A concrete dam crack angle adjustable nondestructive testing method and system

Abstract

This invention discloses a non-destructive testing method and system for concrete dam cracks with adjustable angles, belonging to the field of crack detection technology. It addresses the problem of reduced acoustic impedance differences at crack interfaces by dividing the dam body under test into sections and incorporating the detection of water level depth and P-wave echo characteristics to determine the degree of crack closure. Based on the crack closure state, sections are screened and marked, identifying sections with potential acoustic transparency risks. Furthermore, by combining the crack's stress direction information, the incident deflection angle of the ultrasonic probe is adjusted to change the sound wave incident direction and excite the echo response, thereby disrupting the acoustic transparency of the crack closure interface. The angle compensation effect is verified through comparative analysis of P-wave and S-wave echo characteristics, forming a closed-loop non-destructive testing process. This enables reliable detection of hidden cracks under high water levels without damaging the dam structure.

Description

Technical Field

[0001] This invention relates to the field of crack detection technology, and more specifically, to a non-destructive testing method and system for adjustable crack angles in concrete dams. Background Technology

[0002] As an important hydraulic engineering structure, concrete dams are subjected to a long-term service environment of high water level, high hydrostatic pressure, and complex temperature and stress fields. Cracks of different sizes and orientations are prone to form inside and on the surface of the dam body. In the early stages, these cracks often exhibit characteristics such as small crack width, openings being squeezed closed by water pressure, and irregular orientation. They are particularly hidden under high water level operating conditions, posing a potential threat to the overall safety assessment and operational risk warning of the dam body.

[0003] The existing technology has the following shortcomings:

[0004] Currently, existing technologies for non-destructive testing of cracks in concrete dams mostly employ ultrasonic testing with a fixed incident angle. These methods rely on a single longitudinal wave echo amplitude or detection parameters set by human experience for crack identification. This approach struggles to effectively determine the crack closure state under high water pressure and to consider the acoustic response characteristics of different crack orientations. Consequently, the acoustic impedance difference at the crack interface decreases, and the ultrasonic reflection and scattering effects weaken. Therefore, this paper proposes a non-destructive testing method and system for concrete dam cracks with an adjustable angle.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a non-destructive testing method and system for concrete dam cracks with adjustable angles. This method utilizes a crack closure state discrimination mechanism based on water level information and ultrasonic echo characteristics of the dam section, combined with an adaptive adjustment strategy for the probe incident angle in the direction of crack stress, to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a non-destructive testing method for adjustable crack angle in concrete dams, comprising the following steps:

[0008] Step S1: Divide the dam body area to be tested into sections, collect the detection water level depth of each section, calculate the hydraulic compaction coefficient using the detection water level depth, and transmit ultrasonic waves in the dam body area to be tested and obtain longitudinal wave echo signals.

[0009] Step S2: After processing the reflected echo amplitude of the longitudinal wave echo signal, the signal transmission characteristics of the segment are generated. The crack closure status of the segment is analyzed by combining the hydraulic compression coefficient and the signal transmission characteristics. The segment is then screened and marked based on the crack closure status.

[0010] Step S3: Retrieve the current ultrasonic probe deflection angle, detect the crack stress direction of the marked and divided sections to construct crack direction information, set the incident deflection angle according to the crack direction information and correct the probe deflection angle.

[0011] Step S4: The ultrasonic probe with the probe deflection angle corrected is used to perform secondary ultrasonic wave emission on the marked and divided section, collect the shear wave echo signal and generate the crack echo peak value, and combine the longitudinal wave echo signal to analyze the signal-to-noise ratio enhancement trend and determine whether to output a crack manifestation prompt.

[0012] In a preferred embodiment, in step S1, the area of ​​the dam body to be measured is divided into multiple segments according to a preset segment division interval;

[0013] The water level depth of each section is collected by a water level gauge, and the water density of the dam body area to be measured is retrieved from the hydrological medium parameter database. The product of the water density, the water level depth and the gravitational acceleration constant is used as the hydraulic compaction characteristic.

[0014] The hydraulic compaction coefficient is obtained after standardizing the hydraulic compaction characteristics;

[0015] Ultrasonic longitudinal wave emission operations are performed sequentially on each segment within the dam body area to be tested. The longitudinal wave emission is completed by the ultrasonic probe under the current preset incident angle. The corresponding longitudinal wave echo signal is obtained through the echo acquisition channel. The longitudinal wave echo signal contains multiple amplitude sequences.

[0016] In a preferred embodiment, in step S2, the echo time window of the segmented segment in the longitudinal wave echo signal is retrieved through the echo time window index table, and the amplitude extraction operation of the longitudinal wave echo signal is performed within the echo time window.

[0017] The amplitude of the reflected echo is obtained by subtracting the maximum amplitude from the minimum amplitude of the longitudinal wave echo signal.

[0018] The signal transmission characteristics are calculated by retrieving the reference reflected echo amplitude from the reference echo library and combining the reference reflected echo amplitude with the reflected echo amplitude.

[0019] In a preferred embodiment, in step S2, the product of the hydraulic compaction coefficient and the signal transmission characteristics is used as the crack closure index for dividing the sections.

[0020] The crack closure index is compared with a preset crack closure threshold to analyze the crack closure status of the divided sections:

[0021] If the crack closure index is greater than the preset crack closure threshold, the crack closure status of the divided section is determined to be closed.

[0022] Conversely, the crack closure status of the divided section is determined to be non-closed.

[0023] The sections where the crack is closed are marked.

[0024] In a preferred embodiment, in step S3, the ultrasonic detection system is controlled to retrieve the current ultrasonic probe deflection angle, which is the angle between the probe beam center axis and the normal direction of the dam surface.

[0025] Within the marked and divided sections, based on the current P-wave detection conditions, P-wave echo signals are acquired for the same crack action area along at least two mutually orthogonal spatial sampling directions.

[0026] By comparing the arrival times of the main echoes of the longitudinal wave echo signals at different sampling locations, the crack stress direction is generated and the crack direction information is calculated. The crack direction information is the crack direction angle.

[0027] In a preferred embodiment, in step S3, the target incident deflection angle is constructed based on the crack orientation angle, and the target incident deflection angle is set to satisfy: ;

[0028] in, For the target incident deflection angle, The angle of the crack direction;

[0029] Calculate the difference between the target incident deflection angle and the probe deflection angle to obtain the probe deflection angle correction amount;

[0030] The control probe angle adjustment mechanism performs deflection angle correction on the ultrasonic probe, so that the corrected probe deflection angle is the sum of the probe deflection angle and the probe deflection angle correction amount.

[0031] In a preferred embodiment, in step S4, the corrected probe deflection angle is used as the incident angle parameter for ultrasonic wave emission, and secondary ultrasonic wave emission is performed on the marked segment.

[0032] During the secondary ultrasonic emission process, the ultrasonic detection system simultaneously acquires the transverse wave echo signal formed by the reflection from the crack interface, and performs time window interception and envelope detection processing on the transverse wave echo signal to extract the main echo peak value of the transverse wave echo signal.

[0033] Similarly, the peak value of the main echo signal of the longitudinal wave echo corresponding to the segment divided by the same mark is obtained and stored;

[0034] Background noise was introduced based on time window truncation, and the root mean square (RMS) of the background noise amplitude of the longitudinal wave echo signal and the root mean square (RMS) of the background noise amplitude of the transverse wave echo signal were calculated respectively.

[0035] In a preferred embodiment, in step S4, the P-wave signal-to-noise ratio is obtained by dividing the peak value of the main echo of the P-wave echo signal by the root mean square amplitude of the background noise of the P-wave echo signal.

[0036] The shear wave signal-to-noise ratio is obtained by dividing the peak value of the main echo of the shear wave echo signal by the root mean square value of the background noise amplitude of the shear wave echo signal.

[0037] The signal-to-noise ratio (SNR) enhancement trend is defined as the ratio of the transverse wave SNR to the longitudinal wave SNR.

[0038] When the signal-to-noise ratio enhancement trend is greater than or equal to the preset signal-to-noise ratio enhancement judgment threshold, it is determined that there is a crack structure in the current marked segment, and a crack display prompt is output.

[0039] When the signal-to-noise ratio (SNR) enhancement trend is less than the preset SNR enhancement judgment threshold, the system will not output a crack manifestation prompt and will maintain the current detection result.

[0040] A non-destructive testing system for concrete dam cracks with adjustable angles includes a section detection module, a closure determination module, a direction construction module, and a visualization analysis module. The functions of each module are as follows:

[0041] The section detection module is used to divide the dam body area under test into sections, collect the detection water level depth of each section, calculate the hydraulic compaction coefficient based on the detection water level depth, and collect the longitudinal wave echo signal at the same time.

[0042] The closure determination module is used to extract the reflected echo amplitude of the longitudinal wave echo signal, calculate the signal transmission characteristics based on the reflected echo amplitude, fuse the hydraulic compaction coefficient with the signal transmission characteristics to analyze the crack closure status, and screen and mark the divided sections based on the crack closure status.

[0043] The orientation construction module is used to retrieve the current ultrasonic probe deflection angle, detect the crack stress direction of the marked and divided sections, construct crack orientation information based on the crack stress direction, calculate and output the incident deflection angle, and correct the probe deflection angle.

[0044] The crack visualization analysis module is used to perform secondary ultrasonic transmission on the marked and divided sections using the corrected probe deflection angle, collect shear wave echo signals and generate crack echo peak values, analyze the signal-to-noise ratio enhancement trend in combination with longitudinal wave echo signals, and determine whether to output a crack visualization prompt based on the analysis results.

[0045] The technical effects and advantages of this invention are as follows:

[0046] This invention divides the dam body under test into sections and introduces the detection of water level depth and P-wave echo characteristics to determine the degree of crack closure. Based on the crack closure status, sections are screened and marked, and sections with acoustic transparency risks are identified. Furthermore, by combining the stress direction information of the crack, the incident deflection angle of the ultrasonic probe is adjusted to change the incident direction of the sound wave to excite the echo response, thereby disrupting the acoustic transparency of the crack closure interface. Through comparative analysis of P-wave and S-wave echo characteristics, the angle compensation effect is verified, forming a closed-loop non-destructive testing process. This enables reliable detection of hidden cracks under high water levels without damaging the dam structure, improving the accuracy and stability of crack identification. Attached Figure Description

[0047] Figure 1 This is a diagram illustrating the implementation process of a non-destructive testing system for adjustable crack angles in concrete dams, as described in this invention.

[0048] Figure 2 This is a flowchart illustrating a non-destructive testing method for adjustable crack angles in concrete dams according to the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] This invention divides the dam body under test into sections and introduces the detection of water level depth and P-wave echo characteristics to determine the degree of crack closure. Based on the crack closure status, sections are screened and marked, and sections with acoustic transparency risks are identified. Furthermore, by combining the stress direction information of the crack, the incident deflection angle of the ultrasonic probe is adjusted to change the incident direction of the sound wave to excite the echo response, thereby disrupting the acoustic transparency of the crack closure interface. Through comparative analysis of P-wave and S-wave echo characteristics, the angle compensation effect is verified, forming a closed-loop non-destructive testing process. This enables reliable detection of hidden cracks under high water levels without damaging the dam structure.

[0051] Example 1, such as Figure 1 As shown, a non-destructive testing method for concrete dam cracks with adjustable angles includes the following steps:

[0052] Step S1: Divide the dam body area to be tested into sections, collect the detection water level depth of each section, calculate the hydraulic compaction coefficient using the detection water level depth, and transmit ultrasonic waves in the dam body area to be tested and obtain longitudinal wave echo signals.

[0053] Step S2: After processing the reflected echo amplitude of the longitudinal wave echo signal, the signal transmission characteristics of the segment are generated. The crack closure status of the segment is analyzed by combining the hydraulic compression coefficient and the signal transmission characteristics. The segment is then screened and marked based on the crack closure status.

[0054] Step S3: Retrieve the current ultrasonic probe deflection angle, detect the crack stress direction of the marked and divided sections to construct crack direction information, set the incident deflection angle according to the crack direction information and correct the probe deflection angle.

[0055] Step S4: The ultrasonic probe with the probe deflection angle corrected is used to perform secondary ultrasonic wave emission on the marked and divided section, collect the shear wave echo signal and generate the crack echo peak value, and combine the longitudinal wave echo signal to analyze the signal-to-noise ratio enhancement trend and determine whether to output a crack manifestation prompt.

[0056] The specific implementation is as follows:

[0057] In step S1, when the dam body under test is operating under high water level conditions, the crack interface is easily closed due to hydraulic pressure, causing the ultrasonic longitudinal wave to change from reflection to transmission at the crack, resulting in the crack being invisible at the acoustic level. This leads to the problem of hidden missed detection under high water level conditions. Based on this, the degree of closure of the crack under the current operating conditions is determined by detecting the water level depth and the characteristics of the longitudinal wave echo.

[0058] The area of ​​the dam to be tested is divided into multiple segments according to the preset segment division interval. The preset segment division interval can be set according to the transmission coverage of a single ultrasonic wave and the echo time window resolution requirements.

[0059] The water level depth of each section is collected by a water level gauge. The water level depth is the vertical water column height between the upstream water level elevation of the area to be measured and the representative elevation of the corresponding section. The greater the water level depth, the deeper the water level coverage of the section, and the easier it is for the crack to close.

[0060] The water density in the dam area to be measured is retrieved from the hydrological medium parameter database, and the product of the water density, the detected water level depth, and the gravitational acceleration constant is used as the hydraulic compaction characteristic.

[0061] After standardizing the hydraulic compaction characteristics, the hydraulic compaction coefficient is obtained. The larger the value, the higher the external water pressure, and the easier it is for the crack surface to close. This leads to enhanced transmission of ultrasonic longitudinal waves at the crack interface and a decrease in the amplitude of the reflected echo.

[0062] Ultrasonic longitudinal wave emission operations are performed sequentially on each segment within the dam body area to be tested. The longitudinal wave emission is completed by the ultrasonic probe under the current preset incident angle. After the longitudinal wave emission, the corresponding longitudinal wave echo signal is obtained through the echo acquisition channel. The longitudinal wave echo signal is a time-domain electrical signal received after the ultrasonic wave is emitted, propagates along the concrete medium, and is reflected at different interfaces. Its signal amplitude corresponds to the magnitude of the transducer output voltage caused when the echo reaches the ultrasonic probe, and contains multiple amplitude sequences.

[0063] Among them, the ultrasonic probe is an ultrasonic transducer used to transmit and receive ultrasonic signals. It is used to transmit ultrasonic waves into the divided section under a preset incident angle and receive the echo signals formed by the reflection.

[0064] It should be noted that a water level gauge is a water level monitoring and sensing device used to measure the water level elevation upstream of a dam and output water level elevation data; a hydrological medium parameter database is a parameter database used to store water medium parameters; the standardization processing methods include, but are not limited to, standard linear transformation based on interval scaling, statistical Z-Score standardization method, or normalization method based on nonlinear mapping function. The application methods of standardization processing will not be elaborated here; the preset incident angle is used to limit the initial incident direction of ultrasonic waves relative to the divided section, and can be set according to the surface normal direction of the divided section; the echo acquisition channel is the signal receiving and processing channel corresponding to the ultrasonic probe.

[0065] In step S2, the echo time window of the segment in the longitudinal wave echo signal is retrieved through the echo time window index table. The echo time window is used to limit the calculation range of the reflected echo amplitude to avoid interference from aggregate scattering echo and multiple reflected echoes on the reflection amplitude calculation. The echo time window index table takes the target reflection position of the segment, the ultrasonic longitudinal wave propagation speed and the trigger time of ultrasonic wave emission as input parameters. The corresponding echo time window is generated by calculating the longitudinal wave round-trip propagation delay. The echo time window is then stored after establishing an index association with the corresponding segment identifier.

[0066] Within the echo time window, amplitude extraction is performed on the longitudinal wave echo signal to obtain the reflected echo amplitude corresponding to the segment. The difference between the maximum amplitude and the minimum amplitude of the longitudinal wave echo signal is used to obtain the reflected echo amplitude.

[0067] The amplitude of the reflected echo reflects the reflection intensity at the corresponding depth position of the divided section. The larger the amplitude of the reflected echo, the stronger the reflection component at the crack interface, and the crack can be distinguished under the longitudinal wave detection conditions. The smaller the amplitude of the reflected echo, the more the crack interface tends to be in close contact under the hydraulic pressure.

[0068] The reference reflected echo amplitude is retrieved by the reference echo library. The reference reflected echo amplitude is the reflected echo amplitude obtained in the reference section without the influence of hydraulic compression, and is used as a reference quantity for the longitudinal wave reflection capability.

[0069] The signal transmission characteristics are calculated by combining the amplitude of the reflected echo and the amplitude of the reflected echo. ,in, For the amplitude of the reflected echo, For reference, the amplitude of the reflected echo, This refers to signal transmission characteristics;

[0070] The greater the signal transmission characteristics, the greater the decrease in the longitudinal wave reflection component at the corresponding depth position of the segment relative to the reference state, and the more the crack tends to close under the hydraulic pressure.

[0071] The product of the hydraulic compaction coefficient and the signal transmission characteristics is used as the crack closure index for dividing the sections. The crack closure index is compared with a preset crack closure threshold to analyze the crack closure status of the divided sections.

[0072] If the crack closure index is greater than the preset crack closure threshold, the crack closure status of the divided section is determined to be closed.

[0073] Conversely, the crack closure status of the divided section is determined to be non-closed.

[0074] The sections where the crack is closed are marked.

[0075] It should be noted that the reference echo library is a benchmark parameter library used to store the characteristics of longitudinal wave reflection echoes under conditions where they are not affected by hydraulic pressure; the preset crack closure threshold can be set according to the crack closure index distribution corresponding to the confirmed crack closure division section under the historical high water level operation conditions of the dam body area to be tested.

[0076] In step S3, after marking the divided sections, the process proceeds to the stage of crack orientation identification and adaptive correction of the ultrasonic probe incident angle.

[0077] First, the ultrasonic testing system retrieves the current ultrasonic probe deflection angle, which is the angle between the probe's acoustic beam center axis and the normal direction of the dam surface, and serves as the reference parameter for subsequent angle correction.

[0078] It should be noted that an ultrasonic testing system refers to an integrated set of non-destructive testing devices deployed on the surface of a concrete dam, used to perform functions such as ultrasonic wave transmission, reception, signal processing, and probe attitude control.

[0079] Within the marked and demarcated sections, based on the current P-wave detection conditions, P-wave echo signals are acquired along at least two mutually orthogonal spatial sampling directions for the same crack action area. By comparing the arrival times of the main echoes of the P-wave echo signals at different sampling locations, the crack stress direction is generated and the crack orientation information is calculated to reflect the directional influence of the crack on the ultrasonic propagation path under hydraulic pressure conditions.

[0080] Specifically, detection points are set up along two mutually orthogonal survey lines within the marked and divided sections. The arrival time of the main echo of the longitudinal wave echo signal at each measurement point is obtained. The arrival time difference of the echoes of adjacent measurement points is calculated based on the arrival time of the main echoes, and the spatial distance between adjacent measurement points is also calculated.

[0081] Based on the spatial spacing between adjacent measuring points and the corresponding echo arrival time difference, the crack stress direction is generated, and the crack stress direction is characterized in the form of a feature vector: ;

[0082] in, The direction of crack stress, The spatial spacing between adjacent measurement points along the first sampling direction. This represents the echo arrival time difference corresponding to the first sampling direction. The spatial spacing between adjacent measurement points along the second sampling direction. This represents the echo arrival time difference corresponding to the second sampling direction;

[0083] The crack stress direction eigenvector is used to quantitatively describe the equivalent acoustic conduction hindrance of the crack interface in different spatial directions.

[0084] Based on this, the crack orientation information is calculated using the crack stress direction feature vector, and the crack orientation information is defined as the crack orientation angle, with the specific expression as follows:

[0085] ;

[0086] in, The angle of the crack direction. The spatial spacing between adjacent measurement points along the first sampling direction. This represents the echo arrival time difference corresponding to the first sampling direction. The spatial spacing between adjacent measurement points along the second sampling direction. This represents the echo arrival time difference corresponding to the second sampling direction. It is the arctangent function.

[0087] The crack orientation angle is used to characterize the main extension direction of the crack within the dam body inspection plane.

[0088] After obtaining the crack orientation angle, the target incident deflection angle is constructed based on the crack orientation information, and the target incident deflection angle is set to satisfy:

[0089] ;

[0090] in, For the target incident deflection angle, The angle representing the direction of the crack.

[0091] The above-mentioned setting expression makes the modified ultrasonic incident direction orthogonal to the crack direction, thereby weakening the acoustic transparency of the crack closure interface and enhancing the acoustic response sensitivity of the crack closure interface.

[0092] Finally, the difference between the target incident deflection angle and the probe deflection angle is calculated to obtain the probe deflection angle correction amount;

[0093] The control probe angle adjustment mechanism performs deflection angle correction on the ultrasonic probe, so that the corrected probe deflection angle is the sum of the probe deflection angle and the probe deflection angle correction amount, that is, consistent with the target incident deflection angle value.

[0094] It should be noted that the probe angle adjustment mechanism is an execution unit set between the ultrasonic probe and the detection support structure, used to controllably adjust the spatial incident direction of the ultrasonic probe. It is used to quantitatively adjust the deflection attitude of the ultrasonic probe after receiving the angle correction control command.

[0095] The corrected probe deflection angle is locked and recorded as the incident angle parameter for subsequent secondary ultrasonic testing, which is used to characterize the crack orientation and incident detection relationship corresponding to the current segment.

[0096] In step S4, after correcting the ultrasonic probe deflection angle and locking the corrected probe deflection angle, the secondary ultrasonic detection stage based on the corrected incident angle is entered.

[0097] At this point, the corrected probe deflection angle, as the incident angle parameter of the ultrasonic wave emission, is used to perform enhanced detection on the marked and divided sections targeting the crack closure interface.

[0098] The ultrasonic testing system, while maintaining the corrected probe deflection angle, performs a secondary ultrasonic wave emission on the marked sections. The secondary emission is still performed by the same ultrasonic probe, but the incident angle is deflected relative to the normal direction of the dam surface. This causes the ultrasonic waves, originally incident as longitudinal waves, to undergo mode conversion at the concrete-crack interface, generating ultrasonic signals that propagate as shear waves.

[0099] During the secondary ultrasonic emission process, the ultrasonic detection system simultaneously acquires the shear wave echo signal formed by reflection from the crack interface, and performs time window truncation and envelope detection processing on the shear wave echo signal to extract the main echo peak value. The main echo peak value of the shear wave echo signal is defined as the crack echo peak value, which is used to characterize the reflection response intensity of the crack closure interface to shear waves.

[0100] It should be noted that the shear wave echo signal refers to the shear wave echo signal generated by the mode conversion of the longitudinal wave at the medium interface under inclined incident conditions. It has higher sensitivity to the normal contact state and minute opening and closing changes of the crack interface. The time window interception processing refers to the process by which the ultrasonic detection system calculates the theoretical arrival time interval of the echo corresponding to the crack interface based on the known sound path length, medium wave velocity and corrected incident angle after acquiring the shear wave echo signal. The target analysis time window is set in the shear wave echo signal with the theoretical arrival time interval as the center to remove irrelevant signals from the dam surface reflection, structural boundary reflection and environmental noise. The envelope detection processing refers to the envelope extraction operation of the shear wave echo signal within the target analysis time window. That is, by taking the absolute value of the original echo signal and smoothing it, the envelope curve reflecting the trend of echo energy change is obtained. This converts the high-frequency oscillation signal into an amplitude response feature that can be directly quantified, which facilitates the stable extraction of the peak value of the main shear wave echo to characterize the reflection intensity of the shear wave at the crack closure interface.

[0101] Simultaneously, envelope detection processing is performed on the longitudinal wave echo signal within the corresponding time window to obtain and store the main echo peak value of the longitudinal wave echo signal corresponding to the segment divided by the same mark, and use it as a reference detection signal for comparative analysis with the transverse wave echo signal.

[0102] To quantitatively compare the detection quality of P-wave and S-wave echo signals, background noise is introduced. This background noise is derived from the completed time window truncation process. Specifically, when performing time window truncation on either the P-wave or S-wave echo signal, in addition to the target analysis time window used to extract the main echo of the crack, a noise reference time window is selected within the same echo signal that does not overlap with the target analysis time window in time and does not correspond to the crack interface in space. Within the noise reference time window, amplitude statistical calculations are performed on the P-wave and S-wave echo signals, and the root mean square (RMS) values ​​of their echo amplitudes are calculated respectively. This yields the RMS background noise amplitude of the P-wave and S-wave echo signals, characterizing the background noise level under the corresponding detection conditions.

[0103] Based on this, the signal-to-noise ratio (SNR) enhancement trend is analyzed, and the SNR of the P-wave echo signal and the SNR of the S-wave echo signal are calculated separately to obtain the P-wave SNR and the SNR of the S-wave. The P-wave SNR and the SNR of the S-wave are defined as follows:

[0104] ; ;

[0105] in, For longitudinal wave signal-to-noise ratio, For shear wave signal-to-noise ratio, The peak value of the main echo of the longitudinal wave echo signal. The peak value of the main echo of the shear wave echo signal. The root mean square of the background noise amplitude of the longitudinal wave echo signal. The root mean square of the background noise amplitude of the shear wave echo signal.

[0106] Based on the above signal-to-noise ratio calculation results, the signal-to-noise ratio enhancement trend is further defined as the ratio of the transverse wave signal-to-noise ratio to the longitudinal wave signal-to-noise ratio, in order to quantitatively describe the degree of enhancement of the acoustic response of the crack interface relative to the initial longitudinal wave detection state after the probe deflection angle is corrected.

[0107] When the signal-to-noise ratio enhancement trend is greater than or equal to the preset signal-to-noise ratio enhancement judgment threshold, it is determined that the corrected incident angle has effectively weakened the acoustic transparency characteristics of the crack closure interface, causing the crack interface to change from a state dominated by longitudinal wave transmission to a state dominated by shear wave reflection, thereby confirming that there is a crack structure in the current marked segment.

[0108] At this point, the output crack visualization prompts are displayed, and crack contour information is generated based on the distribution of shear wave echo peaks at different spatial sampling locations to characterize the spatial extension morphology of the crack within the divided section.

[0109] When the signal-to-noise ratio enhancement trend is less than the preset signal-to-noise ratio enhancement judgment threshold, it is determined that the current incident angle adjustment has failed to effectively destroy the acoustic transparency state of the crack closure interface, no crack manifestation prompt is output, and the current detection result is kept for subsequent comprehensive analysis or repeated correction detection.

[0110] It should be noted that the signal-to-noise ratio (SNR) enhancement threshold is a quantitative criterion used to distinguish whether the correction of the incident angle substantially changes the acoustic response state of the crack interface. It is determined based on the statistical characteristics of reference sections without cracks or with low-closure cracks. Specifically, in the preprocessing stage before detection, multiple reference sections with known absence of cracks or stable crack openings are selected. P-wave and S-wave echo signals are acquired under the conditions of the initial probe deflection angle and the corrected probe deflection angle, respectively. The corresponding SNR enhancement trend sequences are calculated, and statistical analysis is performed on the SNR enhancement trends to obtain their mean and standard deviation. The sum of the mean and standard deviation is defined as the SNR enhancement threshold.

[0111] Example 2, as Figure 2As shown, a non-destructive testing system for concrete dam cracks with adjustable angles is used to implement a non-destructive testing method for concrete dam cracks with adjustable angles. The system includes a section detection module, a closure determination module, a direction construction module, and a visualization analysis module. The functions of each module are as follows:

[0112] The section detection module is used to divide the dam body area under test into sections, collect the detection water level depth of each section, calculate the hydraulic compaction coefficient based on the detection water level depth, and collect the longitudinal wave echo signal at the same time.

[0113] The closure determination module is used to extract the reflected echo amplitude of the longitudinal wave echo signal, calculate the signal transmission characteristics based on the reflected echo amplitude, fuse the hydraulic compaction coefficient with the signal transmission characteristics to analyze the crack closure status, and screen and mark the divided sections based on the crack closure status.

[0114] The orientation construction module is used to retrieve the current ultrasonic probe deflection angle, detect the crack stress direction of the marked and divided sections, construct crack orientation information based on the crack stress direction, calculate and output the incident deflection angle, and correct the probe deflection angle.

[0115] The crack visualization analysis module is used to perform secondary ultrasonic transmission on the marked and divided sections using the corrected probe deflection angle, collect shear wave echo signals and generate crack echo peak values, analyze the signal-to-noise ratio enhancement trend in combination with longitudinal wave echo signals, and determine whether to output a crack visualization prompt based on the analysis results.

[0116] Finally, it should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0117] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0118] In this document, the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that terms such as “comprising / including” or “having” specify the presence of the stated features, integrals, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integrals, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0119] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0120] The above description of the disclosed embodiments will enable those skilled in the art to make or use various modifications to these embodiments. It will be readily apparent to those skilled in the art that the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A non-destructive testing method for concrete dam cracks with adjustable angle, characterized in that: Includes the following steps: Step S1: Divide the dam body area to be tested into sections, collect the detection water level depth of each section, calculate the hydraulic compaction coefficient using the detection water level depth, and transmit ultrasonic waves in the dam body area to be tested and obtain longitudinal wave echo signals. In step S1, the area of ​​the dam body to be measured is divided into multiple segments according to the preset segment division interval; The water level depth of each section is collected by a water level gauge, and the water density of the dam body area to be measured is retrieved from the hydrological medium parameter database. The product of the water density, the water level depth and the gravitational acceleration constant is used as the hydraulic compaction characteristic. The hydraulic compaction coefficient is obtained after standardizing the hydraulic compaction characteristics; Ultrasonic longitudinal wave emission operations are performed sequentially on each divided section within the dam body area to be tested. The longitudinal wave emission is completed by the ultrasonic probe under the current preset incident angle condition. The corresponding longitudinal wave echo signal is obtained through the echo acquisition channel. The longitudinal wave echo signal contains multiple amplitude sequences. Step S2: After processing the reflected echo amplitude of the longitudinal wave echo signal, the signal transmission characteristics of the segment are generated. The crack closure status of the segment is analyzed by combining the hydraulic compression coefficient and the signal transmission characteristics. The segment is then screened and marked based on the crack closure status. In step S2, the product of the hydraulic compaction coefficient and the signal transmission characteristics is used as the crack closure index for dividing the section; The crack closure index is compared with a preset crack closure threshold to analyze the crack closure status of the divided sections: If the crack closure index is greater than the preset crack closure threshold, the crack closure status of the divided section is determined to be closed. Conversely, the crack closure status of the divided section is determined to be non-closed. The sections where the cracks are closed are marked. Step S3: Retrieve the current ultrasonic probe deflection angle, detect the crack stress direction of the marked and divided sections to construct crack direction information, set the incident deflection angle according to the crack direction information and correct the probe deflection angle. Step S4: The ultrasonic probe with the probe deflection angle corrected is used to perform secondary ultrasonic wave emission on the marked and divided section, collect the shear wave echo signal and generate the crack echo peak value, and combine the longitudinal wave echo signal to analyze the signal-to-noise ratio enhancement trend and determine whether to output a crack manifestation prompt.

2. The non-destructive testing method for adjustable crack angle in concrete dams according to claim 1, characterized in that: In step S2, the echo time window of the segment in the longitudinal wave echo signal is retrieved through the echo time window index table, and the amplitude extraction operation is performed on the longitudinal wave echo signal within the echo time window; The amplitude of the reflected echo is obtained by subtracting the maximum amplitude from the minimum amplitude of the longitudinal wave echo signal. The signal transmission characteristics are calculated by retrieving the reference reflected echo amplitude from the reference echo library and combining the reference reflected echo amplitude with the reflected echo amplitude.

3. The non-destructive testing method for adjustable crack angle in concrete dams according to claim 1, characterized in that: In step S3, the ultrasonic detection system is controlled to retrieve the current ultrasonic probe deflection angle, which is the angle between the probe beam center axis and the normal direction of the dam surface. Within the marked and divided sections, based on the current P-wave detection conditions, P-wave echo signals are acquired for the same crack action area along at least two mutually orthogonal spatial sampling directions. By comparing the arrival times of the main echoes of the longitudinal wave echo signals at different sampling locations, the crack stress direction is generated and the crack direction information is calculated. The crack direction information is the crack direction angle.

4. The non-destructive testing method for adjustable crack angle in concrete dams according to claim 3, characterized in that: In step S3, the target incident deflection angle is constructed based on the crack orientation angle, and the target incident deflection angle is set to satisfy: ; in, For the target incident deflection angle, The angle of the crack direction; Calculate the difference between the target incident deflection angle and the probe deflection angle to obtain the probe deflection angle correction amount; The control probe angle adjustment mechanism performs deflection angle correction on the ultrasonic probe, so that the corrected probe deflection angle is the sum of the probe deflection angle and the probe deflection angle correction amount.

5. The non-destructive testing method for adjustable crack angle in concrete dams according to claim 1, characterized in that: In step S4, the corrected probe deflection angle is used as the incident angle parameter for ultrasonic wave emission, and secondary ultrasonic wave emission is performed on the marked segment. During the secondary ultrasonic emission process, the ultrasonic detection system simultaneously acquires the transverse wave echo signal formed by the reflection from the crack interface, and performs time window interception and envelope detection processing on the transverse wave echo signal to extract the main echo peak value of the transverse wave echo signal. Similarly, the peak value of the main echo signal of the longitudinal wave echo corresponding to the segment divided by the same mark is obtained and stored; Background noise was introduced based on time window truncation, and the root mean square (RMS) of the background noise amplitude of the longitudinal wave echo signal and the root mean square (RMS) of the background noise amplitude of the transverse wave echo signal were calculated respectively.

6. The non-destructive testing method for adjustable crack angle in concrete dams according to claim 5, characterized in that: In step S4, the signal-to-noise ratio of the longitudinal wave is obtained by dividing the peak value of the main echo of the longitudinal wave echo signal by the root mean square value of the background noise amplitude of the longitudinal wave echo signal. The shear wave signal-to-noise ratio is obtained by dividing the peak value of the main echo of the shear wave echo signal by the root mean square value of the background noise amplitude of the shear wave echo signal. The signal-to-noise ratio (SNR) enhancement trend is defined as the ratio of the transverse wave SNR to the longitudinal wave SNR. When the signal-to-noise ratio enhancement trend is greater than or equal to the preset signal-to-noise ratio enhancement judgment threshold, it is determined that there is a crack structure in the current marked segment, and a crack display prompt is output. When the signal-to-noise ratio (SNR) enhancement trend is less than the preset SNR enhancement judgment threshold, the system will not output a crack manifestation prompt and will maintain the current detection result.

7. A non-destructive testing system for concrete dam cracks with adjustable angle, used to implement the non-destructive testing method for concrete dam cracks with adjustable angle as described in any one of claims 1-6, characterized in that: It includes a segment detection module, a closure determination module, a direction construction module, and an explicit analysis module. The functions of each module are as follows: The section detection module is used to divide the dam body area under test into sections, collect the detection water level depth of each section, calculate the hydraulic compaction coefficient based on the detection water level depth, and collect the longitudinal wave echo signal at the same time. The area of ​​the dam to be measured is divided into multiple sections according to the preset section division spacing; The water level depth of each section is collected by a water level gauge, and the water density of the dam body area to be measured is retrieved from the hydrological medium parameter database. The product of the water density, the water level depth and the gravitational acceleration constant is used as the hydraulic compaction characteristic. The hydraulic compaction coefficient is obtained after standardizing the hydraulic compaction characteristics; Ultrasonic longitudinal wave emission operations are performed sequentially on each divided section within the dam body area to be tested. The longitudinal wave emission is completed by the ultrasonic probe under the current preset incident angle condition. The corresponding longitudinal wave echo signal is obtained through the echo acquisition channel. The longitudinal wave echo signal contains multiple amplitude sequences. The closure determination module is used to extract the reflected echo amplitude of the longitudinal wave echo signal, calculate the signal transmission characteristics based on the reflected echo amplitude, fuse the hydraulic compaction coefficient with the signal transmission characteristics to analyze the crack closure status, and screen and mark the divided sections based on the crack closure status. The product of the hydraulic compaction coefficient and the signal transmission characteristics is used as the crack closure index for dividing the sections. The crack closure index is compared with a preset crack closure threshold to analyze the crack closure status of the divided sections: If the crack closure index is greater than the preset crack closure threshold, the crack closure status of the divided section is determined to be closed. Conversely, the crack closure status of the divided section is determined to be non-closed. The sections where the cracks are closed are marked. The orientation construction module is used to retrieve the current ultrasonic probe deflection angle, detect the crack stress direction of the marked and divided sections, construct crack orientation information based on the crack stress direction, calculate and output the incident deflection angle, and correct the probe deflection angle. The crack visualization analysis module is used to perform secondary ultrasonic transmission on the marked and divided sections using the corrected probe deflection angle, collect shear wave echo signals and generate crack echo peak values, analyze the signal-to-noise ratio enhancement trend in combination with longitudinal wave echo signals, and determine whether to output a crack visualization prompt based on the analysis results.

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