Nonlinear ultrasonic concrete damage monitoring method based on distributed sensors and application thereof

Abstract

The application provides a kind of nonlinear ultrasonic concrete damage monitoring method and application based on distributed sensor, and is specifically related to material monitoring technical field.The monitoring method comprises the following steps:S1, the position of transmitting node and receiving node is defined;S2, piezoelectric ceramic sensor is arranged at corresponding node respectively, and wireless distributed sensor network is formed;S3, ultrasonic wave in the concrete structure to be monitored is excited;S4, ultrasonic response signal is received and sent to main control processing system by wireless communication mode;S5, the signal time-frequency spectrogram of each acoustic path is obtained, and the nonlinear characteristic parameters of the second harmonic in each signal time-frequency spectrogram are extracted;S6, the damage image inside the concrete structure to be monitored is constructed, and the positioning evaluation of damage area is realized;S7, historical data is established by regular monitoring, and early warning of structure deterioration process is realized.Compared with traditional centralized sensor arrangement, the application has strong micro-damage identification ability and high analysis precision, and is suitable for long-term monitoring and early warning of concrete structure health state.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material monitoring, and particularly relates to a nonlinear ultrasonic concrete damage monitoring method based on a distributed sensor. BACKGROUND

[0002] Concrete structures are widely used in civil engineering, transportation, water conservancy and other fields, and are prone to produce micro-cracks, debonding, carbonation and other damages during long-term service. The traditional linear ultrasonic monitoring method has limited ability to identify early micro-damage. In recent years, the nonlinear ultrasonic monitoring technology has gradually become a research hotspot for monitoring micro-damage of concrete due to its high sensitivity to nonlinear changes of materials. However, the existing nonlinear ultrasonic method mostly relies on centralized sensor arrangement, and cannot realize large-scale, multi-point and real-time structure state monitoring. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the present application provides a nonlinear ultrasonic concrete damage monitoring method based on a distributed sensor, and the specific technical solutions are as follows.

[0004] A nonlinear ultrasonic concrete damage monitoring method based on a distributed sensor, specifically comprising the following steps:

[0005] S1. Defining the positions of four corners of one surface of the concrete structure to be monitored as a transmitting node, a first receiving node, a second receiving node and a third receiving node, respectively;

[0006] S2. Setting a first piezoelectric ceramic sensor as a signal excitation end at the transmitting node, and setting second piezoelectric ceramic sensors as signal receiving ends at the first receiving node, the second receiving node and the third receiving node, to form a wireless distributed sensor network;

[0007] S3. Using the first piezoelectric ceramic sensor to transmit a pulse signal to excite ultrasonic waves in the concrete structure to be monitored;

[0008] S4. The three second piezoelectric ceramic sensors simultaneously receive ultrasonic response signals and send them to a master control processing system through a wireless communication mode;

[0009] S5. The master control processing system performs short-time Fourier transform analysis on the received response signals, obtains the signal time-frequency spectrum of each sound path, and extracts the nonlinear characteristic parameters of the second harmonic at each time in each signal time-frequency spectrum;

[0010] S6. Based on the nonlinear characteristic parameters obtained in S5, a damage image of the interior of the concrete structure to be monitored is constructed according to a time-distance mapping, and the positioning evaluation of the damage area is realized;

[0011] S7. Regularly monitor and establish the nonlinear response history data at each node, compare the trend of nonlinear index over time, and realize early warning of the deterioration process of the concrete structure to be monitored.

[0012] Preferably, in S2, the first piezoelectric ceramic sensor comprises 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 module; and the second piezoelectric ceramic sensor comprises an oscilloscope module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module and a power module.

[0013] Preferably, in S3, the range value of the pulse signal emitted by the first piezoelectric ceramic sensor is 200-800Vpp.

[0014] Preferably, in S4, the master control processing system is provided with a short-time Fourier analysis module, a damage positioning module and a nonlinear parameter extraction module; and the first piezoelectric ceramic sensor and the second piezoelectric ceramic sensor both realize data transmission with the master control processing system through the wireless communication module.

[0015] Further preferably, in S5, the nonlinear characteristic parameters of the second harmonic include a second harmonic-fundamental amplitude ratio, a characteristic frequency intensity ratio and a harmonic growth rate.

[0016] The calculation formula of the second harmonic-fundamental amplitude ratio is:

[0017] ;

[0018] In the formula, is the second harmonic-fundamental amplitude ratio; is the change of the second harmonic amplitude at 2ω over time; is the change of the square of the fundamental amplitude at ω over time;

[0019] The calculation formula of the characteristic frequency intensity ratio is:

[0020] ;

[0021] In the formula, is the characteristic frequency intensity ratio; is the change of the amplitude of the highest frequency component in the signal other than the fundamental at ω over time; is the change of the fundamental amplitude at ω over time;

[0022] The calculation formula of the harmonic growth rate is:

[0023] ;

[0024] In the formula, is the harmonic growth rate; is the propagation distance of the second harmonic.

[0025] Further 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 , , , ;

[0026] The concrete structure to be monitored is discretized into a series of equidistant two-dimensional spatial points, and the ultrasonic propagation time from each point in the concrete structure to be monitored to , , , , is calculated:

[0027] ;

[0028] wherein, ; is the sound velocity of the ultrasonic wave in the concrete;

[0029] According to the time-distance mapping, any one of the three types of nonlinear characteristic parameters, i.e., the amplitude ratio of the second harmonic to the fundamental wave, the characteristic frequency intensity ratio or the harmonic growth rate, is projected onto the space, and the following corresponding formula is used to obtain the coordinate values of each point of the damage image of the concrete structure to be monitored, and an interpolation algorithm or an imaging reconstruction algorithm is used to generate the damage image of the internal concrete structure to be monitored corresponding to the nonlinear characteristic parameter:

[0030] wherein, the coordinate calculation formula corresponding to the amplitude ratio of the second harmonic to the fundamental wave is:

[0031] ;

[0032] The coordinate calculation formula corresponding to the characteristic frequency intensity ratio is:

[0033] ;

[0034] The coordinate calculation formula corresponding to the harmonic growth rate is:

[0035] ;

[0036] wherein, is the coordinate corresponding to the amplitude ratio of the second harmonic to the fundamental wave; is the coordinate corresponding to the characteristic frequency intensity ratio; is the coordinate corresponding to the harmonic growth rate;

[0037] wherein, in the damage image obtained by using the amplitude ratio of the second harmonic to the fundamental wave or the characteristic frequency intensity ratio, the amplitude ratio of the second harmonic to the fundamental wave 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.

[0038] 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.

[0039] The beneficial effects of this invention are:

[0040] 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.

[0041] 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

[0042] The accompanying drawings constituting this invention are provided to further understand this application and do not constitute an undue limitation of this application.

[0043] Figure 1 A system framework diagram of the monitoring method provided by the present invention;

[0044] Figure 2 This is a schematic diagram of the nonlinear ultrasonic signal spectrum in an example of the present invention;

[0045] Figure 3 This is a schematic diagram of the damage image results obtained in an example of the present invention. Detailed Implementation

[0046] 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.

[0047] A nonlinear ultrasonic concrete damage monitoring method based on distributed sensors specifically includes the following steps:

[0048] S1. Define the four corner positions of one surface of the concrete structure to be monitored as a transmitting node, a first receiving node, a second receiving node and a third receiving node, as shown in Figure 1

[0049] S2. Set a first piezoelectric ceramic sensor as a signal excitation end at the transmitting node; set second piezoelectric ceramic sensors as signal receiving ends at the first receiving node, the second receiving node and the third receiving node, to form a wireless distributed sensing network;

[0050] Preferably, the first piezoelectric ceramic sensor comprises 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 module; and the second piezoelectric ceramic sensor comprises an oscilloscope module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module and a power module, which is different from the first piezoelectric ceramic sensor.

[0051] Preferably, the power module adopts solar energy or super-long storage lithium battery.

[0052] S3. Use the first piezoelectric ceramic sensor to transmit a pulse signal to excite an ultrasonic wave in the concrete structure to be monitored;

[0053] Preferably, the first piezoelectric ceramic sensor transmits a pulse signal with a range value of 200-800Vpp to excite possible nonlinear effects in the concrete structure to be monitored, such as high-order harmonic and subharmonic phenomena at micro-cracks.

[0054] S4. The three second piezoelectric ceramic sensors simultaneously receive ultrasonic response signals and send them to a master control processing system through wireless communication; wherein the master control processing system is provided with a short-time Fourier analysis module, a damage positioning module and a nonlinear parameter extraction module; the first piezoelectric ceramic sensor and the second piezoelectric ceramic sensor both realize data transmission with the master control processing system through the wireless communication module.

[0055] S5. The master control processing system performs short-time Fourier transform analysis on the received response signals, obtains the signal time-frequency spectrum of each acoustic path, and extracts the nonlinear characteristic parameters of the second harmonic at each time in each signal time-frequency spectrum, including the second harmonic-to-fundamental amplitude ratio, the characteristic frequency intensity ratio and the harmonic growth rate.

[0056] The calculation formula of the second harmonic-to-fundamental amplitude ratio is:

[0057] ;

[0058] In the formula, A2ω is the second harmonic-to-fundamental amplitude ratio; is the second harmonic-to-fundamental amplitude ratio; is the change of the second harmonic amplitude at 2ω with time.​ is the square of the fundamental amplitude at ω as a function of time;

[0059] The characteristic frequency intensity ratio is calculated as:

[0060] ;

[0061] wherein, is the characteristic frequency intensity ratio; is the amplitude of the highest frequency component in the signal other than the fundamental at ω as a function of time; is the fundamental amplitude at ω as a function of time;

[0062] The harmonic growth rate is calculated as:

[0063] ;

[0064] wherein, is the harmonic growth rate; is the propagation distance of the second harmonic.

[0065] S6. Based on the nonlinear characteristic parameters obtained in S5, a damage image inside the concrete structure to be monitored is constructed according to a time-distance mapping, so as to realize positioning evaluation of a damage area;

[0066] Specifically, the coordinates of the transmitting node, the first receiving node, the second receiving node and the third receiving node are defined as , , , ;

[0067] The concrete structure to be monitored is discretized into a series of equidistant two-dimensional space points, and the ultrasonic propagation time from each point to , , , of the concrete structure to be monitored is calculated:

[0068] ;

[0069] wherein, ; is the sound velocity of the ultrasonic wave in the concrete;

[0070] When in use, according to different requirements of assessment on the severity and concentration of damage, according to the time-distance mapping, any one of three kinds of nonlinear characteristic parameters of the amplitude ratio of the second harmonic to the fundamental wave or the characteristic frequency intensity ratio or the harmonic growth rate is selected to be projected onto the space, and the coordinate values of each point of the damage image of the monitored concrete structure are obtained by using the following corresponding formula, and the interpolation algorithm or the imaging reconstruction algorithm is used to generate the damage images of the structure inside obtained from the different nonlinear characteristic parameters:

[0071] The coordinate calculation formula corresponding to the amplitude ratio of the second harmonic to the fundamental wave is:

[0072] ;

[0073] The coordinate calculation formula corresponding to the characteristic frequency intensity ratio is:

[0074] ;

[0075] The coordinate calculation formula corresponding to the harmonic growth rate is:

[0076] ;

[0077] In the formula, is the coordinate corresponding to the amplitude ratio of the second harmonic to the fundamental wave; is the coordinate corresponding to the characteristic frequency intensity ratio; is the coordinate corresponding to the harmonic growth rate;

[0078] In the damage image obtained by using the amplitude ratio of the second harmonic to the fundamental wave or the characteristic frequency intensity ratio, the area with a higher value of the amplitude ratio of the second harmonic to the fundamental wave or the characteristic frequency intensity ratio represents a more serious damage condition; in the damage image obtained by using the harmonic growth rate, the area with a higher value of the harmonic growth rate represents a more concentrated damage area.

[0079] S7. The system periodically monitors and establishes the historical data of the nonlinear response at each node, compares the change trend of the nonlinear index over time, and realizes early warning of the deterioration process of the monitored concrete structure.

[0080] An application of nonlinear ultrasonic concrete damage based on distributed sensors, which mainly applies to the health monitoring of the concrete base structure of a power transmission tower, adopts the monitoring method described above.

[0081] In order to better understand the monitoring method provided by the present application, the following specific examples are used for illustration:

[0082] It is worth noting that the amplitude ratio of the second harmonic to the fundamental wave is selected in this example to generate the damage image of the concrete structure:​​​

[0083] The embodiment is directed to a steel structure electric tower in a mountainous power transmission line. The base of the electric tower is a reinforced concrete structure, which is affected by temperature difference, load vibration and freeze-thaw alternation for a long time, and has a risk of developing micro-cracks. The target is to realize early identification, positioning and evaluation of hidden damage in the base structure, and to meet the demand of remote wireless monitoring.

[0084] The size of the concrete structure is 20m x 20m x 2m, wherein 10 pieces of plexiglass slices with a thickness of 2mm are embedded in a region of 0.5m x 0.5m x 0.5m as crack defects.

[0085] The top surface of the electric tower base is numbered as P1-P4, wherein P1 node is selected as the transmitting node, P2-P4 nodes are respectively selected as three receiving nodes, and the node spacing between the nodes at the two ends of the diagonal line is 14m. A first piezoelectric ceramic sensor is arranged at the P1 node; second piezoelectric ceramic sensors are arranged at the P2-P4 nodes.

[0086] 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 assembly.

[0087] The three second 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, a lithium battery and a solar panel power supply assembly. All sensors are connected to the master control processing system of the base station through the wireless Wi-Fi communication module to realize wireless data transmission.

[0088] During monitoring, the signal generator in the first piezoelectric ceramic sensor generates a 25kHz Hanning window modulated 10-period sine pulse signal and amplifies it to 600Vpp via the power amplifier to drive the piezoelectric ceramic sheet to form an ultrasonic wave into the concrete structure. The P2-P4 nodes synchronously collect the propagation signals (sampling at 1μs intervals), record the response signals received by the piezoelectric ceramic sheet through the oscilloscope module, and send the original signals to the master control processing system in the form of data packets through the wireless Wi-Fi communication module. The master control processing system performs short-time Fourier transform on the collected signals to generate a signal time-frequency spectrum, as shown in Figure 2 Figure 2 ​a signal time-frequency spectrogram of one of the three sound paths), where the horizontal axis is time, the vertical axis is frequency, the black area represents the amplitude of the signal at the corresponding time point and corresponding frequency, ω represents the excitation frequency of the ultrasonic wave, and 2ω represents the frequency of the second harmonic. The second harmonic-to-fundamental amplitude at each time point can be extracted from the signal time-frequency spectrogram.

[0089] The second harmonic-to-fundamental amplitude ratio at each time point on each sound path is calculated using the following formula:

[0090] ;

[0091] The coordinates of the transmitting node, the first receiving node, the second receiving node, and the third receiving node are defined as , , , respectively. The two-dimensional space of the concrete structure to be monitored is discretized at intervals of 10 mm, and the ultrasonic propagation time from each point to the transmitting node and the receiving nodes , , is calculated using the following formula:

[0092] ;

[0093] where is the speed of sound in the concrete structure, which is 3017 m / s in this example. The second harmonic-to-fundamental amplitude ratio is projected onto the space according to the time-distance mapping, and the coordinate values 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 the internal damage image of the structure, as shown in Figure 3 :

[0094] ;

[0095] Figure 3 In this case, the darker the black color, the higher the second harmonic-to-fundamental amplitude ratio, i.e., the higher the damage degree at that location; at this time, the host processing system will automatically mark its position coordinates and nonlinear characteristic parameters. Based on the above method, the base station terminal detects once a day and stores the monitoring data for later tracking analysis of the structure degradation trend.

[0096] In the present application, the terms such as "upper", "lower", "bottom", "top" and the like indicate the orientation or positional relationship shown in the drawings, which are only the relationship words determined for the convenience of describing the structural relationship of the components or elements of the present application, and are not intended to specify any component or element in the present application, and cannot be understood as a limitation on the present application. The terms such as "connected", "connected" and the like should be understood broadly, which means that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. For relevant researchers or technicians in the field, the specific meaning of the above terms in the present application can be determined according to the specific circumstances, and cannot be understood as a limitation on the present application.

[0097] Of course, the above description is not a limitation on the present application, and the present application is also not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present application should also be within the scope of the present application.

Claims

1. A method for nonlinear ultrasonic concrete damage monitoring based on distributed sensors, characterized in that, Specifically comprising the following steps: S1. Define the four corner positions of one surface of the concrete structure to be monitored as a transmitting node, a first receiving node, a second receiving node and a third receiving node respectively; S2. Set a first piezoelectric ceramic sensor as a signal excitation end at the transmitting node; Set a second piezoelectric ceramic sensor as a signal receiving end at the first receiving node, the second receiving node and the third receiving node to form a wireless distributed sensing network; In S2, the first piezoelectric ceramic sensor comprises 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 module; the second piezoelectric ceramic sensor comprises an oscilloscope module, a piezoelectric ceramic sheet, a signal conditioning circuit, a microprocessor, a wireless communication module and a power module; S3. Use the first piezoelectric ceramic sensor to transmit a pulse signal to excite ultrasonic waves in the concrete structure to be monitored; In S3, the range of the pulse signal transmitted by the first piezoelectric ceramic sensor is 200-800Vpp; S4. The three second piezoelectric ceramic sensors simultaneously receive ultrasonic response signals and send them to the master processing system through wireless communication; S5. The master processing system performs short-time Fourier transform analysis on the received response signals, obtains the signal time-frequency spectrum of each sound path, and extracts the nonlinear characteristic parameters of the second harmonic at each time in each signal time-frequency spectrum; S6. Based on the nonlinear characteristic parameters obtained in S5, according to the time-distance mapping, the damage image inside the concrete structure to be monitored is constructed to realize the positioning evaluation of the damage area; S7. Regularly monitor and establish the historical data of the nonlinear response at each node, compare the change trend of the nonlinear characteristic parameters with time, and realize early warning of the deterioration process of the concrete structure to be monitored.

2. The method of claim 1, wherein the method is based on distributed sensor nonlinear ultrasonic concrete damage monitoring. In S4, the master processing system is provided with a short-time Fourier analysis module, a damage positioning module and a nonlinear parameter extraction module; The first piezoelectric ceramic sensor and the second piezoelectric ceramic sensor both realize data transmission with the master processing system through the wireless communication module.

3. The method of claim 2, wherein the method is based on distributed sensor nonlinear ultrasonic concrete damage monitoring. In S5, the nonlinear characteristic parameters of the second harmonic include the amplitude ratio of the second harmonic to the fundamental wave, the characteristic frequency intensity ratio and the harmonic growth rate; The calculation formula of the amplitude ratio of the second harmonic to the fundamental wave is: ； wherein is the second harmonic-to-fundamental amplitude ratio; is the variation of the second harmonic amplitude at 2ω with time; is the variation of the square of the fundamental amplitude at ω with time; The calculation formula of the characteristic frequency intensity ratio is: ； wherein is the characteristic frequency strength ratio; is the amplitude of the highest frequency component in the signal other than the fundamental at ω as a function of time; is the amplitude of the fundamental at ω as a function of time; The calculation formula of the harmonic growth rate is: ； wherein is the harmonic growth rate; is the propagation distance of the second harmonic.

4. The method of claim 3, wherein the method is based on distributed sensor nonlinear ultrasonic concrete damage monitoring. In S6, coordinates of the transmitting node, the first receiving node, the second receiving node and the third receiving node are defined as , , , ; The concrete structure to be monitored is discretized into a series of equidistant two-dimensional spatial points, and the spatial propagation time of ultrasound to each point of the concrete structure to be monitored is calculated to , , , ultrasound propagation time ； wherein ; is the speed of sound of the ultrasonic waves in the concrete; According to the time-distance mapping, any one of the three types of nonlinear characteristic parameters, i.e. the amplitude ratio of the second harmonic to the fundamental wave, the characteristic frequency intensity ratio or the harmonic growth rate, is projected onto the space, and the coordinate values of each point of the damage image of the concrete structure to be monitored are obtained by using the following corresponding formula, and the interpolation algorithm or the imaging reconstruction algorithm is used to generate the damage image inside the concrete structure to be monitored corresponding to the nonlinear characteristic parameters: The coordinate calculation formula corresponding to the amplitude ratio of the second harmonic to the fundamental wave is: ； The coordinate calculation formula corresponding to the characteristic frequency intensity ratio is: ； The coordinate calculation formula corresponding to the harmonic growth rate is: ； wherein is the coordinate corresponding to the second harmonic-to-fundamental amplitude ratio; is the coordinate corresponding to the characteristic frequency intensity ratio; is the coordinate corresponding to the harmonic growth rate; In the damage image obtained by using the second harmonic-to-fundamental amplitude ratio or the characteristic frequency intensity ratio, the second harmonic-to-fundamental amplitude ratio or the characteristic frequency intensity ratio The higher the value in the area, the more serious the damage condition is; in the damage image obtained by using the harmonic growth rate, the harmonic growth rate The higher the value in the area, the more concentrated the damage occurs.

5. An application of distributed sensor based nonlinear ultrasonic concrete damage, using the monitoring method of claim 4, characterized in that, It is suitable for health monitoring of concrete base structures of power transmission towers.

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