Nondestructive testing method and device for layering defect of composite material based on laser ultrasound

Abstract

The invention provides a nondestructive testing method and device for layering defects of a composite material based on laser ultrasound, and the method comprises the following steps: obtaining a to-be-tested composite material, and carrying out the laser ultrasound testing of the to-be-tested composite material, so as to obtain a three-dimensional ultrasonic field signal, performing three-dimensional Fourier transform on the three-dimensional ultrasonic field signal to obtain single-frequency ultrasonic signals of different frequency bands; a wave number domain band-pass filter is used for filtering out wave number components of each level from the corresponding single-frequency ultrasonic signals; and calculating the wave field energy diagram of each level based on the wave number component of each level of each frequency band, acquiring the level corresponding to the wave field energy diagram with the maximum image contrast as a hierarchical defect level, and imaging the hierarchical defect level by adopting two-dimensional wavelet transform to obtain a detection result. According to the scheme, a self-adaptive wavenumber domain band-pass filter is constructed for the theoretical wavenumber sorting of the Lamb waves at different levels of the composite material to be detected, and the optimal scale is determined based on the image comparison coefficient to perform high-precision imaging on defect levels.

Description

Technical Field

[0001] The present application relates to the field of nondestructive testing, and in particular to a laser ultrasound-based nondestructive testing method and device for composite material delamination defects. Background Art

[0002] Composite materials have the advantages of high specific strength and specific stiffness, high temperature resistance, corrosion resistance, and good fatigue resistance. They have been widely used in important industries such as wind power, aerospace, automobiles, and construction. However, during the manufacturing and service process, composite materials are prone to various defects. Delamination defects are one of the most common defect modes, and the formation and expansion of such defects occur inside the material and are not easy to detect.

[0003] The ultrasonic laser nondestructive testing method has the advantages of non-contact and long-distance detection, flexible regulation, high sensitivity to tiny defects, high resolution, and the ability to simultaneously emit different models of ultrasonic waves. In view of the structural characteristics of multi-layer paving of composite materials, the Lamb waves emitted by the laser are mainly propagated in the layered structure with a large length-to-thickness ratio, and have the characteristics of long propagation distance, small attenuation, and high sensitivity of the acoustic wave characteristics to material properties. When the Lamb wave propagates to the delamination defect, its wave number components are prone to large changes. Extracting these wave number components that are sensitive to delamination defects and performing local wave number analysis can achieve high-precision detection of delamination defects. Therefore, the existing ultrasonic laser nondestructive testing methods generally use Lamb waves for detection.

[0004] However, the existing methods for detecting delamination defects based on ultrasonic Lamb waves have the following main problems: 1. Most methods ignore the multi-layer characteristics of the structure and the anisotropy of the mechanical properties of composite materials. When filtering the Lamb wave signal in the wavenumber domain, the constructed wavenumber filter is usually a regular circle, which does not match the propagation directionality of the Lamb wave in the material, resulting in the inability to effectively extract the wavenumber components sensitive to delamination defects; 2. Some methods perform local wavenumber analysis on the extracted wavenumber components based on two-dimensional wavelet transform to achieve imaging of delamination defects. However, the main parameters of the two-dimensional wavelet transform, such as the scale factor, have a great influence on the imaging resolution, and the Lamb wave in the composite material has a wide-band characteristic, and the optimal scale factors corresponding to different frequency components are not necessarily the same. The existing methods basically select the scale factor manually, and lack a quantitative method to determine the optimal scale factor for a given frequency. In addition, most current studies focus on evaluating the size and shape of delamination defects, and the research on the location of the depth of delamination defects is relatively limited.

[0005] In summary, how to effectively extract the wavenumber components that are sensitive to delamination defects and use the optimal scale factor to image delamination defects is a problem that needs to be solved urgently in the existing technology. Summary of the invention

[0006] The embodiment of the present application provides a method and device for nondestructive detection of composite material delamination defects based on laser ultrasound. By constructing an adaptive wavenumber domain bandpass filter by sorting the theoretical wavenumbers of Lamb waves at different levels of the composite material to be tested and matching the directivity of the Lamb wave field, the wavenumber components sensitive to delamination defects can be more effectively extracted, and the optimal scale of the two-dimensional wavelet transform is determined based on the image contrast coefficient to perform high-precision imaging of the defect level.

[0007] In a first aspect, an embodiment of the present application provides a nondestructive detection method for composite material delamination defects based on laser ultrasound, the method comprising: Acquire a composite material to be tested, perform laser ultrasonic testing on the composite material to be tested to obtain a three-dimensional ultrasonic field signal, perform three-dimensional Fourier transformation on the three-dimensional ultrasonic field signal and then filter it to a set frequency band interval to obtain a multi-frequency ultrasonic signal, wherein the multi-frequency ultrasonic signal includes single-frequency ultrasonic signals of different frequency bands; Obtaining a theoretical dispersion curve of Lamb waves in the composite material to be tested, obtaining theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested based on the theoretical dispersion curve, sorting the theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested from large to small to obtain a wave number domain bandpass filter, and using the wave number domain bandpass filter to filter out the wave number components of each level in the corresponding single-frequency ultrasonic signal; The wave field energy map of each level is calculated based on the wave number components of each level in each frequency band. The level corresponding to the wave field energy map with the largest image contrast is the delamination defect level. The delamination defect level is imaged using two-dimensional wavelet transform to obtain the detection result.

[0008] In a second aspect, the embodiment of the present application provides a nondestructive detection device for composite material delamination defects based on laser ultrasound, comprising: an acquisition module, used for acquiring the composite material to be tested, performing laser ultrasonic detection on the composite material to be tested to obtain a three-dimensional ultrasonic field signal, performing three-dimensional Fourier transform on the three-dimensional ultrasonic field signal and filtering it to a set frequency band interval to obtain a multi-frequency ultrasonic signal, wherein the multi-frequency ultrasonic signal includes single-frequency ultrasonic signals of different frequency bands; A filtering module is used to obtain a theoretical dispersion curve of Lamb waves in the composite material to be tested, obtain the theoretical wave number of each single-frequency ultrasonic signal at different levels of the composite material to be tested based on the theoretical dispersion curve, sort the theoretical wave number of each single-frequency ultrasonic signal at different levels of the composite material to be tested from large to small to obtain a wave number domain bandpass filter, and use the wave number domain bandpass filter to filter out the wave number component of each level in the corresponding single-frequency ultrasonic signal; The detection module calculates the wave field energy map of each level based on the wave number components of each level in each frequency band, obtains the level corresponding to the wave field energy map with the largest image contrast as the delamination defect level, and uses two-dimensional wavelet transform to image the delamination defect level to obtain the detection result.

[0009] In a third aspect, an embodiment of the present application provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to perform a laser ultrasound-based nondestructive detection method for composite material delamination defects.

[0010] In a fourth aspect, an embodiment of the present application provides a readable storage medium, in which a computer program is stored. The computer program includes a program code for controlling a process to execute a process, and the process includes a laser ultrasonic-based nondestructive detection method for composite material delamination defects.

[0011] The main contributions and innovations of the present invention are as follows: The embodiment of the present application takes into account the multi-layer characteristics and anisotropy of composite materials. By sorting the theoretical wavenumbers of Lamb waves at different levels of the composite material to be tested, a wavenumber domain bandpass filter is constructed to match the directivity of the Lamb wave field, thereby more effectively extracting wavenumber components sensitive to delamination defects. In the two-dimensional wavelet transform imaging link, the embodiment of the present application calculates the image contrast coefficients at different wavelet scales to determine the optimal wavelet scale, thereby avoiding the blindness of manual selection and achieving more accurate delamination defect imaging. When detecting delamination defects of composite materials, this scheme can more accurately locate the level of the delamination defects and improve the imaging resolution, thereby achieving high-precision detection of delamination defects of composite materials and better meeting the needs of wind power, aerospace and other industries for composite material quality inspection.

[0012] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 is a flow chart of a method for nondestructive detection of composite material delamination defects based on laser ultrasound according to an embodiment of the present application; Figure 2 is a schematic structural diagram of a laser ultrasound system according to an embodiment of the present application; Figure 3 is a schematic diagram of a wave number filter for different thicknesses according to an embodiment of the present application; Figure 4 is a structural block diagram of a data storage device according to an embodiment of the present application; Figure 5 It is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present application. DETAILED DESCRIPTION

[0014] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with one or more embodiments of this specification. Instead, they are merely examples of devices and methods consistent with some aspects of one or more embodiments of this specification as detailed in the appended claims.

[0015] It should be noted that: in other embodiments, the steps of the corresponding method are not necessarily performed in the order shown and described in this specification. In some other embodiments, the steps included in the method may be more or less than those described in this specification. In addition, a single step described in this specification may be decomposed into multiple steps for description in other embodiments; and multiple steps described in this specification may be combined into a single step for description in other embodiments.

[0016] Embodiment 1 The embodiment of the present application provides a nondestructive detection method for composite material delamination defects based on laser ultrasound. By constructing an adaptive wavenumber domain bandpass filter by sorting the theoretical wavenumbers of Lamb waves at different levels of the composite material to be tested, the wavenumber components sensitive to delamination defects can be more effectively extracted, and the optimal scale of two-dimensional wavelet transform is determined based on the image contrast coefficient to perform high-precision imaging of the defect level. Specifically, reference Figure 1 , the method comprising: Acquire a composite material to be tested, perform laser ultrasonic testing on the composite material to be tested to obtain a three-dimensional ultrasonic field signal, perform three-dimensional Fourier transformation on the three-dimensional ultrasonic field signal and then filter it to a set frequency band interval to obtain a multi-frequency ultrasonic signal, wherein the multi-frequency ultrasonic signal includes single-frequency ultrasonic signals of different frequency bands; Obtaining a theoretical dispersion curve of Lamb waves in the composite material to be tested, obtaining theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested based on the theoretical dispersion curve, sorting the theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested from large to small to obtain a wave number domain bandpass filter, and using the wave number domain bandpass filter to filter out the wave number components of each level in the corresponding single-frequency ultrasonic signal; The wave field energy map of each level is calculated based on the wave number components of each level in each frequency band. The level corresponding to the wave field energy map with the largest image contrast coefficient is the delamination defect level. The delamination defect level is imaged using two-dimensional wavelet transform to obtain the imaging result, and then the delamination detection result is obtained based on the imaging result.

[0017] In some embodiments, a laser ultrasonic system is constructed to perform laser ultrasonic detection on the composite material to be tested. The structural schematic diagram of the laser ultrasonic system is as shown in FIG. Figure 2 As shown, the laser ultrasonic system includes a laser emitting unit, an ultrasonic acquisition unit and a system control unit. The laser emitting unit emits high-energy pulse laser to the composite material to be tested through a pulse laser. The composite material to be tested generates Lamb waves in response to the high-energy pulse laser and is acquired by the ultrasonic acquisition unit to obtain a three-dimensional ultrasonic field signal. The system control unit is used to control laser emitting parameters and acquisition parameters.

[0018] Specifically, the laser emission parameters include scanning mode, scanning path, number of scanning points, scanning interval, laser power, etc., and the acquisition parameters include acquisition frequency, acquisition time, etc.

[0019] Exemplarily, the average output power of the laser used in this solution is 20W, and the laser wavelength is 1064nm. An ultrasonic probe is installed at a suitable position of the ultrasonic acquisition unit to collect Lamb waves. The acquisition frequency is set to 50MHz, and the acquisition time is set to 40.96μm. The system control unit is used to control parameters such as scanning mode, number of scanning points, scanning spacing, laser power and sampling frequency. In this example, the surface of the test piece is scanned, the scanning path is S-shaped, the scanning area is a rectangular area of ​​16mm×16mm, and the scanning interval is 0.16mm. Based on the above detection method, each scanning point irradiated by the laser can excite Lamb waves in the test piece. The Lamb waves propagate in the test piece and are finally collected by the ultrasonic probe. The three-dimensional ultrasonic field signal finally collected in this example It is 100×100×2048 points, 100 is the number of scanning points in the x direction and y direction in the scanning area, and 2048 is the number of points of ultrasonic signals collected at each scanning point.

[0020] Furthermore, the detection method in this solution is surface scanning excitation-fixed point detection, and can also be applied to detection occasions where the relative positions of the excitation and detection points are fixed and both move simultaneously.

[0021] In some embodiments, the formula for performing three-dimensional Fourier transform on the three-dimensional ultrasonic field signal is expressed as follows:

[0022] in, is the frequency, and is the wave number in the x direction, is the wave number in the y direction, It is the frequency-wavenumber domain data after three-dimensional Fourier transform.

[0023] The formula for filtering the frequency-wavenumber domain data to the set frequency band interval is as follows:

[0024] in, To set the upper cutoff frequency of the frequency band, To set the lower cutoff frequency of the frequency band, represents the transfer function of the bandpass filter, It is a multi-frequency ultrasonic signal.

[0025] Specifically, the set frequency band interval is a Lamb wave frequency band interval affected by delamination defects, and the set frequency band interval is adjusted according to the frequency range of the actually collected ultrasonic signal.

[0026] For example, the Lamb wave signal in the frequency band of 100kHz - 500kHz of some composite materials is significantly affected by the delamination defects, so the set frequency band interval is set to 100KHz-500KHz to reduce other noise interference.

[0027] In some specific embodiments, the theoretical dispersion curve is a curve showing the relationship between the propagation characteristics of Lamb waves in the composite material to be tested and the frequency and material thickness.

[0028] In some embodiments, the theoretical wave number formula of each single-frequency ultrasonic signal at different layers of the composite material to be tested is expressed as: ,in, is the theoretical wave number, , is the frequency band, For the level, Represents the thickness of the top i layer of the composite material.

[0029] In some embodiments, the theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested are sorted in descending order to obtain a formula for a wave number domain bandpass filter as follows:

[0030] in, The frequency band is , the level is The wavenumber domain bandpass filter, represents the upper boundary of the filter, represents the lower boundary of the filter, The frequency band is , the level is The theoretical wave number, The frequency band is , the level is The theoretical wave number, m+1 is The sequence number after sorting, m-1 is The sorted sequence number, is the wave number in the x direction, is the wave number in the y direction.

[0031] Specifically, there is a composite material with n layers, then represents the thickness of the first layer of the composite material, represents the thickness of the first two layers of the composite material, Represents the thickness of the entire composite material, that is, ~ It indicates the location where the potential stratification occurs. When the wavenumber component filtered out by the wavenumber domain bandpass filter is The theoretical wave number at is the same as that at which the composite material has a delamination defect between the first and second layers. If the theoretical wave number at the position deviates, it means that there is a delamination defect between the second and third layers of the composite material. If the theoretical wave number at is the same, it means that the composite material has no delamination defects.

[0032] For example, assuming that the total thickness of the composite material is d n If the composite material has no delamination defects, the Lamb wave number in the material is only n If there are delamination defects in the first and second layers, in addition to the thickness d n The wave number corresponding to the thickness d1 is also included, so we first construct filters of various levels to filter out the wave numbers corresponding to various thicknesses. n The thickness filter, other filters are actually useless, they can only filter out the wave number components that are far from the theoretical wave number, and then the level of the delamination defect can be confirmed by the image contrast coefficient. Similarly, if there is a delamination defect in the first and second layers, the filter with the thickness of d1 here can filter out the wave number.

[0033] in addition, , ,in, represents the spatial resolution of the wavefield, The minimum value of the filter band used to limit the wavenumber domain bandpass filter is 0. The maximum value of the filter band used to limit the filter is .

[0034] Specifically, since composite materials are anisotropic materials, the Lamb wave field will be affected by multiple factors such as the laying method, fiber direction, material thickness, etc., and its wave number will fluctuate greatly in all horizontal directions. Unlike isotropic materials, the Lamb wave field propagates uniformly in all directions, and the wave number is usually monotonically decreasing with the thickness. Therefore, if the anisotropic characteristics of composite materials are ignored, the designed wave number domain filters for each thickness are usually regular ring shapes. Therefore, this scheme uses a wave number domain bandpass filter constructed by sorting the theoretical wave number to match the directivity of the Lamb wave field in the composite material. The constructed wave number filters for different thicknesses are as follows: Figure 3 As shown, they all have specific shapes, which can isolate the wavenumber component related to the ply thickness above the potential delamination defect and then identify the potential delamination defect location.

[0035] In some embodiments, the formula for filtering out each level of wavenumber components from the corresponding single-frequency ultrasonic signal using the wavenumber domain bandpass filter is as follows:

[0036] in, Indicates frequency band , the level is The wave number component of The frequency band is A single-frequency ultrasonic signal, The frequency band is , the level is Wavenumber domain bandpass filter.

[0037] In some embodiments, in the step of calculating the wavefield energy map of each level based on the wavenumber components of each level of each frequency band, a two-dimensional inverse Fourier transform is performed on the wavenumber components of each level of each frequency band to obtain a frequency-space domain wavefield, and the wavenumber components of the same level in each frequency band are integrated to obtain the wavefield energy map of each level.

[0038] Specifically, the formula for obtaining the frequency-space domain wave field by performing a two-dimensional inverse Fourier transform on each level of the wave number components in each frequency band is as follows:

[0039] in, The frequency band is , the level is The frequency-space domain wave field, Indicates frequency band , the level is The wave number component of .

[0040] Specifically, the formula for integrating the wave number components of the same level in each frequency band to obtain the wave field energy diagram of each level is as follows:

[0041] in, Indicates the level The wave field energy diagram, The frequency band is , the level is The square of the frequency-space domain wavefield.

[0042] In some embodiments, the image contrast coefficient of each wave field energy map is calculated, and the level corresponding to the wave field energy map with the largest image contrast coefficient is selected as the delamination defect level.

[0043] Specifically, the formula for calculating the image contrast coefficient of the wave field energy map is as follows:

[0044] in, For the level The image contrast coefficient of the wave field energy map, Indicates the level The wave field energy diagram, Nx represents the number of data points in the x direction, Ny represents the number of data points in the y direction, p, q, p n and q n It is used to represent the four points before, after, left and right of the selected point. n and q n Take three values: -1, 0, and 1.

[0045] In some specific embodiments, since there is a significant difference in wave number between the level with delamination defects and the undamaged area, the level with the largest image contrast coefficient is taken as the delamination defect level, and the formula is expressed as follows:

[0046] Where D is the delamination defect level, For the level The image contrast coefficient of the wave field energy map.

[0047] In some embodiments, a two-dimensional wavelet transform is performed on the frequency-space domain wavefield of each frequency band at the stratified defect level to obtain a wavelet wavefield corresponding to each frequency band, the values ​​of each wavelet wavefield at all rotation angles are summed to obtain multiple full-range wavelet wavefields, the image contrast coefficient at each wavelet scale in each full-range wavelet wavefield is calculated, and the wavelet scale with the largest image contrast coefficient is selected as the optimal wavelet scale corresponding to the full-range wavelet wavefield, the full-range wavelet wavefield at each optimal wavelet scale is obtained as the optimal wavelet wavefield, the optimal wavelet wavefield corresponding to each frequency band is weighted averaged to obtain a wavelet wavefield energy map of the stratified defect level, and imaging is performed based on the wavelet wavefield energy map.

[0048] Specifically, the frequency-space domain wave field of each frequency band under the layered defect level is subjected to a two-dimensional wavelet transform to obtain the wavelet wave field corresponding to each frequency band one by one, and the formula is expressed as follows:

[0049] in, It is a small wave field. is the wavelet scale and ∈(0,+∞), β is the rotation angle in the two-dimensional wavelet transform and β∈(0,2π,), is the layered defect level D, frequency band The frequency-space domain wave field of

[0050] Specifically, the formula for obtaining multiple full-range wavelet fields by summing the values ​​of each wavelet field at all rotation angles is expressed as:

[0051] in, is the full range wavelet field, It is a small wave field.

[0052] Specifically, since the rotation angle β reflects the propagation characteristics of the Lamb wave in this direction, and the propagation of the Lamb wave field in the composite material is different in all directions, the wavelet wavefields at all rotation angles are summed to obtain the full range wavelet wavefield.

[0053] Specifically, the formula for calculating the image contrast coefficient at each wavelet scale in each full-range wavelet wavefield is as follows:

[0054] in, Indicates frequency band , wavelet scale The image contrast coefficient when is the full range wavelet wavefield, Nx represents the number of data points in the x direction, and Ny represents the number of data points in the y direction.

[0055] Specifically, the formula for selecting the wavelet scale with the largest image contrast coefficient as the optimal wavelet scale corresponding to the full range wavelet field is as follows:

[0056] in, Indicates frequency band , wavelet scale The image contrast factor at .

[0057] Specifically, the formula for obtaining the wavelet field energy map of the hierarchical defect level by weighted averaging the best wavelet field corresponding to each frequency band is as follows:

[0058] in, is the wavelet field energy diagram, is the optimal wavelet field corresponding to each frequency band.

[0059] Furthermore, the obtained wavelet wave field energy map can be used to achieve high-precision imaging of delamination defects, thereby completing the inspection of the composite material to be inspected.

[0060] Embodiment 2 Based on the same idea, refer to Figure 4 , the present application also proposes a nondestructive detection device for composite material delamination defects based on laser ultrasound, comprising: an acquisition module, used for acquiring the composite material to be tested, performing laser ultrasonic detection on the composite material to be tested to obtain a three-dimensional ultrasonic field signal, performing three-dimensional Fourier transform on the three-dimensional ultrasonic field signal and filtering it to a set frequency band interval to obtain a multi-frequency ultrasonic signal, wherein the multi-frequency ultrasonic signal includes single-frequency ultrasonic signals of different frequency bands; A filtering module is used to obtain a theoretical dispersion curve of Lamb waves in the composite material to be tested, obtain the theoretical wave number of each single-frequency ultrasonic signal at different levels of the composite material to be tested based on the theoretical dispersion curve, sort the theoretical wave number of each single-frequency ultrasonic signal at different levels of the composite material to be tested from large to small to obtain a wave number domain bandpass filter, and use the wave number domain bandpass filter to filter out the wave number component of each level in the corresponding single-frequency ultrasonic signal; The detection module calculates the wave field energy map of each level based on the wave number components of each level in each frequency band, obtains the level corresponding to the wave field energy map with the largest image contrast as the delamination defect level, and uses two-dimensional wavelet transform to image the delamination defect level to obtain the detection result.

[0061] Embodiment 3 This embodiment also provides an electronic device, referring to Figure 5, comprises a memory 404 and a processor 402, wherein the memory 404 stores a computer program, and the processor 402 is configured to run the computer program to execute the steps in any of the above method embodiments.

[0062] Specifically, the processor 402 may include a central processing unit (CPU), or an application specific integrated circuit (ASIC), or may be configured to implement one or more integrated circuits of the embodiments of the present application.

[0063] Among them, the memory 404 may include a large capacity memory 404 for data or instructions. For example, but not limitation, the memory 404 may include a hard disk drive (HDD), a floppy disk drive, a solid state drive (SSD), a flash memory, an optical disk, a magneto-optical disk, a tape, or a universal serial bus (USB) drive, or a combination of two or more of these. In appropriate cases, the memory 404 may include a removable or non-removable (or fixed) medium. In appropriate cases, the memory 404 may be inside or outside the data processing device. In a specific embodiment, the memory 404 is a non-volatile memory. In a specific embodiment, the memory 404 includes a read-only memory (ROM) and a random access memory (RAM). Where appropriate, the ROM may be a mask-programmed ROM, a programmable ROM (Programmable Read-Only Memory, PROM for short), an erasable PROM (Erasable Programmable Read-Only Memory, EPROM for short), an electrically erasable PROM (Electrically Erasable Programmable Read-Only Memory, EEPROM for short), an electrically alterable ROM (Electrically Alterable Read-Only Memory, EAROM for short) or a flash memory (FLASH) or a combination of two or more of these. In appropriate circumstances, the RAM may be a static random access memory (SRAM) or a dynamic random access memory (DRAM), wherein the DRAM may be a fast page mode dynamic random access memory 404 (FPMDRAM), an extended data output dynamic random access memory (EDODRAM), a synchronous dynamic random access memory (SDRAM), etc.

[0064] The memory 404 may be used to store or cache various data files required for processing and / or communication, as well as possible computer program instructions executed by the processor 402 .

[0065] The processor 402 reads and executes the computer program instructions stored in the memory 404 to implement any one of the laser ultrasonic-based nondestructive detection methods for composite material delamination defects in the above embodiments.

[0066] Optionally, the electronic device may further include a transmission device 406 and an input / output device 408 , wherein the transmission device 406 is connected to the processor 402 , and the input / output device 408 is connected to the processor 402 .

[0067] The transmission device 406 can be used to receive or send data via a network. Specific examples of the above-mentioned network may include a wired or wireless network provided by a communication provider of the electronic device. In one example, the transmission device includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device 406 can be a radio frequency (Radio Frequency, referred to as RF) module, which is used to communicate with the Internet wirelessly.

[0068] The input / output device 408 is used to input or output information. In this embodiment, the input information may be a three-dimensional ultrasonic field signal of the composite material to be tested, and the output information may be a delamination defect level, etc.

[0069] Optionally, in this embodiment, the processor 402 may be configured to perform the following steps through a computer program: Acquire a composite material to be tested, perform laser ultrasonic testing on the composite material to be tested to obtain a three-dimensional ultrasonic field signal, perform three-dimensional Fourier transformation on the three-dimensional ultrasonic field signal and then filter it to a set frequency band interval to obtain a multi-frequency ultrasonic signal, wherein the multi-frequency ultrasonic signal includes single-frequency ultrasonic signals of different frequency bands; Obtaining a theoretical dispersion curve of Lamb waves in the composite material to be tested, obtaining theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested based on the theoretical dispersion curve, sorting the theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested from large to small to obtain a wave number domain bandpass filter, and using the wave number domain bandpass filter to filter out the wave number components of each level in the corresponding single-frequency ultrasonic signal; The wave field energy map of each level is calculated based on the wave number components of each level in each frequency band. The level corresponding to the wave field energy map with the largest image contrast is the delamination defect level. The delamination defect level is imaged using two-dimensional wavelet transform to obtain the detection result.

[0070] It should be noted that the specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementation modes, and this embodiment will not be described in detail here.

[0071] In general, various embodiments may be implemented in hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software executed by a controller, microprocessor, or other computing device, but the invention is not limited thereto. Although various aspects of the invention may be shown and described as block diagrams, flow charts, or using some other graphical representation, it should be understood that, as non-limiting examples, the boxes, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0072] Embodiments of the present invention may be implemented by computer software that is executable by a data processor of a mobile device, such as in a processor entity, or by hardware, or by a combination of software and hardware. Computer software or programs (also referred to as program products) including software routines, applets and / or macros may be stored in any device-readable data storage medium, and they include program instructions for performing specific tasks. A computer program product may include one or more computer executable components configured to perform an embodiment when the program is run. One or more computer executable components may be at least one software code or a portion thereof. In addition, at this point, it should be noted that, for example, Figure 5 Any block of the logic flow in the program may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on physical media such as memory chips or storage blocks implemented within a processor, magnetic media such as hard disks or floppy disks, and optical media such as, for example, DVDs and their data variants, CDs, etc. Physical media are non-transitory media.

[0073] Those skilled in the art should understand that the technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0074] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A laser ultrasonic nondestructive testing method for composite material delamination defects, characterized in that: The following steps are involved: Acquire a composite material to be tested, perform laser ultrasonic testing on the composite material to be tested to obtain a three-dimensional ultrasonic field signal, perform three-dimensional Fourier transformation on the three-dimensional ultrasonic field signal and then filter it to a set frequency band interval to obtain a multi-frequency ultrasonic signal, wherein the multi-frequency ultrasonic signal includes single-frequency ultrasonic signals of different frequency bands; Obtaining a theoretical dispersion curve of Lamb waves in the composite material to be tested, obtaining theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested based on the theoretical dispersion curve, sorting the theoretical wave numbers of each single-frequency ultrasonic signal at different levels of the composite material to be tested from large to small to obtain a wave number domain bandpass filter, and using the wave number domain bandpass filter to filter out the wave number components of each level in the corresponding single-frequency ultrasonic signal; The wave field energy map of each level is calculated based on the wave number components of each level in each frequency band. The level corresponding to the wave field energy map with the largest image contrast coefficient is the delamination defect level. The delamination defect level is imaged using two-dimensional wavelet transform to obtain the imaging result, and then the delamination detection result is obtained based on the imaging result.

2. The laser ultrasound-based nondestructive testing method for composite material delamination defects according to claim 1, characterized in that: The laser ultrasonic system includes a laser emitting unit, an ultrasonic acquisition unit and a system control unit. The laser emitting unit emits high-energy pulsed laser to the composite material to be tested through a pulsed laser. The composite material to be tested generates Lamb waves in response to the high-energy pulsed laser and is acquired by the ultrasonic acquisition unit to obtain a three-dimensional ultrasonic field signal. The system control unit is used to control laser emitting parameters and acquisition parameters.

3. The laser ultrasonic nondestructive testing method for composite material delamination defects according to claim 1, characterized in that: The theoretical wave number of each single-frequency ultrasonic signal at different levels of the composite material to be tested is sorted from large to small to obtain the formula of the wave number domain bandpass filter as follows: ； in, The frequency band is , the level is The wavenumber domain bandpass filter, represents the upper boundary of the wavenumber domain bandpass filter, represents the lower boundary of the wavenumber domain bandpass filter, The frequency band is , the level is The theoretical wave number, The frequency band is , the level is The theoretical wave number, m+1 is The sequence number after sorting, m-1 is The sorted sequence number, is the wave number in the x direction, is the wave number in the y direction.

4. The laser ultrasonic nondestructive testing method for composite material delamination defects according to claim 1, characterized in that: The formula for filtering out each level of wavenumber components from the corresponding single-frequency ultrasonic signal using the wavenumber domain bandpass filter is as follows: ； in, Indicates frequency band , the level is The wave number component of The frequency band is A single-frequency ultrasonic signal, The frequency band is , the level is Wavenumber domain bandpass filter.

5. The laser ultrasonic nondestructive testing method for composite material delamination defects according to claim 1, characterized in that: In the step of calculating the wave field energy map of each level based on the wave number components of each level of each frequency band, a two-dimensional inverse Fourier transform is performed on the wave number components of each level of each frequency band to obtain the frequency-space domain wave field, and the wave number components of the same level in each frequency band are integrated to obtain the wave field energy map of each level.

6. The laser ultrasound-based nondestructive testing method for composite material delamination defects according to claim 1, characterized in that: The formula for calculating the image contrast coefficient of the wave field energy map is as follows: ； in, For the level The image contrast coefficient of the wave field energy map, Indicates the level The wave field energy diagram, Nx represents the number of data points in the x direction, Ny represents the number of data points in the y direction, p, q, p n and q n It is used to represent the four points before, after, left and right of the selected point.

7. The laser ultrasound-based nondestructive testing method for composite material delamination defects according to claim 1, characterized in that: The frequency-space domain wavefield of each frequency band under the stratified defect level is subjected to a two-dimensional wavelet transform to obtain a wavelet wavefield corresponding to each frequency band. The values ​​of each wavelet wavefield at all rotation angles are summed to obtain multiple full-range wavelet wavefields. The image contrast coefficient at each wavelet scale in each full-range wavelet wavefield is calculated, and the wavelet scale with the largest image contrast coefficient is selected as the optimal wavelet scale corresponding to the full-range wavelet wavefield. The full-range wavelet wavefield at each optimal wavelet scale is obtained as the optimal wavelet wavefield. The optimal wavelet wavefield corresponding to each frequency band is weighted averaged to obtain a wavelet wavefield energy map of the stratified defect level, and imaging is performed based on the wavelet wavefield energy map.

8. A laser ultrasonic-based nondestructive testing device for composite material delamination defects, characterized in that: include: an acquisition module, used for acquiring the composite material to be tested, performing laser ultrasonic detection on the composite material to be tested to obtain a three-dimensional ultrasonic field signal, performing three-dimensional Fourier transform on the three-dimensional ultrasonic field signal and filtering it to a set frequency band interval to obtain a multi-frequency ultrasonic signal, wherein the multi-frequency ultrasonic signal includes single-frequency ultrasonic signals of different frequency bands; A filtering module is used to obtain a theoretical dispersion curve of Lamb waves in the composite material to be tested, obtain the theoretical wave number of each single-frequency ultrasonic signal at different levels of the composite material to be tested based on the theoretical dispersion curve, sort the theoretical wave number of each single-frequency ultrasonic signal at different levels of the composite material to be tested from large to small to obtain a wave number domain bandpass filter, and use the wave number domain bandpass filter to filter out the wave number component of each level in the corresponding single-frequency ultrasonic signal; The detection module calculates the wave field energy map of each level based on the wave number components of each level in each frequency band, obtains the level corresponding to the wave field energy map with the largest image contrast as the delamination defect level, and uses two-dimensional wavelet transform to image the delamination defect level to obtain the detection result.

9. An electronic device comprising a memory and a processor, characterized in that: The memory stores a computer program, and the processor is configured to run the computer program to execute the laser ultrasonic-based nondestructive detection method for composite material delamination defects as described in any one of claims 1 to 7.

10. A readable storage medium, characterized in that: The readable storage medium stores a computer program, which includes a program code for controlling a process to execute a process, wherein the process includes a laser ultrasonic-based nondestructive detection method for composite material delamination defects according to any one of claims 1 to 7.

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