Guided wave monitoring method and device for corrosion of buried anchor rod of electric power iron tower and medium

Abstract

The invention discloses an electric power iron tower buried anchor rod corrosion guided wave monitoring method and device and a medium, and belongs to the technical field of electric power facility state monitoring and nondestructive testing. According to the method, ultrasonic guided waves in a longitudinal mode and a torsional mode are excited and received at the exposed end of an anchor rod, and the propagation time of echoes reflected from the buried end of the anchor rod is accurately extracted; calculating wave velocities V1 and V2 and a wave velocity ratio R of the two modes; the influence of soil environment change on V1 and V2 is consistent, so that the wave velocity ratio R is kept stable; the rigidity and mass distribution of the anchor rod can be differentially changed by the corrosion defect, so that the R value is specifically changed; according to the method, accurate and quantitative diagnosis and early warning of the corrosion state of the anchor rod can be achieved by establishing the healthy reference wave velocity ratio Ri and the diagnosis threshold value delta based on the statistical confidence interval and monitoring whether the subsequent wave velocity ratio Rnew value exceeds the threshold value or not, and the technical bottleneck that a traditional single-mode monitoring method is greatly interfered by the environment is effectively overcome.

Description

Technical Field

[0001] This invention relates to a guided wave monitoring method, device, and medium for corrosion monitoring of buried anchor bolts of power transmission towers, belonging to the field of power facility condition monitoring and non-destructive testing technology. Background Technology

[0002] As a critical supporting structure for power transmission networks, the stability of power transmission towers directly impacts the safe operation of the entire power grid. The stability of these towers largely depends on the integrity of the buried anchors in their foundations. These anchors, operating in complex underground soil environments, are inevitably affected by groundwater, electrolytes, stray currents, and other factors, leading to electrochemical corrosion and stress corrosion. This results in a reduction in their effective cross-sectional area, degradation of their mechanical properties, and a significant decrease in their load-bearing capacity. In severe cases, corrosion can cause anchor breakage, triggering catastrophic accidents such as tower tilting or even overturning, causing enormous economic losses and social impact. Therefore, effective corrosion monitoring of buried anchors is an urgent requirement for achieving predictive maintenance of power facilities and ensuring the safe and stable operation of the power grid.

[0003] Currently, the detection and monitoring of buried anchor bolts mainly rely on the following methods: Excavation inspection: This is the most traditional and direct method, involving direct excavation to inspect the surface corrosion of the anchor bolt. While intuitive, this method is costly, destructive, inefficient, and only allows for sampling inspections, failing to achieve large-scale surveys and long-term online monitoring, thus failing to meet the operation and maintenance requirements of modern smart grids. Electrochemical detection methods: such as polarization resistance method and electrochemical impedance spectroscopy. These methods assess the instantaneous corrosion rate by measuring the electrochemical parameters of the anchor bolt / soil system. However, they only reflect point-like information at the moment of detection, making it difficult to assess the cumulative damage and overall bearing capacity. Furthermore, their measurement results are significantly affected by environmental factors such as soil resistivity, moisture content, and oxygen content, resulting in insufficient stability and reliability, making long-term, stable quantitative assessment difficult. Non-destructive testing methods based on ultrasonic guided waves: Due to its long propagation distance, high detection efficiency, and sensitivity to cross-sectional changes, ultrasonic guided wave technology is considered an ideal means of monitoring rod-shaped components such as anchor bolts. However, most existing guided wave monitoring technologies rely on the absolute value of wave velocity or signal attenuation characteristics of a single mode (usually the longitudinal mode L(0,1)) for judgment. Extensive research and engineering practice show that changes in soil temperature and humidity significantly alter the propagation speed of guided waves. The resulting seasonal fluctuations in wave velocity (up to ±3%-5%) are often much greater than the minor wave velocity changes caused by early corrosion (typically 1%-2%). This extremely low signal-to-noise ratio makes the judgment method based on a single absolute wave velocity highly susceptible to false alarms and missed alarms during seasonal changes or weather variations, making reliability difficult to guarantee and severely limiting the widespread application of this technology in engineering fields.

[0004] Therefore, developing a method for monitoring the corrosion of buried anchor bolts that can effectively overcome environmental interference, is sensitive to early corrosion, provides reliable results, and is easy to implement has become a pressing technical challenge in this field. Summary of the Invention

[0005] In order to address the problems and needs in the background technology, the purpose of this invention is to provide a guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers based on dual-mode wave velocity ratio, so as to solve the defects of the existing buried anchor bolt detection technology.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a method for monitoring corrosion of buried anchor bolts of power transmission towers using guided waves, comprising: Obtain data on the burial depth of the anchor bolts and the installation height of the transducers; Based on the buried depth and installation height data, the total round-trip propagation path length of the guided wave in the anchor bolt is calculated. The longitudinal mode echo signal sequence and the torsional mode echo signal sequence are obtained by sequentially transmitting excitation signals of preset frequencies to the longitudinal mode transducer group and the torsional mode transducer group coupled to the exposed end of the anchor bolt, and the signals reflected back from the buried end of the anchor bolt. The acquired longitudinal mode echo signal sequence and torsional mode echo signal sequence are preprocessed respectively, and the propagation time of the first arrival echo of the longitudinal mode and the propagation time of the first arrival echo of the torsional mode are extracted based on the preprocessed signals and the excitation signal. Based on the total round-trip propagation path length, the propagation time of the first arrival echo of the longitudinal mode, and the propagation time of the first arrival echo of the torsional mode, the guided wave velocity of the longitudinal mode and the guided wave velocity of the torsional mode are calculated respectively. The bimodal wave velocity ratio is calculated based on the calculated longitudinal mode wave velocity and the torsional mode wave velocity. Obtain the mean wave velocity ratio of the healthy baseline and the diagnostic threshold, which are determined in advance based on multiple measurements of healthy anchors; The calculated dual-mode wave velocity ratio is compared with the diagnostic threshold, and the corrosion status of the anchor bolt is determined based on the comparison result.

[0007] Furthermore, the preprocessing of the acquired longitudinal mode echo signal sequence and torsional mode echo signal sequence includes: The echo signal sequence is subjected to bandpass filtering. The filtered signal is subjected to wavelet thresholding denoising. The Symlets wavelet basis is used to decompose the signal into 5 levels, and the high-frequency coefficients obtained from the decomposition are subjected to soft thresholding.

[0008] Furthermore, the extraction of the propagation time of the longitudinal mode first-arrival echo and the propagation time of the torsional mode first-arrival echo based on the preprocessed signal and the excitation signal includes: A time delay estimation method based on cross-correlation function is adopted, and the cross-correlation function between the excitation signal and the preprocessed longitudinal mode echo signal and torsional mode echo signal is calculated, respectively, with the excitation signal as the reference signal. The peak position is determined from the cross-correlation function, and the propagation time t1 of the first arrival echo of the longitudinal mode and the propagation time t2 of the first arrival echo of the torsional mode are extracted based on the peak position.

[0009] Furthermore, the calculation of the longitudinal mode guided wave velocity and the torsional mode guided wave velocity based on the total round-trip propagation path length, the propagation time of the first arrival echo of the longitudinal mode, and the propagation time of the first arrival echo of the torsional mode includes: Calculate the longitudinal modal guided wave velocity V1 = S / t1, where S is the total round-trip propagation path length; Calculate the wave velocity of the torsional mode guided wave V2 = S / t2.

[0010] Furthermore, the bimodal wave velocity ratio is calculated based on the calculated longitudinal mode wave velocity and the torsional mode wave velocity, using the formula: R = V1 / V2.

[0011] Furthermore, obtaining the mean wave velocity ratio of the healthy baseline and the diagnostic threshold, pre-determined based on multiple measurements of healthy anchors, includes: Under the condition of a healthy anchor bolt, N independent measurements are performed to obtain N healthy wave velocity ratio measurements R. i Where i = 1, 2, ..., N, N > 10; Calculate the mean μ of the N health wave velocity ratio measurements. R With standard deviation σ R ; According to the mean μ R With standard deviation σ R Set the diagnostic threshold δ = μ R +3×σ R .

[0012] Furthermore, the step of comparing the calculated dual-mode wave velocity ratio with the diagnostic threshold and determining the corrosion state of the anchor bolt based on the comparison result includes: Calculate the measured wave velocity ratio R new Based on the diagnostic threshold δ, a state judgment is made: if R new If R ≤ δ, then the anchor bolt is considered to be in good condition; if R new If the value is greater than δ, then the anchor rod is determined to be corroded.

[0013] Furthermore, the longitudinal mode transducer group and the torsional mode transducer group coupled to the exposed end of the anchor bolt sequentially transmit excitation signals of a preset frequency, wherein the excitation signal is a narrowband sinusoidal pulse signal modulated by a Hanning window, and its frequency range is 20 kHz ~ 300 kHz.

[0014] Secondly, the present invention provides a guided wave monitoring device for corrosion of buried anchor bolts of power transmission towers, used to implement the guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers as described in any of the preceding claims, comprising: The first acquisition module is used to acquire data on the burial depth of the anchor bolt and the installation height of the transducer. The first calculation module is used to calculate the total round-trip propagation path length of the guided wave in the anchor rod based on the buried depth and installation height data. The second acquisition module is used to acquire the longitudinal mode echo signal sequence and the torsional mode echo signal sequence reflected back from the buried end of the anchor by sequentially transmitting excitation signals of preset frequencies to the longitudinal mode transducer group and the torsional mode transducer group coupled to the exposed end of the anchor bolt. The preprocessing and extraction module is used to preprocess the acquired longitudinal mode echo signal sequence and torsional mode echo signal sequence respectively, and extract the propagation time of the first arrival echo of the longitudinal mode and the propagation time of the first arrival echo of the torsional mode based on the preprocessed signals and the excitation signal. The second calculation module is used to calculate the longitudinal mode guided wave velocity and the torsional mode guided wave velocity based on the total round-trip propagation path length, the propagation time of the first arrival echo of the longitudinal mode, and the propagation time of the first arrival echo of the torsional mode. The third calculation module is used to calculate the dual-mode wave velocity ratio based on the calculated longitudinal mode guided wave velocity and the torsional mode guided wave velocity. The third acquisition module is used to acquire the average wave velocity ratio of the health baseline and the diagnostic threshold determined in advance based on multiple measurements of the healthy anchor. The judgment module is used to compare the calculated dual-mode wave velocity ratio with the diagnostic threshold, and determine the corrosion status of the anchor rod based on the comparison result.

[0015] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the methods described above.

[0016] Fourthly, the present invention provides an electronic device, comprising: Memory, used to store computer programs / instructions; A processor for executing the computer program / instructions to implement the steps of any of the methods described above.

[0017] Fifthly, the present invention provides a computer program product, including a computer program / instructions that, when executed by a processor, implement the steps of any of the methods described above.

[0018] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. This invention provides a method, device, and medium for monitoring corrosion of buried anchor bolts in power transmission towers using guided waves. This is achieved by establishing a healthy baseline wave velocity ratio R based on a statistical confidence interval. i And the diagnostic threshold δ, and monitor the subsequent wave velocity ratio R new By determining whether the value exceeds the threshold, accurate and quantitative diagnosis and early warning of anchor bolt corrosion status can be achieved, effectively overcoming the technical bottleneck of traditional single-mode monitoring methods being greatly affected by environmental interference.

[0019] 2. This invention fundamentally offsets the impact of major environmental disturbances such as soil temperature and humidity on monitoring results by using the intrinsic invariant wave velocity ratio. Through the differentiated influence of corrosion on the wave velocities of the two modes, the change in the wave velocity ratio R is more significant and specific than the change in wave velocity of any single mode, enabling sensitive capture of early corrosion signals. Based on statistical theory, this invention sets thresholds, ensuring objective and repeatable diagnostic results. Combined with trend prediction, it achieves an upgrade from "condition monitoring" to "predictive maintenance." Attached Figure Description

[0020] Figure 1 This is a flowchart of a guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers provided in an embodiment of the present invention. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0022] Example 1: This example introduces a guided wave monitoring method for corrosion of buried anchor bolts on power transmission towers, including: Obtain data on the burial depth of the anchor bolts and the installation height of the transducers; Based on the buried depth and installation height data, the total round-trip propagation path length of the guided wave in the anchor bolt is calculated. The longitudinal mode echo signal sequence and the torsional mode echo signal sequence are obtained by sequentially transmitting excitation signals of preset frequencies to the longitudinal mode transducer group and the torsional mode transducer group coupled to the exposed end of the anchor bolt, and the signals are reflected back from the buried end of the anchor bolt. The acquired longitudinal mode echo signal sequence and torsional mode echo signal sequence are preprocessed respectively, and the propagation time of the first arrival echo of the longitudinal mode and the propagation time of the first arrival echo of the torsional mode are extracted based on the preprocessed signals and the excitation signal. Based on the total round-trip propagation path length, the propagation time of the first arrival echo of the longitudinal mode, and the propagation time of the first arrival echo of the torsional mode, the guided wave velocity of the longitudinal mode and the guided wave velocity of the torsional mode are calculated respectively. The bimodal wave velocity ratio is calculated based on the calculated longitudinal mode wave velocity and the torsional mode wave velocity. Obtain the mean wave velocity ratio of the healthy baseline and the diagnostic threshold, which are determined in advance based on multiple measurements of healthy anchors; The calculated dual-mode wave velocity ratio is compared with the diagnostic threshold, and the corrosion status of the anchor bolt is determined based on the comparison result.

[0023] like Figure 1 As shown in this embodiment, the method for monitoring corrosion of buried anchor bolts on power transmission towers using guided waves involves the following steps in its application: At the exposed end of the buried anchor rod of the power tower, a dual-mode guided wave transducer array is circumferentially coupled and installed, which includes a longitudinal mode piezoelectric transducer group and a torsional mode piezoelectric transducer group. The burial depth h of the anchor rod and the height x of the transducer installation from the ground are accurately measured. Narrowband sinusoidal pulse excitation signals modulated by the Hanning window are sequentially transmitted to the longitudinal and torsional mode transducer groups. The frequency of the excitation signal is selected within the non-sensitive range of the preset guided wave dispersion curve. The echo signal sequences reflected back from the buried end of the anchor bolt and received by the longitudinal and torsional mode transducer groups are collected respectively. The frequency range of the excitation signal is 20 kHz to 300 kHz, preferably 30 kHz to 150 kHz.

[0024] The acquired raw echo signals were sequentially subjected to bandpass filtering and noise suppression. A time delay estimation method based on cross-correlation function was used, with the excitation signal as a reference, to extract the precise propagation times t1 and t2 of the first echo packet from the processed L-mode and T-mode echo signals, respectively. The noise suppression process employed wavelet thresholding, using Symlets wavelet basis to decompose the signal into 5 levels and applying soft thresholding to the high-frequency coefficients.

[0025] Based on the physical path of guided wave propagation, determine the total round-trip propagation path length S = 2 × (h + x); calculate the measured wave velocity V1 = S / t1 of the longitudinal mode guided wave and the measured wave velocity V2 = S / t2 of the torsional mode guided wave respectively; then, calculate the core monitoring index—the dual-mode wave velocity ratio R = V1 / V2; During the initial installation of the anchor bolt or when the absence of corrosion is confirmed, N independent measurements are performed, where N>10, to obtain N wave velocity ratio measurements R under healthy conditions. i (i=1, 2, ..., N); Calculate the mean μ of this data series.R And calculate its standard deviation σ. R Set the diagnostic threshold δ = μ R +3×σ R In subsequent monitoring, the measured wave velocity ratio R was calculated. new Based on the diagnostic threshold δ, a state judgment is made: if R new If R ≤ δ, then the anchor bolt is considered to be in good condition; if R new If the value is greater than δ, then the anchor rod is determined to be corroded.

[0026] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0027] Step (a): Sensor deployment and system calibration Operation: Upon arrival at the site, the inspection personnel inspected anchor bolt number T18-A3 and cleaned rust and dirt from the exposed end face of the target anchor bolt. The magnetic dual-mode guided wave transducer array of the portable device was tightly coupled to the clean end face. Referring to the as-built drawings of the tower and combining them with on-site measurements, the burial depth of the anchor bolt was confirmed to be h = 3.2 meters, and the transducer installation height to be x = 1.0 meter.

[0028] Step (b): Dual-mode guided wave excitation and signal acquisition Operation: The equipment operator sets the excitation signal parameters on the control software: center frequency 100 kHz, 5-cycle Hanning window modulated sinusoidal pulse. The automatic detection process is initiated, and the equipment sequentially transmits excitation signals to the L-mode and T-mode transducer groups, simultaneously acquiring and storing the echo signal sequences from both channels.

[0029] Step (c): Echo signal preprocessing and accurate propagation time extraction Operation: The device's built-in algorithm automatically performs a (100±25) kHz bandpass filter on the original echo signal, followed by soft-threshold wavelet denoising using a 5-level decomposition based on the Symlets wavelet basis. The signal-to-noise ratio of the processed signal is significantly improved. Subsequently, the generalized cross-correlation function (GCC-PHAT) method is used to accurately extract the first-arrival echo time t1 = 1.610 ms for the L mode and the first-arrival echo time t2 = 2.608 ms for the T mode.

[0030] Step (d): Calculation of wave speed and wave speed ratio Operation: The device automatically calculates the propagation path S = 2 × (3.2 + 1.0) = 8.4 meters.

[0031] The L-mode wave velocity V1 is calculated as 8.4 / 1.610×10⁻³ = 5217 m / s.

[0032] The wave velocity of mode T is calculated as V2 = 8.4 / 2.608×10⁻³ = 3221 m / s.

[0033] Calculate the core indicator – wave speed ratio R new = V1 / V2 = 5217 / 3221 = 1.620.

[0034] Step (e): Establishment of health benchmarks and diagnosis of corrosion status Prior to this inspection, a health baseline had been established on healthy samples of similar anchor bolts along the same line (N=20 measurements): mean μ R = 1.605, standard deviation σ R = 0.004. Diagnostic threshold δ = 1.605 + 3 × 0.004 = 1.617. The measured value R... new = 1.620 is compared with the threshold δ = 1.617, since R new = 1.620 > δ = 1.617, therefore it is determined that the tested anchor rod "T18-A3" is corroded. Excavation verification of the anchor rod revealed a significant localized corrosion pit at a depth of 1.8 meters, consistent with the diagnosis.

[0035] The main beneficial effects of this embodiment are: 1. Excellent anti-interference ability: By using the inherent invariant wave velocity ratio, the influence of major environmental interference factors such as soil temperature and humidity on the monitoring results is fundamentally offset.

[0036] 2. High sensitivity and early warning: The differential effect of corrosion on the wave velocity of the two modes makes the change in wave velocity ratio R more significant and specific than the change in wave velocity of any single mode, which can sensitively capture early corrosion signals.

[0037] 3. Quantification and Intelligence: Thresholds are set based on statistical theory, ensuring objective and repeatable diagnostic results. Combined with trend prediction, this achieves an upgrade from "condition monitoring" to "predictive maintenance."

[0038] Example 2: This example provides a guided wave monitoring device for corrosion of buried anchor bolts on power transmission towers, comprising: The first acquisition module is used to acquire data on the burial depth of the anchor bolt and the installation height of the transducer. The first calculation module is used to calculate the total round-trip propagation path length of the guided wave in the anchor rod based on the buried depth and installation height data. The second acquisition module is used to acquire the longitudinal mode echo signal sequence and the torsional mode echo signal sequence reflected back from the buried end of the anchor by sequentially transmitting excitation signals of preset frequencies to the longitudinal mode transducer group and the torsional mode transducer group coupled to the exposed end of the anchor bolt. The preprocessing and extraction module is used to preprocess the acquired longitudinal mode echo signal sequence and torsional mode echo signal sequence respectively, and extract the propagation time of the first arrival echo of the longitudinal mode and the propagation time of the first arrival echo of the torsional mode based on the preprocessed signals and the excitation signal. The second calculation module is used to calculate the longitudinal mode guided wave velocity and the torsional mode guided wave velocity based on the total round-trip propagation path length, the propagation time of the first arrival echo of the longitudinal mode, and the propagation time of the first arrival echo of the torsional mode. The third calculation module is used to calculate the dual-mode wave velocity ratio based on the calculated longitudinal mode guided wave velocity and the torsional mode guided wave velocity. The third acquisition module is used to acquire the average wave velocity ratio of the health baseline and the diagnostic threshold determined in advance based on multiple measurements of the healthy anchor. The judgment module is used to compare the calculated dual-mode wave velocity ratio with the diagnostic threshold, and determine the corrosion status of the anchor rod based on the comparison result.

[0039] The specific functions of each module described above are explained in the relevant content of the method in Embodiment 1, and will not be repeated here.

[0040] Example 3: This example provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the methods described in Example 1.

[0041] Example 4: This example provides an electronic device, including: Memory, used to store computer programs / instructions; A processor for executing the computer program / instructions to implement the steps of any of the methods described in Embodiment 1.

[0042] Example 5: This example provides a computer program product, including a computer program / instructions, which, when executed by a processor, implement the steps of the method described in any one of Examples 1.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

[0044] Those skilled in the art will understand that embodiments of this disclosure can be provided as methods, systems, or computer program products. Therefore, this disclosure can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this disclosure can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0045] This disclosure is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0046] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0047] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure and not to limit its protection scope. Although this disclosure has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading this disclosure, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims.

Claims

1. A guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers, characterized in that, include: Obtain data on the burial depth of the anchor bolts and the installation height of the transducers; Based on the buried depth and installation height data, the total round-trip propagation path length of the guided wave in the anchor bolt is calculated. The longitudinal mode echo signal sequence and the torsional mode echo signal sequence are obtained by sequentially transmitting excitation signals of preset frequencies to the longitudinal mode transducer group and the torsional mode transducer group coupled to the exposed end of the anchor bolt, and the signals are reflected back from the buried end of the anchor bolt. The acquired longitudinal mode echo signal sequence and torsional mode echo signal sequence are preprocessed respectively, and the propagation time of the first arrival echo of the longitudinal mode and the propagation time of the first arrival echo of the torsional mode are extracted based on the preprocessed signals and the excitation signal. Based on the total round-trip propagation path length, the propagation time of the first arrival echo of the longitudinal mode, and the propagation time of the first arrival echo of the torsional mode, the guided wave velocity of the longitudinal mode and the guided wave velocity of the torsional mode are calculated respectively. The bimodal wave velocity ratio is calculated based on the calculated longitudinal mode wave velocity and the torsional mode wave velocity. Obtain the mean wave velocity ratio of the healthy baseline and the diagnostic threshold, which are determined in advance based on multiple measurements of healthy anchors; The calculated dual-mode wave velocity ratio is compared with the diagnostic threshold, and the corrosion status of the anchor bolt is determined based on the comparison result.

2. The guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers according to claim 1, characterized in that, The preprocessing of the acquired longitudinal mode echo signal sequence and torsional mode echo signal sequence includes: The echo signal sequence is subjected to bandpass filtering. The filtered signal is subjected to wavelet thresholding denoising. The Symlets wavelet basis is used to decompose the signal into 5 levels, and the high-frequency coefficients obtained from the decomposition are subjected to soft thresholding.

3. The guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers according to claim 1, characterized in that, The extraction of the propagation time of the first arrival echo of the longitudinal mode and the propagation time of the first arrival echo of the torsional mode based on the preprocessed signal and the excitation signal includes: A time delay estimation method based on cross-correlation function is adopted, and the cross-correlation function between the excitation signal and the preprocessed longitudinal mode echo signal and torsional mode echo signal is calculated, respectively, with the excitation signal as the reference signal. The peak position is determined from the cross-correlation function, and the propagation time t1 of the first arrival echo of the longitudinal mode and the propagation time t2 of the first arrival echo of the torsional mode are extracted based on the peak position.

4. The guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers according to claim 1, characterized in that, The calculation of the longitudinal mode guided wave velocity and the torsional mode guided wave velocity based on the total round-trip propagation path length, the propagation time of the first arrival echo of the longitudinal mode, and the propagation time of the first arrival echo of the torsional mode includes: Calculate the longitudinal modal guided wave velocity V1 = S / t1, where S is the total round-trip propagation path length; Calculate the wave velocity of the torsional mode guided wave V2 = S / t2.

5. The guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers according to claim 1, characterized in that, The bimodal wave velocity ratio is calculated based on the calculated longitudinal mode wave velocity and the torsional mode wave velocity, using the formula: R = V1 / V2.

6. The guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers according to claim 1, characterized in that, The process of obtaining the mean wave velocity ratio of the healthy baseline and the diagnostic threshold, which are pre-determined based on multiple measurements of healthy anchors, includes: Under the condition of a healthy anchor bolt, N independent measurements are performed to obtain N healthy wave velocity ratio measurements R. i , where i = 1, 2, ..., N, N > 10; Calculate the mean μ of the N health wave velocity ratio measurements. R With standard deviation σ R ; According to the mean μ R With standard deviation σ R Set the diagnostic threshold δ = μ R +3×σ R .

7. The guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers according to claim 6, characterized in that, The step of comparing the calculated dual-mode wave velocity ratio with the diagnostic threshold and determining the corrosion state of the anchor bolt based on the comparison result includes: Calculate the measured wave velocity ratio R new Based on the diagnostic threshold δ, a state judgment is made: if R new If R ≤ δ, then the anchor bolt is considered to be in good condition; if R new If the value is greater than δ, then the anchor rod is determined to be corroded.

8. The guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers according to claim 1, characterized in that, The longitudinal mode transducer group and the torsional mode transducer group coupled to the exposed end of the anchor bolt sequentially transmit excitation signals of a preset frequency, wherein the excitation signal is a narrowband sinusoidal pulse signal modulated by a Hanning window, and its frequency range is 20 kHz ~ 300 kHz.

9. A guided wave monitoring device for corrosion of buried anchor bolts of power transmission towers, used to implement the guided wave monitoring method for corrosion of buried anchor bolts of power transmission towers as described in any one of claims 1-8, characterized in that, include: The first acquisition module is used to acquire data on the burial depth of the anchor bolt and the installation height of the transducer. The first calculation module is used to calculate the total round-trip propagation path length of the guided wave in the anchor rod based on the buried depth and installation height data. The second acquisition module is used to acquire the longitudinal mode echo signal sequence and the torsional mode echo signal sequence reflected back from the buried end of the anchor by sequentially transmitting excitation signals of preset frequencies to the longitudinal mode transducer group and the torsional mode transducer group coupled to the exposed end of the anchor bolt. The preprocessing and extraction module is used to preprocess the acquired longitudinal mode echo signal sequence and torsional mode echo signal sequence respectively, and extract the propagation time of the first arrival echo of the longitudinal mode and the propagation time of the first arrival echo of the torsional mode based on the preprocessed signals and the excitation signal. The second calculation module is used to calculate the longitudinal mode guided wave velocity and the torsional mode guided wave velocity based on the total round-trip propagation path length, the propagation time of the first arrival echo of the longitudinal mode, and the propagation time of the first arrival echo of the torsional mode. The third calculation module is used to calculate the dual-mode wave velocity ratio based on the calculated longitudinal mode guided wave velocity and the torsional mode guided wave velocity. The third acquisition module is used to acquire the average wave velocity ratio of the health baseline and the diagnostic threshold determined in advance based on multiple measurements of the healthy anchor. The judgment module is used to compare the calculated dual-mode wave velocity ratio with the diagnostic threshold, and determine the corrosion status of the anchor rod based on the comparison result.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When executed by a processor, the computer program implements the steps of the method according to any one of claims 1-8.

Images