Method for measuring conductivity and inner diameter of pipeline based on sweep frequency eddy current

Abstract

The invention provides a method for measuring the conductivity and the inner diameter of a pipeline based on sweep frequency eddy current. The method comprises the following steps: establishing an eddy current detection device, designing an absolute eddy current detection coil, placing the coil in a metal pipeline, arranging the coil and the pipeline coaxially, introducing alternating current to excite an alternating magnetic field, and inducing eddy current on the surface and the near surface of the pipeline; establishing a metal pipeline eddy current analysis theoretical model, setting coil geometric parameters, and calculating an analysis expression of coil impedance changing along with excitation frequency; calculating the peak frequency and the corresponding phase value of the impedance phase of the coil in a frequency sweep mode, respectively changing the conductivity and the inner diameter of the pipeline, extracting the corresponding peak frequency and phase value, and constructing an inner diameter relation model based on quadratic curve fitting and a conductivity relation model based on power function fitting; and inverting the inner diameter and the conductivity of the metal pipeline by combining a coil impedance sweep frequency phase measurement result. The method can be used for simultaneously measuring the conductivity and the inner diameter of the pipeline, and is suitable for nondestructive testing and performance evaluation of the metal pipeline.

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 pipes are widely used in petrochemical, natural gas transportation, water conservancy projects, power transmission and other fields due to their excellent mechanical strength, electrical conductivity and corrosion resistance. However, metal pipes often need to withstand a variety of complex loads during service. Especially under long-term service conditions, the pipeline structure will be damaged by factors such as fatigue and stress corrosion, and may even crack or fail. The accumulation of these damages will not only affect the mechanical properties of the pipeline, but may also threaten the safety of the entire system. Therefore, damage detection and performance evaluation of metal pipes in service is an important engineering requirement to ensure their safe operation.

[0003] The electromagnetic properties of metal pipelines are closely related to their microstructure, chemical composition and mechanical properties. During the service life of the pipeline, its microstructure and defects will cause changes in electromagnetic parameters such as conductivity. By measuring the electromagnetic parameters of the pipeline, its internal damage state, such as fatigue, cracks and corrosion, can be indirectly evaluated, thereby achieving non-destructive testing and condition monitoring. Based on this principle, electromagnetic technology has gradually become an important research direction in the field of non-destructive 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 especially suitable for defect detection, corrosion evaluation and electromagnetic property measurement of metal materials. At the same time, since 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 some extent.

[0006] To this end, the first object of the present 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 pipeline conductivity and inner diameter measuring device based on swept frequency eddy current.

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

[0009] A fourth objective of the present application is to provide a computer-readable storage medium.

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

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

[0012] S1. Build an eddy current detection device, design an absolute eddy current detection coil, place the coil inside a metal pipe and arrange it coaxially with the pipe, pass an alternating current through the coil to excite an alternating magnetic field, and induce eddy currents on the surface and near the surface of the pipe;

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

[0014] S3. Based on the theoretical model of metal pipe eddy current analysis, the impedance phase of the coil is calculated as the excitation frequency changes under the sweep frequency mode, and the peak frequency and corresponding phase value of the impedance phase are extracted;

[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 frequency phase under different conductivity;

[0016] S5, changing the inner diameter of the metal pipe, jumping back to step S3 and executing until the number of times the inner diameter of the pipe is set reaches the required number, and obtaining 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 pipeline;

[0018] S7. 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 pipeline, 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 of 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 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, based on the metal pipe eddy current analytical theoretical model, calculating the impedance phase of the coil as the excitation frequency changes in the sweep frequency mode, and extracting the peak frequency and corresponding phase value of the impedance phase, includes:

[0027] The sweep excitation frequency range is set to 10 Hz to 1 MHz, and the coil impedance phase θ(ω) at different excitation frequencies is calculated;

[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 phase peak frequency and phase value under different inner diameters are used to fit the relationship between the peak frequency phase value and the inner diameter of the pipeline using a quadratic curve, including:

[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 frequency 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 pipeline, 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 pipeline eddy current analytical theoretical model is used to calculate the coil impedance phase sweep signal θ caused by pipelines with different conductivity. m (ω), extract the phase θ corresponding to the peak frequency m (ω peak ), and the relationship between the peak frequency and the pipeline conductivity is fitted linearly in a double logarithmic coordinate system;

[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 frequency 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 fit is used to determine the relationship between the peak frequency and the pipeline conductivity; it is verified that: the slope of the fitting line will not change with the change of pipeline conductivity, and the intercept of the fitting line will change with the change of conductivity;

[0036] The intercept of the fitting line was extracted, and the relationship between the intercept and conductivity was fitted using a power function.

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

[0038] A building module is used to build an eddy current detection device, design an absolute eddy current detection coil, place the coil inside a metal pipe and arrange it coaxially with the pipe, pass an alternating current through the coil to excite an alternating magnetic field, and induce eddy currents on and near the surface of the pipe;

[0039] Model building module, 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 the excitation frequency;

[0040] A swept frequency impedance phase calculation module is used to calculate the impedance phase of the coil as the excitation frequency changes under 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, and repeatedly calculate until the number of times the pipeline conductivity is set reaches the required number, so as to obtain the peak frequency and corresponding phase value of the eddy current swept frequency phase under different conductivity;

[0042] The 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 inner diameter of the pipe is set reaches the required number, so as to obtain 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 pipeline 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 find the relationship between the peak frequency and the inner diameter of the pipeline 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, the third aspect of the present application provides an electronic device, including: 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 aspect embodiment of the present application proposes a computer-readable storage medium, in which computer-readable storage medium is stored computer execution instructions, and when the computer execution 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 purpose, the fifth aspect of the present application proposes a computer program product, which implements any method in the first aspect when executed by a processor.

[0051] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:

[0052] By utilizing the swept-frequency eddy current detection technology and combining the characteristics of impedance phase changing with frequency, the present application can achieve high-precision measurement of the conductivity and inner diameter of metal pipes to meet the requirements of industrial detection for accuracy and reliability. The measurement processes of the inner diameter and conductivity of the pipe are decoupled by using quadratic curve fitting and power function fitting. The functional relationships between the inner diameter and impedance phase and between conductivity and frequency are established through independent mathematical models, avoiding mutual interference between parameters and improving measurement accuracy and applicability of the model.

[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 the 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 a swept frequency eddy current 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 calculation results of the coil impedance phase under different pipeline inner diameters provided in an embodiment of the present application;

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

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

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

[0062] Figure 7 A schematic diagram of the structure 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] Embodiments of the present application are described in detail below, and examples of the embodiments 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] In view of the problems existing in the prior art, this application combines theoretical modeling, impedance analysis and mathematical fitting methods to propose a method for measuring pipeline conductivity and inner diameter based on swept frequency eddy current. This method uses non-contact, highly sensitive detection means to achieve efficient measurement of the conductivity and inner diameter of metal pipelines without stopping the machine. By real-time monitoring of changes in pipeline conductivity, the fatigue, defects and corrosion status of the pipeline can be evaluated, providing reliable technical support for in-service status monitoring of pipelines, and providing an important basis for the safe operation and life management of industrial equipment.

[0065] Figure 1 The present invention provides a flow chart of a method for measuring the conductivity and inner diameter of a pipeline based on a frequency sweep eddy current. Figure 1 As shown, the method comprises the following steps:

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

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

[0068] In the embodiment of the present application, a copper metal pipe is selected as the object to be measured, and its excellent electrical conductivity ensures that the eddy current induction effect is significant. The change in the coil impedance phase is determined by the intensity and flow range of the eddy current, and the measurement of the impedance phase provides basic data support for the subsequent extraction of the conductivity and size of the pipeline. By optimizing the geometric parameters and excitation signal of the coil, the embodiment of the present application can ensure the sensitivity and applicability of the measurement, thereby laying a good foundation for subsequent steps.

[0069] The eddy current detection device of the embodiment of the present application has a reasonable design and a compact structure, and can realize non-contact measurement of the conductivity and inner diameter of tubular components, and is particularly suitable for the size and electromagnetic property detection of metal pipes such as copper, aluminum, and stainless steel. This step lays a solid foundation for the subsequent establishment of an eddy current analytical model and the extraction of accurate parameters of the pipe conductivity and size, while ensuring the high versatility and high reliability of the detection 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 the excitation frequency.

[0071] In the embodiment of the present application, the geometric parameters of the coil include: the number of turns N of the coil, the inner diameter r1 and the outer diameter r2 of the coil, and the height l2-l1 of the coil. Based on these geometric parameters, the embodiment of the present application establishes an eddy current analytical theoretical model of the metal pipeline to calculate the analytical expression of the change of the coil impedance with the excitation frequency, thereby revealing the influence of the pipeline conductivity and inner diameter on the coil impedance. Specifically, the analytical expression of the change of the coil impedance with the excitation frequency is:

[0072]

[0073] Where:

[0074]

[0075]

[0076] Where 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 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.

[0077] In one embodiment of the present application, the inner diameter a of the pipeline 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 geometric dimensions. The establishment of the analytical model reveals the distribution of eddy currents and their influence on the coil impedance phase by comprehensively considering the conductivity and geometric parameters of the pipeline material.

[0078] like Figure 2As shown in the figure, by using this analytical model to calculate the change of the coil impedance phase with the excitation frequency, it can be 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 electromagnetic characteristics and geometric parameters of the pipeline on the 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 a function of the excitation frequency in the sweep frequency mode, and the peak frequency and corresponding phase value of the impedance phase are extracted.

[0080] In the embodiment of the present application, the sweep excitation frequency range is first set to 10 Hz to 1 MHz, the coil is gradually excited using this frequency range, and the impedance phase θ(ω) of the coil at different excitation frequencies is calculated. The curve of the impedance phase changing with the excitation frequency can reflect the influence of the conductivity and inner diameter of the pipeline on the electromagnetic characteristics.

[0081] In order to extract the peak frequency of the impedance phase and its corresponding phase value, the present 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 and corresponding phase value of the phase curve can be accurately obtained. Through polynomial fitting, the errors caused by measurement noise and frequency resolution limitations can be effectively reduced, thereby improving the accuracy of the calculation.

[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 +50)Hz], a 4th-order polynomial fitting is performed on the impedance phase curve. The final peak frequency and the corresponding phase value are obtained by calculating the first-order derivative f′(ω)=0 of the fitting polynomial 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, and provide basic data for mathematical fitting and parameter inversion in subsequent steps.

[0084] S4, changing the conductivity of the metal pipe, and 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 frequency phase under different conductivity.

[0085] In the embodiment of the present application, the conductivity of the metal pipe is adjusted by changing the material of the metal pipe, and the impedance phase change of the coil under different conductivity conditions is measured respectively. Specifically, the metal pipe components are selected from the following five common materials: copper, aluminum, aluminum alloy, stainless steel and titanium alloy. The conductivity of these materials is 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 change of coil impedance phase caused by different materials is as follows: Figure 2 As shown. Figure 2 It can be seen that as the conductivity of the pipeline material decreases, the peak frequency of the coil impedance phase gradually shifts to the low frequency direction, 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 conductivity has a direct effect on the eddy current distribution and the induced magnetic field strength. As the conductivity of the material decreases, the intensity of the induced eddy current weakens and its flow range also decreases, which leads to a significant change in the impedance characteristics of the coil. Specifically, materials with higher conductivity (such as copper and aluminum) have higher peak frequencies, while materials with lower conductivity (such as stainless steel and titanium alloy) cause the peak frequency to move significantly toward low frequencies. In addition, the corresponding phase value also shows a certain trend of change. This trend shows that the effect 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 the mathematical relationship between different conductivities and peak frequencies. This step not only verifies the sensitive response of this method to materials with different conductivity, but also lays a solid foundation for the inversion of conductivity parameters.

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

[0091] In the embodiment of the present application, by changing the inner diameter of the metal pipe, the coil impedance phase change curve θ(ω) under different inner diameter conditions is measured. 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 frequency sweep phase curve is measured by repeatedly executing step S3 and the peak frequency f of the phase is extracted. peak and phase value θ peak .

[0092] like Figure 3 As shown in the figure, the results of the change of the coil impedance phase caused by metal pipes with different inner diameters with the excitation frequency show that the inner diameter has a significant effect on the impedance phase. It can be observed from the figure that as the inner diameter increases, the peak frequency of the coil impedance phase curve gradually shifts to the low frequency direction, and the corresponding phase value also shows a certain change. This shows that the change in the inner diameter of the pipeline directly affects the intensity and distribution range of the induced eddy current, thereby changing the impedance characteristics of the coil.

[0093] By recording and collating the measurement results under different inner diameter conditions, a complete set of peak frequency and phase value data can be obtained. These data provide important support for the subsequent establishment of a mathematical relationship model between peak frequency and inner diameter, and also lay the foundation for the ultimate realization of accurate inversion of the inner diameter. This step verifies the sensitivity and accuracy of the method under changes in inner diameter, and further expands the application scenarios and measurement capabilities of the method.

[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 frequency 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 ). Further, according to the extracted peak frequency and phase value, a quadratic curve is used to fit the relationship between the peak frequency phase value and the inner diameter of the pipeline.

[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] It can be seen from the fitting results 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 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), 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 ) will not change significantly, and the quadratic function fitting relationship adopted will not be affected by the change of conductivity. This shows that the relationship between the inner diameter and the phase peak frequency remains consistent under different conductivity conditions and has high stability and reliability.

[0100] Specifically, Figure 2 As shown in the figure, when the radius of the metal pipe remains unchanged, the peak phase of the curve will not change with the change of the pipe conductivity. This phenomenon further verifies the independence of the quadratic function fitting relationship and provides theoretical support for the subsequent inversion of the inner diameter of the pipe under unknown conductivity conditions. At the same time, since the peak phase is insensitive to changes in conductivity, the quadratic fitting model lays the foundation for the simultaneous measurement of the inner diameter and conductivity of the pipe. This step establishes an accurate relationship between the inner diameter and the phase value through a robust mathematical model, further improving the measurement accuracy and wide applicability of the method.

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

[0102] In the embodiment of the present application, the metal pipeline eddy current analytical theoretical model is used to calculate the coil impedance phase sweep frequency signal θ caused by pipelines 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 is used to model the relationship between the peak frequency and the inner diameter of the pipe.

[0103] Specifically, in the double logarithmic coordinate system, the linear relationship between the peak frequency and the inner diameter of the pipeline is fitted for the measurement results of different conductivity conditions (titanium alloy, aluminum alloy and copper). 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 ). The verification results show that in the double logarithmic coordinate system, the slope of the fitting line will not change with the change of pipeline conductivity, but the intercept of the fitting line will change regularly with the change of conductivity. This regularity shows that the change of intercept can be used to characterize the conductivity characteristics of the material.

[0109] Specifically, Figure 2 As shown in Figure 2, the slope of the peak frequency and pipeline 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 present a power function relationship, and the expression is:

[0110] σ=16.13b 0.05593

[0111] This power function relationship shows that high-precision measurement of pipeline conductivity can be achieved by fitting the intercept. This step constructs a complete mathematical relationship model of peak frequency, inner diameter and conductivity based on the slope and intercept of the fitting line, providing a scientific basis for the measurement of pipeline conductivity. At the same time, the accuracy and stability of the method are verified by power function fitting, 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 embodiment of the present application, 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 fitting intercept) constructed in the above steps are used to realize the joint inversion of the inner diameter and conductivity of the pipeline. Specifically, the phase curve of the coil impedance changing with the excitation frequency is recorded by using the sweep frequency measurement mode, and the peak frequency and the 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 pipeline is calculated. Then, according to 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 conductivity σ of the pipeline material is calculated. The above method can quickly and accurately invert the inner diameter and conductivity of the pipeline at the same time by combining the fitting model with the experimental data.

[0119] Specifically, this application adopts the swept frequency measurement mode, and only needs to extract the peak frequency and the corresponding phase value to complete the parameter inversion calculation, avoiding the complex full-band analysis and redundant data processing, and significantly improving the measurement efficiency and accuracy. The results predicted by this application are highly consistent with the experimental measurement values, verifying the reliability and applicability of the method.

[0120] At the same time, the method of this application has a fast response speed, a simple measurement process, no need to contact the measured pipeline, and is suitable for pipeline detection of different metal materials and sizes, with broad engineering application value and promotion prospects. Through this step, the simultaneous measurement of the inner diameter and conductivity of the pipeline is successfully achieved, providing efficient and accurate technical support for pipeline performance monitoring and status evaluation.

[0121] In order to implement the above embodiments, the present application also proposes a pipeline conductivity and inner diameter measurement device based on swept-frequency eddy current. Figure 7 The schematic diagram of the structure of a pipeline conductivity and inner diameter measuring device based on swept frequency eddy current provided in an embodiment of the present application. Figure 7 As shown, the device comprises:

[0122] Building module 100, used to build an eddy current detection device, design an absolute eddy current detection coil, place the coil inside a metal pipe and arrange it coaxially with the pipe, pass an alternating current through the coil to excite an alternating magnetic field, and induce eddy currents on the surface and near the surface of the pipe;

[0123] The model building module 200 is used to establish a theoretical analytical model of eddy current in a metal pipe, set geometric parameters of the coil, and calculate an 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 impedance phase of the coil as the excitation frequency changes in the swept frequency mode based on the metal pipe eddy current analytical theoretical model, and 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 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;

[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 inner diameter of the pipe is set reaches the required number, and obtain 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 fit the relationship between the peak frequency and the inner diameter of the pipeline based on the peak frequency under 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 by 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 should be noted that personal information from users should be collected for legitimate and reasonable purposes and should not be shared or sold outside of these legitimate uses. In addition, such collection / sharing should be carried out after receiving the user's informed consent, including but not limited to notifying the user to read the user agreement / user notice and sign the agreement / authorization including authorization of relevant user information before the user uses the function. In addition, any necessary steps should be taken to protect and safeguard access to such personal information data and ensure that others who have access to personal information data comply with its privacy policy and procedures.

[0135] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this application can be executed in parallel, sequentially or in different orders, as long as the expected results of the technical solution of this application can be achieved, and this document is not limited here.

[0136] The above specific implementations do not constitute a limitation on the protection scope of this application. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of this application should be included in the protection scope of this application.

Claims

1. A method for measuring pipeline conductivity and inner diameter based on frequency sweeping eddy current, characterized in that: The following steps are involved: S1. Build an eddy current detection device, design an absolute eddy current detection coil, place the coil inside a metal pipe and arrange it coaxially with the pipe, pass an alternating current through the coil to excite an alternating magnetic field, and induce eddy currents on the surface and near the surface of the pipe; S2. Establish a theoretical model for eddy current analysis of metal pipes, set the geometric parameters of the coil, and calculate the analytical expression of the change of coil impedance with the excitation frequency; S3. Based on the theoretical model of metal pipe eddy current analysis, the impedance phase of the coil is calculated as the excitation frequency changes under the sweep frequency mode, and the peak frequency and corresponding phase value of the impedance phase are extracted; 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 frequency phase under different conductivity; S5, changing the inner diameter of the metal pipe, jumping back to step S3 and executing until the number of times the inner diameter of the pipe is set reaches the required number, and obtaining 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 pipeline; S7. 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 pipeline, 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 N of the coil, the inner diameter r1 and the outer diameter r2 of the coil, and the height l2-l1 of the coil.

3. The method according to claim 2, characterized in that The analytical expression of the coil impedance changing with the excitation frequency is: Where: 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 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.

4. The method according to claim 3, characterized in that Based on the metal pipe eddy current analytical theoretical model, the impedance phase of the coil is calculated in a sweep frequency mode with the excitation frequency, and the peak frequency and corresponding phase value of the impedance phase are extracted, including: The sweep excitation frequency range is set to 10 Hz to 1 MHz, and the coil impedance phase θ(ω) at different excitation frequencies is calculated; 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.

5. The method according to claim 4, characterized in that The relationship between the peak frequency and the phase value under different inner diameters is fitted by a quadratic curve and the inner diameter of the pipeline, including: 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; 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 frequency 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; 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.

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 pipeline 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 pipeline eddy current analytical theoretical model is used to calculate the coil impedance phase sweep signal θ caused by pipelines with different conductivity. m (ω), extract the phase θ corresponding to the peak frequency m (ω peak ), and the relationship between the peak frequency and the pipeline conductivity is fitted linearly in a double logarithmic coordinate system; 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 frequency 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 fit is used to find the relationship between the peak frequency and the pipeline conductivity; it is verified that: the slope of the fitting line will not change with the change of pipeline conductivity, and the intercept of the fitting line will change with the change of conductivity; The intercept of the fitting line was extracted, and the relationship between the intercept and conductivity was fitted using a power function.

7. A pipeline conductivity and inner diameter measuring device based on swept frequency eddy current, characterized in that: include: A building module is used to build an eddy current detection device, design an absolute eddy current detection coil, place the coil inside a metal pipe and arrange it coaxially with the pipe, pass an alternating current through the coil to excite an alternating magnetic field, and induce eddy currents on and near the surface of the pipe; Model building module, 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 the excitation frequency; A swept frequency impedance phase calculation module is used to calculate the impedance phase of the coil as the excitation frequency changes under 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, and repeatedly calculate until the number of times the pipeline conductivity is set reaches the required number, so as to obtain the peak frequency and corresponding phase value of the eddy current swept frequency phase under different conductivity; The 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 inner diameter of the pipe is set reaches the required number, so as to obtain 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 pipeline 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 find the relationship between the peak frequency and the inner diameter of the pipeline 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 being executed by a processor.

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