Nonlinear ultrasonic concrete damage monitoring method based on distributed sensor and application

Abstract

The invention provides a nonlinear ultrasonic concrete damage monitoring method based on distributed sensors and application, and particularly relates to the technical field of material monitoring. The monitoring method comprises the following steps: S1, defining the positions of a transmitting node and a receiving node; s2, piezoelectric ceramic sensors are arranged at the corresponding nodes respectively, and a wireless distributed sensing network is formed; s3, exciting ultrasonic waves in the concrete structure to be monitored; s4, receiving the ultrasonic response signal and sending the ultrasonic response signal to the main control processing system in a wireless communication mode; s5, obtaining a signal time-frequency spectrogram of each sound path and extracting nonlinear characteristic parameters of second harmonics in each signal time-frequency spectrogram; s6, constructing a damage image of the interior of the to-be-monitored concrete structure, and realizing positioning evaluation of a damage area; and S7, regularly monitoring and establishing historical data to realize early warning of the structure degradation process. Compared with traditional centralized sensor arrangement, the method is high in micro-damage identification capability, high in analysis precision and suitable for long-term monitoring and early warning of the health state of the concrete structure.

Description

Technical Field

[0001] This invention relates to the field of materials monitoring technology, specifically to a method for monitoring nonlinear ultrasonic concrete damage based on distributed sensors. Background Technology

[0002] Concrete structures are widely used in civil engineering, transportation, water conservancy, and other fields. During long-term service, they are prone to damage such as micro-cracks, debonding, and carbonation. Traditional linear ultrasonic monitoring methods have limited ability to identify early-stage micro-damage. In recent years, nonlinear ultrasonic monitoring technology has gradually become a research hotspot for concrete micro-damage monitoring due to its high sensitivity to nonlinear changes in materials. However, most existing nonlinear ultrasonic methods rely on centralized sensor deployments, making it impossible to achieve large-scale, multi-point, real-time structural condition monitoring. Summary of the Invention

[0003] To overcome the shortcomings of the prior art, this invention provides a nonlinear ultrasonic concrete damage monitoring method based on distributed sensors, the specific technical solution of which is as follows: A nonlinear ultrasonic concrete damage monitoring method based on distributed sensors specifically includes the following steps: S1. Define the four corners of one surface of the concrete structure to be monitored as the transmitting node, the first receiving node, the second receiving node, and the third receiving node, respectively; S2. A first piezoelectric ceramic sensor is set at the transmitting node as a signal excitation end; a second piezoelectric ceramic sensor is set at the first receiving node, the second receiving node and the third receiving node as a signal receiving end, forming a wireless distributed sensor network; S3. Use the first piezoelectric ceramic sensor to emit a pulse signal to excite ultrasonic waves in the concrete structure to be monitored; S4. The three second piezoelectric ceramic sensors simultaneously receive ultrasonic response signals and transmit them to the main control processing system via wireless communication; S5. The main control processing system performs short-time Fourier transform analysis on the received response signal to obtain the signal time spectrum of each acoustic path, and extracts the nonlinear characteristic parameters of the second harmonic at each moment in the signal time spectrum. S6. Based on the nonlinear feature parameters obtained in S5, a damage image of the interior of the concrete structure to be monitored is constructed according to the time-distance mapping to realize the location assessment of the damage area; S7. Regularly monitor and establish historical data of nonlinear response at each node, compare the changing trends of nonlinear indicators over time, and achieve early warning of the deterioration process of the monitored concrete structure.

[0004] Preferably, in S2, the first piezoelectric ceramic sensor includes a signal generator module, a power amplifier module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module, and a power supply module; the second piezoelectric ceramic sensor includes an oscilloscope module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module, and a power supply module.

[0005] Preferably, in S3, the range of the pulse signal emitted by the first piezoelectric ceramic sensor is 200–800 Vpp.

[0006] Preferably, in S4, the main control processing system is equipped with a short-time Fourier analysis module, a damage localization module, and a nonlinear parameter extraction module; both the first piezoelectric ceramic sensor and the second piezoelectric ceramic sensor realize data transmission with the main control processing system through a wireless communication module.

[0007] Preferably, in S5, the nonlinear characteristic parameters of the second harmonic include the second harmonic-fundamental amplitude ratio, the characteristic frequency intensity ratio, and the harmonic growth rate. The formula for calculating the second harmonic-fundamental amplitude ratio is as follows: ; In the formula, The ratio of the second harmonic amplitude to the fundamental amplitude; It is the change of the second harmonic amplitude at 2ω over time; It is the change of the square of the fundamental wave amplitude at ω over time; The formula for calculating the characteristic frequency intensity ratio is: ; In the formula, The ratio of characteristic frequency intensity; It is the change in amplitude of the highest frequency component in the signal other than the fundamental wave at ω over time; It represents the change of the fundamental amplitude at ω over time; The formula for calculating the harmonic growth rate is: ; In the formula, The harmonic growth rate; It is the propagation distance of the second harmonic.

[0008] More preferably, in S6, the coordinates of the transmitting node, the first receiving node, the second receiving node, and the third receiving node are defined as follows: , , , ; The concrete structure to be monitored is discretized into a series of equally spaced two-dimensional spatial points, and the values ​​of each point in the space of the concrete structure to be monitored are calculated. arrive , , , Ultrasonic propagation time: ; In the formula, ; The velocity of ultrasound in concrete; Based on the time-distance mapping, any one of three nonlinear characteristic parameters—the amplitude ratio of the second harmonic to the fundamental wave, the characteristic frequency intensity ratio, or the harmonic growth rate—is projected onto space. The coordinate values ​​of each point in the damage image of the concrete structure to be monitored are obtained using the following corresponding formula. An interpolation algorithm or an imaging reconstruction algorithm is then used to generate damage images of the interior of the concrete structure to be monitored with the corresponding nonlinear characteristic parameters: The formula for calculating the coordinates corresponding to the second harmonic-fundamental amplitude ratio is as follows: ; The formula for calculating the coordinates corresponding to the characteristic frequency intensity ratio is: ; The formula for calculating the coordinates corresponding to the harmonic growth rate is: ; In the formula, The coordinates corresponding to the second harmonic-fundamental amplitude ratio; The coordinates corresponding to the characteristic frequency intensity ratio; The coordinates corresponding to the harmonic growth rate; Among them, in the damage images obtained using the second harmonic-fundamental amplitude ratio or the characteristic frequency intensity ratio, the second harmonic-fundamental amplitude ratio... or characteristic frequency intensity ratio The higher the value, the more severe the damage; in the damage image obtained using the harmonic growth rate, the harmonic growth rate... The higher the elevation, the more concentrated the damage occurred.

[0009] An application of nonlinear ultrasonic concrete damage based on distributed sensors is presented. The monitoring method described above is suitable for health monitoring of concrete foundation structures of transmission towers.

[0010] The beneficial effects of this invention are: Compared to traditional centralized sensor monitoring methods, this invention utilizes high-amplitude excitation and short-time Fourier transform analysis to extract the second harmonic nonlinear response caused by early damage such as microcracks and debonding in concrete structures, significantly improving the ability to identify micro-damage. This invention also uses piezoelectric ceramic sensor nodes with wireless communication capabilities to construct a distributed sensor network, which not only facilitates flexible deployment in large or complex structures but also avoids the construction difficulties caused by traditional wiring.

[0011] Furthermore, this invention supports spatial imaging and damage visualization based on nonlinear characteristics, enabling precise location of damaged areas and intuitive assessment of the degree of damage. Simultaneously, the system supports multi-node periodic data acquisition and remote data transmission, facilitating the establishment of a historical database and enabling trend identification and early warning of structural health. Attached Figure Description

[0012] The accompanying drawings constituting this invention are provided to further understand this application and do not constitute an undue limitation of this application.

[0013] Figure 1 A system framework diagram of the monitoring method provided by the present invention; Figure 2 This is a schematic diagram of the nonlinear ultrasonic signal spectrum in an example of the present invention; Figure 3 This is a schematic diagram of the damage image results obtained in an example of the present invention. Detailed Implementation

[0014] The specific implementation of the nonlinear ultrasonic concrete damage monitoring method based on distributed sensors provided by the present invention will be further described with reference to the accompanying drawings and embodiments.

[0015] A nonlinear ultrasonic concrete damage monitoring method based on distributed sensors specifically includes the following steps: S1. Define the four corners of one surface of the concrete structure to be monitored as the transmitting node, the first receiving node, the second receiving node, and the third receiving node, respectively. Figure 1 As shown; S2. A first piezoelectric ceramic sensor is set at the transmitting node as a signal excitation end; a second piezoelectric ceramic sensor is set at the first receiving node, the second receiving node and the third receiving node as a signal receiving end, forming a wireless distributed sensor network; Preferably, the first piezoelectric ceramic sensor includes a signal generator module, a power amplifier module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module, and a power supply module; unlike the first piezoelectric ceramic sensor, the second piezoelectric ceramic sensor includes an oscilloscope module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module, and a power supply module.

[0016] Preferably, the power module uses a solar-powered or ultra-long-lasting lithium battery.

[0017] S3. Use the first piezoelectric ceramic sensor to emit a pulse signal to excite ultrasonic waves in the concrete structure to be monitored; Preferably, the pulse signal emitted by the first piezoelectric ceramic sensor is in the range of 200 to 800 Vpp, so as to excite nonlinear effects that may exist in the concrete structure to be monitored, such as high-order harmonics and subharmonics at microcracks.

[0018] S4. The three second piezoelectric ceramic sensors simultaneously receive ultrasonic response signals and transmit them to the main control processing system via wireless communication; wherein, the main control processing system is equipped with a short-time Fourier analysis module, a damage localization module, and a nonlinear parameter extraction module; the first and second piezoelectric ceramic sensors both realize data transmission with the main control processing system through wireless communication modules.

[0019] S5. The main control processing system performs short-time Fourier transform analysis on the received response signal to obtain the signal time spectrum of each acoustic path, and extracts the nonlinear characteristic parameters of the second harmonic at each moment in the signal time spectrum, including the second harmonic-fundamental amplitude ratio, characteristic frequency intensity ratio, and harmonic growth rate. The formula for calculating the second harmonic-fundamental amplitude ratio is as follows: ; In the formula, The ratio of the second harmonic amplitude to the fundamental amplitude; It is the change of the second harmonic amplitude at 2ω over time; It is the change of the square of the fundamental wave amplitude at ω over time; The formula for calculating the characteristic frequency intensity ratio is: ; In the formula, The ratio of characteristic frequency intensity; It is the change in amplitude of the highest frequency component in the signal other than the fundamental wave at ω over time; It represents the change of the fundamental amplitude at ω over time; The formula for calculating the harmonic growth rate is: ; In the formula, The harmonic growth rate; It is the propagation distance of the second harmonic.

[0020] S6. Based on the nonlinear feature parameters obtained in S5, a damage image of the interior of the concrete structure to be monitored is constructed according to the time-distance mapping to realize the location assessment of the damage area; Specifically, the coordinates of the transmitting node, the first receiving node, the second receiving node, and the third receiving node are defined as follows: , , , ; The concrete structure to be monitored is discretized into a series of equally spaced two-dimensional spatial points, and the values ​​of each point in the space of the concrete structure to be monitored are calculated. arrive , , , Ultrasonic propagation time: ; In the formula, ; The velocity of ultrasound in concrete; In practice, depending on the need for assessing the severity and concentration of damage, and based on time-distance mapping, any one of three nonlinear characteristic parameters—the amplitude ratio of the second harmonic to the fundamental wave, the characteristic frequency intensity ratio, or the harmonic growth rate—is projected onto space. The coordinates of each point in the damage image of the concrete structure under monitoring are then obtained using the following corresponding formula. Interpolation algorithms or imaging reconstruction algorithms can then be used to generate three damage images of the structure's interior obtained from different nonlinear characteristic parameters: The formula for calculating the coordinates corresponding to the second harmonic-fundamental amplitude ratio is as follows: ; The formula for calculating the coordinates corresponding to the characteristic frequency intensity ratio is: ; The formula for calculating the coordinates corresponding to the harmonic growth rate is: ; In the formula, The coordinates corresponding to the second harmonic-fundamental amplitude ratio; The coordinates corresponding to the characteristic frequency intensity ratio; The coordinates corresponding to the harmonic growth rate; Among them, in the damage images obtained using the second harmonic-fundamental amplitude ratio or the characteristic frequency intensity ratio, the second harmonic-fundamental amplitude ratio... or characteristic frequency intensity ratio The higher the value, the more severe the damage; in the damage image obtained using the harmonic growth rate, the harmonic growth rate... The higher the elevation, the more concentrated the damage occurred.

[0021] S7. Systematically and periodically monitor and establish historical data of nonlinear response at each node, compare the changing trends of nonlinear indicators over time, and achieve early warning of the deterioration process of the monitored concrete structure.

[0022] An application of nonlinear ultrasonic concrete damage based on distributed sensors, using the above-mentioned monitoring method, is mainly applicable to the health monitoring of concrete foundation structures of transmission towers.

[0023] To better understand the monitoring method provided by this invention, specific embodiments are described below: It is worth noting here that this example uses the second harmonic-fundamental amplitude ratio as the parameter to generate damage images of concrete structures: This embodiment focuses on a steel-structured power tower in a mountainous transmission line. Its base is a reinforced concrete structure, subject to long-term exposure to temperature differences, load vibrations, and freeze-thaw cycles, posing a risk of microcrack development. The objective is to achieve early identification, location, and assessment of hidden damage within the base structure, while also meeting the requirements for remote wireless monitoring.

[0024] The concrete structure measures 20m × 20m × 2m, with 10 2mm thick acrylic sheets embedded within a 0.5m × 0.5m × 0.5m area to represent crack defects.

[0025] The four corners of the top surface of the power tower base are numbered P1 to P4. Node P1 is selected as the transmitting node, and nodes P2 to P4 are designated as three receiving nodes, with a node spacing of 14m between the two ends of the diagonal. A first piezoelectric ceramic sensor is installed at node P1; second piezoelectric ceramic sensors are installed at nodes P2 to P4.

[0026] The first piezoelectric ceramic sensor of the transmitting node includes: a piezoelectric ceramic sheet with a center frequency of 25kHz, a signal conditioning circuit, a signal generator module, a power amplifier module, a wireless Wi-Fi communication module, an STM32 low-power microprocessor, a lithium battery, and a solar panel power supply component.

[0027] The three secondary piezoelectric ceramic sensors include: a piezoelectric ceramic sheet with a center frequency of 50kHz, a signal conditioning circuit, an oscilloscope module for signal acquisition, a wireless Wi-Fi communication module, an STM32 low-power microprocessor, and a lithium battery and solar panel power supply assembly. All sensors are connected to the base station's main control processing system via the wireless Wi-Fi communication module to achieve wireless data transmission.

[0028] During monitoring, a 10-cycle sinusoidal pulse signal modulated with a 25kHz Hanning window is generated by the signal generator in the first piezoelectric ceramic sensor and amplified to 600Vpp by a power amplifier to drive the piezoelectric ceramic sheet to inject ultrasonic waves into the concrete structure. Nodes P2 to P4 synchronously acquire the propagation signal (sampled at 1μs intervals). The response signal received by the piezoelectric ceramic sheet is recorded by an oscilloscope module. The raw signal is then transmitted to the main control processing system in the form of data packets via a wireless Wi-Fi communication module. The main control processing system performs a short-time Fourier transform on the acquired signal to generate a signal time-frequency spectrum, such as... Figure 2 As shown ( Figure 2 The time-spectrum diagram of one of the three acoustic paths is shown. The horizontal axis represents time, the vertical axis represents frequency, the black area represents the amplitude of the signal at the corresponding time point and frequency, ω represents the excitation frequency of the ultrasound, and 2ω represents the frequency of the second harmonic. The amplitude of the second harmonic-fundamental wave at each moment can be extracted from this time-spectrum diagram.

[0029] The second harmonic-fundamental amplitude ratio at each moment along each sound path can be calculated using the following formula: ; Define the coordinates of the transmitting node, the first receiving node, the second receiving node, and the third receiving node as follows: , , , The two-dimensional space of the concrete structure to be monitored is discretized at 10mm intervals, and the value of each point in the two-dimensional space is calculated using the following formula. To launch node and receiving node , , Ultrasonic propagation time: ; in, This is the velocity of ultrasound in the concrete structure, which is 3017 m / s in this example. Based on the time-distance mapping, the amplitude ratio of the second harmonic to the fundamental wave is projected spatially. The coordinates of each point in the concrete structure damage image are obtained using the following formula, and an interpolation algorithm or imaging reconstruction algorithm is used to generate a damage image of the structure's interior, such as... Figure 3 As shown: ; Figure 3In the diagram, the darker the black, the higher the amplitude ratio of the second harmonic to the fundamental frequency, indicating a higher degree of damage. The main control processing system will automatically mark the location coordinates and nonlinear characteristic parameters at this point. Based on this method, the base station terminal performs a timed excitation detection once daily and simultaneously stores the monitoring data for subsequent tracking and analysis of structural degradation trends.

[0030] In this invention, terms such as "upper," "lower," "bottom," and "top" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are merely used to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any particular component or element in this invention, nor should they be construed as limiting the invention. Terms such as "connected" and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of the above terms in this invention based on the specific circumstances, and they should not be construed as limiting the invention.

[0031] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for monitoring nonlinear ultrasonic concrete damage based on distributed sensors, characterized in that, Specifically, the following steps are included: S1. Define the four corners of one surface of the concrete structure to be monitored as the transmitting node, the first receiving node, the second receiving node, and the third receiving node, respectively; S2. A first piezoelectric ceramic sensor is set at the transmitting node as the signal excitation end; Second piezoelectric ceramic sensors are set at the first receiving node, the second receiving node and the third receiving node as signal receiving ends to form a wireless distributed sensor network. S3. Use the first piezoelectric ceramic sensor to emit a pulse signal to excite ultrasonic waves in the concrete structure to be monitored; S4. The three second piezoelectric ceramic sensors simultaneously receive ultrasonic response signals and transmit them to the main control processing system via wireless communication; S5. The main control processing system performs short-time Fourier transform analysis on the received response signal to obtain the signal time spectrum of each acoustic path, and extracts the nonlinear characteristic parameters of the second harmonic at each moment in the signal time spectrum. S6. Based on the nonlinear feature parameters obtained in S5, a damage image of the interior of the concrete structure to be monitored is constructed according to the time-distance mapping to realize the location assessment of the damage area; S7. Regularly monitor and establish historical data of nonlinear response at each node, compare the changing trends of nonlinear characteristic parameters over time, and achieve early warning of the deterioration process of the monitored concrete structure.

2. The method for monitoring nonlinear ultrasonic concrete damage based on distributed sensors according to claim 1, characterized in that, In S2, the first piezoelectric ceramic sensor includes a signal generator module, a power amplifier module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module, and a power supply module; The second piezoelectric ceramic sensor includes an oscilloscope module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module, and a power supply module.

3. The method for monitoring nonlinear ultrasonic concrete damage based on distributed sensors according to claim 2, characterized in that, In S3, the range of pulse signals emitted by the first piezoelectric ceramic sensor is 200–800 Vpp.

4. The method for monitoring nonlinear ultrasonic concrete damage based on distributed sensors according to claim 3, characterized in that, In S4, the main control processing system is equipped with a short-time Fourier analysis module, a damage localization module, and a nonlinear parameter extraction module; Both the first and second piezoelectric ceramic sensors transmit data to the main control processing system via a wireless communication module.

5. The method for monitoring nonlinear ultrasonic concrete damage based on distributed sensors according to claim 4, characterized in that, In S5, the nonlinear characteristic parameters of the second harmonic include the second harmonic-fundamental amplitude ratio, the characteristic frequency intensity ratio, and the harmonic growth rate. The formula for calculating the second harmonic-fundamental amplitude ratio is as follows: ； In the formula, The ratio of the second harmonic amplitude to the fundamental amplitude; It is the change of the second harmonic amplitude at 2ω over time; It is the change of the square of the fundamental wave amplitude at ω over time; The formula for calculating the characteristic frequency intensity ratio is: ； In the formula, The ratio of characteristic frequency intensity; It is the change in amplitude of the highest frequency component in the signal other than the fundamental wave at ω over time; It represents the change of the fundamental amplitude at ω over time; The formula for calculating the harmonic growth rate is: ； In the formula, The harmonic growth rate; It is the propagation distance of the second harmonic.

6. The method for monitoring nonlinear ultrasonic concrete damage based on distributed sensors according to claim 5, characterized in that, In S6, the coordinates of the transmitting node, the first receiving node, the second receiving node, and the third receiving node are defined as follows: , , , ; The concrete structure to be monitored is discretized into a series of equally spaced two-dimensional spatial points, and the values ​​of each point in the space of the concrete structure to be monitored are calculated. arrive , , , Ultrasonic propagation time: ； In the formula, ; The velocity of ultrasound in concrete; Based on the time-distance mapping, any one of three nonlinear characteristic parameters—the amplitude ratio of the second harmonic to the fundamental wave, the characteristic frequency intensity ratio, or the harmonic growth rate—is projected onto space. The coordinate values ​​of each point in the damage image of the concrete structure to be monitored are obtained using the following corresponding formula. An interpolation algorithm or an imaging reconstruction algorithm is then used to generate damage images of the interior of the concrete structure to be monitored with the corresponding nonlinear characteristic parameters: The formula for calculating the coordinates corresponding to the second harmonic-fundamental amplitude ratio is as follows: ； The formula for calculating the coordinates corresponding to the characteristic frequency intensity ratio is: ； The formula for calculating the coordinates corresponding to the harmonic growth rate is: ； In the formula, The coordinates corresponding to the second harmonic-fundamental amplitude ratio; The coordinates corresponding to the characteristic frequency intensity ratio; The coordinates corresponding to the harmonic growth rate; Among them, in the damage images obtained using the second harmonic-fundamental amplitude ratio or the characteristic frequency intensity ratio, the second harmonic-fundamental amplitude ratio... or characteristic frequency intensity ratio The higher the value, the more severe the damage; in the damage image obtained using the harmonic growth rate, the harmonic growth rate... The higher the elevation, the more concentrated the damage occurred.

7. An application of nonlinear ultrasonic concrete damage based on distributed sensors, employing the monitoring method described in claim 6, characterized in that, Suitable for health monitoring of concrete base structures of transmission towers.

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