Three-dimensional imaging device for power transmission tower base pipe wall and corrosion state evaluation method thereof

Abstract

The present application relates to a kind of transmission tower base pipe wall three-dimensional imaging device and its corrosion state evaluation method, belong to nondestructive testing technical field.The method includes: S1: the ultrasonic array probe in three-dimensional imaging device is rotated around tower base horizontally for a week, obtains pipe wall longitudinal thickness information;S2: according to the angle information and horizontal radial data of ultrasonic array probe, the external contour of pipe wall is constructed;S3: according to the angle information and pipe wall thickness information of ultrasonic array probe, the internal contour of pipe wall is constructed in combination with the external contour information of pipe wall;S4: suspected corrosion point in pipe wall internal contour is confirmed by multi-angle acoustic beam;S5: on the basis of obtaining the internal and external contour of pipe wall, the three-dimensional imaging result of tower pipe wall is constructed;Or according to three-dimensional imaging result, the mechanical strength of pipe wall and the corrosion degree of inner pipe wall are evaluated.The present application breaks through traditional detection dimension, realizes high-precision, high-definition visual three-dimensional fine evaluation.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology and relates to a three-dimensional imaging device for the pipe wall of a power transmission tower base and a method for assessing its corrosion status. Background Technology

[0002] In recent years, steel pipe towers have been widely used in power grid transmission lines of different voltage levels due to their advantages such as high cross-sectional stiffness and good cross-sectional stress characteristics. Compared with traditional angle steel structures, steel pipe tower structures have significantly improved overall stiffness, stability, and resistance to wind vibration loads, effectively reducing the risk of tower collapse. However, since a large number of towers are installed outdoors, although the steel surfaces of the towers are galvanized for protection, long-term corrosion can still occur on the inner and outer walls of the tower base in harsh climates prone to frost, heavy rain, and floods, potentially leading to serious safety accidents. Therefore, regularly inspecting the corrosion status and assessing the health condition of the steel pipe towers in power systems is extremely important for reducing the safe operation risks of transmission corridors.

[0003] To address the challenge of non-destructive testing (NDT) of tubular components, the industry typically employs methods such as penetrant testing, eddy current testing, industrial CT inspection, magnetic flux leakage testing, X-ray inspection, ultrasonic guided wave testing, and traditional ultrasonic testing. However, these methods all have significant limitations when applied to corrosion detection within transmission tower bases. Specifically, penetrant testing can only detect surface opening defects and cannot detect internal or inner wall corrosion; eddy current testing can only detect conductive materials and the results are not readily apparent; while industrial CT and X-ray inspections provide intuitive results, their high cost, low efficiency, and radiation safety hazards make them unsuitable for the large-scale on-site testing needs of transmission corridors; and magnetic flux leakage testing is highly susceptible to interference from the complex geometry, wall thickness, and material inhomogeneity of the tower base.

[0004] In the field of ultrasonic nondestructive testing, it is currently mainly divided into two directions: ultrasonic guided wave testing and ultrasonic phased array testing. However, both of them have bottlenecks that are difficult to overcome in practical applications. Traditional ultrasonic guided wave testing techniques (such as those using longitudinal, torsional, or bending modes) are suitable for rapid, long-distance inspection of pipe materials and can provide a rough location of defects. However, ultrasonic guided waves are not sensitive enough to uniform corrosion of pipe walls, axial cracks, and minor defects in welds. More seriously, the detection results are one-dimensional echo signals, which are not intuitive and cannot provide accurate quantitative assessment of the degree of corrosion damage (such as corrosion depth and area). Furthermore, in complex base structures, guided waves are prone to false positives and false negatives due to signal interference, multipath reflections, or mode conversions. Currently, the industry is attempting to combine ultrasonic guided wave preliminary localization with ultrasonic thickness gauges, but the effectiveness of this one-dimensional non-destructive testing combination in terms of detection accuracy and intuitiveness remains very limited.

[0005] While ultrasonic phased array technology offers higher detection accuracy than traditional single-probe technology, the tower base is often composed of highly specular and point scatterers with high acoustic impedance and significant differences in acoustic characteristics. Defect echo signals are typically only well represented when the ultrasonic wave is incident normally, making it extremely difficult to extract weak internal corrosion signals from complex background clutter. Furthermore, phased array technology requires extremely high surface smoothness of the pipe wall, and its detection results are easily interfered with by impurities inside the pipe and uneven rust surfaces. In addition, existing phased array ultrasonic imaging technology has many shortcomings in imaging resolution and real-time performance: during imaging, the ultrasonic echo signal received by the transducer is affected by various factors such as transducer diffraction, system electronic oscillation, excitation pulse width, and external electrical interference noise, resulting in time-varying effects. This leads to blurred, distorted, or even indistinguishable two-dimensional imaging results due to the coherent superposition of multiple defects, making it difficult to meet the needs of automated, high-precision quantitative non-destructive testing of circular pipe components.

[0006] In summary, to obtain richer detection information and improve the intuitiveness, objectivity, and accuracy of corrosion diagnosis of transmission tower foundations, ultrasonic non-destructive testing is gradually transitioning from traditional one-dimensional echo curve diagnosis and two-dimensional image diagnosis to three-dimensional ultrasonic non-destructive testing with high-definition visualization. This is an inevitable trend in the field. However, there is currently a lack of effective technical solutions for achieving high-precision, all-round, three-dimensional high-definition visualization real-time detection and quantitative assessment of corrosion inside the pipe walls of transmission tower foundations under harsh outdoor environments and complex interference conditions. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a three-dimensional imaging device for the pipe wall of transmission tower foundations and a method for assessing its corrosion status. This device can be effectively applied in engineering practice to assess the detailed defects and corrosion of the inner wall of transmission tower foundations. It can also assess whether there is any shoddy workmanship or insufficient strength during tower construction, and detect whether it meets standards, thereby ensuring the safety of transmission towers from the source. This invention combines ultrasonic guided wave measurement methods to achieve a high-quality detection solution integrating rapid coarse positioning and detailed high-definition imaging. This allows for a direct and accurate detailed assessment of the pipe wall of transmission line tower foundations, determining the corrosion status and defect contours of the inner wall, and promptly and effectively identifying potential safety hazards inside the tower, reducing the risk of tower collapse in transmission corridors. This is of great significance for the condition assessment and detection of easily corroded and damaged power system equipment, and ultimately for ensuring the safe operation of transmission corridors.

[0008] To achieve the above objectives, the present invention provides the following technical solution: Option 1: A three-dimensional imaging device for the pipe wall of a power transmission tower base, comprising an ultrasonic transmitting and receiving circuit, a stepper motor, a displacement sensor, and a ring track. The ultrasonic transmitting and receiving circuit includes an ultrasonic array probe, a switch array, a multiplexing module, an FPGA control module, an ultrasonic transmitting front-end circuit, an ultrasonic echo signal processing circuit, and a microcontroller.

[0009] A stepper motor drives the ultrasonic array probe to rotate 360° horizontally along a circular track. Each time the probe rotates by an angle, it measures the longitudinal thickness of the tube wall corresponding to the ultrasonic array element and records the radial geometric dimension between the ultrasonic array probe and the circular track based on the displacement sensor fixed on the spring device. After the stepper motor completes the 360° horizontal rotation around the circular track, it collects the longitudinal cross-sectional information of the tube wall corresponding to each angle.

[0010] The ultrasonic array probe includes multiple ultrasonic array elements arranged along the axial direction of the tower. The multiple ultrasonic array elements transmit and receive according to a preset array element combination to form a normal incident sound beam perpendicular to the pipe wall thickness direction and an oblique incident sound beam with a preset vertical angle relative to the pipe wall thickness direction. The normal incident sound beam is used to obtain the initial thickness information at the measurement point, and the oblique incident sound beam is used to confirm the suspected corrosion area on the inner wall corresponding to the same measurement point from multiple angles.

[0011] The ultrasonic array probe is used to emit ultrasonic waves and receive reflected echoes from the pipe wall interface; the switch array is used to select the ultrasonic array elements currently participating in transmission and reception; the multiplexing module is used to connect multiple ultrasonic array element channels sequentially to the transmission and reception channels according to the scanning order; the FPGA control module is used to receive external control signals and generate array element channel selection signals, transmission control signals, and transmit / receive switching control signals; the ultrasonic transmission front-end circuit is used to excite the selected ultrasonic array elements to emit ultrasonic waves, and to conduct the high-voltage pulse channel during the transmission phase and the low-voltage echo channel during the reception phase; the ultrasonic echo signal processing circuit is used to amplify, filter, and perform analog-to-digital conversion on the low-voltage echo signal conducted by the ultrasonic transmission front-end circuit; the microcontroller is used to send external control commands to the FPGA control module and to receive or manage subsequent acquired data.

[0012] Option 2: A method for assessing the corrosion status of the pipe wall of a transmission tower base, using the three-dimensional imaging device described in Option 1. This method specifically includes the following steps: S1: Rotate the ultrasonic array probe in the three-dimensional imaging device horizontally around the tower base for one revolution to obtain the longitudinal thickness information of the pipe wall; S2: Construct the external contour of the tube wall based on the angle information and horizontal radial data of the ultrasonic array probe; S3: Based on the angle information of the ultrasonic array probe and the wall thickness information, combined with the external contour information of the wall, construct the internal contour of the wall; S4: Confirm suspected corrosion points in the internal contour of the pipe wall using multi-angle acoustic beams; S5: Based on the obtained inner and outer contours of the pipe wall, construct the three-dimensional imaging results of the tower pipe wall; S6: Assess the mechanical strength of the tube wall based on the profile and thickness information of the tower tube wall; or assess the degree of corrosion of the inner tube wall of the tower based on the tube wall thickness, inner surface roughness and average multi-angle confirmation information.

[0013] Furthermore, in step S1, stepper motor 2 drives ultrasonic array probe 1 to rotate horizontally around the tower base for one revolution, collecting a total of [number missing] data. M There are [number] angular positions; (linear) ultrasonic array probe 1 has [number] total [number] angular positions; N Each array element corresponds to a height measurement point along the longitudinal direction of the pipe wall; the first... j Each angular position is denoted as , No. i The vertical height corresponding to each array element is denoted as . This forms a pipe wall thickness matrix indexed by "longitudinal height - circumferential angle"; Angular coordinates can be represented using an equal-angle sampling method as follows:

[0014] If we use a stepper motor with 2-pulse counting to calculate the angle, let the single-step angle of the motor be... The subdivision coefficient is , No. j The cumulative number of pulses during each acquisition is: Then the angular coordinates are:

[0015] No. i The vertical height coordinates corresponding to each array element are:

[0016] in, This is the initial height. This represents the vertical spacing between adjacent array elements.

[0017] Furthermore, in step S2, constructing the outer contour of the pipe wall specifically includes: in the first... j At various angular positions, the displacement sensor records the radial expansion and contraction between the ultrasonic array probe 1 and the annular track 5. Let the radius from the center of the circular track 5 to the track reference plane be... The fixed compensation distance introduced by the probe wedge, coupling layer, and mechanical installation is: Then, the radius of the outer surface of the pipe wall at this angle can be expressed as:

[0018] If we further consider the zero-point error of the displacement sensor and the installation eccentricity error, the outer wall radius can be corrected as follows:

[0019] in, For the zero-point error of the displacement sensor, For the first j The radial eccentricity compensation at each angular position; converting the cylindrical coordinates to spatial rectangular coordinates, the radial eccentricity compensation at each angular position of the outer surface of the pipe wall can be obtained. i The height, the first j Three-dimensional coordinates at each angle:

[0020]

[0021]

[0022] Therefore, the point cloud set on the outer surface of the pipe wall can be represented as: .

[0023] Through the above calculations, the outer contour of the pipe wall can be obtained from the probe angle information and radial displacement information, providing a geometric reference for subsequent internal contour inversion and three-dimensional imaging.

[0024] Furthermore, in step S3, constructing the internal contour of the pipe wall specifically includes: at each angle Below, ultrasonic array probe 1 sequentially measures the tube wall thickness corresponding to each array element; let the first... i Each array element, the first j The arrival time of the outer wall interface echo detected at each angle position is: The arrival time of the echo from the inner wall interface is Then the echo time difference is:

[0025] The ultrasonic wave undergoes two propagation processes in the direction of the pipe wall thickness: incident and reflected. Therefore, the pipe wall thickness at the measuring point at this angle is:

[0026] in, c The propagation speed of ultrasound in steel can be determined based on the type of steel or experimental calibration results. To reduce the impact of echo noise, local false detections, and abnormal measurement points on the 3D reconstruction results, neighborhood smoothing can be performed on the pipe wall thickness data.

[0027] in, This is the smoothed pipe wall thickness value. For neighborhood weights, a and b These represent the smoothing ranges in the longitudinal and circumferential directions, respectively; given the outer surface radius and pipe wall thickness, the inner surface radius... It can be obtained by subtracting the thickness at the corresponding position from the outer surface radius:

[0028] Therefore, the three-dimensional coordinates of the inner surface are:

[0029]

[0030]

[0031] This yields the point cloud set of the inner surface of the pipe wall: .

[0032] This allows the internal contour of the pipe wall to be deduced from the external contour and thickness matrix. If internal corrosion exists in a certain area, the thickness value at the corresponding location decreases, and the inner wall radius shifts towards the outer wall, which manifests as local depressions, pitting, or thinning areas in the 3D model.

[0033] Furthermore, in step S4, after obtaining the smoothed pipe wall thickness value... and inner surface radius Then, based on the thickness reduction at the measuring points... Thickness reduction rate Neighborhood thickness deviation and abnormal offset of inner wall radius Preliminary judgment is made on suspected corrosion points; when a measuring point meets the following conditions, such as the thickness is lower than the preset thickness threshold, the thickness reduction rate exceeds the preset thinning rate threshold, the thickness deviation of the neighboring area exceeds the preset deviation threshold, or the inner wall radius deviates abnormally relative to the average inner wall radius of the neighboring area, the measuring point is marked as a suspected corrosion point.

[0034]

[0035]

[0036]

[0037]

[0038]

[0039] Define a preliminary function for identifying suspected erosion points. A measuring point is marked as a suspected corrosion point when it meets any of the following conditions:

[0040] At this time, it is ordered that:

[0041] When none of the above conditions are met, let:

[0042] in, This indicates that the (i,j)th measuring point is marked as a suspected corrosion point; For design thickness; The thickness of the measurement point after smoothing; Thickness threshold; The thickness reduction rate threshold; The threshold for neighborhood thickness deviation; The threshold for abnormal offset of the inner wall radius; This refers to the local neighborhood of the measurement point (i,j). This represents the original pipe wall thickness measurement at the (i,j)th measuring point without smoothing. Let be the radius of the inner surface of the pipe wall at the (i,j)th measuring point.

[0043] The multi-angle acoustic beam confirmation steps for suspected corrosion sites specifically include: When measurement point (i,j) is marked as a suspected corrosion point, the corresponding element in the ultrasonic array probe is controlled to emit a normally incident sound beam, and the adjacent elements above and / or below the normally incident element are controlled to emit obliquely incident sound beams, so that the sound beams emitted by different elements are directed to the same suspected corrosion area. The echo time of the outer wall interface, the echo time of the inner wall interface, the echo amplitude of the inner wall, and the echo phase characteristics of the inner wall are extracted for the normally incident sound beam and the obliquely incident sound beam, respectively. Based on the thickness consistency, echo amplitude anomaly consistency, and inner wall position consistency calculated by the multi-angle sound beam, the suspected corrosion point is confirmed. When the multi-angle confirmation index meets the preset conditions, the suspected corrosion point is confirmed as a valid corrosion point. Thickness measurement with normal incident sound beam:

[0044]

[0045] in, The time difference between the echo from the outer wall interface and the echo from the inner wall interface of the normally incident sound beam. The arrival time of the echo from the outer wall interface of the normally incident sound beam. The arrival time of the echo from the inner wall interface of the normally incident sound beam is denoted as . The tube wall thickness is measured by the normally incident sound beam; Oblique incidence beam path correction:

[0046]

[0047]

[0048]

[0049] Or it can be written in the form of angle correction:

[0050]

[0051] in, Number the offset array elements; This represents the axial distance between the offset element and the directly opposite element. The length of the one-way propagation path of the oblique sound beam in the tube wall; The equivalent normal thickness after correction of the oblique sound beam; Let q be the angle between the qth obliquely incident sound beam and the direction of the tube wall normal; Let be the arrival time of the echo from the inner wall interface corresponding to the q-th oblique sound beam. Let q be the arrival time of the echo from the outer wall interface corresponding to the qth oblique sound beam; Multi-angle thickness consistency:

[0052]

[0053]

[0054]

[0055] in, For the set of sound beams to be confirmed; This represents the average thickness from multiple angles. For multi-angle thickness variance; For thickness consistency indicators; The allowable thickness fluctuation threshold; Abnormal consistency in echo amplitude:

[0056]

[0057]

[0058]

[0059] in, For local neighborhood The reference echo amplitude of the inner wall corresponding to the (p,r)th nearest measuring point under the normal incident sound beam; The neighborhood reference echo amplitude; For the first The echo amplitude of the inner wall corresponding to the beam; For the first The amplitude attenuation rate of the bar beam; The average amplitude attenuation rate from multiple angles; This is an indicator for confirming abnormal echo amplitude. This is the amplitude attenuation rate threshold; To determine the steepness coefficient of the discriminant function; Inner wall position consistency:

[0060]

[0061]

[0062] in, For the first The inner wall radius obtained by strip beam inversion; This represents the average radius of the inner wall at multiple angles. The variance of the inner wall position; This serves as an indicator of the consistency of the inner wall position. The threshold for allowable inner wall position deviation.

[0063] Multi-angle corrosion confirmation coefficient:

[0064]

[0065]

[0066] in, This is the confirmation coefficient for multi-angle corrosion. The weights are respectively for thickness consistency, amplitude anomaly consistency, and inner wall position consistency; To confirm the threshold from multiple perspectives; This indicates that the suspected corrosion point has been confirmed as a valid corrosion point.

[0067] Furthermore, in step S5, the three-dimensional imaging results of the tower wall are constructed, specifically including: obtaining the point cloud of the outer surface. and inner surface point cloud Next, sampling points at adjacent heights and angles need to be meshed to form a complete three-dimensional surface of the pipe wall; for the outer wall, four adjacent sampling points form an outer wall mesh unit: ,in For the first i The height, the first j Point clouds on the outer wall at various angles; For the inner wall, four adjacent sampling points form an inner wall grid cell: ,in For the first i The height, the first j Point clouds on the inner wall at various angles; Since the tower base tube wall is a ring structure, the angular direction needs to meet the periodic boundary conditions:

[0068]

[0069] To improve the continuity and display accuracy of 3D imaging, interpolation can be performed on the radius field:

[0070]

[0071] in, This represents bilinear interpolation, cubic spline interpolation, or surface fitting interpolation algorithms; ultimately, the three-dimensional solid model of the pipe wall can be represented as:

[0072] in, and These represent the point clouds of the outer and inner walls, respectively. and These represent the outer and inner wall mesh patches, respectively. Using this model, the host computer can display the outer contour, inner contour, localized thinning areas, and three-dimensional corrosion distribution of the pipe wall, achieving high-definition visualization imaging of the tower pipe wall.

[0073] Furthermore, in step S6, the evaluation of the mechanical strength of the pipe wall specifically includes: pipe wall corrosion leads to a local reduction in thickness, thereby reducing the cross-sectional bearing capacity and bending resistance of the tower base. Let the designed pipe wall thickness be... The outer radius in the uncorroded state is The inner radius is:

[0074] Cross-sectional area in the uncorroded state for: ; Moment of inertia of cross section in uncorroded state for: ; For the detected i,j position, its local inner radius is:

[0075] Corresponding local cross-sectional area It can be represented as: ; Corresponding local section moment of inertia It can be represented as: ; Define the local mechanical strength retention factor for: ;when The closer the value is to 1, the better the mechanical properties of the pipe wall in that region are maintained; when When the value decreases significantly, it indicates that the bending resistance of the area has decreased significantly due to thinning caused by corrosion.

[0076] To conduct an overall safety assessment, a worst-case strength retention factor can be defined. for: Or define the average strength retention factor. for: ;in, Used to determine the most dangerous corrosion locations. It is used to reflect the overall structural strength retention.

[0077] The results were confirmed using multi-angle acoustic beams, and the most unfavorable strength retention factor was calculated within the effective corrosion point set.

[0078] in, Used to characterize and confirm the most dangerous mechanical strength retention status in the corroded area from multiple angles.

[0079] Furthermore, in step S6, the evaluation of the corrosion degree of the inner wall of the tower specifically includes a comprehensive evaluation from three aspects: thickness reduction, corrosion area ratio, and inner wall roughness. First, based on the multi-angle corrosion confirmation coefficient... Define the thickness reduction at the i-th and j-th measurement points. for:

[0080] Thickness reduction rate for: ; Minimum remaining thickness within the detection area for: ; Maximum thickness reduction rate for: ; Secondly, let the thickness warning threshold be... When the thickness at a measurement point is less than this threshold, the location is determined to be a corrosion risk area; corrosion indicator function. for:

[0081]

[0082] Percentage of corroded area It can be represented as:

[0083] If the area of ​​the curved surface mesh is considered, the first i,j Area of ​​each grid cell It can be approximated as: ,in, This refers to the angular interval between two adjacent rotational samplings of the ultrasonic array probe. It is the height interval between two adjacent longitudinal height measuring points, that is, the distance between the corresponding measuring points of adjacent array elements in the axial direction of the tower; The corrosion area percentage can then be corrected as follows:

[0084] Next, the roughness of the inner surface is evaluated using the undulation of the inner wall radius; let... For measuring points The local neighborhood of the surrounding area, the average radius of the inner wall within that neighborhood. for:

[0085] The local roughness at that location for:

[0086] The maximum roughness of the detection area is:

[0087] Increase average multi-angle confirmation:

[0088] in, To prevent the stability coefficient from having a denominator of zero, This indicates the average multi-angle confirmation of the effective corrosion area.

[0089] Finally, a comprehensive evaluation index for corrosion status was established by taking into account the thickness reduction rate, corrosion area ratio, inner wall roughness, and average multi-angle confirmation degree. for:

[0090] in, , , , Let be the weighting coefficient, and satisfy: ; The allowable roughness of the inner wall or the experimentally calibrated roughness; Based on comprehensive evaluation indicators The corrosion state can be divided into four levels, among which Class I slight corrosion. Class II moderate corrosion Class III severe corrosion. It is classified as Class IV hazardous corrosion; its determination function is:

[0091] in, , , The corrosion level threshold can be determined through experimental calibration, on-site testing experience, or tower design safety requirements.

[0092] The beneficial effects of this invention are as follows: 1) This invention extends one-dimensional ranging to two-dimensional longitudinal cross-sectional imaging by controlling an ultrasonic linear array probe to perform horizontal spatial rotation scanning. Furthermore, by combining spatial orientation information with a three-dimensional model reconstruction algorithm, it achieves high-definition three-dimensional visualization imaging of the internal structure of the transmission tower base pipe wall. This method can intuitively and clearly present the contours of defects and corrosion details on the inner wall of the tower base, completely solving the problems of false detections and missed detections caused by the lack of intuitive results in traditional methods.

[0093] 2) This invention targets the inner wall of the tower base tube. By constructing a correlation function between tube wall thickness, surface roughness, and effective corrosion status (using multi-angle sound beams to confirm suspected corrosion points in the inner contour of the tube wall), it can not only accurately extract the characteristics of hidden corrosion on the inner wall, but also automatically filter out areas where the tube wall thickness is less than a set threshold and provide real-time early warnings. This greatly assists maintenance personnel in assessing the health status of transmission corridors and can effectively reduce the safety risk of tower collapse.

[0094] 3) To address the significant near-field blind zone issue inherent in traditional phased array or linear arrays in transmit / receive combined mode, this invention employs a separate transmit / receive array element switching control method. This effectively eliminates the near-field blind zone while ensuring high-speed switching scanning, guaranteeing the horizontal and vertical resolution of the cross-section reconstruction. Through the cooperation of a general-purpose ring guide rail, spring device, and displacement sensor, this invention ensures that the probe is strictly perpendicular to the surface of the object being probed during 360° horizontal rotation, accurately compensating for radial geometric changes in real time. This effectively solves the bottleneck of traditional phased array technology, which requires excessively high surface flatness and is susceptible to interference from impurities, avoiding image distortion and information loss in 3D reconstruction.

[0095] 4) Compared to high-cost, low-efficiency technologies such as industrial CT and X-ray inspections, which pose radiation safety hazards, the ultrasonic non-destructive testing method used in this invention is completely harmless to the human body and has low equipment inspection costs. The device design of this invention is modular, portable, and capable of real-time imaging, making it highly adaptable to harsh and variable working environments such as outdoor or field power transmission corridors, thus reducing the workload of on-site operators.

[0096] 5) This invention can not only be used to periodically assess the corrosion and potential hazards of the inner wall of the base of in-service transmission towers; it can also be extended to the quality acceptance during the construction process of towers, effectively detecting whether there are any cases of shoddy workmanship, insufficient strength, or failure to meet national standards, thereby achieving root cause control of power safety throughout the entire life cycle from infrastructure construction to operation and maintenance.

[0097] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0098] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1 This is a detailed flowchart of the corrosion status assessment method for the pipe wall of the transmission tower base based on three-dimensional imaging, according to the present invention. Figure 2 A schematic diagram of data acquisition for an ultrasonic three-dimensional high-definition visualization imaging device; Figure 3 This is a block diagram of an ultrasonic transmitter and receiver circuit. Figure 4 This is a flowchart of the ultrasonic wave transmission process. Figure 5 This is a block diagram of an ultrasonic echo signal processing circuit. Figure 6This is a schematic diagram of the method for generating the longitudinal section of the pipe wall; Figure 7 A simplified flowchart illustrating the corrosion status assessment method for the pipe wall of a transmission tower base based on three-dimensional imaging; Figure 8 This is a 3D imaging effect of the pipe wall.

[0099] Reference numerals: 1-ultrasonic array probe, 2-stepper motor, 3-probe fixing bracket, 4-spring device, 5-circular track, 6-track connecting buckle. Detailed Implementation

[0100] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0101] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0102] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0103] Example 1: Please see Figure 2This embodiment provides a three-dimensional imaging device for the pipe wall of a power transmission tower base, including an ultrasonic transmitting and receiving circuit, an ultrasonic echo signal processing circuit, a stepper motor, a displacement sensor, and a ring track. It includes an ultrasonic array probe, a switch array, a multiplexing module (MUX), an FPGA control module, an ultrasonic transmitting front-end circuit, an ultrasonic echo signal processing circuit, and a microcontroller.

[0104] The ultrasonic array probe includes multiple ultrasonic array elements arranged along the axial direction of the tower. The multiple ultrasonic array elements transmit and receive according to a preset array element combination to form a normal incident sound beam perpendicular to the pipe wall thickness direction and an oblique incident sound beam with a preset vertical angle relative to the pipe wall thickness direction. The normal incident sound beam is used to obtain the initial thickness information at the measurement point, and the oblique incident sound beam is used to confirm the suspected corrosion area on the inner wall corresponding to the same measurement point from multiple angles.

[0105] Stepper motor 2 drives (linear) ultrasonic array probe 1 to rotate 360° horizontally along the ring track 5. Every time it rotates by a small angle, ultrasonic array probe 1 measures the longitudinal thickness information of the tube wall corresponding to the ultrasonic array element, and records the radial geometric dimension between ultrasonic array probe 1 and (detachable telescopic probe) ring track 5 according to the displacement sensor fixed on spring device 4.

[0106] After stepper motor 2 completes a 360° horizontal rotation around the circular track 5, longitudinal cross-sectional information of the pipe wall at each angle can be collected. Since the geometry of the track is fixed, and radial information at different angles has also been collected, all the raw data required for reconstructing the 3D image of the tower pipe wall is obtained. The collected raw data is then uploaded to the host computer, and a 3D image reconstruction algorithm is used to obtain the 3D reconstructed image of the tower pipe wall.

[0107] Example 2: This embodiment provides a specific structure for an ultrasonic transmitting and receiving circuit.

[0108] (1) Ultrasonic transmitting and receiving circuit The transmitting circuit of an ultrasonic imaging device generates significant interference, making the design of the transmitting and receiving circuitry particularly critical. The performance of this section directly impacts the overall system performance. For example, the ultrasonic transmitting and receiving circuitry... Figure 3As shown, the circuit mainly includes an ultrasonic array probe, a switch array, a multiplexing module (MUX), an FPGA control module, an ultrasonic transmitting front-end circuit, an ultrasonic echo signal processing circuit, and a microcontroller. The ultrasonic array probe is used to transmit ultrasonic waves and receive echoes reflected from the tube wall interface. The switch array is used to select the ultrasonic array element currently participating in transmission and reception. The MUX is used to sequentially connect multiple ultrasonic array element channels to the transmission and reception channels according to the scanning order. The FPGA control module is used to receive external control signals and generate array element channel selection signals, transmission control signals, and transmit / receive switching control signals. T / R CTRL represents the transmit / receive control signal, used to control the switching of ultrasonic array elements between transmission and reception states; CTRL represents the control signal, used to control the operating timing of the high-voltage pulse transmitting chip and the transmit / receive switch. HV Pulse represents the high-voltage pulse signal, used to excite the selected ultrasonic array element to transmit ultrasonic waves; T / R SW represents the transmit / receive switching switch, used to conduct the high-voltage pulse channel during the transmission phase and the low-voltage echo channel during the reception phase, preventing the high-voltage transmission signal from directly entering the subsequent receiving circuit. The ultrasonic echo signal processing circuit is used to amplify, filter, and perform analog-to-digital conversion on the ultrasonic echo signal. The microcontroller is used to send external control commands to the FPGA control module and to receive or manage subsequent acquired data.

[0109] The ultrasonic transmitting front-end circuit is planned to use the integrated chip HDL6M05584, which integrates a high-voltage pulse generator and a high-voltage transceiver switch, serving as the ultrasonic pulse transmitting and receiving control device. The switch array is planned to use ECN3290TF as the high-voltage multiplexing switch for scanning the linear array probe elements. The ultrasonic transmitting and receiving module is planned to use Intel's Cyclone III series EP3C10E144I7N to control the ultrasonic pulse generation and the state switching of the transmitting and receiving switches. This module controls the ultrasonic transmission process as follows: Figure 4 As shown.

[0110] After receiving the external start signal, the control system, according to Figure 4 The process shown enables the ultrasonic switch array to be turned on sequentially. The FPGA control module controls the HDL6M05584 to emit high-voltage pulses to excite the array elements in sequence, and controls the ultrasonic echo signal output to the ultrasonic echo signal processing circuit. Then the above steps are repeated until the scanning is completed.

[0111] (2) Ultrasonic Echo Signal Processing Circuit In this embodiment, the ultrasonic echo signal processing circuit consists of an analog front-end acquisition circuit (such as chip AFE5805), a digital-to-analog converter (such as DAC902), and a clock conditioner (such as LMK03033C), and its block diagram is as follows. Figure 5 As shown.

[0112] The AFE5805 internally includes functional modules such as a low-noise amplifier (LNA), a variable gain amplifier or programmable gain amplifier (VCA / PGA), a low-pass filter (LPF), and an analog-to-digital converter (ADC). The LNA performs primary amplification of small-amplitude ultrasonic echo signals and minimizes the impact of pre-amplifier noise on the signal. The VCA / PGA dynamically adjusts the amplification factor based on the echo signal strength. The LPF filters out high-frequency noise and out-of-band interference, improving the signal-to-noise ratio of the echo signal. The ADC converts the analog echo signal into digital echo data. The DAC902 outputs the TGC gain compensation control signal, where TGC stands for Time Gain Compensation, used to compensate for the decrease in echo amplitude caused by propagation distance and material attenuation during ultrasonic wave propagation through the pipe wall. The LMK03033C provides a high-precision sampling clock for the AFE5805, ensuring the synchronization and stability of multi-channel echo signal acquisition.

[0113] The digital echo data processed by the AFE5805 is transmitted to the FPGA via the LVDS interface. The FPGA performs data buffering, timing control, and data organization required for subsequent thickness calculation.

[0114] (3) Method for generating longitudinal section diagram of pipe wall Methods for generating longitudinal cross-sections of tower pipe walls, such as Figure 6 As shown, (a) is the echo signal curve acquired by a single ultrasonic array element, with the horizontal axis... The vertical axis represents the ultrasonic echo propagation time. (a) Represents the echo voltage amplitude; (b) shows the arrangement of thickness data measured by multiple ultrasonic array elements, with the vertical axis representing the vertical axis. The horizontal axis represents the ultrasonic element number or the corresponding longitudinal measurement point number. (c) represents the pipe wall thickness calculated from the echo time difference; (d) is a longitudinal cross-sectional view of the pipe wall generated based on the thickness data of multiple array elements.

[0115] Specifically, after the ultrasound waves are reflected from the outer and inner surfaces of the pipe wall, two main peaks are formed in the echo signal. Let the first... The arrival time of the echo from the outer wall interface corresponding to each array element is: The arrival time of the echo from the inner wall interface is The time difference between the two peaks is:

[0116] Because the ultrasonic wave propagates back and forth along the thickness of the pipe wall, therefore the first The wall thickness at the measuring point corresponding to each array element It can be represented as:

[0117] in, Let be the speed of ultrasonic wave propagation in steel, typically taken as 5900 mm / s. Calculate the first to the second... The thickness value corresponding to each array element By connecting and interpolating according to the arrangement order of the array elements in the axial direction of the tower, the following can be obtained: Figure 6 The longitudinal cross-sectional view of the pipe wall shown in (c) is shown in the middle.

[0118] Example 3: Please see Figure 1 and Figure 7 This embodiment provides a method for assessing the corrosion status of the pipe wall of a transmission tower base, specifically including the following steps: Step 1: The ultrasonic array probe rotates 360º around the pipe wall of the tower base to collect angle information, radial displacement data, and pipe wall thickness information; Step 2: The external contour of the pipe wall can be constructed based on the collected angle information and radial displacement data.

[0119] Step 3: Based on the collected angle information and pipe wall thickness information, and combined with the external contour information of the pipe wall (i.e., the thickness matrix), the internal contour of the pipe wall is inverted, thus constructing the internal contour of the pipe wall.

[0120] Step 4: Initially identify suspected corrosion points, and then use multi-angle sound beams to confirm valid corrosion points.

[0121] Step 5: Construct point cloud and mesh models of the inner and outer walls to generate high-definition 3D visualization imaging results of the pipe wall, i.e., the 3D imaging results of the tower pipe wall. See [link / reference]. Figure 8 , Figure 8 Each corroded area exhibits a localized thinning morphology with inward depressions, which can intuitively characterize the location, distribution range, and morphological features of corrosion.

[0122] Step 6: Based on the tower pipe wall profile and thickness information, the mechanical strength of the pipe wall can be assessed; the thickness reduction rate, corrosion area ratio and inner wall roughness can also be calculated to comprehensively evaluate the corrosion state and classify corrosion equivalence.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A three-dimensional imaging device for the pipe wall of a transmission tower base, comprising an ultrasonic transmitting and receiving circuit, characterized in that, The device also includes a stepper motor, a displacement sensor, and a circular track; the ultrasonic transmitting and receiving circuit includes an ultrasonic array probe, a switch array, a multiplexing module, an FPGA control module, an ultrasonic transmitting front-end circuit, an ultrasonic echo signal processing circuit, and a microcontroller. A stepper motor drives the ultrasonic array probe to rotate 360° horizontally along a circular track. Each time the probe rotates by an angle, it measures the longitudinal thickness of the tube wall corresponding to the ultrasonic array element and records the radial geometric dimension between the ultrasonic array probe and the circular track based on the displacement sensor fixed on the spring device. After the stepper motor completes the 360° horizontal rotation around the circular track, it collects the longitudinal cross-sectional information of the tube wall corresponding to each angle. The ultrasonic array probe includes multiple ultrasonic array elements arranged along the axial direction of the tower. The multiple ultrasonic array elements transmit and receive according to a preset array element combination to form a normal incident sound beam perpendicular to the pipe wall thickness direction and an oblique incident sound beam with a preset vertical angle relative to the pipe wall thickness direction. The normal incident sound beam is used to obtain the initial thickness information at the measurement point, and the oblique incident sound beam is used to confirm the suspected corrosion area on the inner wall corresponding to the same measurement point from multiple angles. The ultrasonic array probe is used to emit ultrasonic waves and receive the reflected echoes from the pipe wall interface; the switch array is used to select the ultrasonic array element currently participating in transmission and reception; the multiplexing module is used to connect multiple ultrasonic array element channels to the transmission and reception channels in sequence according to the scanning order. The FPGA control module is used to receive external control signals and generate array element channel selection signals, transmission control signals and transmit / receive switching control signals; the ultrasonic transmitting front-end circuit is used to excite the selected ultrasonic array element to transmit ultrasonic waves, and to conduct the high-voltage pulse channel during the transmission phase and the low-voltage echo channel during the receiving phase. The ultrasonic echo signal processing circuit is used to amplify, filter, and perform analog-to-digital conversion on the low-voltage echo signal transmitted by the acoustic emission front-end circuit; the microcontroller is used to send external control commands to the FPGA control module and to receive or manage subsequent acquired data. The assessment of corrosion status of the transmission tower base pipe wall using the aforementioned three-dimensional imaging device includes the following steps: S1: Rotate the ultrasonic array probe in the three-dimensional imaging device horizontally around the tower base for one revolution to obtain the longitudinal thickness information of the pipe wall; S2: Construct the outer contour of the tube wall based on the angle information and horizontal radial data of the ultrasonic array probe; S3: Based on the angle information of the ultrasonic array probe and the wall thickness information, combined with the external contour information of the wall, construct the internal contour of the wall; S4: Confirm suspected corrosion points in the internal contour of the pipe wall using multi-angle acoustic beams; Obtain the smoothed pipe wall thickness value and inner surface radius Then, based on the thickness reduction at the measuring points... Thickness reduction rate Neighborhood thickness deviation and abnormal offset of inner wall radius Preliminary judgment is made on suspected corrosion points; when a measuring point meets the following conditions, such as the thickness is lower than the preset thickness threshold, the thickness reduction rate exceeds the preset thinning rate threshold, the thickness deviation of the neighboring area exceeds the preset deviation threshold, or the inner wall radius deviates abnormally relative to the average inner wall radius of the neighboring area, the measuring point is marked as a suspected corrosion point. Define a preliminary function for identifying suspected erosion points. A measuring point is marked as a suspected corrosion point when it meets any of the following conditions: At this time, it is ordered that: When none of the above conditions are met, let: in, This indicates that the (i,j)th measuring point is marked as a suspected corrosion point; For design thickness; The thickness of the measurement point after smoothing; Thickness threshold; The thickness reduction rate threshold; The threshold for neighborhood thickness deviation; The threshold for abnormal offset of the inner wall radius; This refers to the local neighborhood of the measurement point (i,j). This represents the original pipe wall thickness measurement at the (i,j)th measuring point without smoothing. Let be the radius of the inner surface of the pipe wall at the (i,j)th measuring point; When measurement point (i,j) is marked as a suspected corrosion point, the corresponding element in the ultrasonic array probe is controlled to emit a normally incident sound beam, and the adjacent elements above and / or below the normally incident element are controlled to emit obliquely incident sound beams, so that the sound beams emitted by different elements are directed to the same suspected corrosion area. The echo time of the outer wall interface, the echo time of the inner wall interface, the echo amplitude of the inner wall, and the echo phase characteristics of the inner wall are extracted for the normally incident sound beam and the obliquely incident sound beam, respectively. Based on the thickness consistency, echo amplitude anomaly consistency, and inner wall position consistency calculated by the multi-angle sound beam, the suspected corrosion point is confirmed. When the multi-angle confirmation index meets the preset conditions, the suspected corrosion point is confirmed as a valid corrosion point. Thickness measurement with normal incident sound beam: in, The time difference between the echo from the outer wall interface and the echo from the inner wall interface of the normally incident sound beam. The arrival time of the echo from the outer wall interface of the normally incident sound beam. The arrival time of the echo from the inner wall interface of the normally incident sound beam is denoted as . The tube wall thickness is measured by the normally incident sound beam; Oblique incidence beam path correction: Or it can be written in the form of angle correction: in, Number the offset array elements; This represents the axial distance between the offset element and the directly opposite element. The length of the one-way propagation path of the oblique sound beam in the tube wall; The equivalent normal thickness after correction of the oblique sound beam; Let q be the angle between the qth obliquely incident sound beam and the direction of the tube wall normal; Let be the arrival time of the echo from the inner wall interface corresponding to the q-th oblique sound beam. Let q be the arrival time of the echo from the outer wall interface corresponding to the qth oblique sound beam; Multi-angle thickness consistency: in, For the set of sound beams to be confirmed; This represents the average thickness from multiple angles. For multi-angle thickness variance; For thickness consistency indicators; The allowable thickness fluctuation threshold; Abnormal consistency in echo amplitude: in, For local neighborhood The reference echo amplitude of the inner wall corresponding to the (p,r)th nearest measuring point under the normal incident sound beam; The neighborhood reference echo amplitude; For the first The echo amplitude of the inner wall corresponding to the beam; For the first The amplitude attenuation rate of the bar beam; The average amplitude attenuation rate from multiple angles; This is an indicator for confirming abnormal echo amplitude. This is the amplitude attenuation rate threshold; To determine the steepness coefficient of the discriminant function; Inner wall position consistency: in, For the first The inner wall radius obtained by beam inversion; This represents the average radius of the inner wall at multiple angles. The variance of the inner wall position; This serves as an indicator of the consistency of the inner wall position. The allowable inner wall position deviation threshold; Multi-angle corrosion confirmation coefficient: in, This is the confirmation coefficient for multi-angle corrosion. The weights are respectively for thickness consistency, amplitude anomaly consistency, and inner wall position consistency; To confirm the threshold from multiple perspectives; This indicates that the suspected corrosion point has been confirmed as a valid corrosion point; S5: Based on the obtained inner and outer contours of the pipe wall, construct the three-dimensional imaging results of the tower pipe wall; S6: Assess the mechanical strength of the tube wall based on the profile and thickness information of the tower tube wall; or assess the degree of corrosion of the inner tube wall of the tower based on the tube wall thickness, inner surface roughness and average multi-angle confirmation information.

2. The three-dimensional imaging device for the pipe wall of the transmission tower base according to claim 1, characterized in that, In step S1, the stepper motor drives the ultrasonic array probe to rotate horizontally around the tower base for one revolution, collecting a total of [number] data. M The ultrasonic array probe has [number] angular positions; N Each array element corresponds to a height measurement point along the longitudinal direction of the pipe wall; the first... j Each angular position is denoted as , No. i The vertical height corresponding to each array element is denoted as . This forms a pipe wall thickness matrix indexed by "longitudinal height - circumferential angle"; Angular coordinates are represented using an equal-angle sampling method as follows: If we use stepper motor pulse counting to calculate the angle, let the single-step angle of the motor be... The subdivision coefficient is , No. j The cumulative number of pulses during each acquisition is: Then the angular coordinates are: No. i The vertical height coordinates corresponding to each array element are: in, The initial height, This represents the vertical spacing between adjacent array elements.

3. The three-dimensional imaging device for the pipe wall of the transmission tower base according to claim 2, characterized in that, In step S2, constructing the outer contour of the pipe wall specifically includes: in the first... j At various angular positions, displacement sensors record the radial expansion and contraction between the ultrasonic array probe and the circular track. Let the radius from the center of the circular track to the track reference plane be... The fixed compensation distance introduced by the probe wedge, coupling layer, and mechanical installation is: Considering the zero-point error of the displacement sensor and the installation eccentricity error, the outer wall radius is expressed as: in, For the zero-point error of the displacement sensor, For the first j The radial eccentricity compensation at each angular position; converting the cylindrical coordinates to spatial rectangular coordinates, the radial eccentricity compensation at each angular position of the outer surface of the pipe wall is obtained. i The height, the first j Three-dimensional coordinates at each angle: Therefore, the point cloud set on the outer surface of the pipe wall is represented as: 。 4. The three-dimensional imaging device for the pipe wall of the transmission tower base according to claim 3, characterized in that, In step S3, constructing the internal contour of the pipe wall specifically includes: at each angle Below, the ultrasonic array probe sequentially measures the tube wall thickness corresponding to each array element; let the first element be... i Each array element, the first j The arrival time of the outer wall interface echo detected at each angle position is: The arrival time of the echo from the inner wall interface is Then the echo time difference is: The ultrasonic wave undergoes two propagation processes in the direction of the pipe wall thickness: incident and reflected. Therefore, the pipe wall thickness at the measuring point at this angle is: in, c The propagation speed of ultrasound in steel; neighborhood smoothing processing is performed on the pipe wall thickness data: in, This is the smoothed pipe wall thickness value. For neighborhood weights, a and b These represent the smoothing ranges in the longitudinal and circumferential directions, respectively; given the outer surface radius and pipe wall thickness, the inner surface radius... The thickness at the corresponding location is obtained by subtracting the outer surface radius from the outer surface radius: Therefore, the three-dimensional coordinates of the inner surface are: This yields the point cloud set of the inner surface of the pipe wall: 。 5. The three-dimensional imaging device for the pipe wall of the transmission tower base according to claim 1, characterized in that, In step S5, the three-dimensional imaging results of the tower wall are constructed, specifically including: obtaining the point cloud of the outer surface. and inner surface point cloud Next, sampling points at adjacent heights and angles need to be meshed to form a complete three-dimensional surface of the pipe wall; for the outer wall, four adjacent sampling points form an outer wall mesh unit: ,in For the first i The height, the first j Point clouds on the outer wall at various angles; For the inner wall, four adjacent sampling points form an inner wall grid cell: ,in For the first i The height, the first j Point clouds on the inner wall at various angles; Since the tower base tube wall is a ring structure, the angular direction satisfies the periodic boundary condition: Interpolation processing is performed on the radius field: in, This represents bilinear interpolation, cubic spline interpolation, or surface fitting interpolation algorithms; ultimately, the three-dimensional solid model of the pipe wall is represented as: in, and These represent the point clouds of the outer and inner walls, respectively. and These represent the outer and inner wall mesh patches, respectively.

6. The three-dimensional imaging device for the pipe wall of the transmission tower base according to claim 1, characterized in that, In step S6, evaluating the mechanical strength of the pipe wall specifically includes: assuming the designed pipe wall thickness is... The outer radius in the uncorroded state is The inner radius is: Moment of inertia of cross section in uncorroded state for: ; For the detected first i,j The local section moment of inertia at each location. Represented as: ; Define the local mechanical strength retention factor for: ; To conduct an overall safety assessment, a worst-case strength retention factor is defined. for: Or define the average strength retention factor. for: ;in, Used to determine the most dangerous corrosion locations. Used to reflect the overall structural strength retention; The results were confirmed using multi-angle acoustic beams, and the most unfavorable strength retention factor was calculated within the effective corrosion point set. in, Used to characterize and confirm the most dangerous mechanical strength retention status in the corroded area from multiple angles.

7. The three-dimensional imaging device for the pipe wall of the transmission tower base according to claim 5, characterized in that, In step S6, the evaluation of the corrosion degree of the inner wall of the tower specifically includes a comprehensive evaluation from three aspects: thickness reduction, corrosion area ratio, and inner wall roughness; firstly, based on the multi-angle corrosion confirmation coefficient... , define the first i , j Thickness reduction at each measuring point for: Thickness reduction rate for: ; Minimum remaining thickness within the detection area for: ; Maximum thickness reduction rate for: ; Secondly, let the thickness warning threshold be... When the thickness at a measurement point is less than this threshold, the location is determined to be a corrosion risk area; corrosion indicator function. for: Percentage of corroded area Represented as: If the area of ​​the curved surface mesh is considered, the first i , j Area of ​​each grid cell Approximately: ,in, This refers to the angular interval between two adjacent rotational samplings of the ultrasonic array probe. It is the height interval between two adjacent longitudinal height measuring points, that is, the distance between the corresponding measuring points of adjacent array elements in the axial direction of the tower; The corrosion area percentage is then corrected to: Next, the roughness of the inner surface is evaluated using the undulation of the inner wall radius; let... For measuring points The local neighborhood of the surrounding area, the average radius of the inner wall within that neighborhood. for: The local roughness at that location for: The maximum roughness of the detection area is: Increase average multi-angle confirmation: in, To prevent the stability coefficient from having a denominator of zero, This indicates the average multi-angle confirmation of the effective corrosion area; Finally, a comprehensive evaluation index for corrosion status was established by taking into account the thickness reduction rate, corrosion area ratio, inner wall roughness, and average multi-angle confirmation degree. for: in, , , , Let be the weighting coefficient, and satisfy: ; The allowable roughness of the inner wall or the experimentally calibrated roughness; Based on comprehensive evaluation indicators The corrosion state is divided into four levels, among which Class I slight corrosion. Class II moderate corrosion Class III severe corrosion. It is classified as Class IV hazardous corrosion; its determination function is: in, , , The corrosion level threshold is determined through experimental calibration, on-site testing experience, or tower design safety requirements.

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