Showing papers on "Lamb waves published in 2015"
TL;DR: In this article, a signal processing of full wavefield data is proposed for detection, localization and visualization of a crack growth in thin-walled structures. But the proposed method only out-of-plane velocities are used.
124 citations
TL;DR: In this paper, Laminated composites are susceptible to delamination due to their weak transverse tensile and interlaminar shear strength as compared to their in-plane properties.
Abstract: Laminated composites are susceptible to delamination due to their weak transverse tensile and interlaminar shear strengths as compared to their in-plane properties. Delamination damage can occur in...
109 citations
TL;DR: In this paper, a predictive model of attenuated guided wave propagation in carbon fiber-reinforced polymer using Rayleigh damping is developed, which can be used for structural health monitoring applications.
Abstract: In this work, a predictive model of attenuated guided wave propagation in carbon fiber–reinforced polymer using Rayleigh damping is developed. After a brief introduction, this article reviews the theory of guided waves in anisotropic composite materials. It follows with a discussion of the piezoelectric wafer active sensors, which are lightweight and inexpensive transducers for structural health monitoring applications. Experiments were performed on a carbon fiber–reinforced polymer panel to measure the dispersion curves and the piezoelectric wafer active sensors tuning curves. Lamb wave damping coefficient was modeled using the multi-physics finite element method and compared with experimental results. A discussion about the capability to simulate, with multi-physics finite element method commercial software, guided wave in composite material using the Rayleigh damping is developed. This article ends with conclusion, and suggestions for further work are also presented.
97 citations
TL;DR: In this paper, the authors extended the use of temporal signal processing to the realm of nonlinear Lamb waves, so as to reap the high sensitivity of Lamb wave to small-scale damage (e.g., fatigue cracks), and the efficacy of temporal signals processing in locating damage.
96 citations
TL;DR: For the first time, it is demonstrated that the flexible humidity sensors work as usual without noticeable deterioration in performance even under severe bending conditions up to 1500 με.
Abstract: This paper reports high performance flexible Lamb wave humidity sensors with a graphene oxide sensing layer. The devices were fabricated on piezoelectric ZnO thin films deposited on flexible polyimide substrates. Two resonant peaks, namely the zero order antisymmetric (A0) and symmetric (S0) mode Lamb waves, were observed and fitted well with the theoretical analysis and modelling. With graphene oxide microflakes as the sensing layer, the sensing performance of both wave modes was investigated. The humidity sensitivity of the A0 mode is 145.83 ppm per %RH (at humidity 85%RH), higher than that of S0 mode of 89.35 ppm per %RH. For the first time, we have demonstrated that the flexible humidity sensors work as usual without noticeable deterioration in performance even under severe bending conditions up to 1500 μe. Also the sensors showed an excellent stability upon repeated bending for thousand times. All the results demonstrated that the Lamb wave flexible humidity sensors have a great potential for application in flexible electronics.
95 citations
TL;DR: In this paper, an application of Artificial Neural Networks and Probability Ellipse methods for damage detection using Lamb waves is presented, where wave propagation data are used to determine the location and degree of damage in metallic and composite plates.
90 citations
TL;DR: A modified Lysmer–Kuhlemeyer approach to be used in the NRB design for Lamb wave problems is proposed, which can be effectively and conveniently implemented in commercial finite element (FE) codes.
90 citations
TL;DR: In this article, a multipath guided wave imaging algorithm is presented that leverages the large number of echoes and reverberations present in recorded ultrasonic waveforms to detect and locate damage in geometrically complex structures.
Abstract: Ultrasonic guided wave imaging can potentially detect and localize damage over a large area with a sparse, or spatially distributed, array. However, conventional delay-and-sum imaging methods require knowledge of the propagation velocity and rely on direct-path propagation from the transmitting transducer, to a damage location, and finally to the receiving transducer, limiting the applicability of these techniques to relatively simple structures. A multipath guided wave imaging algorithm is presented here that leverages the large number of echoes and reverberations present in recorded ultrasonic waveforms to successfully detect and locate damage in geometrically complex structures. Multipath guided wave imaging not only allows imaging to be performed on structures with complex features (e.g. stiffeners, lap joints, and rivets) and inhomogeneous and anisotropic materials but also significantly improves image quality with far fewer sensors compared to conventional elliptical imaging. Experimental results fr...
71 citations
TL;DR: In this paper, the propagation characteristics of Lamb waves in composite plate-type acoustic metamaterial constituted of one-side cylindrical stubs deposited on a two-dimensional binary locally resonant phononic plate were investigated.
69 citations
TL;DR: In this paper, an analytical wave approach was developed to describe the physics properties of multiresonant metamaterials for Lamb waves propagating in plates, where a 10 by 10 uniform, periodic array of long rods attached to the surface of the plate formed the substrate in which antisymmetric Lamb waves are excited.
Abstract: We develop an analytical wave approach to describe the physics properties of multiresonant metamaterials for Lamb waves propagating in plates. The metamaterial that we characterize consists of a 10 by 10 uniform, periodic array of long rods attached to the surface of the plate that forms the substrate in which antisymmetric ${A}_{0}$ Lamb waves are excited. We show that the ${A}_{0}$ Lamb wave propagation through the metamaterial can be accurately modeled using a simplified theory that replaces the two-dimensional array with a one-dimensional beam with a linear array of 10 rods. The wave propagation problem is solved rigorously for this one-dimensional system using the scattering matrix for a single rod. The exact eigenvalues of the system are approximated in a long wavelength expansion to determine a simple expression for the effective wave number and dispersion of the metamaterial. The modeled dispersion is compared with an experimental measurement of the dispersion inside the metamaterial with excellent agreement. The multiresonant rods, restricted to longitudinal vibration consistent with ${A}_{0}$ Lamb waves excited in the plate, produce two wide stop bands in the frequency domain from 0 to 10 kHz where the stop or passband boundaries align with the minima and maxima of the rod's impedance. We show that a negative effective density is obtained in the stop band. With the simple yet highly accurate relations given in this paper we have a tool to develop more complex metamaterials with rods and plates of different properties.
68 citations
TL;DR: The numerical design of a directional invisibility cloak for backward scattered elastic waves propagating in a thin plate (A0 Lamb waves) shows the best directional cloaking was obtained when the resonators' length decreases from the central to the outermost ring.
Abstract: This paper deals with the numerical design of a directional invisibility cloak for backward scattered elastic waves propagating in a thin plate (A 0 Lamb waves). The directional cloak is based on a set of resonating beams that are attached perpendicular to the plate and are arranged at a sub-wavelength scale in ten concentric rings. The exotic effective properties of this locally resonant metamaterial ensure coexistence of bandgaps and directional cloaking for certain beam configurations over a large frequency band. The best directional cloaking was obtained when the resonators' length decreases from the central to the outermost ring. In this case, flexural waves experience a vanishing index of refraction when they cross the outer layers, leading to a frequency bandgap that protects the central part of the cloak. Numerical simulation shows that there is no back-scattering in these configurations. These results might have applications in the design of seismic-wave protection devices.
TL;DR: Some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures.
TL;DR: In this article, the suitability of the two zero-order Lamb wave modes to detect multiple barely-visible impact damage in composite material was assessed and the results were consistently validated by digital shearography, ultrasonic C-scan and optical microscopy.
Abstract: This work assesses the suitability of the two zero-order Lamb wave modes to detect multiple barely-visible impact damage in composite material. Three specimens were subjected to damage at three different low-energy levels and one was left as an undamaged reference sample. Ultrasonic Lamb wave modes were selectively generated by surface-bonded piezoceramic wafer transducers in two tuned configurations. By using an algorithm based on the Akaike Information Criterion the time-of-flight of the Lamb modes was determined, allowing their threshold detection capabilities for the studied application to be successfully benchmarked. The results were consistently validated by digital shearography, ultrasonic C-scan and optical microscopy. A study of the effects on structural integrity was completed with an assessment of the damping ratio and residual bending strength proving to be sensitive parameters to the induced damage.
TL;DR: In this article, the actual wing slats of a Boeing 737 aircraft were used for detection of typical damages observed at the normal operating conditions, and the cuts and impact damages of the slats were considered.
TL;DR: The main features and utility of proposed d36 piezoelectric wafer for guided wave generation and detection in structural health monitoring are demonstrated.
TL;DR: In this paper, the authors combined air-coupled Lamb wave scan method and virtual time reversal (VTR) algorithm and proposed a composite baseline-free delamination inspection technique of composite plates according to VTR algorithm, time reversal process is virtually performed through signal operations and the hardware manipulation for time reversal is not required.
Abstract: In the paper, we combined air-coupled Lamb wave scan method and virtual time reversal (VTR) algorithm and proposed a composite baseline-free delamination inspection technique of composite plates According to VTR algorithm, time reversal process is virtually performed through signal operations and the hardware manipulation for time reversal is not required Baseline-free damage inspection can be achieved by comparing the first input actuation signal with the reconstructed final signal obtained by VTR algorithm An air-coupled Lamb wave scan method combined with VTR-based probabilistic imaging algorithm is developed for delamination inspection of composite plates Carbon fiber-reinforced composite plates with the delaminations of different shapes and sizes were experimentally tested The testing results are well in accordance with the actual delamination locations and sizes as well as the results obtained with the commercial point-to-point immersion C-scan system
TL;DR: In this article, a four-node plate bending element based on first order shear deformation theory is used to predict the propagation velocity of first antisymmetric Lamb wave mode in graphite/epoxy composite plates by numerical simulation.
TL;DR: In this article, an acoustic metasurface that converts longitudinal acoustic waves into transverse elastic waves in an acoustic-elastic coupled system is presented, and the mechanism that changes the direction of the wave motion is described.
Abstract: This letter presents an acoustic metasurface that converts longitudinal acoustic waves into transverse elastic waves in an acoustic-elastic coupled system. Metasurface configurations are obtained by a level set-based topology optimization method, and we describe the mechanism that changes the direction of the wave motion. Numerical examples of 2D problems with prescribed frequencies of incident acoustic waves are provided, and transverse elastic wave amplitudes are maximized by manipulating the propagation of the acoustic waves. Frequency analysis reveals that each of the different metasurface designs obtained for different wavelengths of incident waves provides peak response at the target frequency.
TL;DR: In this article, a transverse mode suppression theory and its experimental verification through aluminum nitride Lamb wave resonators (LWRs) operating at 142 MHz is presented, based on which the origin of transverse modes in LWR is investigated.
Abstract: This paper presents a transverse mode suppression theory and its experimental verification through aluminum nitride Lamb wave resonators (LWRs) operating at 142 MHz An effective 2-D approximation model of the LWR is proposed, based on which the origin of transverse modes in LWR is investigated The displacement distribution, resonant frequencies, and electromechanical coupling coefficients $( k_{t}^{2})$ of the main mode and its auxiliary transverse modes are obtained A spurious mode suppression theory in terms of the expression of $k_{t}^{2}$ in the 2-D model is proposed Three kinds of electrodes are designed to suppress the transverse mode adjacent to the main mode, including a novel interdigital transducer gap technique that is reported for the first time With the applicable geometries, these methods reduce the spurious response from 118 to <05 dB, without significantly affecting the figure of merit of the resonator
TL;DR: In this article, the authors investigated Lamb wave propagation in a beam under lead zirconate titanate actuation/sensing, in which the lead ZIRCONATE titanate effects are included.
Abstract: Lead zirconate titanate actuators and sensors have been the widely used in Lamb wave–based damage detection applications. The excitation frequency, waveform, and wave propagation characteristics should be comprehensively considered to effectively conduct diagnosis of incipient forms of damage. In this article, we investigate Lamb wave propagation in a beam under lead zirconate titanate actuation/sensing, in which the lead zirconate titanate effects are included. First, mathematical models are developed to account for both unimorph (i.e. sensor mode) and bimorph (i.e. actuator mode) configurations. The Timoshenko beam theory is adopted for both base beam and lead zirconate titanate layers to accommodate high-frequency responses. Second, the fully coupled electromechanical governing equations are determined and solved in an analytical form to formulate the spectral finite element model. Finally, parametric studies are carried out to determine the optimal actuation frequency, sensor size, actuator, and senso...
Abstract: This paper proposes a very promising acquisition-analysis procedure to evaluate real-time damage in carbon fiber-reinforced polymer (CFRP) composite plates by means of the acoustic emission (AE) method. It shows how, by using appropriate acquisition frequency filters and very narrow time windows, it is possible to avoid reflection at boundaries and successfully split the A0 and S0 Lamb modes of the AE signals. After that, an appropriate algorithm —based on the comparison of strength of both modes in time and frequency domains— allows one to associate each AE event to a particular damage mechanism (delamination, fiber breaking and matrix micro-cracking). Experimental results from three point bending tests carried out on 22-layer CFRP samples, with delamination artificially induced by a Teflon film, clearly demonstrate the real-time evaluation of the induced delamination and the beginning and growth of new ones.
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TL;DR: In this article, the results of a combined experimental and numerical study of the generation of internal waves using the novel internal wave generator design of Gostiaux et al. were presented.
Abstract: We present the results of a combined experimental and numerical study of the generation of internal waves using the novel internal wave generator design of Gostiaux et al. (2007). This mechanism, which involves a tunable source comprised of oscillating plates, has so far been used for a few fundamental studies of internal waves, but its full potential has yet to be realized. Our studies reveal that this approach is capable of producing a wide variety of two-dimensional wave fields, including plane waves, wave beams and discrete vertical modes in finite-depth stratifications. The effects of discretization by a finite number of plates, forcing amplitude and angle of propagation are investigated, and it is found that the method is remarkably efficient at generating a complete wave field despite forcing only one velocity component in a controllable manner. We furthermore find that the nature of the radiated wave field is well predicted using Fourier transforms of the spatial structure of the wave generator.
TL;DR: The proposed non-contact hybrid system can effectively characterize the dispersive relation without knowledge of neither the materials characteristics nor the mathematical model and proved a high sensitivity of the air-coupled and laser ultrasound in characterizing Lamb wave dispersion in plate-like structures.
TL;DR: This study presents an exact, analytic expression for the two-dimensional Fourier transform description of shear wave propagation in viscoelastic materials following asymmetric Gaussian excitations and uses this expression to evaluate the bias in 2D-FT measurements obtained using the plane or cylindrical wave assumptions.
Abstract: Recent measurements of shear wave propagation in viscoelastic materials have been analyzed by constructing the two-dimensional Fourier transform (2D-FT) of the spatial-temporal shear wave signal and using an analysis procedure derived under the assumption the wave is described as a plane wave, or as the asymptotic form of a wave expanding radially from a cylindrically symmetric source. This study presents an exact, analytic expression for the 2D-FT description of shear wave propagation in viscoelastic materials following asymmetric Gaussian excitations and uses this expression to evaluate the bias in 2D-FT measurements obtained using the plane or cylindrical wave assumptions. A wide range of biases are observed depending on specific values of frequency, aspect ratio R of the source asymmetry, and material properties. These biases can be reduced significantly by weighting the shear wave signal in the spatial domain to correct for the geometric spreading of the shear wavefront using a factor of x(p). The optimal weighting power p is found to be near the theoretical value of 0.5 for the case of a cylindrical source with R = 1, and decreases for asymmetric sources with R > 1.
TL;DR: In this paper, a detailed study of the interaction of Rayleigh surface waves with defects in a thick aluminum plate is carried out using numerical simulations and laboratory experiments, which are shown to partially result in Lamb wave conversion.
TL;DR: In this paper, the second harmonic generation is used to analyze composite specimens for impact damages, and the results of the relative acoustical nonlinearity parameter are compared to the development of the group velocity due to impact damages.
Abstract: To detect micro-structural damages like fiber/matrix cracks and delaminations in composite materials accurately new methods are developed. Previous works have investigated and shown that the acoustical nonlinearity parameter is a good tool to detect micro-structural damages like plasticity in metal and fatigue damages in metal and composites. In this work, the second harmonic generation is used to analyze composite specimens for impact damages. Therefore, Lamb waves are launched and detected by a piezoelectric actuator and sensor, respectively, at a certain frequency to generate cumulative second harmonic modes. The excitation frequency has to meet special conditions. The signal processing is done by using the wavelet transform to avoid misinterpretations that may occur using the short-time Fourier transform. The Morlet wavelet is used as the mother wavelet. The results of the relative acoustical nonlinearity parameter are compared to the development of the group velocity due to impact damages. It is show...
TL;DR: In this article, an imaging algorithm based on time reversal is developed to detect multiple debonding in tapered composite sandwich panels, using guided waves at different excitation frequencies ranging from 150 to 200 kHz, from an active sensor network.
TL;DR: In this article, the authors used ultrasonic phased arrays for structural health monitoring (SHM) of planar structures, where 2D topologies are required to obtain unequivocal damage localization.
Abstract: Ultrasonic phased arrays have a considerable application potential for structural health monitoring (SHM) of planar structures. 2D topologies are required to obtain unequivocal damage localization ...
TL;DR: In this paper, the authors demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band.
Abstract: Integrating nanoscale electromechanical transducers and nanophotonic devices potentially can enable acousto-optic devices to reach unprecedented high frequencies and modulation efficiency. Here, we demonstrate acousto-optic modulation of a photonic crystal nanocavity using Lamb waves with frequency up to 19 GHz, reaching the microwave K band. The devices are fabricated in suspended aluminum nitride membrane. Excitation of acoustic waves is achieved with interdigital transducers with period as small as 300 nm. Confining both acoustic wave and optical wave within the thickness of the membrane leads to improved acousto-optic modulation efficiency in these devices than that obtained in previous surface acoustic wave devices. Our system demonstrates a scalable optomechanical platform where strong acousto-optic coupling between cavity-confined photons and high frequency traveling phonons can be explored.
TL;DR: In this article, a time domain spectral finite element is developed for improving the efficiency of numerical simulations of guided waves in laminated composite strips, which relies on a new generalized laminate mechanics model formulated to represent symmetric and anti-symmetric Lamb waves.