Micro-crack positioning method and system of nonlinear ultrasonic mixing signal

Abstract

The invention provides a microcrack positioning method and system of a nonlinear ultrasonic mixing signal, and relates to the technical field of nondestructive testing. The method comprises the following steps: exciting signals with different frequencies into a test piece for resonance, collecting echo signals generated by signal resonance at a plurality of measurement points, performing Fourier transform processing on the plurality of echo signals to generate a prediction spectrogram, and calculating a prediction nonlinear coefficient of a microcrack position according to the prediction spectrogram; the method comprises the following steps: performing displacement processing on a simulation test piece model, simulating material displacement caused by propagation of a frequency mixing signal needing to be excited in a material, obtaining a displacement relation graph, performing Fourier transform processing, generating a simulation spectrogram, and calculating a simulation nonlinear coefficient of a simulation microcrack position according to the simulation spectrogram. The simulated nonlinear coefficient is used for verifying and predicting the nonlinear coefficient to obtain the position of the micro-crack, so that the micro-crack is accurately positioned, the micro-crack can be effectively identified and positioned, and a high-sensitivity and high-resolution detection result is provided.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of nondestructive testing, and in particular to a micro-crack locating method and system of a nonlinear ultrasonic mixing signal. Background Art

[0002] Under the action of alternating cyclic stress, mechanical equipment and parts will produce tiny cracks at local high stress points after a period of time. These germinated microcracks will continue to expand under the action of load until the structural equipment breaks. When ultrasonic waves propagate in a solid medium containing microcracks, the presence of cracks makes the medium no longer uniform and linear in local areas, but has a nonlinear effect and generates mixed frequency signals. Therefore, it is of great significance to measure and locate the microcracks formed in the early stage of the equipment in combination with mixed frequency signals. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a micro-crack locating method and system using a nonlinear ultrasonic mixing signal in view of the deficiencies in the prior art.

[0004] The technical solution of the present invention to solve the above technical problems is as follows:

[0005] A microcrack location method using a nonlinear ultrasonic mixing signal comprises the following steps:

[0006] Divide a plurality of measuring points based on the position of the test piece, use a nonlinear ultrasonic instrument to generate sinusoidal signals of different frequencies, respectively, excite the sinusoidal signals of corresponding frequencies into the test piece through excitation sensors deployed at different sides of the test piece, and receive echo signals of different sinusoidal signals at the plurality of measuring points through designated excitation sensors;

[0007] Performing Fourier transform processing on the plurality of echo signals to obtain a predicted spectrum diagram, extracting predicted amplitudes corresponding to the plurality of measurement points from the predicted spectrum diagram, and performing nonlinear calculation on the plurality of predicted amplitudes respectively to obtain nonlinear coefficients corresponding to the plurality of measurement points;

[0008] Importing a simulation specimen model, dividing a plurality of simulation measurement points based on the position of the simulation specimen model, performing displacement processing on the plurality of simulation measurement points of the simulation specimen model, and obtaining displacement relationship images corresponding to the plurality of simulation measurement points;

[0009] Performing Fourier transform processing on the plurality of displacement relationship images to obtain a simulation spectrum diagram, extracting predicted simulation amplitudes corresponding to the plurality of simulation measurement points from the simulation spectrum diagram, and performing nonlinear calculation on the plurality of predicted simulation amplitudes to obtain a plurality of simulation nonlinear coefficients corresponding to the plurality of simulation measurement points;

[0010] The plurality of nonlinear coefficients are compared with the plurality of simulation nonlinear coefficients, and when the comparison results are consistent, the microcrack positions are determined according to the plurality of nonlinear coefficients.

[0011] Another technical solution of the present invention to solve the above technical problems is as follows:

[0012] A micro-crack location system of nonlinear ultrasonic mixing signal, comprising:

[0013] A prediction module is used to divide a plurality of measurement points based on the position of the test piece, generate sinusoidal signals of different frequencies respectively by using a nonlinear ultrasonic instrument, excite sinusoidal signals of corresponding frequencies into the test piece respectively by using excitation sensors disposed at different side ends of the test piece, receive echo signals of different sinusoidal signals at a plurality of the measurement points by using a designated excitation sensor, perform Fourier transform processing on the plurality of the echo signals to obtain a prediction spectrum diagram, extract prediction amplitudes corresponding to the plurality of the measurement points from the prediction spectrum diagram, perform nonlinear calculation on the plurality of the prediction amplitudes respectively, and obtain nonlinear coefficients corresponding to the plurality of the measurement points;

[0014] A simulation module, used for importing a simulation specimen model, dividing a plurality of simulation measurement points based on the position of the simulation specimen model, performing displacement processing on the plurality of simulation measurement points of the simulation specimen model to obtain displacement relationship images corresponding to the plurality of simulation measurement points, performing Fourier transform processing on the plurality of displacement relationship images to obtain a simulation spectrum diagram, extracting predicted simulation amplitudes corresponding to the plurality of simulation measurement points from the simulation spectrum diagram, performing nonlinear calculations on the plurality of predicted simulation amplitudes respectively, and obtaining a plurality of simulation nonlinear coefficients corresponding to the plurality of simulation measurement points;

[0015] The verification module is used to compare the multiple nonlinear coefficients with the multiple simulation nonlinear coefficients, and when the comparison results are consistent, determine the microcrack positions according to the multiple nonlinear coefficients.

[0016] The beneficial effects of the present invention are as follows: the test piece to be inspected is divided into regions by dividing the measurement points, the size of the nonlinear coefficient of each measurement point is calculated to pre-position the region, and the microcrack position is obtained, and then the identified microcrack position is verified in combination with the result of the simulation specimen model detection, so that the microcracks can be effectively identified and located, and high-sensitivity and high-resolution detection results can be provided, which can reduce the waste caused by premature replacement of non-destructive materials of equipment and thus reduce maintenance costs, and at the same time, potential structural damage can be discovered, thereby ensuring the safety and reliability of the structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A flow chart of a microcrack locating method using a nonlinear ultrasonic mixing signal provided by an embodiment of the present invention;

[0018] Figure 2 A structural diagram of signal transmission in a microcrack locating method provided by an embodiment of the present invention;

[0019] Figure 3 A schematic diagram of the test piece measurement points and measurement area provided by an embodiment of the present invention;

[0020] Figure 4 A module block diagram of a micro-crack location system for nonlinear ultrasonic mixing signals provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0022] In the prior art, the relationship between the plastic damage and fatigue degree of the material and the mixing parameters was studied by using the nonlinear effect of body waves, and it was found that the mixing parameters increased with the increase of material damage or fatigue degree. Based on the experimental system for collinear ultrasonic mixing measurement, the mixing signal obtained by dual spectrum analysis was processed to obtain the relationship between the nonlinear coefficient and the frequency change of ultrasonic excitation. The study conducted experiments on aluminum plates with three different fatigue cycles, and used the harmonic method to detect and record the amplitudes of the fundamental wave and the second harmonic of the three materials. The data was analyzed and processed to obtain the nonlinear coefficient and the second harmonic amplitude, which were compared and analyzed with the fatigue damage of the material. The possibility of Lamb wave mixing technology for crack location and imaging was studied. The results showed that the crack image obtained by the mixing signal was basically consistent with the actual crack image, which verified the feasibility of the mixing location technology. The study used nonlinear collinear opposite-side mixing technology to locate the structural damage of metal materials, and combined with the time-frequency domain analysis method to achieve the location of structural damage. The study conducted experiments on aluminum alloy specimens with fatigue cracks of five different depths, and concluded that within a certain crack depth, the crack depth is positively correlated with the difference frequency nonlinear coefficient and the sum frequency nonlinear coefficient. By fitting curve analysis of the two sets of experimental data, the corresponding crack depth prediction model was established.

[0023] like Figure 1 As shown, a microcrack location method of a nonlinear ultrasonic mixing signal provided by an embodiment of the present invention includes the following steps:

[0024] Divide a plurality of measuring points based on the position of the test piece, use a nonlinear ultrasonic instrument to generate sinusoidal signals of different frequencies, respectively, excite the sinusoidal signals of corresponding frequencies into the test piece through excitation sensors deployed at different sides of the test piece, and receive echo signals of different sinusoidal signals at the plurality of measuring points through designated excitation sensors;

[0025] Performing Fourier transform processing on the plurality of echo signals to obtain a predicted spectrum diagram, extracting predicted amplitudes corresponding to the plurality of measurement points from the predicted spectrum diagram, and performing nonlinear calculation on the plurality of predicted amplitudes respectively to obtain nonlinear coefficients corresponding to the plurality of measurement points;

[0026] Importing a simulation specimen model, dividing a plurality of simulation measurement points based on the position of the simulation specimen model, performing displacement processing on the plurality of simulation measurement points of the simulation specimen model, and obtaining displacement relationship images corresponding to the plurality of simulation measurement points;

[0027] Performing Fourier transform processing on the plurality of displacement relationship images to obtain a simulation spectrum diagram, extracting predicted simulation amplitudes corresponding to the plurality of simulation measurement points from the simulation spectrum diagram, and performing nonlinear calculation on the plurality of predicted simulation amplitudes to obtain a plurality of simulation nonlinear coefficients corresponding to the plurality of simulation measurement points;

[0028] The plurality of nonlinear coefficients are compared with the plurality of simulation nonlinear coefficients, and when the comparison results are consistent, the microcrack positions are determined according to the plurality of nonlinear coefficients.

[0029] In the embodiment of the present invention, the test piece to be inspected is divided into regions by dividing the measurement points, the size of the nonlinear coefficient of each measurement point is calculated to pre-position the region, and then combined with the results of the simulation test, micro cracks can be effectively identified and located, and high-sensitivity and high-resolution test results can be provided, which can reduce the waste caused by premature replacement of non-destructive materials for mechanical devices, thereby reducing maintenance costs, and at the same time, potential structural damage to mechanical devices can be discovered, thereby ensuring the safety and reliability of the structure. Therefore, the present invention has good reference significance in engineering practice.

[0030] Preferably, if Figure 2 As shown, it also includes equipment construction and specimen preparation steps, as follows:

[0031] The equipment used included a computer, a nonlinear ultrasound machine (RAM-5000-SNAP), an attenuator, a low-pass filter (i.e., filter), a signal excitation sensor (i.e., transducer), a duplexer, a high-pass filter, and an oscilloscope;

[0032] Connect a computer to a nonlinear ultrasonic instrument, connect the RF output terminal 1 (for low-frequency sinusoidal signals) of the nonlinear ultrasonic instrument to the first attenuator, the low-pass filter and the first excitation sensor in sequence, connect the RF output terminal 2 (for high-frequency sinusoidal signals) of the nonlinear ultrasonic instrument to the second attenuator, the duplexer and the second excitation sensor in sequence, stick the excitation sensor to both sides of the x-axis direction of the coordinate system where the test piece is located through a medical ultrasonic coupling agent, connect the duplexer to the high-pass filter and the RF input terminal of the nonlinear ultrasonic instrument in sequence, and connect the nonlinear ultrasonic instrument to an oscilloscope.

[0033] A three-point bending fatigue loading test was performed on a specimen of aluminum alloy material using an MTS high-frequency fatigue loading machine, and a specimen containing fatigue microcracks at the center of the specimen was obtained, that is, A, B and C on the defective specimen represent microcracks at different positions.

[0034] Preferably, if Figure 3 As shown in the figure, multiple measuring points are set on the specimen, including:

[0035] A coordinate system with the leftmost point of the specimen as the origin is established, and the excitation direction of the excitation sensor probe on the left side of the specimen is the positive half axis of the coordinate axis. On the positive half axis of the coordinate axis, multiple equally spaced measurement points are evenly divided and marked as A 1 ,A 2 ,...,A i ,A j ,...,A n These measurement points divide the specimen into several equidistant areas, marked as D 1 ,D 2 ,...,D i ,D j ,...,D n , such as measuring point A 1 With measuring point A 2 The area between is D 1 , and so on.

[0036] In the embodiment of the present invention, a metal specimen to be tested is divided into a plurality of measuring points, and a measuring area is divided between each measuring point, so as to locate the microcracks according to the nonlinear coefficient measured at each measuring point.

[0037] Preferably, the outputting of sinusoidal signals of different frequencies respectively by a nonlinear ultrasonic instrument comprises:

[0038] A low-frequency excitation signal of 1.8 MHz and a high-frequency excitation signal of 4.6 MHz are generated by a computer and transmitted to a nonlinear ultrasonic instrument for conversion. A low-frequency sinusoidal signal and a high-frequency sinusoidal signal are output through two radio frequency output terminals of the nonlinear ultrasonic instrument; the low-frequency sinusoidal signal is adjusted for signal strength through an attenuator, and then the signal clarity is improved through a low-pass filter, and then the signal is transmitted to a first excitation sensor (for receiving low-frequency signals); the high-frequency sinusoidal signal is adjusted for signal strength through an attenuator, and then the signal attenuation and distortion are reduced through a duplexer, and then the signal is transmitted to a second excitation sensor (for receiving high-frequency signals).

[0039] In the embodiment of the present invention, the purpose of frequency mixing detection is achieved by exciting low-frequency signals and high-frequency signals, and a series of enhancement processes are performed on the signals to avoid low detection accuracy caused by signal attenuation and distortion during transmission.

[0040] Preferably, the sinusoidal signal includes a low-frequency sinusoidal signal and a high-frequency sinusoidal signal;

[0041] The method of respectively exciting sinusoidal signals of corresponding frequencies into the test piece by using excitation sensors disposed at different sides of the test piece comprises:

[0042] The low-frequency sinusoidal signal is converted into a low-frequency ultrasonic signal by a first excitation sensor deployed at one side of the specimen, and the high-frequency sinusoidal signal is converted into a high-frequency ultrasonic signal by a second excitation sensor deployed at the other side of the specimen. Delay calculation is performed on the low-frequency ultrasonic signal and the high-frequency ultrasonic signal to obtain a delay time, the low-frequency ultrasonic signal is excited into the specimen by the first excitation sensor, and the high-frequency ultrasonic signal is excited into the specimen by the second excitation sensor according to the delay time.

[0043] Before the signal conversion processing is performed on the low-frequency sinusoidal signal and the high-frequency sinusoidal signal, it also includes:

[0044] The low-frequency sinusoidal signal is modulated by using the Blackman window function through the first excitation sensor arranged at both ends of the test piece, and the high-frequency sinusoidal signal is modulated by using the Blackman window function through the second excitation sensor.

[0045] It should be understood that the signal excitation sensors symmetrically arranged on both sides of the sample to be tested adopt Blackman window modulation to window the signal with a window function, thereby changing the spectral characteristics of the signal, reducing spectral leakage and sidelobe effects, and thus improving the accuracy of frequency domain analysis.

[0046] In the embodiment of the present invention, a low frequency signal and a high frequency signal are excited into the specimen, and the high frequency signal is excited into the specimen with a delay according to a delay time, so that the low frequency signal and the high frequency signal can meet in the specimen to achieve resonance.

[0047] Preferably, the delay calculation of the low-frequency ultrasonic signal and the high-frequency ultrasonic signal to obtain the delay time includes:

[0048] The low-frequency ultrasonic signal and the high-frequency ultrasonic signal are calculated by a delay calculation expression to obtain a delay time, and the delay calculation expression is:

[0049]

[0050] Among them, T S is the delay time, is the measurement point location, is the group velocity of the low-frequency ultrasonic signal (i.e. the group velocity of the low-frequency excitation shock wave), is the group velocity of the high-frequency ultrasonic signal (i.e., the group velocity of the high-frequency excitation frequency wave), and L is the length of the specimen.

[0051] Specifically, the derivation process of the delay calculation expression is:

[0052] C g1 t n +C g2 (t n -T s )=L,

[0053]

[0054] Among them, t n It is the time when the low-frequency ultrasonic signal and the high-frequency ultrasonic signal meet in the specimen.

[0055] In an embodiment of the present invention, the delay time required to excite the high-frequency ultrasonic signal is derived based on the group velocity of the low-frequency ultrasonic signal, the group velocity of the high-frequency ultrasonic signal, the meeting time of the low-frequency ultrasonic signal and the high-frequency ultrasonic signal, the position of each measuring point and the length of the specimen. By changing the excitation time of the excitation sensor on one side of the specimen, the two columns of signals can resonate at each measuring point on the specimen.

[0056] Preferably, when different sinusoidal signals resonate at a plurality of the measuring points, echo signals of the plurality of the measuring points are obtained, including:

[0057] When the low-frequency ultrasonic signal and the high-frequency ultrasonic signal are respectively at the measuring point A of the specimen 1 ,A 2 ,...,A NWhen they meet, they resonate and generate echo signals corresponding to each measuring point, which are collected by the second excitation sensor, and then pass through the duplexer to reduce the attenuation and distortion of the signal. Then, each echo signal is subjected to noise reduction processing by the high-pass filter, and finally input from the RF input terminal of the nonlinear ultrasonic instrument and transmitted to the oscilloscope by the nonlinear ultrasonic instrument.

[0058] Preferably, the predicted amplitude includes a first fundamental wave amplitude, a second fundamental wave amplitude, a sum frequency amplitude and a difference frequency amplitude;

[0059] The performing nonlinear calculations on the plurality of predicted amplitudes respectively to obtain nonlinear coefficients corresponding to the plurality of measurement points comprises:

[0060] The first fundamental wave amplitude, the second fundamental wave amplitude and the sum frequency amplitude of any measuring point are calculated by a nonlinear calculation expression to obtain a sum frequency nonlinear coefficient. The first fundamental wave amplitude, the second fundamental wave amplitude and the difference frequency amplitude of any measuring point are calculated by a nonlinear calculation expression to obtain a difference frequency nonlinear coefficient. In this process, all measuring points are processed to obtain the sum frequency nonlinear coefficient and the difference frequency nonlinear coefficient corresponding to the multiple measuring points. The nonlinear calculation expression is:

[0061]

[0062] Among them, β 1 is the sum frequency nonlinear coefficient, β 2 is the difference frequency nonlinear coefficient, is the sum frequency amplitude, is the first fundamental amplitude, is the second fundamental amplitude, is the difference frequency amplitude.

[0063] It should be understood that the first and second harmonics 2ω can also be extracted from the predicted spectrum. 1 The amplitude The second harmonic 2ω 2 The amplitude

[0064] The processing steps of performing nonlinear calculation on the plurality of predicted simulation amplitudes are the same as the processing steps of performing nonlinear calculation on the plurality of predicted amplitudes, and will not be repeated here.

[0065] In the embodiment of the present invention, since the mixing signal can reflect the nonlinear effect of the metal specimen, and since the propagation of ultrasound in a solid medium containing microcracks will have a nonlinear effect, it is known that microcracks exist in the metal specimen. Therefore, nonlinear calculation is performed on each amplitude of the echo signal at each measuring point, and then the area where the microcracks are located is determined according to the nonlinear coefficient of each measuring point.

[0066] Preferably, determining the microcrack positions according to the plurality of nonlinear coefficients comprises:

[0067] The plurality of nonlinear coefficients are sorted in descending order, the first two nonlinear coefficients are selected from the sorting result, the measurement points corresponding to the two selected nonlinear coefficients are searched, and the area between the two measurement points is determined as the microcrack position.

[0068] It should be understood that the multiple sum frequency nonlinear coefficients or the multiple difference frequency nonlinear coefficients are sorted to determine the two measurement points A with larger nonlinear coefficients. i and A j , thus determining the area where the microcracks are located as D i .

[0069] In the embodiment of the present invention, since the larger the nonlinear coefficient, the more obvious the defect, the two largest nonlinear coefficients are selected from the nonlinear coefficients of all the measuring points to determine the area where the microcracks are located based on the two measuring points.

[0070] The predicted microcrack positions are verified through COMSO simulation to ensure the accuracy of microcrack positioning of the tested specimens.

[0071] Preferably, the step of importing a simulation specimen model having the same size as the specimen and setting a plurality of simulation measurement points includes:

[0072] The solidwork modeling tool was used to construct a cuboid with a length of 100 mm, a width of 30 mm, and a height of 30 mm as a simulation specimen model, and then a defect with a length of 30 mm and a width of 2 mm was cut out in the middle to simulate a crack.

[0073] It should be understood that the size of the simulated specimen model is consistent with the size of the tested specimen, and multiple simulated measurement points with the same number and position as the specimen are set on the simulated specimen model. The simulated specimen model is divided into the same measurement points as the metal specimen, so that the detection results of the metal specimen can be verified one by one to ensure the accuracy of the positioning results.

[0074] Preferably, the performing displacement processing on the plurality of simulation measurement points of the simulation specimen model comprises:

[0075] The plurality of simulation measurement points of the simulation specimen model are subjected to displacement processing according to the high-frequency simulation excitation signal, and the plurality of simulation measurement points of the simulation specimen model are subjected to displacement processing according to the low-frequency simulation excitation signal through a displacement function, wherein the displacement function is:

[0076] -exp(-(2tf 1 -2) 2 )*sin(2pif 1t),

[0077] Among them, -exp(-(2tf 1 -2) 2 ) is a Gaussian attenuation function, sin(2pif 1 t) is the periodic frequency of change f 1 The sine wave, t is the displacement application time, f 1 is the frequency of the low-frequency simulation excitation signal.

[0078] Preferably, performing displacement processing on the plurality of simulation measurement points of the simulation specimen model according to the high-frequency simulation excitation signal comprises:

[0079] The multiple simulation measurement points of the simulation specimen model are subjected to displacement processing according to the high-frequency simulation excitation signal through a delay displacement function, wherein the delay displacement function is:

[0080] -exp(-(2(tT′ S )f 2 -2))*sin(2pif 2 (tT′ S )),

[0081] Among them, -exp(-(2(tT′ S )f 2 -2)) is a Gaussian attenuation function, sin(2pif 2 (tT′ S )) is the frequency of periodic change f 2 The sine wave, t is the displacement application time, f 2 is the frequency of the high-frequency simulation excitation signal, T′ s is the simulation delay time.

[0082] Specifically, according to the set low-frequency displacement frequency (i.e., the frequency of the low-frequency simulation excitation signal) and the set high-frequency displacement frequency (i.e., the frequency of the high-frequency simulation excitation signal), the displacement field is applied to the simulation specimen model, so that multiple simulation measurement points of the simulation specimen model move according to the frequency of the simulation excitation signal, and the low-frequency simulation excitation signal and the high-frequency simulation excitation signal excited on both sides of the simulation specimen model meet in the simulation specimen model to generate resonance. The function expression of applying the displacement field on both sides of the simulation specimen model is:

[0083] -exp(-(2tf 1 -2) 2 )*sin(2pif 1 t), (t≤5 / f 1 )

[0084] -exp(-(2tf2 -2) 2 )*sin(2pif 2 t), (t≤5 / f 2 )

[0085] Among them, -exp(-(2tf 1 -2) 2 ) is a Gaussian attenuation function. As time t increases, the function decreases exponentially. (2tf 2 -2) Control the center position of the Gaussian curve when t = 1 / f 1 When , this item is the maximum value, sin(2pif 1 t) is sin(2πf 1 t) is the periodic frequency of change f 1 The sine wave, sin(2pif 2 t) is the periodic frequency of change f 2 The sine wave, t is the displacement application time, f 1 is the frequency of the low-frequency simulation excitation signal, f 2 is the frequency of the high-frequency simulation excitation signal;

[0086] In order to simulate the resonance of the low-frequency simulation excitation signal and the high-frequency simulation excitation signal at the multiple simulation measurement points of the simulation specimen model, it is necessary to delay the displacement application time of the high-frequency simulation excitation signal. In the simulation process, the delay of the displacement field excitation signal on the right side of the specimen is realized by changing the function (equivalent to the high-frequency ultrasonic signal being excited into the specimen by the second excitation sensor according to the delay time in the actual detection), so that the two columns of signals are respectively at the simulation measurement point A of the simulation specimen model. 1 ,A 2 ,...,A N The function expression of the displacement field imposed by the high-frequency simulation excitation signal with added delay time on one side of the simulation specimen model is:

[0087] -exp(-(2(tT′ s )f 2 -2))*sin(2pif 2 (tT′ s )),

[0088] Among them, -exp(-(2(tT′ s )f 2 -2)) is a Gaussian attenuation function, sin(2pif 2 (tT′ s )) is the frequency of periodic change f 2 The sine wave, t is the displacement application time, f 2is the frequency of the high-frequency simulation excitation signal, T′ s is the simulation delay time.

[0089] It should be understood that the physical field interface is selected as the solid mechanics interface to apply the physical field to the simulation specimen model. Since the ultrasonic wave emitted during the positioning detection of the specimen is a high-frequency sound wave, its propagation can be regarded as the periodic vibration of particles in the medium under the action of elastic force, and this vibration can be accurately described by the displacement field. Therefore, the displacement field is applied to the center positions on both sides of the constructed simulation specimen model to simulate the propagation of the ultrasonic wave excited by the excitation sensor in the material and the resulting material displacement.

[0090] In the embodiment of the present invention, the simulation specimen model is subjected to displacement processing according to a set frequency to simulate the process of exciting ultrasonic signals on both sides of the specimen in the detection and identification of a real specimen so that the ultrasonic signals on both sides resonate in the specimen.

[0091] Preferably, receiving the displacement relationship images corresponding to the plurality of simulation measurement points by a receiving probe comprises:

[0092] In advance, at the simulation measurement point A 1 ,A 2 ,...,A N A receiving probe is added to receive the resonance signal. A free tetrahedral mesh is used to mesh the constructed simulation specimen model. The output time step of the transient solver is set to range(0,0.01,30)μs, that is, the output time step is 0.01μs, and the output is stopped when it is close to or near 30μs.

[0093] After the displacement processing is performed on the plurality of simulation measurement points of the simulation specimen model, the received signal is each simulation measurement point A 1 ,A 2 ,...,A N An image of the relationship between displacement and time at the receiving probe (i.e., displacement relationship image) is obtained.

[0094] In the embodiment of the present invention, a receiving probe is added to simulate the receiving process of the echo signal by the high-frequency excitation sensor, so as to simulate a simulation spectrum diagram according to each displacement relationship image.

[0095] Preferably, comparing the plurality of nonlinear coefficients with the plurality of simulation nonlinear coefficients comprises:

[0096] The plurality of nonlinear coefficients and the plurality of simulation nonlinear coefficients are processed respectively by the plot function to obtain a nonlinear coefficient curve graph and a simulation nonlinear coefficient curve graph, and the nonlinear coefficient curve graph and the simulation nonlinear coefficient curve graph are compared to obtain a comparison result.

[0097] It should be understood that the two sets of data are processed using the plot function, and the nonlinear coefficient curve graphs of each measurement point of the specimen detection and the simulation specimen model detection are drawn, and the two graphs are visually compared. It is found that the curve graph drawn by the test specimen data and the curve graph drawn by the simulation data have a high degree of overlap, which verifies the accuracy of the generated specimen microcrack detection results.

[0098] In the embodiment of the present invention, by visually comparing the nonlinear coefficient of the detection result with the nonlinear coefficient of the simulation result, it is possible to intuitively compare whether the nonlinear coefficient curves are consistent and determine whether the detection result is accurate.

[0099] like Figure 4 As shown, a micro-crack location system of a nonlinear ultrasonic mixing signal provided by an embodiment of the present invention includes:

[0100] A prediction module is used to divide a plurality of measurement points based on the position of the test piece, generate sinusoidal signals of different frequencies respectively by using a nonlinear ultrasonic instrument, excite sinusoidal signals of corresponding frequencies into the test piece respectively by using excitation sensors disposed at different side ends of the test piece, receive echo signals of different sinusoidal signals at a plurality of the measurement points by using a designated excitation sensor, perform Fourier transform processing on the plurality of the echo signals to obtain a prediction spectrum diagram, extract prediction amplitudes corresponding to the plurality of the measurement points from the prediction spectrum diagram, perform nonlinear calculation on the plurality of the prediction amplitudes respectively, and obtain nonlinear coefficients corresponding to the plurality of the measurement points;

[0101] A simulation module, used for importing a simulation specimen model, dividing a plurality of simulation measurement points based on the position of the simulation specimen model, performing displacement processing on the plurality of simulation measurement points of the simulation specimen model to obtain displacement relationship images corresponding to the plurality of simulation measurement points, performing Fourier transform processing on the plurality of displacement relationship images to obtain a simulation spectrum diagram, extracting predicted simulation amplitudes corresponding to the plurality of simulation measurement points from the simulation spectrum diagram, performing nonlinear calculations on the plurality of predicted simulation amplitudes respectively, and obtaining a plurality of simulation nonlinear coefficients corresponding to the plurality of simulation measurement points;

[0102] The verification module is used to compare the multiple nonlinear coefficients with the multiple simulation nonlinear coefficients, and when the comparison results are consistent, determine the microcrack positions according to the multiple nonlinear coefficients.

[0103] It should be noted that, in this article, relational terms such as first and second, etc. are only used 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. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0104] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems and modules described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0105] In the several embodiments provided in this application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are only schematic, for example, the division of modules is only a logical function division, and there may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0106] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the embodiments of the present invention.

[0107] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A microcrack location method using a nonlinear ultrasonic mixing signal, characterized in that: The steps include: Divide a plurality of measuring points based on the position of the test piece, use a nonlinear ultrasonic instrument to generate sinusoidal signals of different frequencies, respectively, excite the sinusoidal signals of corresponding frequencies into the test piece through excitation sensors deployed at different sides of the test piece, and receive echo signals of different sinusoidal signals at the plurality of measuring points through designated excitation sensors; Performing Fourier transform processing on the plurality of echo signals to obtain a predicted spectrum diagram, extracting predicted amplitudes corresponding to the plurality of measurement points from the predicted spectrum diagram, and performing nonlinear calculation on the plurality of predicted amplitudes respectively to obtain nonlinear coefficients corresponding to the plurality of measurement points; Importing a simulation specimen model, dividing a plurality of simulation measurement points based on the position of the simulation specimen model, performing displacement processing on the plurality of simulation measurement points of the simulation specimen model, and obtaining displacement relationship images corresponding to the plurality of simulation measurement points; Performing Fourier transform processing on the plurality of displacement relationship images to obtain a simulation spectrum diagram, extracting predicted simulation amplitudes corresponding to the plurality of simulation measurement points from the simulation spectrum diagram, and performing nonlinear calculation on the plurality of predicted simulation amplitudes to obtain a plurality of simulation nonlinear coefficients corresponding to the plurality of simulation measurement points; The plurality of nonlinear coefficients are compared with the plurality of simulation nonlinear coefficients, and when the comparison results are consistent, the microcrack positions are determined according to the plurality of nonlinear coefficients.

2. The microcrack locating method according to claim 1, characterized in that: The sinusoidal signal includes a low-frequency sinusoidal signal and a high-frequency sinusoidal signal; The method of respectively exciting sinusoidal signals of corresponding frequencies into the test piece by using excitation sensors disposed at different sides of the test piece comprises: The low-frequency sinusoidal signal is converted into a low-frequency ultrasonic signal by a first excitation sensor deployed at one side of the specimen, and the high-frequency sinusoidal signal is converted into a high-frequency ultrasonic signal by a second excitation sensor deployed at the other side of the specimen. Delay calculation is performed on the low-frequency ultrasonic signal and the high-frequency ultrasonic signal to obtain a delay time, the low-frequency ultrasonic signal is excited into the specimen by the first excitation sensor, and the high-frequency ultrasonic signal is excited into the specimen by the second excitation sensor according to the delay time.

3. The microcrack locating method according to claim 2, characterized in that: The delay calculation of the low-frequency ultrasonic signal and the high-frequency ultrasonic signal to obtain the delay time includes: The low-frequency ultrasonic signal and the high-frequency ultrasonic signal are calculated by a delay calculation expression to obtain a delay time, and the delay calculation expression is: Among them, T S is the delay time, is the measurement point location, is the group velocity of the low-frequency ultrasonic signal, C g2 is the group velocity of the high-frequency ultrasonic signal, and L is the length of the specimen.

4. The microcrack locating method according to claim 1, characterized in that: The predicted amplitude includes a first fundamental wave amplitude, a second fundamental wave amplitude, a sum frequency amplitude and a difference frequency amplitude; The performing nonlinear calculations on the plurality of predicted amplitudes respectively to obtain nonlinear coefficients corresponding to the plurality of measurement points comprises: The first fundamental wave amplitude, the second fundamental wave amplitude and the sum frequency amplitude of any measuring point are calculated by a nonlinear calculation expression to obtain a sum frequency nonlinear coefficient. The first fundamental wave amplitude, the second fundamental wave amplitude and the difference frequency amplitude of any measuring point are calculated by a nonlinear calculation expression to obtain a difference frequency nonlinear coefficient. In this process, all measuring points are processed to obtain the sum frequency nonlinear coefficient and the difference frequency nonlinear coefficient corresponding to the multiple measuring points. The nonlinear calculation expression is: Among them, β1 is the sum frequency nonlinear coefficient, β2 is the difference frequency nonlinear coefficient, is the sum frequency amplitude, is the first fundamental amplitude, is the second fundamental amplitude, is the difference frequency amplitude.

5. The microcrack locating method according to claim 1, characterized in that: Determining the microcrack positions according to the plurality of nonlinear coefficients comprises: The plurality of nonlinear coefficients are sorted in descending order, the first two nonlinear coefficients are selected from the sorting result, the measurement points corresponding to the two selected nonlinear coefficients are searched, and the area between the two measurement points is determined as the microcrack position.

6. The microcrack locating method according to claim 1, characterized in that: The performing displacement processing on the plurality of simulation measurement points of the simulation specimen model comprises: The plurality of simulation measurement points of the simulation specimen model are subjected to displacement processing according to the high-frequency simulation excitation signal, and the plurality of simulation measurement points of the simulation specimen model are subjected to displacement processing according to the low-frequency simulation excitation signal through a displacement function, wherein the displacement function is: -exp(-(2tf1-2) 2 )*sin(2pif1t), Among them, -exp(-(2tf1-2) 2 ) is a Gaussian attenuation function, sin(2pif1t) is a periodically changing sine wave with a frequency of f1, t is the displacement application time, and f1 is the frequency of the low-frequency simulation excitation signal.

7. The microcrack locating method according to claim 6, characterized in that: The performing displacement processing on the plurality of simulation measurement points of the simulation specimen model according to the high-frequency simulation excitation signal comprises: The multiple simulation measurement points of the simulation specimen model are subjected to displacement processing according to the high-frequency simulation excitation signal through a delay displacement function, wherein the delay displacement function is: -exp(-(2(t-T s ′)f2-2))*sin(2pif2(t-T S ′)), Among them, -exp(-(2(tT S ′)f2-2)) is a Gaussian attenuation function, sin(2pif2(tT S ′)) is a sine wave with a periodic frequency of f2, t is the displacement application time, f2 is the frequency of the high-frequency simulation excitation signal, T S ' is the simulation delay time.

8. The microcrack locating method according to claim 1, characterized in that: The comparing the plurality of nonlinear coefficients with the plurality of simulation nonlinear coefficients comprises: The plurality of nonlinear coefficients and the plurality of simulation nonlinear coefficients are processed respectively by the plot function to obtain a nonlinear coefficient curve graph and a simulation nonlinear coefficient curve graph, and the nonlinear coefficient curve graph and the simulation nonlinear coefficient curve graph are compared to obtain a comparison result.

9. A microcrack location system of nonlinear ultrasonic mixing signal, characterized in that: include: A prediction module is used to divide a plurality of measurement points based on the position of the test piece, generate sinusoidal signals of different frequencies respectively by using a nonlinear ultrasonic instrument, excite sinusoidal signals of corresponding frequencies into the test piece respectively by using excitation sensors disposed at different side ends of the test piece, receive echo signals of different sinusoidal signals at a plurality of the measurement points by using a designated excitation sensor, perform Fourier transform processing on the plurality of the echo signals to obtain a prediction spectrum diagram, extract prediction amplitudes corresponding to the plurality of the measurement points from the prediction spectrum diagram, perform nonlinear calculation on the plurality of the prediction amplitudes respectively, and obtain nonlinear coefficients corresponding to the plurality of the measurement points; A simulation module, used for importing a simulation specimen model, dividing a plurality of simulation measurement points based on the position of the simulation specimen model, performing displacement processing on the plurality of simulation measurement points of the simulation specimen model to obtain displacement relationship images corresponding to the plurality of simulation measurement points, performing Fourier transform processing on the plurality of displacement relationship images to obtain a simulation spectrum diagram, extracting predicted simulation amplitudes corresponding to the plurality of simulation measurement points from the simulation spectrum diagram, performing nonlinear calculations on the plurality of predicted simulation amplitudes respectively, and obtaining a plurality of simulation nonlinear coefficients corresponding to the plurality of simulation measurement points; The verification module is used to compare the multiple nonlinear coefficients with the multiple simulation nonlinear coefficients, and when the comparison results are consistent, determine the microcrack positions according to the multiple nonlinear coefficients.

10. The micro-crack locating system according to claim 9, characterized in that: The sinusoidal signal includes a low-frequency sinusoidal signal and a high-frequency sinusoidal signal; In the prediction module, sinusoidal signals of corresponding frequencies are excited into the specimen respectively by excitation sensors disposed at different sides of the specimen, including: The low-frequency sinusoidal signal is converted into a low-frequency ultrasonic signal by a first excitation sensor deployed at one side of the specimen, and the high-frequency sinusoidal signal is converted into a high-frequency ultrasonic signal by a second excitation sensor deployed at the other side of the specimen. Delay calculation is performed on the low-frequency ultrasonic signal and the high-frequency ultrasonic signal to obtain a delay time, the low-frequency ultrasonic signal is excited into the specimen by the first excitation sensor, and the high-frequency ultrasonic signal is excited into the specimen by the second excitation sensor according to the delay time.

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