Defect imaging method based on nonlinear ultrasonic mixing and high harmonic phased array

Abstract

This invention provides a defect imaging method based on nonlinear ultrasonic mixing and high-harmonic phased arrays, belonging to the field of ultrasonic nondestructive testing technology. The method includes: exciting shear wave and longitudinal wave signals through each element of an ultrasonic phased array; receiving nonlinear signals through each element to form full matrix data; obtaining first matrix data corresponding to the difference-frequency shear wave signal, second matrix data corresponding to the sum-frequency shear wave signal, and third matrix data corresponding to the high-harmonic signals of the longitudinal wave through variational mode decomposition; further obtaining first defect imaging data corresponding to the difference-frequency shear wave signal, second defect imaging data corresponding to the sum-frequency shear wave signal, and third defect imaging data corresponding to the high-harmonic signals of the longitudinal wave; and obtaining defect detection results based on the first, second, and third defect imaging data. By arranging and combining imaging results of different nonlinear signals, various minute defects in materials can be accurately detected.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic nondestructive testing technology, and more specifically, relates to a defect imaging method based on nonlinear ultrasonic mixing and high-order harmonic phased array. Background Technology

[0002] In the field of nondestructive testing (NDT), ultrasonic testing is widely used. However, most existing ultrasonic testing methods are based on the principle of linear ultrasound. This principle states that when ultrasonic waves encounter volumetric defects with significant acoustic impedance and a length greater than or equal to their wavelength, they exhibit linear characteristics such as reflection, absorption, and scattering of ultrasonic energy. Linear ultrasonic NDT technology relies on this principle to detect and evaluate defects, making it difficult to detect defects smaller than the wavelength. Nonlinear ultrasonic testing, on the other hand, originates from the nonlinear effects induced by the interaction between ultrasonic waves and defects such as microcracks and material nonlinearities (e.g., lattice distortion). This generates phenomena such as higher harmonics, subharmonics, acoustic resonance frequency drift, and mixing harmonics. These nonlinear phenomena are more sensitive to small defects, enabling the detection of even minute defects.

[0003] Existing research on ultrasonic phased array imaging is based on the principle of linear ultrasound, which makes it difficult to identify minute defects below the wavelength level. Meanwhile, nonlinear ultrasound research mostly relies on defined nonlinear coefficients to qualitatively evaluate defects, failing to accurately and intuitively represent defect information. How to accurately detect minute defects in materials is a pressing technical problem that the industry needs to solve. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to achieve accurate detection of minute defects in materials.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a defect imaging method based on nonlinear ultrasonic mixing and high-order harmonic phased array, comprising:

[0006] The transverse wave signal and the longitudinal wave signal are excited by each element in the ultrasonic phased array, and the transverse wave signal and the longitudinal wave signal reach the target material simultaneously.

[0007] The nonlinear signals received by each element in the ultrasonic phased array are used to form full matrix data.

[0008] Based on the full matrix data, variational mode decomposition is used to obtain the first matrix data corresponding to the difference frequency shear wave signal, the second matrix data corresponding to the sum frequency shear wave signal, and the third matrix data corresponding to the higher harmonic signals of the longitudinal wave, wherein the higher harmonic signals are second-order or higher harmonic signals.

[0009] Based on the first matrix data, the second matrix data and the third matrix data, the first defect imaging data corresponding to the difference frequency shear wave signal, the second defect imaging data corresponding to the sum frequency shear wave signal and the third defect imaging data corresponding to the higher harmonic signal of the longitudinal wave are obtained.

[0010] Based on the first defect imaging data, the second defect imaging data, and the third defect imaging data, the defect detection results of the target material are obtained.

[0011] Optionally, the step of obtaining first defect imaging data corresponding to the difference-frequency shear wave signal, second defect imaging data corresponding to the sum-frequency shear wave signal, and third defect imaging data corresponding to the higher harmonic signals of the longitudinal wave based on the first matrix data, the second matrix data, and the third matrix data includes:

[0012] Perform the following operations on any one of the target signals: the difference frequency shear wave signal, the sum frequency shear wave signal, and the higher harmonic signal of the longitudinal wave:

[0013] Based on the matrix data corresponding to the target signal, the amplitude corresponding to each pixel in the imaging area is obtained through a full-focus imaging algorithm;

[0014] Based on the amplitude value corresponding to each pixel in the imaging region, obtain the complex domain signal corresponding to each pixel in the imaging region;

[0015] Based on the complex domain signal corresponding to each pixel in the imaging region, the defect imaging data corresponding to the target signal is obtained through filtering.

[0016] Optionally, obtaining the complex domain signal corresponding to each pixel in the imaging region based on the amplitude value of each pixel in the imaging region includes obtaining the complex domain signal corresponding to the pixel using the following formula:

[0017] I2 = Hilbert(I(x,y));

[0018] Where I(x,y) represents the magnitude of the pixel, Hilbert(·) represents the Hilbert transform, and I2 represents the complex domain signal of the pixel.

[0019] Optionally, the step of obtaining defect imaging data corresponding to the target signal by filtering the complex domain signal corresponding to each pixel in the imaging region includes filtering using the following formula:

[0020]

[0021] Where I2 represents the complex domain signal corresponding to the pixel, |I2|max I2 represents the maximum absolute value, and I3 represents the defect imaging value corresponding to the pixel after filtering.

[0022] Optionally, the step of receiving nonlinear signals through each element of the ultrasonic phased array to form full matrix data includes:

[0023] For each element in the ultrasonic phased array, the first signal is received by first exciting the positive phase fundamental wave of the element, and then the second signal is received by exciting the negative phase fundamental wave.

[0024] Based on the first signal and the second signal received by each array element, the nonlinear signal received by each array element is obtained.

[0025] The full matrix data is composed based on the nonlinear signals received by each array element.

[0026] Optionally, obtaining the nonlinear signal received by each array element based on the first signal and the second signal received by each array element includes obtaining the nonlinear signal received by the array element using the following formula:

[0027]

[0028] Among them, u c The nonlinear signal received by the array element is represented by u1, which represents the first signal, and u2, which represents the second signal.

[0029] Optionally, the step of exciting transverse and longitudinal wave signals through each element of the ultrasonic phased array includes:

[0030] For any two adjacent array elements in the ultrasonic phased array, first control one array element to excite a transverse wave signal, and then control the other array element to excite a longitudinal wave signal.

[0031] The excitation time difference between the transverse wave signal and the longitudinal wave signal is determined based on a first time taken for the transverse wave signal to propagate to the target material and a second time taken for the longitudinal wave signal to propagate to the target material.

[0032] Secondly, the present invention also provides a defect imaging device based on nonlinear ultrasonic mixing and high-order harmonic phased array, comprising:

[0033] The signal excitation module is used to excite transverse wave signals and longitudinal wave signals through each element in the ultrasonic phased array, and the transverse wave signals and the longitudinal wave signals arrive at the target material simultaneously.

[0034] The full matrix data composition module is used to receive nonlinear signals through each array element in the ultrasonic phased array and compose full matrix data.

[0035] The data decomposition module is used to obtain, based on the full matrix data, the first matrix data corresponding to the difference frequency shear wave signal, the second matrix data corresponding to the sum frequency shear wave signal, and the third matrix data corresponding to the higher harmonic signal of the longitudinal wave through variational mode decomposition, wherein the higher harmonic signal is a second or higher harmonic signal.

[0036] The defect imaging data acquisition module is used to acquire, based on the first matrix data, the second matrix data and the third matrix data, the first defect imaging data corresponding to the difference frequency shear wave signal, the second defect imaging data corresponding to the sum frequency shear wave signal and the third defect imaging data corresponding to the higher harmonic signal of the longitudinal wave.

[0037] The defect detection result acquisition module is used to acquire the defect detection result of the target material based on the first defect imaging data, the second defect imaging data and the third defect imaging data.

[0038] Thirdly, the present invention provides an electronic device comprising: at least one memory for storing a program; and at least one processor for executing the program stored in the memory, wherein when the program stored in the memory is executed, the processor is configured to execute the method described in the first aspect or any possible implementation thereof.

[0039] Fourthly, the present invention provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to perform the method described in the first aspect or any possible implementation thereof.

[0040] It is understood that the beneficial effects of the second to fourth aspects mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0041] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0042] By exciting transverse and longitudinal wave signals, which simultaneously reach the target material, ultrasound can interact with defects in the material to generate nonlinear effects. When ultrasound encounters microcracks or material nonlinearities, it produces nonlinear signals. For material nonlinearity, the generation mechanism of nonlinear ultrasound stems from the distortion of the material's microstructure beyond its elastic minimum deformation state, resulting in a deviation from linearity. For microcracks, the interaction between ultrasound and the microcrack causes a "breathing" effect, thus generating nonlinear signals. Furthermore, by receiving these nonlinear signals from individual elements in an ultrasonic phased array, a full matrix of data is formed. This matrix data can be decomposed into matrix data corresponding to difference-frequency transverse wave signals, sum-frequency transverse wave signals, and higher harmonic signals of the longitudinal wave. Using this matrix data corresponding to each nonlinear signal, defect imaging data corresponding to various signals can be acquired and imaged. Combinations of different nonlinear signal imaging results can yield defect detection results for the target material. Different nonlinear signals exhibit varying degrees of sensitivity to microcracks and material nonlinearity. Different types of nonlinear signals can be used to image microcracks or material nonlinearity separately: for example, the high sensitivity of sum-frequency shear wave signals and longitudinal wave second harmonic signals can be used to identify and image microcracks; similarly, the high sensitivity of difference-frequency shear wave signals can be used to identify material nonlinearity. By arranging and combining the imaging results of different nonlinear signals, various minute defects in materials can be accurately detected. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 This is a flowchart illustrating the defect imaging method based on nonlinear ultrasonic mixing and high-order harmonic phased array provided by the present invention.

[0045] Figure 2 This is a schematic diagram of the nonlinear ultrasonic phased array detection model for microcracks and nonlinear regions of materials provided by the present invention;

[0046] Figure 3 This is one of the microcrack defect imaging results provided by the present invention;

[0047] Figure 4 This is the second image of the microcrack defect imaging results provided by the present invention;

[0048] Figure 5 This is the third image of the microcrack defect imaging results provided by the present invention;

[0049] Figure 6 This is one of the material nonlinear region imaging results provided by the present invention;

[0050] Figure 7 This is the second image of the nonlinear region imaging results of materials provided by the present invention;

[0051] Figure 8 This is the third image of the nonlinear region imaging results of materials provided by this invention;

[0052] Figure 9 This is the frequency domain diagram of the detection material when it is nonlinear, provided by the present invention;

[0053] Figure 10 This is one of the imaging results provided by the present invention when microcracks and material nonlinearity coexist;

[0054] Figure 11 This is the second image of the imaging results provided by the present invention when microcracks and material nonlinearity coexist.

[0055] Figure 12 This is the third image of the imaging results provided by the present invention when microcracks and material nonlinearity coexist.

[0056] Figure 13 This is one of the imaging results provided by the present invention when microcracks coexist with strong material nonlinearity;

[0057] Figure 14 This is the second image of the imaging results provided by the present invention when microcracks and strong material nonlinearity coexist.

[0058] Figure 15 This is the third image of the imaging results provided by this invention when microcracks and strong material nonlinearity coexist.

[0059] Figure 16 This is a schematic diagram of the defect imaging device based on nonlinear ultrasonic mixing and high-order harmonic phased array provided by the present invention. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0061] The terms "first" and "second," etc., used in the specification and claims herein are used to distinguish different objects, not to describe a specific order of objects. For example, "first matrix data" and "second matrix data," etc., are used to distinguish different matrix data, not to describe a specific order of matrix data.

[0062] In embodiments of the present invention, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" or "for example" in embodiments of the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0063] In the description of the embodiments of the present invention, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0064] Next, the technical solutions provided in the embodiments of the present invention will be introduced.

[0065] Figure 1 This is a flowchart illustrating the defect imaging method based on nonlinear ultrasonic mixing and high-harmonic phased array provided by the present invention, as shown below. Figure 1 As shown, the subject executing this defect imaging method can be an electronic device, such as a server. The method includes steps S10, S20, S30, S40, and S50.

[0066] In step S10, transverse and longitudinal wave signals are excited by each element in the ultrasonic phased array, and the transverse and longitudinal wave signals arrive at the target material simultaneously.

[0067] It is understandable that ultrasound (the aforementioned excitation transverse and longitudinal wave signals) interacts with defects to produce nonlinear effects. When ultrasound encounters microcracks or material nonlinearity, it generates nonlinear signals. For material nonlinearity, the generation mechanism of nonlinear ultrasound originates from the distortion of the material microstructure that deviates from the linear state when the material is in a state of small elastic deformation. For microcracks, the interaction between ultrasound and microcracks causes the microcracks to have a breathing effect, thereby generating nonlinear signals.

[0068] Step S20: Nonlinear signals are received by each element in the ultrasonic phased array to form full matrix data.

[0069] Step S30: Based on the full matrix data, the first matrix data corresponding to the difference frequency shear wave signal, the second matrix data corresponding to the sum frequency shear wave signal, and the third matrix data corresponding to the higher harmonic signals of the longitudinal wave are obtained through variational mode decomposition. The higher harmonic signals are second-order or higher harmonic signals.

[0070] Specifically, variational mode decomposition (VMD) can be performed on each data point in the full matrix data to extract different intrinsic mode functions (IMFs). Useful components can be extracted from these IMFs to obtain the difference frequency shear wave signal, the sum frequency shear wave signal, and the second harmonic signal of the longitudinal wave, and the corresponding matrix data, such as the first matrix data corresponding to the difference frequency shear wave signal, the second matrix data corresponding to the sum frequency shear wave signal, and the third matrix data corresponding to the higher harmonic signal of the longitudinal wave.

[0071] It is understandable that, as mentioned above, the detection principle mainly stems from the nonlinear signal generated by the interaction between ultrasound and the defect. According to different frequencies, nonlinear signals can be divided into: (1) second harmonics, third harmonics, and other higher harmonics; (2) mixing harmonics, of which mixing can be divided into difference frequency and sum frequency;

[0072] The frequency of the second harmonic is twice the fundamental frequency of the excitation. When two excitation signals are applied, a mixed signal is generated. The frequency of the difference frequency signal is the difference between the frequencies of the two signals, and the frequency of the sum frequency signal is the sum of the frequencies of the two excitation signals.

[0073] Whether the mixed signal is a transverse wave or a longitudinal wave depends on the mixing conditions. This invention uses a collinear and in-direction mixing method, so the resulting mixed signal is a transverse wave.

[0074] Step S40: Based on the first matrix data, the second matrix data, and the third matrix data, acquire the first defect imaging data corresponding to the difference frequency shear wave signal, the second defect imaging data corresponding to the sum frequency shear wave signal, and the third defect imaging data corresponding to the higher harmonic signals of the longitudinal wave.

[0075] Step S50: Based on the first defect imaging data, the second defect imaging data, and the third defect imaging data, obtain the defect detection results of the target material.

[0076] It is understandable that by exciting transverse and longitudinal wave signals, which simultaneously reach the target material, the ultrasonic waves can interact with the defects in the target material to produce nonlinear effects, thereby generating nonlinear signals. These nonlinear signals are then received by each element in the ultrasonic phased array, forming a complete matrix data set. This matrix data can be decomposed into matrix data corresponding to the difference-frequency transverse wave signal, the sum-frequency transverse wave signal, and the higher harmonic signals of the longitudinal wave. Furthermore, using the matrix data corresponding to each nonlinear signal, defect imaging data corresponding to various signals can be obtained and imaged. Combinations of imaging results from different nonlinear signals can yield defect detection results for the target material. Different nonlinear signals exhibit varying sensitivities to microcracks and material nonlinearities. Different types of nonlinear signals can be used to image microcracks or material nonlinearities: for example, the high sensitivity of sum-frequency transverse wave signals and second harmonic signals of longitudinal waves can be used for microcrack identification and imaging; similarly, the high sensitivity of difference-frequency transverse wave signals can be used to identify material nonlinearities. By combining imaging results from different nonlinear signals, various minute defects in materials can be accurately detected.

[0077] The defect imaging method based on nonlinear ultrasonic mixing and high-order harmonic phased array provided by this invention has a high sensitivity to the microstructural features of materials with spatial dimensions much smaller than the wavelength of ultrasonic waves. It has special advantages in the evaluation and detection of material nonlinearity and micro-damage (such as microcracks) inside the material. At the same time, by using multiple types of nonlinear signals for imaging, it can realize the imaging of microcracks and material nonlinearity, further enriching the types of defects that can be detected.

[0078] Optionally, step S10 specifically includes: for any two adjacent array elements in the ultrasonic phased array, first control one array element to excite a shear wave signal, and then control the other array element to excite a longitudinal wave signal.

[0079] The excitation time difference between the transverse wave signal and the longitudinal wave signal is determined based on the first time taken for the transverse wave signal to propagate to the target material and the second time taken for the longitudinal wave signal to propagate to the target material.

[0080] Understandably, in order to achieve simultaneous arrival of transverse and longitudinal waves at the defect, the transmission element timing can be controlled. The transverse wave is excited first, and the delay time is calculated based on the time required for the transverse wave to reach the defect and the wave velocity. The longitudinal wave is then emitted after a corresponding delay, ultimately causing the wavefronts of both waves to arrive at the defect simultaneously.

[0081] Optionally, step S20 specifically includes: step S201, step S202 and step S203.

[0082] Step S201: For each element in the ultrasonic phased array, the positive phase fundamental wave is first excited by the element to receive the first signal, and then the negative phase fundamental wave is excited to receive the second signal.

[0083] Step S202: Based on the first and second signals received by each array element, obtain the nonlinear signal received by each array element.

[0084] Specifically, the nonlinear signal received by the array element can be obtained using the following formula:

[0085]

[0086] Among them, u c The nonlinear signals received by the array element are represented by u1, u2, and u1 represents the first signal.

[0087] Specifically, the positive-phase fundamental wave is first excited to receive signal u1, then the anti-phase fundamental wave is excited to receive signal u2, and the two are added together and divided by two to obtain the signal u that retains only the nonlinear component. c The data received by each array element are then combined to form the full matrix data.

[0088] Step S203: Based on the nonlinear signals received by each array element, form the full matrix data.

[0089] Optionally, step S40 specifically includes performing the following steps S401, S402, and S403 on any one of the target signals among the difference frequency shear wave signal, the sum frequency shear wave signal, and the higher harmonic signal of the longitudinal wave.

[0090] Step S401: Based on the matrix data corresponding to the target signal, the amplitude corresponding to each pixel in the imaging area is obtained through a full-focus imaging algorithm.

[0091] When the target signal is a difference frequency shear wave signal, the matrix data corresponding to the target signal is specifically the first matrix data mentioned above; when the target signal is a sum frequency shear wave signal, the matrix data corresponding to the target signal is specifically the second matrix data mentioned above; when the target signal is a high-order harmonic signal of a longitudinal wave, the matrix data corresponding to the target signal is specifically the third matrix data mentioned above.

[0092] Specifically, the imaging area can be divided into several grids, and the sum of the amplitudes of all array elements is the amplitude of each pixel. The calculation formula is as follows:

[0093]

[0094] Where I(x,y) represents the final magnitude at pixel position (x,y), and S ij For nonlinear signal data with respect to time and amplitude in a matrix grid, t ij (x,y) represents the time taken for the fundamental wave of different transceiver array elements to pass through a certain pixel (x,y), and its corresponding calculation formula is:

[0095]

[0096] Since the transverse wave is excited first, and the two wavefronts arrive at the defect simultaneously, the time for the excitation signal to reach the defect can be calculated using the defect distance and the transverse wave velocity. Therefore, c1 is the transverse wave velocity in the fundamental signal, and c2 is the wave velocity of the corresponding type of nonlinear signal.

[0097] Step S402: Based on the amplitude corresponding to each pixel in the imaging region, obtain the complex domain signal corresponding to each pixel in the imaging region.

[0098] Specifically, the complex domain signal corresponding to a pixel can be obtained using the following formula:

[0099] I2 = Hilbert(I(x,y));

[0100] Where I(x,y) represents the magnitude of the pixel, Hilbert(·) represents the Hilbert transform, and I2 represents the complex domain signal of the pixel.

[0101] Understandably, by further post-processing the amplitude information of each pixel, such as using the Hilbert algorithm, the time-domain signal can be restored to the signal in the entire complex domain through the Hilbert transform, which can accurately capture instantaneous information and optimize image quality.

[0102] Step S403: Based on the complex domain signal corresponding to each pixel in the imaging area, the defect imaging data corresponding to the target signal is obtained through filtering.

[0103] When the target signal is a difference-frequency shear wave signal, the defect imaging data corresponding to the target signal is specifically the first defect imaging data mentioned above; when the target signal is a sum-frequency shear wave signal, the defect imaging data corresponding to the target signal is specifically the second defect imaging data mentioned above; when the target signal is a higher harmonic signal of a longitudinal wave, the defect imaging data corresponding to the target signal is specifically the third defect imaging data mentioned above.

[0104] Understandably, the "-6dB method" can be used to process the signal, that is, to filter out signals smaller than half of the maximum amplitude value. This can filter out most of the noise interference, retain only the defect image, and optimize the image quality.

[0105] Specifically, filtering can be performed using the following formula:

[0106]

[0107] Where I2 represents the complex domain signal corresponding to the pixel, |I2| maxI2 represents the maximum absolute value, and I3 represents the defect imaging value corresponding to the pixel after filtering.

[0108] Figure 2 This is a schematic diagram of a nonlinear ultrasonic phased array model for detecting microcracks and nonlinear regions of materials provided by the present invention. For example, refer to... Figure 2 The location of the defect and the position of the phased array elements are as follows: Figure 2 As shown, the model material is aluminum, the microcrack defect is 0.3 mm in length, and the area of ​​the nonlinear defect region is 10 mm × 10 mm. The material nonlinearity is represented by a nonlinear constitutive equation containing third-order elastic constants. To intuitively reflect the material nonlinearity, it can be simplified to a one-dimensional constitutive model: σ = (E + E²ε)ε, E² = -0.5 × (3E + 2A + 6B + 2C), where σ and ε represent stress and strain, respectively, E² is the second-order elastic modulus, and A, B, and C are used to characterize the strength of the material nonlinearity. A, B, and C are the third-order elastic constants (TOE). Below the model are 16 ultrasonic phased array elements. The phased array elements are excited by a Hanning window pulse signal u(t) = Asin(2πft) × 0.5(1 - cos(2πft / N), where the fundamental frequencies are 10-cycle 3MHz transverse waves and 4MHz longitudinal waves, respectively, and the amplitude is A = 10. -4 mm.

[0109] Reference Figure 1 The defect imaging method based on nonlinear ultrasonic mixing and high-order harmonic phased array provided by the present invention includes the following steps:

[0110] Step S10: Excite transverse and longitudinal wave signals through each element in the ultrasonic phased array.

[0111] For example, in an ultrasonic phased array, one element first excites a transverse wave, and the adjacent element excites a longitudinal wave. The signals are both sinusoidal pulse signals with a 10-period Hanning window, u(t) = Asin(2πft) × 0.5(1 - cos(2πft / N), and the amplitude is A = 10. -4 mm.

[0112] Controlling the transmission element timing, the transverse wave is excited first, and the time for the transverse wave to reach the defect is t1 (i.e., the first duration mentioned above). The time for the longitudinal wave to reach the defect is t2 (i.e., the second duration mentioned above). The delay time Δt = t1 - t2 is calculated, that is, the longitudinal wave is delayed by Δt during transmission, and finally both waves reach the defect simultaneously.

[0113] Step S20: Nonlinear signals are received by each element in the ultrasonic phased array to form full matrix data.

[0114] For example, each array element receives nonlinear signals and assembles them into full matrix data. First, a positive-phase fundamental wave is excited to obtain signal u1 (i.e., the first signal mentioned above). Setting the amplitude 'A' to '-A' is used to excite the anti-phase fundamental wave. Signal u2 (i.e., the second signal mentioned above) is received. The two signals are added together and divided by two to obtain signal u that retains only the nonlinear component. c = (u1+u2) / 2, and combine the data of each array element into a data matrix, that is, the full matrix data.

[0115] Step S30: Based on the full matrix data, obtain the first matrix data corresponding to the difference frequency shear wave signal, the second matrix data corresponding to the sum frequency shear wave signal, and the third matrix data corresponding to the higher harmonic signals of the longitudinal wave through variational mode decomposition.

[0116] For example, variational mode decomposition (VM) can be performed on the data in the full matrix to decompose different intrinsic mode functions (IMFs), specifically IMF components of different frequencies. Based on the frequency, three nonlinear signals are selected: difference-frequency shear wave signal, sum-frequency shear wave signal, and higher harmonic signals of the longitudinal wave. The corresponding IMF components are then used to reconstruct the signals to obtain the corresponding matrix data. Here, the higher harmonics can be second harmonic signals, but in this invention, the higher harmonics are not limited to second harmonics.

[0117] Step S40: Based on the first matrix data, the second matrix data, and the third matrix data, acquire the first defect imaging data corresponding to the difference frequency shear wave signal, the second defect imaging data corresponding to the sum frequency shear wave signal, and the third defect imaging data corresponding to the higher harmonic signals of the longitudinal wave.

[0118] For example, using a full-focus imaging algorithm, the imaging area is set to 60mm×80mm, and the entire area is divided into 600×800 parts according to a grid size of 0.1mm×0.1mm. The amplitude I(x,y) of each pixel is obtained by superimposing the amplitudes of all array elements.

[0119] Further post-processing of the amplitude information of each pixel, such as the Hilbert algorithm, i.e., I2 = Hilbert(I(x,y)), can restore the time-domain signal to the signal in the entire complex domain through the Hilbert transform, accurately capture instantaneous information, and optimize image quality.

[0120] Further signal processing can be achieved using the "-6dB method," which filters out signals smaller than half of the maximum amplitude. This effectively removes most noise interference, retaining only the defect image. Specifically:

[0121]

[0122] The "-6dB method" filters out all noise that satisfies I3 < -6, which can block most noise interference. In practical applications, it is not limited to "-6dB" and can be selected according to needs.

[0123] Step S50: Based on the first defect imaging data, the second defect imaging data, and the third defect imaging data, obtain the defect detection results of the target material.

[0124] For example, by arranging and combining imaging results of different nonlinear signals (difference-frequency shear wave signals, sum-frequency shear wave signals, and higher harmonic signals of longitudinal waves), and because different nonlinear signals have different sensitivities to microcracks and material nonlinearity, microcracks or material nonlinearity can be imaged separately using different types of nonlinear signals. Specifically, this includes the following three types:

[0125] (1) Only microcracks are detected. Three nonlinear components: difference frequency shear wave, sum frequency shear wave and longitudinal wave second harmonic can all be used to image microcracks. In a single detection result, the difference frequency shear wave signal has a low frequency, and the frequency affects the imaging resolution, so the lateral resolution of the difference frequency shear wave imaging is poor.

[0126] (2) Detecting only material nonlinearity: Among the three nonlinear components, the difference frequency transverse wave is the most sensitive to the detection of material nonlinearity and can accurately detect the location of the material nonlinear region.

[0127] (3) Detection of coexistence of microcracks and material nonlinearity: Since different nonlinear signals have different sensitivities to different defects, the sum-frequency transverse wave and longitudinal wave second harmonic signal intensity caused by microcracks are greater than those caused by material nonlinearity signals. Therefore, when detecting the two defects at the same time, only the location of the microcrack can be reflected; while the difference-frequency signal has similar sensitivities to the two defects, and can realize the simultaneous detection of the two defects.

[0128] Figure 3 This is one of the microcrack defect imaging results provided by the present invention. Figure 4 This is the second image of the microcrack defect imaging results provided by the present invention. Figure 5 This is the third image of the microcrack defect imaging results provided by the present invention, for reference. Figure 3-5 This is an imaging result image of microcrack defects provided by the present invention. Figure 3-5 The images obtained from the difference frequency shear wave signal, the sum frequency shear wave signal, and the second harmonic signal of the longitudinal wave are shown respectively. The x and y coordinates represent the position coordinates of the imaging area. It can be seen that the three nonlinear components can achieve accurate imaging of the microcrack location. However, due to the influence of the ultrasonic signal frequency, the imaging resolution varies greatly. The difference frequency shear wave signal has the lowest frequency and the worst lateral resolution.

[0129] Figure 6 This is one of the imaging results of the nonlinear region of materials provided by the present invention. Figure 7 This is the second image of the nonlinear region imaging results of materials provided by this invention. Figure 8 This is the third image of the nonlinear region imaging results of materials provided by this invention, for reference. Figure 6-8 This is an imaging result diagram of material nonlinearity provided by the present invention. Figure 6-8 Imaging images obtained from difference frequency shear wave signal, sum frequency shear wave signal, and longitudinal wave second harmonic signal are shown respectively. The difference frequency shear wave signal imaging can accurately reflect the defect location, while the sum frequency shear wave signal and longitudinal wave second harmonic signal imaging results both show two imaging regions, which cannot accurately reflect the location of the nonlinear region of the material.

[0130] Figure 9 This is the frequency domain diagram of the detection material when it is nonlinear, provided by the present invention. (Refer to...) Figure 9 The frequency domain diagram of the nonlinear signal caused by material nonlinearity shows that the difference frequency shear wave signal is very obvious, while the sum frequency shear wave signal and the second harmonic signal of the longitudinal wave are relatively weak. Therefore, combined with... Figure 9 For example, the nonlinear region of a material is very sensitive to difference frequency signals.

[0131] Figure 10 This is one of the imaging results provided by the present invention when microcracks and material nonlinearity coexist. Figure 11 This is the second image of the imaging results provided by this invention when microcracks and material nonlinearity coexist. Figure 12 This is the third image of the imaging results provided by this invention when microcracks and material nonlinearity coexist. (Refer to...) Figure 10-12 This is an imaging result diagram of the coexistence of nonlinear material defects and microcrack defects provided by the present invention. Figure 10-12 The images obtained from the difference frequency shear wave signal, the sum frequency shear wave signal, and the second harmonic signal of the longitudinal wave are shown respectively. The difference frequency shear wave signal imaging can simultaneously image both microcracks and material nonlinearity, while the sum frequency shear wave signal and the second harmonic signal of the longitudinal wave can only image microcracks. This indicates that the intensity of the difference frequency shear wave signal caused by microcracks and material nonlinearity is not much different, while the sum frequency shear wave signal and the second harmonic signal of the longitudinal wave caused by microcracks are both greater than those caused by material nonlinearity.

[0132] Figure 13 This is one of the imaging results provided by the present invention when microcracks coexist with strong material nonlinearity. Figure 14 This is the second image of the imaging results provided by this invention when microcracks and strong material nonlinearity coexist. Figure 15 This is the third image provided by the present invention showing the imaging results when microcracks and strong material nonlinearity coexist. (Reference) Figure 13-15 The image shows the imaging results of strong material nonlinear defects and microcracks provided by this invention. Figure 13-15These are imaging images obtained from the difference-frequency shear wave signal, the longitudinal wave second harmonic signal, and the combined difference-frequency shear wave signal and longitudinal wave second harmonic signal, respectively. In the constitutive equation of material nonlinearity, A, B, and C in the above constitutive equation represent relatively weak material nonlinearity. However, the strength of nonlinearity in actual materials varies. If A, B, and C are magnified by a certain factor (usually tens of times) to obtain A1, B1, and C1, the nonlinearity of the material is enhanced. And from... Figure 10-12 The imaging results show that the difference frequency signals caused by A, B, and C are similar in intensity to those caused by microcracks. However, after amplifying A, B, and C to A1, B1, and C1, the difference frequency shear wave signal caused by material nonlinearity is stronger than that caused by microcracks. Therefore, during imaging, the difference frequency signal can only image material nonlinear defects, missing microcrack images. Furthermore, the sum-frequency shear wave signal and second harmonic signal induced by microcracks are much stronger than those caused by material nonlinearity. Therefore, during imaging, only microcrack images can be captured. Combining these two images, as shown... Figure 15 In this process, imaging results that simultaneously detect material nonlinearity and microcracks can be obtained, avoiding missed defects.

[0133] The defect imaging device based on nonlinear ultrasonic mixing and high-harmonic phased array provided by the present invention will be described below. The defect imaging device based on nonlinear ultrasonic mixing and high-harmonic phased array described below can be referred to in correspondence with the defect imaging method based on nonlinear ultrasonic mixing and high-harmonic phased array described above.

[0134] Figure 16 This is a schematic diagram of the defect imaging device based on nonlinear ultrasonic mixing and high-order harmonic phased array provided by the present invention, as shown below. Figure 16 As shown, the device includes: a signal excitation module 10, a full matrix data composition module 20, a data decomposition module 30, a defect imaging data acquisition module 40, and a defect detection result acquisition module 50. Wherein:

[0135] The signal excitation module 10 is used to excite transverse wave signals and longitudinal wave signals through each element in the ultrasonic phased array, so that the transverse wave signals and longitudinal wave signals reach the target material simultaneously.

[0136] The full matrix data composition module 20 is used to receive nonlinear signals through each array element in the ultrasonic phased array to form full matrix data.

[0137] The data decomposition module 30 is used to obtain, based on the full matrix data, the first matrix data corresponding to the difference frequency shear wave signal, the second matrix data corresponding to the sum frequency shear wave signal, and the third matrix data corresponding to the higher harmonic signal of the longitudinal wave through variational mode decomposition. The higher harmonic signal is a second or higher harmonic signal.

[0138] The defect imaging data acquisition module 40 is used to acquire, based on the first matrix data, the second matrix data, and the third matrix data, the first defect imaging data corresponding to the difference frequency shear wave signal, the second defect imaging data corresponding to the sum frequency shear wave signal, and the third defect imaging data corresponding to the higher harmonic signal of the longitudinal wave.

[0139] The defect detection result acquisition module 50 is used to acquire the defect detection results of the target material based on the first defect imaging data, the second defect imaging data and the third defect imaging data.

[0140] It should be understood that the above-described device is used to execute the methods in the above embodiments. The implementation principle and technical effect of the corresponding program modules in the device are similar to those described in the above methods. The working process of the device can be referred to the corresponding process in the above methods, and will not be repeated here.

[0141] Based on the methods described in the above embodiments, this invention provides an electronic device. The device may include at least one memory for storing a program and at least one processor for executing the program stored in the memory. When the program stored in the memory is executed, the processor performs the methods described in the above embodiments.

[0142] Based on the methods in the above embodiments, this embodiment of the invention provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0143] Based on the methods in the above embodiments, this embodiment of the invention provides a computer program product that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0144] It is understood that the processor in the embodiments of the present invention can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor can be a microprocessor or any conventional processor.

[0145] The method steps in these embodiments of the invention can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside in an ASIC.

[0146] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present invention are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0147] It is understood that the various numerical designations used in the embodiments of the present invention are merely for the convenience of description and are not intended to limit the scope of the embodiments of the present invention.

[0148] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for defect imaging based on nonlinear ultrasonic mixing and high harmonic phased arrays, characterized in that, include: The transverse wave signal and the longitudinal wave signal are excited by each element in the ultrasonic phased array, and the transverse wave signal and the longitudinal wave signal reach the target material simultaneously. The nonlinear signals received by each element in the ultrasonic phased array are used to form full matrix data. Based on the full matrix data, variational mode decomposition is used to obtain the first matrix data corresponding to the difference frequency shear wave signal, the second matrix data corresponding to the sum frequency shear wave signal, and the third matrix data corresponding to the higher harmonic signals of the longitudinal wave, wherein the higher harmonic signals are second-order or higher harmonic signals. Based on the first matrix data, the second matrix data and the third matrix data, the first defect imaging data corresponding to the difference frequency shear wave signal, the second defect imaging data corresponding to the sum frequency shear wave signal and the third defect imaging data corresponding to the higher harmonic signal of the longitudinal wave are obtained. Based on the first defect imaging data, the second defect imaging data, and the third defect imaging data, the defect detection results of the target material are obtained.

2. The method according to claim 1, wherein, The step of acquiring first defect imaging data corresponding to the difference-frequency shear wave signal, second defect imaging data corresponding to the sum-frequency shear wave signal, and third defect imaging data corresponding to the higher harmonic signals of the longitudinal wave based on the first matrix data, the second matrix data, and the third matrix data includes: Perform the following operations on any one of the target signals: the difference frequency shear wave signal, the sum frequency shear wave signal, and the higher harmonic signal of the longitudinal wave: Based on the matrix data corresponding to the target signal, the amplitude corresponding to each pixel in the imaging area is obtained through a full-focus imaging algorithm; Based on the amplitude value corresponding to each pixel in the imaging region, obtain the complex domain signal corresponding to each pixel in the imaging region; Based on the complex domain signal corresponding to each pixel in the imaging region, the defect imaging data corresponding to the target signal is obtained through filtering.

3. The method according to claim 2, wherein, The step of obtaining the complex domain signal corresponding to each pixel in the imaging region based on the amplitude value of each pixel in the imaging region includes obtaining the complex domain signal corresponding to each pixel through the following formula: I2 = Hilbert(I(x,y)); Where I(x,y) represents the magnitude of the pixel, Hilbert(·) represents the Hilbert transform, and I2 represents the complex domain signal of the pixel.

4. The method according to claim 3, wherein, The defect imaging data corresponding to the target signal is obtained by filtering the complex domain signal corresponding to each pixel in the imaging region, including filtering using the following formula: wherein I2represents a complex domain signal corresponding to a pixel point, |I2| max represents a maximum value of the absolute value of I2, and I3represents a defect imaging value corresponding to the pixel point after the filtering processing.

5. The method of claim 1, wherein, The process of receiving nonlinear signals from each element of the ultrasonic phased array to form full matrix data includes: For each element in the ultrasonic phased array, the first signal is received by first exciting the positive phase fundamental wave of the element, and then the second signal is received by exciting the negative phase fundamental wave. Based on the first signal and the second signal received by each array element, the nonlinear signal received by each array element is obtained. The full matrix data is composed based on the nonlinear signals received by each array element.

6. The defect imaging method based on nonlinear ultrasonic mixing and high-order harmonic phased array according to claim 5, characterized in that, The step of obtaining the nonlinear signal received by each array element based on the first signal and the second signal received by each array element includes obtaining the nonlinear signal received by the array element using the following formula: wherein u c represents a nonlinear signal received by an array element, u1 represents the first signal, and u2 represents the second signal.

7. The defect imaging method based on nonlinear ultrasonic mixing and high-order harmonic phased array according to any one of claims 1-6, characterized in that, The process of exciting transverse and longitudinal wave signals through each element of the ultrasonic phased array includes: For any two adjacent array elements in the ultrasonic phased array, first control one array element to excite a transverse wave signal, and then control the other array element to excite a longitudinal wave signal. The excitation time difference between the transverse wave signal and the longitudinal wave signal is determined based on a first time taken for the transverse wave signal to propagate to the target material and a second time taken for the longitudinal wave signal to propagate to the target material.

8. A defect imaging device based on nonlinear ultrasonic mixing and high-order harmonic phased array, characterized in that, include: The signal excitation module is used to excite transverse wave signals and longitudinal wave signals through each element in the ultrasonic phased array, and the transverse wave signals and the longitudinal wave signals arrive at the target material simultaneously. The full matrix data composition module is used to receive nonlinear signals through each array element in the ultrasonic phased array and compose full matrix data. The data decomposition module is used to obtain, based on the full matrix data, the first matrix data corresponding to the difference frequency shear wave signal, the second matrix data corresponding to the sum frequency shear wave signal, and the third matrix data corresponding to the higher harmonic signal of the longitudinal wave through variational mode decomposition, wherein the higher harmonic signal is a second or higher harmonic signal. The defect imaging data acquisition module is used to acquire, based on the first matrix data, the second matrix data and the third matrix data, the first defect imaging data corresponding to the difference frequency shear wave signal, the second defect imaging data corresponding to the sum frequency shear wave signal and the third defect imaging data corresponding to the higher harmonic signal of the longitudinal wave. The defect detection result acquisition module is used to acquire the defect detection result of the target material based on the first defect imaging data, the second defect imaging data and the third defect imaging data.

9. An electronic device, characterized in that, include: At least one memory for storing programs; At least one processor is configured to execute a program stored in the memory, wherein when the program stored in the memory is executed, the processor is configured to perform the method as described in any one of claims 1-7.

10. A non-transitory computer-readable storage medium storing a computer program, characterized in that, When the computer program is run on the processor, it causes the processor to perform the method as described in any one of claims 1-7.

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