Showing papers on "Guided wave testing published in 2005"

Guided-wave and leakage characteristics of substrate integrated waveguide

Abstract: The substrate integrated waveguide (SIW) technique makes it possible that a complete circuit including planar circuitry, transitions, and rectangular waveguides are fabricated in planar form using a standard printed circuit board or other planar processing techniques. In this paper, guided wave and modes characteristics of such an SIW periodic structure are studied in detail for the first time. A numerical multimode calibration procedure is proposed and developed with a commercial software package on the basis of a full-wave finite-element method for the accurate extraction of complex propagation constants of the SIW structure. Two different lengths of the SIW are numerically simulated under multimode excitation. By means of our proposed technique, the complex propagation constant of each SIW mode can accurately be extracted and the electromagnetic bandstop phenomena of periodic structures are also investigated. Experiments are made to validate our proposed technique. Simple design rules are provided and discussed.

Finite-dimensional piezoelectric transducer modeling for guided wave based structural health monitoring

Abstract: Among the various schemes being considered for structural health monitoring (SHM), guided wave (GW) testing in particular has shown great promise. While GW testing using hand-held transducers for non-destructive evaluation (NDE) is a well established technology, GW testing for SHM using surface-bonded/embedded piezoelectric wafer transducers (piezos) is relatively in its formative years. Little effort has been made towards a precise characterization of GW excitation using piezos and often the various parameters involved are chosen without mathematical foundation. In this work, a formulation for modeling the transient GW field excited using arbitrary shaped surface-bonded piezos in isotropic plates based on the 3D linear elasticity equations is presented. This is then used for the specific cases of rectangular and ring-shaped actuators, which are most commonly used in GW SHM. Equations for the output voltage response of surface-bonded piezo-sensors in GW fields are derived and optimization of the actuator/sensor dimensions is done based on these. Finally, numerical and experimental results establishing the validity of these models are discussed.

Embedded non-destructive evaluation for structural health monitoring, damage detection, and failure prevention

Abstract: In this paper we review the state of the art in an emerging new technology: embedded ultrasonic non-destructive evaluation (NDE). Embedded ultrasonic NDE permits active structural health monitoring, i.e. the on-demand interrogation of the structure to determine its current state of structural health. The enabling element of embedded ultrasonic NDE is the piezoelectric wafer active sensor (PWAS). We begin by reviewing the guided wave theory in plate, tube, and shell structures, with special attention to Lamb waves. The mechanisms of Lamb wave excitation and detection with embeddable PWAS transducers is presented. It is shown analytically and verified experimentally that Lamb wave mode tuning can be achieved by the judicious combination of PWAS dimensions, frequency value, and Lamb mode characteristics. Subsequently, we address in turn the use of pitch-catch, pulse-echo, and phased array ultrasonic methods for Lambwave damage detection. In each case, the conventional ultrasonic NDE results are contrasted with embedded NDE results. Detection of cracks, disbonds, delaminations, and diffuse damage in metallic and composite structures are exemplified. Other techniques, such as the time reversal method and the migration technique, are also presented. The paper ends with conclusions and suggestions for further work.

Optical routing and sensing with nanowire assemblies

Abstract: The manipulation of photons in structures smaller than the wavelength of light is central to the development of nanoscale integrated photonic systems for computing, communications, and sensing. We assemble small groups of freestanding, chemically synthesized nanoribbons and nanowires into model structures that illustrate how light is exchanged between subwavelength cavities made of three different semiconductors. The coupling strength of the optical linkages formed when nanowires are brought into contact depends both on their volume of interaction and angle of intersection. With simple coupling schemes, lasing nanowires can launch coherent pulses of light through ribbon waveguides that are up to a millimeter in length. Also, interwire coupling losses are low enough to allow light to propagate across several right-angle bends in a grid of crossed ribbons. The fraction of the guided wave traveling outside the wire/ribbon cavities is used to link nanowires through space and to separate colors within multiribbon networks. In addition, we find that nanoribbons function efficiently as waveguides in liquid media and provide a unique means for probing molecules in solution or in proximity to the waveguide surface. Our results lay the spadework for photonic devices based on assemblies of active and passive nanowire elements and presage the use of nanowire waveguides in microfluidics and biology.

Lamb wave basis for impact-echo method analysis

Abstract: The impact-echo method has been developed over the past 20 years and is now widely used in the nondestructive evaluation of concrete. However, some practical issues remain unresolved, such as the physical basis for the empirical correction factor sbd used to obtain thickness mode frequency. A new approach based on guided wave theory is proposed in this paper: that the impact-echo resonance in plates corresponds to the zero-group-velocity frequency of the S1 Lamb mode. A numerical model is developed, verified by experiment, and then shown to adequately simulate the dynamic response of a concrete plate. Using this model the thickness resonance mode is identified and found to accurately match that particular Lamb mode in terms of shape and frequency. New values forb based on the Lamb mode model are computed and dependence on material Poisson's ratio is demonstrated.

Multi-mode propagation and diffusion in structures through finite elements

Abstract: The present work addresses the question of guided wave properties in structures. Guided multi-modal dispersion curves and diffusion of waves at singularities are the main concern. A propagative approach, based on a finite element model, is formulated. It provides an effective way to calculate the dispersion curves of complex guided structures. Some properties of guided waves are deduced from the formulation. The question of wave diffusion at substructures coupling locations is also considered. A closed formulation of the problem using Lagrange multipliers is presented. Its numerical implementation is detailed. Ultimately, a numerical test is offered. The case study concerns a thin walled structure.

Modal-reflectivity enhancement by geometry tuning in Photonic Crystal microcavities

Abstract: When a guided wave is impinging onto a Photonic Crystal (PC) mirror, a fraction of the light is not reflected back and is radiated into the claddings. We present a theoretical and numerical study of this radiation problem for several three-dimensional mirror geometries which are important for light confinement in micropillars, air-bridge microcavities and two-dimensional PC microcavities. The cause of the radiation is shown to be a mode-profile mismatch. Additionally, design tools for reducing this mismatch by tuning the mirror geometry are derived. These tools are validated by numerical results performed with a three-dimensional Fourier modal method. Several engineered mirror geometries which lower the radiation loss by several orders of magnitude are designed.

Omnidirectional guided wave inspection of large metallic plate structures using an EMAT array

Abstract: The design of an electromagnetic acoustic transducer (EMAT) array device for the inspection of large areas of metallic plate-like structures using the S/sub 0/ guided wave mode is described. The reasons for using the S/sub 0/ mode are discussed and it is shown how the choice of mode determines the nature of the EMAT array elements. A novel array construction technique is shown to be necessary whereby the EMAT coils for adjacent elements are overlapped in order to achieve the required element density. Results are presented that illustrate the operation of the device on steel and aluminum plate specimens in the thickness range from 5 to 10 mm. An area of at least 10 m/sup 2/ can be inspected from a single location. Spurious signals in the results are caused both by the unwanted A/sub 0/ mode and by S/sub 0/ sidelobes, the latter occurring at the same radial distance from the array as the genuine S/sub 0/ signal from a reflector, but in the wrong direction. The signal-to-coherent noise performance of the complete system is determined by the amplitude ratio of the largest genuine S/sub 0/ signal to the largest spurious signal. This is typically around 30 dB. The sensitivity of the device to artificial defects and genuine corrosion patches is demonstrated and the limitations of its operation are discussed. The feasibility of using the device with the S/sub 1/ guided wave mode to inspect a 20 mm thick plate is also demonstrated.

Generation and detection of guided waves using PZT wafer transducers

Abstract: We report here the use of finite element simulation and experiments to further explore the operation of the wafer transducer. We have separately modeled the emission and detection processes. In particular, we have calculated the wave velocities and the received voltage signals due to A0 and S0 modes at an output transducer as a function of pulse center frequency. These calculations include the effects of finite pulse width, pulse dispersion, and the detailed interaction between the piezoelectric element and the transmitting medium. We show that the received signals for A0 and S0 modes have maxima near the frequencies predicted from the previously published point-force model.

Guided propagation of terahertz pulses on metal wires

Abstract: We demonstrate a new waveguiding structure for terahertz (THz) radiation in which broadband THz pulses are confined and guided along a bare metal wire. The propagation of THz pulses on such a waveguide is characterized with a fiber-coupled terahertz time-domain spectroscopy system. Free-space THz radiation is coupled onto the waveguide at different positions along the wire, and spatially resolved detection of the electric field of the guided wave is performed at the end of the wire. This waveguide exhibits the lowest attenuation of any waveguide for broadband THz pulses reported so far because of the minimal exposed metallic surface area. It also supports propagation of broadband radiation with negligible group-velocity dispersion, making it especially suitable for use in THz sensing and diagnostic systems. In addition, the structural simplicity lends itself naturally to the facile manipulation of the guided pulses, including coupling, directing, and beam splitting. These results can be described in terms of a model developed by Sommerfeld for waves propagating along the surface of a cylindrical conductor.

Ultrasonic guided wave monitoring of composite wing skin-to-spar bonded joints in aerospace structures

Abstract: The monitoring of adhesively bonded joints by ultrasonic guided waves is the general topic of this paper. Specifically, composite-to-composite joints representative of the wing skin-to-spar bonds of unmanned aerial vehicles (UAVs) are examined. This research is the first step towards the development of an on-board structural health monitoring system for UAV wings based on integrated ultrasonic sensors. The study investigates two different lay-ups for the wing skin and two different types of bond defects, namely poorly cured adhesive and disbonded interfaces. The assessment of bond state is based on monitoring the strength of transmission through the joints of selected guided modes. The wave propagation problem is studied numerically by a semi-analytical finite element method that accounts for viscoelastic damping, and experimentally by ultrasonic testing that uses small PZT disks preferably exciting and detecting the single-plate s0 mode. Both the models and the experiments confirm that the ultrasonic ene...

The matching pursuit approach based on the modulated Gaussian pulse for efficient guided-wave damage inspection

Abstract: The success of the guided-wave damage inspection technology depends not only on the generation and measurement of desired waveforms but also on the signal processing of the measured waves, but less attention has been paid to the latter. This research aims to develop an efficient signal processing technique especially suitable for the current guided-wave technology. To achieve this objective, the use of a two-stage matching pursuit approach based on the Gabor dictionary is proposed. Instead of truncated sine pulses commonly used in waveguide inspection, Gabor pulses, the modulated Gaussian pulses, are chosen as the elastic energy carrier to facilitate the matching pursuit algorithm. To extract meaningful waves out of noisy signals, a two-stage matching pursuit strategy is developed, which consists of the following: rough approximations with a set of predetermined parameters characterizing the Gabor pulse, and fine adjustments of the parameters by optimization. The parameters estimated from measured longitudinal elastic waves can be then directly used to assess not only the location but also the size of a crack in a rod. For the estimation of the crack size, in particular, Love's theory is incorporated in the matching pursuit analysis. Several experiments were conducted to verify the validity of the proposed approach in damage assessment.

Guided wave tomography on an aircraft wing with leave in place sensors

Abstract: Leave in place sensor and guided wave tomographic techniques are combined together in structural health monitoring aging aircraft. In a sample problem, eight PZT transducers are mounted on the surface of the wing of an E2 aircraft. An area within a circle of 240 mm diameter is monitored with through transmission guided waves. The occurrence and progression of an artificial defect beside one rivet is clearly detected. Different computed tomography (CT) algorithms such as the back projection method, algebraic reconstruction method (ART) and multi resolution algebraic reconstruction technology (MART) are used in the defect image reconstruction with the feature of signal difference coefficient (SDC).

Torsional wave experiments with a new magnetostrictive transducer configuration.

Abstract: For the efficient long-range nondestructive structural health inspection of pipes, guided waves have become widely used. Among the various guided wave modes, the torsional wave is most preferred since its first branch is nondispersive. Our objective in this work is to develop a new magnetostrictive transducer configuration to transmit and receive torsional waves in cylindrical waveguides. The conventional magnetostrictive transducer for the generation and measurement of torsional waves consists of solenoid coils and a nickel strip bonded circumferentially to test pipes. The strip must be premagnetized by a permanent magnet before actual measurements. Because of the premagnetization, the transducer is not suitable for the long-term on-line monitoring of pipes buried underground. To avoid the cumbersome premagnetization and to improve the transduction efficiency, we propose a new transducer configuration using several pieces of nickel strips installed at 45° with respect to the pipe axis. If a static bias magnetic field is also applied, the transducer output can be substantially increased. Several experiments were conducted to study the performance of the proposed transducer configuration. The proposed transducer configuration was also applied for damage detection in an aluminum pipe.

Defect imaging with guided waves in a pipe

Abstract: Guided wave techniques are expected to become an effective means for rapid, long-range inspection of pipes. Such techniques still have many practical difficulties in application, however, due to the complex characteristics of guided waves such as dispersion and their multimodal nature. A defect imaging technique is developed in this study to overcome the complexities of guided wave inspection. Received signals are separated into single-mode waveforms with a mode extraction technique and then spatial waveforms on the pipe surface at an arbitrary time are reconstructed. The predicted waveforms can provide a defect image at the moment when an incident wave arrives at a defect region, which is based on a time-reversal technique. This defect imaging technique is experimentally verified using eight signals detected at eight different circumferential positions. Images of artificial defects are obtained with one-hole and two-hole test pipes, and increasing the frequency of incident waves increases the resolution of the images. Holes and pipe ends are recognizable in the images, but the reconstructed images contain some errors in the area behind the defects where guided waves do not propagate or do not reflect back to the receiving transducers.

Fundamental modal properties of surface waves on metamaterial grounded slabs

Abstract: This paper deals with the analysis of surface waves supported by a metamaterial layer on a ground plane, and investigates the potentiality of these grounded slabs as substrates for planar antennas. Both double- and single-negative media, either epsilon- or mu-negative, are considered. As is known, such structures may support two kinds of surface waves, i.e., ordinary (transversely attenuating only in air) and evanescent (transversely attenuating also inside the slab) surface waves. A graphical analysis is performed for proper real solutions of the dispersion equation for TE and TM modes, and conditions are presented that ensure the suppression of a guided-wave regime for both polarizations and kinds of wave. In order to demonstrate the feasibility of substrates with such desirable properties, numerical simulations based on experimentally tested dispersion models for the permittivity and permeability of the considered metamaterial media are reported. Moreover, the effects of slab truncation on the field radiated by a dipole source are illustrated by comparing the radiation patterns at different frequencies both in the presence and in the absence of surface waves. The reported results make the considered structures promising candidates as substrates for planar antennas and arrays with reduced edge-diffraction effects and mutual coupling between elements.

Rectangular waveguide with dielectric-filled corrugations supporting backward waves

Abstract: A new application for corrugated waveguides as left-handed (LH) meta-material guided-wave structures is investigated. The waveguide is operated below the cutoff of the dominant mode, where the waveguide has an inherent shunt inductance. The dielectric-filled corrugations are used to provide a series capacitance, which, along with the shunt inductance, create the necessary environment to support backward waves. A simple equivalent-circuit model is constructed, and proves quite accurate in determining the dispersion, as well as the scattering characteristics of the structure. Experimental verification of the occurrence of backward waves in the corrugated waveguide is presented. Very good agreement between the results obtained using the equivalent-circuit model and the full-wave finite-difference time-domain solution is achieved. The effect of the various design parameters on the LH propagation bandwidth is investigated. The advantages and possible applications of the structure are discussed.

Finite elements methods for modeling the guided waves propagation in structures with weak interfaces

Abstract: This paper describes two methods using a finite element (FE) code for modeling the effects of weak interfaces on the propagation of low-order Lamb modes. The variable properties of the interfaces are modeled by either a thin layer or a uniform repartition of compression and shear springs that insure the continuity of the stresses and impose a discontinuity in the displacement field. The method is tested by comparison with measurements that were presented in a previous paper [J. Acoust. Soc. Am. 113(6) 3161–3170 (2003)]. The interface was the contact between a rough elastomer with high internal damping loaded against one surface of a glass plate. Both normal and shear stiffnesses of the interface were quantified from the attenuation of A0 and S0 Lamb waves caused by leakage of energy from the plate into the elastomer and measured at each step of a compressive loading. The FE model is made in the frequency domain, thus allowing the viscoelastic properties of the elastomer to be modeled by using complex modu...

Ultrasonic inspection of multi-wire steel strands with the aid of the wavelet transform

Abstract: The non-destructive detection of structural defects in multi-wire strands used as post-tensioned tendons and cable stays is a challenging, yet critical task. A promising method under investigation is based on the use of ultrasonic stress waves that propagate within the strand and interact with structural discontinuities. The waveguide-like geometry of the strands lends itself to the monitoring of long lengths at a time (long range). The topic of this paper is the enhancement of ultrasonic monitoring of strands by a joint time–frequency analysis based on the discrete wavelet transform (DWT). The test set-up uses magnetostrictive sensors for the excitation and the detection of ultrasonic guided waves in the strands. The main advantage of the DWT is an unmatched de-noising performance. Effective de-noising becomes necessary for the detection of small defects located far away from the inspection probes as desirable in the field. When compared to the traditional signal averaging, the DWT can be used in real time owing to its computational efficiency. The theory of the DWT filter bank decomposition is first revised. The effectiveness of the wavelet processing is then demonstrated for the detection of small notches of varying depths located in the free portion of the strands as well as in the critical anchored areas. The study also shows the importance of selecting the proper mother wavelet function for best performance. The DWT proves effective in eliminating the need for signal averaging and in reducing the power supply required by the monitoring system. Both outcomes make the guided wave inspection method for strands more suitable for field use.

Flexural Torsional Guided Wave Mechanics and Focusing in Pipe

Abstract: Theoretical work on flexural torsional guided waves in pipe is presented along with angular profile experimental justification. Combined with previous work on flexural longitudinal modes and axisymmetric longitudinal and torsional modes, this work now forms a framework of nonuxisymmetric guided wave mechanics in pipe. Pipe inspection experiments are also carried out by flexural torsional. wave focusing to demonstrate the advantages of the focusing technique.

Modeling and experimental detection of damage in various materials using the pulse-echo method and piezoelectric sensors/actuators

Abstract: The application of guided wave techniques to nondestructively determine the structural integrity of various engineering materials, like alumina, laminated composites, and composite sandwiches, is presented. In particular, a combined theoretical, numerical, and experimental investigation of the fundamental aspects of the pulse-echo method using piezoelectric sensors and actuators is conducted. The dispersion effect of wave guides on these materials is first analyzed, and the transient propagation process of wave guides and its interaction with internal damage are then numerically simulated. The implementations of the pulse-echo method are illustrated in experimental testing and damage detection of aluminum beams, carbon/epoxy laminated composite plates, and composite sandwich beams. The effects of frequencies, wave forms, and types of piezoelectric material on the damage detection process are discussed, in consideration of locating damage in structures. As illustrated in this study, the pulse-echo method combined with piezoelectric material can be used effectively to locate damage in various engineering materials and structures.

Substrate integrated waveguide 180-degree narrow-wall directional coupler

Abstract: Substrate integrated waveguide (SIW) is a new type of guided wave structure which could be implemented in both microwave- and millimeter wave integrated circuits The study combines narrow-wall directional coupler with slow wave structure in SIW technique and achieved an over 54% bandwidth with /spl plusmn/03dB power equality, -20 dB isolation and 180 degrees phase shift between the output- and coupled ports as well for a coupler of length of 059 Its low cost and small size make it attractive for many narrowband applications

Defect Classification in Pipes by Neural Networks Using Multiple Guided Ultrasonic Wave Features Extracted After Wavelet Processing

Abstract: This paper casts pipe inspection by ultrasonic guided waves in a feature extraction and automatic classification framework. The specific defect under investigation is a small notch cut in an ASTM-A53-F steel pipe at depths ranging from 1% to 17% of the pipe cross-sectional area. A semi-analytical finite element method is first used to model wave propagation in the pipe. In the experiment, reflection measurements are taken and six features are extracted from the discrete wavelet decomposition of the raw signals and from the Hilbert and Fourier transforms of the reconstructed signals. A six-dimensional damage index is then constructed, and it is fed to an artificial neural network that classifies the size and the location of the notch. Overall, the wavelet-based multifeature analysis demonstrates good classification performance and robustness against noise and changes in some of the operating parameters.

Ultrasonic/Guided Waves for Structural Health Monitoring

Abstract: Structural damage detection and monitoring is one of the major maintenance activities in transportation, processing and civil engineering. Current procedures are based on scheduled inspections which are often time/labour consuming and expensive. Guided ultrasonic waves offer the ability of inspecting large structures with a small number of transducers. Recent developments in smart sensor technologies allow for integration of these transducers with monitored structures. This is associated with a new design philosophy leading to more efficient and economically attractive structures. The paper briefly discusses various damage detection methods based on structural, ultrasonic and guided ultrasonic waves. The focus is on recent research advances in damage monitoring techniques, smart sensor technologies and signal processing.

Goos-Hänchen and Imbert-Fedorov shifts for leaky guided modes

Abstract: The Goos-Hanchen shift for a light beam totally reflected on the external interface of a dielectric thin film deposited on a high-index substrate can be strongly enhanced through some specific incidence angles corresponding to the leaky guided modes into the layer. Because the resonant eigenstates are polarization dependent, it has been possible to observe such resonance with an experimental setup based on a periodic modulation of the polarization state combined with position-sensitive detection. Classical models usually used for a single interface (Artmann's model based on phase argument and Renard's model based on an energetic interpretation) have been re-adapted to describe the behavior of the entire layer. Good agreement is obtained between theory and experimental results.

Acquisition and Inversion of Dispersive Seismic Waves in Shallow Marine Environments

Abstract: Dispersive Scholte waves as well as acoustic guided waves have been excited by surface towed airguns and recorded with stationary receivers (OBS) and a towed hydrophone array. The inversion of the recorded wavefield spectra was adapted to the data from shallow marine environments. The dispersive interface wave travelling along the sea floor (Scholte Wave) is sensitive to the shear wave velocity (Vs) of the sediment and could be sucessfully recorded and inverted at different sites in Kiel Bay and the south-east rim of the Arkona Basin in the Baltic Sea. Limitations remain for very soft sediments with Vs < 50m/s. The acoustic guided wave is sensitive to density and compressional velocity (Vp) as well as Vs. Shear wave velocity and high resolution Vp information could be obtained from the inversion of this wave type in the central Arkona Basin, where very soft sediments (10-20m) overlaid the till and chalk layers, and no interface wave was observed. The lateral variation of the dispersion of Scholte waves was observed with the towed acquisition system, which could be suitable to effciently locate areas with a high shear wave velocity basement at shallow (0-100m) depth.

Control of planar nonlinear guided waves and spatial solitons with a left-handed medium

Abstract: The evidence that double-negative media, with an effective negative permittivity and an effective negative permeability, can be manufactured to operate at frequencies ranging from microwave to optical is ushering in a new era of metamaterials. They are referred to here as 'left handed', even though a variety of names is evident from the literature. In anticipation of a demand for highly structured integrated practical waveguides, this paper addresses the impact of this type of medium upon waveguides that can be also nonlinear. After an interesting historical overview and an exposure of some straightforward concepts, a planar guide is investigated, in which the waveguide is a slab consisting of a left-handed medium sandwiched between a substrate and cladding that are simple dielectrics. The substrate and cladding display a Kerr-type nonlinear response. Because of the nonlinear properties of the Kerr media, the power flow direction can be controlled by the intensity of the electric field. A comprehensive finite-difference-time-domain (FDTD) analysis is presented that concentrates upon spatial soliton behaviour. An interesting soliton-lens arrangement is investigated that lends itself to a novel cancellation effect.

Investigation of the phase velocities of guided acoustic waves in soft porous layers

Abstract: A new experimental method for measuring the phase velocities of guided acoustic waves in soft poroelastic or poroviscoelastic plates is proposed. The method is based on the generation of standing waves in the material and on the spatial Fourier transform of the displacement profile of the upper surface. The plate is glued on a rigid substrate so that it has a free upper surface and a nonmoving lower surface. The displacement is measured with a laser Doppler vibrometer along a line corresponding to the direction of propagation of plane surface waves. A continuous sine with varying frequencies was chosen as excitation signal to maximize the precision of the measurements. The spatial Fourier transform provides the wave numbers, and the phase velocities are obtained from the relationship between wave number and frequency. The phase velocities of several guided modes could be measured in a highly porous foam saturated by air. The modes were also studied theoretically and, from the theoretical results, the experimental results, and a fitting procedure, it was possible to determine the frequency behavior of the complex shear modulus and of the complex Poisson ratio from 200 Hz to 1.4 kHz, in a frequency range higher than the traditional methods.

Calculation of the Response of a Composite Plate to Localized Dynamic Surface Loads Using a New Wave Number Integral Method

Abstract: This study is motivated by the need for an efficient and accurate tool to analyze the wavefield produced by localized dynamic sources on the surface or the interior of isotropicplates and anisotropic composite laminates. A semi-analytical method based on the wavenumber integral representation of the elastodynamic field is described that reduces theoverall computational effort significantly over other available methods. This method isused to calculate the guided wave field produced in a thin unidirectional graphite/epoxycomposite laminate by a dynamic surface point load. The results are compared with thoseobtained from a finite element analysis, showing excellent agreement, except for minordifferences at higher frequencies. A recently discovered feature of the calculated surfacemotion, namely, a spatially periodic ‘‘phase reversal’’of the main pulse with propagationdistance, is observed in both cases. The present work is expected to be helpful in devel-oping impact damage monitoring systems in defect-critical structural components throughreal time analysis of acoustic emission wave forms. @DOI: 10.1115/1.1828064#