Structural defect detection method and system based on mixed-frequency ultrasonic delayed excitation

Abstract

A structural defect detection method and system based on mixed-frequency ultrasonic delayed excitation. Four piezoelectric ceramic sensors are arranged in a rectangular pattern on a surface of a composite material layer. Mixed-frequency sound waves received by the two piezoelectric ceramic sensors undergo bandpass filtering, EMD decomposition and reconstruction, and frequency spectrum-energy spectrum analysis in sequence, then a modulation sideband parameter is extracted from a time-frequency spectrum, and a defect identification parameter is calculated on the basis of the modulation sideband parameter; if the defect identification parameter is greater than zero, a defect is present within a modulation aliasing region at excitation delay time; and if the defect identification parameter is less than zero, no defect is present within the modulation aliasing region at the excitation delay time. On the basis of a mixed-frequency excitation mode of delayed excitation of a low-frequency pump wave and a high-frequency detection wave, mixed-frequency incident waves do not need to be on the same axis, a sound wave aliasing region can be indirectly adjusted, and thus large-scale comprehensive scanning of the structure is achieved.

Description

Method and system for detecting structural defects by mixed frequency ultrasonic delay excitation

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present application claims priority to the Chinese patent application No. 202411160055.9, filed on August 22, 2024, and entitled "Method and system for detecting structural defects by mixed frequency ultrasonic delay excitation", the content of which is incorporated herein by reference in its entirety and forms a part of the present application for all purposes. TECHNICAL FIELD

[0003] The present application relates to the technical field of composite material defect detection, and in particular to a method and system for detecting structural defects by mixed frequency ultrasonic delay excitation. BACKGROUND

[0004] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0005] Composite materials are widely used in many fields such as aircraft, rockets, bridges, pipelines, and automobiles due to their high strength and light weight characteristics. They not only reduce the weight of equipment but also have advantages such as corrosion resistance, aging resistance, and fatigue resistance, which can greatly extend the service life of equipment structures. However, due to improper manufacturing processes or material defects, interlaminar defects (such as interlaminar separation, interlaminar voids, and interlaminar impurities) often occur in composite materials, which can cause insufficient bonding strength between layers and easily lead to shear bearing capacity failure under external load, even causing huge economic losses or major safety accidents. Therefore, effective identification and positioning of interlaminar defects in composite materials are crucial for ensuring the safe operation of equipment. For internal delamination and peeling defects in structures, they can generally be identified by ultrasonic testing technology and thermal imaging technology. However, when the delamination is in the very early stage, the transmission coefficient of the defect is very similar to that of the good bonding area, which makes it difficult for traditional detection techniques to detect the early defects. Therefore, developing effective methods for identifying and positioning interlaminar defects is a great challenge in the field of non-destructive testing and structural health monitoring.

[0006] Ultrasonic guided waves are formed by multiple reflections and further coupling of elastic waves within the structure, which can propagate throughout the thickness of the thin plate structure. They have the advantages of fast speed, high damage sensitivity, and real-time online monitoring of in-service structures, and have attracted much attention in recent years. Ultrasonic guided wave detection technology can be divided into linear ultrasonic detection methods and nonlinear ultrasonic detection methods. Linear ultrasonic detection methods are based on the principles of acoustic wave diffraction, reflection, and transmission, and use parameters such as sound speed and attenuation to characterize engineering component damage. However, they are only suitable for detecting macroscopic delamination damage and have great limitations in identifying early interlaminar defects.

[0007] Nonlinear ultrasonic testing technology can effectively overcome the shortcomings of linear ultrasonic testing technology which is not suitable for early micro-damage detection. By measuring the harmonic, sideband and other nonlinear parameters, the early performance degradation and early damage evolution process of the material can be effectively reflected. Studies have shown that the nonlinear components caused by interlaminar defects are more significant, and the nonlinear mixing acoustic modulation detection technology can significantly stimulate the weak nonlinear effects at the nearly perfect damage interface. Moreover, the nonlinear mixing acoustic modulation detection technology can be divided into collinear mixing detection technology and non-collinear mixing detection technology. This technology has obvious advantages such as frequency selection, direction control and spatial selection, thereby significantly improving the detection accuracy and helping to realize damage positioning. However, the collinear mixing method requires two incident waves on the same axis and has high precision requirements, which is difficult to implement. SUMMARY

[0008] In order to solve the problems of the prior art, the application provides a mixed-frequency ultrasonic delay excitation structure defect detection method and system. Based on the mixed-frequency excitation mode of low-frequency pump wave and high-frequency probe wave delay excitation, the mixed-frequency incident wave does not need to be on the same axis, and the acoustic aliasing region can be indirectly adjusted, thereby realizing large-scale comprehensive scanning of the structure.

[0009] In order to achieve the above purpose, the application adopts the following technical scheme:

[0010] In a first aspect, the application provides a mixed-frequency ultrasonic delay excitation structure defect detection method.

[0011] A mixed-frequency ultrasonic delay excitation structure defect detection device comprises four piezoelectric ceramic sensors arranged in a rectangle and fixed on the surface of the structure. The four piezoelectric ceramic sensors are in communication connection with a control terminal. The two piezoelectric ceramic sensors on the first side of the rectangle serve as excitation ends, and the two piezoelectric ceramic sensors on the second side of the rectangle serve as receiving ends.

[0012] The first piezoelectric ceramic sensor of the excitation end is used to emit a high-frequency probe wave according to the control signal of the control terminal, and the second piezoelectric ceramic sensor of the excitation end is used to emit a low-frequency pump wave according to the control signal of the control terminal. The high-frequency probe wave has an excitation delay time relative to the low-frequency pump wave.

[0013] When the front end of the high-frequency probe wave meets the end of the excited low-frequency pump wave, the position coordinates are the first coordinates, at which time the high-frequency probe wave and the low-frequency pump wave interact and generate a mixed-frequency acoustic wave. When the end of the high-frequency probe wave meets the front end of the excited low-frequency pump wave, the position coordinates are the second coordinates, at which time the high-frequency probe wave and the low-frequency pump wave are separated from each other and no longer generate a mixed-frequency acoustic wave.

[0014] The control terminal is configured to perform defect detection in a modulation aliasing region between the first coordinate and the second coordinate according to mixed frequency sound waves received by the two piezoelectric ceramic sensors of the receiving terminal.

[0015] In a second aspect, the application provides a structural defect detection method of mixed frequency ultrasonic delay excitation.

[0016] The structural defect detection method of mixed frequency ultrasonic delay excitation utilizes the structural defect detection device of mixed frequency ultrasonic delay excitation in the first aspect of the application, and includes the following processes:

[0017] After the mixed frequency sound waves received by the two piezoelectric ceramic sensors are sequentially subjected to band-pass filtering, EMD decomposition and reconstruction, and spectrum-energy spectrum analysis, modulation sideband parameters are extracted from the time-frequency spectrum, and defect identification parameters are calculated according to the modulation sideband parameters.

[0018] If the defect identification parameter is greater than zero, there is a defect in the modulation aliasing region at the excitation delay time; if the defect identification parameter is less than zero, there is no defect in the modulation aliasing region at the excitation delay time.

[0019] As a further limitation of the second aspect of the application, the defect identification parameter γ is: Wherein, β Rec1 represents the modulation sideband parameter corresponding to the response signal of the low-frequency pump wave, β Rec2 represents the modulation sideband parameter corresponding to the response signal of the high-frequency probe wave.

[0020] As a further limitation of the second aspect of the application, the center point of the first piezoelectric ceramic sensor is taken as the origin, the horizontal line on the rectangle is taken as the X-axis, and the vertical line on the rectangle is taken as the Y-axis, then the first coordinate is (x1, y1) and the second coordinate is (x2, y2).

[0021] If the defect identification parameter is greater than zero, there is a defect between x1 and x2 on the X-axis in the modulation aliasing region at the set delay time.

[0022] As a further limitation of the second aspect of the application, the front end of the high-frequency probe wave meets the end of the excited low-frequency pump wave, and the trajectory is:

[0023] Wherein, d a is the distance between the first piezoelectric ceramic sensor and the second piezoelectric ceramic sensor, the two piezoelectric ceramic sensors on the second side of the rectangle are the third piezoelectric ceramic sensor and the fourth piezoelectric ceramic sensor, the first piezoelectric ceramic sensor and the third piezoelectric ceramic sensor are collinear, d b is the distance between the first piezoelectric ceramic sensor and the third piezoelectric ceramic sensor, and d b1d is the distance between the first piezoelectric ceramic sensor and the meeting position, at this time, d b1 is equal to x1, Δt is the delay excitation time of the high-frequency probe wave, λ L is the wavelength of the low-frequency pump wave, C g_L is the group velocity of the low-frequency pump wave, C g_H is the group velocity of the high-frequency probe wave;

[0024] The end of the high-frequency probe wave meets the front end of the excited low-frequency pump wave, and the trajectory is:

[0025] Wherein, d b1 is the distance between the first piezoelectric ceramic sensor and the meeting position, at this time, d b1 is equal to x2, λ H is the wavelength of the high-frequency probe wave;

[0026] According to the trajectory at the first time, the trajectory at the second time, and the excitation delay time corresponding to the defect identification parameter greater than zero, combined with the sound wave propagation speed, the values of x1 and x2 are obtained.

[0027] In a third aspect, the present application provides a mixed-frequency ultrasonic delay excitation structural defect detection system.

[0028] A mixed-frequency ultrasonic delay excitation structural defect detection system utilizes the mixed-frequency ultrasonic delay excitation structural defect detection device of the first aspect of the present application, and includes the following processes:

[0029] The defect identification parameter calculation unit is configured to: after the mixed-frequency sound waves received by the two piezoelectric ceramic sensors are sequentially subjected to band-pass filtering, EMD decomposition and reconstruction, and frequency-energy spectrum analysis, the modulation sideband parameter is extracted from the time-frequency spectrum, and the defect identification parameter is calculated according to the modulation sideband parameter;

[0030] The damage detection unit is configured to: if the defect identification parameter is greater than zero, there is a defect in the modulation aliasing region at the excitation delay time; if the defect identification parameter is less than zero, there is no defect in the modulation aliasing region at the excitation delay time.

[0031] In a fourth aspect, the present application provides a computer device, which includes: a processor and a computer readable storage medium;

[0032] The processor is adapted to execute the computer program;

[0033] The computer readable storage medium has a computer program stored therein, and the computer program is executed by the processor to realize the mixed-frequency ultrasonic delay excitation structural defect detection method according to the second aspect of the present application.

[0034] In a fifth aspect, the present application provides a computer readable storage medium, which stores a computer program, the computer program being adapted to be loaded and executed by a processor to implement the method for detecting structural defects by mixed-frequency ultrasonic delay excitation according to the second aspect of the present application.

[0035] In a sixth aspect, the present application provides a computer program product, which comprises a computer program, the computer program being executed by a processor to implement the method for detecting structural defects by mixed-frequency ultrasonic delay excitation according to the second aspect of the present application.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] 1. The present application innovatively provides a method and system for detecting structural defects by mixed-frequency ultrasonic delay excitation, which is based on the mixed-frequency excitation mode of low-frequency pump wave and high-frequency probe wave delay excitation, does not require mixed-frequency incident waves on the same axis, can indirectly adjust the ultrasonic aliasing region, and thus realizes large-scale comprehensive scanning of the structure.

[0038] 2. The present application is based on the typical nonlinear acoustic feature of modulation sideband, constructs a mapping model of "excitation delay time △t i defect identification parameter γ", performs damage identification and positioning, can eliminate the influence of system nonlinearity, overcomes the dependence on the healthy reference signal, and has broad engineering application prospects.

[0039] The advantages of the additional aspects of the present application will be partially given in the following description, partially become obvious from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0040] The drawings accompanying the specification of the present application form a part thereof, serve to provide further understanding of the present application, and together with the illustrative embodiments of the present application and their description serve to explain the present application, and do not constitute improper limitations on the present application.

[0041] Fig. 1 is a schematic diagram of the method for detecting structural defects by mixed-frequency ultrasonic delay excitation provided by the embodiment 1 of the present application;

[0042] Fig. 2 is a schematic diagram of the ultrasonic aliasing region based on mixed-frequency ultrasonic delay excitation provided by the embodiment 1 of the present application;

[0043] Fig. 3 is a schematic diagram of the method for detecting structural defects by mixed-frequency ultrasonic delay excitation provided by the embodiment 1 of the present application;

[0044] Fig. 4 is a schematic diagram of an electronic device provided by the embodiment 4 of the present application. DETAILED DESCRIPTION

[0045] The application will be further described below with reference to the drawings and embodiments.

[0046] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0047] The embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0048] Embodiment 1

[0049] The implementation mode proposes a structure defect detection device based on mixed frequency ultrasonic delay excitation, as shown in FIG. 1 and FIG. 2, four piezoelectric ceramic sensors are pasted on the surface of the bonded structure to form a rectangular excitation-sensing network (a piezoelectric ceramic sensor is arranged at each of the four corners of the rectangle) ; wherein the piezoelectric ceramic sensors on the right side (the first piezoelectric ceramic sensor and the second piezoelectric ceramic sensor from top to bottom) are used as excitation ends to excite ultrasonic waves, and the piezoelectric ceramic sensors on the left side (the third piezoelectric ceramic sensor and the fourth piezoelectric ceramic sensor from top to bottom) are used as receiving ends to receive ultrasonic response signals.

[0050] In the implementation mode, for non-collinear mixed frequency detection, the traditional acoustic modulation technology is improved in the way of low-frequency pump wave and high-frequency probe wave delay excitation, that is, the excitation time of the high-frequency probe wave HF excited by Act1 (i.e. the first piezoelectric ceramic sensor) is delayed △t i (i = 1, 2…m), respectively, the corresponding mixed frequency response signals Res1 and Res2 are collected.

[0051] It also includes a control terminal, which is in communication connection with the four piezoelectric ceramic sensors respectively, for controlling the first piezoelectric ceramic sensor to emit the high-frequency probe wave HF, controlling the second piezoelectric ceramic sensor to emit the low-frequency pump wave LF, and for detecting defects in the modulation aliasing region between the first coordinate and the second coordinate according to the mixed frequency acoustic waves received by the two piezoelectric ceramic sensors of the receiving end.

[0052] Embodiment 2

[0053] The implementation mode based on the structure defect detection device based on mixed frequency ultrasonic delay excitation described in embodiment 1 provides a specific structure defect detection method based on mixed frequency ultrasonic delay excitation, including the following processes:

[0054] When t = 0, the low-frequency pump wave LF is excited in the aluminum plate, and the group velocity is C g-L ;

[0055] When t = At i , the high-frequency probe wave HF is excited, and the group velocity is C g-H ;

[0056] Suppose that when t = ti, the front end of the excited high-frequency probe wave HF meets the end of the excited low-frequency pump wave LF, and the coordinates of the meeting position are (xi, yi), at which the two will interact and generate a mixed-frequency acoustic wave. At this time, the motion trajectory of the front end of the high-frequency probe wave H and the motion trajectory of the end of the low-frequency probe wave L are combined to obtain:

[0057] where d a , d b , and d b1 are the distance between Act1 (i.e., the first piezoelectric ceramic sensor) and Act2 (i.e., the second piezoelectric ceramic sensor), the distance between Act1 (i.e., the first piezoelectric ceramic sensor) and Rec1 (i.e., the third piezoelectric ceramic sensor), and the distance between Act1 (i.e., the first piezoelectric ceramic sensor) and the meeting position (at this time, d b1 = xi), At is the delay excitation time of the high-frequency probe wave H, and l L is the wavelength of the low-frequency pump wave L.

[0058] Suppose that when t = t2, the end of the excited high-frequency probe wave H meets the front end of the excited low-frequency pump wave L, and the coordinates of the meeting position are (x2, y2). At this time, the motion trajectory equation of the end of the high-frequency probe wave H and the motion trajectory equation of the front end of the low-frequency pump wave L are combined to obtain:

[0059] where d b1 is the distance between Act1 (i.e., the first piezoelectric ceramic sensor) and the meeting position (at this time, d b1 = x2), and l H is the wavelength of the high-frequency pump wave H. After this time, the high-frequency probe wave H and the low-frequency pump wave L separate from each other because the group velocity of the high-frequency probe wave H is higher than that of the low-frequency pump wave L, and thus there is no mixing area.

[0060] In the process of sequential scanning, as shown in FIG. 3, the i group of mixed-frequency response signals (i.e., Res 1 and Res 2) collected for each group of non-collinear mixing detection are subjected to band-pass filtering, EMD decomposition and reconstruction, and frequency-energy spectrum analysis, and the modulation sideband parameters are extracted in the time-frequency spectrum for calculating the defect identification parameter y:

[0061] where b Rec1 and b Rec2 represent the modulation sideband parameters in the response signals Res1 and Res2, respectively, and their calculation methods are as shown in equation (4):

[0062] wherein A H±nL , A L and A H represent the energy of the sideband, low frequency and high frequency components in the response spectrum of the response signal Res1, respectively, and β Rec1 is calculated when A H±nL , A L and A H represent the energy of the sideband, low frequency and high frequency components in the response spectrum of the response signal Res2, respectively, and β Rec2 is calculated when A H±nL , A L and A H represent the energy of the sideband, low frequency and high frequency components in the response spectrum of the response signal Res2, respectively.

[0063] In the present implementation, according to different excitation delay times, a "excitation delay time Δt i -defect identification parameter γ" mapping model is constructed for each detection path (i.e. within each group of rectangular excitation-sensing sub-networks), and according to the positive or negative of the parameter γ and the change trend, damage can be identified and detected without reference. Specifically, if γ>0, it represents that under the excitation delay time Δt i , there is a defect in the modulation aliasing region; if γ<0, it represents that under the excitation delay time Δt i , there is no defect in the modulation aliasing region.

[0064] In the present implementation, further, the excitation delay time Δt i corresponding to γ>0 is extracted, and combined with the sound wave propagation speed, the fzero function in Matlab software can be used to solve x1 and x2, and the position of the damage in the x-axis direction (i.e. between x1 and x2) can be determined, so as to realize damage positioning.

[0065] Example 3:

[0066] The present implementation based on the structure defect detection device based on mixed frequency ultrasonic delay excitation described in embodiment 1 provides a mixed frequency ultrasonic delay excitation structure defect detection system, which uses the mixed frequency ultrasonic delay excitation structure defect detection device described in the first aspect of the present application, and includes the following processes:

[0067] The defect identification parameter calculation unit is configured to: after the mixed frequency sound waves received by the two piezoelectric ceramic sensors are sequentially subjected to band-pass filtering, EMD decomposition and reconstruction, and spectrum-energy spectrum analysis, the modulation sideband parameter is extracted from the time-frequency spectrum, and the defect identification parameter is calculated according to the modulation sideband parameter;

[0068] The damage detection unit is configured such that: if the defect identification parameter is greater than zero, a defect exists in the modulation aliasing region under the excitation delay time; if the defect identification parameter is less than zero, no defect exists in the modulation aliasing region under the excitation delay time.

[0069] Specifically, in the defect identification parameter calculation unit, bandpass filtering, EMD decomposition and reconstruction, and frequency-energy spectrum analysis are performed on the i sets of mixing response signals (i.e., Res 1 and Res 2) acquired for each set of non-collinear mixing detection. Modulation sideband parameters are extracted from the time spectrum to calculate the defect identification parameter γ. β Rec1 and β Rec2 These represent the modulation sideband parameters in the response signals Res1 and Res2, respectively, and are calculated as follows: Among them, A H±nL A L and A H Representing the energies of the sidebands, low-frequency components, and high-frequency components in the response spectrum, respectively, calculate β. Rec1 At that time, A H±nL A L and A H Calculate β, where β represents the energy of the sideband, low-frequency, and high-frequency components in the response spectrum of the response signal Res1, respectively. Rec2 At that time, A H±nL A L and A H These represent the energy of the sideband, low-frequency, and high-frequency components in the response spectrum of the response signal Res2, respectively.

[0070] Specifically, in the damage detection unit, based on different excitation delay times, the "excitation delay time Δt" is constructed for each detection path (i.e., within each group of rectangular excitation-sensor subnetworks). i - The defect identification parameter γ" mapping model allows for benchmark-free damage identification and detection based on the sign and trend of parameter γ. Specifically, if γ > 0, it represents the excitation delay time Δt. i Below, a defect exists in the modulation aliasing region; if γ < 0, it represents the excitation delay time Δt. i Under these conditions, there are no defects in the modulation aliasing region.

[0071] In this implementation, the excitation delay time Δt corresponding to γ ​​> 0 is further extracted. i By combining the speed of sound wave propagation, we can use the fzero function in Matlab software to solve for x1 and x2, and thus determine the location of the damage in the x-axis direction (i.e., between x1 and x2), thereby achieving damage localization.

[0072] It can be understood that the above-mentioned units can be combined into one or several other units respectively or entirely, or some of the units can be further split into multiple units with smaller functions to achieve the same operation without affecting the implementation of the technical effects of the embodiments of the present application. The above-mentioned units are divided based on logical functions. In actual applications, the functions of one unit can also be implemented by multiple units, or the functions of multiple units can be implemented by one unit. In other embodiments of the present application, the defect detection system can also include other units. In actual applications, these functions can also be assisted by other units, and can be implemented by multiple units in cooperation.

[0073] According to another embodiment of the present application, the system described in the embodiment can be constructed and the defect detection method of the embodiments of the present application can be implemented by running a computer program (including program codes) capable of performing each step involved in the corresponding method described in Embodiment 2 on a general computing device such as a computer including processing elements and storage elements such as a Central Processing Unit (CPU), a Random Access Memory (RAM), a Read Only Memory (ROM), etc., the computer program can be recorded on a computer readable recording medium, loaded into the above-mentioned computing device through the computer readable recording medium, and run therein.

[0074] Embodiment 4:

[0075] As shown in FIG. 4, the present implementation provides an electronic device (which can serve as the control terminal in Embodiment 1), which includes a processor 1001, a communication interface 1002, and a computer readable storage medium 1003, wherein the processor 1001, the communication interface 1002, and the computer readable storage medium 1003 can be connected through a bus or other means.

[0076] The communication interface 1002 is configured to receive and send data, the computer readable storage medium 1003 can be stored in the memory of the electronic device, the computer readable storage medium 1003 is configured to store a computer program, the computer program includes program instructions, and the processor 1001 is configured to execute the program instructions stored in the computer readable storage medium 1003.

[0077] The processor 1001 (or CPU (Central Processing Unit)) is the computing core and control core of the electronic device, which is suitable for implementing one or more instructions, and is particularly suitable for loading and executing one or more instructions to implement a corresponding method flow or a corresponding function.

[0078] The processor 1001 is configured to perform the following process:

[0079] S1: After performing bandpass filtering, EMD decomposition and reconstruction, and spectrum-energy spectrum analysis on the mixed acoustic waves received by the two piezoelectric ceramic sensors, the modulation sideband parameters are extracted from the time spectrum, and the defect identification parameters are calculated based on the modulation sideband parameters.

[0080] S2: If the defect identification parameter is greater than zero, then there is a defect in the modulation aliasing region under the excitation delay time; if the defect identification parameter is less than zero, then there is no defect in the modulation aliasing region under the excitation delay time.

[0081] Specifically, in step S1, bandpass filtering, EMD decomposition and reconstruction, and frequency-energy spectrum analysis are performed on the i sets of mixing response signals (i.e., Res 1 and Res 2) acquired for each set of non-collinear mixing detection. Modulation sideband parameters are extracted from the time spectrum to calculate the defect identification parameter γ. β Rec1 and β Rec2 These represent the modulation sideband parameters in the response signals Res1 and Res2, respectively, and are calculated as follows: Among them, A H±nL A L and A H Representing the energies of the sidebands, low-frequency components, and high-frequency components in the response spectrum, respectively, calculate β. Rec1 At that time, A H±nL A L and A H Calculate β, where β represents the energy of the sideband, low-frequency, and high-frequency components in the response spectrum of the response signal Res1, respectively. Rec2 At that time, A H±nL A L and A H These represent the energy of the sideband, low-frequency, and high-frequency components in the response spectrum of the response signal Res2, respectively.

[0082] Specifically, in step S2, based on different excitation delay times, the "excitation delay time Δt" is constructed for each detection path (i.e., within each group of rectangular excitation-sensing sub-networks). i - The defect identification parameter γ" mapping model allows for benchmark-free damage identification and detection based on the sign and trend of parameter γ. Specifically, if γ > 0, it represents the excitation delay time Δt. i Below, a defect exists in the modulation aliasing region; if γ < 0, it represents the excitation delay time Δt. i Under these conditions, there are no defects in the modulation aliasing region.

[0083] In this implementation, the excitation delay time Δt corresponding to γ ​​> 0 is further extracted. i, combined with the sound wave propagation velocity, the fzero function in Matlab software can be used to solve x1 and x2, so as to determine the position of the damage in the x-axis direction (i.e. between x1 and x2), thereby realizing damage positioning.

[0084] Embodiment 4:

[0085] The present embodiment provides a computer readable storage medium (which can be embedded in the control terminal in embodiment 1), which is a memory device in an electronic device, used to store programs and data. It can be understood that the computer readable storage medium herein can include a built-in storage medium in the electronic device, and of course can also include an extended storage medium supported by the electronic device. The computer readable storage medium provides a storage space which stores the processing system of the electronic device.

[0086] And in the storage space, one or more instructions suitable for being loaded and executed by the processor are also stored, which can be one or more computer programs (including program codes). It should be noted that the computer readable storage medium herein can be a high-speed RAM memory, or a non-volatile memory such as at least one disk memory; optionally, it can also be at least one computer readable storage medium located away from the aforementioned processor.

[0087] In one embodiment, the computer readable storage medium stores one or more instructions; the processor loads and executes the one or more instructions stored in the computer readable storage medium to implement the following process:

[0088] S1: After the mixed frequency sound waves received by the two piezoelectric ceramic sensors are sequentially subjected to band-pass filtering, EMD decomposition and reconstruction, and frequency-energy spectrum analysis, the modulation sideband parameters are extracted from the time-frequency spectrum, and the defect identification parameters are calculated according to the modulation sideband parameters;

[0089] S2: If the defect identification parameter is greater than zero, there is a defect in the modulation aliasing region under the excitation delay time; if the defect identification parameter is less than zero, there is no defect in the modulation aliasing region under the excitation delay time.

[0090] Specifically, in step S1, for each group of non-collinear mixing detection, the i group of mixed frequency response signals (i.e. Res 1 and Res 2) collected are subjected to band-pass filtering, EMD decomposition and reconstruction, and frequency-energy spectrum analysis, and the modulation sideband parameters are extracted from the time-frequency spectrum for calculating the defect identification parameter γ: β Rec1 and β Rec2 respectively represent the modulation sideband parameters in the response signals Res1 and Res2, and the calculation methods are: wherein A H±nL , A L and A H represent the energy of the sideband, low frequency and high frequency components in the response spectrum of the response signal Res1, respectively, and β Rec1 is calculated. H±nL , A L and A H represent the energy of the sideband, low frequency and high frequency components in the response spectrum of the response signal Res2, respectively, and β Rec2 is calculated. H±nL , A L and A H represent the energy of the sideband, low frequency and high frequency components in the response spectrum of the response signal Res2, respectively, and β Rec2 is calculated.

[0091] Specifically, in step S2, a "excitation delay time Δt i -defect identification parameter γ" mapping model of each detection path (i.e. in each group of rectangular excitation-sensing sub-networks) is constructed according to different excitation delay times, and the damage can be identified and detected according to the positive and negative and change trend of the parameter γ. Specifically, if γ>0, it represents that there is a defect in the modulation aliasing region under the excitation delay time Δt i ; if γ<0, it represents that there is no defect in the modulation aliasing region under the excitation delay time Δt i .

[0092] In the present implementation, further, the excitation delay time Δt i corresponding to γ>0 is extracted, and the sound wave propagation speed is combined to solve x1 and x2 by using the fzero function in Matlab software, so as to determine the position of the damage in the x-axis direction (i.e. between x1 and x2), thereby realizing damage positioning.

[0093] Example 5:

[0094] The present implementation provides a computer program product or computer program (which can be embedded into the control terminal in example 1) comprising computer instructions stored in a computer readable storage medium. The processor of the electronic device reads the computer instructions from the computer readable storage medium, and the processor executes the computer instructions to make the electronic device execute the following processes:

[0095] S1: After the mixed frequency sound waves received by the two piezoelectric ceramic sensors are sequentially subjected to band-pass filtering, EMD decomposition and reconstruction, and spectrum-energy spectrum analysis, the modulation sideband parameter is extracted from the time-frequency spectrum, and the defect identification parameter is calculated according to the modulation sideband parameter;

[0096] S2: if the defect identification parameter is greater than zero, then under the excitation delay time, there is a defect in the modulation aliasing region; if the defect identification parameter is less than zero, then under the excitation delay time, there is no defect in the modulation aliasing region.

[0097] Specifically, in step S1, for each group of non-collinear mixing, the i-group mixing response signals (i.e. Res 1 and Res 2) collected are subjected to band-pass filtering, EMD decomposition and reconstruction, and frequency-energy spectrum analysis, and the modulation sideband parameters are extracted in the time-frequency spectrum, which are used to calculate the defect identification parameter γ: β Rec1 and β Rec2 respectively represent the modulation sideband parameters in the response signals Res1 and Res2, and the calculation methods are as follows: Wherein, A H±nL , A L and A H respectively represent the energy of the sideband, low frequency and high frequency components in the response spectrum, and the calculation of β Rec1 is as follows: A H±nL , A L and A H respectively represent the energy of the sideband, low frequency and high frequency components in the response spectrum of the response signal Res1, and the calculation of β Rec2 is as follows: A H±nL , A L and A H respectively represent the energy of the sideband, low frequency and high frequency components in the response spectrum of the response signal Res2.

[0098] Specifically, in step S2, according to different excitation delay times, the "excitation delay time Δt i -defect identification parameter γ" mapping model of each detection path (i.e. in each group of rectangular excitation-sensing sub-network) is constructed, and according to the positive and negative of the parameter γ and the change trend, the damage can be identified and detected without reference. Specifically, if γ>0, it represents that under the excitation delay time Δt i , there is a defect in the modulation aliasing region; if γ<0, it represents that under the excitation delay time Δt i , there is no defect in the modulation aliasing region.

[0099] In the present embodiment, further, the excitation delay time Δt i corresponding to γ>0 is extracted, and combined with the sound wave propagation speed, the fzero function in Matlab software can be used to solve x1 and x2, and the position of the damage in the x-axis direction (i.e. between x1 and x2) can be determined, so as to realize damage positioning.

[0100] Those skilled in the art can be aware that units and algorithm steps of each example described in combination with the embodiments disclosed in the application can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed in hardware or software depends on specific applications and design constraints of the technical solutions. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the application.

[0101] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or part of the embodiments can be implemented in the form of 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 according to the embodiments of the application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. Computer instructions can be stored in or transmitted by a computer-readable storage medium. Computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center through wired (for example, coaxial cable, optical fiber, digital line (DSL)) or wireless (for example, infrared, wireless, microwave, etc.) mode. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data processing device such as a server, data center, etc. containing one or more available media sets. The available media can be magnetic media (for example, floppy disk, hard disk, magnetic tape), optical media (for example, DVD), or semiconductor media (for example, solid state disk (SSD)) and the like.

[0102] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A structure defect detection device based on mixed frequency ultrasonic delay excitation, comprising four piezoelectric ceramic sensors arranged in a rectangle on a structure surface, the four piezoelectric ceramic sensors being in communication with a control terminal, two piezoelectric ceramic sensors on a first side of the rectangle serving as excitation ends, and two piezoelectric ceramic sensors on a second side of the rectangle serving as receiving ends; the first piezoelectric ceramic sensor of the excitation ends is configured to emit a high-frequency probe wave according to a control signal from the control terminal, and the second piezoelectric ceramic sensor of the excitation ends is configured to emit a low-frequency pump wave according to a control signal from the control terminal, the high-frequency probe wave having an excitation delay time relative to the low-frequency pump wave; a first coordinate is obtained when a front end of the high-frequency probe wave meets a tail end of the excited low-frequency pump wave, at which time the high-frequency probe wave and the low-frequency pump wave interact to generate mixed frequency sound waves; a second coordinate is obtained when a tail end of the high-frequency probe wave meets a front end of the excited low-frequency pump wave, at which time the high-frequency probe wave and the low-frequency pump wave separate from each other and no longer generate mixed frequency sound waves; and the control terminal is configured to detect defects in a modulation aliasing region between the first coordinate and the second coordinate based on the mixed frequency sound waves received by the two piezoelectric ceramic sensors of the receiving ends. The structure defect detection device based on mixed frequency ultrasonic delay excitation of claim 1 comprises the following processes: The mixed frequency sound waves received by the two piezoelectric ceramic sensors are sequentially subjected to band-pass filtering, EMD decomposition and reconstruction, and spectrum-energy spectrum analysis, and then modulation sideband parameters are extracted from a time-frequency spectrum based on the mixed frequency sound waves, and a defect identification parameter is calculated based on the modulation sideband parameters; If the defect identification parameter is greater than zero, there is a defect in the modulation aliasing region at the excitation delay time; If the defect identification parameter is less than zero, there is no defect in the modulation aliasing region at the excitation delay time.

2. A method of structural defect detection by mixed-mode ultrasonic delay excitation, characterized in that, 3.The structure defect detection method based on mixed frequency ultrasonic delay excitation of claim 2, wherein 4.The structure defect detection method based on mixed frequency ultrasonic delay excitation of claim 2, wherein Taking a center point of the first piezoelectric ceramic sensor as an origin, a horizontal line on the rectangle as an X-axis, and a vertical line on the rectangle as a Y-axis, the first coordinate is (x1, y1) and the second coordinate is (x2, y2); If the defect identification parameter is greater than zero, there is a defect between x1 and x2 on the X-axis in the modulation aliasing region at the set delay time. 5.The structure defect detection method based on mixed frequency ultrasonic delay excitation of claim 4, wherein The defect recognition parameter γ is: wherein β Rec1 represents the modulation sideband parameter corresponding to the response signal of the low-frequency pump wave Rec2 represents the modulation sideband parameter corresponding to the response signal of the high-frequency probe wave. The values of x1 and x2 are obtained based on the trajectory at the first time, the trajectory at the second time, and the excitation delay time corresponding to the defect identification parameter being greater than zero, in combination with a sound wave propagation speed. The structure defect detection device based on mixed frequency ultrasonic delay excitation of claim 1 comprises the following processes: A defect identification parameter calculation unit is configured to sequentially subject the mixed frequency sound waves received by the two piezoelectric ceramic sensors to band-pass filtering, EMD decomposition and reconstruction, and spectrum-energy spectrum analysis, and then extract modulation sideband parameters from a time-frequency spectrum based on the mixed frequency sound waves, and calculate a defect identification parameter based on the modulation sideband parameters. ​ The front end of the high-frequency probe wave meets the end of the excited low-frequency pump wave, and the trajectory is: wherein d a is the distance between the first piezoelectric ceramic sensor and the second piezoelectric ceramic sensor, the two piezoelectric ceramic sensors of the rectangular second side are respectively the third piezoelectric ceramic sensor and the fourth piezoelectric ceramic sensor, the first piezoelectric ceramic sensor and the third piezoelectric ceramic sensor are collinear, d b is the distance between the first piezoelectric ceramic sensor and the third piezoelectric ceramic sensor, d b1 is the distance between the first piezoelectric ceramic sensor and the meeting position, at this time, d b1 is equal to x1, △t is the delay excitation time of the high-frequency detection wave, λ L is the wavelength of the low-frequency pump wave, C g_L is the group velocity of the low-frequency pump wave; The end of the high-frequency probe wave meets the front end of the excited low-frequency pump wave, and the trajectory is: wherein d b1 is the distance between the first piezoelectric ceramic sensor and the meeting position, at which time d b1 is equal to x2, λ H is the wavelength of the high-frequency detection wave; ​ 6. A mixed-mode ultrasonic delay launch structural defect detection system characterized by, ​ ​ The damage detection unit is configured to modulate the presence of a defect in the aliasing region at the excitation delay time if the defect identification parameter is greater than zero. The damage detection unit is configured to modulate the absence of a defect in the aliasing region at the excitation delay time if the defect identification parameter is less than zero.

7. The mixed frequency ultrasonic delay excitation structural defect detection system of claim 6, wherein: In the defect recognition parameter calculation unit, the defect recognition parameter γ is: wherein β Rec1 represents the modulation sideband parameter corresponding to the response signal of the low-frequency pump wave Rec2 represents the modulation sideband parameter corresponding to the response signal of the high-frequency probe wave 8. A computer device, comprising: comprises: a processor and a computer readable storage medium; a processor adapted to execute a computer program; a computer readable storage medium having stored therein a computer program which, when executed by the processor, implements the mixed frequency ultrasonic delay excitation structural defect detection method of claims 2-5.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program which is adapted to be loaded and executed by the processor to implement the mixed frequency ultrasonic delay excitation structural defect detection method of claims 2-5.

10. A computer program product, characterised in that, The computer program product comprises a computer program which, when executed by the processor, implements the mixed frequency ultrasonic delay excitation structural defect detection method of claims 2-5.

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