A method and device for acquiring equivalent frequency and skin depth of eddy current detection
By establishing the theoretical relationship between probe velocity and equivalent frequency and introducing a magnetic Reynolds number transition point correction term, the problem of unclear equivalent frequency and skin depth in motional eddy current detection is solved, achieving high-precision skin depth acquisition and expanding the applicability of motional eddy current detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TSINGHUA UNIVERSITY
- Filing Date
- 2026-01-07
- Publication Date
- 2026-06-02
AI Technical Summary
In existing motional eddy current testing, the theoretical relationship between the equivalent frequency and the skin depth is unclear, which makes it impossible to accurately estimate material parameters and limits its application under high-speed testing conditions.
A theoretical model for motional eddy current detection is established, the mapping relationship between probe velocity and equivalent frequency is derived, a correction term for the magnetic Reynolds number transition point is introduced, and the skin depth is calculated by adjusting the equivalent frequency information to improve the acquisition accuracy in the low-speed range.
It achieves high-precision acquisition of skin depth in dynamic eddy current testing, supports parameter inversion of conductive materials under high-speed conditions, and is suitable for non-destructive testing in the rapid production process of thin plate materials.
Smart Images
Figure CN122132660A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of motional eddy current detection technology, and in particular to a method and apparatus for obtaining the equivalent frequency and skin depth of motional eddy current detection. Background Technology
[0002] Eddy current testing, as an important technique in the field of nondestructive testing, is widely used in industrial scenarios such as aerospace and rail transportation. With the continuous increase in material processing speed, the limitations of traditional eddy current testing, which relies on fixed-frequency excitation, are becoming increasingly apparent. Especially under high-speed motion conditions of 2-50 m / s, the dynamic matching requirement between the excitation frequency and the sample velocity significantly exacerbates the skin effect. Among related technologies, motional eddy current testing has been proposed. It utilizes the relative motion between a static magnetic field and a conductive sample to generate eddy currents, making it suitable for high-speed testing.
[0003] However, existing research on motional eddy current testing mainly focuses on defect detection, and the theoretical relationship between the equivalent frequency generated by the testing method and the skin depth is not yet clear, leading to an inability to accurately estimate material parameters. Traditional eddy current testing relies on frequency scanning to decouple parameters, but the equivalent relationship between velocity and frequency in motional eddy current testing lacks a systematic model, limiting its industrial applications. Therefore, it is necessary to develop a skin depth acquisition method based on equivalent frequency to expand the applicability of motional eddy current testing. Summary of the Invention
[0004] The present invention aims to at least partially solve one of the technical problems in the related art.
[0005] Therefore, the first objective of this invention is to provide a method for obtaining the equivalent frequency and skin depth of motional eddy current detection.
[0006] Another objective of this invention is to provide a device for obtaining the equivalent frequency and skin depth of motional eddy current detection.
[0007] The third objective of this invention is to provide a computer device.
[0008] A fourth objective of this invention is to provide a non-transitory computer-readable storage medium.
[0009] To achieve the above objectives, a first aspect of the present invention provides a method for obtaining the equivalent frequency and skin depth of motional eddy current detection, comprising: S1. Establish a theoretical model for motional eddy current detection to describe the eddy current distribution and spatial characteristics of the magnetic field when a conductive sample moves in a static magnetic field. S2, Based on the theoretical model, determine the mapping relationship between probe speed and equivalent frequency, so as to convert the motion speed parameter into equivalent frequency information; S3, calculate the basic skin depth based on the equivalent frequency information; S4, introduce a velocity-dependent correction term based on the magnetic Reynolds number transition point, and update the low-speed segment error of the basic skin depth by adjusting the equivalent frequency information calculation formula.
[0010] In one embodiment of the present invention, the step of deriving the mapping relationship between probe velocity and equivalent frequency based on the theoretical model, and converting the motion velocity parameter into equivalent frequency domain information, includes: The effective length of the magnetic field is the distance between two main peaks in the static magnetic field spatial distribution, and the distance between the main peaks is determined by the point of maximum magnetic field intensity gradient.
[0011] In one embodiment of the present invention, the formula for calculating the basic skin depth based on the equivalent frequency is as follows: , where μ is the magnetic permeability and σ is the electrical conductivity.
[0012] In one embodiment of the present invention, the step of introducing a velocity-dependent correction term based on the magnetic Reynolds number transition point and correcting the low-velocity error of the skin depth by adjusting the equivalent frequency calculation formula includes: The corrected skin depth formula is Where v0 is the transition velocity; the transition velocity v0 is determined by the magnetic Reynolds number. Get, when R m When approximately 1 hour, L R The characteristic length is denoted as .
[0013] In one embodiment of the present invention, it further includes: The expression for the magnetic field is:
[0014] Where a is the half-width of the permanent magnet in the direction of sample movement, h is the height of the permanent magnet, y0 is the lift-off distance, and I is the magnetization intensity of the permanent magnet.
[0015] In one embodiment of the present invention, it further includes: The formula for the equivalent frequency feq is: , where v is the probe velocity and Leff is the effective length of the magnetic field.
[0016] The present invention discloses a method and apparatus for obtaining the equivalent frequency and skin depth in motional eddy current detection. By establishing a theoretical relationship between probe velocity and equivalent frequency and introducing a velocity-dependent correction term, the method and apparatus achieve high-precision acquisition of skin depth in motional eddy current detection, effectively supporting parameter inversion of conductive materials under high-speed conditions.
[0017] To achieve the above objectives, a third aspect of this application provides a computer device comprising a processor and a memory; wherein the processor reads executable program code stored in the memory to run a program corresponding to the executable program code, for implementing a method for obtaining the equivalent frequency and skin depth of motional eddy current detection as described in the first aspect embodiment.
[0018] To achieve the above objectives, a fourth aspect of this application provides a non-transitory computer-readable storage medium storing a computer program that, when executed by a processor, implements a method for obtaining the equivalent frequency and skin depth of motional eddy current detection as described in the first aspect embodiment.
[0019] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0020] Figure 1 This is a flowchart of a method for obtaining the equivalent frequency and skin depth of motional eddy current detection according to an embodiment of the present invention; Figure 2 This is a schematic diagram of numerical simulation results for detecting skin depth using motional eddy currents at different speeds according to an embodiment of the present invention; Figure 3 This is a comparison diagram of the equivalent frequency model and numerical simulation results at different speeds according to embodiments of the present invention; Figure 4 This is a structural diagram of an apparatus for obtaining the equivalent frequency and skin depth of motional eddy current detection according to an embodiment of the present invention; Figure 5 It is a computer device according to an embodiment of the present invention. Detailed Implementation
[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.
[0023] The following description, with reference to the accompanying drawings, describes a method and apparatus for obtaining the equivalent frequency and skin depth of motional eddy current detection according to an embodiment of the present invention.
[0024] Figure 1 This is a flowchart of a method for obtaining the equivalent frequency and skin depth of motional eddy current detection according to an embodiment of the present invention, as shown below. Figure 1 As shown, it includes: S1. Establish a theoretical model for motional eddy current detection to describe the eddy current distribution and spatial characteristics of the magnetic field when a conductive sample moves in a static magnetic field. S2, Based on the theoretical model, determine the mapping relationship between probe speed and equivalent frequency, so as to convert the motion speed parameter into equivalent frequency information; S3, calculate the basic skin depth based on the equivalent frequency information; S4, introduce a velocity-dependent correction term based on the magnetic Reynolds number transition point, and update the low-speed segment error of the basic skin depth by adjusting the equivalent frequency information calculation formula.
[0025] Step 1: Establish a theoretical model for motional eddy current detection, describing the eddy current distribution and magnetic field expression when a conductive sample moves in a static magnetic field; In step 1, the theoretical model adopts a two-dimensional analytical model, and the eddy current density distribution is solved by spatial Fourier transform. The magnetic field expression is:
[0026] Among them, the half-width a of the permanent magnet in the direction of sample movement is 0.5 mm, the height h of the permanent magnet is 1 mm, the lift-off distance y0 is 5 mm, and the magnetization intensity I of the permanent magnet is 6e5 A / m.
[0027] Further, in step 2, based on the theoretical model, the relationship between probe velocity and equivalent frequency is derived, wherein the equivalent frequency... f eq The formula is Where v is the probe velocity, L eff The effective length of the magnetic field; In step 2, the effective length of the magnetic field L eff Defined as the distance between two main peaks in the spatial distribution of the static magnetic field, which is 12.5 mm.
[0028] Further, in step 3, the skin depth is obtained based on the equivalent frequency, using the following formula: , where μ is the magnetic permeability and σ is the electrical conductivity; Further, in step 4, a velocity-dependent correction term is introduced, which is based on the magnetic Reynolds number transition point. The corrected skin depth formula is as follows: , where v0 is the transition velocity.
[0029] In step 4, the transition velocity v0 is determined by the magnetic Reynolds number. Get, when R m When approximately 1 hour, , where the feature length L R The value is 6.25 mm, and the transition velocity v0 is 3 m / s.
[0030] Furthermore, the verification experiment used conductive samples with a velocity range of 2-50 m / s, and the numerical simulation results are as follows. Figure 2 As shown, the comparison of skin depth at various velocities obtained from numerical simulation and equivalent frequency models is as follows: Figure 3 As shown, the maximum error does not exceed 5%.
[0031] This invention proposes a method for obtaining equivalent frequency and skin depth based on motional eddy current detection. By using an equivalent frequency model, the velocity parameters of motional eddy current detection are transformed into frequency domain information, simplifying the acquisition of skin depth. The correction term considers the magnetic Reynolds number transition point, improving the acquisition accuracy under low-speed conditions. The method is applicable to high-speed environments, providing theoretical support for online detection. It is suitable for rapid production processes of thin sheet materials and can be widely applied in the field of non-destructive testing of defects in thin sheet materials.
[0032] To achieve the above embodiments, such as Figure 4 As shown, this embodiment also provides an equivalent frequency and skin depth acquisition device 10 for motional eddy current detection, including: The theoretical model building module 100 is used to build a theoretical model for motional eddy current detection, describing the eddy current distribution and spatial characteristics of the magnetic field when a conductive sample moves in a static magnetic field. The equivalent frequency mapping module 200 is used to derive the mapping relationship between probe speed and equivalent frequency based on the theoretical model, and to convert motion speed parameters into equivalent frequency domain information. The skin depth calculation module 300 is used to calculate the basic skin depth based on the equivalent frequency and establish a correlation model between velocity and material parameters. The velocity-dependent correction module 400 is used to introduce a velocity-dependent correction term based on the magnetic Reynolds number transition point, and correct the low-speed segment error of the skin depth by adjusting the equivalent frequency calculation formula.
[0033] The present invention discloses a method and apparatus for obtaining the equivalent frequency and skin depth in motional eddy current detection. By establishing a theoretical relationship between probe velocity and equivalent frequency and introducing a velocity-dependent correction term, the method and apparatus achieve high-precision acquisition of skin depth in motional eddy current detection, effectively supporting parameter inversion of conductive materials under high-speed conditions.
[0034] To implement the methods of the above embodiments, the present invention also provides a computer device, such as...Figure 5 As shown, the computer device 600 includes a memory 601 and a processor 602; wherein, the processor 602 reads the executable program code stored in the memory 601 to run a program corresponding to the executable program code, so as to implement the various steps of the above-described method for obtaining the equivalent frequency and skin depth of motional eddy current detection.
[0035] To implement the above embodiments, this application also proposes a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements a method for obtaining the equivalent frequency and skin depth of motional eddy current detection as described in the foregoing embodiments.
[0036] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.
[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
Claims
1. A method for obtaining the equivalent frequency and skin depth of motional eddy current detection, characterized in that, include: S1. Establish a theoretical model for motional eddy current detection to describe the eddy current distribution and spatial characteristics of the magnetic field when a conductive sample moves in a static magnetic field. S2, Based on the theoretical model, determine the mapping relationship between probe speed and equivalent frequency, so as to convert the motion speed parameter into equivalent frequency information; S3, calculate the basic skin depth based on the equivalent frequency information; S4, introduce a velocity-dependent correction term based on the magnetic Reynolds number transition point, and update the low-speed segment error of the basic skin depth by adjusting the equivalent frequency information calculation formula.
2. The method as described in claim 1, characterized in that, The theoretical model adopts a two-dimensional analytical model, and the eddy current density distribution is solved by spatial Fourier transform.
3. The method as described in claim 2, characterized in that, The process of deriving the mapping relationship between probe velocity and equivalent frequency based on the theoretical model, and converting the motion velocity parameters into equivalent frequency domain information, includes: The effective length of the magnetic field is the distance between two main peaks in the static magnetic field spatial distribution, and the distance between the main peaks is determined by the point of maximum magnetic field intensity gradient.
4. The method as described in claim 1, characterized in that, The basic skin depth is calculated based on the equivalent frequency, using the following formula: , where μ is the magnetic permeability and σ is the electrical conductivity.
5. The method as described in claim 1, characterized in that, The introduction of a velocity-dependent correction term based on the magnetic Reynolds number transition point, and the correction of the low-velocity error of the skin depth by adjusting the equivalent frequency calculation formula, includes: The corrected skin depth formula is Where v0 is the transition velocity; the transition velocity v0 is determined by the magnetic Reynolds number. Get, when R m When approximately 1 hour, L R The characteristic length is denoted as .
6. The method as described in claim 2, characterized in that, Also includes: The expression for the magnetic field is: Where a is the half-width of the permanent magnet in the direction of sample movement, h is the height of the permanent magnet, y0 is the lift-off distance, and I is the magnetization intensity of the permanent magnet.
7. The method as described in claim 3, characterized in that, Also includes: The formula for the equivalent frequency feq is: , where v is the probe velocity and Leff is the effective length of the magnetic field.
8. A device for obtaining the equivalent frequency and skin depth of motional eddy current detection, characterized in that, include: The theoretical model building module is used to build a theoretical model for motional eddy current detection, describing the eddy current distribution and spatial characteristics of the magnetic field when a conductive sample moves in a static magnetic field. The equivalent frequency mapping module is used to derive the mapping relationship between probe speed and equivalent frequency based on the theoretical model, and to convert motion speed parameters into equivalent frequency domain information. The skin depth calculation module is used to calculate the basic skin depth based on the equivalent frequency and establish a correlation model between velocity and material parameters. The velocity-dependent correction module is used to introduce a velocity-dependent correction term based on the magnetic Reynolds number transition point, and corrects the low-velocity error of the skin depth by adjusting the equivalent frequency calculation formula.
9. A computer device, characterized in that, Including processor and memory; The processor reads executable program code stored in the memory to run a program corresponding to the executable program code, so as to implement the method for obtaining the equivalent frequency and skin depth of motional eddy current detection as described in any one of claims 1-7.
10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the processor, the program implements a method for obtaining the equivalent frequency and skin depth of motional eddy current detection as described in any one of claims 1-7.