Micro-damage tomography method based on nonlinear ultrasonic static component damage index

Abstract

The application provides a micro-damage tomography method based on a nonlinear ultrasonic static component damage index, and particularly relates to the technical field of material monitoring. The method specifically comprises the following steps: S1, arranging sensors on the surface of a component to be measured; S2, setting a signal excitation end and a signal receiving end; S3, respectively emitting signals from the signal excitation end and collecting received signals of the signal receiving end, and performing error preprocessing on the collected signals; S4, performing fast Fourier transform analysis and obtaining a static component energy value; S5, calculating a nonlinear damage index; and S6, embedding the nonlinear damage index as a parameter into a RAPID elliptical positioning algorithm based on a detection grid formed by a circular array or an orthogonal scanning array, calculating and filling pixel values of the detection grid of an imaging area, and generating a micro-damage tomography image. Through the nonlinear damage index and the RAPID elliptical tomography algorithm, the application can realize the positioning imaging of millimeter-level micro-cracks, delamination defects and the like in a structure to be monitored.

Description

Technical Field

[0001] This invention relates to the field of materials monitoring technology, specifically to a micro-damage tomography method based on the nonlinear ultrasonic static component damage index. Background Technology

[0002] Materials are prone to structural defects such as microcracks, fatigue damage, and delamination under long-term service or extreme conditions (e.g., high temperature, high load, strong radiation). If these defects are not detected and identified in a timely manner, they may lead to catastrophic failures and cause significant damage to personnel and equipment. Therefore, developing highly sensitive and reliable non-destructive testing technologies is of great significance for ensuring the safe operation of critical structures.

[0003] Ultrasonic nondestructive testing (UDT) has become an important technical means in the field of structural health monitoring due to its advantages such as non-invasiveness, high resolution, and strong penetration. However, existing mainstream linear ultrasonic testing methods mainly rely on the elastic response of materials, and have weak ability to identify microscale damage (such as early cracks or interface degradation), which is prone to false positives or false negatives. Traditional nonlinear ultrasonic testing methods, such as those based on the second harmonic coefficient (... While traditional ultrasonic imaging can reflect nonlinear damage, it suffers from severe signal attenuation and poor imaging stability in high-attenuation materials (such as carbon fiber composites), limiting its practical engineering applications. In recent years, static component (SC) signals, as a direct product of nonlinear acoustic response, have attracted widespread attention. Damage regions such as cracks and interface fissures accumulate local low-frequency strain under ultrasonic excitation, resulting in an enhancement of the static component in the signal. Compared to harmonic components, the static component has a lower frequency, stronger penetration ability, and better attenuation resistance, making it particularly suitable for micro-damage detection in high-attenuation systems such as composite materials and complex components.

[0004] In industrial nondestructive testing image reconstruction, the imaging algorithm and sensor array layout directly determine the imaging quality and detection resolution. Existing systems mostly employ the RAPID algorithm for elliptic probabilistic image reconstruction. This algorithm utilizes the time difference of sound wave propagation (TOF) to construct an elliptic trajectory model between the transmitter and receiver pairs, achieving defect probability mapping. However, the traditional RAPID algorithm primarily relies on linear signal amplitude as a damage indicator, failing to fully extract nonlinear response features and exhibiting insufficient sensitivity in multipath interference or complex structural scenarios, easily leading to blurred images or misjudgments. Furthermore, the acoustic wave amplitude upon which existing elliptic localization algorithms are based is typically significantly affected by material anisotropy, sound attenuation, and structural noise, resulting in a low signal-to-noise ratio, unclear image boundaries, and difficulty in achieving accurate spatial reconstruction of early, subtle damage.

[0005] Therefore, there is an urgent need for a new ultrasonic nondestructive testing method that can combine nonlinear acoustic parameters, adapt high attenuation materials, and improve spatial imaging accuracy to break through the technical bottlenecks of existing linear ultrasonic or traditional RAPID image algorithms in micro-damage detection. SUMMARY

[0006] To overcome the shortcomings of the prior art, the present application provides a micro-damage tomography method based on a nonlinear ultrasonic static component damage index, and the specific technical solutions are as follows:

[0007] A micro-damage tomography method based on a nonlinear ultrasonic static component damage index, specifically comprising the following steps:

[0008] S1. One of a circular array or an orthogonal scanning array is selected to arrange sensors on the surface of the component to be measured;

[0009] S2. The signal excitation end and the signal receiving end are set;

[0010] S3. The signal excitation end is respectively subjected to signal transmission, and the received signal of the signal receiving end is transmitted to an oscilloscope through an amplifier, the signal uploaded by the oscilloscope is uploaded to a PC data processing terminal, and the collected signal is subjected to error preprocessing;

[0011] S4. Fast Fourier transform analysis is performed based on the signal after error preprocessing in S3, and the static component energy value is obtained;

[0012] S5. The nonlinear damage index is calculated ;

[0013] S6. The nonlinear damage index is embedded as a parameter into a RAPID elliptical positioning algorithm based on the detection grid formed by the circular array or the orthogonal scanning array, the detection grid of the imaging area is calculated and filled, and a micro-damage tomography image is generated.

[0014] Preferably, in S1, the circular array is arranged according to a circular structure with a diameter of , and the number of elements of the circular array is ;

[0015] The orthogonal scanning array is to take one face of the component to be measured as a scanning area and to arrange two sensors at adjacent two corner positions of the scanning area;

[0016] wherein the diameter of the circular array satisfies ; the spacing between the two sensors of the orthogonal scanning array satisfies ; and the wavelength , the phase velocity of the transmission frequency of the signal excitation end, the transmission frequency of the signal excitation end.

[0017] Preferably, in S2, the center frequency of the signal excitation end and the signal receiving end sensor is 500 kHz; the transmission signal of the signal excitation end adopts a narrow-band pulse modulated by a Hanning window and the transmission frequency is 200 kHz-500 kHz.

[0018] Preferably, in S3, the signal transmission and signal collection specifically include:

[0019] S3.1. When the circular array arrangement is adopted, the signal collection process specifically includes the following sub-steps:

[0020] S3.1.1 sequentially taking each of the sensors of the circular array as the signal excitation end and the remaining sensors as the signal receiving end;

[0021] S3.1.2 using a signal generator to sequentially transmit low-amplitude excitation signals and high-amplitude excitation signals to each sensor through an attenuator for excitation, while collecting the signals received by the remaining sensors; wherein, when each sensor is taken as the signal excitation end, the signals received by the remaining sensors are repeatedly collected not less than five times;

[0022] S3.1.3 uploading the received signals obtained in S3.1.2 to a PC data processing terminal and taking the average of the repeatedly collected signals, thereby completing the preprocessing of the accidental errors of the measurement results;

[0023] S3.2. When the orthogonal scanning array arrangement is adopted, the signal collection process specifically includes the following sub-steps:

[0024] S3.2.1 setting the signal excitation end at one of the corners of the scanning area and setting the signal receiving end along the X-axis direction at the other corner of the scanning area;

[0025] S3.2.2 using a signal generator to transmit low-amplitude excitation signals and high-amplitude excitation signals to the signal excitation end through an attenuator for excitation, while collecting the signals of the signal receiving end, thereby completing the scanning of one sound path;

[0026] S3.2.3 synchronously moving the signal excitation end and the signal receiving end along the Y-axis direction, the moving step of each scanning being 5 mm, and repeatedly performing S3.2.2 to complete the scanning along the Y-axis direction of the scanning area; wherein, the signal needs to be repeatedly collected not less than five times when each sound path is scanned;

[0027] S3.2.4 moving the signal excitation end back to the initial position and moving the signal receiving end to the edge corner diagonally opposite to its initial position;

[0028] S3.2.5 exciting the signal excitation end with low-amplitude excitation signals and high-amplitude excitation signals respectively transmitted by the signal generator through the attenuator, and collecting signals of the signal receiving end at the same time, to complete scanning of one sound path;

[0029] S3.2.6 moving the signal excitation end and the signal receiving end synchronously along the X-axis direction, with a moving step of 5 mm for each scanning, and repeating S3.2.5 to complete scanning along the X-axis direction of the scanning area; wherein the signal is collected for no less than five times for each scanning of the sound path;

[0030] S3.2.7 uploading the received signals obtained in S3.2.3 and S3.2.6 to the PC data processing terminal, and calculating the average value of the repeatedly collected signals for each sound path, to complete the preprocessing of the accidental error of the measurement results of all sound paths.

[0031] It is also preferred that the voltage amplitude of the low-amplitude excitation signal ranges from 10 to 30 V, and the voltage amplitude of the high-amplitude excitation signal ranges from 50 to 80 V.

[0032] It is also preferred that the collected signals after error preprocessing based on S3.1.3 or S3.2.7 are subjected to fast Fourier transform analysis, and the spectral amplitudes in the integral zero-frequency band of 0-500 Hz are used to calculate and respectively.

[0033] wherein, is the static component energy under the excitation of the low-amplitude excitation signal; is the static component energy under the excitation of the high-amplitude excitation signal.

[0034] It is further preferred that in S5, the nonlinear damage index is calculated according to the following formula:

[0035] .

[0036] wherein, is the amplification coefficient of the signal amplitude transmitted by the signal excitation end, i.e. the ratio of the high amplitude to the low amplitude of the incident wave of the signal excitation end, .

[0037] It is still further preferred that in S6, the detection grid formed by the circular array or the orthogonal scanning array is a two-dimensional spatial grid, and each pixel point in the two-dimensional spatial grid corresponds to a spatial position in the component to be measured; and the nonlinear damage index Embedded into the RAPID elliptical positioning algorithm, each pixel point in the two-dimensional space grid is calculated respectively to obtain the comprehensive nonlinear response intensity of each pixel point, realize the visualization imaging and spatial reconstruction of the potential damage position and degree inside the measured component structure, and generate a micro-damage tomographic image; wherein the spatial position in the image is embodied by different colors of the probability of damage existing in the position, specifically:

[0038] Case one: the dark blue to light green region corresponds to a low value, indicating that the material state of the region is good, no nonlinear response is found, and it is inferred to be a damage-free state;

[0039] Case two: the yellow to red region corresponds to a high value, indicating that the response nonlinearity degree of the region under high amplitude excitation is significantly enhanced, and it is inferred to exist debonding, micro-crack or fatigue damage;

[0040] Wherein, when the imaging area presents a strip distribution with an aspect ratio of greater than or equal to 4:1, it is inferred that there is a crack propagation path or fatigue damage along the length direction; when the imaging area presents a circular or elliptical patch distribution, it is inferred to be a debonding defect.

[0041] Further preferably, the PC data processing terminal comprises a MATLAB signal processing module, a fast Fourier transform analysis module, a parameter extraction module and a wireless communication module; the signal excitation end, the signal receiving end, the signal generator, the attenuator, the amplifier and the oscilloscope are electrically connected with the PC data processing terminal.

[0042] The beneficial effects of the present application are:

[0043] The present application proposes a kind of static component nonlinear damage index The micro-damage detection method combining the RAPID elliptical tomographic algorithm amplifies damage signal by high and low excitation amplitude modulation, combines circular array or orthogonal scanning, optimizes imaging algorithm, realizes high sensitivity, high efficiency detection and accurate spatial positioning of micro-damage;

[0044] Compared with traditional nonlinear second harmonic detection method, in the detection sensitivity, The index effectively avoids the dependence of second harmonic method on phase matching by extracting static nonlinear response, and the nonlinear damage index calculated by static component is 1.5 times of the damage index obtained by corresponding second harmonic method, so that stable identification of micro-damage is realized;

[0045] Especially in the field of composite nondestructive testing, the nonlinear damage index calculated by static component The imaging performance is significantly better than the traditional second harmonic method, and the core breakthrough is the signal fidelity improvement brought by the low attenuation characteristic, thereby maintaining the signal strength stable, and still achieving a signal-to-noise ratio of ≥8dB under a background noise of 20dB. However, in anisotropic materials such as carbon fiber reinforced polymers, the energy is quickly dissipated due to the dispersion effect when the sound wave propagates (the measured attenuation coefficient is 23.7dB / m at 5MHz), which seriously restricts the ability of deep defect detection and large area detection; but by extracting the steady-state response of the fundamental wave and the nonlinear action of the material, the attenuation coefficient is only linearly related to the frequency (the measured attenuation coefficient is 7.2dB / m in the same frequency band), which greatly improves the signal penetration depth and propagation distance, and supports deep defect detection and larger area scanning. BRIEF DESCRIPTION OF DRAWINGS

[0046] The drawings constituting the specification of the present application are used to provide further understanding of the present application and do not constitute undue limitations on the present application.

[0047] Figure 1 A flowchart for the method of the present application is provided;

[0048] Figure 2 A sensor layout diagram for a circular array;

[0049] Figure 3 A sensor layout and scanning path diagram for an orthogonal scanning array;

[0050] Figure 4 A schematic diagram for Example 1 using a circular array; wherein (a) is a layout diagram of the positions of the sensors; (b) is a numbering diagram of each sensor;

[0051] Figure 5 Micro-damage tomographic images generated in Example 1; wherein (a) is a tomographic image of a 10×10mm debonding defect of the test piece; (b) is a tomographic image of a 3×3mm debonding defect of the test piece;

[0052] Figure 6 A tomographic image of a 10×10mm debonding defect of the test piece using the traditional second harmonic method;

[0053] Figure 7 A schematic diagram of the orthogonal scanning area in Example 2;

[0054] Figure 8 Micro-damage tomographic images generated in Example 2. DETAILED DESCRIPTION

[0055] The specific embodiments of the micro-damage tomographic imaging method based on the nonlinear ultrasonic static component damage index provided by the present application are further described in conjunction with the drawings and examples.

[0056] AsFigure 1 As shown, the micro-damage tomography method based on nonlinear ultrasonic static component damage index specifically comprises the following steps:

[0057] S1. Select one of a circular array or an orthogonal scanning array to arrange sensors on the surface of the measured component;

[0058] Preferably, in S1, the circular array is arranged in a circular structure with each sensor arranged along a diameter of , and the number of elements of the circular array is , as shown in Figure 2 ;

[0059] The orthogonal scanning array is to arrange two sensors at adjacent two corner positions of a scanning area of the measured component.

[0060] Preferably, the diameter of the circular array is , and the distance between the two sensors of the orthogonal scanning array is ; and the wavelength , the phase velocity of the signal excitation end transmission frequency is , and the transmission frequency of the signal excitation end is . Here, it is worth mentioning that the sensors in the circular array are piezoelectric sheets, and the sensors in the orthogonal scanning array are ultrasonic probes.

[0061] S2. Set the signal excitation end and the signal receiving end.

[0062] Preferably, in S2, the center frequency of the signal excitation end and the signal receiving end sensor is 500 kHz; the transmission signal of the signal excitation end adopts a narrow-band pulse modulated by a Hanning window, and the transmission frequency is 200 kHz to 500 kHz.

[0063] S3. Transmit signals from the signal excitation end and collect the received signals of the signal receiving end, transmit the received signals through an amplifier to an oscilloscope, upload the signals collected by the oscilloscope to a PC data processing terminal, and perform error preprocessing on the collected signals.

[0064] Preferably, in S3, the signal transmission and signal collection using different arrays specifically includes:

[0065] S3.1. When the circular array is used, the signal collection process specifically includes the following sub-steps:

[0066] S3.1.1 sequentially arrange the , and the number of elements of the circular array is

[0067] , as shown in ;one sensor is respectively set as a signal excitation end, and the remaining sensors are respectively set as signal receiving ends one sensor is respectively set as a signal excitation end, and the remaining sensors are respectively set as signal receiving ends

[0068] S3.1.2, the signal generator is used to transmit low-amplitude excitation signals and high-amplitude excitation signals to each sensor through the attenuator, and signals received by the remaining sensors are collected at the same time; wherein, each sensor is set as a signal excitation end, and the signals received by the remaining sensors are collected for not less than five times;

[0069] S3.1.3, the signals obtained in S3.1.2 are uploaded to a PC data processing terminal, and the average value of the repeatedly collected signals is calculated, so as to complete the preprocessing of the accidental error of the measurement result;

[0070] S3.2, when the orthogonal scanning array is used, the signal collection process specifically includes the following sub-steps:

[0071] S3.2.1, the signal excitation end is set at one corner of the scanning area, and the signal receiving end is set at the other corner of the scanning area along the X-axis direction;

[0072] S3.2.2, the signal generator is used to transmit low-amplitude excitation signals and high-amplitude excitation signals to the signal excitation end through the attenuator, and the signals received by the signal receiving end are collected at the same time, so as to complete the scanning of one sound path;

[0073] S3.2.3, the signal excitation end and the signal receiving end are synchronously moved along the Y-axis direction, the moving step of each scanning is 5mm, and S3.2.2 is repeated to complete the scanning along the Y-axis direction of the scanning area; wherein, the signals are collected for not less than five times during the scanning of each sound path;

[0074] S3.2.4, the signal excitation end is moved back to the initial position, and the signal receiving end is moved to the corner opposite to the initial position;

[0075] S3.2.5, the signal generator is used to transmit low-amplitude excitation signals and high-amplitude excitation signals to the signal excitation end through the attenuator, and the signals received by the signal receiving end are collected at the same time, so as to complete the scanning of one sound path;

[0076] S3.2.6, the signal excitation end and the signal receiving end are synchronously moved along the X-axis direction, the moving step of each scanning is 5mm, and S3.2.5 is repeated to complete the scanning along the X-axis direction of the scanning area; wherein, the signals are collected for not less than five times during the scanning of each sound path; the specific scanning path is shown in Figure 3

[0077] ​S3.2.7 Uploads several received signals obtained in S3.2.3 and S3.2.6 to the PC data processing terminal and calculates the average value of the signals repeatedly collected for each sound path, thereby completing the preprocessing of random errors in the measurement results of all sound paths.

[0078] Preferably, the voltage amplitude range of the low-amplitude excitation signal is 10–30V; and the voltage amplitude range of the high-amplitude excitation signal is 50–80V.

[0079] S4. Perform Fast Fourier Transform analysis on the signal after error preprocessing in S3 and obtain the energy value of the static component;

[0080] Preferably, a Fast Fourier Transform analysis is performed on the average value of the acquired signal after error preprocessing according to S3.1.3 or S3.2.7, and the spectral amplitude within the zero-band of integration (0–500 Hz) is used to calculate the... and ;

[0081] in, The static component energy under low-amplitude excitation signal excitation; This refers to the static component energy under high-amplitude excitation signal.

[0082] S5. Calculate the nonlinear damage index ;

[0083] More preferably, in S5, the nonlinear damage index The calculation formula is as follows:

[0084] ;

[0085] in, This is the amplification factor of the transmitted signal amplitude at the signal excitation end, which is the ratio of the high and low amplitudes of the incident wave at the signal excitation end. .

[0086] S6. Based on the detection grid formed by a circular array or orthogonal scanning array, the nonlinear damage index is... The RAPID elliptical localization algorithm is embedded as a parameter to calculate and fill the detection grid in the imaging area, generating a micro-damage tomographic image.

[0087] Specifically, the detection grid formed by a circular array or orthogonal scanning array is a two-dimensional spatial grid, where each pixel corresponds to a spatial location in the component under test; the circular array uses a directly defined polar coordinate grid. Generate a detection grid; an orthogonal scanning array of sensors is arranged along the Cartesian coordinate axes to form a Cartesian grid. Further generate a detection grid; and apply the nonlinear damage index. Embedded into the RAPID elliptical positioning algorithm, each pixel point in the two-dimensional spatial grid is calculated respectively to obtain the comprehensive nonlinear response intensity of each pixel point, realize the visualization imaging and spatial reconstruction of the potential damage location and degree inside the measured component structure, and generate a micro-damage tomographic image; wherein each spatial position in the image reflects the probability of damage at its position through different colors, specifically:

[0088] Case one: the deep blue to light green area corresponds to a low value, indicating that the material state of the region is good, no nonlinear response is found, and it is inferred to be a damage-free state;

[0089] Case two: the yellow to red area corresponds to a high value, indicating that the nonlinear degree of response of the region under high amplitude excitation is significantly enhanced, and it is inferred to exist as debonding, micro-cracks or fatigue damage;

[0090] Wherein, when the imaging area presents a strip distribution with an aspect ratio ≥ 4:1, it is inferred that there is a crack propagation path or fatigue damage along the length direction; when the imaging area presents a circular or elliptical patch distribution, it is inferred that it is a debonding defect.

[0091] Specifically, if the imaging area presents a circular or elliptical patch distribution with an aspect ratio less than 2:1, the boundary is clear and distributed isolated, and it is usually inferred to be a debonding, interface separation or local non-bonding defect;

[0092] If the imaging area presents a short strip or thin line distribution with an aspect ratio generally between 2:1 and 4:1 and exhibits an asymmetric, locally prominent high response area, it is inferred to be an early micro-crack initiation area;

[0093] If the imaging area presents a strip or elongated strip distribution with an aspect ratio greater than or equal to 4:1 and is continuously distributed along the length direction, it is inferred to be a fatigue cumulative damage area or a crack propagation path.

[0094] More preferably, the PC data processing terminal comprises a MATLAB signal processing module, a fast Fourier transform analysis module, a parameter extraction module and a wireless communication module; the signal excitation end, the signal receiving end, the signal generator, the attenuator, the amplifier and the oscilloscope are electrically connected with the PC data processing terminal.

[0095] In order to better understand the micro-damage tomographic imaging method provided by the present application, the following specific embodiments are described.

[0096] Example 1:

[0097] In this embodiment, 12 piezoelectric sheets are used in a circular array layout, and the piezoelectric sheets are numbered 1-12 in turn, such asFigure 4 Two metal component bonding samples were selected as sample bodies, wherein the upper and lower bonding layers of each sample body were bonded with Al7075-T6 aluminum alloy material, and the size was 200*200*2mm; the middle bonding layer was bonded with IXChemistry-28206 two-component liquid industrial adhesive, and a polytetrafluoroethylene sheet was placed in the middle bonding layer between the bonding layer and the bonded layer to simulate the debonding defect (two square debonding defects with sizes of 10*10mm and 3*3mm were respectively placed in the middle bonding layers of the two sample bodies for comparative analysis). The center of the bonded component was taken as the origin to establish a rectangular coordinate system, and the center position coordinates of the debonding defects in the embodiment were (20, 30). The excitation signal of the signal excitation end was a sinusoidal pulse signal with a cycle number of 10, a center frequency of 300 kHz, and a Hanning window modulation, and the circumferential array diameter was 150mm.

[0098] During detection, first, a low-amplitude excitation signal (the output level was set to 40%) was used to sequentially complete the full-array signal acquisition process: taking No. 1 piezoelectric sheet as the signal excitation end, the received signals of Nos. 2 to 12 piezoelectric sheets except No. 1 were collected; then taking No. 2 piezoelectric sheet as the signal excitation end, the received signals of Nos. 1 and 3 to 12 piezoelectric sheets except No. 2 were collected; and so on, until the full signal acquisition of 12 piezoelectric sheets as the signal excitation end was completed, and a total of 132 groups of response data under the condition of low-amplitude excitation signal were obtained in a single acquisition.

[0099] Then, the above steps were repeated, and the acquisition was repeated in the same excitation-receiving sequence, but the low-amplitude excitation signal was replaced by a high-amplitude excitation signal (the output level was set to 80%), and a total of 132 groups of response data under the condition of high-amplitude excitation signal were obtained in a single acquisition.

[0100] In order to reduce the accidental error of the measurement results, when each piezoelectric sheet was taken as the signal excitation end, the remaining signal receiving end signals were collected 5 times repeatedly and the average value was taken, that is, a total of 660 groups of low-amplitude and 660 groups of high-amplitude excitation signal data were finally obtained, and after average processing, 132*2 groups of signal data under the condition of paired high and low amplitude excitation signals were formed, which were used for subsequent defect detection and positioning analysis calculation.

[0101] Specifically, Figure 5Fig. 5 (a) is the damage tomography result of the debonding defect with the size of 10x10mm; Fig. 5 (b) is the damage tomography result of the debonding defect with the size of 3x3mm; the elliptical position in the figure is the position of the debonding defect detected by the method provided in the present application, and the red square is the actual position of the debonding defect, and there is a certain error between the detection positioning result and the actual debonding defect position, but the high response areas in the two figures are concentrated near the actual defect position, and the positioning relative error of the experimental result is less than 4.18%, which is lower than the 5% error threshold generally accepted in the industry. Therefore, the nonlinear damage index provided in the present application has good defect positioning capability, and it is proved that the imaging method provided in the present application has certain accuracy and reliability in the quantitative detection and positioning of micro debonding defects.

[0102] In order to better compare with the traditional tomography image result, the tomography image of the debonding defect with the size of 3x3mm using the traditional second harmonic method is also attached, as shown in Fig. 6. Due to the weak amplitude of the ultrasonic guided wave second harmonic, it is not easy to extract and is easily affected by noise, attenuation and system nonlinearity, the second harmonic nonlinear parameter results calculated in each path are unstable, resulting in the existence of difficult-to-eliminate artifacts in the image of the detection result of the traditional method, and the image cannot distinguish the specific position of the damage. The imaging method provided in the present application solves the above problems well. Figure 6

[0103] Example 2:

[0104] The ultrasonic probe in this embodiment adopts the layout mode of orthogonal scanning array, and the schematic diagram of the bonding damage sample, scanning area and scanning path direction is shown in Fig. 7 (wherein, the blue dashed line represents the scanning area, and the red area simulates the damage). Figure 7

[0105] In this embodiment, the test piece is a 16-layer quasi-isotropic carbon fiber reinforced composite plate, and the layering order is . Among them, the thickness of each layer of the composite plate is 0.14mm, and the total thickness is 2.24mm. The delamination damage is obtained by inserting a polytetrafluoroethylene film (thickness of 0.05mm) between the selected layers during the layering bonding process. The scanning range is a rectangular area with a size of 200x200, that is, the distance between the signal excitation end and the signal receiving end is 200mm, and the scanning step is 5mm each time. The excitation signal of the signal excitation end is selected as a sinusoidal pulse signal with a period number of 10 and a center frequency of 200kHz, which is modulated by a Hanning window. In the experiment, the step is set to scan and calculate the damage index for positioning imaging, and the result is shown in Fig. 5. Figure 8 ​​As shown: the actual shape and location of delamination damage has been clearly calibrated; the high-brightness red and orange color block areas presented in the image clearly indicate the presence of a large area of debonding defects inside the material, and the detection data of these areas are in good agreement with the physical dissection results, verifying the reliability of the detection method. It is worth noting that the light blue and green color block areas generated during the scanning process are actually artifacts caused by the superposition of multiple scanning paths. Such interference signals can be effectively excluded by setting appropriate threshold parameters, thereby ensuring the accuracy of the detection results. That is, using this method can clearly show the damage situation and location inside the component to be monitored.

[0106] 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 is only a relationship word determined for the purpose of describing the structural relationship of the components or elements of the present application, and is not intended to specify any component or element in the present application. It cannot be understood as a limitation on the present application. The terms such as "connected", "connected" and the like should be broadly understood, 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 it cannot be understood as a limitation on the present application.

[0107] 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 essential scope of the present application should also be within the protection scope of the present application.

Claims

1. A method of micro-damage tomography based on the non-linear ultrasonic static component damage index, characterized in that, Specifically comprising the following steps: S1. Selecting one of a circular array or an orthogonal scanning array to arrange sensors on the surface of the measured component; The circular array is arranged in a circular structure with a diameter of The number of array elements of the circular array is ​ The orthogonal scanning array is to take one face of the measured component as a scanning area and to arrange two sensors at two adjacent corner positions of the scanning area respectively; Wherein, the diameter of the circular array satisfies ; the spacing between the two sensors of the orthogonal scanning array satisfies ; wavelength , is the phase velocity of the signal excitation end transmission frequency, is the transmission frequency of the signal excitation end S2. Setting a signal excitation end and a signal receiving end; S3. Transmitting signals from the signal excitation end respectively and collecting received signals of the signal receiving end, transmitting the received signals to an oscilloscope through an amplifier, collecting signals uploaded by the oscilloscope to a PC data processing terminal and pre-processing errors of the collected signals; S4. Performing fast Fourier transform analysis on the signals pre-processed in S3 and obtaining static component energy values; S5. Calculate a non-linear impairment index : ; Wherein, is the static component energy under the low-amplitude excitation signal excitation; is the static component energy under the high-amplitude excitation signal excitation; is the amplification coefficient of the signal excitation end emission signal amplitude, that is, the ratio of the high and low amplitudes of the signal excitation end incident wave, ; S6. Based on the detection grid formed by the circular array or the orthogonal scanning array, the non-linear damage index is calculated As the parameter embedded RAPID ellipse positioning algorithm, the detection grid pixel value of the imaging area is calculated and filled to generate the micro-damage tomographic image.

2. The method of micro-damage tomography based on nonlinear ultrasonic static component damage index according to claim 1, characterized in that, In S2, the center frequencies of the sensors of the signal excitation end and the signal receiving end are both 500 kHz; The transmitting signals of the signal excitation end are narrow-band pulses modulated by a Hanning window and the transmitting frequency is 200 kHz-500 kHz.

3. The nonlinear ultrasonic static component damage index based micro-damage tomography method of claim 2, wherein, In S3, the signal transmission and signal collection specifically comprise: S3.

1. When the circular array is arranged, the signal collection process specifically comprises the following sub-steps: S3.1.1 Sequentially arrange the circular array... Each sensor serves as a signal excitation terminal, and the remaining... Each sensor serves as a signal receiver. S3.1.

2. Using a signal generator to transmit low-amplitude excitation signals and high-amplitude excitation signals to each sensor through an attenuator in turn for excitation, while collecting signals received by the remaining sensors; wherein, when each sensor is used as the signal excitation end, the signals received by the remaining sensors are collected repeatedly for not less than five times; S3.1.

3. Uploading the received signals obtained in S3.1.2 to a PC data processing terminal and calculating the average value of the repeatedly collected signals, thereby completing the pre-processing of accidental errors of the measurement results; S3.

2. When the orthogonal scanning array is arranged, the signal collection process specifically comprises the following sub-steps: S3.2.

1. Setting the signal excitation end at one corner of the scanning area and setting the signal receiving end at the other corner of the scanning area along the X-axis direction; S3.2.

2. Using a signal generator to transmit low-amplitude excitation signals and high-amplitude excitation signals to the signal excitation end through an attenuator for excitation, while collecting signals of the signal receiving end, thereby completing scanning of one acoustic path; S3.2.

3. Synchronously moving the signal excitation end and the signal receiving end along the Y-axis direction, the moving step of each scanning is 5 mm, and S3.2.2 is repeated to complete scanning along the Y-axis direction of the scanning area; wherein, the signals are collected repeatedly for not less than five times for each acoustic path scanning; S3.2.

4. Moving the signal excitation end back to the initial position and moving the signal receiving end to the corner opposite to the initial position; S3.2.

5. Using a signal generator to transmit low-amplitude excitation signals and high-amplitude excitation signals to the signal excitation end through an attenuator for excitation, while collecting signals of the signal receiving end, thereby completing scanning of one acoustic path; S3.2.

6. Synchronously moving the signal excitation end and the signal receiving end along the X-axis direction, the moving step of each scanning is 5 mm, and S3.2.5 is repeated to complete scanning along the X-axis direction of the scanning area; wherein, the signals are collected repeatedly for not less than five times for each acoustic path scanning; S3.2.7 The several received signals obtained in S3.2.3 and S3.2.6 are uploaded to the PC data processing terminal and the average value of the repeatedly collected signals of each acoustic path is calculated, thereby completing the preprocessing of the accidental error of all acoustic path measurement results.

4. The nonlinear ultrasonic static component damage index based micro-damage tomography method of claim 3, wherein, The voltage amplitude of the low-amplitude excitation signal ranges from 10 to 30 V; and the voltage amplitude of the high-amplitude excitation signal ranges from 50 to 80 V.

5. The nonlinear ultrasonic static component damage index based microdamage tomography method of claim 3, wherein, In S4, the average value of the error pre-processed collected signal in S3.1.3 or S3.2.7 is subjected to fast Fourier transform analysis, and the spectrum amplitude in the integral zero frequency band of 0-500 Hz is used to calculate and respectively.

6. The nonlinear ultrasonic static component damage index based microdamage tomography method of claim 5, wherein, In S6, the detection grid formed by the circular array or the orthogonal scanning array is a two-dimensional spatial grid, and each pixel point in the two-dimensional spatial grid corresponds to a spatial position in the component to be measured. a nonlinear damage index is calculated The nonlinear damage index is embedded into the RAPID ellipse positioning algorithm, and each pixel point in the two-dimensional space grid is calculated to obtain the comprehensive nonlinear response intensity of each pixel point, realize the visualization imaging and spatial reconstruction of the potential damage position and degree inside the measured component structure, and generate a micro-damage tomographic image; wherein each spatial position in the image reflects the probability of damage at the position through different colors, specifically: Case 1: The deep blue to light green region corresponds to low values, indicating that the material in this region is in good condition, no nonlinear response is found, and it is inferred to be in a nondestructive state; Case two: yellow to red region corresponds to high value, indicating that the response nonlinearity of this region under high amplitude excitation is significantly enhanced, which is inferred to be due to the presence of debonding, micro-cracks or fatigue damage; When the imaging region presents a strip-shaped distribution with a length-width ratio ≥ 4:1, it is inferred that there is a crack propagation path or fatigue damage along the length direction at this position; when the imaging region presents a circular or elliptical patch-shaped distribution, it is inferred that this is a debonding defect.

7. The nonlinear ultrasonic static component damage index based micro-damage tomography method of claim 4, wherein, The PC data processing terminal comprises a MATLAB signal processing module, a fast Fourier transform analysis module, a parameter extraction module and a wireless communication module. The signal excitation end, the signal receiving end, the signal generator, the attenuator, the amplifier and the oscilloscope are electrically connected to the PC data processing terminal.

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