Showing papers on "Acoustic wave published in 2001"
TL;DR: A spherical harmonics analysis is used to derive performance bounds on how well an array of loudspeakers can recreate a three-dimensional (3-D) plane-wave sound field within a spherical region of space.
Abstract: Reproduction of a sound field is a fundamental problem in acoustic signal processing. In this paper, we use a spherical harmonics analysis to derive performance bounds on how well an array of loudspeakers can recreate a three-dimensional (3-D) plane-wave sound field within a spherical region of space. Specifically, we develop a relationship between the number of loudspeakers, the size of the reproduction sphere, the frequency range, and the desired accuracy. We also provide analogous results for the special case of reproduction of a two-dimensional (2-D) sound field. Results are verified through computer simulations.
378 citations
TL;DR: A brief overview of acoustic wave sensor physics, materials, sensor types, and applications is presented in this paper, where emphasis is placed on the different types and their respective advantages, and their specific applications in industry.
Abstract: A brief overview of acoustic wave sensor physics, materials, sensor types, and applications is presented in this paper. Emphasis is placed on the different types of acoustic wave sensors, their respective advantages, and their specific applications in industry.
368 citations
TL;DR: The sensitivity of nonlinear elastic wave spectroscopy (NEWS) methods to the detection of damage features (cracks, flaws, etc.) is far greater than can be obtained with linear acoustical methods as mentioned in this paper.
Abstract: Nonlinear elastic wave spectroscopy (NEWS) represents a class of powerful tools which explore the dynamic nonlinear stress–strain features in the compliant bond system of a micro-inhomogeneous material and link them to micro-scale damage. Hysteresis and nonlinearity in the constitutive relation (at the micro-strain level) result in acoustic and ultrasonic wave distortion, which gives rise to changes in the resonance frequencies as a function of drive amplitude, generation of accompanying harmonics, nonlinear attenuation, and multiplication of waves of different frequencies. The sensitivity of nonlinear methods to the detection of damage features (cracks, flaws, etc.) is far greater than can be obtained with linear acoustical methods (measures of wavespeed and wave dissipation). We illustrate two recently developed NEWS methods, and compare the results for both techniques on roofing tiles used in building construction.
303 citations
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TL;DR: In this paper, a position of an object in contact with the non-piezoelectric substrate is detected based on the received results at the two receiving elements, and the sensitivity in a region near the diagonal, which is influenced largely by propagation loss of the surface acoustic waves, is improved by increasing the width of the electrode fingers of the excitation elements and/or the receiving elements.
Abstract: Surface acoustic waves are propagated in a lower-left oblique direction and a lower-right oblique direction from an excitation element located on the upper side of a non-piezoelectric substrate and then received by receiving elements located on the left side and the right side, while surface acoustic waves are propagated in an upper-left oblique direction and an upper-right oblique direction from an excitation element located on the lower side of the non-piezoelectric substrate and then received by the receiving elements located on the left side and the right side. Based on the received results at the two receiving elements, a position of an object in contact with the non-piezoelectric substrate is detected. The sensitivity in a region near the diagonal, which is influenced largely by propagation loss of the surface acoustic waves, is improved by increasing the widths of the electrode fingers of the excitation elements and/or the receiving elements, the number of pairs of the electrode fingers, or the aperture width of comb-like electrodes, according to an increase in the propagation distances of the surface acoustic waves, i.e., toward the region near the diagonal.
211 citations
TL;DR: In this paper, the authors highlight the use of passive measurement of acoustic emissions created by a process as a potentially non-invasive, real-time monitoring technique to be used in process control.
208 citations
TL;DR: In this article, the generation of electron-acoustic waves in an unmagnetized, four-component plasma consisting of stationary cold and hot Maxwellian electrons, drifting electron beam and ions was examined.
201 citations
TL;DR: In this paper, the authors investigated the form and dynamics of shock-acoustic waves generated by earthquakes and used the method for detecting and locating the sources of ionospheric impulsive disturbances, based on using data from a global network of receivers of the GPS navigation system.
Abstract: . We investigate the form and dynamics of shock-acoustic waves generated by earthquakes. We use the method for detecting and locating the sources of ionospheric impulsive disturbances, based on using data from a global network of receivers of the GPS navigation system, and require no a priori information about the place and time of the associated effects. The practical implementation of the method is illustrated by a case study of earthquake effects in Turkey (17 August and 12 November 1999), in Southern Sumatra (4 June 2000), and off the coast of Central America (13 January 2001). It was found that in all instances the time period of the ionospheric response is 180–390 s, and the amplitude exceeds, by a factor of two as a minimum, the standard deviation of background fluctuations in total electron content in this range of periods under quiet and moderate geomagnetic conditions. The elevation of the wave vector varies through a range of 20–44°, and the phase velocity (1100–1300 m/s) approaches the sound velocity at the heights of the ionospheric F-region maximum. The calculated (by neglecting refraction corrections) location of the source roughly corresponds to the earthquake epicenter. Our data are consistent with the present views that shock-acoustic waves are caused by a piston-like movement of the Earth’s surface in the zone of an earthquake epicenter. Key words. Ionosphere (ionospheric disturbances; wave propagation) – Radio science (ionospheric propagation)
181 citations
TL;DR: In this paper, a wide-band microphone is used to detect the audible acoustic wave generated during laser ablation in ambient air and under water, and it is found that the laser ablating rate is highly enhanced by the water film.
Abstract: Laser ablation of solid substrates in ambient air and under water is investigated. It is found that the laser ablation rate is highly enhanced by the water film. A wide-band microphone is used to detect the audible acoustic wave generated during laser ablation. Peak-to-peak amplitude of the acoustic wave recorded in water confinement regime (WCR) is greater than that recorded in ambient. It is assumed that the plasma generated in WCR induces a much stronger pressure. This high-pressure, high-temperature plasma results in a much higher ablation rate. Theoretical calculation is also carried out to verify this assumption. By proper calibration, acoustic wave detection can be used as a real-time monitoring of the laser ablation.
178 citations
TL;DR: In this article, the initial phase of hypersonic boundary-layer transition comprising excitation of boundary layer modes and their downstream evolution from receptivity regions to the unstable region (instability prehistory problem) is considered.
Abstract: The initial phase of hypersonic boundary-layer transition comprising excitation of boundary-layer modes and their downstream evolution from receptivity regions to the unstable region (instability prehistory problem) is considered. The disturbance spectrum reveals the following features: (1) the first and second modes are synchronized with acoustic waves near the leading edge; (2) further downstream, the first mode is synchronized with entropy and vorticity waves; (3) near the lower neutral branch of the Mack second mode, the first mode is synchronized with the second mode. Disturbance behavior in Regions (2) and (3) is studied using the multiple-mode method accounting for interaction between modes due to mean-flow nonparallel effects. Analysis of the disturbance behavior in Region 3) provides the intermodal exchange rule coupling input and output amplitudes of the first and second modes. It is shown that Region (3) includes branch points at which disturbance group velocity and amplitude are singular. These singularities can cause difficulties in stability analyses. In Region (2), vorticity/entropy waves are partially swallowed by the boundary layer. They may effectively generate the Mack second mode near its lower neutral branch.
173 citations
TL;DR: In this paper, a linear model has been constructed to estimate the effect of entropy waves on the thermo-acoustic response and stability of a combustor with a choked exit nozzle, as it might be found in a gas turbine.
Abstract: Thermoacoustic instabilities are a cause for concern in combustion applications as diverse as small household burners, gas turbines or rocket engines. In this work, a feedback mechanism is analyzed, which couples combustion chamber acoustics with convectively transported fluctuations of entropy (entropy waves) generated within a premixed flame. Essential elements of this thermo-acoustic feedback loop are fluctuations in fuel concentration, induced by acoustic disturbances at the location of fuel injection, convective transport of fuel inhomogeneities through the premixing section of the burner, modulations in heat release rate and hot gas entropy resulting from the consumption of fuel/air mixture with varying fuel concentration by the flame, and the generation of sound through entropy non-uniformities at the turbine inlet. From a qualitative analysis based on relative phases, it is concluded that depending on the various convective and acoustic time lags involved, entropy waves may couple constructively as well as destructively with combustor acoustics. However, such qualitative analysis does not indicate whether the coupling between entropy and acoustic waves is strong enough to significantly influence thermo-acoustic stability. Therefore, a linear model has been constructed to estimate the effect of entropy waves on the thermo-acoustic response and stability of a combustor with a choked exit nozzle, as it might be found in a gas turbine. Note that phenomena like dispersion of convective waves, distributed heat release, vortical velocities, etc., have not been taken into account, as they would burden the presentation with unnecessary complexity. Results obtained indicate that the interaction between combustor acoustics and entropy waves can be significant, especially for the lowest non-axisymmetric modes, and even at frequencies higher than those usually associated with convective waves. As expected, it was observed that the coupling between pressure and entropy waves at the exit nozzle can enhance as well as reduce the thermo-acoustic stability of a combustor, or the responsiveness to an external or internal fluid-mechanic excitation mechanism. It is concluded that comprehensive thermo-acoustic analysis of a premixed combustor with a choked exit must in general include generation and propagation of entropy waves and coupling with combustor acoustics.
169 citations
TL;DR: In this paper, it was shown that the nonlinear propagation of the dust-acoustic waves in a strongly coupled dusty plasma is governed by a Korteweg-de Vries-Burgers (K-dV-burgers) equation, derived from a set of generalized hydrodynamic equations for strongly correlated dust grains, as well as the Boltzmann distribution for electrons and ions.
Abstract: It is shown that the nonlinear propagation of the dust-acoustic waves in a strongly coupled dusty plasma is governed by a Korteweg-de Vries-Burgers (K-dV-Burgers) equation. The latter is derived from a set of generalized hydrodynamic equations for strongly correlated dust grains, as well as the Boltzmann distribution for electrons and ions. Possible stationary solutions of the K-dV-Burgers equation are represented in terms of monotonic/oscillatory shock profiles.
TL;DR: It is shown that hCP iron follows a Birch law for VP, which is used to extrapolate velocities to inner core conditions, and suggests an inner core that is 4 to 5% lighter than hcp iron.
Abstract: The dispersion of longitudinal acoustic phonons was measured by inelastic x-ray scattering in the hexagonal closed-packed (hcp) structure of iron from 19 to 110 gigapascals. Phonon dispersion curves were recorded on polycrystalline iron compressed in a diamond anvil cell, revealing an increase of the longitudinal wave velocity (VP) from 7000 to 8800 meters per second. We show that hcp iron follows a Birch law for VP, which is used to extrapolate velocities to inner core conditions. Extrapolated longitudinal acoustic wave velocities compared with seismic data suggest an inner core that is 4 to 5% lighter than hcp iron.
TL;DR: In this paper, the boundary layer receptivity of the sharp leading edge of a at plate to acoustic waves induced by two-dimensional and three-dimensional perturbers was investigated for a free-stream Mach number M∞ = 5.92.
Abstract: Experimental investigations of the boundary layer receptivity, on the sharp leading edge of a at plate, to acoustic waves induced by two-dimensional and three-
dimensional perturbers, have been performed for a free-stream Mach number M∞ = 5.92. The fields of controlled free-stream disturbances were studied. It was shown that two-dimensional and three-dimensional perturbers radiate acoustic waves and that these perturbers present a set of harmonic motionless sources and moving sources with constant amplitude. The disturbances excited in the boundary layer were measured. It was found that acoustic waves impinging on the leading edge generate Tollmien–Schlichting waves in the boundary layer. The receptivity coefficients were obtained for several radiation conditions and intensities. It was shown that there is a dependence of receptivity coefficients on the wave inclination angles.
TL;DR: The general properties of fundamental antisymmetric A/sub 0/, symmetric S/ sub 0/, and shear horizontal SH/sub0/ acoustic waves propagating in thin piezoelectric plates have been theoretically investigated on samples of lithium niobate and lithium tantalate.
Abstract: The general properties of fundamental antisymmetric A/sub 0/, symmetric S/sub 0/, and shear horizontal SH/sub 0/ acoustic waves propagating in thin piezoelectric plates have been theoretically investigated on samples of lithium niobate (LiNbO/sub 3/) and lithium tantalate (LiTaO/sub 3/). The results obtained will be useful for a proper development of various physical, chemical, and biological sensors and devices for signal processing based on plate acoustic waves.
TL;DR: In this article, the authors outline a set of ideas for implementing a quantum processor based on technology used in surface acoustic wave (SAW) single-electron transport devices, which allow single electrons to be captured from a two-dimensional electron gas by a SAW.
Abstract: We outline a set of ideas for implementing a quantum processor based on technology used in surface acoustic wave (SAW) single-electron transport devices. These devices allow single electrons to be captured from a two-dimensional electron gas by a SAW. We discuss how these devices can be adapted to capture electrons in pure spin states and how both single and two-qubit gates can be constructed. We give designs for readout gates and discuss possible sources of error and decoherence.
TL;DR: Taking advantage of a noncontact remote measurement technique, the A/S coupling measurements for antitank landmine detection are conducted using a laser Doppler-vibrometer (LDV) and the resulting data analysts, which demonstrate the effectiveness of this technique are described in this paper.
Abstract: When an acoustic wave strikes the ground surface, energy is coupled into the motion of the fluid/solid frame comprising the ground. This phenomenon is termed acoustic-to-seismic (A/S) coupling In the ground, the Biot Type Il or Biot slow waves travel with a speed well below the speed of sound in air. The porous nature of the ground causes the entering acoustic wave to bend toward the normal and the acoustic wave propagates downward into the ground. When an object is buried a few cm below the ground surface, it distinctly changes the A/S coupled motion. These changes can be sensed by measuring vibrational particle velocity on the ground surface. Taking advantage of a noncontact remote measurement technique, the A/S coupling measurements for antitank landmine detection are conducted using a laser Doppler-vibrometer (LDV). Recent field measurements in both calibration and blind mine lanes and the resulting data analysts, which demonstrate the effectiveness of this technique, are described in this paper.
04 Jun 2001
TL;DR: In this article, a linear model for thermoacoustic oscillations in lean premixed prevaporised (LPP) combustors is described, where a thin annular combustor is assumed and circumferential modes are included but radial dependence is ignored.
Abstract: Lean premixed prevaporised (LPP) combustion can reduce NOx emissions from gas turbines, but often leads to combustion instability. Acoustic waves produce fluctuations in heat release, for instance by perturbing the fuel–air ratio or flame shape. These heat fluctuations will in turn generate more acoustic waves and in some situations self-sustained oscillations can result.A linear model for thermoacoustic oscillations in LPP combustors is described. A thin annular combustor is assumed and so circumferential modes are included but radial dependence is ignored. The geometry consists of straight ducts joined by short regions of area change. Perturbations to the flow can be thought of as a combination of acoustic, entropy and vorticity waves. The development of these waves along the straight ducts is found using a propagation matrix approach. At the entrance to the combustion chamber, a flame model is used in which the unsteady heat release is related to fluctuations in fuel–air ratio. Various possible inlet and outlet conditions are described. The model is then applied to a simplified example based on a sector rig. The resonant modes are found numerically and compared with the frequencies that occurred in experiments.Copyright © 2001 by ASME
TL;DR: A tactile display using surface a acoustic waves that can continuously change the fineness of the surface's grain by controlling the SAWs' burst frequency is proposed.
Abstract: Developing realistic tactile displays for virtual reality has been challenging. Tangible displays are increasingly important interfaces not only for augmenting the reality of computer graphics but also for conveying graphical information to persons with visual impairments. We propose a tactile display using surface a acoustic waves. We can continuously change the fineness of the surface's grain by controlling the SAWs' burst frequency.
TL;DR: In this paper, a wide-band microphone is used to detect the audible acoustic wave generated during the laser ablation of Si under a water surface, and it is found that the first peak-to-peak amplitude of the acoustic wave is the strongest when the water layer thickness is 1.1 mm above the substrate.
Abstract: Laser ablation of Si under a water surface has been investigated. The laser used is a KrF excimer laser, which has a wavelength of 248 nm and a pulse duration of 23 ns. It is found that the laser ablation rate of Si varies with the thickness of the water layer above the Si substrates. The laser ablation rate is the most highly enhanced with a water layer of 1.1 mm. It is assumed that the plasma generated in the water confinement regime with an optimal water layer thickness induces the strongest pressure. This high-pressure, high-temperature plasma results in the highest ablation rate. A wide-band microphone is used to detect the audible acoustic wave generated during the laser ablation. The amplitude of the acoustic wave is closely related to the ablation rate. It is found that the first peak-to-peak amplitude of the acoustic wave is the strongest when the water layer thickness is 1.1 mm above the substrate. Fast Fourier transform analysis of the wave forms shows that there are several frequency component...
TL;DR: A new class of nonlinear acoustic phenomena has been observed for acoustic wave interactions with cracked defects in solids, and acoustic-wave impact on a crack is shown to exhibit amplitude hysteresis and storage for parametric and non linear acoustic effects.
Abstract: A new class of nonlinear acoustic phenomena has been observed for acoustic wave interactions with cracked defects in solids. Parametric modulation of crack stiffness results in fractional acoustic subharmonics, wave instability, and generation of chaotic noiselike acoustic excitations. Acoustic-wave impact on a crack is shown to exhibit amplitude hysteresis and storage for parametric and nonlinear acoustic effects. The measured storage time amounts to several hours and is believed to be due to a long-term relaxation of thermally induced microstrain within a crack area.
TL;DR: In this article, an elongate probe, having a longitudinal axis and including a distal portion adapted for insertion into the cavity, is used for mapping a surface of a cavity within a body of a subject.
Abstract: Apparatus for mapping a surface of a cavity within a body of a subject includes an elongate probe, having a longitudinal axis and including a distal portion adapted for insertion into the cavity. A plurality of acoustic transducers are distributed along the longitudinal axis over the distal portion of the probe, which transducers are adapted to be actuated individually to emit acoustic waves while the probe is in the cavity, and are further adapted to receive the acoustic waves after reflection of the waves from the surface of the cavity and to generate, responsive to the received waves, electrical signals indicative of times of flight of the waves.
TL;DR: In this paper, a preconditioner for the conjugate gradient method applied to the normal equation was constructed to solve the regularized linearized operator equation in each Newton step, reducing the number of operator evaluations dramatically compared to standard regularized Newton methods.
Abstract: We examine the scattering of time-harmonic acoustic waves in inhomogeneous media The problem is to recover a spatially varying refractive index in a three-dimensional medium from far-field measurements of scattered waves corresponding to incoming waves from all directions This problem is exponentially ill-posed and of a large scale since a solution of the direct problem corresponds to solving a partial differential equation in 3 for each incident wave We construct a preconditioner for the conjugate gradient method applied to the normal equation to solve the regularized linearized operator equation in each Newton step This reduces the number of operator evaluations dramatically compared to standard regularized Newton methods Our method can also be applied effectively to other exponentially ill-posed problems, for example, in impedance tomography, heat conduction and obstacle scattering To solve the direct problems, we use an improved fast solver for the Lippmann–Schwinger equation suggested by Vainikko
Patent•
09 Oct 2001TL;DR: In this article, a method for estimating formation properties by analyzing acoustic waves that are emitted from and received by a bottom hole assembly is presented, based on a bottom-hole assembly.
Abstract: The present invention is a method for estimating formation properties (4), by analyzing acoustic waves (20) that are emitted from and received by a bottom hole assembly (14).
15 Jul 2001
TL;DR: In this paper, a linear model of the exciting force wave is derived to evaluate the exciting forces and to optimize the design of stator winding, rotor PM shape and rotor PM skew angle for minimization of sound power level for low noise motor design.
Abstract: Analysis of electromagnetic vibration and acoustic noise assessment and methods to minimize resultant sound power level for low noise motor design is presented in this paper. The linear model of the exciting force wave is derived to evaluate the exciting force and to optimize the design of stator winding, rotor PM shape and rotor PM skew angle for minimization of sound power level for low noise motor design. Mode number and frequency of the exciting force wave, natural vibration frequency, maximum vibration velocity and maximum vibration displacement of main vibration source are introduced to evaluate machine vibration. Resultant sound power levels for the cylindrical sound wave and the plane sound wave models are introduced to analyze the acoustic noise assessment of both axial and radial flux PM machines respectively. Finally, electromagnetic vibration and acoustic noise assessment of both radial and axial flux surface mounted motor structures are completed and illustrated in the paper.
TL;DR: In this article, a parametric analysis of the receptivity of the hypersonic boundary layer to free-stream disturbances is performed for a two-dimensional Mach 15 viscous flow over a parabola.
Abstract: The receptivity of hypersonic boundary layers to free-stream disturbances, which is the process of environmental disturbances initially entering the boundary layers and generating disturbance waves, is altered considerably by the presence of bow shocks in hypersonic flow fields. This paper presents a numerical simulation study of the generation of boundary layer disturbance waves due to free-stream waves, for a two-dimensional Mach 15 viscous flow over a parabola. Both steady and unsteady flow solutions of the receptivity problem are obtained by computing the full Navier–Stokes equations using a high-order-accurate shock-fitting finite difference scheme. The effects of bow-shock/free-stream-sound interactions on the receptivity process are accurately taken into account by treating the shock as a discontinuity surface, governed by the Rankine-Hugoniot relations. The results show that the disturbance waves generated and developed in the hypersonic boundary layer contain both first-, second-, and third-mode waves. A parametric study is carried out on the receptivity characteristics for different free-stream waves, frequencies, nose bluntness characterized by Strouhal numbers, Reynolds numbers, Mach numbers, and wall cooling. In this paper, the hypersonic boundary-layer receptivity is characterized by a receptivity parameter defined as the ratio of the maximum induced wave amplitude in the first-mode-dominated region to the amplitude of the free-stream forcing wave. It is found that the receptivity parameter decreases when the forcing frequency or nose bluntness increase. The results also show that the generation of boundary layer waves is mainly due to the interaction of the boundary layer with the acoustic wave field behind the bow shock, rather than interactions with the entropy and vorticity wave fields.
TL;DR: In this paper, the authors describe the design and performance of micromachined, self-focusing acoustic-wave liquid ejector (AWLE) that requires no heat, nozzle, nor acoustic lens.
Abstract: This paper describes the design and performance of micromachined, self-focusing acoustic-wave liquid ejector (AWLE) that requires no heat, nozzle, nor acoustic lens. The AWLE has a very simple device structure and is easy to fabricate. Three versions of AWLE have been designed, fabricated, and tested for an ink-jet printing application. Also developed are computer simulation and design aids that take into account the acoustic loss in water and the two-time wave reflections at the water-air and water-transducer interfaces. The AWLE has been observed to eject water droplets of about 5 /spl mu/m in diameter with radio frequency (RF) pulses of 5 /spl mu/s pulsewidth. Overall, the AWLE has been shown to be capable of improving the printing resolution and speed of ink-jet printing significantly.
TL;DR: In this paper, a model for a single, coupled Helmholtz resonator system mounted on a one-dimensional duct is presented, where a model of the membrane is used to estimate equivalent piston properties from measured physical properties.
Abstract: Helmholtz resonators are used in a variety of applications to reduce the transmission of unwanted sound. This work demonstrates that mechanically coupled resonators can be used to design a particular transmission loss response, provide a wider bandwidth of attenuation, and adapt the transmission loss characteristics of a structure to attenuate disturbances of varying frequency. An analytical model is developed for a single, coupled resonator system mounted on a one-dimensional duct. Experiments are conducted on a similar system that uses a thin membrane to couple the resonator volumes. A simplistic model of the membrane is presented to estimate equivalent piston properties from measured physical properties. Experiments confirm that the coupled resonator system behaves as predicted by the model simulations, and that the transmission loss can be shaped by adjusting the mass or stiffness of the coupling member. The experimental results also illustrate the structural-acoustic coupling effects between the resonators and the membrane, and indicate that a more inclusive model of the membrane and acoustic dynamics is required in order to accurately predict the resonator transmission loss.
TL;DR: In this article, the authors used a sub-picosecond interferometer to study the acoustics waves created by heating a partially perforated metal film with a subposecond laser pulse and measured the period of initial oscillations in the metal film and the amplitude of the sound wave in the substrate.
Abstract: Picosecond interferometry is used to study the acoustics waves created by heating Pt films with a subpicosecond laser pulse. Both the period of the initial oscillations in the metal film and the amplitude of the sound wave in the substrate are measured quantitatively. The platinum films are roughened by irradiation with energetic ions. The amplitude of the sound wave is doubled at those irradiation levels where the platinum coverage has been reduced by about one-half. A theory for the amplitude of the launched acoustic wave predicts that the acoustic amplitude is proportional to the mean square film thickness. Thus changes in the morphology of a partially perforated metal film can be observed using a simple, nondestructive optical technique.
TL;DR: In this paper, the authors examined the nonlinear propagation of electron-acoustic waves in an unmagnetized, four-component plasma consisting of hot Maxwellian electrons, fluid cold and beam electrons and ions.
TL;DR: In this article, a new approach for the analysis of transient waves propagating in anisotropic composite laminates is presented, where the wavelet transform (WT) using the Gabor wavelet is applied to the time-frequency analysis of dispersive flexural waves in these plates.
Abstract: A new approach is presented for the analysis of transient waves propagating in anisotropic composite laminates. The wavelet transform (WT) using the Gabor wavelet is applied to the time-frequency analysis of dispersive flexural waves in these plates. It can be shown that the peaks of the magnitude of WT in a time-frequency domain is related to the arrival times of the group velocity. Experiments were performed using a lead break as the simulated acoustic emission source on the surface of unidirectional and quasi-isotropic laminates. A method was developed to obtain the group velocity of the flexural mode as a function of frequency. Theoretical predictions were made using the Mindlin plate theory, which includes the effects of shear deformation and rotatory inertia. Our predictions on the dispersion of the flexural mode showed good agreement with the experimental results.