In this paper,we theoretically study the Lamb wave in a multilayered piezoelectric semiconductor(PSC)plate,where each layer is an n-type PSC with the symmetry of transverse isotropy.Based on the extended Stroh formali...In this paper,we theoretically study the Lamb wave in a multilayered piezoelectric semiconductor(PSC)plate,where each layer is an n-type PSC with the symmetry of transverse isotropy.Based on the extended Stroh formalism and dual-variable and position(DVP)method,the general solution of the coupled fields for the Lamb wave is derived,and then the dispersion equation is obtained by the application of the boundary conditions.First,the influence of semiconducting properties on the dispersion behavior of the Lamb wave in a single-layer PSC plate is analyzed.Then,the propagation characteristics of the Lamb wave in a sandwich plate are investigated in detail.The numerical results show that the wave speed and attenuation depend on the stacking sequence,layer thickness,and initial carrier density,the Lamb wave can propagate without a cut-off frequency in both the homogeneous and multilayer PSC plates due to the semiconducting properties,and the Lamb wave without attenuation can be achieved by carefully selecting the semiconductor property in the upper and lower layers.These new features could be very helpful as theoretical guidance for the design and performance optimization of PSC devices.展开更多
Ultrasonic Lamb waves undergo complex mode conversion and diffraction at non-penetrating defects, such as plate corrosion and cracks. Lamb wave imaging has a resolution limit due to the guided wave dispersion characte...Ultrasonic Lamb waves undergo complex mode conversion and diffraction at non-penetrating defects, such as plate corrosion and cracks. Lamb wave imaging has a resolution limit due to the guided wave dispersion characteristics and Rayleigh criterion limitations. In this paper, a full convolutional network is designed to segment and reconstruct the received signals, enabling the automatic identification of target modalities. This approach eliminates clutter and mode conversion interference when calculating direct and accompanying acoustic fields in time-domain topological energy(TDTE) imaging.Subsequently, the measured accompanying acoustic field is reversed for adaptive focusing on defects and enhance the imaging quality. To circumvent the limitations of the Rayleigh criterion, the direct acoustic field and the accompanying acoustic field were fused to characterize the pixel distribution in the imaging region, achieving Lamb wave super-resolution imaging. Experimental results indicate that compared to the sign coherence factor-total focusing method(SCF-TFM),the proposed method achieves a 31.41% improvement in lateral resolution and a 29.53% increase in signal-to-noise ratio for single-blind-hole defects. In the case of multiple-blind-hole defects with spacings greater than the Rayleigh criterion resolution limit, it exhibits a 27.23% enhancement in signal-to-noise ratio. On the contrary, when the defect spacings are relatively smaller than the limit, this method has a higher resolution limit than SCF-TFM in super-resolution imaging.展开更多
Due to the complexity and faintness of the detection wave patterns obtained by aircoupled transducers,if it is possible to effectively separate the various modes and obtain nondispersive signals for more accurate dete...Due to the complexity and faintness of the detection wave patterns obtained by aircoupled transducers,if it is possible to effectively separate the various modes and obtain nondispersive signals for more accurate detection and positioning,it will help to improve the accuracy and reliability of air-coupled ultrasonic Lamb wave detection,providing better technical support for the application and development of related fields.Because of the increased complexity of aircoupled signals,there is no definite theoretical formula to describe the mode changes of aircoupled signals,so the method based on blind separation has unique value.To address these challenges,the paper proposes a single-channel blind source separation(SCBSS)method.The effectiveness of this method is evaluated through simulations and experiments,demonstrating favorable separation results and efficient computational speed.This work first conducts an in-depth analysis of the signal characteristics of air-coupled ultrasonic non-destructive testing,and simulates the ultrasonic excitation conditions of air-coupled sensors through finite element software.The study of modal changes and multipath effects caused by the variation of the incidence angle of the ACT signal is carried out,and the situation of the Lamb wave signal excited by ACT at the receiving end is analyzed.By combining ACT with PZT signals,the ultrasonic signals of air-coupled Lamb waves are compared and studied,and their modal purification is carried out.展开更多
A quantitative identification method for in-flight icing has the capability to significantly enhance the safety of aircraft operations.Ultrasonic guided waves have the unique advantage of detecting icing in a relative...A quantitative identification method for in-flight icing has the capability to significantly enhance the safety of aircraft operations.Ultrasonic guided waves have the unique advantage of detecting icing in a relatively large area,but quantitative identification of ice layers is a challenge.In this paper,a quantitative identification method of ice accumulation based on ultrasonic guided waves is proposed.Firstly,a simulation model for the wave dynamics of piezoelectric coupling in three dimensions is established to analyze the propagation characteristics of Lamb waves in a structure consisting of an aluminum plate and an ice layer.The wavelet transform method is utilized to extract the Time of Flight(ToF)or Time of Delay(ToD)of S_(0)/B_(1) mode waves,which serves as a characteristic parameter to precisely determine and assess the level of ice accumulation.Then,an experimental system is developed to evaluate the feasibility of Lamb waves-based icing real-time detection in the presence of spray conditions.Finally,a combination of the Hampel median filter and the moving average filter is developed to analyze ToF/ToD signals.Numerical simulation results reveal a positive correlation between geometric dimensions(length,width,thickness)of the ice layer and ToF/ToD of B1 mode waves,indicating their potential as indicators for quantifying ice accumulation.Experimental results of real-time icing detection indicate that ToF/ToD will reach greater peak values with the growth of the arbitrary-shaped ice layer until saturation to effectively predict the simulation results.This study lays a foundation for the practical application of quantitative icing detection via ultrasonic guided waves.展开更多
Acoustic streaming enabled by a Lamb wave resonator(LWR)is efficient for particle trapping and enrichment in microfluidic channels.However,because Lamb waves combine the features of bulk acoustic waves and surface aco...Acoustic streaming enabled by a Lamb wave resonator(LWR)is efficient for particle trapping and enrichment in microfluidic channels.However,because Lamb waves combine the features of bulk acoustic waves and surface acoustic waves,the resulting acoustic streaming in the LWR occurs in multiple planes,and the particle flow behavior in this acoustofluidic system is largely unknown.Reported here are numerical simulations and laboratory experiments conducted to investigate the boundary conditions for particle motion inside a microvortex induced by an LWR.Upon dynamic capture,the particles’trajectories become orbital paths within an acoustic vortex.The suspended particles encounter two distinct acoustic phenomena,i.e.,the drag force resulting from acoustic streaming and the acoustic radiation force,which exert forces in various directions on the particles.When the acoustic radiation force and the fluid drag force are dominant for large and small particles in a mixed solution,respectively,the large particles reside within the vortex while the small particles remain at its periphery.Conversely,when the acoustic radiation force is dominant for both types of particles,the distribution pattern is reversed.展开更多
A two-step method is proposed for detection and identification of invisible impact damage in composite structure under temperature changes using Lamb waves.First,a statistical outlier analysis is employed to distingui...A two-step method is proposed for detection and identification of invisible impact damage in composite structure under temperature changes using Lamb waves.First,a statistical outlier analysis is employed to distinguish whether the changes of Lamb wave signals are induced by damage within a monitoring area or are only affected by temperature changes.Damage indices are defined after the Lamb wave signals are processed by Fourier transform,and a Monte Carlo procedure is used to obtain the damage threshold value for the damage indices at the undamaged state.If the damage indices in the operation state exceed the threshold value,the presence of damage is determined.Then,a probabilistic damage imaging algorithm displaying probabilities of the presence of damage within the monitoring area is adopted to fuse information collected from multiple actuator-sensor paths to identify the location of damage.Damage indices under damaged state are used to generate the diagnostic image.Experimental study on a stiffened composite panel with random temperature changes is performed to demonstrate the effectiveness of the proposed method.展开更多
Structure health monitoring based on diagnostic Lamb waves has been found to be one of the most promising techniques recently. This paper has a brief review of the new developments on this method including the basic n...Structure health monitoring based on diagnostic Lamb waves has been found to be one of the most promising techniques recently. This paper has a brief review of the new developments on this method including the basic novel of the method, fundamentals and mathematics of Lamb wave propagation, narrowband and wideband Lamb wave excitation methods, optimization of excitation factors and diagnostic Lamb wave interpretation methods.展开更多
Based on Lamb wave analysis of propagation in plate-like structures, a damage detection method is proposed that not only locates the position of the damage accurately but also estimates its size. Similar damage detect...Based on Lamb wave analysis of propagation in plate-like structures, a damage detection method is proposed that not only locates the position of the damage accurately but also estimates its size. Similar damage detection methods focus only on localization giving no quantitative estimation of extent. To improve detection, we propose two predictive circle methods for size estimation. Numerical simulations and experiments were performed for an aluminum plate with a hole. Two PZT configurations of different sizes were designed to excite and detect Lamb waves. From cross-correlation analysis, the damage location and extent can be determined. Results show that the proposed method enables a better quantitative resolution in detection, the size of the inspection area influences the accuracy of damage identification, and the closer is the inspected area to the damage, the more accurate are the results. The method proposed can be developed into a multiple-step detection method for multi-scale analysis with prospective accuracy.展开更多
We propose a nonlinear ultrasonic technique by using the mixed-frequency signals excited Lamb waves to conduct micro-crack detection in thin plate structures.Simulation models of three-dimensional(3D)aluminum plates a...We propose a nonlinear ultrasonic technique by using the mixed-frequency signals excited Lamb waves to conduct micro-crack detection in thin plate structures.Simulation models of three-dimensional(3D)aluminum plates and composite laminates are established by ABAQUS software,where the aluminum plate contains buried crack and composite laminates comprises cohesive element whose thickness is zero to simulate delamination damage.The interactions between the S0 mode Lamb wave and the buried micro-cracks of various dimensions are simulated by using the finite element method.Fourier frequency spectrum analysis is applied to the received time domain signal and fundamental frequency amplitudes,and sum and difference frequencies are extracted and simulated.Simulation results indicate that nonlinear Lamb waves have different sensitivities to various crack sizes.There is a positive correlation among crack length,height,and sum and difference frequency amplitudes for an aluminum plate,with both amplitudes decreasing as crack thickness increased,i.e.,nonlinear effect weakens as the micro-crack becomes thicker.The amplitudes of sum and difference frequency are positively correlated with the length and width of the zero-thickness cohesive element in the composite laminates.Furthermore,amplitude ratio change is investigated and it can be used as an effective tool to detect inner defects in thin 3D plates.展开更多
This paper investigates the influence of crack orientation on damage quantification using Lamb wave in plate structures. Finite element simulation is performed to acquire Lamb wave signal responses for different confi...This paper investigates the influence of crack orientation on damage quantification using Lamb wave in plate structures. Finite element simulation is performed to acquire Lamb wave signal responses for different configurations of crack orientations and crack lengths. Two Lamb wave features, namely the normalized amplitude and the phase change, are used as damage sensitive features to develop a crack size quantification model. A hypothesis based on the geometrical influence on signal features is proposed, and the crack size quantification model incorporating the orientation angle is established using the hypothesis. An index of Probability of Reliable Quantification(PRQ) is proposed to evaluate the performance of the model. The index can be used to determine the sizing risk in terms of probabilities. A realistic aluminum plate is used to obtain the experimental data using piezoelectric(PZT) wafer-type sensors around a center through crack. The experimental data are used to validate the overall method. Results indicate that the proposed model can yield reliable results for size quantification of inclined cracks.展开更多
In this paper, we investigate the diffraction tomography for quantitative imaging damages of partly through-thickness holes with various shapes in isotropic plates by using converted and non-converted scattered Lamb w...In this paper, we investigate the diffraction tomography for quantitative imaging damages of partly through-thickness holes with various shapes in isotropic plates by using converted and non-converted scattered Lamb waves generated nu- merically. Finite element simulations are carried out to provide the scattered wave data. The validity of the finite element model is confirmed by the comparison of scattering directivity pattern （SDP） of circle blind hole damage between the finite element simulations and the analytical results. The imaging method is based on a theoretical relation between the one-dimensional （1D） Fourier transform of the scattered projection and two-dimensional （2D） spatial Fourier transform of the scattering object. A quantitative image of the damage is obtained by carrying out the 2D inverse Fourier transform of the scattering object. The proposed approach employs a circle transducer network containing forward and backward projections, which lead to so-called transmission mode （TMDT） and reflection mode diffraction tomography （RMDT）, respectively. The reconstructed results of the two projections for a non-converted SO scattered mode are investigated to illuminate the influence of the scattering field data. The results show that Lamb wave diffraction tomography using the combination of TMDT and RMDT improves the imaging effect compared with by using only the TMDT or RMDT. The scattered data of the converted A0 mode are also used to assess the performance of the diffraction tomography method. It is found that the circle and elliptical shaped damages can still be reasonably identified from the reconstructed images while the reconstructed results of other complex shaped damages like crisscross rectangles and racecourse are relatively poor.展开更多
A fully non-contact experimental platform for ultrasonic Lamb wave damage detection was constructed,where laser exciting and the scanning laser Doppler vibrometer were used to realize the high-resolution pickup of the...A fully non-contact experimental platform for ultrasonic Lamb wave damage detection was constructed,where laser exciting and the scanning laser Doppler vibrometer were used to realize the high-resolution pickup of the Lamb wave field in the structure,which has overcome the disadvantages of low spatial resolution caused by the conventional contact Lamb wave transducer.In order to suppress the dispersion effect of broadband laser-ultrasonic signal,we proposed time-domain filtering in multi-band method based on wavelet analysis to decompose the broadband signal into multiple narrowband ones and separate the scattering signals effectively without reference signal.On this basis,the total focusing method(TFM)was used for damage imaging.However,when the traditional TFM was applied to image based on ultrasonic Lamb wave,the inherent dispersion characteristic of ultrasonic Lamb wave could lead to the miscalculation of time delay,thus reducing the imaging precision.Therefore,the frequency-domain TFM was developed by applying phase delay in the frequency domain.The logical AND was introduced to synthesize the damage imaging results of multiple narrowband signals to obtain high-precision damage imaging.Our study has shown that the method of time-domain filtering in multi-band combining with frequency-domain TFM can realize non-contact and accurate damage detection in isotropic plate structures,and it is a potential effective method for application in engineering practice.展开更多
In this paper, we investigate a method of selectively enhancing the single mode signal of a Lamb wave by using a meander-coil electromagnetic acoustic transducer （EMAT） with a new magnetic configuration. We use the ...In this paper, we investigate a method of selectively enhancing the single mode signal of a Lamb wave by using a meander-coil electromagnetic acoustic transducer （EMAT） with a new magnetic configuration. We use the Lamb antisym- metric （A0） mode and symmetric （SO） mode as an example for analysis. The analytical expression of the magnitude of the spatial Fourier transform of the Lorentz force generated by different meander coils is used to determine the optimal driving frequency for single mode generation. The numerical calculation is used to characterize the new magnetic configuration and the conventional EMAT magnet. Experimental examinations of each meander coil in combination with the conventional and new magnetic configuration show that the Lamb wave signal can be selectively enhanced by choosing the appropriate driving frequency and coil parameters through using the improved meander-coil EMAT.展开更多
In this paper,three-dimensional finite-element modeling is conducted to investigate the nonlinear interactions between Lamb waves and microcracks.The simulation research focuses on the influence of microcrack orientat...In this paper,three-dimensional finite-element modeling is conducted to investigate the nonlinear interactions between Lamb waves and microcracks.The simulation research focuses on the influence of microcrack orientation on the propagation direction of generated sum-frequency Lamb waves.The simulation results show that the resonant conditions based on classical nonlinear theory are valid for such interactions,leading to the generation of transmitted and reflected sum-frequency SO waves(SFSWs).Moreover,the propagation directions of these two SFSWs exhibit different trends with respect to the orientations of microcracks.The transmitted SFSW can be used to detect microcracks,whereas the reflected one can be used to measure their orientations.展开更多
The physical process of cumulative second-harmonic generation of Lamb waves propagating in a two-layered solid plate is presented by using the second-order perturbation and the technique of nonlinear reflection of aco...The physical process of cumulative second-harmonic generation of Lamb waves propagating in a two-layered solid plate is presented by using the second-order perturbation and the technique of nonlinear reflection of acoustic waves at an interface. In general, the cumulative second-harmonic generation of a dispersive guided wave propagation does not occur. However, the present paper shows that the second-harmonic of Lamb wave propagation arising from the nonlinear interaction of the partial bulk acoustic waves and the restriction of the three boundaries of the solid plates does have a cumulative growth effect if some conditions are satisfied. Through boundary condition and initial condition of excitation, the analytical expression of cumulative second-harmonic of Lamb waves propagation is determined. Numerical results show the cumulative effect of Lamb waves on second-harmonic field patterns.展开更多
The influences of phase and group velocity matching on cumulative second harmonic generation of Lamb waves are investigated in numerical perspective. Finite element simulations of nonlinear Lamb wave propagation are p...The influences of phase and group velocity matching on cumulative second harmonic generation of Lamb waves are investigated in numerical perspective. Finite element simulations of nonlinear Lamb wave propagation are performed for Lamb wave mode pairs with exact and approximate phase velocity matching, with and without group velocity matching, respectively. The evolution of time-domain second harmonic Lamb waves is analyzed with the propagation distance. The amplitudes of primary and second harmonic waves are calculated to characterize the acoustic nonlinearity. The results verify that phase velocity matching is necessary for generation of the cumulative second harmonic Lamb wave in numerical perspective, while group velocity matching is demonstrated to not be a necessary condition.展开更多
Within the second-order perturbation approximation, this paper investigates the physical process of generation of the time-domain second harmonic by a primary Lamb wave waveform in an elastic plate. The present work i...Within the second-order perturbation approximation, this paper investigates the physical process of generation of the time-domain second harmonic by a primary Lamb wave waveform in an elastic plate. The present work is performed based on the preconditions that the phase velocity matching is satisfied and that the transfer of energy from the primary Lamb wave to the double frequency Lamb wave is not zero. It investigates the influences of the difference between the group velocities of the primary Lamb wave and the double frequency Lamb wave, the propagation distance and the duration of the primary Lamb wave waveform on the envelope shape of the time-domain second harmonic. It finds that the maximum magnitude of the envelope of the second-harmonic waveform can grow within some propagation distance even if the condition of group velocity matching is not satisfied. Our analyses also indicate that the maximum magnitude of the envelope of the second-harmonic waveform is kept constant beyond a specific propagation distance. Furthermore, it concludes that the integration amplitude of the time-domain second-harmonic waveform always grows with propagation distance within the second-order perturbation. The present research yields new physical insight not previously available into the effect of generation of the time-domain second harmonic by propagation of a primary Lamb wave waveform.展开更多
Harmonic nonlinear ultrasound can offer high sensitivity for residual stress measurements;however,it cannot be used for local stress measurements at a point in space and exhibits nonlinear distortions in the experimen...Harmonic nonlinear ultrasound can offer high sensitivity for residual stress measurements;however,it cannot be used for local stress measurements at a point in space and exhibits nonlinear distortions in the experimental system.This paper presents a feasibility study on the measurement of residual stress in a metal plate using a nonlinear Lamb wave-mixing technique.The resonant conditions for two Lamb waves to generate a mixing frequency wave are obtained via theoretical analysis.Finite element simulations are performed to investigate the nonlinear interactions between the two Lamb waves.Results show that two incident A0 waves interact in regions of material nonlinearity and generate a rightward S0 wave at the sum frequency.Residual stress measurement experiments are conducted on steel plate specimens using the collinear Lamb wave-mixing technique.By setting different delays for two transmitters,the generated sum-frequency component at different spatial locations is measured.Experimental results show that the spatial distribution of the amplitude of the sum-frequency component agrees well with the spatial distribution of the residual stress measured using X-rays.The proposed collinear Lamb wave-mixing method is effective for measuring the distribution of residual stress in metal plates.展开更多
A promising tool to detect micro-cracks in plate-like structures is used for generating higher harmonic Lamb waves.In this paper,a method combining nonlinear S0 mode Lamb waves with time reversal to locate micro-crack...A promising tool to detect micro-cracks in plate-like structures is used for generating higher harmonic Lamb waves.In this paper,a method combining nonlinear S0 mode Lamb waves with time reversal to locate micro-cracks is presented and verified by numerical simulations.Two different models,the contact acoustic nonlinearity(CAN)model and the Preisach-Mayergoyz(PM)model,are used to simulate a localized damage in a thin plate.Pulse inversion method is employed to extract the second and fourth harmonics from the received signal.Time reversal is performed to compensate the dispersion of S0 mode Lamb waves.Consequently,the higher harmonics generated from the damaged area can be refocused on their source.By investigating the spatial distribution of harmonic wave packets,the location of micro-cracks will be revealed.The numerical simulations indicate that this method gives accurate locations of the damaged area in a plate.Furthermore,the PM model is proved to be a suitable model to simulate the micro-cracks in plates for generation of higher harmonics.展开更多
A novel Lamb wave frequency-mixing technique is proposed for locating microcracks in a thin plate,which does not require the resonance condition of Lamb wave mixing and can accurately locate the microcracks through on...A novel Lamb wave frequency-mixing technique is proposed for locating microcracks in a thin plate,which does not require the resonance condition of Lamb wave mixing and can accurately locate the microcracks through only one-time sensing.Based on the bilinear stress-strain constitutive model,a two-dimensional finite element(FE)model is built to investigate the frequency-mixing response induced by the interaction between two primary Lamb waves and a microcrack.When two primary Lamb waves of A0 and S0 modes with different frequencies excited on the same side of the plate simultaneously impinge on the examined microcrack,under the modulation of the contact acoustic nonlinearity,the microcrack itself can be deemed as the secondary sound source and it will radiate the Lamb waves of new combined frequencies.Based on the time of flight of the generated A0 mode at difference frequency,an indicator named normalized amplitude index(NAI)is defined to directly locate the multi-microcracks in the given plate.It is found that the number and location of the microcracks can be intuitively visualized by using the NAI based frequency-mixing technique.It is also demonstrated that the proposed frequency mixing technique is a promising approach for the microcrack localization.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.U21A20430 and 12302202)the Hebei Natural Science Foundation of China(No.A2023210040)+1 种基金the Science and Technology Project of Hebei Education Department of China(No.BJ2025005)the Hebei Provincial Department of Human Resources and Social Security of China(No.C20220324)。
文摘In this paper,we theoretically study the Lamb wave in a multilayered piezoelectric semiconductor(PSC)plate,where each layer is an n-type PSC with the symmetry of transverse isotropy.Based on the extended Stroh formalism and dual-variable and position(DVP)method,the general solution of the coupled fields for the Lamb wave is derived,and then the dispersion equation is obtained by the application of the boundary conditions.First,the influence of semiconducting properties on the dispersion behavior of the Lamb wave in a single-layer PSC plate is analyzed.Then,the propagation characteristics of the Lamb wave in a sandwich plate are investigated in detail.The numerical results show that the wave speed and attenuation depend on the stacking sequence,layer thickness,and initial carrier density,the Lamb wave can propagate without a cut-off frequency in both the homogeneous and multilayer PSC plates due to the semiconducting properties,and the Lamb wave without attenuation can be achieved by carefully selecting the semiconductor property in the upper and lower layers.These new features could be very helpful as theoretical guidance for the design and performance optimization of PSC devices.
基金Project supported by the National Natural Science Foundation of China (Grant No. 12174085)the Key Research and Development Project of Changzhou, Jiangsu Province, China (Grant No. CE20235054)the Postgraduate Research and Practice Innovation Program of Jiangsu Province, China (Grant No. KYCX24 0833)。
文摘Ultrasonic Lamb waves undergo complex mode conversion and diffraction at non-penetrating defects, such as plate corrosion and cracks. Lamb wave imaging has a resolution limit due to the guided wave dispersion characteristics and Rayleigh criterion limitations. In this paper, a full convolutional network is designed to segment and reconstruct the received signals, enabling the automatic identification of target modalities. This approach eliminates clutter and mode conversion interference when calculating direct and accompanying acoustic fields in time-domain topological energy(TDTE) imaging.Subsequently, the measured accompanying acoustic field is reversed for adaptive focusing on defects and enhance the imaging quality. To circumvent the limitations of the Rayleigh criterion, the direct acoustic field and the accompanying acoustic field were fused to characterize the pixel distribution in the imaging region, achieving Lamb wave super-resolution imaging. Experimental results indicate that compared to the sign coherence factor-total focusing method(SCF-TFM),the proposed method achieves a 31.41% improvement in lateral resolution and a 29.53% increase in signal-to-noise ratio for single-blind-hole defects. In the case of multiple-blind-hole defects with spacings greater than the Rayleigh criterion resolution limit, it exhibits a 27.23% enhancement in signal-to-noise ratio. On the contrary, when the defect spacings are relatively smaller than the limit, this method has a higher resolution limit than SCF-TFM in super-resolution imaging.
基金Supported by the National Natural Science Foundation of China(Nos.92360306,52222504 and 52241502).
文摘Due to the complexity and faintness of the detection wave patterns obtained by aircoupled transducers,if it is possible to effectively separate the various modes and obtain nondispersive signals for more accurate detection and positioning,it will help to improve the accuracy and reliability of air-coupled ultrasonic Lamb wave detection,providing better technical support for the application and development of related fields.Because of the increased complexity of aircoupled signals,there is no definite theoretical formula to describe the mode changes of aircoupled signals,so the method based on blind separation has unique value.To address these challenges,the paper proposes a single-channel blind source separation(SCBSS)method.The effectiveness of this method is evaluated through simulations and experiments,demonstrating favorable separation results and efficient computational speed.This work first conducts an in-depth analysis of the signal characteristics of air-coupled ultrasonic non-destructive testing,and simulates the ultrasonic excitation conditions of air-coupled sensors through finite element software.The study of modal changes and multipath effects caused by the variation of the incidence angle of the ACT signal is carried out,and the situation of the Lamb wave signal excited by ACT at the receiving end is analyzed.By combining ACT with PZT signals,the ultrasonic signals of air-coupled Lamb waves are compared and studied,and their modal purification is carried out.
基金supported by the National Science and Technology Major Project,China(No.J2019-III-0017).
文摘A quantitative identification method for in-flight icing has the capability to significantly enhance the safety of aircraft operations.Ultrasonic guided waves have the unique advantage of detecting icing in a relatively large area,but quantitative identification of ice layers is a challenge.In this paper,a quantitative identification method of ice accumulation based on ultrasonic guided waves is proposed.Firstly,a simulation model for the wave dynamics of piezoelectric coupling in three dimensions is established to analyze the propagation characteristics of Lamb waves in a structure consisting of an aluminum plate and an ice layer.The wavelet transform method is utilized to extract the Time of Flight(ToF)or Time of Delay(ToD)of S_(0)/B_(1) mode waves,which serves as a characteristic parameter to precisely determine and assess the level of ice accumulation.Then,an experimental system is developed to evaluate the feasibility of Lamb waves-based icing real-time detection in the presence of spray conditions.Finally,a combination of the Hampel median filter and the moving average filter is developed to analyze ToF/ToD signals.Numerical simulation results reveal a positive correlation between geometric dimensions(length,width,thickness)of the ice layer and ToF/ToD of B1 mode waves,indicating their potential as indicators for quantifying ice accumulation.Experimental results of real-time icing detection indicate that ToF/ToD will reach greater peak values with the growth of the arbitrary-shaped ice layer until saturation to effectively predict the simulation results.This study lays a foundation for the practical application of quantitative icing detection via ultrasonic guided waves.
基金support of the National Natural Science Foundation of China (Grant No.62174119)the 111 Project (Grant No.B07014)the Foundation for Talent Scientists of Nanchang Institute for Microtechnology of Tianjin University.
文摘Acoustic streaming enabled by a Lamb wave resonator(LWR)is efficient for particle trapping and enrichment in microfluidic channels.However,because Lamb waves combine the features of bulk acoustic waves and surface acoustic waves,the resulting acoustic streaming in the LWR occurs in multiple planes,and the particle flow behavior in this acoustofluidic system is largely unknown.Reported here are numerical simulations and laboratory experiments conducted to investigate the boundary conditions for particle motion inside a microvortex induced by an LWR.Upon dynamic capture,the particles’trajectories become orbital paths within an acoustic vortex.The suspended particles encounter two distinct acoustic phenomena,i.e.,the drag force resulting from acoustic streaming and the acoustic radiation force,which exert forces in various directions on the particles.When the acoustic radiation force and the fluid drag force are dominant for large and small particles in a mixed solution,respectively,the large particles reside within the vortex while the small particles remain at its periphery.Conversely,when the acoustic radiation force is dominant for both types of particles,the distribution pattern is reversed.
基金Supported by the Aeronautical Science Foundation of China(2008ZA52012)the Six Kinds of Excellent Talent Project in Jiangsu Province of China(2010JZ004)the Research Foundation of Nanjing University of Aeronautics and Astronautics(NS2010027)~~
文摘A two-step method is proposed for detection and identification of invisible impact damage in composite structure under temperature changes using Lamb waves.First,a statistical outlier analysis is employed to distinguish whether the changes of Lamb wave signals are induced by damage within a monitoring area or are only affected by temperature changes.Damage indices are defined after the Lamb wave signals are processed by Fourier transform,and a Monte Carlo procedure is used to obtain the damage threshold value for the damage indices at the undamaged state.If the damage indices in the operation state exceed the threshold value,the presence of damage is determined.Then,a probabilistic damage imaging algorithm displaying probabilities of the presence of damage within the monitoring area is adopted to fuse information collected from multiple actuator-sensor paths to identify the location of damage.Damage indices under damaged state are used to generate the diagnostic image.Experimental study on a stiffened composite panel with random temperature changes is performed to demonstrate the effectiveness of the proposed method.
基金The authors acknowledge the financial supports from the National Natural Science Foundation of China under grant No.90305005,50135030
文摘Structure health monitoring based on diagnostic Lamb waves has been found to be one of the most promising techniques recently. This paper has a brief review of the new developments on this method including the basic novel of the method, fundamentals and mathematics of Lamb wave propagation, narrowband and wideband Lamb wave excitation methods, optimization of excitation factors and diagnostic Lamb wave interpretation methods.
基金Project supported by the National Natural Science Foundation of China(Nos.11172003 and 11521202)
文摘Based on Lamb wave analysis of propagation in plate-like structures, a damage detection method is proposed that not only locates the position of the damage accurately but also estimates its size. Similar damage detection methods focus only on localization giving no quantitative estimation of extent. To improve detection, we propose two predictive circle methods for size estimation. Numerical simulations and experiments were performed for an aluminum plate with a hole. Two PZT configurations of different sizes were designed to excite and detect Lamb waves. From cross-correlation analysis, the damage location and extent can be determined. Results show that the proposed method enables a better quantitative resolution in detection, the size of the inspection area influences the accuracy of damage identification, and the closer is the inspected area to the damage, the more accurate are the results. The method proposed can be developed into a multiple-step detection method for multi-scale analysis with prospective accuracy.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61571222,61602235,and 11474160)the Six Talent Peaks Project of Jiangsu Province,China
文摘We propose a nonlinear ultrasonic technique by using the mixed-frequency signals excited Lamb waves to conduct micro-crack detection in thin plate structures.Simulation models of three-dimensional(3D)aluminum plates and composite laminates are established by ABAQUS software,where the aluminum plate contains buried crack and composite laminates comprises cohesive element whose thickness is zero to simulate delamination damage.The interactions between the S0 mode Lamb wave and the buried micro-cracks of various dimensions are simulated by using the finite element method.Fourier frequency spectrum analysis is applied to the received time domain signal and fundamental frequency amplitudes,and sum and difference frequencies are extracted and simulated.Simulation results indicate that nonlinear Lamb waves have different sensitivities to various crack sizes.There is a positive correlation among crack length,height,and sum and difference frequency amplitudes for an aluminum plate,with both amplitudes decreasing as crack thickness increased,i.e.,nonlinear effect weakens as the micro-crack becomes thicker.The amplitudes of sum and difference frequency are positively correlated with the length and width of the zero-thickness cohesive element in the composite laminates.Furthermore,amplitude ratio change is investigated and it can be used as an effective tool to detect inner defects in thin 3D plates.
基金supported by Science Challenge Project of China (No. TZ2018007)National Natural Science Foundation of China (Nos. 11872088 and51975546)。
文摘This paper investigates the influence of crack orientation on damage quantification using Lamb wave in plate structures. Finite element simulation is performed to acquire Lamb wave signal responses for different configurations of crack orientations and crack lengths. Two Lamb wave features, namely the normalized amplitude and the phase change, are used as damage sensitive features to develop a crack size quantification model. A hypothesis based on the geometrical influence on signal features is proposed, and the crack size quantification model incorporating the orientation angle is established using the hypothesis. An index of Probability of Reliable Quantification(PRQ) is proposed to evaluate the performance of the model. The index can be used to determine the sizing risk in terms of probabilities. A realistic aluminum plate is used to obtain the experimental data using piezoelectric(PZT) wafer-type sensors around a center through crack. The experimental data are used to validate the overall method. Results indicate that the proposed model can yield reliable results for size quantification of inclined cracks.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474195,11274226,11674214,and 51478258)
文摘In this paper, we investigate the diffraction tomography for quantitative imaging damages of partly through-thickness holes with various shapes in isotropic plates by using converted and non-converted scattered Lamb waves generated nu- merically. Finite element simulations are carried out to provide the scattered wave data. The validity of the finite element model is confirmed by the comparison of scattering directivity pattern （SDP） of circle blind hole damage between the finite element simulations and the analytical results. The imaging method is based on a theoretical relation between the one-dimensional （1D） Fourier transform of the scattered projection and two-dimensional （2D） spatial Fourier transform of the scattering object. A quantitative image of the damage is obtained by carrying out the 2D inverse Fourier transform of the scattering object. The proposed approach employs a circle transducer network containing forward and backward projections, which lead to so-called transmission mode （TMDT） and reflection mode diffraction tomography （RMDT）, respectively. The reconstructed results of the two projections for a non-converted SO scattered mode are investigated to illuminate the influence of the scattering field data. The results show that Lamb wave diffraction tomography using the combination of TMDT and RMDT improves the imaging effect compared with by using only the TMDT or RMDT. The scattered data of the converted A0 mode are also used to assess the performance of the diffraction tomography method. It is found that the circle and elliptical shaped damages can still be reasonably identified from the reconstructed images while the reconstructed results of other complex shaped damages like crisscross rectangles and racecourse are relatively poor.
基金This work is supported by the National Science Foundation of China(NSFC)with agreement No.11520101001.This paper continues to study on the basis of the work of Chen Li,Fan Min and Zhou Lei.thank you!I also would like to thank my mentor Professor Luo Ying for his guidance and help.
文摘A fully non-contact experimental platform for ultrasonic Lamb wave damage detection was constructed,where laser exciting and the scanning laser Doppler vibrometer were used to realize the high-resolution pickup of the Lamb wave field in the structure,which has overcome the disadvantages of low spatial resolution caused by the conventional contact Lamb wave transducer.In order to suppress the dispersion effect of broadband laser-ultrasonic signal,we proposed time-domain filtering in multi-band method based on wavelet analysis to decompose the broadband signal into multiple narrowband ones and separate the scattering signals effectively without reference signal.On this basis,the total focusing method(TFM)was used for damage imaging.However,when the traditional TFM was applied to image based on ultrasonic Lamb wave,the inherent dispersion characteristic of ultrasonic Lamb wave could lead to the miscalculation of time delay,thus reducing the imaging precision.Therefore,the frequency-domain TFM was developed by applying phase delay in the frequency domain.The logical AND was introduced to synthesize the damage imaging results of multiple narrowband signals to obtain high-precision damage imaging.Our study has shown that the method of time-domain filtering in multi-band combining with frequency-domain TFM can realize non-contact and accurate damage detection in isotropic plate structures,and it is a potential effective method for application in engineering practice.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51507171 and 51577184)
文摘In this paper, we investigate a method of selectively enhancing the single mode signal of a Lamb wave by using a meander-coil electromagnetic acoustic transducer （EMAT） with a new magnetic configuration. We use the Lamb antisym- metric （A0） mode and symmetric （SO） mode as an example for analysis. The analytical expression of the magnitude of the spatial Fourier transform of the Lorentz force generated by different meander coils is used to determine the optimal driving frequency for single mode generation. The numerical calculation is used to characterize the new magnetic configuration and the conventional EMAT magnet. Experimental examinations of each meander coil in combination with the conventional and new magnetic configuration show that the Lamb wave signal can be selectively enhanced by choosing the appropriate driving frequency and coil parameters through using the improved meander-coil EMAT.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFF0203002)National Natural Science Foundation of China(Grant Nos.11572010,11572011).
文摘In this paper,three-dimensional finite-element modeling is conducted to investigate the nonlinear interactions between Lamb waves and microcracks.The simulation research focuses on the influence of microcrack orientation on the propagation direction of generated sum-frequency Lamb waves.The simulation results show that the resonant conditions based on classical nonlinear theory are valid for such interactions,leading to the generation of transmitted and reflected sum-frequency SO waves(SFSWs).Moreover,the propagation directions of these two SFSWs exhibit different trends with respect to the orientations of microcracks.The transmitted SFSW can be used to detect microcracks,whereas the reflected one can be used to measure their orientations.
基金Project supported by the Shanghai Leading Academic Discipline Project, China (Grant No B503)
文摘The physical process of cumulative second-harmonic generation of Lamb waves propagating in a two-layered solid plate is presented by using the second-order perturbation and the technique of nonlinear reflection of acoustic waves at an interface. In general, the cumulative second-harmonic generation of a dispersive guided wave propagation does not occur. However, the present paper shows that the second-harmonic of Lamb wave propagation arising from the nonlinear interaction of the partial bulk acoustic waves and the restriction of the three boundaries of the solid plates does have a cumulative growth effect if some conditions are satisfied. Through boundary condition and initial condition of excitation, the analytical expression of cumulative second-harmonic of Lamb waves propagation is determined. Numerical results show the cumulative effect of Lamb waves on second-harmonic field patterns.
基金Supported by the National Natural Science Foundation of China under Grant Nos 51325504,11474093,11622430 and 11474361the National Key Research and Development Program of China(2016YFC0801903-02)the Fundamental Research Funds for the Central Universities
文摘The influences of phase and group velocity matching on cumulative second harmonic generation of Lamb waves are investigated in numerical perspective. Finite element simulations of nonlinear Lamb wave propagation are performed for Lamb wave mode pairs with exact and approximate phase velocity matching, with and without group velocity matching, respectively. The evolution of time-domain second harmonic Lamb waves is analyzed with the propagation distance. The amplitudes of primary and second harmonic waves are calculated to characterize the acoustic nonlinearity. The results verify that phase velocity matching is necessary for generation of the cumulative second harmonic Lamb wave in numerical perspective, while group velocity matching is demonstrated to not be a necessary condition.
基金Project supported by the National Natural Science Foundation of China (Grant No 10974256)
文摘Within the second-order perturbation approximation, this paper investigates the physical process of generation of the time-domain second harmonic by a primary Lamb wave waveform in an elastic plate. The present work is performed based on the preconditions that the phase velocity matching is satisfied and that the transfer of energy from the primary Lamb wave to the double frequency Lamb wave is not zero. It investigates the influences of the difference between the group velocities of the primary Lamb wave and the double frequency Lamb wave, the propagation distance and the duration of the primary Lamb wave waveform on the envelope shape of the time-domain second harmonic. It finds that the maximum magnitude of the envelope of the second-harmonic waveform can grow within some propagation distance even if the condition of group velocity matching is not satisfied. Our analyses also indicate that the maximum magnitude of the envelope of the second-harmonic waveform is kept constant beyond a specific propagation distance. Furthermore, it concludes that the integration amplitude of the time-domain second-harmonic waveform always grows with propagation distance within the second-order perturbation. The present research yields new physical insight not previously available into the effect of generation of the time-domain second harmonic by propagation of a primary Lamb wave waveform.
基金National Natural Science Foundation of China(Grant Nos.11972053,12274012)。
文摘Harmonic nonlinear ultrasound can offer high sensitivity for residual stress measurements;however,it cannot be used for local stress measurements at a point in space and exhibits nonlinear distortions in the experimental system.This paper presents a feasibility study on the measurement of residual stress in a metal plate using a nonlinear Lamb wave-mixing technique.The resonant conditions for two Lamb waves to generate a mixing frequency wave are obtained via theoretical analysis.Finite element simulations are performed to investigate the nonlinear interactions between the two Lamb waves.Results show that two incident A0 waves interact in regions of material nonlinearity and generate a rightward S0 wave at the sum frequency.Residual stress measurement experiments are conducted on steel plate specimens using the collinear Lamb wave-mixing technique.By setting different delays for two transmitters,the generated sum-frequency component at different spatial locations is measured.Experimental results show that the spatial distribution of the amplitude of the sum-frequency component agrees well with the spatial distribution of the residual stress measured using X-rays.The proposed collinear Lamb wave-mixing method is effective for measuring the distribution of residual stress in metal plates.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFF0203000)the State Key Program of the National Natural Science Foundation of China(Grant No.11834008)+3 种基金the National Natural Science Foundation of China(Grant No.11774167)the Fund from the State Key Laboratory of Acoustics,Chinese Academy of Sciences(Grant No.SKLA201809)the Science Fund from the Key Laboratory of Underwater Acoustic Environment,Chinese Academy of Sciences(Grant No.SSHJ-KFKT-1701)the Natural Science Fund for AQSIQ Technology Research and Development Program,China(Grant No.2017QK125).
文摘A promising tool to detect micro-cracks in plate-like structures is used for generating higher harmonic Lamb waves.In this paper,a method combining nonlinear S0 mode Lamb waves with time reversal to locate micro-cracks is presented and verified by numerical simulations.Two different models,the contact acoustic nonlinearity(CAN)model and the Preisach-Mayergoyz(PM)model,are used to simulate a localized damage in a thin plate.Pulse inversion method is employed to extract the second and fourth harmonics from the received signal.Time reversal is performed to compensate the dispersion of S0 mode Lamb waves.Consequently,the higher harmonics generated from the damaged area can be refocused on their source.By investigating the spatial distribution of harmonic wave packets,the location of micro-cracks will be revealed.The numerical simulations indicate that this method gives accurate locations of the damaged area in a plate.Furthermore,the PM model is proved to be a suitable model to simulate the micro-cracks in plates for generation of higher harmonics.
基金the National Natural Science Foundation of China(Grant Nos.12074050,52005058,11834008,and 11632004)the China Postdoctoral Science Foundation(Grant No.2020M673119)the Fund for Innovative Research Groups of Natural Science Foundation of Hebei Province,China(Grant No.A2020202002).
文摘A novel Lamb wave frequency-mixing technique is proposed for locating microcracks in a thin plate,which does not require the resonance condition of Lamb wave mixing and can accurately locate the microcracks through only one-time sensing.Based on the bilinear stress-strain constitutive model,a two-dimensional finite element(FE)model is built to investigate the frequency-mixing response induced by the interaction between two primary Lamb waves and a microcrack.When two primary Lamb waves of A0 and S0 modes with different frequencies excited on the same side of the plate simultaneously impinge on the examined microcrack,under the modulation of the contact acoustic nonlinearity,the microcrack itself can be deemed as the secondary sound source and it will radiate the Lamb waves of new combined frequencies.Based on the time of flight of the generated A0 mode at difference frequency,an indicator named normalized amplitude index(NAI)is defined to directly locate the multi-microcracks in the given plate.It is found that the number and location of the microcracks can be intuitively visualized by using the NAI based frequency-mixing technique.It is also demonstrated that the proposed frequency mixing technique is a promising approach for the microcrack localization.
