A method for measuring pipeline conductivity and inner diameter based on swept frequency eddy current

Abstract

This application proposes a method for measuring pipeline conductivity and inner diameter based on swept-frequency eddy currents. The method includes: constructing an eddy current detection device, designing an absolute eddy current detection coil, placing the coil inside a metal pipe and coaxially arranged with the pipe, passing an alternating current to excite an alternating magnetic field, and inducing eddy currents on and near the pipe surface; establishing an analytical theoretical model for eddy currents in metal pipes, setting the coil's geometric parameters, and calculating an analytical expression for how the coil's impedance changes with the excitation frequency; calculating the peak frequency and corresponding phase value of the coil's impedance phase in a swept-frequency mode, varying the pipe's conductivity and inner diameter, extracting the corresponding peak frequency and phase value, and constructing an inner diameter relationship model based on quadratic curve fitting and a conductivity relationship model based on power function fitting; and combining the coil impedance swept-frequency phase measurement results to invert the inner diameter and conductivity of the metal pipe. This method can simultaneously measure the pipe's conductivity and inner diameter, making it suitable for nondestructive testing and performance evaluation of metal pipes.

Description

Technical Field

[0001] The present application relates to the field of electromagnetic eddy current detection, and in particular to a method for measuring the electrical conductivity and inner diameter of a pipeline based on swept-frequency eddy current. Background Art

[0002] Metal pipelines are widely used in the petrochemical industry, natural gas transportation, water conservancy projects, power transmission, and other fields due to their excellent mechanical strength, electrical conductivity, and corrosion resistance. However, metal pipelines are often subject to a variety of complex loads during their service. Especially under long-term service conditions, the pipeline structure can be damaged by factors such as fatigue and stress corrosion, and may even crack or fail. The accumulation of such damage not only affects the mechanical properties of the pipeline but also threatens the safety of the entire system. Therefore, in-service damage detection and performance evaluation of metal pipelines are important engineering requirements to ensure their safe operation.

[0003] The electromagnetic properties of metal pipelines are closely related to their microstructure, chemical composition, and mechanical properties. During service, the microstructure and defects of pipelines cause changes in electromagnetic parameters such as conductivity. By measuring these electromagnetic parameters, internal damage states, such as fatigue, cracks, and corrosion, can be indirectly assessed, enabling nondestructive testing and condition monitoring. Based on this principle, electromagnetic technology has gradually become a key research direction in the field of nondestructive testing.

[0004] Eddy current testing technology is a non-destructive testing method based on the principle of electromagnetic induction. It evaluates the electrical conductivity, conductivity and related properties of metals by detecting the distribution and changes of induced eddy currents in the metal being tested. Eddy current testing has the advantages of high sensitivity, non-contact measurement, and fast detection speed. It is particularly suitable for defect detection, corrosion assessment and electromagnetic property measurement of metal materials. At the same time, because eddy current testing relies on the skin effect, it can achieve deep detection of metals of different thicknesses, so it has a wide range of applications in engineering. However, the application of traditional eddy current testing in the measurement of electrical conductivity of metal pipelines still faces some technical difficulties. For example, under complex working conditions, the detection accuracy is low, the decoupling ability of multiple parameters is insufficient, and the real-time performance is poor, which limits its application in the in-service status monitoring of metal pipelines. Summary of the Invention

[0005] The present application aims to solve one of the technical problems in the related art at least to a certain extent.

[0006] To this end, the first object of this application is to propose a method for measuring pipeline conductivity and inner diameter based on swept-frequency eddy current.

[0007] The second object of the present application is to provide a device for measuring the electrical conductivity and inner diameter of a pipeline based on swept-frequency eddy current.

[0008] The third objective of this application is to provide an electronic device.

[0009] The fourth object of this application is to provide a computer-readable storage medium.

[0010] A fifth object of this application is to provide a computer program product.

[0011] To achieve the above objectives, the first embodiment of the present application proposes a method for measuring pipeline conductivity and inner diameter based on swept-frequency eddy current, comprising:

[0012] S1. Build an eddy current detection device and design an absolute eddy current detection coil. Place the coil inside a metal pipe and arrange it coaxially with the pipe. Apply an alternating current to the coil to excite an alternating magnetic field, inducing eddy currents on and near the pipe surface.

[0013] S2. Establish a theoretical analytical model for eddy current in metal pipes, set the geometric parameters of the coil, and calculate the analytical expression of the change of coil impedance with excitation frequency;

[0014] S3. Based on the theoretical model of metal pipe eddy current analysis, calculate the change of the impedance phase of the coil with the excitation frequency in the sweep frequency mode, and extract the peak frequency and corresponding phase value of the impedance phase;

[0015] S4. Changing the conductivity of the metal pipe, repeatedly performing step S3 until the number of times the pipe conductivity is set reaches the required number, and obtaining the peak frequency and corresponding phase value of the eddy current sweep phase under different conductivities;

[0016] S5. Change the inner diameter of the metal pipe, jump back to step S3 and execute again until the number of times the pipe inner diameter is set reaches the required number, and obtain the peak frequency and corresponding phase value of the eddy current sweep frequency phase under different inner diameters;

[0017] S6. Based on the phase peak frequency and phase value under different inner diameters, a quadratic curve is used to fit the relationship between the peak frequency phase value and the inner diameter of the pipe;

[0018] S7. In a double logarithmic coordinate system, based on the peak frequency at different conductivities, a linear fit is used to calculate the relationship between the peak frequency and the inner diameter of the pipe, the linear fit intercept is extracted, and a power function is used to fit the relationship between the intercept and the conductivity;

[0019] S8. Using the fitted quadratic function and power function models, combined with the coil impedance sweep phase change measurement results, the inner diameter and conductivity of the pipeline are simultaneously inverted.

[0020] Optionally, the geometric parameters of the coil include: the number of turns N of the coil, the inner diameter r1 and outer diameter r2 of the coil, and the height l2-l1 of the coil.

[0021] Optionally, the analytical expression for the change of the coil impedance with the excitation frequency is:

[0022]

[0023] Where:

[0024]

[0025] Wherein, ΔZ is the change of coil impedance, ω is the excitation angular frequency, a is the inner radius of the metal pipe, σ is the conductivity of the metal pipe, μ0 is the magnetic constant, α is the integral variable related to the wave number, I(r2, r1) is the integral function used to describe the coil current distribution, S(α) is the influence coefficient of the impedance change, α1 is the complex wave number, I0 and I1 are the 0th and 1st order first-order modified Bessel functions, respectively, and K0 and K1 are the 0th and 1st order second-order modified Bessel functions, respectively.

[0026] Optionally, the calculation of the impedance phase of the coil as a function of the excitation frequency in a sweep frequency mode based on the metal pipe eddy current analytical theoretical model, and the extraction of the peak frequency and corresponding phase value of the impedance phase, include:

[0027] Set the sweep excitation frequency range to 10 Hz to 1 MHz and calculate the coil impedance phase θ(ω) at different excitation frequencies.

[0028] At the minimum value, the polynomial f(ω) is used to fit the curve near the peak frequency, and the first-order derivative of the fitting polynomial is set to zero to obtain the peak frequency and the corresponding phase value.

[0029] Optionally, the method of fitting the relationship between the peak frequency phase value and the inner diameter of the pipeline using a quadratic curve based on the phase peak frequency and phase value under different inner diameters includes:

[0030] The metal pipe eddy current analytical theoretical model is used to calculate the coil impedance phase sweep signal θ caused by pipes with different inner diameters. n (ω), extract the phase θ corresponding to the peak frequency n (ω peak ), and a quadratic curve was used to fit the relationship between the peak frequency phase value and the inner diameter;

[0031] By changing the conductivity of the metal pipe, the eddy current analytical theoretical model of the metal pipe is still used to calculate the coil impedance phase sweep signal θ caused by pipes with different inner diameters. n (ω), extract the phase θ corresponding to the peak frequency n (ω peak ), and a quadratic curve was used to fit the relationship between the peak frequency phase value and the inner diameter;

[0032] Verification: Phase θ n(ω peak ) will not change with the change of conductivity σ, and the quadratic function fitting relationship adopted will not change with the change of conductivity.

[0033] Optionally, in a double logarithmic coordinate system, based on the peak frequency at different conductivities, a linear fit is used to find the relationship between the peak frequency and the inner diameter of the pipe, a linear fit intercept is extracted, and a power function is used to find the relationship between the intercept and the conductivity, including:

[0034] The metal pipe eddy current analytical theoretical model is used to calculate the coil impedance phase sweep signal θ caused by pipes with different conductivity. m (ω), extract the phase θ corresponding to the peak frequency m (ω peak ), and in the double logarithmic coordinate system, a linear fitting is used to measure the relationship between the peak frequency and the pipeline conductivity;

[0035] By changing the inner diameter of the metal pipe, the eddy current analytical theoretical model of the metal pipe is used to calculate the coil impedance phase sweep signal θ caused by pipes with different conductivity. m (ω), extract the phase θ corresponding to the peak frequency m (ω peak ), and a linear fit was used to determine the relationship between peak frequency and pipeline conductivity in a double logarithmic coordinate system. It was verified that the slope of the fitted line would not change with changes in pipeline conductivity, while the intercept of the fitted line would change with changes in conductivity.

[0036] The intercept of the fitted straight line was extracted, and the power function was used to fit the relationship between the intercept and conductivity.

[0037] To achieve the above-mentioned purpose, the second embodiment of the present application proposes a device for measuring pipeline conductivity and inner diameter based on swept-frequency eddy current, comprising:

[0038] A construction module is provided for constructing an eddy current detection device, designing an absolute eddy current detection coil, placing the coil inside a metal pipe and coaxially arranged with the pipe, passing an alternating current through the coil to excite an alternating magnetic field, and inducing eddy currents on and near the pipe surface;

[0039] The model building module is used to establish the analytical theoretical model of eddy current in metal pipes, set the geometric parameters of the coil, and calculate the analytical expression of the change of coil impedance with excitation frequency;

[0040] A swept-frequency impedance phase calculation module is used to calculate the change of the impedance phase of the coil with the excitation frequency in a swept-frequency mode based on the metal pipe eddy current analytical theoretical model, and to extract the peak frequency and corresponding phase value of the impedance phase;

[0041] The conductivity measurement module is used to change the conductivity of the metal pipe, call the swept frequency impedance phase calculation module, repeatedly calculate until the number of times the pipeline conductivity is set reaches the required number, and obtain the peak frequency and corresponding phase value of the eddy current swept frequency phase under different conductivities;

[0042] An inner diameter measurement module is used to change the inner diameter of the metal pipe, call the swept frequency impedance phase calculation module and the conductivity measurement module, and repeatedly calculate until the number of times the pipe inner diameter is set reaches the required number, thereby obtaining the peak frequency and corresponding phase value of the eddy current swept frequency phase under different inner diameters;

[0043] A quadratic fitting module is used to fit the relationship between the peak frequency phase value and the inner diameter of the pipe using a quadratic curve based on the phase peak frequency and phase value under different inner diameters;

[0044] The double logarithmic linear fitting module is used to use a linear fit to calculate the relationship between the peak frequency and the inner diameter of the pipe based on the peak frequency at different conductivities in a double logarithmic coordinate system, extract the linear fit intercept, and use a power function to fit the relationship between the intercept and the conductivity.

[0045] The parameter inversion module is used to simultaneously invert the inner diameter and conductivity of the pipeline by using the fitted quadratic function and power function models combined with the coil impedance sweep phase change measurement results.

[0046] To achieve the above-mentioned purpose, a third embodiment of the present application provides an electronic device, comprising: a processor, and a memory communicatively connected to the processor;

[0047] The memory stores computer-executable instructions;

[0048] The processor executes the computer-executable instructions stored in the memory to implement the method as described in any one of the first aspects.

[0049] To achieve the above-mentioned purpose, the fourth embodiment of the present application proposes a computer-readable storage medium, which stores computer-executable instructions. When the computer-executable instructions are executed by a processor, they are used to implement the method as described in any one of the first aspects.

[0050] To achieve the above-mentioned objectives, the fifth embodiment of the present application proposes a computer program product, which implements any one of the methods in the first aspect when executed by a processor.

[0051] The technical solutions provided by the embodiments of this application bring at least the following beneficial effects:

[0052] By utilizing swept-frequency eddy current detection technology and combining the characteristics of impedance phase changing with frequency, this application can achieve high-precision measurement of the conductivity and inner diameter of metal pipes, meeting the requirements of industrial detection for accuracy and reliability. Quadratic curve fitting and power function fitting are used to decouple the measurement processes of the pipe inner diameter and conductivity. Independent mathematical models are used to establish the functional relationships between the inner diameter and impedance phase, and between conductivity and frequency, respectively, avoiding mutual interference between parameters and improving measurement accuracy and model applicability.

[0053] In addition, this application uses non-contact eddy current detection technology, which does not damage the metal pipe being tested and can achieve online measurement without dismantling the pipe or interrupting production, meeting the needs of online monitoring and life assessment of pipe performance in industrial scenarios.

[0054] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0056] Figure 1 A schematic flow chart of a method for measuring the electrical conductivity and inner diameter of a pipeline based on swept-frequency eddy currents provided in an embodiment of the present application;

[0057] Figure 2 A schematic diagram of the calculation results of the coil impedance phase under different conductivities provided in an embodiment of the present application;

[0058] Figure 3 A schematic diagram of the coil impedance phase calculation results for different pipe inner diameters provided in an embodiment of the present application;

[0059] Figure 4 A schematic diagram showing the relationship between the peak phase of the frequency sweep and the inner diameter of the pipe provided in an embodiment of the present application;

[0060] Figure 5 A schematic diagram of the relationship between the sweep frequency peak value and the inner diameter of the pipe in the double logarithmic coordinate system provided in the embodiment of the present application;

[0061] Figure 6 A schematic diagram showing the relationship between the intercept of the fitted line and the electrical conductivity of the pipeline provided in an embodiment of the present application;

[0062] Figure 7 A schematic structural diagram of a pipeline conductivity and inner diameter measuring device based on swept-frequency eddy current provided in an embodiment of the present application. DETAILED DESCRIPTION

[0063] The following describes in detail embodiments of the present application, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0064] To address the challenges of existing technologies, this application proposes a method for measuring pipeline conductivity and inner diameter based on swept-frequency eddy currents, combining theoretical modeling, impedance analysis, and mathematical fitting. This method utilizes non-contact, highly sensitive detection techniques to efficiently measure the conductivity and inner diameter of metal pipelines without requiring downtime. By monitoring changes in pipeline conductivity in real time, it can assess pipeline fatigue, defects, and corrosion, providing reliable technical support for in-service pipeline condition monitoring and an important basis for the safe operation and lifespan management of industrial equipment.

[0065] Figure 1 The flow chart of a method for measuring the conductivity and inner diameter of a pipeline based on a swept frequency eddy current is provided in an embodiment of the present application. Figure 1 As shown, the method includes the following steps:

[0066] S1. Build an eddy current detection device and design an absolute eddy current detection coil. Place the coil inside a metal pipe and arrange it coaxially with the pipe. Apply an alternating current to the coil to excite an alternating magnetic field, inducing eddy currents on the pipe surface and near the surface.

[0067] Specifically, the present embodiment designs a cylindrical eddy current sensor comprising an absolute eddy current detection coil. The coil's geometric parameters are precisely designed, with an inner and outer diameter of 2 mm and 5 mm, respectively, and 100 turns, to ensure sufficient sensitivity and detection range for pipeline eddy currents. A sinusoidal alternating current is passed through the coil as an excitation signal, with a frequency range of 10 Hz to 1 MHz. By selecting different excitation frequencies, the distribution range and depth of the eddy currents can be effectively controlled to meet the measurement requirements of different pipeline parameters.

[0068] In this embodiment, copper metal pipes are used as the test object. Their excellent electrical conductivity ensures a significant eddy current induction effect. The change in the coil impedance phase is determined by the intensity and flow range of the eddy currents. This impedance phase measurement provides basic data support for the subsequent extraction of the pipe's conductivity and dimensions. By optimizing the coil's geometric parameters and excitation signal, this embodiment ensures measurement sensitivity and applicability, laying a solid foundation for subsequent steps.

[0069] The eddy current testing device of the present embodiment features a rational design and compact structure, enabling non-contact measurement of the conductivity and inner diameter of tubular components. It is particularly suitable for testing the dimensions and electromagnetic properties of metal pipes, such as copper, aluminum, and stainless steel. This step lays a solid foundation for the subsequent development of an eddy current analytical model and the extraction of precise parameters for pipe conductivity and dimensions, while also ensuring the high versatility and reliability of the testing device.

[0070] S2. Establish a theoretical analytical model of eddy current in metal pipes, set the geometric parameters of the coil, and calculate the analytical expression of the change of coil impedance with excitation frequency.

[0071] In the embodiments of the present application, the geometric parameters of the coil include: the number of turns N, the inner and outer diameters r1 and r2 of the coil, and the height l2-l1 of the coil. Based on these geometric parameters, the embodiments of the present application establish an analytical theoretical model of eddy currents in metal pipes to calculate an analytical expression for how the coil impedance changes with the excitation frequency, thereby revealing the influence of the pipe conductivity and inner diameter on the coil impedance. Specifically, the analytical expression for how the coil impedance changes with the excitation frequency is:

[0072]

[0073] Where:

[0074]

[0075]

[0076] Where ΔZ is the change in coil impedance, ω is the excitation angular frequency, a is the inner radius of the metal pipe, σ is the conductivity of the metal pipe, μ0 is the magnetic constant, α is the integral variable related to the wave number, I(r2,r1) is the integral function used to describe the coil current distribution, S(α) is the influence coefficient of the impedance change, α1 is the complex wave number, I0 and I1 are the 0th and 1st order first-kind modified Bessel functions, respectively, and K0 and K1 are the 0th and 1st order second-kind modified Bessel functions, respectively.

[0077] In one embodiment of this application, the pipe inner diameter a is set to 6 mm, and the excitation frequency range is set to 10 Hz to 1 MHz to cover the detection requirements of different materials and geometries. The analytical model, which comprehensively considers the conductivity and geometric parameters of the pipe material, reveals the distribution of eddy currents and their impact on the coil impedance phase.

[0078] like Figure 2As shown in the figure, by using this analytical model to calculate the variation of the coil impedance phase with the excitation frequency, it is observed that the impedance phase changes significantly at specific frequencies. These specific frequency points are closely related to the conductivity and inner diameter of the pipeline, providing an accurate theoretical basis for subsequent conductivity and inner diameter measurements. The eddy current analytical theoretical model established in this step effectively characterizes the influence of the pipeline's electromagnetic properties and geometric parameters on eddy current behavior, laying the foundation for accurate measurement.

[0079] S3. Based on the analytical theoretical model of eddy current in metal pipes, the impedance phase of the coil is calculated as it changes with the excitation frequency in the sweep frequency mode, and the peak frequency and corresponding phase value of the impedance phase are extracted.

[0080] In this example, a swept frequency excitation range of 10 Hz to 1 MHz was first set. The coil was then progressively excited within this frequency range, and the coil impedance phase θ (ω) was calculated at different excitation frequencies. The curve of the impedance phase versus excitation frequency reflects the influence of the pipeline's conductivity and inner diameter on its electromagnetic properties.

[0081] To extract the peak frequency of the impedance phase and its corresponding phase value, this application uses a polynomial f(ω) to fit the phase curve near the peak frequency near the minimum value at the excitation frequency. By setting the first-order derivative f′(ω) of the fitting polynomial equal to zero, the peak frequency of the phase curve and the corresponding phase value can be accurately obtained. Polynomial fitting can effectively reduce errors caused by measurement noise and frequency resolution limitations, thereby improving calculation accuracy.

[0082] Furthermore, in the embodiment of the present application, in order to more accurately extract the peak frequency and its corresponding phase value, the initial value of the peak frequency is preliminarily determined to be f peak Then, in [(f peak -50)Hz,(f peak A fourth-order polynomial fit was performed on the impedance phase curve within a frequency range of [+50) Hz]. The final peak frequency and corresponding phase value were obtained by calculating the first-order derivative of the fitting polynomial, f′(ω) = 0, and setting it equal to zero.

[0083] The final peak frequency and phase values ​​obtained by the above method can reflect the characteristics of pipeline conductivity and geometric parameters, providing basic data for mathematical fitting and parameter inversion in subsequent steps.

[0084] S4. Change the conductivity of the metal pipe and repeatedly perform step S3 until the number of times the pipe conductivity is set reaches the required number, and obtain the peak frequency and corresponding phase value of the eddy current sweep phase under different conductivities.

[0085] In this example, the conductivity of the metal pipe was adjusted by varying its material, and the impedance phase change of the coil was measured under different conductivity conditions. Specifically, the metal pipe components were made of the following five common materials: copper, aluminum, aluminum alloy, stainless steel, and titanium alloy. The conductivity of these materials was set to 58MS / m, 38MS / m, 20MS / m, 2.32MS / m, and 0.56MS / m, respectively, covering the conductivity range of common metal materials.

[0086] Under each material condition, the sweep frequency method described in step S3 is used to measure the coil impedance phase change curve θ(ω) within the excitation frequency range, and the corresponding peak frequency f is extracted by fitting. peak and phase value θ peak By repeatedly executing the above process, the peak frequency and corresponding phase value data of the eddy current sweep phase under different conductivity conditions are recorded.

[0087] In this embodiment, the changes in coil impedance phase caused by different materials are as follows: Figure 2 As shown. Figure 2 It can be seen that as the conductivity of the pipe material decreases, the peak frequency of the coil impedance phase gradually shifts toward lower frequencies, and the corresponding phase value also changes significantly. Specifically, for five different materials: copper (58MS / m), aluminum (38MS / m), aluminum alloy (20MS / m), stainless steel (2.32MS / m), and titanium alloy (0.56MS / m), the coil impedance phase curves show significant differences within the excitation frequency range.

[0088] Depend on Figure 2 It can be observed that electrical conductivity has a direct impact on the distribution of eddy currents and the strength of the induced magnetic field. As the material's electrical conductivity decreases, the intensity of the induced eddy currents weakens and their flow range also shrinks, which leads to a significant change in the impedance characteristics of the coil. Specifically, materials with higher electrical conductivity (such as copper and aluminum) have higher peak frequencies, while materials with lower electrical conductivity (such as stainless steel and titanium alloys) cause the peak frequencies to shift significantly toward lower frequencies. In addition, the corresponding phase values ​​also show a certain trend of change. This trend shows that the impact of conductivity on the impedance phase can be accurately characterized by changes in peak frequency and phase value.

[0089] The systematic measurement of these peak frequencies and phase values ​​provides important data support for the subsequent fitting of mathematical relationships between different conductivities and peak frequencies. This step not only verifies the method's sensitive response to different conductive materials but also lays a solid foundation for the inversion of conductivity parameters.

[0090] S5. Change the inner diameter of the metal pipe, jump back to step S3 and execute until the number of times the pipe inner diameter is set reaches the required number, and obtain the peak frequency and corresponding phase value of the eddy current sweep phase under different inner diameters.

[0091] In the embodiment of the present application, the inner diameter of the metal pipe is changed to measure the coil impedance phase change curve θ(ω) under different inner diameter conditions. Specifically, the inner diameters of the metal pipe components are set to 5mm, 5.5mm, 6mm, 6.5mm and 7mm, covering the common pipe inner diameter range. For each inner diameter, the corresponding sweep phase curve is measured by repeating step S3 and the peak frequency f of the phase is extracted. peak and phase value θ peak .

[0092] like Figure 3 The results show that the coil impedance phase changes with the excitation frequency due to metal pipes of different inner diameters. The inner diameter has a significant impact on the impedance phase. As can be seen from the figure, as the inner diameter increases, the peak frequency of the coil impedance phase curve gradually shifts toward lower frequencies, and the corresponding phase value also changes. This indicates that changes in the pipe's inner diameter directly affect the intensity and distribution of the induced eddy currents, thereby altering the coil's impedance characteristics.

[0093] By recording and organizing the measurement results under different inner diameter conditions, a complete set of peak frequency and phase values ​​can be obtained. This data provides important support for the subsequent establishment of a mathematical model for the relationship between peak frequency and inner diameter, and also lays the foundation for the ultimate accurate inversion of inner diameter. This step verifies the sensitivity and accuracy of the method under varying inner diameter conditions and further expands its application scenarios and measurement capabilities.

[0094] S6. Based on the phase peak frequency and phase value under different inner diameters, a quadratic curve is used to fit the relationship between the peak frequency phase value and the inner diameter of the pipeline.

[0095] In the embodiment of the present application, the metal pipe eddy current analytical theoretical model is used to calculate the coil impedance phase sweep signal θ caused by pipes with different inner diameters. n (ω), and extract the phase value θ corresponding to the peak frequency n (ω peak ). Furthermore, based on the extracted peak frequency and phase values, a quadratic curve is used to fit the relationship between the peak frequency phase value and the inner diameter of the pipe.

[0096] Specifically, the fitting results are as follows Figure 4 As shown, the expression of the quadratic curve obtained by fitting is:

[0097] a=-2.092θ 2 (ω peak)+29.14θ(ω peak )-14.75

[0098] The fitting results show that there is a good quadratic function relationship between the inner diameter and the phase value corresponding to the peak frequency. The fitting curve provides an accurate mathematical model for the subsequent measurement of the inner diameter of the pipeline.

[0099] Furthermore, in order to verify the stability and applicability of the fitting relationship, the conductivity of the metal pipe is changed in the embodiment of the present application, and the metal pipe eddy current analytical theoretical model is still used to calculate the coil impedance phase sweep signal θ caused by pipes with different inner diameters. n (ω), and extract the phase value θ corresponding to the peak frequency n (ω peak ). The results show that as the conductivity σ changes, the phase value θ n (ω peak ) does not change significantly, and the quadratic function fitting relationship used is unaffected by changes in conductivity. This shows that the relationship between inner diameter and phase peak frequency remains consistent under different conductivity conditions, showing high stability and reliability.

[0100] Specifically, if Figure 2 As shown, when the radius of the metal pipe remains constant, the peak phase of the curve does not change with changes in the pipe's conductivity. This phenomenon further verifies the independence of the quadratic function fitting relationship and provides theoretical support for the subsequent inversion of the pipe's inner diameter under unknown conductivity conditions. Furthermore, because the peak phase is insensitive to changes in conductivity, the quadratic fitting model lays the foundation for the simultaneous measurement of the pipe's inner diameter and conductivity. This step establishes an accurate relationship between the inner diameter and phase values ​​through a robust mathematical model, further improving the measurement accuracy and broad applicability of the method.

[0101] S7. In a double logarithmic coordinate system, based on the peak frequency at different conductivities, a linear fit is used to calculate the relationship between the peak frequency and the inner diameter of the pipe. The linear fit intercept is extracted, and a power function is used to fit the relationship between the intercept and the conductivity.

[0102] In the embodiment of the present application, the metal pipe eddy current analytical theoretical model is used to calculate the coil impedance phase sweep signal θ caused by pipes with different conductivity. m (ω), and extract the peak frequency ω ppak and the corresponding phase value θ m (ω peak By analyzing the measurement data under different conductivity conditions in a double logarithmic coordinate system, a linear fitting method was used to model the relationship between the peak frequency and the inner diameter of the pipe.

[0103] Specifically, in the double logarithmic coordinate system, for the measurement results of different conductivity conditions (titanium alloy, aluminum alloy and copper), the linear relationship between the peak frequency and the inner diameter of the pipe is fitted. The fitting results are as follows: Figure 5 As shown, their expressions are:

[0104] ln(ω peak )=-3.538ln(a)+15.55

[0105] ln(ω peak )=-3.538ln(a)+19.12

[0106] ln(ω peak )=-3.538ln(a)+20.19

[0107] From the fitting results, it can be seen that the relationship between the peak frequency and the inner diameter of the pipeline shows a good linear relationship in the double logarithmic coordinate system, and its slope remains unchanged at -3.538, while the intercept changes significantly with the change of pipeline conductivity.

[0108] Furthermore, the present application changes the inner diameter of the metal pipe and still uses the metal pipe eddy current analytical theoretical model to calculate the coil impedance phase sweep signal θ under different conductivity conditions. m (ω), and extract the peak frequency ω peak and the corresponding phase θ m (ω peak Verification results show that, in a double-logarithmic coordinate system, the slope of the fitted line does not change with changes in pipe conductivity, but the intercept of the fitted line exhibits regular changes with changes in conductivity. This regularity suggests that changes in the intercept can be used to characterize the conductivity properties of a material.

[0109] Specifically, if Figure 2 As shown in Figure 2, the slope of the peak frequency and pipe inner diameter fitting line remains unchanged under different conductivity conditions. After further analyzing the relationship between the intercept of the fitting line and conductivity, the fitting intercept b is extracted, and the power function is used to fit the intercept b and conductivity σ, as shown in Figure 2. Figure 6 The fitting results show that the intercept and conductivity have a power function relationship, which is expressed as follows:

[0110] σ=16.13b 0.05593

[0111] This power function relationship demonstrates that high-precision pipeline conductivity measurements can be achieved by fitting the intercept. This step constructs a complete mathematical relationship model between peak frequency, inner diameter, and conductivity based on the slope and intercept of the fitted line, providing a scientific basis for pipeline conductivity measurement. Furthermore, power function fitting verifies the accuracy and stability of this method, laying the foundation for conductivity measurement in industrial applications.

[0112] S8. Using the fitted quadratic function and power function models, combined with the coil impedance sweep phase change measurement results, the inner diameter and conductivity of the pipeline are simultaneously inverted.

[0113] In the present embodiment, a joint inversion of the pipe inner diameter and conductivity is achieved based on the quadratic function model (the relationship between the inner diameter and the phase corresponding to the peak frequency) and the power function model (the relationship between the conductivity and the linear fit intercept) constructed in the aforementioned steps. Specifically, a swept frequency measurement mode is used to record the phase curve of the coil impedance as it changes with the excitation frequency, and the peak frequency and corresponding phase value in the curve are extracted.

[0114] Then, based on the extracted peak frequency and phase values, first use the quadratic fitting relationship:

[0115] a=-2.092θ 2 (ω peak )+29.14θ(ω peak )-14.75

[0116] The inner diameter a of the pipe is calculated. Then, based on the linear fitting model in the double logarithmic coordinate system, the peak frequency and the intercept b of the inner diameter fitting line are extracted, and combined with the power function model:

[0117] σ=16.13b 0.05593

[0118] The electrical conductivity σ of the pipeline material is calculated. By combining the fitting model with experimental data, the above method can quickly and accurately invert the inner diameter and electrical conductivity of the pipeline at the same time.

[0119] Specifically, this application uses a swept-frequency measurement mode, which only requires extracting the peak frequency and corresponding phase value to complete the parameter inversion calculation. This avoids the complex full-band analysis and redundant data processing, significantly improving measurement efficiency and accuracy. The predicted results obtained in this application are highly consistent with the experimental measurements, verifying the reliability and applicability of the method.

[0120] The method presented here also features a fast response time, a simple measurement process, and no contact with the pipe being tested. It is suitable for testing pipes of varying metal materials and sizes, and possesses broad engineering application value and potential for widespread adoption. This method successfully achieves simultaneous measurement of pipe inner diameter and conductivity, providing efficient and accurate technical support for pipeline performance monitoring and condition assessment.

[0121] In order to implement the above embodiment, the present application also proposes a device for measuring pipeline conductivity and inner diameter based on swept-frequency eddy current. Figure 7 This is a schematic diagram of the structure of a device for measuring the conductivity and inner diameter of a pipeline based on a swept frequency eddy current according to an embodiment of the present application. Figure 7 As shown, the device includes:

[0122] Building module 100, for building an eddy current detection device, designing an absolute eddy current detection coil, placing the coil inside a metal pipe and coaxially arranged with the pipe, passing an alternating current through the coil to excite an alternating magnetic field, and inducing eddy currents on and near the pipe surface;

[0123] The model building module 200 is used to establish a theoretical analytical model of eddy current in metal pipes, set the geometric parameters of the coil, and calculate the analytical expression of the change of coil impedance with the excitation frequency;

[0124] The swept-frequency impedance phase calculation module 300 is used to calculate the change of the impedance phase of the coil with the excitation frequency in the swept-frequency mode based on the theoretical model of the metal pipe eddy current analysis, and to extract the peak frequency and corresponding phase value of the impedance phase;

[0125] The conductivity measurement module 400 is used to change the conductivity of the metal pipe, call the swept frequency impedance phase calculation module, and repeatedly calculate until the number of times the pipe conductivity is set reaches the required number, thereby obtaining the peak frequency and corresponding phase value of the eddy current swept frequency phase under different conductivities;

[0126] The inner diameter measurement module 500 is used to change the inner diameter of the metal pipe, call the swept frequency impedance phase calculation module and the conductivity measurement module, and repeatedly calculate until the number of times the pipe inner diameter is set reaches the required number, thereby obtaining the peak frequency and corresponding phase value of the eddy current swept frequency phase under different inner diameters;

[0127] A quadratic fitting module 600 is used to fit the relationship between the peak frequency phase value and the inner diameter of the pipeline using a quadratic curve based on the phase peak frequency and phase value under different inner diameters;

[0128] A double logarithmic linear fitting module 700 is used to use a linear fit to calculate the relationship between the peak frequency and the inner diameter of the pipe based on the peak frequency at different conductivities in a double logarithmic coordinate system, extract the linear fit intercept, and use a power function to fit the relationship between the intercept and the conductivity;

[0129] The parameter inversion module 800 is used to simultaneously invert the inner diameter and conductivity of the pipeline by using the fitted quadratic function and power function models in combination with the coil impedance sweep phase change measurement results.

[0130] In order to implement the above embodiments, the present application also proposes an electronic device, comprising: a processor, and a memory communicatively connected to the processor; the memory stores computer-executable instructions; the processor executes the computer-executable instructions stored in the memory to implement the method provided by the above embodiments.

[0131] In order to implement the above embodiments, the present application also proposes a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the methods provided in the above embodiments.

[0132] In order to implement the above embodiments, the present application also proposes a computer program product, including a computer program, which implements the methods provided by the above embodiments when executed by a processor.

[0133] The collection, storage, use, processing, transmission, provision and disclosure of user personal information involved in this application are in compliance with relevant laws and regulations and do not violate public order and good morals.

[0134] It is important to note that personal information collected from users should be used for legitimate and reasonable purposes and should not be shared or sold beyond these legitimate uses. Furthermore, such collection / sharing should be conducted only after receiving the user's informed consent, including but not limited to notifying the user to read the user agreement / user notice and sign an agreement / authorization that includes the relevant user information before using the feature. Furthermore, any necessary steps must be taken to safeguard and secure access to such personal information and ensure that others with access to personal information comply with its privacy policy and procedures.

[0135] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this application can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of this application can be achieved. This is not limited herein.

[0136] The above specific embodiments do not constitute a limitation on the scope of protection of this application. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application shall be included within the scope of protection of this application.

Claims

1. A method for measuring pipeline conductivity and inner diameter based on swept frequency eddy current, characterized in that: The following steps are involved: S1. Build an eddy current detection device and design an absolute eddy current detection coil. Place the coil inside a metal pipe and arrange it coaxially with the pipe. Apply an alternating current to the coil to excite an alternating magnetic field, inducing eddy currents on and near the pipe surface. S2. Establish a theoretical analytical model for eddy current in metal pipes, set the geometric parameters of the coil, and calculate the analytical expression of the change of coil impedance with excitation frequency; S3. Based on the theoretical model of metal pipe eddy current analysis, calculate the change of the impedance phase of the coil with the excitation frequency in the sweep frequency mode, and extract the peak frequency and corresponding phase value of the impedance phase; S4. Changing the conductivity of the metal pipe, repeatedly performing step S3 until the number of times the pipe conductivity is set reaches the required number, and obtaining the peak frequency and corresponding phase value of the eddy current sweep phase under different conductivities; S5. Change the inner diameter of the metal pipe, jump back to step S3 and execute again until the number of times the pipe inner diameter is set reaches the required number, and obtain the peak frequency and corresponding phase value of the eddy current sweep frequency phase under different inner diameters; S6. Based on the phase peak frequency and phase value under different inner diameters, a quadratic curve is used to fit the relationship between the peak frequency phase value and the inner diameter of the pipe; S7. In a double logarithmic coordinate system, based on the peak frequency at different conductivities, a linear fit is used to calculate the relationship between the peak frequency and the inner diameter of the pipe, the linear fit intercept is extracted, and a power function is used to fit the relationship between the intercept and the conductivity; S8. Using the fitted quadratic function and power function models, combined with the coil impedance sweep phase change measurement results, the inner diameter and conductivity of the pipeline are simultaneously inverted.

2. The method according to claim 1, characterized in that The geometric parameters of the coil include: the number of turns of the coil , inner diameter of the coil and outer diameter , coil height .

3. The method according to claim 2, characterized in that The analytical expression of the change of the coil impedance with the excitation frequency is: Where: Where, is the change in coil impedance, is the excitation angular frequency, is the inner radius of the metal pipe, is the electrical conductivity of the metal pipe, is the magnetic constant, is the integral variable, which is related to the wave number, is an integral function used to describe the coil current distribution, is the influence coefficient of impedance change, is the complex wave number, and are the 0th and 1st order modified Bessel functions of the first kind, respectively, and are the 0th and 1st order modified Bessel functions of the second kind respectively.

4. The method according to claim 3, characterized in that The method of calculating the change of the impedance phase of the coil with the excitation frequency based on the metal pipe eddy current analytical theoretical model in the frequency sweep mode and extracting the peak frequency and corresponding phase value of the impedance phase includes: Set the sweep excitation frequency range from 10 Hz to 1 MHz and calculate the coil impedance phase at different excitation frequencies. ; Use polynomial at the minimum Fit the curve near the peak frequency, set the first-order derivative of the fitting polynomial to zero, and obtain the peak frequency and corresponding phase value.

5. The method according to claim 4, characterized in that The relationship between the peak frequency and phase value and the inner diameter of the pipeline is fitted using a quadratic curve based on the phase peak frequency and phase value under different inner diameters, including: The metal pipe eddy current analytical theoretical model is used to calculate the coil impedance phase sweep frequency signal caused by pipes with different inner diameters. , extract the phase corresponding to the peak frequency , and a quadratic curve was used to fit the relationship between the peak frequency phase value and the inner diameter; Changing the conductivity of the metal pipe, still using the metal pipe eddy current analytical theoretical model, respectively calculate the coil impedance phase sweep signal caused by pipes with different inner diameters , extract the phase corresponding to the peak frequency , and a quadratic curve was used to fit the relationship between the peak frequency phase value and the inner diameter; Verification: Phase Does not change with conductivity The quadratic function fitting relationship adopted will not change due to the change of conductivity.

6. The method according to claim 5, characterized in that The method of using a linear fit to fit the relationship between the peak frequency and the inner diameter of the pipe based on the peak frequency at different conductivities in a double logarithmic coordinate system, extracting the linear fit intercept, and using a power function to fit the relationship between the intercept and the conductivity includes: The metal pipe eddy current analytical theoretical model is used to calculate the coil impedance phase sweep frequency signal caused by pipes with different conductivity. , extract the phase corresponding to the peak frequency , and in the double logarithmic coordinate system, the relationship between the peak frequency and the pipeline conductivity is fitted linearly; By changing the inner diameter of the metal pipe, the eddy current analytical theoretical model of the metal pipe is used to calculate the coil impedance phase sweep signal caused by pipes with different electrical conductivities. , extract the phase corresponding to the peak frequency , and in a double logarithmic coordinate system, a linear fit is used to find the relationship between the peak frequency and the pipeline conductivity. It is verified that the slope of the fitted line does not change with changes in pipeline conductivity, while the intercept of the fitted line changes with changes in conductivity. The intercept of the fitted straight line was extracted, and the power function was used to fit the relationship between the intercept and conductivity.

7. A device for measuring pipeline conductivity and inner diameter based on swept frequency eddy current, characterized in that: include: A construction module is provided for constructing an eddy current detection device, designing an absolute eddy current detection coil, placing the coil inside a metal pipe and coaxially arranged with the pipe, passing an alternating current through the coil to excite an alternating magnetic field, and inducing eddy currents on and near the pipe surface; The model building module is used to establish the analytical theoretical model of eddy current in metal pipes, set the geometric parameters of the coil, and calculate the analytical expression of the change of coil impedance with excitation frequency; A swept-frequency impedance phase calculation module is used to calculate the change of the impedance phase of the coil with the excitation frequency in a swept-frequency mode based on the metal pipe eddy current analytical theoretical model, and to extract the peak frequency and corresponding phase value of the impedance phase; The conductivity measurement module is used to change the conductivity of the metal pipe, call the swept frequency impedance phase calculation module, repeatedly calculate until the number of times the pipeline conductivity is set reaches the required number, and obtain the peak frequency and corresponding phase value of the eddy current swept frequency phase under different conductivities; An inner diameter measurement module is used to change the inner diameter of the metal pipe, call the swept frequency impedance phase calculation module and the conductivity measurement module, and repeatedly calculate until the number of times the pipe inner diameter is set reaches the required number, thereby obtaining the peak frequency and corresponding phase value of the eddy current swept frequency phase under different inner diameters; A quadratic fitting module is used to fit the relationship between the peak frequency phase value and the inner diameter of the pipe using a quadratic curve based on the phase peak frequency and phase value under different inner diameters; The double logarithmic linear fitting module is used to use a linear fit to calculate the relationship between the peak frequency and the inner diameter of the pipe based on the peak frequency at different conductivities in a double logarithmic coordinate system, extract the linear fit intercept, and use a power function to fit the relationship between the intercept and the conductivity. The parameter inversion module is used to simultaneously invert the inner diameter and conductivity of the pipeline by using the fitted quadratic function and power function models combined with the coil impedance sweep phase change measurement results.

8. An electronic device, characterized in that: include: a processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 6 when executed by a processor.

10. A computer program product, characterized in that The invention comprises a computer program, which implements the method according to any one of claims 1 to 6 when the computer program is executed by a processor.

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