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Showing papers on "Guided wave testing published in 2006"


Proceedings ArticleDOI
TL;DR: In this article, a semi-analytical finite element (SAFE) method for modeling wave propagation in waveguides of arbitrary cross-section is proposed, and the dispersive solutions are obtained in terms of phase velocity, group velocity, energy velocity, attenuation and cross-sectional mode shapes.

534 citations


Proceedings ArticleDOI
01 Sep 2006
TL;DR: In this article, a new guided wave structure of half mode substrate integrated waveguide (HMSIW) for microwave and millimeter wave application is proposed for the first time.
Abstract: In this paper, a new guided wave structure of half mode substrate integrated waveguide (HMSIW) for microwave and millimeter wave application is proposed for the first time. The principle of the HMSIW is described, and its propagation characteristics are simulated and measured. The measured results at microwave and millimeter wave bands show that the attenuation of it is less than that of conventional microstrip and even SIW, but its size is nearly half of a SIW. Thus, we can further compress the size of a microwave or millimeter wave integrated circuit based on this new guided wave structure.

380 citations


Journal ArticleDOI
TL;DR: Integrated structures that will allow for improvements of current signal-processing functions as well as the implementation of novel device concepts are presented.
Abstract: The authors present a review of all-optical signal-processing technologies based on /spl chi//sup (2)/ nonlinear interactions in guided-wave devices and their applications for telecommunication. In this study, the main focus is on three-wave interactions in annealed proton-exchanged periodically poled lithium niobate waveguides due to their suitable properties with respect to nonlinear mixing efficiency, propagation loss, and ease of fabrication. These devices allow the implementation of advanced all-optical signal-processing functions for next-generation networks with signal bandwidths beyond 1 THz. In this paper, integrated structures that will allow for improvements of current signal-processing functions as well as the implementation of novel device concepts are also presented.

246 citations


Journal ArticleDOI
TL;DR: In this article, a structural health monitoring system based on the excitation and reception of guided waves using piezoelectric elements as sensors is described, and the baseline subtraction approach is used to detect defects in a simple rectangular plate.
Abstract: It is desirable for any structural health monitoring (SHM) system to have maximum sensitivity with minimum sensor density. The structural health monitoring system described here is based on the excitation and reception of guided waves using piezoelectric elements as sensors. One of the main challenges faced is that in all but the most simple structures the wave interactions become too complex for the time domain signals to be interpreted directly. One approach to overcoming this complexity is to subtract a baseline reference signal from the measured system when it is known to be defect free. This strategy enables changes in the structure to be identified. Two key issues must be addressed to allow this paradigm to become a reality. First, the system must be sufficiently sensitive to small reflections from defects such as cracking. Second, it must be able to distinguish between benign changes and those due to structural defects. In this paper the baseline subtraction approach is used to detect defects in a simple rectangular plate. The system is shown to work well in the short term, and good sensitivity to defects is demonstrated. The performance degrades over the medium to long term. The principal reason for this degradation is shown to be the effect of change in temperature of the system. These effects are quantified and strategies for overcoming them are discussed.

240 citations


Journal ArticleDOI
TL;DR: The prototype of a guided ultrasonic wave array for the structural integrity monitoring of large, plate-like structures has been designed, built, and tested, and the sensitivity of the array device for defect detection has been established.
Abstract: The prototype of a guided ultrasonic wave array for the structural integrity monitoring of large, plate-like structures has been designed, built, and tested. The development of suitably small transducers for the excitation and measurement of the first antisymmetric Lamb wave mode A/sub 0/ is described. The array design consists of a ring of 32 transducers, permanently bonded to the structure with a protective membrane, in a compact housing with the necessary multiplexing electronics. Using a phased addition algorithm with dispersion compensation and deconvolution in the wavenumber domain, a good dynamic range can be achieved with a limited number of transducers. Limitations in the transducer design and manufacture restricted the overall dynamic range achieved to 27 dB. Laboratory measurements for a steel plate containing various defects have been performed. The results for standard defects are compared to theoretical predictions and the sensitivity of the array device for defect detection has been established. Simulated corrosion pitting and a defect cut with an angle grinder simulating general corrosion were detected.

149 citations


Journal ArticleDOI
TL;DR: In this article, an effective model of surface-bounded flat PZT disks based on effective force, moment and displacement is developed for Lamb wave excitation, collection and propagation in isotropic plate and quasi-isotropic laminated composite.

120 citations


Journal ArticleDOI
TL;DR: Theoretical dispersion curves and wave structures for a bar with an arbitrary cross-section are derived in this paper using a special modeling technique called the semi-analytical finite element method (SAFEM).

112 citations


Journal ArticleDOI
TL;DR: The approximate analytical algorithms presented in this paper provides a convenient method enabling quick acoustic field analysis on large-diameter industrial pipes for NDE applications and predicts that the wave beam will converge to its original circumferential shape after the wave propagates for a certain distance.

105 citations


Journal ArticleDOI
TL;DR: The proposed damage detection methodology can be used successfully to localise the damage location, however, as expected, the localisation is strongly affected by the frequency range used.

76 citations


Journal ArticleDOI
TL;DR: In this article, a new compact sensor configuration comprising a single transmitter and multi-receivers (STMR) is presented for the in situ structural health monitoring (SHM) of large plate-like isotropic structures.
Abstract: A new compact sensor configuration comprising a single transmitter and multi-receivers (STMR) is presented for the in situ structural health monitoring (SHM) of large plate-like isotropic structures. The STMR exploits the long-range propagation characteristics of ultrasonic guided Lamb waves and a phase reconstruction algorithm to provide defect detection and location capability under non-dispersive as well as dispersive regimes of guided waves. Simulations are performed on defect-free and defective finite plates of aluminum to demonstrate the various features of the STMR system. Experiments were carried out on 1 mm thick aluminum plates initially using a pair of individual sensors and subsequently using a prototype STMR array. The simulated results of the STMR performance were validated well through these experiments. Features of the STMR system such as its small footprint, the relatively simple data acquisition and processing discussed here have applications in the SHM of plate-like structures, and particularly of aerospace structures.

74 citations


Journal ArticleDOI
TL;DR: In this article, the dispersion properties of the guided modes propagating along a dielectric slab waveguide with a left-handed material substrate are studied and it is shown that both the oscillating and surface modes can propagate very slowly along such a waveguide if the thickness of the core layer is chosen appropriately.
Abstract: The dispersion properties of the guided modes propagating along a dielectric slab waveguide with a left-handed material substrate are studied. It is shown that both the oscillating and surface modes can propagate very slowly along such a waveguide if the thickness of the core layer is chosen appropriately. The propagation speed of the guided waves can even approach zero and this slow propagation is illustrated with an finite-difference time-domain simulation in a tapered waveguide. The influence of the material loss on the slow propagation is also discussed.

Journal ArticleDOI
TL;DR: In this paper, the experimental results clearly show that elastic waves can propagate through the corrugated plate (waveguide) for certain frequencies called pass bands, and find it difficult to propagate for some other frequencies called stop bands.
Abstract: Nonplanar surfaces are often encountered in engineering structures. In aerospace structures, periodically corrugated boundaries are formed by friction-stir-welding. In civil engineering structures, rebars used in reinforced concrete beams and slabs have periodic surface. Periodic structures are also being used to create desired acoustic band gaps. For health monitoring of these structures, a good understanding of the elastic wave propagation through such periodic structures is necessary. Although a number of research papers on the wave propagation in periodic structures are available in the literature, no one experimentally investigated the guided wave propagation through plates with periodic boundaries and compared the experimental results with theoretical predictions as done in this paper. The experimental results clearly show that elastic waves can propagate through the corrugated plate (waveguide) for certain frequencies called “pass bands,” and find it difficult to propagate for some other frequencies called “stop bands.” Stop bands are found to increase with the degree of corrugation. Experimental results are compared with the theoretical predictions, and good matching is observed for plates with small degree of corrugation. Only two parameters—the depth of corrugation and the wavelength of the periodicity—are sufficient for modeling the elastic wave propagation in slightly corrugated plates.

Proceedings ArticleDOI
16 Mar 2006
TL;DR: In this article, a chirplet matching pursuit algorithm was proposed to isolate individual reflections from defects in the structure and estimate the time-frequency centers, the modes and individual energies of the reflections, which would be used to locate and characterize defects.
Abstract: Signal processing algorithms for guided wave pulse echo-based SHM must be capable of isolating individual reflections from defects in the structure, if any, which could be overlapping and multimodal. In addition, they should be able to estimate the time-frequency centers, the modes and individual energies of the reflections, which would be used to locate and characterize defects. Finally, they should be computationally efficient and amenable to automated processing. This work addresses these issues with a new algorithm employing chirplet matching pursuits followed by a mode correlation check for single point sensors. Its theoretical advantages over conventional time-frequency representations in all aspects are elaborated and these are demonstrated using numerical simulations and experiments in isotropic plate structures. The issue of in-plane triangulation is then discussed and experimental work done to explore this issue is presented. This work concludes with a description of how the algorithm can be extended to composite plate structures.

Journal ArticleDOI
TL;DR: In this article, an alternating magnetic field by a figure-of-eight coil is applied to a circular magnetostrictive patch bonded to a plate, ultrasonic guided waves can be effectively generated and measured.
Abstract: When an alternating magnetic field by a figure-of-eight coil is applied to a circular magnetostrictive patch bonded to a plate, ultrasonic guided waves can be effectively generated and measured. Wave experiments with two transducers consisting of the coil and the patch show that the magnitude and type of the measured waves depend on the magnetic field directions of the wave transmitting and receiving coils; a first-order theory was derived to explain the direction-dependent phenomena. The relation between the patch size and the frequency of the maximum signal output was also investigated.

Journal ArticleDOI
TL;DR: In this paper, an experimental investigation on the ultrasonic wave propagation in seven-wire strands loaded at different stress levels is presented, where Wafer piezoelectric sensors are employed in a through transmission configuration for the generation and detection of stress waves.
Abstract: In recent years methods based on guided ultrasonic waves gained increasing attention for the nondestructive evaluation and the health monitoring of multi-wire strands used in civil structures as prestressing tendons and stay cables. The study of wave propagation properties in such components has been challenging due to the load-dependent inter-wire contact and the helical geometry of the peripheral wires. The present paper addresses an experimental investigation on the ultrasonic wave propagation in seven-wire strands loaded at different stress levels. Wafer piezoelectric sensors are employed in a through transmission configuration for the generation and detection of stress waves. The response of the lowest-order longitudinal mode is studied at different levels of load. Those ultrasonic features, associated with the transmitted ultrasonic energy, sensitive to the variation of applied load are identified and discussed as possible means of a load monitoring.

Proceedings ArticleDOI
TL;DR: In this article, three different synthetically focused imaging algorithms for a linear array aperture: CSM (Common Source Method), SAFT (Synthetic Aperture Focusing Technique) and TFM (Total Focusing Method).
Abstract: Synthetically focused imaging has been used for some time in the NDE community. The techniques have primarily been directed towards imaging using bulk waves. There has recently been use of SAFT (Synthetic Aperture Focusing Technique) using guided waves in plates. Here, we review three different synthetically focused imaging algorithms for a linear array aperture: CSM (Common Source Method), SAFT and TFM (Total Focusing Method). The resolution of the different techniques is obtained from scalar diffraction theory and then validated by means of a low frequency (50kHz) steel plate experiment using PZT excitation and laser reception of the A0 mode. Imaging of through thickness slits parallel to the array is then discussed.

Journal ArticleDOI
TL;DR: The objective of this study is to develop an efficient technique to deal with dispersed pulses by chirp functions of special form that can simulate up to quadratically varying group delay for guided-wave nondestructive evaluation.
Abstract: If the wave mode used in guided wave non-destructive inspection is dispersive, reflected pulses from damaged parts may be significantly distorted due to wave dispersion. The main concern, in this case, is how to detect the reflected pulses in noisy signals, and to extract meaningful damage information from the detected pulses. However, current signal processing techniques used for guided wave inspection do not account for pulse dispersion, so the extracted information is often not so accurate. The objective of this study is to develop an efficient technique to deal with dispersed pulses for guided-wave nondestructive evaluation. Our idea is to model dispersed pulses by chirp functions of special form that can simulate up to quadratically varying group delay. To determine the parameters of the chirp functions approximating dispersed, reflected pulses, an adaptive matching pursuit algorithm is employed. Once the characterizing parameters are found, the damage location and extent can be estimated. The proposed method is tested with experimentally measured signals of longitudinal waves in a circular cylinder.

Journal ArticleDOI
TL;DR: In this article, the results of experiments carried out to study the identification of damage using Bragg grating sensors as ultrasonic receivers of Lamb waves are given, where the experiments involve a rectangular aluminium plate and damage was introduced into the plate by drilling a hole into the center of the plate.
Abstract: Damage detection is an important issue in structural health monitoring. Lamb waves are the most widely used acousto-ultrasonic guided waves for damage detection. This paper gives the results of experiments carried out to study the identification of damage using Bragg grating sensors as ultrasonic receivers of Lamb waves. The experiments involve a rectangular aluminium plate. Damage was introduced into the plate by drilling a hole into the centre of the plate. In order to obtain different severity of damage, the hole diameter was increased step by step. Several signal processing tools are presented and then applied to the Lamb wave signals in order to find a parameter that corresponds to the severity of damage. The parameter that serves as the damage index has to have small cross-sensitivity to other physical parameters, e.g. temperature. Therefore, additional experiments have been carried out to study the temperature dependence of the Lamb wave signals. In order to determine the influence of the temperature on the damage detection results, the cross-sensitivity is studied within this paper.

Journal ArticleDOI
TL;DR: In this article, a novel spectroscopy technique that uses parallel-plate waveguides for the characterisation of highly conductive materials in the terahertz (THz) frequency regime is presented.
Abstract: A novel spectroscopy technique that uses parallel-plate waveguides for the characterisation of highly conductive materials in the terahertz (THz) frequency regime is presented. This guided-wave technique resolves some of the fundamental problems associated with standard THz time-domain spectroscopy (THz-TDS) as applied to these optically dense materials. The technique is demonstrated by measuring the conductivity of highly phosphorus doped silicon.

Journal ArticleDOI
TL;DR: In this paper, the scattering of the fundamental guided torsional mode by a local axisymmetrical layer coated inside a pipe, referred to as a bilayered pipe, was studied.
Abstract: The scattering of the fundamental guided torsional mode by a local axisymmetrical layer coated inside a pipe, referred to as a bilayered pipe, is studied. In a prescribed frequency range, the number of torsional modes which can propagate in an empty pipe is increased by the presence of the coating layer, including new cutoff frequencies that depend on the layer thickness and shear acoustic properties. This principle suggests the potential for detecting, and perhaps characterizing layers inside pipes, which may be exploited in two ways using either remote or local measurements. A remote measurement may be employed to measure the reflection from the entry point of the layer inside the pipe. Such a measurement shows that the reflection coefficient spectrum exhibits periodic maxima that occur at the cutoff frequencies of the torsional modes in the bilayered pipe. On the other hand, when the location of the coating layer is accessible, the local guided wave measurement can be made to measure the dispersion cur...

Journal ArticleDOI
TL;DR: The propagation phenomena of guided waves in a bended pipe were investigated using a wideband laser ultrasonic system and indicated the amplitude of the F(1,1) mode converted from the L(0, 1) mode increased with the increase of the bending angle.

Journal ArticleDOI
TL;DR: In this paper, a nonlinear Mach-Zehnder interferometer based on photonic-crystal waveguides is proposed and modeled by using rigorous finite-element-based numerical scheme.
Abstract: A nonlinear Mach-Zehnder interferometer based on photonic-crystal waveguides is proposed and modeled by using rigorous finite-element-based numerical scheme. Guided modes of nonlinear photonic-crystal waveguides are investigated to determine a length of nonlinear arm and a switching power, and further, intensity-dependent switching characteristics of the nonlinear Mach-Zehnder interferometer, for the first time, as far as the authors know, are demonstrated. Effects of saturable nonlinearity and two-photon absorption (TPA) on switching characteristics are also taken into account.

Journal ArticleDOI
TL;DR: In this article, the existence of homoclinic solutions to the origin in a Schrodinger equation with a nonlinear term was proved using a Krasnoselskii fixed point theorem together with a compactness criterion due to Zima.
Abstract: Motivated by the study of the propagation of electromagnetic waves through a multi-layered optical medium, we prove the existence of two different kinds of homoclinic solutions to the origin in a Schrodinger equation with a nonlinear term. We use a Krasnoselskii fixed point theorem together with a compactness criterion due to Zima. The main results are illustrated with concrete examples of practical interest such as self-focusing nonlinearities of Kerr and non-Kerr type.

Proceedings ArticleDOI
TL;DR: In this article, a number of tomographic and phased array methods have been proposed for generating two dimensional images of plate-like structures using sparse arrays of spatially distributed ultrasonic transducers.
Abstract: A number of tomographic and phased‐array methods have been proposed for generating two dimensional images of plate‐like structures using sparse arrays of spatially distributed ultrasonic transducers. The phased array differential approach is considered here whereby pulse echo and through transmission signals are recorded before and after localized damaged is introduced, and differenced signals are combined using a focusing rule to produce an image of the plate. The application is structural health monitoring where the transducers are permanently bonded to the structure. The quality of the image is affected by many factors such as the number and location of the transducers, the characteristics of the damage, the signal‐to‐noise ratio, presence of edge reflections, and anything unrelated to damage that may perturb the ultrasonic signals such as temperature changes and transducer bonding variations. Two methods for enhancing image quality are implemented and then evaluated as to their effectiveness. In the first method, the windowing function is changed in width prior to phased signal addition to yield the best image quality. In the second method, signals are envelope‐detected prior to phased signal addition to eliminate phasing artifacts. Results are reported for artificial defects introduced in aluminum plates.

Journal ArticleDOI
TL;DR: In this article, the authors investigate the geometry of deep subduction zone waveguides (depth > 100 km) and compare the wavefield characteristics for up-dip profiles with data recorded at the Chile-Peru subduction zones.
Abstract: SUMMARY We investigate the geometry of deep subduction zone waveguides (depth >100 km). The wavefield characteristics for up-dip profiles are described and compared with data recorded at the Chile–Peru subduction zone. Observed distorted P onsets at stations in northern Chile near 21°S can be matched by 2-D finite difference simulations of a thin low-velocity layer (LVL) atop the slab in an IASP91 velocity model. The replacement of the LVL by simple random velocity undulations in the slab in the same model cannot explain the observations. Varying slab geometries are investigated and the distribution of guided wave onsets originating in deep waveguides is predicted relative to the slab surface. Further, double couple source position and orientation is explored and found to be closely limited by the guided wave observations. Sources situated above the layer and at distances more than 2 layer widths below the subducted Moho are not suitable. For the remaining favourable source locations, a strong link between pulse shapes and fault plane dip angle is evident. We conclude that up-dip guided wave observations at subduction zones follow a simple pattern given by slab geometry and modified by source position. The resulting onsets are shaped by layer thickness and velocity contrast and further influenced by the shape of the slab surface.

Journal ArticleDOI
TL;DR: In this paper, a single-layer guided-mode resonance (GMR) filter based on a free-standing silicon-nitride membrane suspended on a silicon substrate is achieved by using bulk-micromachining technology.
Abstract: In this paper, a single-layer guided-mode resonance (GMR) filter based on a free-standing silicon-nitride membrane suspended on a silicon substrate is achieved by using bulk-micromachining technology. Both of grating and waveguide structures without a lower-cladding layer, i.e., substrate, are fabricated simultaneously on a silicon-nitride membrane. The device can be used as a transmission bandstop filter with the advantages of simple structure, high efficiency, and feasibility to integrate with other optoelectronic elements into a microsystem chip. The design consideration, fabrication procedures, and measured spectral response are shown in this paper. Moreover, by stacking two proposed devices, /spl Delta//spl lambda/ of the stopband at a transmission below 10% is 5.06 nm.

Journal ArticleDOI
TL;DR: The objective of this study is to understand the role of residual stress in piezoelectric layers in order to predict the performance of integrated structures in thick or thin film technology.
Abstract: The objective of this study is to understand the role of residual stress in piezoelectric layers in order to predict the performance of integrated structures. This is of particular importance in thick or thin film technology. Considering a bulk piezoelectric material, the Christoffel equation for a piezoelectric material is modified to take into account a uniform residual stress on a given cross section. A numerical study of its influence is carried out on the slowness curves and coupling coefficients of a lithium niobate material. In a second part, modified Christoffel tensor is used to calculate the dispersion curves of Lamb waves in a piezoelectric plate. The Lamb modes are found to be sensitive to the residual stress. In particular, it is shown how the behavior of the first Lamb modes is modified with residual stress. In a third part, these results are extended to a piezoelectric film laid down on a substrate in order to model the importance of these phenomena on the behavior of an integrated structure. The numerical study of guided waves in a lithium niobate plate is performed first, then the case of a lithium niobate film laid down on a silicon substrate is considered.

Journal ArticleDOI
Y. Cui1, D.H. Zou1
TL;DR: In this article, an 800 mm partially grouted cylindrical rock bolt model was created to study the behavior of the guided ultrasonic wave propagating inside the grouted bolt along its central axis.

Journal ArticleDOI
TL;DR: Experiments carried out with a nanosecond narrow-bandwidth, high-power fiber source thoroughly explored the response of the nonlinear photonic crystal device in terms of its power, wavelength, and angle tunability.
Abstract: We demonstrate twin-beam second-harmonic generation from telecommunications wavelengths in an optimized buried reverse proton exchanged planar waveguide made in 2D hexagonally poled LiNbO3. Experiments carried out with a nanosecond narrow-bandwidth, high-power fiber source thoroughly explored the response of the nonlinear photonic crystal device in terms of its power, wavelength, and angle tunability.

21 Apr 2006
TL;DR: In this paper, a general version of coupledmode theory for frequency-domain scattering problems in integrated optics is proposed, which typically combines modes of the optical channels in the structure with coefficient functions of in principle arbitrary coordinates.
Abstract: In this paper, a general version of coupled-mode theory for frequency-domain scattering problems in integrated optics is proposed. As a prerequisite, a physically reasonable field template is required, that typically combines modes of the optical channels in the structure with coefficient functions of in principle arbitrary coordinates. Upon 1D discretizations of these amplitude functions into finite elements, a Galerkin procedure reduces the problem to a system of linear equations in the element coefficients, where given input amplitudes are included. Smooth approximate solutions are obtained by solving the system in a least squares sense. The versatility of the approach is illustrated by means of a series of 2D examples, including a perpendicular crossing of waveguides, and a grating-assisted rectangular resonator. As an Appendix, we show that, alternatively, a similar procedure can be derived by variational means, i.e., by restricting a suitable functional representation of the full 2D/3D vectorial scattering problem (with transparent influx boundary conditions for inhomogeneous exterior) to the respective field templates.