevenly distributed gap is generated between the probe and the sample. This gap leads to a lift-off effect, which interferes with defect identification in the field of non-destructive testing based on eddy current detection. Furthermore, the dynamic change of the lift-off distance of the uneven surface further deteriorates the detection effect.

[0045] The schematic diagram of the improved surface-adaptive eddy current detection probe in this embodiment is as follows: Figure 3 As shown. This embodiment uses a magnetic core bundle composed of multiple magnetic needles instead of the original block iron core; the magnetic core bundle can achieve magnetic field concentration and enhancement in the same way as a traditional iron core. However, structurally, in this embodiment, each magnetic needle in the magnetic core bundle can slide freely along the axial direction. Therefore, when applied to non-uniform structural surfaces, the relative height of the ends of each magnetic needle can be flexibly adjusted, ensuring that the end of each magnetic needle is in close contact with the surface of the object being measured. Thus, as can be seen... Figure 3 As shown, when the magnetic core bundle of this embodiment is applied to non-uniform surface detection, the detection surface of the magnetic core bundle will exhibit a "fluid"-like shape, thereby achieving close contact with the measured surface through local shape changes, achieving the technical effect of "zero lift-off", and overcoming the attenuation problem caused by the lift-off effect in traditional solutions.

[0046] To ensure the magnetic core bundle maintains close contact with the object under various detection conditions, this embodiment modifies the structure of the original eddy current detection probe. An added component allows the magnetic needle to be magnetized during use, enabling it to adhere tightly to the object under test via magnetic attraction. Therefore, regardless of the probe's orientation (e.g., measuring the object above or below), the two objects remain in close contact without spontaneous detachment. Specifically, the structural improvement in this embodiment involves replacing the single coil in the traditional eddy current detection probe with a double coil positioned at both ends of the magnetic needle's axis. The coil furthest from the detection surface serves as the excitation coil, receiving the current signal from an external power supply and performing a dual function:

[0047] The first step is to magnetize the magnetic core bundle. At this point, both ends of each magnetic needle become magnetic poles, and the end faces of all the needles (i.e., the detection surfaces of the magnetic core bundle) will adhere tightly to the surface of the object being measured through magnetic attraction. In practical applications, to produce a stable magnetic attraction effect, the external power supply should input a DC signal of a preset strength.

[0048] Secondly, an alternating magnetic field (also called a detection magnetic field) is applied to the object under test during the detection process. The applied alternating magnetic field is used to induce a magnetic field in the object under test, thereby completing the corresponding flaw detection task. In practical applications, in order to realize the eddy current detection function, an AC signal should be input to the external power supply.

[0049] The end of the dual coil closest to the magnetic core bundle detection surface is the induction coil, which is used to detect the magnetic field generated by the eddy current induced in the sample under test, which is opposite in direction to the original magnetic field (the detection field generated by the excitation coil at this time), and outputs the corresponding detection signal in combination with its own impedance change.

[0050] To verify the feasibility of the strategy adopted in this embodiment, which uses magnetic attraction to make the magnetic core bundle and the object under test come into close contact, the following mechanical analysis of the magnetic attraction process is performed:

[0051] In practical applications, the attraction force F of the excitation coil during steady-state operation is calculated using the following formula:

[0052]

[0053] In the above formula, For the working air gap flux, B The magnetic flux density of the working air gap. Let be the free permeability, and its value is . , S This represents the cross-sectional area of ​​a single magnetic needle.

[0054] According to Ampere's circuital law, the magnetic flux density in the magnetic core... B Satisfy the following formula:

[0055]

[0056] In the above formula, I To the current intensity in the excitation coil, N The number of turns of the excitation coil, The height of the magnetized iron core, denoted as ρ, where ρ is the relative permeability of the iron core.

[0057] Combining the two equations above, we can obtain the magnetic attraction force of a single magnetic needle. for:

[0058]

[0059] In an ideal close-packed configuration, a single magnetic needle can come into contact with a maximum of six other magnetic needles, and the normal force between the needles is... F p , k Let be the coefficient of friction, and its frictional force is calculated using the following formula:

[0060]

[0061] when At that time, that is:

[0062]

[0063] It meets the working condition of the magnetic needle bundle closely fitting the curved surface.

[0064] Of course, it should be noted that the above analysis is only a theoretical analysis. In practical applications, when the eddy current testing probe contacts the object under test in different spatial postures (such as overhead, overhead, and horizontal), the influence of the gravity of the eddy current testing probe and the pressure applied to the probe on the above force analysis process should also be considered. However, regardless of the application scenario, increasing the intensity of the DC signal input to the excitation coil from the external power supply can improve performance. I To enhance magnetic adsorption, it is always possible to eventually overcome the friction between the magnetic needles and switch each magnetic needle from a flat-end shape to a shape that matches the surface of the object being measured.

[0065] In the actual implementation of this embodiment, the shape of the magnetic needles can be optimized to facilitate relative sliding of the needles within the magnetic core bundle. For example, linear, uniform, straight cylindrical magnetic needles can be selected to avoid axial resistance caused by bending or changes in wire diameter. The surface of the magnetic needles can be mirror-finished to make them sufficiently smooth, thereby reducing the coefficient of friction. Cylindrical magnetic needles can be chosen instead of prismatic needles to reduce the contact area between adjacent needles, and so on.

[0066] The following are provided in this embodiment: Figure 1 In the simplified scheme of the curved adaptive eddy current detection probe shown, the excitation coil and induction coil tightly wound around the outside of the magnetic core bundle can act as limiting components with radial limiting function; however, the coils do not have an axial limiting effect on the individual magnetic needles in the magnetic core bundle. In practical applications, to prevent the magnetic needles from exceeding the axial displacement limit and causing them to detach from the coils, ultimately leading to the disintegration of the magnetic core bundle, this embodiment can further add a limiting component to the eddy current detection probe. This limiting component should have two switchable operating states, including a free state that allows the magnetic needles to slide relative to each other, and a limiting state that fixes the relative positions of the magnetic needles.

[0067] In the free state, each magnetic needle in the core bundle can adaptively slide flexibly along the axial direction according to the object being measured, thus closely conforming to various curved surface structures with different morphologies. This results in the detection surface of the entire core bundle forming a lattice state that matches the surface morphology of the measured structure. In the constrained state, the constraining element can apply a force to the entire core bundle, preventing relative movement of the individual magnetic needles. This ensures that the core bundle effectively maintains a close fit with the object being measured during the measurement process, and also prevents the core bundle from disintegrating in non-measurement states.

[0068] In practical applications, such as Figure 4 As shown, the limiting element can be an adjustable sleeve; the sleeve is made of non-ferromagnetic material and is fitted over the limiting element. The sleeve is loosened before testing to allow relative sliding of the magnetic needles; and tightened after testing to fix the relative position of each magnetic needle.

[0069] In another feasible solution, the limiting element can also be a mounting base made of flexible material. For example... Figure 5 As shown, the mounting base is honeycomb-shaped, containing multiple through holes, the diameter of which matches the outer diameter of the magnetic needle. The magnetic needle is inserted into the through hole. When using this type of limiting component, the mounting base fixes the relative position of each magnetic needle after compressive deformation, and allows relative sliding of each magnetic needle when the mounting base recovers its deformation. In practical applications, the magnetic needle can be tightly connected to the mounting base in the initial state (meaning there is no gap between them in the free state, preventing relative sliding), and then the magnetic force can be used to "pull" the magnetic needle out of the mounting base to achieve a shape change and close contact with the object being measured. Alternatively, the magnetic needle can be loosely inserted into the mounting base in the initial state (meaning there is a small gap in the free state, allowing relative sliding), and then fasteners can be used to apply compressive stress to the mounting base when necessary, causing the mounting base to deform and "clamp" the magnetic needles.

[0070] In other designs, the limiting element may also include an end cap and an elastic membrane fixed inside it; the end cap is fitted onto the end of the magnetic core bundle; and the end of each magnetic needle furthest from the detection surface is bonded to the elastic membrane. The elastic membrane serves two purposes: firstly, it limits the axial sliding range of each magnetic needle; secondly, it deforms as each magnetic needle slides, thereby restoring the magnetic needles to their original position through the deformation recovery of the elastic membrane.

[0071] As described above, the curved adaptive eddy current detection probe provided in this embodiment requires, in practical operation, both the generation of a stable magnetic field using the current input to the excitation coil to achieve magnetic attraction, and the generation of an alternating magnetic field using the current input to the excitation coil to complete eddy current detection. To achieve these objectives, in practical applications, the current signal input to the excitation coil by the adjustable power supply can adopt the following two modes:

[0072] Mode 1:

[0073] Before detection, a preset current intensity DC signal is output to achieve adsorption. If necessary, after the eddy current detection probe has achieved adsorption and deformation, a limiting component can be used to lock its shape, and external pressure can be used to keep the probe in contact with the object being detected. Then, during detection, only an alternating signal used to generate a preset detection magnetic field is output.

[0074] Mode 2:

[0075] The adjustable power supply can also output a current signal containing both AC and DC components, so that the magnetic needle is magnetized and attracted to the surface of the object being measured, generating a preset detection magnetic field in the target area of ​​the object. That is, the current signal input to the excitation coil must both maintain the attraction force and induce eddy currents in the target area of ​​the object being measured.

[0076] Of the two operating modes, the former is relatively more cumbersome to operate, but the equipment consumes less power and is not affected by the adsorption magnetic field during inspection, making signal processing easier. The latter is simpler to operate and has higher detection efficiency, but it suffers from relatively higher power consumption and requires more complex processing of the detection signal. In particular, the latter can automatically switch the end-face morphology of the magnetic core bundle during measurement and effectively maintain the optimal shape; therefore, it can be applied to continuous measurement of non-uniform surfaces, which is the most prominent feature of this solution. In practical applications, technicians can flexibly choose different operating modes according to the specific application scenario.

[0077] Example 2

[0078] Based on the scheme in Example 1, this embodiment further provides a non-destructive testing instrument, such as... Figure 7As shown, it includes: an eddy current detection probe, an adjustable power supply, a signal receiver, and a data processing module. The eddy current detection probe is the surface-adaptive eddy current detection probe of Embodiment 1. The adjustable power supply is electrically connected to the excitation coil of the eddy current detection probe and is used to output a dynamically adjustable current signal. The current signal output by the adjustable power supply can magnetize the magnetic core bundle, causing the detection surface of the eddy current detection probe to be tightly attracted to the target area of ​​the object being measured; and generating an alternating magnetic field for detection in the target area.

[0079] The signal receiver is electrically connected to the induction coil and senses the signal generated by the object under test during the detection process. In practical applications, the signal receiver includes a conditioning circuit and a sampling circuit; the conditioning circuit filters and amplifies the acquired signal; the sampling circuit performs A / D conversion sampling on the coil's output. The data processing module acquires the signal received by the signal receiver, performs signal analysis and analog-to-digital conversion, and then generates the required detection results.

[0080] In a further optimized embodiment, the non-destructive testing instrument also includes a display component. The display component is electrically connected to the data processing module and is used to visualize the detection results, so that users can intuitively observe the defect types and defect distribution status of different areas of the tested object.

[0081] Specifically, in conjunction with the description of the structure and function of the eddy current testing probe in Example 1, this example further discusses a method for completing a testing task using the aforementioned non-destructive testing instrument, namely, a testing method for complex curved surface structures. Accordingly, this testing method includes two modes:

[0082] The first mode is:

[0083] Before starting the test, switch the limiting device of the eddy current detection probe to the free state; output a current signal containing both AC and DC components through the adjustable power supply, so that the detection surface of the magnetic core bundle is magnetically attracted to the object under test and adaptively deforms. After the test is completed in the magnetic attraction state, turn off the adjustable power supply; finally, after each magnetic needle in the magnetic core bundle is reset, switch the limiting device back to the limiting state.

[0084] The second mode is:

[0085] Before starting the test, switch the limiting device of the eddy current detection probe to the free state. Output a DC signal through the adjustable power supply to magnetically attract the detection surface of the magnetic core bundle to the object under test and allow it to adapt to deformation. Then switch the limiting device to the limiting state to maintain the current shape of the magnetic core bundle. Next, switch the output of the adjustable power supply to an alternating signal to complete the test. Then, turn off the adjustable power supply and switch the limiting device to the free state to reset each magnetic needle in the magnetic core bundle. Finally, switch the limiting device to the limiting state.

[0086] Example 3

[0087] Based on the scheme of Example 1, this embodiment further provides a paint film thickness measuring instrument, which adopts the surface adaptive eddy current detection probe as in Example 1.

[0088] Existing paint film thickness gauges primarily utilize the aforementioned lift-off effect to measure the paint film thickness on metal surfaces. Their working principle involves treating the paint film as a non-magnetic medium between the object being measured (the metal component to which the paint film adheres) and the eddy current probe. When the eddy current probe is used for detection, a change in the paint film thickness indicates a change in the lift-off distance between the probe and the object being measured, which in turn causes a change in the detection signal output by the induction coil. Traditional paint film thickness gauges utilize this principle to measure paint film thickness.

[0089] However, when traditional paint film thickness gauges are applied to measure paint films on non-uniform surfaces, the probe's core cannot make close contact with the surface being measured. Therefore, the lift-off distance between the probe and the object being measured is affected not only by the paint film thickness but also by the unevenness of the paint film surface, leading to a decrease in the accuracy of the final measurement result. The paint film thickness gauge using a surface-adaptive eddy current detection probe provided in this embodiment completely overcomes this defect, achieving high-precision measurement of paint film thickness on both uniform and non-uniform surfaces.

[0090] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A surface-adaptive eddy current detection probe, characterized in that, It includes: a magnetic core bundle, an excitation coil, and an induction coil; the magnetic core bundle is composed of multiple smooth magnetic needles made of ferromagnetic material arranged closely together in parallel; the excitation coil and the induction coil are wound on the magnetic core bundle to limit the magnetic needles into a bundle radially and allow the magnetic needles to slide relative to each other axially; the excitation coil is used to connect to an adjustable power supply; the excitation coil uses the adjustable power supply to generate an alternating magnetic field for detection in the target area and magnetizes the magnetic core bundle so that the detection surface of the eddy current detection probe is tightly attracted to the target area on the surface of the object being measured; the induction coil is used to sense and output the signal generated by the object being measured during the detection process.

2. The surface-adaptive eddy current detection probe according to claim 1, characterized in that: The adjustable power supply outputs a preset current intensity DC current before detection to achieve magnetic adsorption; and outputs an alternating signal to generate a preset detection magnetic field during detection. Alternatively, the adjustable power supply outputs a current signal that simultaneously contains both AC and DC components throughout the entire process, so that the magnetic needle is magnetized and attracted to the object under test, generating a preset detection magnetic field in the target area of ​​the object under test.

3. The surface-adaptive eddy current detection probe according to claim 1, characterized in that: The excitation coil is wound around the end of the magnetic core bundle away from the detection surface; the induction coil is wound around the end of the magnetic core bundle closer to the detection surface.

4. The surface-adaptive eddy current detection probe according to claim 3, characterized in that: The magnetic needle is made of ferrite, permalloy or silicon steel. and / or The magnetic needle is a cylindrical magnetic needle.

5. The surface-adaptive eddy current detection probe according to claim 2, characterized in that: It also includes a limiting member with two switchable working states, including a free state that allows the magnetic needles to slide relative to each other, and a limiting state that fixes the relative position of the magnetic needles.

6. The surface-adaptive eddy current detection probe according to claim 5, characterized in that: The limiting component includes a retractable sleeve; the sleeve is made of a non-ferromagnetic material and is fitted over the magnetic core bundle. And / or, the limiting member includes a mounting base made of a non-ferromagnetic flexible material, the mounting base being honeycomb-shaped and containing a plurality of through holes, the diameter of the through holes matching the outer diameter of the magnetic needles; each magnetic needle is inserted into the through hole; And / or, the limiting member includes an end cap and an elastic film fixed inside it; the end cap is sleeved on the end of the magnetic core bundle; the end of each magnetic needle away from the detection surface is bonded to the elastic film.

7. A non-destructive testing instrument, characterized in that, It includes: The surface-adaptive eddy current detection probe as described in claim 5 or 6; An adjustable power supply is electrically connected to the excitation coil of the eddy current detection probe and is used to output a dynamically adjustable current signal. The current signal is used to magnetize the magnetic core bundle so that the detection surface of the eddy current detection probe is tightly attracted to the target area of ​​the object being measured; and to generate an alternating magnetic field for detection in the target area. A signal receiver, which is electrically connected to the induction coil, senses the signal generated by the object under test during the detection process; The data processing module is used to acquire the signal received by the signal receiver, perform signal analysis and analog-to-digital conversion on it, and then generate the required detection results.

8. The non-destructive testing instrument according to claim 7, characterized in that: The signal receiver includes a conditioning circuit and a sampling circuit; the conditioning circuit is used to filter and amplify the acquired signal; the sampling circuit is used to sample the output of the induction coil through A / D conversion. and / or The non-destructive testing instrument also includes a display component, which is electrically connected to the data processing module and is used to visualize the detection results.

9. A flaw detection method for complex curved surface structures, characterized in that: It employs the non-destructive testing instrument as described in claim 7 or 8, which includes: Before the test begins, the limiting device of the eddy current test probe is switched to the free state. The current signal containing both AC and DC components is output through the adjustable power supply. The detection surface of the magnetic core bundle is magnetically attracted to the object under test and adapts to deformation. After the test is completed in the magnetic attraction state, the adjustable power supply is turned off. Finally, after each magnetic needle in the magnetic core bundle is reset, the limiting device is switched back to the limiting state. Alternatively, before starting the test, switch the limiting device of the eddy current detection probe to the free state, output a DC signal through the adjustable power supply to make the detection surface of the magnetic core bundle magnetically attract the object under test and adapt to deformation; then switch the limiting device to the limiting state to maintain the current shape of the magnetic core bundle; then switch the output of the adjustable power supply to an alternating signal to complete the test; then turn off the adjustable power supply and switch the limiting device to the free state to reset each magnetic needle in the magnetic core bundle; finally switch the limiting device to the limiting state.

10. A paint film thickness measuring instrument, characterized in that, It employs a surface-adaptive eddy current detection probe as described in any one of claims 1-6.

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