A method for micro-crack detection based on nonlinear ultrasonic

Abstract

The application discloses a micro-crack detection method based on nonlinear ultrasonic, and relates to the technical field of micro-crack detection, and comprises the following steps: calling a historical micro-crack detection record of nonlinear ultrasonic, extracting an ultrasonic detection signal from a detection result, analyzing in combination with a use condition of a to-be-detected equipment and a historical measured equipment, and screening and extracting a target record from the detection record; capturing a micro-crack response signal interval of the target record, acquiring response signal intensities of each propagation mode of ultrasonic waves at different detection moments, and establishing a probability matrix of each part of the to-be-detected equipment; acquiring a to-be-measured part of the to-be-detected equipment, calculating display weights of each propagation mode, and implementing differential gain amplification on the response signals of each propagation mode. The application is helpful to improve micro-crack detection sensitivity, reduce signal distortion risk, and realize accurate and reliable early micro-crack identification by analyzing structural characteristics and crack propagation directions of different parts of the equipment and performing differential configuration of the propagation modes.

Description

Technical Field

[0001] This invention relates to the field of microcrack detection technology, specifically a microcrack detection method based on nonlinear ultrasound. Background Technology

[0002] During operation, thermal power units are susceptible to early microcracks in critical components due to complex operating conditions and environmental factors. Failure to detect and address these cracks in a timely manner can lead to serious safety hazards. Existing nonlinear ultrasonic testing technology can identify microcracks early through high-order harmonic response, effectively warning of defect propagation and ensuring safe equipment operation. However, ultrasonic guided waves contain different propagation modes, and the detection sensitivity of different modes varies significantly for different microcracks. Current technologies often adopt a uniform mode detection scheme for all parts of thermal power units without considering the structural characteristics and crack propagation direction of different parts of the unit for differentiated configuration. This can easily lead to insufficient detection sensitivity and signal distortion in some areas, making it difficult to achieve accurate and reliable early microcrack identification. Summary of the Invention

[0003] The purpose of this invention is to provide a microcrack detection method based on nonlinear ultrasound to solve the problems raised in the prior art.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] A microcrack detection method based on nonlinear ultrasound includes the following steps:

[0006] Retrieve historical nonlinear ultrasonic microcrack detection records, extract the detection time, tested equipment, and detection results corresponding to the detection records; obtain the current microcrack testing equipment, extract the ultrasonic detection signal from the historical detection results, perform matching analysis based on the usage status of the testing equipment and the historical tested equipment, and filter and extract target records from the detection records;

[0007] Capture the target record corresponding microcrack response signal range, obtain the response signal intensity of each propagation mode of ultrasonic waves at different detection times, and establish the probability matrix of each part of the device under test;

[0008] For the equipment to be tested, the crack direction of each part usually shows a certain pattern. This is because different parts of the pipeline have different stress characteristics and working conditions. The types of cracks that are prone to occur in different parts and the direction of extension have typical distribution characteristics. Therefore, the probability of longitudinal cracks, transverse cracks and oblique cracks in each part is significantly different. So the probability matrix of each part is different in this scheme.

[0009] The current test part of the device under test is obtained. Based on the probability matrix of the test part, the display weight of each propagation mode is calculated. According to the current display weight of each propagation mode, the response signal of each propagation mode is amplified with differentiated gain.

[0010] Preferably, the target record is extracted from the detection record, including:

[0011] Obtain the detection results corresponding to the detection record, extract and analyze the ultrasound detection signal, calculate the signal-to-noise ratio and waveform distortion rate, and extract the first marker record from the detection record based on the signal-to-noise ratio and waveform distortion rate;

[0012] Obtain the equipment under test corresponding to the test record, and determine the service life of the equipment under test and the equipment under test respectively; extract various environmental indicators related to microcrack initiation and propagation, and obtain the corresponding index values ​​of each environmental indicator in the actual use of the equipment under test and the equipment under test; extract the second marker record from the test record based on the service life and index values.

[0013] The detection record that is simultaneously the first and second marked record is taken as the target record.

[0014] The first marker record indicates that the data recorded in the record is reliable, and the second marker record indicates that the environmental conditions between the tested device and the device to be tested are matched. Therefore, extracting the target record can ensure that the historical data used is reliable and matches the environmental conditions of the device to be tested, thereby improving the accuracy and reliability of subsequent nonlinear ultrasonic test results.

[0015] Preferably, the first marker record extracted from the detection record includes:

[0016] The effective signal segment containing microcrack response in the ultrasonic test signal is extracted, and the second harmonic component is located through frequency domain transformation to obtain the maximum peak value of the second harmonic; the background signal segment without microcrack in the ultrasonic test signal is extracted, and the corresponding maximum noise amplitude is extracted; the signal-to-noise ratio (SNR) dB of the ultrasonic test signal is calculated based on the maximum peak value and the maximum noise amplitude.

[0017] The effective signal segment of the ultrasonic detection signal is subjected to Fourier transform to obtain the spectrum diagram. The fundamental amplitude and the amplitude of each higher harmonic are extracted, and the waveform distortion rate (THD) of the ultrasonic detection signal is calculated.

[0018] Calculate the normalized signal-to-noise ratio dB` and the normalized waveform distortion THD`. If dB`×THD` is greater than the preset threshold value, the corresponding detection record is used as the first marked record.

[0019] It should be noted that the signal-to-noise ratio (SNR) characterizes the quality of the signal. A higher SNR indicates that the ultrasonic detection signal is more reliable. The waveform distortion rate characterizes the degree to which the ultrasonic waveform deviates from a sine wave. A larger waveform distortion rate indicates that the possibility of microcracks is higher. Therefore, in this scheme, based on the normalized SNR dB` and the normalized waveform distortion THD`, reliable records can be extracted from the detection records, which are the first marked records.

[0020] Preferably, the extraction of the second marker record from the detection record includes:

[0021] Obtain several index values ​​of a certain environmental index m for the device under test and the device under test within the historical usage window, and construct the first and second histograms corresponding to the environmental index m.

[0022] Calculate the cosine similarity between the first and second histograms as the target value of environmental indicator m; pre-set the weights of various environmental indicators, multiply the target value of each environmental indicator by its corresponding weight, and then sum them to obtain the reliability value of the tested equipment.

[0023] If the equipment to be tested and the equipment under test have the same service life and the reliability value of the equipment under test is greater than the preset reliability threshold, the corresponding test record will be used as the second marker record.

[0024] Preferably, constructing the first and second histograms corresponding to environmental indicator m includes:

[0025] The environmental indicator m is used to divide several indicator intervals;

[0026] Obtain several index values ​​of environmental index m of the device under test within the historical usage window, count the number of index values ​​falling into each index interval, calculate the probability corresponding to each index interval, and construct the first histogram of environmental index m.

[0027] Obtain several index values ​​of environmental index m of the device under test within the historical usage window, count the number of index values ​​falling into each index interval, calculate the probability corresponding to each index interval, and construct a second histogram of environmental index m.

[0028] Preferably, the parts of the equipment to be tested are pipe parts, and the ultrasonic waves used are pipe ultrasonic guided waves, whose propagation mode types include longitudinal mode, bending mode and torsional mode.

[0029] For pipeline components, the longitudinal mode of ultrasound propagates along the pipeline axis, with the particle vibration direction parallel to the pipeline axis; the bending mode propagates in combination with the circumferential and axial directions, with the particle vibration direction perpendicular to the pipeline axis; and the torsional mode propagates along the pipeline axis, with the particle vibration direction twisting along the pipeline circumferentially.

[0030] Preferably, a probability matrix is ​​established for each part of the device to be tested, including:

[0031] Extract a detection time within the microcrack response signal interval corresponding to the target record, extract the second harmonic amplitude of each propagation mode of the ultrasonic wave at the detection time, and take the second harmonic amplitude of the longitudinal mode as R1, the second harmonic amplitude of the bending mode as R2, and the second harmonic amplitude of the torsional mode as R3.

[0032] Based on the comparison of the values ​​of R1, R2 and R3, the reliable direction corresponding to the detection moment is determined. The reliable direction is one of the longitudinal crack, transverse crack and oblique crack.

[0033] Obtain the reliable direction at multiple detection times for the same location, count the number of longitudinal cracks, transverse cracks and oblique cracks belonging to the reliable direction, calculate the probability of longitudinal cracks, transverse cracks and oblique cracks belonging to the reliable direction, establish the probability matrix of the location, and obtain the probability matrix of each part of the equipment to be tested.

[0034] Preferably, determining the reliable direction corresponding to the detection moment includes:

[0035] The first condition is that R2 is greater than K1×R1, where K1 is the first constant; the second condition is that R1 is greater than K2×R2, where K2 is the second constant; and the third condition is that the variance among R1, R2, and R3 is less than a preset variance threshold.

[0036] When only condition one is met, the reliable direction corresponding to the detection time is recorded as a longitudinal crack; when only condition two is met, the reliable direction corresponding to the detection time is recorded as a transverse crack; and when only condition three is met, the reliable direction corresponding to the detection time is recorded as an oblique crack.

[0037] Preferably, the calculation of the display weights for each propagation mode includes:

[0038] Obtain several historical detection times corresponding to the part to be tested, and obtain the second harmonic amplitude values ​​of the longitudinal mode, bending mode and torsional mode when the reliable direction is longitudinal crack, transverse crack and oblique crack respectively at each detection time. Obtain the target values ​​of the longitudinal mode, bending mode and torsional mode corresponding to longitudinal crack, transverse crack and oblique crack respectively, and establish the target matrix.

[0039] In this scheme, the response signals of each propagation mode are amplified differently according to the display weight of each propagation mode. The larger the display weight, the higher the gain amplification of the corresponding response signal, and the more prominent the rule is in the display interface. This realizes the differentiated display and highlighting of the detection characteristics of different propagation modes, which facilitates intuitive identification of the sensitive response of each mode to microcracks, enhances the display of key mode information, and improves the intuitiveness and accuracy of microcrack judgment.

[0040] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention provides a microcrack detection method based on nonlinear ultrasound, comprising: retrieving historical microcrack detection records using nonlinear ultrasound; extracting ultrasound detection signals from the detection results; analyzing the usage status of the device under test and historically tested devices; selecting and extracting target records from the detection records; capturing the microcrack response signal range of the target records; obtaining the response signal intensity of each propagation mode of ultrasound at different detection times; establishing a probability matrix for each part of the device under test; obtaining the current test part of the device under test; calculating the display weight of each propagation mode; and implementing differentiated gain amplification for the response signals of each propagation mode. This invention, by analyzing the structural characteristics and crack propagation direction of different parts of the device and performing differentiated configuration of propagation modes, helps to improve the sensitivity of microcrack detection, reduce the risk of signal distortion, enhance the display of key modal information, improve the intuitiveness and accuracy of microcrack judgment, and contribute to accurate and reliable early microcrack identification. Attached Figure Description

[0041] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic flowchart of a microcrack detection method based on nonlinear ultrasound according to the present invention. Detailed Implementation

[0043] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0044] Example: Figure 1 As shown, this invention provides a technical solution for microcrack detection based on nonlinear ultrasound, comprising the following steps:

[0045] Retrieve historical microcrack detection records using nonlinear ultrasonic technology. These records refer to the early microcrack diagnosis records of the tested equipment in thermal power units using nonlinear ultrasonic technology. Extract the detection time, tested equipment, and detection results corresponding to the detection records. The detection results here include nonlinear ultrasonic response results. Since nonlinear ultrasound consists of high-order harmonics, the response results specifically include the amplitude information of each harmonic.

[0046] The process involves acquiring the current microcrack detection equipment, extracting ultrasonic detection signals from historical detection results, performing a matching analysis between the current equipment and historically tested equipment, and filtering and extracting target records from the detection logs. Specifically:

[0047] Obtain the detection results corresponding to the detection records, extract and analyze the ultrasound detection signals, calculate the signal-to-noise ratio and waveform distortion rate, and extract the first marker record from the detection records based on the signal-to-noise ratio and waveform distortion rate, including:

[0048] In this embodiment, the effective signal segment containing the microcrack response in the ultrasonic detection signal is extracted, and the second harmonic component is located through frequency domain transformation to obtain the maximum peak value A of the second harmonic. signal Extract the background signal segment from the ultrasonic testing signal where there are no microcracks, and extract the corresponding maximum noise amplitude A. noise The signal-to-noise ratio of the ultrasonic detection signal is calculated based on the maximum peak value and the maximum noise amplitude.

[0049]

[0050] The effective signal segment of the ultrasonic detection signal is subjected to Fourier transform to obtain the spectrum. The fundamental amplitude and the amplitudes of each higher harmonic are extracted. The fundamental amplitude is A1, and the amplitudes of the second, third, ..., Nth harmonics are A2, A3, ..., A1, respectively. N The waveform distortion rate of the ultrasonic detection signal was calculated:

[0051]

[0052] Calculate the normalized signal-to-noise ratio dB` and the normalized waveform distortion THD`. If dB`×THD` is greater than the preset threshold, the corresponding detection record is used as the first marked record. The threshold here is 0.5.

[0053] It should be noted that the signal-to-noise ratio (SNR) characterizes the quality of the signal. A higher SNR indicates that the ultrasonic detection signal is more reliable. The waveform distortion rate characterizes the degree to which the ultrasonic waveform deviates from a sine wave. A larger waveform distortion rate indicates that the possibility of microcracks is higher. Therefore, in this scheme, based on the normalized SNR dB` and the normalized waveform distortion THD`, reliable records can be extracted from the detection records, which are the first marked records.

[0054] Obtain the equipment under test corresponding to the test record, and determine the service life of both the equipment under test and the equipment being tested, for example, three years and five years. Extract various environmental indicators related to microcrack initiation and propagation. Environmental indicators characterize various condition parameters in the environment in which the equipment is located that affect microcrack initiation and propagation. By analyzing environmental indicators, the similarity and difference characteristics of the environmental conditions and operating parameters of the equipment under test and historical tested equipment can be characterized, thereby providing a basis for the reliability comparison of test results. In this embodiment, environmental indicators include temperature, internal pressure of the equipment, and vibration intensity, etc. The internal pressure of the equipment can be obtained through a pressure gauge, and the vibration intensity can be obtained through an accelerometer. Obtain the corresponding indicator values ​​of each environmental indicator in the actual use of the equipment under test and the equipment being tested. Based on the service life and indicator values, extract the second marker record from the test record, including:

[0055] Several index values ​​of a certain environmental index m are obtained for both the device under test and the device being tested within a historical usage window. A first and second histogram corresponding to environmental index m are constructed. The histogram construction here includes:

[0056] Based on the environmental indicator m, several indicator intervals are divided. In this embodiment, the environmental indicator m refers to temperature. The indicator intervals are divided into equal intervals of 5°C, such as 10-15°C, 15-20°C, 30-35°C, etc., thus dividing the indicator intervals into several intervals.

[0057] Obtain several index values ​​of environmental index m of the device under test within the historical usage window, count the number of index values ​​falling into each index interval, calculate the probability corresponding to each index interval based on the ratio of the number of index values ​​in each index interval to the total number of index values, and construct the first histogram of environmental index m. The vertical axis of the first histogram is the probability, and the horizontal axis is each index interval. The method for constructing the second histogram described below can also refer to this method.

[0058] Obtain several index values ​​of environmental index m of the device under test within the historical usage window, count the number of index values ​​falling into each index interval, calculate the probability corresponding to each index interval, and construct a second histogram of environmental index m.

[0059] The cosine similarity between the first and second histograms is calculated using existing technology, with the cosine similarity used as the target value of the environmental indicator m. The larger the target value, i.e., the larger the cosine similarity, the more similar the first and second histograms are, thus indicating that the environmental conditions and operating parameters of the device under test and the device being tested are closer.

[0060] Various environmental indicators are pre-set with weights. The target value of each environmental indicator is multiplied by its corresponding weight, and then summed to obtain the reliability value of the equipment under test. The formula is as follows:

[0061]

[0062] Where M represents the number of environmental indicators, and W... m Let Q be the weight of the m-th environmental indicator. m The target value for the m-th environmental indicator is given. If the service life of the device to be tested and the device under test are the same and the reliability value of the device under test is greater than the preset reliability threshold, the corresponding test record will be used as the second marker record.

[0063] The detection record that is simultaneously the first marker record and the second marker record is used as the target record. The first marker record indicates that the data recorded in the record is reliable, and the second marker record indicates that the environmental conditions between the tested device and the device to be tested are matched. Therefore, extracting the target record can ensure that the historical data used is reliable and matches the environmental conditions of the device to be tested, thereby improving the accuracy and reliability of the subsequent nonlinear ultrasonic detection results.

[0064] The target is captured to record the corresponding microcrack response signal range, and the response signal intensity of each propagation mode of ultrasound at different detection times is obtained to establish the probability matrix of each part of the device under test.

[0065] The various parts of the equipment to be tested are pipeline sections, and the ultrasonic waves used are pipeline ultrasonic guided waves. The propagation modes include longitudinal mode, bending mode, and torsional mode. For pipeline sections, the longitudinal mode of the ultrasonic wave propagates along the pipeline axis, and the direction of particle vibration is parallel to the pipeline axis. The bending mode propagates in combination with the axial direction along the pipeline circumference, and the direction of particle vibration is perpendicular to the pipeline axis. The torsional mode propagates along the pipeline axis, and the direction of particle vibration is torsional along the pipeline circumference. The longitudinal mode, bending mode, and torsional mode in this solution are common modes in the prior art, and will not be described in detail here.

[0066] Establish the probability matrix for each part of the device to be tested, including:

[0067] Extract a detection time within the microcrack response signal interval corresponding to the target record, extract the second harmonic amplitude of each propagation mode of the ultrasonic wave at the detection time, and take the second harmonic amplitude of the longitudinal mode as R1, the second harmonic amplitude of the bending mode as R2, and the second harmonic amplitude of the torsional mode as R3.

[0068] Based on the comparison of R1, R2, and R3 values, the reliable direction corresponding to this detection moment is determined. The reliable direction is one of the following: longitudinal crack, transverse crack, and oblique crack. A longitudinal crack is a crack whose extension direction is parallel to the pipe axis; a transverse crack is a crack whose extension direction is perpendicular to the pipe axis; and an oblique crack is a spiral or obliquely distributed crack whose extension direction is inclined relative to the pipe axis. Specifically:

[0069] The first condition is that R2 is greater than K1×R1, where K1 is the first constant. In this embodiment, K1=5. Since the longitudinal crack is a crack whose extension direction is parallel to the pipe axis, the particle vibration direction of the bending mode will cut through the crack. However, the longitudinal mode is parallel to the crack and will not break the crack. Therefore, the bending mode is more sensitive to the longitudinal crack, while the longitudinal mode is not. As a result, there will be a significant difference in the second harmonic amplitude. Therefore, the first condition needs to be set as R2 being greater than K1×R1.

[0070] Condition two is that R1 is greater than K2×R2, where K2 is the second constant. In this embodiment, K2=3. Since the transverse crack is a crack whose extension direction is perpendicular to the pipe axis, the particle vibration direction of the longitudinal mode will cut through the crack. Therefore, the longitudinal mode is more sensitive to the longitudinal crack, while the bending mode is less sensitive to the transverse crack. Therefore, it is necessary to set condition two as R1 being greater than K2×R2.

[0071] Condition 3 is that the variance between R1, R2 and R3 is less than the preset variance threshold. For oblique cracks, the longitudinal mode, bending mode and torsional mode will all interact effectively with the crack surface and can all excite obvious contact nonlinearity and high-order harmonic response. Therefore, they are all sensitive to oblique cracks. Therefore, it is necessary to set condition 3 that the variance between R1, R2 and R3 is less than the preset variance threshold.

[0072] When only condition one is met, the reliable direction corresponding to the detection time is recorded as a longitudinal crack; when only condition two is met, the reliable direction corresponding to the detection time is recorded as a transverse crack; and when only condition three is met, the reliable direction corresponding to the detection time is recorded as an oblique crack.

[0073] Obtain the reliable direction at multiple detection times for the same location, count the number of longitudinal cracks, transverse cracks and oblique cracks belonging to the reliable direction, calculate the probability of longitudinal cracks, transverse cracks and oblique cracks belonging to the reliable direction, establish the probability matrix of the location, and obtain the probability matrix of each part of the equipment to be tested.

[0074] For the equipment under test, the crack direction of each part usually shows a certain pattern. This is because different parts of the pipeline have different stress characteristics and working conditions. The types of cracks that are prone to occur in different parts and the direction of extension have typical distribution characteristics. Therefore, the probability of longitudinal cracks, transverse cracks and oblique cracks in each part is significantly different. So the probability matrix of each part is different in this scheme.

[0075] For example, if the number of longitudinal cracks, transverse cracks, and diagonal cracks belonging to reliable directions for this location are 7, 1, and 2 respectively, then the probabilities of longitudinal cracks, transverse cracks, and diagonal cracks belonging to reliable directions are 0.7, 0.1, and 0.2 respectively. The probability matrix for this location is established as follows:

[0076]

[0077] Wherein, P1, P2, and P3 represent the probabilities that the longitudinal crack, transverse crack, and oblique crack belong to the reliable direction, respectively.

[0078] Obtain the current test part of the device under test, and calculate the display weight of each propagation mode based on the probability matrix of the test part, specifically:

[0079] Obtain several historical detection times corresponding to the part under test. For each detection time, when the reliable direction is longitudinal crack, transverse crack, and oblique crack, obtain the second harmonic amplitude values ​​of the longitudinal mode, bending mode, and torsional mode. Obtain the target values ​​of the longitudinal mode, bending mode, and torsional mode corresponding to longitudinal crack, transverse crack, and oblique crack, respectively, and establish the target matrix. For example, as follows:

[0080] Obtain the second harmonic amplitudes of the longitudinal modes when the crack direction is longitudinal for several reliable directions, calculate the average second harmonic amplitude, and normalize the average second harmonic amplitude using the sigmoid function to obtain the target value N of the longitudinal mode corresponding to the longitudinal crack. 11 The second harmonic amplitudes of the bending modes are obtained when the reliable direction of the crack is longitudinal. The average second harmonic amplitude is calculated and normalized to obtain the target value N of the bending mode corresponding to the longitudinal crack. 12 Where, the target value N 11 and target value N 12 The values ​​range from 0 to 1.

[0081] By analogy, the target value N of the torsional mode corresponding to the longitudinal crack is obtained. 13 The target value N of the longitudinal mode corresponding to the transverse crack is obtained. 21 The target value N of the bending mode corresponding to the transverse crack is obtained. 22 The target value N of the torsional mode corresponding to the transverse crack is obtained. 23The target value N of the longitudinal mode corresponding to the oblique crack is obtained. 31 The target value N of the bending mode corresponding to the oblique crack is obtained. 32 The target value N of the torsional mode corresponding to the oblique crack is obtained. 33 .

[0082] The established target matrix is ​​as follows:

[0083]

[0084] The probability matrix is ​​multiplied by the target matrix, and the display weights of the longitudinal mode, bending mode and torsional mode are determined based on the multiplication result.

[0085] Multiplying the probability matrix E1 and the target matrix E2, we obtain the following matrix:

[0086]

[0087] V1, V2, and V3 are used as the display weights for the longitudinal mode, bending mode, and torsional mode, respectively.

[0088] In this scheme, differentiated gain amplification is applied to the response signals of each propagation mode according to the display weight of each current propagation mode. The larger the display weight, the higher the gain amplification factor of the corresponding response signal, and the more prominent it is in the display interface. This achieves differentiated display and emphasis of the detection characteristics of different propagation modes. For example, the larger the display weight, the greater the brightness or vividness of the corresponding propagation mode, and the more obvious the display. Or, if the amplitude of the displayed waveform = the original amplitude * the amplification factor, then the larger the display weight, the larger the amplification factor, and the more prominent the data of that mode is displayed. This facilitates intuitive identification of the sensitive response of each mode to microcracks, enhances the display of key mode information, and improves the intuitiveness and accuracy of microcrack judgment.

[0089] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0090] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0091] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A microcrack detection method based on nonlinear ultrasound, characterized in that, Includes the following steps: Retrieve historical nonlinear ultrasonic microcrack detection records, extract the detection time, tested equipment, and detection results corresponding to the detection records; obtain the current microcrack testing equipment, extract the ultrasonic detection signal from the historical detection results, perform matching analysis based on the usage status of the testing equipment and the historical tested equipment, and filter and extract target records from the detection records; Capture the target record corresponding microcrack response signal range, obtain the response signal intensity of each propagation mode of ultrasonic waves at different detection times, and establish the probability matrix of each part of the device under test; The current test part of the device under test is obtained. Based on the probability matrix of the test part, the display weight of each propagation mode is calculated. According to the current display weight of each propagation mode, the response signal of each propagation mode is amplified by differential gain.

2. The microcrack detection method based on nonlinear ultrasound according to claim 1, characterized in that, Target records are extracted from the detection records, including: Obtain the detection results corresponding to the detection record, extract and analyze the ultrasound detection signal, calculate the signal-to-noise ratio and waveform distortion rate, and extract the first marker record from the detection record based on the signal-to-noise ratio and waveform distortion rate; Obtain the equipment under test corresponding to the test record, and determine the service life of the equipment under test and the equipment under test respectively; extract various environmental indicators related to microcrack initiation and propagation, and obtain the corresponding index values ​​of each environmental indicator in the actual use of the equipment under test and the equipment under test; extract the second marker record from the test record based on the service life and index values. The detection record that is simultaneously the first and second marked record is taken as the target record.

3. The microcrack detection method based on nonlinear ultrasound according to claim 2, characterized in that, Extract the first marker record from the detection record, including: The effective signal segment containing microcrack response in the ultrasonic test signal is extracted, and the second harmonic component is located through frequency domain transformation to obtain the maximum peak value of the second harmonic; the background signal segment without microcrack in the ultrasonic test signal is extracted, and the corresponding maximum noise amplitude is extracted; the signal-to-noise ratio (SNR) dB of the ultrasonic test signal is calculated based on the maximum peak value and the maximum noise amplitude. The effective signal segment of the ultrasonic detection signal is subjected to Fourier transform to obtain the spectrum diagram. The fundamental amplitude and the amplitude of each higher harmonic are extracted, and the waveform distortion rate (THD) of the ultrasonic detection signal is calculated. Calculate the normalized signal-to-noise ratio dB` and the normalized waveform distortion THD`. If dB`×THD` is greater than the preset threshold value, the corresponding detection record is used as the first marked record.

4. The microcrack detection method based on nonlinear ultrasound according to claim 2, characterized in that, Extract the second marker record from the detection record, including: Obtain several index values ​​of a certain environmental index m for the device under test and the device under test within the historical usage window, and construct the first and second histograms corresponding to the environmental index m. Calculate the cosine similarity between the first and second histograms as the target value of environmental indicator m; pre-set the weights of various environmental indicators, multiply the target value of each environmental indicator by its corresponding weight, and then sum them to obtain the reliability value of the tested equipment. If the equipment to be tested and the equipment under test have the same service life and the reliability value of the equipment under test is greater than the preset reliability threshold, the corresponding test record will be used as the second marker record.

5. The microcrack detection method based on nonlinear ultrasound according to claim 4, characterized in that, Construct the first and second histograms for environmental indicator m, including: The environmental indicator m is used to divide several indicator intervals; Obtain several index values ​​of environmental index m of the device under test within the historical usage window, count the number of index values ​​falling into each index interval, calculate the probability corresponding to each index interval, and construct the first histogram of environmental index m. Obtain several index values ​​of environmental index m of the device under test within the historical usage window, count the number of index values ​​falling into each index interval, calculate the probability corresponding to each index interval, and construct a second histogram of environmental index m.

6. The microcrack detection method based on nonlinear ultrasound according to claim 1, characterized in that, The various parts of the equipment to be tested are pipe parts, and the ultrasonic waves used are pipe ultrasonic guided waves, whose propagation mode types include longitudinal mode, bending mode and torsional mode.

7. The microcrack detection method based on nonlinear ultrasound according to claim 6, characterized in that, Establish the probability matrix for each part of the device to be tested, including: Extract a detection time within the microcrack response signal interval corresponding to the target record, extract the second harmonic amplitude of each propagation mode of the ultrasonic wave at the detection time, and take the second harmonic amplitude of the longitudinal mode as R1, the second harmonic amplitude of the bending mode as R2, and the second harmonic amplitude of the torsional mode as R3. Based on the comparison of the values ​​of R1, R2 and R3, the reliable direction corresponding to the detection moment is determined. The reliable direction is one of the longitudinal crack, transverse crack and oblique crack. Obtain the reliable direction at multiple detection times for the same location, count the number of longitudinal cracks, transverse cracks and oblique cracks belonging to the reliable direction, calculate the probability of longitudinal cracks, transverse cracks and oblique cracks belonging to the reliable direction, establish the probability matrix of the location, and obtain the probability matrix of each part of the equipment to be tested.

8. The microcrack detection method based on nonlinear ultrasound according to claim 7, characterized in that, Determining the reliable direction corresponding to this detection moment includes: The first condition is that R2 is greater than K1×R1, where K1 is the first constant; the second condition is that R1 is greater than K2×R2, where K2 is the second constant; and the third condition is that the variance among R1, R2, and R3 is less than a preset variance threshold. When only condition one is met, the reliable direction corresponding to the detection time is recorded as a longitudinal crack; when only condition two is met, the reliable direction corresponding to the detection time is recorded as a transverse crack; and when only condition three is met, the reliable direction corresponding to the detection time is recorded as an oblique crack.

9. A microcrack detection method based on nonlinear ultrasound according to claim 7, characterized in that, Calculate the display weights for each propagation mode, including: Obtain several historical detection times corresponding to the part to be tested, and obtain the second harmonic amplitude values ​​of the longitudinal mode, bending mode and torsional mode when the reliable direction is longitudinal crack, transverse crack and oblique crack respectively at each detection time. Obtain the target values ​​of the longitudinal mode, bending mode and torsional mode corresponding to longitudinal crack, transverse crack and oblique crack respectively, and establish the target matrix. The probability matrix is ​​multiplied by the target matrix, and the display weights of the longitudinal mode, bending mode and torsional mode are determined based on the multiplication result.

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