Carbon fiber composite material plate damage positioning method and system

Abstract

The invention discloses a carbon fiber composite material plate damage positioning method and system, and belongs to the technical field of composite material damage positioning. The arrival time of the S0 mode and the A0 mode of Lamb waves is obtained, the arrival time of the A0 mode serves as the basis for determining the arrival angle, the time difference between each pair of sensors is determined, and the maximum absolute time difference is determined; for each pair of sensors, obtaining modal time difference of arrival; the sound source arrival angle of the Lamb waves is determined by calculating the minimum absolute value of the time difference; according to the modal time difference of arrival and the obtained modal wave velocities of the S0 and A0 modals, determining the distance between each sensor in the sensor array and a Lamb wave sound source, and determining the average distance between the sound source and each array element; according to the average distance and the sound source arrival angle of the Lamb waves, the coordinate position of the sound source relative to the center point of the sensor array is obtained, and the coordinate position is the position where the damage on the carbon fiber composite material plate is located. The method can realize accurate positioning of the sound source.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material damage location, and more specifically to a carbon fiber composite material plate damage location method and system. Background Art

[0002] Composite materials have broad application prospects in the fields of aviation, automobiles, building structures, etc. due to their high strength-to-weight ratio, corrosion resistance, fatigue resistance and other excellent properties. With the changes in the surrounding environment and the influence of load conditions, the damage and failure problems of composite materials are increasing.

[0003] Lamb waves are elastic guided waves formed by the superposition of ultrasonic waves reflected from the upper and lower free boundaries in a thin plate structure. Compared with traditional transverse and longitudinal waves, Lamb waves are widely used in the field of nondestructive testing and structural health monitoring due to their advantages such as boundary reflection, low attenuation, long detection distance, high detection efficiency, and sensitivity to damage.

[0004] However, the application of Lamb wave-based positioning technology in fields such as materials science, mechanics, and aerospace is very limited, and one-dimensional positioning itself has certain limitations. It requires a large amount of sample data and is prone to large positioning errors when faced with complex structures, multiple sound sources, and inhomogeneous materials. Summary of the invention

[0005] In response to the problems existing in the above-mentioned fields, the present invention proposes a method and system for locating damage of a carbon fiber composite material plate, which collects waveform data of Lamb waves through a triangular sensor array set up on the carbon fiber composite material plate, and combines the characteristics of the material and the wave velocity, accurately calculates the arrival time between the sound source and each sensor, accurately determines its arrival angle, and comprehensively evaluates the distance information between the center point of the triangular array distributed sensor array and the damage position, thereby obtaining the damage position on the carbon fiber composite material plate and realizing accurate positioning of the sound source.

[0006] In order to solve the above technical problems, the present invention discloses a method for locating damage of a carbon fiber composite material plate, comprising the following steps: A triangular sensor array is set up on the carbon fiber composite material plate to obtain the Lamb wave generated on the carbon fiber composite material plate after the lead breaking experiment through the triangular sensor array; By determining the start and end time of the Lamb wave time window, the arrival time of the S0 mode and A0 mode of the Lamb wave are obtained respectively; By obtaining the time difference between each pair of sensors, the maximum absolute time difference is obtained; for each pair of sensors, the ratio of the maximum absolute time difference to the propagation time between the sound source and each sensor is determined to obtain the arrival time difference of the A0 mode; the arrival time of the S0 mode between each pair of sensors is subtracted to determine the arrival time difference of the S0 mode; by calculating the minimum absolute value of the arrival time difference between the S0 mode and the A0 mode, the arrival angle between each sensor and the sound source is determined; Obtain the modal wave velocity of the S0 mode and the A0 mode; determine the relative distance between each sensor and the sound source according to the arrival time and modal wave velocity of the S0 mode and the A0 mode; determine the spacing between the sound source and each sensor according to the arrival angle and relative distance between each sensor and the sound source; According to the distance between the sound source and each sensor, the coordinate position of the sound source relative to the center point of the sensor array is obtained through the triangulation principle. The coordinate position is the location of the damage on the carbon fiber composite material plate.

[0007] Preferably, the step of obtaining the arrival time of the S0 mode of the Lamb wave specifically includes: Select the time window of Lamb wave, calculate the characteristic function CF based on the real part of continuous wavelet transform CWT at a preset frequency, and shorten the time window of the signal according to the global maximum value of the characteristic function CF; In the shortened time window, the AIC function is used to calculate the minimum value of the signal, and the time scale corresponding to the minimum value is obtained, which is the arrival time of the S0 mode.

[0008] Preferably, the step of obtaining the arrival time of the A0 mode of the Lamb wave specifically includes: Filter, denoise and normalize the received Lamb wave signal; The envelope of the signal is calculated by the Hilbert transform method to obtain the instantaneous amplitude of the signal; Calculate the maximum value of the envelope, that is, the peak amplitude of the signal A max , according to the peak amplitude, the secondary threshold is set to two-thirds of the peak value as the limit of the effective signal; Find the critical point in the signal envelope, perform half-sine wave fitting between the second critical point and the next adjacent peak, and generate a half-sine curve representing the change trend of the signal waveform through the fitting algorithm; Find the intersection interval of the half-sine wave and the envelope, and the signal zero-crossing point corresponding to the intersection point in the intersection interval. The zero-crossing point is the moment when the signal waveform changes from positive oscillation to negative oscillation. The extrapolation method is used to locate the zero-crossing point of the half-sine wave, and the time corresponding to the zero-crossing point is the arrival time of the A0 mode.

[0009] Preferably, the acquiring the arrival time difference of the A0 mode specifically includes: A triangular sensor array is established, and the time difference required for the Lamb wave signal to reach each sensor is measured by setting up a triangular sensor array on a carbon fiber composite material plate; According to the propagation characteristics of the A0 mode of Lamb waves, the time difference between each pair of sensors is calculated. ΔT A0; Based on the time difference between each pair of sensors ΔT A0, get the time difference ΔT The corresponding maximum absolute time difference in A0 Δ T A0 max ; For each pair of sensors, calculate ΔT Theoretical hyperbolic distribution of A0, and using the arccosine function to find ΔT A0 max The propagation time between the sound source and each sensor Δt The ratio is taken as the arrival time difference of the A0 mode.

[0010] Preferably, the acquiring the arrival time difference of the S0 mode specifically includes: For each sensor, the time difference between any pair of sensors receiving the S0 mode signal is calculated based on the S0 mode signal it receives. The formula for the arrival time difference of the S0 mode is: ; In the formula, t s0,A , t s0,B denote the arrival time of sensor A and the S0 mode corresponding to sensor A, respectively.

[0011] Preferably, determining the arrival angle between each sensor and the sound source specifically includes: Based on the triangular sensor array, the area where the sound source is located is located, and the positioning area is divided into three sections of 120 degrees; Based on the sensor that receives the Lamb wave first, for each pair of sensors, the arrival time difference between the S0 mode and the A0 mode between each pair of sensors is calculated. ΔT , select the time difference ΔT The corresponding minimum absolute value in ΔTmin ; The minimum absolute value of the arccosine function ΔTmin Calculate and obtain the angle of arrival between each sensor and the sound source.

[0012] Preferably, determining the relative distance between each sensor and the sound source comprises the following steps: Use Dispersion Calculator software to calculate the dispersion characteristic curves of the S0 mode and A0 mode of Lamb wave of the composite plate, and obtain the modal wave velocity of the S0 mode and A0 mode of Lamb wave of the anisotropic material according to the ply direction and frequency; Based on the modal arrival time difference and the modal velocity of the S0 mode and A0 mode of the Lamb wave, the time it takes for the sound source to reach the three sensors is tested, and the distance formula is used to calculate the distance between the sound source and each sensor; The distance formula is: ; In the formula, t A0 , t S0 denote the arrival times of the S0 mode and the A0 mode respectively, v A0 , v S0 represent the modal wave velocities of S0 mode and A0 mode respectively.

[0013] Preferably, obtaining the coordinate position of the sound source relative to the center point of the sensor array specifically includes: The intersection of the three angular bisectors of the triangular sensor array is defined as the geometric center of the triangular sensor array. Using the principle of triangulation, the coordinate position of the sound source relative to the center point of the sensor array is solved according to the relative distance between each sensor and the sound source. The coordinate position of the sound source relative to the center point of the sensor array is regarded as the damage position on the carbon fiber composite material plate.

[0014] Preferably, a carbon fiber composite material plate damage location system is also included, comprising: A signal acquisition module is used to set up a triangular sensor array on the carbon fiber composite material board to obtain the Lamb wave generated on the carbon fiber composite material board after the lead breaking experiment through the triangular sensor array; A modal arrival time determination module is used to obtain the arrival time of the S0 mode and the A0 mode of the Lamb wave respectively by determining the start time and the end time of the time window of the Lamb wave; The module for determining the arrival angle between the sensor and the sound source is used to obtain the maximum absolute time difference by obtaining the time difference between each pair of sensors; for each pair of sensors, determine the ratio of the maximum absolute time difference to the propagation time between the sound source and each sensor, and obtain the arrival time difference of the A0 mode; subtract the obtained arrival time of the S0 mode between each pair of sensors to determine the arrival time difference of the S0 mode; determine the arrival angle between each sensor and the sound source by calculating the minimum absolute value of the arrival time difference between the S0 mode and the A0 mode; The sound source damage localization module is used to obtain the modal wave velocity of the S0 mode and the A0 mode; determine the relative distance between each sensor and the sound source according to the arrival time and modal wave velocity of the S0 mode and the A0 mode; determine the spacing between the sound source and each sensor according to the arrival angle and relative distance between each sensor and the sound source; and obtain the coordinate position of the sound source relative to the center point of the sensor array through the triangulation principle according to the spacing between the sound source and each sensor, and the coordinate position is the location of the damage on the carbon fiber composite material plate.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The damage location method of the carbon fiber composite material plate proposed by the present invention, through the triangular sensor array set up on the carbon fiber composite material plate, the Lamb wave generated on the carbon fiber composite material plate after the lead breaking test is obtained by the triangular sensor array, and the Lamb wave of the carbon fiber composite material plate at different time points is collected and analyzed, so that the dynamic information of the sound source in the plate can be obtained more directly, thereby realizing real-time monitoring of the health status of the plate structure. Based on the triangular sensor array, the arrival time and arrival time difference of the S0 mode and the A0 mode of the Lamb wave are respectively obtained; by calculating the minimum absolute value of the arrival time difference of the S0 mode and the A0 mode, the arrival angle between each sensor and the sound source is determined, which is conducive to obtaining a high-precision sound source location result. By determining the spacing between the sound source and each sensor, the coordinate position of the sound source relative to the center point of the sensor array is obtained by the triangulation principle, and the coordinate position is the location of the damage on the carbon fiber composite material plate. The method collects the waveform data of the sound wave signal through the sensor array, and combines the characteristics and wave velocity of the material, by accurately calculating the arrival time of the sound source, accurately determining its arrival angle, and comprehensively evaluating the specific distance between the center point of the triangular distributed sensor array and the damaged sound source, to achieve accurate positioning of the sound source. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of the damage location method for carbon fiber composite material plate proposed by the present invention; Figure 2 A graph showing a lead breaking test of a carbon fiber composite material plate provided by an embodiment of the present invention; Figure 3A diagram for determining the arrival time of the lead-off signal S0 provided in an embodiment of the present invention; Figure 4 A diagram for determining the arrival time of the lead-off signal A0 provided in an embodiment of the present invention; Figure 5 A first impact division area diagram provided by an embodiment of the present invention; Figure 6 A schematic diagram of the distance from a sound source to a sensor provided in an embodiment of the present invention; Figure 7 A flowchart of the actual position calculation of a sound source provided by an embodiment of the present invention; Figure 8 A schematic diagram of the sensor arrangement spacing distribution provided in an embodiment of the present invention; Fig. 9 A plane display of the sound source localization calculation result provided by an embodiment of the present invention; Fig.10 A relationship curve between angle error and distance is provided for the embodiment of the present invention. DETAILED DESCRIPTION

[0017] The following will be combined with the attached embodiment of the present invention Figure 1-Figure 10 , the technical solutions in the embodiments of the present invention are clearly and completely described. It should be understood that the terms described in the present invention are only used to describe specific implementation methods and are not used to limit the present invention.

[0018] like Figure 1 As shown, the present invention proposes a method for locating damage of a carbon fiber composite material plate, comprising the following steps: S1: A triangular sensor array is set up on the carbon fiber composite material plate, and the Lamb wave generated on the carbon fiber composite material plate after the lead breaking test is obtained through the triangular sensor array. The acoustic emission signal of the Lamb wave received by a single sensor is analyzed to confirm the accuracy of the AIC (Akaike Information Criterion) method and the threshold method for damage location using Lamb waves.

[0019] S2: By determining the start and end times of the Lamb wave time window, the arrival times of the S0 mode and A0 mode of the Lamb wave are obtained respectively.

[0020] S3: Obtain the maximum absolute time difference by obtaining the time difference between each pair of sensors; for each pair of sensors, determine the ratio of the maximum absolute time difference to the propagation time between the sound source and each sensor, and obtain the arrival time difference of the A0 mode; determine the arrival time difference of the S0 mode by subtracting the obtained arrival times of the S0 mode between each pair of sensors; determine the arrival angle between each sensor and the sound source by calculating the minimum absolute value of the arrival time difference between the S0 mode and the A0 mode.

[0021] S4: Obtain the modal wave velocity of the S0 mode and the A0 mode; determine the relative distance between each sensor and the sound source according to the arrival time and modal wave velocity of the S0 mode and the A0 mode; determine the spacing between the sound source and each sensor according to the arrival angle and relative distance between each sensor and the sound source.

[0022] S5: According to the distance between the sound source and each sensor, the coordinate position of the sound source relative to the center point of the sensor array is obtained through the triangulation principle, and the coordinate position is the location of the damage on the carbon fiber composite material plate.

[0023] Specifically, in step S1, the present invention takes the T700s carbon fiber reinforced composite material plate as the PLB research object, sets a sensor at 200 mm at one end edge thereof, and uses the PLB test to simulate the acoustic emission source. At a distance of 5-40 cm, a PLB test is performed in a manner of setting a lead break every 5 cm to obtain the acoustic emission signal of the Lamb wave.

[0024] In step S2, the AIC information criterion principle is used in combination with the threshold method to analyze the acoustic emission signal of the Lamb wave, so as to determine the arrival time of the S0 mode and the A0 mode of the Lamb wave.

[0025] The AIC criterion is used to determine the starting point of the global minimum. However, when the signal-to-noise ratio is low or in other situations, it cannot reflect the arrival time of the signal very well. Therefore, using the AIC value of the appropriate time window selected in advance as the determination method for the initial time can improve the accuracy of the prediction.

[0026] On this basis, a new signal processing method based on frequency, amplitude or both changes is proposed. The proper selection of characteristic function CF can improve the resolution of noise and sound radiation. For large thin plates, this paper proposes a characteristic function method based on Allen, which can better preserve the weak signal mode of thin plate specimens.

[0027] The specific formula is as follows: ; in, R is a constant determined by experiment.R =4.

[0028] The global maximum of the characteristic function CF is used to reduce the time window range of the Lamb wave, thereby determining the start and end times of the time window. By calculating the global maximum of the characteristic function CF, the time window of the Lamb wave is reduced, and the AIC function is calculated again on the reduced time window range. The time scale corresponding to the global minimum value is the arrival time of the S0 mode of the Lamb wave.

[0029] In order to improve the recognition accuracy of the arrival time of the S0 mode of the Lamb wave, the time window is the time corresponding to the global maximum value of the characteristic function CF from the starting end of the acoustic emission signal of the Lamb wave Add the experimentally determined delay Finish.

[0030] Filter, denoise and normalize the received Lamb wave acoustic emission signal; The envelope of the signal is calculated by the Hilbert transform method to obtain the instantaneous amplitude of the signal; Calculate the maximum value of the envelope, that is, the peak amplitude of the signal A max , according to the peak amplitude, the secondary threshold is set to two-thirds of the peak value as the limit of the effective signal; Find the critical point in the signal envelope, perform half-sine wave fitting between the second critical point and the next adjacent peak, and generate a half-sine curve representing the change trend of the signal waveform through the fitting algorithm; Find the intersection interval of the half-sine wave and the envelope, and the signal zero-crossing point corresponding to the intersection point in the intersection interval. The zero-crossing point is the moment when the signal waveform changes from positive oscillation to negative oscillation. The extrapolation method is used to locate the zero-crossing point of the half-sine wave, and the time corresponding to the zero-crossing point is the arrival time of the A0 mode.

[0031] In step S3, the A0 modal arrival time difference is obtained, which specifically includes: A triangular sensor array is established, and the time difference required for the Lamb wave signal to reach each sensor is measured by setting up a triangular sensor array on a carbon fiber composite material plate; According to the propagation characteristics of the A0 mode of Lamb waves, the time difference between each pair of sensors is calculated. ΔT A0; based on the time difference between each pair of sensors ΔT A0, get the time difference ΔT The corresponding maximum absolute time difference in A0 ΔT A0 max ; For each pair of sensors, calculate ΔTTheoretical hyperbolic distribution of A0, and using the arccosine function to find ΔT A0 max The propagation time between the sound source and each sensor Δt The ratio is taken as the arrival time difference of the A0 mode.

[0032] For each sensor, the time difference between any pair of sensors receiving the S0 mode signal is calculated based on the S0 mode signal it receives. The formula for the arrival time difference of the S0 mode is: ; In the formula, t s0,A , t s0,B denote the arrival time of sensor A and the S0 mode corresponding to sensor A, respectively.

[0033] Furthermore, the angle of arrival is calculated and the ambiguity is removed: Using a triangular sensor array, we first identify the sensor where the sound source signal first arrives, and then divide the area where the sound source may appear into 120° fan-shaped areas. For each sensor, we calculate the arrival time difference between the S0 mode and the A0 mode between each pair of sensors. ΔT , and then determine the arrival time difference ΔT The corresponding minimum absolute value in ΔTmin , through the arc cosine function to the minimum absolute value ΔTmin Calculation is performed to obtain the angle of arrival between each sensor and the sound source.

[0034] The calculation of the angle of arrival is effectively screened using the regional information obtained by identifying the sensor where the sound source signal first arrives to overcome the ambiguity caused by the calculation of the arccosine function.

[0035] On this basis, the arrival angle of each pair of sensors is made consistent with the set global coordinate standard through the method of rotation and transformation of the array global coordinate system: for sensor pair 1-2, the calculated angle is adjusted to α-60°; for sensor pair 1-3, the calculated angle is adjusted to α-120°; for sensor pair 2-3, the calculated angle can be directly adapted to the coordinate system without changing.

[0036] In step S4, the relative distance between each sensor and the sound source is determined, specifically including: The dispersion characteristic curves of the S0 mode and A0 mode of Lamb wave of the composite plate are calculated using the Dispersion Calculator software, and the modal wave velocities of the S0 mode and A0 mode of Lamb wave of the anisotropic material are obtained according to the ply direction and frequency.

[0037] The calculation process to obtain the distance from the center point of the sensor array to the sound source location includes: Based on the modal arrival time difference and the modal velocities of the S0 mode and A0 mode of the Lamb wave, the time it takes for the sound source to reach the three sensors is tested, and the distance formula is used to calculate the distance between the sound source and each sensor.

[0038] The distance formula is: ; In the formula, t A0 , t S0 denote the arrival times of the S0 mode and the A0 mode respectively, v A0 , v S0 represent the modal wave velocities of S0 mode and A0 mode respectively.

[0039] In step S5, the intersection of the three angular bisectors of the triangular sensor array is defined as the geometric center of the triangular sensor array. The coordinate position of the sound source relative to the center point of the sensor array is solved based on the relative distance between each sensor and the sound source using the principle of triangulation. The coordinate position is the location of the damage on the carbon fiber composite material plate.

[0040] The present invention also proposes a carbon fiber composite material plate damage location system, comprising: A signal acquisition module is used to set up a triangular sensor array on the carbon fiber composite material board to obtain the Lamb wave generated on the carbon fiber composite material board after the lead breaking experiment through the triangular sensor array; A modal arrival time determination module is used to obtain the arrival time of the S0 mode and the A0 mode of the Lamb wave respectively by determining the start time and the end time of the time window of the Lamb wave; The module for determining the arrival angle between the sensor and the sound source is used to obtain the maximum absolute time difference by obtaining the time difference between each pair of sensors; for each pair of sensors, determine the ratio of the maximum absolute time difference to the propagation time between the sound source and each sensor, and obtain the arrival time difference of the A0 mode; subtract the obtained arrival time of the S0 mode between each pair of sensors to determine the arrival time difference of the S0 mode; determine the arrival angle between each sensor and the sound source by calculating the minimum absolute value of the arrival time difference between the S0 mode and the A0 mode; The sound source damage localization module is used to obtain the modal wave velocity of the S0 mode and the A0 mode; determine the relative distance between each sensor and the sound source according to the arrival time and modal wave velocity of the S0 mode and the A0 mode; determine the spacing between the sound source and each sensor according to the arrival angle and relative distance between each sensor and the sound source; and obtain the coordinate position of the sound source relative to the center point of the sensor array through the triangulation principle according to the spacing between the sound source and each sensor, and the coordinate position is the location of the damage on the carbon fiber composite material plate.

[0041] The damage location method of the carbon fiber composite material plate proposed in the present invention can directly obtain the dynamic information of the sound source in the plate by collecting and analyzing the Lamb wave signals of the carbon fiber composite material plate at different time points, thereby realizing real-time monitoring of the health status of the plate structure, which is of great significance in engineering. In addition, by arranging the sensor array and adopting the positioning algorithm based on Lamb waves, it is conducive to obtaining high-precision sound source positioning results, and the calculation process is simple, the anti-interference is strong, and it is more suitable for complex working environments. The present invention proposes a method based on the time difference method and the wave velocity model, which can quickly and accurately locate the damage position of the Lamb wave, significantly improve its positioning accuracy, and is more suitable for long-term health monitoring of the CFRP plate structure. The sound source location method disclosed in the present invention is simple to operate, does not require too many site conditions, and is relatively inexpensive. It can monitor the damage of the carbon fiber composite material plate for a long time at a long distance, saves a lot of manpower and material resources, and greatly improves the efficiency of monitoring. By adopting a contactless acoustic emission sensor on the surface of the carbon fiber composite material plate, no contact is made with the plate, the safety of the detection process is ensured, and the potential danger caused by contact is effectively avoided.

[0042] Example In order to verify the effectiveness of the method proposed in the present invention, Figure 2 As shown, it is a lead breaking test diagram of the carbon fiber composite material plate provided in this embodiment.

[0043] The present invention takes T700s carbon fiber composite material plate as the research object, arranges multiple sensors based on a triangular sensor array at 200 mm at one end edge thereof, adopts the PLB test method to simulate the acoustic emission source, and the test range is 5-40 cm away from the sensor. The lead-breaking distance increases by 5 cm each time, and the PLB test is performed to obtain the acoustic emission signal of Lamb wave.

[0044] like Figure 3 As shown in the figure, the arrival time determination diagram of the S0 mode of the Lamb wave obtained through the lead breaking experiment is shown in the figure. According to the AIC criterion, Figure 3 The four diagrams in the figure depict different stages of calculating the arrival time and divide the entire calculation process into two major steps.

[0045] Figure 3 Figure (a) is the real part analysis of continuous wavelet transform (CWT) at a frequency of 200kHz.

[0046] Firstly, for the Lamb waves with different frequencies, the real part of CWT in the 200kHz frequency band is selected and the characteristic function CF is used to solve it, so as to realize the simultaneous and effective detection of the S0 mode and A0 mode of the Lamb wave.

[0047] Then, by calculating the global maximum value of the characteristic function CF, the interval length of the original signal of the Lamb wave in the time domain is shortened, as Figure 3 When applying the calculation formula of the AIC criterion, a suitable time window must be selected to improve the accuracy of identifying the arrival time of the S0 mode and A0 mode of the Lamb wave.

[0048] The calculation formula of AIC criterion is: ; like Figure 3 As shown in Figure (b), a time window is precisely defined, which starts from the initial moment of the original signal of the Lamb wave and continues to the end point of the signal. The signal components within this specified time period are considered to be uninformative. t max is the time corresponding to the global maximum of the characteristic function CF, and the delay Δt am It is determined by multiple experiments, the delay Δ t am The value of is related to the test material. Since it is a thin plate specimen, the calculation here selects Δt am Also 20 μs .

[0049] Secondly, compared with the original signal in the full time domain, based on the time interval reduced by the calculation steps mentioned above, for the selected Lamb wave, at a specific frequency of 200kHz, the continuous wavelet transform CWT is implemented and special attention is paid to the real part of the CWT of the transformation result. Then, according to the calculation formula of the AIC criterion, the real part of the CWT data is deeply analyzed and interpreted. This process not only reveals the dynamic characteristics of the Lamb wave signal in the high frequency band, but also effectively evaluates and optimizes the complexity and fitting degree of the model through the calculation formula of the AIC criterion, ensuring the accuracy and effectiveness of the analysis results.

[0050] The AIC function can be used to effectively calculate and identify the overall minimum value in the Lamb wave signal, thereby accurately extracting its key features. Its corresponding time scale value in the time domain is the estimate of the arrival time. In other words, the minimum value of the AIC function calculated at this moment and its corresponding horizontal axis coordinate are the arrival time of the S0 mode of the Lamb wave, such as Figure 3 As shown in Figure (c) and Figure (d).

[0051] like Figure 4 As shown, it is a diagram for determining the arrival time of the A0 mode of the acoustic emission signal of the Lamb wave generated by the PLB test.

[0052] Although the AIC method performs well in identifying the arrival time of the first S0 mode wave packet of the Lamb wave signal, it is not suitable for detecting the appearance of the A0 mode wave packet. In order to effectively capture this signal feature change, the present invention proposes a technique based on dynamic threshold adjustment, which aims to accurately identify the arrival of the first high-amplitude A0 mode signal after the arrival of the small-amplitude S0 mode signal. This method significantly improves the accuracy and response speed of key signal event detection by adapting to the changes in the modal signal strength in real time.

[0053] Based on the A0 mode of the broken lead signal generated when excited on the plane, it shows a significant characteristic - the modal energy is concentrated and the low-frequency scattering effect is strong, which enables the present invention to effectively identify the A0 mode. However, in the propagation process of the A0 mode, it faces challenges such as boundary reflection, superposition of frequency components and conversion between modes, which may cause the actual peak arrival time of some frequency components to be delayed compared with expectations. Once the first peak value significantly exceeds the preset threshold, it may cause measurement inaccuracy of specific frequency components, thereby causing obvious positioning deviation. This peak is the first peak value to exceed the set limit, that is, the arrival time. When processing using the threshold standard, the peak amplitude of the signal is obtained by calculating the maximum value of the signal envelope, so as to set the secondary threshold, which is set to two-thirds of the maximum amplitude of the modal component. Then, the half-sine wave graph intersects with the partial area of ​​the envelope from the reference point to the subsequent adjacent vertex. Finally, the zero-crossing position of the half-sine wave is determined by extrapolation technology, and the time point corresponding to the zero-crossing position is accurately identified as the arrival time of the modal signal.

[0054] like Figure 5 As shown in the figure, the area division diagram is based on the sensor that receives the Lamb wave first. The positioning area is divided into three different sections and its possible arrival angle is reduced to 120°. The sensor that first receives the sound source signal can point out the section where the sound source is located. On this basis, by comparing the difference between the three groups of sensors when the A0 mode arrives, the minimum absolute value is obtained. ΔTminBased on this minimum absolute value, the minimum absolute value is obtained by the arc cosine function. ΔTmin The calculations give the angle of arrival between each sensor and the sound source. The inverse cosine function produces two distinct sets of solutions (one in the 30° to 150° range; the other in the 210° to 330° range).

[0055] like Figure 6 As shown, this is a schematic diagram of the distance from the sound source to each sensor.

[0056] The calculation of the average distance depends mainly on the average distance between the sound source and the center point of the sensor array, where the center point of the array is located at the intersection of the angular bisectors of the three angles that form the triangular array. By analyzing the calculated distance of the sound source and the actual distance between the center point of the sensor array, the calculated data is compared with the measured data, and it is concluded that the average calculated distance will produce a smaller error. This method can be used to obtain a fixed reference point to determine the location of the sound source in the actual structure.

[0057] like Figure 7 As shown, this is a flowchart of the actual sound source position calculation process.

[0058] On this basis, the arrival time of the two modal components of the Lamb wave signal, A0 mode and S0 mode, was determined by combining the AIC criterion with the threshold method. Since each acquired signal originates from the same sound source, the time difference of the same mode between different sensors and the time difference between the modal components recorded by a single sensor can be calculated.

[0059] Subsequently, the first impact signals of multiple sensors are obtained through the signal timing acquisition method, and the modal wave velocity of the S0 mode and the A0 mode is calculated using the DispersionCalculator software. Then, combined with the arrival time of the second measurement, the arrival time of the two measurements is subtracted. According to the calculated arrival time difference and the modal wave velocity of the A0 mode, the angle information of the sound source arriving at the sensor array is derived, and the arrival angle range of the sound source is determined by the first impact signal. Finally, based on the modal wave velocity of the A0 and S0 modes and their arrival time, the distance between the sound source and each sensor is calculated, and the average spacing and arrival angle from the sound source to each array element are used to deduce the coordinate position of the sound source relative to the center point of the sensor array, that is, the sound source position, which is the location of the damage on the carbon fiber composite material plate.

[0060] like Figure 8 The figure shows the schematic diagram of the sensor layout spacing distribution.

[0061] In the positioning experiment, the PLB test was applied as an artificial sound source to the surface of a carbon fiber reinforced composite material plate (CFRP plate), and its acoustic characteristics were studied. In order to prevent signal damage due to edge reflection during transmission, the present invention intends to conduct a lead-breaking experiment at a grid point 10 cm away from the edge of the plate, and to break the lead at each grid point to ensure the repeatability of the test results and reduce errors caused by human factors in the test. The composite plate is divided into 18×24 units, and the lateral and longitudinal spacing of each unit are the same, and the length is 50 mm. The specific test diagram is as follows Figure 8 As shown, three Nano30 sensors are attached in a triangle shape in the center of the flat plate, and the distance between them (from center point to center point) is 50 mm.

[0062] like Fig. 9 As shown, the plane display of the sound source localization calculation results is shown. Fig. 9 It can be seen that within a short distance, this planar positioning method can achieve high positioning accuracy. However, when the distance increases, its measurement error also increases. By comparing with the measured data, it is found that in most cases, the calculation result of the radial distance from the center of the array to the sound source is very accurate, but there are some errors in the determination of the coordinate release angle.

[0063] like Fig.10 As shown in the figure, a curve of the relationship between angle error and distance is given. Most of the data show that the calculated error of the arrival angle is usually controlled within 8°, and only a few points have a deviation of more than 10°. At a position about 350mm from the center of the array, the absolute error of the arrival angle is about 2.0°. Comprehensively analyzing the various positions of the entire flat panel, the average value of the absolute error of the arrival angle is about 3.2°. Moreover, from the calculation results of all error values, as the distance increases, the increase in the error value becomes relatively gentle, and the maximum error distribution is within 6°.

[0064] The present embodiment discloses a method for locating damage of a carbon fiber composite material plate based on multi-mode Lamb waves. By collecting and processing the acoustic emission signals of the CFRP plate, the sound source position information on the CFRP plate can be more directly obtained, thereby realizing accurate positioning and extension of the internal damage of the CFRP plate.

[0065] The present invention proposes a method for calculating the arrival angle based on the stability of the A0 modal wave velocity, which effectively improves the positioning accuracy while satisfying the propagation characteristics of anisotropic materials; by combining the modal separation signal processing technology with the fast time difference method to locate the sound source, the detection accuracy of the signal arrival time is significantly improved, the reliability of the sound source positioning is improved, and it is more suitable for long-term monitoring of internal damage of CFRP plates. At the same time, the method proposed by the present invention has the advantages of simple structure, easy operation, no dependence on the test environment and low cost, which can avoid manual intervention to a large extent and improve monitoring efficiency.

[0066] In order to facilitate those skilled in the art to fully understand and implement the contents disclosed in the present invention, the following specifically describes the installation and operation process of the planar sound source localization system based on the CFRP plate in combination with the methods and systems of the above embodiments: Step 1: Sensor layout and installation: Select a wide-band piezoelectric sensor suitable for Lamb wave detection to ensure that the sensor can work within the target frequency band. Arrange the three sensors evenly on the surface of the CFRP plate in an equilateral triangle, making them as close to the location of the sound source as possible to improve the accuracy of positioning. Use highly sensitive double-sided tape or a special fixing fixture to make the sensor fit tightly to the surface of the plate to prevent signal attenuation. In order to reduce signal loss and external interference, connect the sensor to the data acquisition system and use a high-resistance coaxial cable to transmit the signal.

[0067] Step 2: System calibration: Before formally acquiring the signal, the modal wave velocity of the Lamb wave needs to be calibrated. Generate Lamb wave signals at known point sound sources (such as lead core rupture, piezoelectric excitation, etc.), and measure the time difference received by each sensor. By analyzing the known characteristics of the material and different ply directions, combined with the dispersion curve, the group velocity and phase velocity in different directions are calculated, and the polar coordinate sound velocity distribution of the S0 mode and A0 mode in different directions is obtained, providing basic parameter basis for positioning calculation.

[0068] Step 3: Signal acquisition and processing: In the experiment, the acoustic emission signal of Lamb wave is introduced through the signal excitation device, and the Lamb wave of CFRP is collected through the sensor. The appropriate sampling frequency is selected to ensure the complete signal collected without confusion. The collected signal is transmitted to the computer through a high-speed data acquisition card and further analyzed by digital signal processing software. On this basis, the mode is separated by using time-frequency analysis methods such as wavelet transform and FFT to obtain the arrival time of the two modes of A0 mode and S0 mode.

[0069] Step 4: Sound source localization: The modal wave velocity calibration parameters obtained in step 2 are combined with the geometric arrangement of the sensor array to calculate the travel time difference from the sound source to each sensor. A method based on triangulation and time inversion technology is proposed, which can accurately obtain the planar position between the sound source and the center point of the sensor array and give the corresponding error range. On this basis, the positioning results are repeatedly calculated to eliminate random errors and achieve the optimal positioning accuracy.

[0070] Step 5: Result analysis and verification: The positioning results are evaluated for errors and compared with known point sound sources to verify the accuracy of the positioning. On this basis, combined with the signal amplitude attenuation law after modal separation, the change relationship between the sound source distance sensor is analyzed to determine the damage type and range of the structure. Finally, the positioning results are combined with the test requirements to monitor and evaluate the damage of the CFRP flat plate structure.

[0071] The system is reasonably designed and easy to operate. It is suitable for acoustic emission monitoring of various types of CFRP plates. It can effectively reduce human interference, improve the accuracy and efficiency of sound source positioning, and provide reliable data support for the safety assessment of complex composite structures.

[0072] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0073] In addition, unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention belongs. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods related to the documents. In the event of any conflict with any incorporated document, the content of this specification shall prevail.

Claims

1. A method for locating damage of a carbon fiber composite material plate, characterized in that: The following steps are involved: A triangular sensor array is set up on the carbon fiber composite material plate to obtain the Lamb wave generated on the carbon fiber composite material plate after the lead breaking experiment through the triangular sensor array; By determining the start and end time of the Lamb wave time window, the arrival time of the S0 mode and A0 mode of the Lamb wave are obtained respectively; By obtaining the time difference between each pair of sensors, the maximum absolute time difference is obtained; for each pair of sensors, the ratio of the maximum absolute time difference to the propagation time between the sound source and each sensor is determined to obtain the arrival time difference of the A0 mode; the arrival time of the S0 mode between each pair of sensors is subtracted to determine the arrival time difference of the S0 mode; by calculating the minimum absolute value of the arrival time difference between the S0 mode and the A0 mode, the arrival angle between each sensor and the sound source is determined; Obtain the modal wave velocity of the S0 mode and the A0 mode; determine the relative distance between each sensor and the sound source according to the arrival time and modal wave velocity of the S0 mode and the A0 mode; determine the spacing between the sound source and each sensor according to the arrival angle and relative distance between each sensor and the sound source; According to the distance between the sound source and each sensor, the coordinate position of the sound source relative to the center point of the sensor array is obtained through the triangulation principle. The coordinate position is the location of the damage on the carbon fiber composite material plate.

2. The method for locating damage of a carbon fiber composite material plate according to claim 1, characterized in that: The obtaining of the arrival time of the S0 mode of the Lamb wave specifically includes: Select the time window of Lamb wave, calculate the characteristic function CF based on the real part of continuous wavelet transform CWT at a preset frequency, and shorten the time window of the signal according to the global maximum value of the characteristic function CF; In the shortened time window, the AIC function is used to calculate the minimum value of the signal, and the time scale corresponding to the minimum value is obtained, which is the arrival time of the S0 mode.

3. The damage location method of carbon fiber composite material plate according to claim 2, characterized in that: The obtaining of the arrival time of the A0 mode of the Lamb wave specifically includes: Filter, denoise and normalize the received Lamb wave signal; The envelope of the signal is calculated by the Hilbert transform method to obtain the instantaneous amplitude of the signal; Calculate the maximum value of the envelope, that is, the peak amplitude of the signal A max , according to the peak amplitude, the secondary threshold is set to two-thirds of the peak value as the limit of the effective signal; Find the critical point in the signal envelope, perform half-sine wave fitting between the second critical point and the next adjacent peak, and generate a half-sine curve representing the change trend of the signal waveform through the fitting algorithm; Find the intersection interval of the half-sine wave and the envelope, and the signal zero-crossing point corresponding to the intersection point in the intersection interval. The zero-crossing point is the moment when the signal waveform changes from positive oscillation to negative oscillation. The extrapolation method is used to locate the zero-crossing point of the half-sine wave, and the time corresponding to the zero-crossing point is the arrival time of the A0 mode.

4. The method for locating damage of a carbon fiber composite material plate according to claim 3, characterized in that: The obtaining of the arrival time difference of the A0 mode specifically includes: A triangular sensor array is established, and the time difference required for the Lamb wave signal to reach each sensor is measured by setting up a triangular sensor array on a carbon fiber composite material plate; According to the propagation characteristics of the A0 mode of Lamb wave, the time difference between each pair of sensors is calculated ΔT A0; Based on the time difference between each pair of sensors ΔT A0, get the time difference ΔT The corresponding maximum absolute time difference in A0 Δ T A0 max ; For each pair of sensors, calculate ΔT Theoretical hyperbolic distribution of A0, and using the arccosine function to find ΔT A0 max The propagation time between the sound source and each sensor Δt The ratio is taken as the arrival time difference of the A0 mode.

5. The method for locating damage of a carbon fiber composite material plate according to claim 4, characterized in that: The obtaining of the arrival time difference of the S0 mode specifically includes: For each sensor, the time difference between any pair of sensors receiving the S0 mode signal is calculated based on the S0 mode signal it receives. The formula for the arrival time difference of the S0 mode is: ； In the formula, t s0,A , t s0,B denote the arrival time of sensor A and the S0 mode corresponding to sensor A, respectively.

6. The method for locating damage of a carbon fiber composite material plate according to claim 5, characterized in that: Determining the arrival angle between each sensor and the sound source specifically includes: Based on the triangular sensor array, the area where the sound source is located is located, and the positioning area is divided into three sections of 120 degrees; Based on the sensor that receives the Lamb wave first, for each pair of sensors, the arrival time difference between the S0 mode and the A0 mode between each pair of sensors is calculated. ΔT , select the time difference ΔT The corresponding minimum absolute value in ΔTmin ; The minimum absolute value of the arccosine function ΔTmin Calculate and obtain the angle of arrival between each sensor and the sound source.

7. The method for locating damage of a carbon fiber composite material plate according to claim 6, characterized in that: Determining the relative distance between each sensor and the sound source comprises the following steps: Use Dispersion Calculator software to calculate the dispersion characteristic curves of the S0 mode and A0 mode of Lamb wave of the composite plate, and obtain the modal wave velocity of the S0 mode and A0 mode of Lamb wave of the anisotropic material according to the ply direction and frequency; Based on the modal arrival time difference and the modal velocity of the S0 mode and A0 mode of the Lamb wave, the time it takes for the sound source to reach the three sensors is tested, and the distance formula is used to calculate the distance between the sound source and each sensor; The distance formula is: ； In the formula, t A0 , t S0 denote the arrival times of the S0 mode and the A0 mode respectively, v A0 , v S0 represent the modal wave velocities of S0 mode and A0 mode respectively.

8. The method for locating damage of a carbon fiber composite material plate according to claim 7, characterized in that: The method of obtaining the coordinate position of the sound source relative to the center point of the sensor array by using the triangulation principle specifically includes: The intersection of the three angular bisectors of the triangular sensor array is defined as the geometric center of the triangular sensor array. Using the principle of triangulation, the coordinate position of the sound source relative to the center point of the sensor array is solved according to the relative distance between each sensor and the sound source. The coordinate position of the sound source relative to the center point of the sensor array is regarded as the damage position on the carbon fiber composite material plate.

9. A carbon fiber composite material plate damage location system, characterized in that: include: A signal acquisition module is used to set up a triangular sensor array on the carbon fiber composite material board to obtain the Lamb wave generated on the carbon fiber composite material board after the lead breaking experiment through the triangular sensor array; A modal arrival time determination module is used to obtain the arrival time of the S0 mode and the A0 mode of the Lamb wave respectively by determining the start time and the end time of the time window of the Lamb wave; The module for determining the arrival angle between the sensor and the sound source is used to obtain the maximum absolute time difference by obtaining the time difference between each pair of sensors; for each pair of sensors, determine the ratio of the maximum absolute time difference to the propagation time between the sound source and each sensor, and obtain the arrival time difference of the A0 mode; subtract the obtained arrival time of the S0 mode between each pair of sensors to determine the arrival time difference of the S0 mode; determine the arrival angle between each sensor and the sound source by calculating the minimum absolute value of the arrival time difference between the S0 mode and the A0 mode; The sound source damage localization module is used to obtain the modal wave velocity of the S0 mode and the A0 mode; determine the relative distance between each sensor and the sound source according to the arrival time and modal wave velocity of the S0 mode and the A0 mode; determine the spacing between the sound source and each sensor according to the arrival angle and relative distance between each sensor and the sound source; and obtain the coordinate position of the sound source relative to the center point of the sensor array through the triangulation principle according to the spacing between the sound source and each sensor, and the coordinate position is the location of the damage on the carbon fiber composite material plate.

Images