A method, system and device for non-destructive detection of the depth of a power pole based on nonlinear acoustic characteristics

Abstract

This invention relates to a non-destructive testing method, system, and equipment for the burial depth of utility poles based on nonlinear acoustic features. The testing method includes: S1, applying a broadband transient impact excitation to the sidewall of a concrete utility pole to induce a vibration response in the dominant resonant mode; S2, simultaneously acquiring the force signal of the impact excitation and the acceleration signal of the vibration response to obtain a time-domain response signal; S3, extracting nonlinear acoustic features from the response signal, including at least one of higher harmonic features and resonant frequency shift features; S4, inputting the extracted nonlinear acoustic features into a calibrated regression model to output a quantitative index characterizing the degree of delamination damage at the steel-concrete interface in the concrete utility pole. This invention overcomes the limitation of existing linear acoustic methods, which can only qualitatively judge severe damage, and enables early detection and quantitative assessment of hidden damage such as early delamination and microcracks at the steel-concrete interface.

Description

Technical Field

[0001] This invention relates to the field of pole burial depth detection technology, specifically to a non-destructive testing method, system, and equipment for pole burial depth based on nonlinear acoustic characteristics. Background Technology

[0002] Reinforced concrete poles, as core supporting infrastructure of power transmission and distribution systems, are widely used in urban and rural power transmission and distribution networks, urban lighting, and other fields. Their health status is directly related to the stable operation of the power system, personal safety, and the safety of public property. Because poles are exposed to the complex outdoor environment for extended periods, they must continuously withstand various factors such as wind loads, conductor tension, icing, freeze-thaw cycles, foundation settlement, concrete carbonization, and steel corrosion. This makes them prone to various types of damage, including interface peeling, rust-induced cracks, and separation of the steel-concrete interface. These types of damage are characterized by their insidious nature and gradual development. If they are not detected and assessed in a timely manner, they can easily lead to further damage, even causing pole breakage or collapse, resulting in large-scale power outages and significant safety hazards.

[0003] Currently, various technical solutions have been developed in the field of non-destructive testing of pole damage. Among them, acoustic-based testing methods have been widely used due to their advantages such as non-contact operation and ease of use. For example, the technical solution described in Reference 1.

[0004] Reference 1: Chinese patent document with publication number CN111595374A.

[0005] Reference 1 describes a method for detecting the burial depth and damage of utility poles based on Rayleigh waves. The method includes determining the location of reinforcing bars, drawing contour lines on the land portion of the pole, and marking the locations of the reinforcing bars on these lines; placing an exciter and a pickup on the upper and lower sides of the contour lines; the signal emitted by the exciter decreasing from high frequency to low frequency, and the pickup starting to scan and detect the signal; each time the pickup detects a reflected signal, the time t (from the exciter emitting the signal to the pickup detecting the signal at that frequency), the frequency f, and the wave velocity V are transmitted to a processing device; after measurement at each marked point, a line graph showing the change of time t with frequency f from high to low is created in the processing device until all reinforcing bar marked points are measured. All line graphs are then placed in a coordinate system to find the characteristic frequency f0, and combined with the wave velocity V and propagation time, the burial depth and damage status of the utility pole are determined.

[0006] The aforementioned technical solution determines whether a utility pole is damaged by analyzing the change in the propagation time of Rayleigh waves after encountering a crack. However, the linear acoustic parameters (such as wave velocity and propagation time) upon which this damage assessment relies are not sensitive to minor early-stage damage to the pole (such as minor steel-concrete interface delamination and early rust-induced cracks) and cannot be quantitatively assessed. Furthermore, the internal structure of reinforced concrete poles is complex, containing not only potential damage but also various structures such as steel bars, clamps, flanges, and concrete particle boundaries. When an excitation signal is applied to the pole to generate Rayleigh waves, the excitation signal produces numerous linear reflection echoes at these internal structures. These structural reflection echoes are highly prone to aliasing with the reflection echoes generated by actual damage in the time domain. The linear acoustic parameters used in this existing technology cannot effectively distinguish whether the signal fluctuations are caused by material nonlinearity (i.e., damage characteristics) or by linear reflections from the internal structures, leading to misjudgments during the detection process and affecting the reliability of the detection results. Summary of the Invention

[0007] The purpose of this invention is to solve the above-mentioned technical problems existing in the prior art and to provide a non-destructive testing method, system and equipment for pole burial depth based on nonlinear acoustic characteristics.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics, comprising the following steps: Step S1: Apply a broadband transient impact excitation to the sidewall of the concrete pole to induce a vibration response in the pole that includes at least one dominant resonant mode; Step S2: Synchronously acquire the force signal of the impact excitation and the acceleration signal of the vibration response to obtain the time-domain response signal; Step S3: Extract nonlinear acoustic features from the response signal. The nonlinear acoustic features include at least one of higher harmonic features and resonant frequency shift features. Step S4: Input the extracted nonlinear acoustic features into a calibrated regression model and output a quantitative index to characterize the degree of delamination damage at the steel-concrete interface in concrete poles.

[0009] As a further optimization of the non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics of the present invention, step S1 further includes: performing at least two broadband transient impact excitations at different excitation levels on the same measuring point by replacing the excitation hammer with one of different materials or changing the excitation intensity, so as to obtain response signals under different excitation levels.

[0010] As a further optimization of the non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics of this invention, the nonlinear coefficient β is calculated, and the trend of β changing with the excitation level is analyzed to distinguish between classical nonlinear and non-classical nonlinear elastic behavior: Where A2f is the second harmonic amplitude of the response signal under different excitation levels, A f This corresponds to the fundamental frequency amplitude; As a further optimization of the non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics of the present invention, step S3 specifically includes: performing spectral analysis on the response signal, calculating the ratio of the second harmonic amplitude to the corresponding fundamental frequency amplitude in its spectrum, or calculating the normalized measure of the spectral peak at the second harmonic frequency point generated by the coupling of the fundamental frequency and using the calculation result as the higher harmonic feature.

[0011] As a further optimization of the non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics of the present invention, the step of calculating the normalized measure of the spectral peak at the second harmonic frequency point in the dual spectrum further includes: defining the nonlinear intrinsic parameter β. bis for: Where B(f1, f2) is the bispectral density of the response signal, f0 is the fundamental frequency of the dominant resonance mode, and the denominator is all frequency points (f0, f1, f2) on the diagonal of the bispectral density. i f i The average value of the amplitude, where N is the number of frequency points; The calculated β bis The value is used as the characteristic of the higher harmonics.

[0012] As a further optimization of the non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics of the present invention, step S3 specifically includes: By performing time-frequency analysis on the response signal, the instantaneous frequency function and instantaneous amplitude function of the dominant resonance mode are extracted; The nonlinear softening relationship in which the instantaneous frequency monotonically decreases as the instantaneous amplitude increases was identified; By fitting the slope of this relationship, a nonlinear frequency shift coefficient is obtained and used as a characteristic of the resonant frequency shift.

[0013] As a further optimization of the non-destructive testing method for pole burial depth based on nonlinear acoustic features of the present invention, the regression model in step S4 is a support vector regression model or a Gaussian process regression model. This model is obtained by pre-training on a calibration database. The calibration database contains corresponding data pairs of nonlinear acoustic features and peeling damage indices that have been pre-established through finite element simulation and / or physical accelerated corrosion tests under known different peeling conditions.

[0014] As a further optimization of the non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics of the present invention, the peeling damage index includes the percentage of peeling area at the steel-concrete interface, the thickness of the peeling gap, or the quantitative classification of the degree of filling of corrosion products.

[0015] On the other hand, the present invention also provides a non-destructive testing system for pole burial depth based on nonlinear acoustic characteristics, comprising: An excitation module is used to apply a broadband transient impact excitation to the sidewall of the concrete pole to induce a vibration response in the pole; and The sensing and acquisition module includes a force sensor for measuring the impact excitation force, an accelerometer for measuring the vibration response acceleration, and a high-speed data acquisition unit for simultaneously acquiring the signals of both; and The processor is configured to perform the steps of the above method to process the acquired signals and to output quantitative indicators of peel damage.

[0016] On the other hand, the present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, characterized in that the processor executes the computer program to implement the steps of the above-described method.

[0017] This invention offers the following advantages: It overcomes the limitation of existing linear acoustic methods, which can only qualitatively assess severe damage, and enables early detection and quantitative assessment of hidden damage such as early delamination at the steel / concrete interface and microcracks. By tracking the nonlinear acoustic characteristics of the material caused by damage, it can effectively distinguish damage signals from the linear reflection of the structure itself, significantly reducing the false positive rate. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the non-destructive testing method for pole burial depth. Detailed Implementation

[0019] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0021] Furthermore, the described embodiments are merely some embodiments of this application, and not all embodiments. Typically in... The components of the embodiments of this application described and illustrated in the accompanying drawings can be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] It should be noted that the term "comprising" will be used in the embodiments of this application to indicate the presence of the features declared thereafter, but does not exclude the addition of other features.

[0023] <Example 1> like Figure 1 As shown: A non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics, comprising the following steps: Step S1: Apply a broadband transient impact excitation to the sidewall of the concrete pole to induce a vibration response in the pole that includes at least one dominant resonant mode.

[0024] Transient pulses are applied to the sidewall of the pole using a broadband impact hammer equipped with a force sensor (containing hammerheads made of polyester, aluminum, steel, etc.). The force signal is recorded synchronously for reference. The impact excitation is rich in low-frequency components, which can excite the overall bending and longitudinal resonant modes of the structure, covering a frequency range from hundreds of Hz to several kHz.

[0025] At least one high-sensitivity accelerometer is rigidly fixed to the side of the pole with a magnetic base or clamp, located between the excitation point and the expected damage zone.

[0026] Signal acquisition: The excitation force F(t) and acceleration response a(t) of the hammer are synchronously acquired at a sampling rate of not less than 200kHz. A single impact response signal is obtained under one impact, with a window length of 100~500ms, which is sufficient to capture the multi-order resonance and attenuation of the structure.

[0027] By replacing the excitation hammer with one of different materials or changing the excitation intensity, the same measuring point is subjected to at least two broadband transient impact excitations at different excitation levels to obtain response signals under different excitation levels.

[0028] Calculate the nonlinear coefficient β, and by analyzing the trend of β changing with the excitation level, distinguish between classical and non-classical nonlinear elastic behavior: Among them, A 2f Let A be the second harmonic amplitude of the response signal under different excitation levels. f This corresponds to the fundamental frequency amplitude.

[0029] Step S2: Synchronously acquire the force signal of the impact excitation and the acceleration signal of the vibration response to obtain the time domain response signal.

[0030] Step S3: Extract nonlinear acoustic features from the response signal. The nonlinear acoustic features include at least one of higher harmonic features and resonant frequency shift features. Perform spectral analysis on the response signal, calculate the ratio of the second harmonic amplitude to the corresponding fundamental frequency amplitude in its spectrum, or calculate the normalized measure of the spectral peak at the second harmonic frequency point generated by the coupling of the fundamental frequency in the bispectrum, and use the calculation results as higher harmonic characteristics.

[0031] The steps for calculating the normalized measure of the spectral peak at the second harmonic frequency in a bispectral system further include: defining the nonlinear intrinsic parameter β. bis for: Where B(f1,f2) is the bispectral density of the response signal, f0 is the fundamental frequency of the dominant resonance mode, and the denominator is all frequency points (f0,f0) on the diagonal of the bispectral density. i ,f i The average value of the amplitude, where N is the number of frequency points; The calculated β bis The value is used as the characteristic of the higher harmonics.

[0032] By performing time-frequency analysis on the response signal, the instantaneous frequency function and instantaneous amplitude function of the dominant resonance mode are extracted; The nonlinear softening relationship in which the instantaneous frequency monotonically decreases as the instantaneous amplitude increases was identified; By fitting the slope of this relationship, a nonlinear frequency shift coefficient is obtained and used as a characteristic of the resonant frequency shift.

[0033] Step S4: Input the extracted nonlinear acoustic features into a calibrated regression model and output a quantitative index to characterize the degree of delamination damage at the steel-concrete interface in concrete poles.

[0034] The regression model is a support vector regression model or a Gaussian process regression model. The model is pre-trained based on a calibration database, which contains corresponding data pairs of nonlinear acoustic features and peeling damage indices that have been pre-established through finite element simulation and / or physical accelerated corrosion tests under known different peeling conditions.

[0035] Peeling damage indicators include the percentage of peeled area at the steel-concrete interface, the thickness of the peel gap, or the quantitative classification of the degree of filling of corrosion products.

[0036] Specifically, a reinforced concrete pole model containing a "contact interface" was established using finite element software such as ABAQUS / Explicit, and different sizes of peeling areas (such as circumferential peeling percentage and gap thickness) were set at the interface.

[0037] The simulation simulates impact excitation, extracts the response, and calculates the aforementioned nonlinear parameters β and α. nl .

[0038] Based on accelerated corrosion tests on actual objects, a calibration database of data pairs (damage parameters, nonlinear parameters) was established.

[0039] On-site assessment process: Sensors were deployed near the suspected area of ​​the utility pole, and impacts were applied according to standard procedures.

[0040] Run the algorithm package (bispectral analysis, frequency shift tracking) to calculate β. bis and α nl .

[0041] Input these two parameters into a pre-trained Support Vector Regression (SVR) or Gaussian Process Regression (GPR) model (trained from a calibration database) to directly output an estimate of the stripping area and a confidence interval.

[0042] Detection example: The #045 cone-shaped concrete pole of a certain 10kV overhead line is 10.5m high above ground and has a designed burial depth of 2.0m. It has been in service for 18 years.

[0043] At a height of 0.5m above the ground on the utility pole, select two locations along the same contour line to install acceleration sensors #1 and #2 respectively: Accelerometer #1 is rigidly attached to the side of the pole using a magnetic base, with its sensing axis radially positioned, and is used to receive vibration responses. Accelerometer #2 is installed 0.6m below #1 on the same busbar and is used for wave velocity calibration.

[0044] Using a nylon hammer, strike the side wall of the pole near sensor #1 with moderate force to simultaneously acquire force signal F1(t) and acceleration response a1(t), with a sampling rate of 200kHz and a recording duration of 500ms.

[0045] Replace the hammer head with a steel hammer and apply a second excitation at the same impact point with a greater impact force, simultaneously collecting F2(t) and a2(t).

[0046] Using the dual-channel time-difference method, based on the first wave arrival time difference Δt = 0.198 ms between the two sensors and the distance Ls = 0.6 m, the actual elastic wave velocity of the pole is calculated as: V = 0.6 / 0.198 × 10⁻⁶. -3 =3030 m / s The acceleration response a2(t) under high-level excitation is the main object of analysis: A synchronous squeezed wavelet transform (SWT) is performed on a2(t) to obtain a high-resolution time spectrum. The instantaneous frequency curve f(t) and instantaneous amplitude envelope A(t) of the first-order longitudinal resonance mode are automatically extracted from the time spectrum.

[0047] By fitting the relationship between f(t) and A(t), we obtain: f(t)≈852.3-1.87×10 -3 ·A(t) Hz Nonlinear frequency offset coefficient α nl =-1.87×10 -3 Hz / g, its absolute value is significantly greater than the reference value for a healthy utility pole (approximately -0.15 × 10⁻⁶). -3 (Hz / g), indicating the presence of significant non-classical nonlinear elastic behavior.

[0048] Calculate the bispectral density of a2(t). A significant second-harmonic coupling peak appears at the fundamental frequency f0 = 852 Hz. Calculate the nonlinear intrinsic parameters: β bis =12.8 Reference value β for healthy utility poles bis <2.0 Calculate the second harmonic ratio under low-level and high-level excitation respectively. Low-level incentives: β low =4.2×10 -3 High-level incentives: βhigh =1.6×10 -3 The β value decreases significantly with increasing excitation level. This trend confirms that the nonlinearity originates from the nonclassical nonlinear elastic effect of the "breathing crack" type, thus eliminating the interference of inherent nonlinearity of the instrument or material.

[0049] A Hadamard product operation was performed on the dual-channel signal to obtain a composite signal with enhanced uplink reflected wave. Through multi-sample statistics, a stable uplink reflected wave arrival time difference of ΔT = 1.32 ms was identified.

[0050] The three nonlinear eigenvalues ​​(α) extracted nl =-1.87×10 -3 β bis =12.8, Δβ=2.6×10 -3 Input a pre-calibrated support vector regression (SVR) model.

[0051] Model output: Percentage of area of ​​delamination at the steel-concrete interface: approximately 18.6% 95% confidence interval: [15.2%, 22.1%] Damage level: Moderate peeling Based on the wave velocity V = 3030 m / s and the time difference of arrival of the reflected wave ΔT = 1.32 ms, calculate the distance from the reflecting interface to the sensor above: D = 3030 × 1.32 × 10 -3 / 2=2.00 m The sensor is installed at a height H = 0.5 m, therefore the pole burial depth is: L = DH = 2.00 - 0.5 = 1.50 m <Example 2> A non-destructive testing system for pole burial depth based on nonlinear acoustic characteristics, comprising: An excitation module is used to apply a broadband transient impact excitation to the sidewall of the concrete pole to induce a vibration response in the pole; and The sensing and acquisition module includes a force sensor for measuring the impact excitation force, an accelerometer for measuring the vibration response acceleration, and a high-speed data acquisition unit for simultaneously acquiring the signals of both; and The processor is configured to perform the steps of the method described in Example 1 to process the acquired signals and to achieve a quantitative output of the peel damage index.

[0052] <Example 3> This embodiment also provides an electronic device suitable for non-destructive measurement of pole burial depth, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the method described in <Embodiment 1>.

[0053] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0054] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A non-destructive testing method for the burial depth of utility poles based on nonlinear acoustic characteristics, characterized in that, Includes the following steps: Step S1: Apply a broadband transient impact excitation to the sidewall of the concrete pole to induce a vibration response in the pole that includes at least one dominant resonant mode; Step S2: Synchronously acquire the force signal of the impact excitation and the acceleration signal of the vibration response to obtain the time-domain response signal; Step S3: Extract nonlinear acoustic features from the response signal. The nonlinear acoustic features include at least one of higher harmonic features and resonant frequency shift features. Step S4: Input the extracted nonlinear acoustic features into a calibrated regression model and output a quantitative index to characterize the degree of delamination damage at the steel-concrete interface in concrete poles.

2. The non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics as described in claim 1, characterized in that, Step S1 further includes: applying the broadband transient impact excitation at least twice at different excitation levels to the same measuring point by replacing the excitation hammer with one of different materials or changing the excitation intensity, so as to obtain the response signal under different excitation levels.

3. The non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics as described in claim 2, characterized in that, Calculate the nonlinear coefficient β, and by analyzing the trend of β changing with the excitation level, distinguish between classical and non-classical nonlinear elastic behavior: Among them, A 2f Let A be the second harmonic amplitude of the response signal under different excitation levels. f For the corresponding base frequency Amplitude.

4. The non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics as described in claim 1, characterized in that, Step S3 specifically includes: performing spectral analysis on the response signal, calculating the ratio of the second harmonic amplitude to the corresponding fundamental frequency amplitude in its spectrum, or calculating the normalized measure of the spectral peak at the second harmonic frequency point generated by the coupling of the fundamental frequency and using the calculation result as a higher harmonic feature.

5. The non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics as described in claim 4, characterized in that, The steps for calculating the normalized measure of the spectral peak at the second harmonic frequency in a bispectral system further include: defining the nonlinear intrinsic parameter β. bis for: Where B(f1,f2) is the bispectral density of the response signal, f0 is the fundamental frequency of the dominant resonance mode, and the denominator is all frequency points (f0,f0) on the diagonal of the bispectral density. i ,f i The average value of the amplitude, where N is the number of frequency points; The calculated β bis The value is used as the characteristic of the higher harmonics.

6. The non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics as described in claim 1, characterized in that, Step S3 specifically includes: By performing time-frequency analysis on the response signal, the instantaneous frequency function and instantaneous amplitude function of the dominant resonance mode are extracted; The nonlinear softening relationship in which the instantaneous frequency monotonically decreases as the instantaneous amplitude increases was identified; By fitting the slope of this relationship, a nonlinear frequency shift coefficient is obtained and used as a characteristic of the resonant frequency shift.

7. The non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics as described in claim 1, characterized in that: The regression model in step S4 is a support vector regression model or a Gaussian process regression model. This model is pre-trained based on a calibration database. The calibration database contains corresponding data pairs of nonlinear acoustic features and peeling damage indices that have been pre-established through finite element simulation and / or physical accelerated corrosion tests under known different peeling conditions.

8. The non-destructive testing method for pole burial depth based on nonlinear acoustic characteristics as described in claim 7, characterized in that: The peeling damage indicators include the percentage of peeled area at the steel-concrete interface, the thickness of the peeling gap, or the quantitative classification of the degree of filling of corrosion products.

9. A non-destructive testing system for pole burial depth based on nonlinear acoustic characteristics, characterized in that, include: An excitation module is used to apply a broadband transient impact excitation to the sidewall of the concrete pole to induce a vibration response in the pole. as well as The sensing and acquisition module includes a force sensor for measuring the impact excitation force, an accelerometer for measuring the vibration response acceleration, and a high-speed data acquisition unit for simultaneously acquiring the signals of both. as well as The processor is configured to perform the steps of the method as described in any one of claims 1 to 8 to process the acquired signal and to achieve a quantitative output of the peel damage index.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 8.

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