Tesis: "Guided ultrasonic waves"

1

Pavlakovic, Brian Nicholas. "Leaky guided ultrasonic waves in NDT". Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/7907.

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2

Bartoli, Ivan. "Structural health monitoring by ultrasonic guided waves". Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3283893.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed December 3, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 311-325).

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3

Ghandourah, E. I. I. "Large plate monitoring using guided ultrasonic waves". Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1463979/.

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Areas of stress concentration around welded structures are likely to lead to fatigue cracks and corrosion pitting during the life time of technical machinery. Performing periodical non-destructive testing of the critical area is crucial for the maintenance of structural integrity and the prevention of unforeseen shutdowns of the system. Low frequency guided ultrasonic waves can propagate along thin structures and allow for the efficient testing of large components. Structural damage can be localized using a distributed array of guided ultrasonic wave sensors. Guided waves might be employed to overcome the accessibility problem for stiffened plate structures where access to some parts of the inspected structure is not possible. The transmission and reflection of the A0 Lamb wave mode for a variation of the stiffener geometry and excitation frequency was investigated numerically and verified experimentally. The dispersive behaviour of the guided waves has been studied to ascertain a frequency thickness product that provides limited pulse distortion. The limitations of the plate geometry as well as the excitation and monitoring locations were discussed. The radial spreading of the incident, transmitted and reflected waves from a stiffener has been investigated. The efficient quantification of the transmitted and reflected waves from the stiffener for a wide range of angles has been obtained from a single Finite Element model containing two parallel lines of nodes in front of and past the stiffener. The research outcomes have shown the dependency of the scattered wave on the incident angle and stiffener dimensions. Reasonably good A0 wave mode transmission was obtained from the oblique wave propagation (up to an angle of 45o) across realistic stiffener geometries. The choice of an optimum excitation frequency, which can ensure maximum transmission across the stiffener for specific plate geometry, was recommended. The ability for defect detection in inaccessible areas has been investigated numerically and validated experimentally. The possibility of detecting and characterizing the reflection of a guided wave pulse (A0 mode) from a through-thickness notch located behind the stiffener has been discussed. Two different approaches, based on the access to the sides of the stiffener on the plate, were employed. The limitations of the detectable defect size and location behind the stiffener have been investigated. The energy of the transmitted wave across the stiffener was adequate to detect simulated damage behind the stiffener. The evaluation has shown that defect detection in inaccessible areas behind stiffeners is achievable if the signal-to-noise ratio is high enough. In experimental measurements the noise level was of similar magnitude to the observed reflections at the defect. Thus, there is necessity to enhance the signal-to-noise ratio in experimental measurements.

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4

Vallet, Quentin. "Predicting bone strength with ultrasonic guided waves". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066626.

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Cette thèse s'inscrit dans le cadre du développement d'une sonde ultrasonore afin d'obtenir des nouveaux biomarqueurs de l'os cortical et améliorer la prédiction du risque de fracture. Notre approche se base sur la mesure des ondes guidées ultrasonores dans l'os cortical. La technique de transmission axiale bidirectionelle a été utilisée pour mesurer les modes guidées se propageant dans l'enveloppe corticale des os longs (i.e., le radius). Les propriétés matérielles et structurelles liées à la résistance osseuse ont été obtenues à partir des courbes de dispersion en utilisant un schéma d'inversion. Ainsi, un problème inverse totalement automatique, basé sur une optimisation par algorithmes génétiques et un modèle 2D de plaque libre transverse isotrope, a été développé. Cette procédure d'inversion a d'abord été testée sur des matériaux contrôlés avec des propriétés connues. Puis, la faisabilité d'obtenir des propriétés corticales sur des radii ex vivo a été montrée. Ces estimations ont été validées par comparaison avec des valeurs de référence obtenues avec des techniques indépendantes telles que la micro-tomodensitométrie par rayons X (épaisseur, porosité) et la spectroscopie par résonance ultrasonore (élasticité). Un bon accord a été trouvé entre les valeurs de référence et les estimations d'épaisseur, de porosité et d'élasticité. Enfin, la méthode a été étendue à des mesures in vivo. La validité du modèle en présence de tissus mous a d'abord été démontrée. Puis, les propriétés osseuses ont été obtenues sur des sujets sains. Un bon accord a été trouvé entre l'épaisseur estimée et les valeurs de référence obtenues par tomodensitométrie périphérique haute résolution
We aimed at developing new ultrasound-based biomarkers of cortical bone to enhance fracture risk prediction in osteoporosis. Our approach was based on the original concept of measuring ultrasonic guided waves in cortical bone. The bi-directional axial transmission technique was used to measure the guided modes propagating in the cortical envelope of long bones (i.e., the radius). Strength-related structural and material properties of bone were recovered from the dispersion curves through an inversion scheme. To this goal, a fully automatic inverse problem based on genetic algorithms optimization, using a 2-D transverse isotropic free plate waveguide model was developed. The proposed inverse procedure was first tested on laboratory-controlled measurements performed on academic samples with known properties. Then, the feasibility of estimating cortical properties of ex vivo radius specimens was assessed. The inferred bone properties were validated by face-to-face comparison with reference values determined by a set of independent state-of-the art technologies, including X-ray micro-computed tomography (thickness, porosity) and resonance ultrasound spectroscopy (stiffness). A good agreement was found between reference values and estimates of thickness, porosity and stiffness. Lastly, the method was extended to in vivo measurements, first, by ensuring the validity of the waveguide model in presence of soft tissues to demonstrate the feasibility of measuring experimental dispersion curves in vivo and infer from them bone properties. Estimated cortical thickness values were consistent with actual values derived from high resolution peripheral computed tomography

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5

Vallet, Quentin. "Predicting bone strength with ultrasonic guided waves". Electronic Thesis or Diss., Paris 6, 2016. http://www.theses.fr/2016PA066626.

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Cette thèse s'inscrit dans le cadre du développement d'une sonde ultrasonore afin d'obtenir des nouveaux biomarqueurs de l'os cortical et améliorer la prédiction du risque de fracture. Notre approche se base sur la mesure des ondes guidées ultrasonores dans l'os cortical. La technique de transmission axiale bidirectionelle a été utilisée pour mesurer les modes guidées se propageant dans l'enveloppe corticale des os longs (i.e., le radius). Les propriétés matérielles et structurelles liées à la résistance osseuse ont été obtenues à partir des courbes de dispersion en utilisant un schéma d'inversion. Ainsi, un problème inverse totalement automatique, basé sur une optimisation par algorithmes génétiques et un modèle 2D de plaque libre transverse isotrope, a été développé. Cette procédure d'inversion a d'abord été testée sur des matériaux contrôlés avec des propriétés connues. Puis, la faisabilité d'obtenir des propriétés corticales sur des radii ex vivo a été montrée. Ces estimations ont été validées par comparaison avec des valeurs de référence obtenues avec des techniques indépendantes telles que la micro-tomodensitométrie par rayons X (épaisseur, porosité) et la spectroscopie par résonance ultrasonore (élasticité). Un bon accord a été trouvé entre les valeurs de référence et les estimations d'épaisseur, de porosité et d'élasticité. Enfin, la méthode a été étendue à des mesures in vivo. La validité du modèle en présence de tissus mous a d'abord été démontrée. Puis, les propriétés osseuses ont été obtenues sur des sujets sains. Un bon accord a été trouvé entre l'épaisseur estimée et les valeurs de référence obtenues par tomodensitométrie périphérique haute résolution
We aimed at developing new ultrasound-based biomarkers of cortical bone to enhance fracture risk prediction in osteoporosis. Our approach was based on the original concept of measuring ultrasonic guided waves in cortical bone. The bi-directional axial transmission technique was used to measure the guided modes propagating in the cortical envelope of long bones (i.e., the radius). Strength-related structural and material properties of bone were recovered from the dispersion curves through an inversion scheme. To this goal, a fully automatic inverse problem based on genetic algorithms optimization, using a 2-D transverse isotropic free plate waveguide model was developed. The proposed inverse procedure was first tested on laboratory-controlled measurements performed on academic samples with known properties. Then, the feasibility of estimating cortical properties of ex vivo radius specimens was assessed. The inferred bone properties were validated by face-to-face comparison with reference values determined by a set of independent state-of-the art technologies, including X-ray micro-computed tomography (thickness, porosity) and resonance ultrasound spectroscopy (stiffness). A good agreement was found between reference values and estimates of thickness, porosity and stiffness. Lastly, the method was extended to in vivo measurements, first, by ensuring the validity of the waveguide model in presence of soft tissues to demonstrate the feasibility of measuring experimental dispersion curves in vivo and infer from them bone properties. Estimated cortical thickness values were consistent with actual values derived from high resolution peripheral computed tomography

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6

Valle, Christine. "Guided circumferential waves in annular structures". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/17271.

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7

Belanger, Pierre. "Feasibility of thickness mapping using ultrasonic guided waves". Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/5503.

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Detection and sizing of corrosion in pipelines and pressure vessels over large, partially accessible areas is of growing interest in the petrochemical and nuclear industries. Traditionally, conventional ultrasonic thickness gauging and eddy current techniques have been used to precisely measure the thickness in structures. These techniques only allow the measurement of the local thickness under the probe. Consequently obtaining the remnant thickness of a specimen over a large area requires the probe to be scanned, which is a long and tedious process. Moreover, with these techniques, the scanning may become impossible when the area of inspection is inaccessible. There is therefore a need for a rapid, accurate, long range inspection technique to measure the remaining thickness in corrosion patches. Low frequency guided waves are now routinely used to screen large area of pipes and other structures for cracks and corrosion. Their detection and location capability is very good, but the standard screening technique only gives a rough estimate of the remaining wall thickness. Guided waves have multiple properties which can be used for thickness mapping over large partially accessible areas e.g. dispersion and cutoff frequency thickness product of the high order modes. The present work aims to demonstrate the potential of guided waves for thickness mapping over large partially accessible areas. It starts with a general introduction on ultrasonic guided waves and a literature review of the different techniques for the evaluation of thickness with guided waves. The severity of the errors introduced in time-of-flight tomography for thickness reconstruction by breaking the assumption of the ray theory are investigated. As these errors are significant, the possibility of using the cutoff property of the high order modes is investigated in a frequency range where the ray theory is valid. It is found that the attenuation due to the scattering of the waves in corrosion is too large for this technique to work. Finally the use of low frequency guided wave for diffraction tomography is examined. Finite element simulations of a 64 element circular array on a plate show that when the scattering mechanism of the object to be reconstructed satisfies the Born approximation the reconstruction of the thickness is accurate. However the practical implementation is more challenging when the incident field is not known. Experimental results demonstrate that ultimately the scattering from the array of transducer is a major source of error in the tomographic reconstruction, but when there is no scattering from the array of transducers the reconstructions are very similar to the finite element simulations.

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8

Buys, B. J. "Rock bolt condition monitoring using ultrasonic guided waves". Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-06222009-135318/.

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9

Levine, Ross M. "Ultrasonic guided wave imaging via sparse reconstruction". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51829.

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Structural health monitoring (SHM) is concerned with the continuous, long-term assessment of structural integrity. One commonly investigated SHM technique uses guided ultrasonic waves, which travel through the structure and interact with damage. Measured signals are then analyzed in software for detection, estimation, and characterization of damage. One common configuration for such a system uses a spatially-distributed array of fixed piezoelectric transducers, which is inexpensive and can cover large areas. Typically, one or more sets of prerecorded baseline signals are measured when the structure is in a known state, with imaging methods operating on differences between follow-up measurements and these baselines. Presented here is a new class of SHM spatially-distributed array algorithms that rely on sparse reconstruction. For this problem, damage over a region of interest (ROI) is considered to be sparse. Two different techniques are demonstrated here. The first, which relies on sparse reconstruction, uses an a priori assumption of scattering behavior to generate a redundant dictionary where each column corresponds to a pixel in the ROI. The second method extends this concept by using multidimensional models for each pixel, with each pixel corresponding to a "block" in the dictionary matrix; this method does not require advance knowledge of scattering behavior. Analysis and experimental results presented demonstrate the validity of the sparsity assumption. Experiments show that images generated with sparse methods are superior to those created with delay-and-sum methods; the techniques here are shown to be tolerant of propagation model mismatch. The block-sparse method described here also allows the extraction of scattering patterns, which can be used for damage characterization.

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10

Li, Zongbao. "Crack detection in annular components by ultrasonic guided waves". Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/15920.

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11

Krishna, Aditya. "Topological Imaging of Tubular Structures using Ultrasonic guided waves". Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0111.

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Les structures tubulaires sont largement utilisées dans diverses industries telles que l’aérospatiale, le pétrole et le gaz, le nucléaire, etc. Le Contrôle Non Destructive (CND) de ces structures joue un rôle crucial au cours de leur cycle de vie. Afin de tester de grandes structures avec une accessibilité limitée, la méthode de CND utilisant des ondes guidées a été développée comme une solution viable. En raison de la nature de ces ondes, elles sont capables de se propager sur de grandes distances sans perdre une grande partie de leur énergie. Cependant, elles sont complexes puisque leur vitesse dépend de la fréquence, c'est-à-dire qu'elles sont dispersives. Classiquement, l’étude de ce type d’ondes nécessite des simulations par éléments finis coûteuses. Cette thèse propose une alternative à de telles simulations avec une méthode rapide et robuste pour simuler la propagation d'ondes guidées dans des structures tubulaires.Partant de ces calculs, pour localiser des défauts, l'objectif de ce travail est d'obtenir des images topologiques 3D de structures tubulaires isotropes multicouches par propagation de ces ondes guidées ultrasonores. Un modèle mathématique est proposé où l'équation d'onde est convertie en une équation différentielle ordinaire par rapport au rayon «r» en utilisant les transformées de Fourier et de Laplace pour les variables spatiales et temporelles respectivement. La solution en ondes partielles, exprimée comme une combinaison des fonctions de Bessel, permet la création d'un algorithme semi-analytique rapide et robuste pour calculer la fonction de Green de structures tubulaires. Un modèle approché en présence de défauts numériques est ensuite développé. La réponse des défauts est considérée comme la réponse cumulative des sources secondaires, visant à annuler le champ de contraintes incident et diffracté présent en son sein. Ensuite, le modèle numérique est validé par des mesures expérimentales.Enfin, la technique de l'imagerie topologique est introduite. Cette méthode d'imagerie est basée sur la corrélation entre les champs ultrasonores sans et avec défaut. La polyvalence et la flexibilité de l'outil numérique en conjonction avec cette méthode d'imagerie sont ensuite démontrées avec succès en localisant et imageant une multitude de défauts numériques et expérimentaux avec des dimensions aussi faibles que 1/40e de la longueur d'onde
Tubular structures are widely used in a variety of industries such as Aerospace, Oil and Gas, Nuclear, etc. Non Destructive Evaluation (NDE) of these structures plays a crucial role during it’s life cycle. In order to test large structures with limited accessibility, guided wave testing was developed as a viable solution. Due to the nature of these waves, they are able to propagate over large distances without losing much of their energy. However, they are also complex in that their velocity is frequency dependent i.e. they are dispersive. Conventionally, guided wave testing require costly finite element simulations. This thesis offers an alternative to such simulations with a quick and robust method to simulate guided wave propagation in tubular structures.Based on these calculations, the aim of this work is to obtain the 3d topological image of multilayered isotropic tubular structures using ultrasonic guided waves to locate defects. A mathematical model has been proposed where the wave equation is converted to an ordinary differential equation with respect to radius 'r' using the Fourier and Laplace transforms for the spatial and temporal variables respectively. The partial wave solution, expressed as a combination of Bessel’s functions, allows for the creation of a fast robust semi-analytical algorithm to compute the Green function in tubular structures. A model to approximate numerical defects is then developed. The defect response is considered as the cumulative response of secondary sources, aiming to negate the incident and diffracted stress field present within it. Next, the numerical model is validated with experimental measurements.Finally, the technique of Topological Imaging is introduced. This method of imaging is based on the idea of performing a correlation between two wave fields for defect localization. The versatility and flexibility of the numerical tool in conjunction with the method of imaging is then successfully demonstrated by localising and imaging a multitude of numerical and experimental defects with dimensions as low as 1=40th of the wavelength

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12

Chan, Chi Kit. "An ultrasonic self-localized automated guided vehicle system /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?IELM%202006%20CHAN.

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13

Seifried, Robert. "Propagation of guided waves in adhesive bonded components". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/19494.

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14

Ma, Jian. "On-line measurements of contents inside pipes using guided ultrasonic waves". Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/8168.

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15

Willey, Carson Landis. "Ultrasonic Guided Wave Tomography for Wall Thickness Mapping in Pipes". University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1460729589.

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16

Autrusson, Thibaut Bernard. "Nonlinear ultrasonic guided waves for quantitative life prediction of structures with complex geometries". Thesis, Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37103.

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Material damage such as dislocations and microcracks are characteristic of early stages of fatigue. Accumulation of these nascent cracks leads to non-linear elastic response of the material. These non-linearities can be detected from harmonic generation for propagating elastic waves. The long term goal of this study is to investigate the non-linear elastic propagation in parts with complex geometry. Cellular Automata is introduced as a new simulation method, in order to develop new analysis on quadratic non-linearities. An existing linear code was progressively modified to take into account a different constitutive law. Also the boundary conditions need to be reviewed to ensure free stress with the non-linear behavior. The propagation of the longitudinal wave is investigated in detail. Numerical accuracy is validated from comparison with a closed, for both linear and non-linear code. The reflection of the non-linear P-wave gives confirmation for the correct treatment of the boundary condition. Finally the capabilities of the Cellular Automata code are underlined for reflection of Lamb waves for various boundary conditions.

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17

Koston, E. "Fatigue crack monitoring in multi-layered aircraft structures using guided ultrasonic waves". Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/516138/.

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The detection of fatigue cracks at fasteners in the sub layers of multi-layered aircraft structures can be problematic using conventional nondestructive testing methods. In this thesis the sensitivity of low frequency guided ultrasonic waves to detect these defects is studied. Guided ultrasonic waves typically have energy distributed through the thickness of such structures and allow for defect detection in all sub-layers, but have wavelengths larger than commonly used in bulk wave ultrasonic testing. The model aerospace multi-layered structure investigated consists of two aluminium plate strips adhesively bonded using a paste adhesive with a fastener hole. Guided waves were excited by placing piezoelectric (PZT) transducers on the surface of the structure. Experimentally the wave propagation and scattering was measured using a laser interferometer. The wave propagation was studied numerically using Semi-Analytical Finite-Element (SAFE) calculations and 3D Finite Element (FE) simulations. Thickness and width mode shapes of the guided waves were identified from the SAFE simulations. By placing PZT discs across the width of the structure the excited exural wave modes could be controlled to an extent. The thickness mode shapes of these waves are similar to those in a large multi-layered plate structure. 3D FE simulations predict a similar amplitude change due to a defect in these structures. Fatigue crack growth monitoring on tensile specimens was realized, measuring the amplitude at a single point. The measured changes in the amplitude of the ultrasonic signal due to a defect agree well with 3D FE simulations. These investigations found that using low frequency guided ultrasonic waves defects through the thickness of a hidden sub layer can be detected from measurements on the undamaged, accessible layer.

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18

Gandhi, Navneet. "Determination of dispersion curves for acoustoelastic lamb wave propagation". Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37158.

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The effect of stress on Lamb wave propagation is relevant to both nondestructive evaluation and structural health monitoring because of changes in received signals due to both the associated strain and the acoustoelastic effect. A homogeneous plate that is initially isotropic becomes anisotropic under biaxial stress, and dispersion of propagating waves becomes directionally dependent. The problem is similar to Lamb wave propagation in an anisotropic plate, except the fourth order tensor in the resulting wave equation does not have the same symmetry as that for the unstressed anisotropic plate, and the constitutive equation relating incremental stress to incremental strain is more complicated. Here we review the theory of acoustoelastic and develop theory for acoustoelastic Lamb wave propagation and show how dispersion curves shift anisotropically for an aluminum plate under biaxial tension. We also develop an approximate method using the effective elastic constants (EECs) and show that existing commercial tools to generate dispersion curves can be used under restricted conditions to describe wave propagation in biaxially stressed plates. Predictions of changes in phase velocity as a function of propagation direction using theory and the EEC method are compared to experimental results for a single wave mode.

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19

Koreck, Juergen. "Computational characterization of adhesive bond properties using guided waves in bonded plates". Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-08252006-064856/.

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Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2007.
Jacobs, Laurence, Committee Chair ; Qu, Jianmin, Committee Member ; Valle, Christine, Committee Co-Chair.

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20

Ahmed, Mustofa N. "A Study of Guided Ultrasonic Wave Propagation Characteristics in Thin Aluminum Plate for Damage Detection". University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1387732124.

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21

Yucel, Mehmet Kerim. "Signal processing methods for defect detection in multi-wire helical waveguides using ultrasonic guided waves". Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11219.

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Non-Destructive Testing of industrial components carries vital importance, both financially and safety-wise. Among all Non-Destructive techniques, Long Range Ultrasonic Testing utilizing the guided wave phenomena is a young technology proven to be commercially valid. Owing to its well-documented analytical models, Ultrasonic Guided Waves has been successfully applied to cylindrical and plate-like structures. Its applications to complex structures such as multi-wire cables are fairly immature, mainly due to the high complexity of wave propagation. Research performed by the author approaches the long range inspection of overhead transmission line cables using ultrasonic guided waves. Existing studies focusing on guided wave application on power cables are extremely limited in inspection range, which dramatically degrades its chances of commercialization. This thesis consists of three main chapters, all of which approaches different problems associated with the inspection of power cables. In the first chapter, a thorough analysis of wave propagation in ACSR (most widely used power cable) cables is conducted. It is shown that high frequency guided waves, by concentrating the energy on the surface layers, can travel much further in the form of fundamental longitudinal wave mode, than previous studies have shown. Defect detection studies proved the system’s capability of detecting defects which introduce either increase or decrease in cross sectional area of the cable. Results of the chapter indicate the detectability of defects as small as 4.5% of the cross sectional area through a 26.5 meter long cable without any post-processing. In the second chapter, several algorithms are proposed to increase the inspection range and signal quality. Well-documented wavelet-denoising algorithm is optimized for power cables and up to 24% signal-to-noise ratio improvement is achieved. By introducing an attenuation correction framework, a theoretical inspection range of 75 meters is presented. A new framework combining dispersion compensation and attenuation correction is proposed and verified, which shows an inspection range of 130 meters and SNR improvement up to 8 dBs. Last chapter addresses the accurate localization of structural defects. Having proven the optimum excitation and related wave propagation in ACSR cables, a system having a more complex wave propagation characteristics is studied. A new algorithm combining pulse compression using Maximal Length Sequences and dispersion compensation is applied to multi-modal signals obtained from a solid aluminum rod. The algorithm proved to be able to improve signal quality and extract an accurate location for defects. Maximal Length Sequences are compared to chirp signals in terms of SNR improvement and localization, which produced favourable results for MLS in terms of localization and for chirp in terms of SNR improvement.

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22

Baltazar-Lopez, Martin Eduardo. "Applications of TAP-NDE technique to non-contact ultrasonic inspection in tubulars". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1614.

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The possibility and feasibility of experimental detection of localized defects in tubes using laser-induced ultrasonic wave approach through Thermo Acousto Photonic Non Destructive Evaluation (TAP-NDE) and Signal processing through wavelet transform is examined in this research. Guided waves in cylindrical surfaces provide solutions for detection of different defects in the material. Several experiments were conducted to this respect. Wave propagation in both axial and circumferential directions was studied. The dispersive wave propagation of ultrasonic waves in hollow cylinders has been investigated experimentally, primarily for use in non-contact and nondestructive inspections of pipes and tubes. The laser ultrasonic waves propagated in cylindrical waveguides are particularly attractive because of their unique characteristics in the applications of nondestructive evaluation (NDE). Contrary to studies making use of only axially symmetric guided waves in hollow cylinders, here are analyzed also nonaxisymmetric waves. The analysis of data is made by using the Gabor wavelet transform. The capability of modeling the guided wave dispersion in hollow cylinders is used in developing guided wave experimental techniques for flaw detection. Good agreement was obtained when comparing the dispersion spectra between theory and experimentation. Measurement of group velocities of guided waves, which are obtained directly from the wavelet transform coefficients, can be used to determine allocation and sizing of flaws.

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23

Duroux, Adelaide A. "Estimation of guided waves from cross-correlations of diffuse wavefields for passive structural health monitoring". Thesis, Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33896.

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Recent theoretical and experimental studies in a wide range of applications (ultrasonics, underwater acoustics, seismicoe) have demonstrated that Green's functions (impulse responses) can be extracted from cross-correlation of diffuse fields using only passive sensors. The technique, whose validity is supported by a physical argument based on time-reversal invariance, effectively uses a correlation process between the point source and points located in the focal zone. Indeed, the coherent noise source distributions can be considered as a timereversal mirror and the cross-correlation operations gives the field measured at one receiver after refocusing on the other receiver. Passive-only reconstruction of coherent Lamb waves (80-200 kHz) in an aluminum plate and thickness comparable to aircraft fuselage and wing panels will be presented. In particular, the influence of the noise source characteristics (location, frequency spectrum) on the signal-to-noise ratio the emerging coherent waveform will be investigated using a scanning laser Doppler velocimeter. This study suggests the potential for a structural health monitoring method for aircraft panels based on passive ultrasound imaging reconstructed from diffuse fields.

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24

Mograne, Mohamed Abderrahmane. "Viscosimétrie ultrasonore ultra large bande". Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTS089/document.

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Cette thèse a pour objectif d’instrumenter un contenant familier dans le domaine du biomédical et de la chimie (un tube à essai) avec des éléments piézoélectriques à ondes longitudinales (L) et d’implémenter, en les optimisant, diverses méthodes ultrasonores pour mesurer les viscosités rapidement, sans changer de banc de mesure et cela de quelques Hz à plusieurs dizaines de mégahertz au voisinage de la température ambiante. Grâce au système mis en place il est possible en quelques minutes de déterminer le comportement rhéologique du liquide, étudié en mesurant sa viscosité de cisaillement. Par ailleurs, la gamme de viscosité atteinte est extrêmement large puisque les mesures sont possibles de quelques dizaines de mPa.s à plusieurs centaines de Pa.s. Enfin, au-delà de résultats quantitatifs en terme de viscosité, le banc de mesure peut être aussi utilisé pour suivre de façon qualitative des cinétiques de réaction (polymérisation par exemple)
The main goal of this thesis is to set specific piezoelectric elements emitting longitudinal waves (L) on a well-known container in the field of biomedical and chemistry (a test tube) and to implement with some optimizations various ultrasonic methods to measure viscosities quickly, without changing the measurement bench. The measurement has to be done from a few Hz to several tens of megahertz around room temperature. Up to now it is possible to determine in a few minutes the rheological behavior of the liquid studied thanks to the evaluation of its shear viscosity. Furthermore, the viscosity range reached is extremely wide: the measurements are possible from a few tens of mPa.s to several hundred Pa.s. Finally, beyond quantitative results in terms of viscosity, the measurement bench can also be used to qualitatively monitor reactions (polymerization for example)

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25

Matt, Howard M. "Structural diagnostics of CFRP composite aircraft components by ultrasonic guided waves and built-in piezoelectric transducers". Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3238426.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed January 4, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 203-216).

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26

Engholm, Marcus. "Ultrasonic Arrays for Sensing and Beamforming of Lamb Waves". Doctoral thesis, Uppsala universitet, Signaler och System, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-122189.

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Non-destructive testing (NDT) techniques are critical to ensure integrity and safety of engineered structures. Structural health monitoring (SHM) is considered as the next step in the field enabling continuous monitoring of structures. The first part of the thesis concerns NDT and SHM using guided waves in plates, or Lamb waves, to perform imaging of plate structures. The imaging is performed using a fixed active array setup covering a larger area of a plate. Current methods are based on conventional beamforming techniques that do not efficiently exploit the available data from the small arrays used for the purpose. In this thesis an adaptive signal processing approach based on the minimum variance distortionless response (MVDR) method is proposed to mitigate issues related to guided waves, such as dispersion and the presence of multiple propagating modes. Other benefits of the method include a significant increase in resolution. Simulation and experimental results show that the method outperforms current standard processing techniques. The second part of the thesis addresses transducer design issues for resonant ultrasound inspections. Resonant ultrasound methods utilize the shape and frequency of the object's natural modes of vibration to detect anomalies. The method considered in the thesis uses transducers that are acoustically coupled to the inspected structures. Changes in the transducer's electrical impedance are used to detect defects. The sensitivity that can be expected from such a setup is shown to highly depend on the transducer resonance frequency, as well as the working frequency of the instrument. Through simulations and a theoretical argumentation, optimal conditions to achieve high sensitivity are given.

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27

Leleux, Alban. "Contrôle non destructif de composites par ondes ultrasonores guidées, générées et détectées par multiéléments". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14623/document.

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Une technique de Contrôle Non Destructif (CND) a été développée, permettant la génération et la détection d’ondes de Lamb guidées le long de grandes plaques constituées de différents matériaux (métal, polymère ou composite renforcé par des fibres). Basée sur l’emploi de nombreux éléments étroitement couplés à la plaque, cette technique d’inspection diffère du Structural Health Monitoring (SHM) classique car tous les éléments émetteurs ou récepteurs sont regroupés dans une zone très localisée, définie par la surface active d’une sonde multiélément matricielle, et ne sont pas fixés de manière permanente et distribuée au sein, ou en surface, de la structure testée. De plus, le principe (connu) du déphasage entre éléments est appliqué à la sonde pour la génération et la réception d’un mode de Lamb pur dans (ou provenant) de multiples directions le long de la plaque. Les lois de retards appliquées à ces éléments, aussi bien lorsque la sonde fonctionne en mode émission qu’en mode réception, prennent en compte la nature dispersive de l’onde de Lamb. Enfin, un traitement de signal spécifique est appliqué pour compenser la dispersion subie par les ondes guidées au cours de leur propagation le long de la pièce testée. Un prototype expérimental et sa modélisation par éléments finis sont présentés, ainsi que les mesures et les résultats simulés de ses performances en termes de sélectivité modale et de directivité angulaire. Concernant les applications de CND, la construction d’images, représentatives de toutes les parties de la pièce testée qui diffractent le mode guidé (bord de pièce, défauts, trous, raidisseurs, etc.), a permis de démontrer le potentiel (et quelques limites) de cette technique vis-à-vis d’une inspection rapide de grandes structures, y compris de zones éloignées de la sonde ou encore de zones difficiles d’accès
A technique of Non-Destructive Testing (NDT) was developed for the generation and detection of Lamb waves propagating along large plates made of different materials (metal, polymer or fibre-reinforced composite). Based on the use of many elements closely coupled to the plate, this inspection technique differs from the classic Structural Health Monitoring (SHM) because all the transmitters or receivers are grouped in a very localized area, defined by the active surface of a phased array matrix probe, and are not permanently attached and distributed within or on the surface of the test structure. In addition, the principle (known) of the phase shift between the elements is applied to the probe for generating and receiving a pure Lamb mode in (or from) multiple directions along the plate. The delay laws applied to these elements, in transmit mode or receive mode, take into account the dispersive nature of the Lamb wave. Finally, a specific signal processing is applied to compensate the dispersion suffered by the guided waves during their propagation along the test piece. An experimental prototype and its finite element modeling are presented, as well as measurements and simulation results of its performances in terms of modal selectivity and angular directivity. For NDT applications, the construction of images, representing all parts of the test piece, which diffract the guided mode (edges, defects, holes, stiffeners, etc.), has demonstrated the potential (and some limits) of this technique for a quick inspection of large structures, including areas remote from the probe or areas difficult to access

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28

Coccia, Stefano. "Ultrasonic guided waves for structural health monitoring and application to rail inspection prototype for the Federal Railroad Administration". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3283950.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed March 14, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 271-281).

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29

Poosh, Matineh Eyb. "A Data-Driven Framework Based on Sparse Representation of Ultrasonic Guided-Waves for Online Damage Detection of Pipelines". Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/642.

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This work addresses some of the open challenges in guided-wave based structural health monitoring (SHM) of pipelines. In this dissertation, we review these challenges under three headings: (a) Multiple modes, (b) Multi-path reflections, and (c) Sensitivity to environmental and operational conditions (EOCs). The objective is to develop damage detection methods that (1) simplify guided-wave signals, and (2) have low sensitivity to EOC variations. First, I propose a supervised method for online damage detection. The detection performance is maximized under variety of EOCs, by imposing a sparsity constraint on the signals. In the training stage, data is recorded from an intact pipe, as well as the pipe with structural abnormalities. During the monitoring stage, test signals are projected on the extracted sparse discriminant vector, and these projections are used as damage-sensitive features. I conduct a diverse set of laboratory and field experiments to investigate and to validate the extent to which EOC variations, as well as the differences in characteristics of the structural abnormality in training and test data, can influence the discriminatory power of the damage-sensitive features. The validation results suggest that a simple binary-labeled training data (i.e., undamaged/damaged), obtained under a limited range of EOCs, is sufficient for the proposed method. In other words, the detection method does not require prior knowledge about the characteristics of the damage (e.g., size, type, location), and/or a training dataset that is obtained from a wide range of EOCs. ix Next, I propose an unsupervised method to address some of the limitations of the aforementioned supervised approach. The unsupervised approach eliminates the need for training data captured from a pipe with structural abnormality, which can be a challenge for some applications such as pipes with restricted accessibility. Therefore, the damage-related training parameters that may affect the detection performance of the supervised method are not an issue for the unsupervised approach. The proposed unsupervised method takes advantage of two facts that are further verified throughout this work: (1) high-energy arrivals are less sensitive to EOC variations compared to the rest of the signal, and (2) damage changes the energy-content and/or time-location of high-energy arrivals in the signal. For this method, the training dataset is not labeled, but is assumed to mostly include intact signals. In the training stage, a sparse subset of high-energy arrivals from intact pipes is extracted so that energy estimation error is minimized. My experimental analysis proved that high-energy arrivals in intact signals are located at different time-points than those in damaged signals. Therefore, using the extracted sparse subset (which is mainly composed of high-energy arrivals), the energy estimation error will increase as damage occurs. The proposed method is proved successful for online detection of damage under varying EOCs. It is also shown that the wider the range of EOCs in the training dataset, the better the detection performance. This range, however, is not required to be comprehensive of all possible testing scenarios. For example, for a test dataset in which temperature varies between 24℃ and 39℃, a training dataset with temperatures ranging between 24℃ and 30℃ results in separation accuracy of 99%, and detection delay of five observations, captured in one-minute intervals.

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30

Gravenkamp, Hauke [Verfasser], Sabine [Gutachter] Langer, Marc [Gutachter] Kreutzbruck y Chongmin [Gutachter] Song. "Numerical methods for the simulation of ultrasonic guided waves / Hauke Gravenkamp ; Gutachter: Sabine Langer, Marc Kreutzbruck, Chongmin Song". Berlin : Bundesanstalt für Materialforschung und -prüfung (BAM), 2014. http://d-nb.info/1122647859/34.

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31

Rodrigues, Marques Hugo. "Omnidirectional and unidirectional SH0 mode transducer arrays for guided wave evaluation of plate-like structures". Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/14021.

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Structures made of plate-like components are common in a variety of industries where the impacts of structural failures are severe. In many cases these structures are surrounded and only partially accessible, such as storage tanks and bridges, making them difficult to inspect frequently. The application of ultrasonic Guided Waves (GWs) in the evaluation and monitoring of relatively large plate-like structures is evermore a feasible option with the continuous development of transducer arrays. The use of transducer arrays is however complex due to directional control and the existence of many GW modes. Aimed at the evaluation of plate-like structures, in this research two piezoelectric transducer arrays respectively capable of omnidirectional and unidirectional control of the fundamental GW shear mode in plates (SH0) with above 20 dB mode purity are successfully designed, produced and validated. Omnidirectionality facilitates full structural evaluation coverage and can lead to defect mapping of large volumes with relatively few transducers. A unidirectional beam with relatively high mode purity facilitates evaluation of specific structural locations. Preference to the SH0 mode was given because of its non-dispersive and in-plane propagation properties making it more suitable than other GW modes to propagation in structures surrounded by fluid material. To enable the array development, a number of monolithic piezoelectric thickness-shear transducers of varied area were characterised with respect to GW mode directionality, amplitude and SH0 mode purity. The characterisation of each thickness-shear transducer allows for optimised superposition manipulation for specific applications. A single characterised shear transducer was selected for use in the development of omnidirectional and unidirectional SH0 mode transducer arrays. To aid development a linear superposition analysis model was produced and used to predict for a circular array design the optimum parameters for omnidirectional SH0 mode transmission with significant mode purity. A range of parameter combinations were evaluated and their predicted influence on array performance was characterised. The same method was employed to optimise a dual row linear array design for the unidirectional transducer array. All results were validated by FE models and later with empirical data. Both developed transducer arrays were characterised with respect to GW mode directionality, magnitude and SH0 mode purity. Both their detection sensitivity to pertinent defects and structures was validated, demonstrating relevance to Non Destructive Evaluation (NDE) and Structural Health Monitoring (SHM) applications.

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32

Chitikireddy, Ravi. "Laser generated thermoelastic waves in finite and infinite transversely isotropic cylinders". Taylor & Francis Group, LLC, 2010. http://hdl.handle.net/1993/8445.

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This thesis presents a theoretical study of thermoelastic guided waves in cylinders in the context of Lord-Shulman generalized theory of thermoelasticity. Two different methods were formulated to study dispersion relations in infinite cylinders. One of them is a Semi Analytical Finite Element (SAFE) method and the other is an analytical method. In the SAFE method, the dispersion equation has been formulated as a generalized eigenvalue problem by treating radial displacement and temperature with a one dimensional finite element model through the thickness of the cylinder. In the analytical method, displacement potentials are introduced to obtain the dispersion relations of guided wave modes. This method is applicable to isotropic cylinders and has been developed primarily to cross check the SAFE formulation. Frequency spectra obtained by both methods for an isotropic cylinder have shown excellent agreement with each other. Since the SAFE method can be used for an anisotropic composite cylinder, guided wave modes for anisotropic and composite cylinders are presented. Transient analysis of ultrasonic guided waves generated by concentrated heating of the outer surface of an infinite anisotropic cylinder has also been studied. The SAFE method is employed to model the response of a cylinder due to a pulsed laser focused on its surface. Green’s functions were constructed numerically by superposition of guided wave modes in frequency and wave number domains. Time histories of the propagating modes are then calculated by applying an inverse Fourier transformation in the time domain. Transient radial displacements of longitudinal and flexural modes of a silicon nitride cylinder are presented. Propagation of thermoelastic waves in finite length circular cylinders have also been investigated. The SAFE method is used to simulate the guided wave modes in the cylinder. Frequency spectra obtained by the SAFE formulation, for a finite length transversely isotropic cylinder, are validated by comparing the numerical results with relevant publications. Frequency spectra for axisymmetric and asymmetric modes in a silicon nitride finite cylinder with both ends insulated and restrained by frictionless rigid walls are presented. The plain strain problem of circumferential guided waves is also studied and the results are validated for an isothermal case.

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33

Murdy, Paul. "Combining Acoustic Emission and Guided Ultrasonic Waves for Global Property Prediction and Structural Health Monitoring of Glass Fiber Composites". Thesis, Montana State University, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10981460.

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Since the turn of the century, wind turbines have been rapidly growing in size and are projected to continue growing as the technology develops. These increases in size have led to increased failure rates of the glass fiber composite turbine blades. Because of this, it is of utmost importance to understand failure mechanisms in glass fiber composites and investigate new approaches to predicting failures. This has led to advancements in structural health monitoring of large composites structures by applying sophisticated sensing technologies, in attempts to evaluate material damage states and predict structural failures before they occur. This research has taken a novel approach to apply multiple ultrasonic monitoring techniques, in the form of acoustic emission and guided ultrasonic waves, simultaneously to the mechanical testing of glass fiber reinforced composite laminates. Testing of the composite laminates was conducted in the form of increasing load-unload-reload static tension tests and tension-tension fatigue tests, to measure modulus degradation of the laminates while applying the monitoring techniques. Acoustic emission was used to detect damage events that occurred within laminates in real-time and guided ultrasonic waves were applied periodically to the laminates to observe changes in wave propagation and relate back to damage severity within the laminates. Furthermore, the acoustic emission and guided ultrasonic wave datasets were combined and used to train multivariate regression models to predict modulus degradation of the laminates tested, with no prior knowledge of the laminates’ loading histories. Overall, the predictive models were able to make good predictions and showed the potential for combining multiple monitoring techniques into singular systems and statistical predictive models. This research has shown that the combination of the two measurement techniques can be implemented for more accurate and reliable monitoring of large composite structures than the techniques used individually, with minimal additional hardware. Ultimately, this research has paved the way for a new form of smart structural health monitoring, with superior predictive capabilities, which will benefit the renewable energy through reducing maintenance and repair costs and mitigating the risk of wind turbine blade failures.

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34

Huber, Armin [Verfasser] y Markus [Akademischer Betreuer] Sause. "Numerical Modeling of Guided Waves in Anisotropic Composites with Application to Air-coupled Ultrasonic Inspection / Armin Huber ; Betreuer: Markus Sause". Augsburg : Universität Augsburg, 2021. http://d-nb.info/1230755314/34.

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35

McKeon, Peter. "A fundamental study to enable ultrasonic structural health monitoring of a thick-walled composite over-wrapped pressure vessel". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54308.

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A structural health monitoring system is desired to monitor the integrity of cylindrical, multi-layer carbon over-wrapped pressure vessels intended to house hydrogen at high pressures. In order to develop the system based on ultrasonic guided wave technology, the interaction between ultrasonic guided waves and defect types of interest must be understood. Finite element models in two and three dimensions are developed to predict guided wave motion in the reservoirs. Key parameters are optimized including frequency range, excited modes, detected modes, and transducer dimensions. A novel baseline subtraction technique in the frequency wavenumber domain is presented to increase lower level detection limits. Some experiments are carried out to corroborate the findings in the finite element environment.

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36

Okumura, Shigeaki. "Array Signal Processing for Accurate Medical Ultrasound Measurements". Kyoto University, 2018. http://hdl.handle.net/2433/232419.

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37

Lefevre, Fabien. "Caractérisation de structures du type plaque par ondes guidées générées et détectées par laser". Valenciennes, 2010. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/24980ba6-f06c-4c75-988a-16e1228d2e42.

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La réalisation de couches minces déposées sur substrats est très recherchée dans de nombreuses applications. C'est le cas par exemple des pièces nickelées destinées à des dispositifs à hautes performances techniques, où une couche anti-corrosion est déposée a n d'améliorer leur imperméabilité. L'utilisation de ces structures du type couche sur substrat étant grandissante, on comprend dès lors l'importance de disposer de moyens non destructifs permettant de les contrôler et de les caractériser. Dans ce travail, l'objectif a été de mettre à pro t les ondes acoustiques guidées pour le contrôle et la caractérisation de structures du type plaque. Pour la génération et la détection de ces ondes guidées, la technique laser-ultrasons a été privilégiée. C'est une méthode large bande et sans contact permettant d'éviter l'utilisation d'un milieu de couplage ou tout contact direct avec la structure et pouvant s'adapter à des géométries complexes. Pour tirer pro t au maximum de l'utilisation de cette technique, des réseaux de neurones lui ont été associés a n de résoudre le problème inverse posé par les ondes de plaque. Une méthode de caractérisation originale, e cace et polyvalente a ainsi été mise en oeuvre, permettant de déterminer les propriétés géométriques et/ou mécaniques de plaques simples ou de structures à couches. Des structures composées de silicium ont plus particulièrement été étudiées par le biais de cette méthode. Des simulations éléments nis, ainsi que des études sur certains défauts présents dans les couches minces, comme l'adhérence, sont présentées
The deposition of thin layers on substrates is more and more required in many applications. For example, to reach high technical performance, bumpers or other parts are nickeled to improve their impermeability and resistance. Another example in microelectronics is the realization of transistors found in LCDs where they are associated with each pixel. The use of these layer/substrate structures is growing, so the importance of having non-destructive techniques to monitor and characterize them is well understood. The point in using ultrasonic waves for non-destructive testing and evaluation of various materials and structures is well known. In this work, the aim was to use guided waves to monitor and to characterize plaque-like structures. The main advantage of using these modes lies in their ability to test very large areas and inaccessible structures. For the generation and detection of guided waves, the laser ultrasonics technique was preferred. It is a broadband and non contact method which doesn't imply the use of coupling medium and which can be adapted to complex geometries. To take full advantage of this technique, it has been combined with neural networks in order to solve the inverse problem posed by the propagation of guided waves. As a result, an original, e cient and polyvalent characterization method has been obtained, which allowed us to determine the geometric properties and / or the elastic parameters of di erent plate-like structures. Structures made of silicon have been studied with this method. Finite element simulations and studies concerning the in uence of defects, including adhesion, on the waves propagation are also presented

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38

Hall, James Stroman. "Adaptive dispersion compensation and ultrasonic imaging for structural health monitoring". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41159.

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Ultrasonic guided wave imaging methods offer a cost-effective mechanism to perform in situ structural health monitoring (SHM) of large plate-like structures, such as commercial aircraft skins, ship hulls, storage tanks, and civil structures. However, current limits in imaging quality, environmental sensitivities, and implementation costs, among other things, are preventing widespread commercial adoption. The research presented here significantly advances state of the art guided wave imaging techniques using inexpensive, spatially distributed arrays of piezoelectric transducers. Novel adaptive imaging techniques are combined with in situ estimation and compensation of propagation parameters; e.g., dispersion curves and transducer transfer functions, to reduce sensitivity to unavoidable measurement inaccuracies and significantly improve resolution and reduce artifacts in guided wave images. The techniques can be used not only to detect and locate defects or damage, but also to characterize the type of damage. The improved ability to detect, locate, and now characterize defects or damage using a sparse array of ultrasonic transducers is intended to assist in the establishment of in situ guided wave imaging as a technically and economically viable tool for long-term monitoring of plate-like engineering structures.

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39

Höhne, Christian [Verfasser], Jens [Akademischer Betreuer] Prager, Ennes [Gutachter] Sarradj y Manfred [Gutachter] Kaltenbacher. "Multimodal approach for the numerical simulation of ultrasonic guided waves in cylindrical structures of non-constant thickness / Christian Höhne ; Gutachter: Ennes Sarradj, Manfred Kaltenbacher ; Betreuer: Jens Prager". Cottbus : BTU Cottbus - Senftenberg, 2017. http://d-nb.info/1127580825/34.

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40

El, Rammouz Hala. "Réalisation de matrices de micro-transducteurs acoustiques : application au controle santé intégré". Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2021. http://www.theses.fr/2021UPHF0010.

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Les réseaux de micro-transducteurs connaissent un fort développement afin de répondre aux exigences du contrôle santé intégré des structures. Ce dernier permet d'évaluer en tout moment l'état de santé de la structure tout en intégrant un système de contrôle non destructif à celle-ci. En effet, un réseau de micro-transducteurs permet d'acquérir plusieurs signaux en même temps sans effectuer un balayage spatial permettant de caractériser la structure. Parallèlement, l'utilisation des ondes guidées ultrasonores fournit un outil efficace pour la caractérisation de celle-ci. Cependant, elles présentent des caractéristiques complexes qui rend l'analyse de leurs interactions avec des défauts compliquée. Pour cela, il est souhaitable de favoriser la propagation d'un mode unique dans la structure. Dans ce contexte, le but de cette thèse est de présenter un modèle de matrice de micro-transducteurs pour la réception des ondes guidées dans une structure cylindrique, en particulier, le mode de flexion F(1,1). Dans un premier temps, la réalisation et la caractérisation des matrices de micro-transducteurs sont présentées. Les résultats ont montré la capacité de celles-ci à opérer dans la gamme fréquentielle (60 kHz - 70 kHz) malgré sa haute fréquence de résonance. Dans un deuxième temps, les mesures optiques et électriques effectuées sur la matrice ont validé l'utilisation de celle-ci pour des applications dans le CSI et le CND des structures cylindriques tout en favorisant la propagation du mode F(1,1)
Micro-transducers networks are experiencing strong development in order to meet the require- ments of Structural Health Monitoring (SHM). The latter makes it possible to assess at any time the state of health of the structure while integrating a Non-Destructive Evaluation (NDE) system therein. Indeed, a network of micro-transducers makes it possible to acquire several signals at the same time without carrying out a mechanical scanning making it possible to characterise the structure. At the same time, the use of ultrasonic guided waves provides an e_ective tool for the characterisation of structures. However, they have complex characteristics which make the analysis of their interactions with defects complicated. For this, it is desirable to promote the propagation of a single-mode in the structure. In this context, this thesis aims to present a model of a micro- transducers matrix for the reception of guided waves in a cylindrical structure, in particular, the _exural mode F(1,1). First, the realisation and characterisation of the micro-transducer matrices are presented. The results showed their ability to operate in the frequency range (60 kHz - 70 kHz) despite its high resonant frequency. Second, the optical and electrical measurements carried out on the matrix validated its use for applications in the SHM and the NDE of cylindrical structures while generating the F(1,1) mode

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41

Masmoudi, Mohamed. "Modélisation de la propagation d'ondes guidées, générées et détectées par transducteurs ultrasonores à couplage air : Application au CND de structures aéronautiques composites". Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14483/document.

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Le contrôle non destructif par ondes guidées générées et détectées par des transducteurs ultrasonores à couplage par air, présente deux avantages majeurs. Le premier réside dans la capacité des ondes guidées à transporter l’information sur la qualité du milieu sur une grande distance. De plus, l’absence d’un milieu de couplage liquide entre les capteurs et le milieu à tester, rend le contrôle plus commode. Ce travail consiste d’abord à développer un procédé de simulation numérique qui prend en considération de nombreux paramètres du système de contrôle. Dans une optique de réduire le nombre de degrés de liberté, un modèle hybride a été développé qui consiste en une combinaison entre un modèle analytique basé sur l’intégrale de Kirchhoff pour la propagation des ultrasons dans l’air et un modèle éléments finis de la propagation des ondes guidées dans le matériau. La mesure des caractéristiques du transducteur à couplage par air (efficacité de l’émetteur et sensibilité du récepteur) permet, d’une part, de calculer la valeur exacte de la pression dans l’air et les valeurs exactes des champs de contraintes et de déplacements dans la structure, pour une tension et une fréquence d’excitation, et d’autre part, de remonter à la tension électrique aux bornes de ce récepteur pour une pression rayonnée par le matériau. Par suite, cette caractérisation rend possible la comparaison entre les prédictions numériques de la réponse (en niveau de tension) du système et les mesures expérimentales correspondantes. A la lumière du modèle numérique développé, une optimisation des paramètres du système de contrôle (angle, fréquence,diamètre, direction de propagation, champ proche et champ lointain) a été effectuée pour améliorer la pureté des modes guidés par le matériau. Une manipulation expérimentale, basée sur un transducteur à couplage par air pour l’émission et une sonde laser pour la réception, a été alors mise en place pour valider quelques prédictions numériques. Ensuite, on a étudié l’interaction des ondes guidées ultrasonores avec des défauts de type délaminage enfouis dans une plaque composite à symétrie quadratique. Pour cela, on a analysé la sensibilité des deux modes fondamentaux A0 et S0 au délaminage en terme de détectabilité. En parallèle, on a traité un problème inverse qui consiste à dimensionner un délaminage par le calcul du spectre fréquentiel du coefficient de réflexion. Enfin, on a mis en évidence le potentiel des transducteurs à couplage par air à ausculter des pièces aéronautiques impactées
Non-destructive testing (NDT) using guided waves generated and detected by air-coupled ultrasonic transducers have two main advantages. First, this non-contact technique without coupled medium allows obvious convenience of use. Moreover, the ability of guided waves to carry information about medium quality over long distance. In this context, a numerical model has been developed, which takes into account many parameters of the control system. In order to reduce the number of degrees of freedom, a hybrid model has been developed which consists of a combination between an analytical model, based on the Kirchhoff integral for the propagation of ultrasound in air and a finite element model for the propagation of guided waves in the material. The measured characteristics (efficiency and sensitivity) of two air-coupled transducers allow the prediction of the accurate values of the pressure of bulk waves generated in air and the measurement of the pressure of the radiated field in air by guided waves propagating in a structure. This process enables the comparison between predicted and measured guided waves modes. Based on the hybrid model, an optimization of the parameters of the control system (angle, frequency, diameter, direction of propagation, near and far field) was performed to improve the purity of guided modes along the material plate. To validate some numerical predictions, an aircoupled ultrasonic transducer is used and oriented at a specific angle chosen for generating one specific Lambmode guided along a composite plate sample, and a laser probe measures the normal velocity at different locations on the surface of the plate. Then, the interaction of ultrasonic guided waves with delamination in acomposite plate was studied. In particular, the sensitivity of the two fundamental modes A0 and S0 was analyzed in order to predict the detectability of the defect. In parallel, the inverse problem is solved and the defect size is quantified by calculating the spectrum of the reflection coefficient. Finally, the potential of air-coupled transducers to examine an aircraft structure, has been demonstrated

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42

Bouchakour, Omar. "Contrôle-santé structurel passif à ondes guidées, basé sur des réseaux de capteurs ultrasonores désynchronisés". Electronic Thesis or Diss., Valenciennes, Université Polytechnique Hauts-de-France, 2025. http://www.theses.fr/2025UPHF0004.

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L'évolution de la surveillance de l'état des structures (SHM) au cours des dernières années a vu émerger des réseaux de capteurs indépendants à faibles ressources matérielles. Cependant, les signaux enregistrés par ces capteurs pour faire de l'imagerie passive peuvent présenter des désynchronisations qui rendent difficile la localisation des endommagements dans la structure inspectée. Bien que la technique de pic de corrélation (PCT), reposant sur la symétrie des fonctions de corrélation de bruit, puisse être appliquée pour corriger ces décalages, une synchronisation parfaite est difficile à atteindre en présence de bruit électronique et/ou de reconstruction de la fonction de Green. Dans ce manuscrit, une étude du comportement des erreurs résiduelles liées à une resynchronisation imparfaite, en fonction des paramètres statistiques du bruit, est menée. Puis, la dégradation du contraste des images de localisation des défauts est quantifiée en fonction de l'écart type de ces erreurs de resynchronisation. Par la suite, un processus basé sur la pseudo-inversion de Moore-Penrose est développé pour minimiser ces erreurs et améliorer la qualité des images de localisation. Cette étude est ensuite étendue au cas de la localisation de défauts à diffusion anisotrope. Enfin, une étude de faisabilité est effectuée sur un réseau de capteurs communicants sans fil
The evolution of structural health monitoring (SHM) in recent years has witnessed the emergence of independent sensor networks with limited material resources. However, the signals recorded by these sensors for passive imaging can exhibit desynchronizations that make it difficult to locate damage in the inspected structure. Although the peak correlation technique (PCT), based on the symmetry of noise correlation functions, can be applied to correct these offsets, achieving perfect synchronization is challenging in the presence of electronic noise and/or reconstruction of the Green's function. In this manuscript, a study of the behavior of residual errors associated with imperfect resynchronization, as a function of the statistical parameters of noise, is conducted. Then, the degradation of the contrast of defect localization images is quantified as a function of the standard deviation of these resynchronization errors. Subsequently, a process based on the Moore-Penrose pseudo-inversion is developed to minimize these errors and improve the quality of the localization images. This study is then extended to the case of defect localization with anisotropic scattering. Finally, a feasibility study is carried out on a network of wireless communicating sensors

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43

Luker, L. Dwight. "Investigation of a cylindrical nonacoustic-wavenumber calibration array". Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15885.

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44

Sasso, Magali. "Traitement et analyse du signal ultrasonore pour la caractérisation de l'os cortical". Phd thesis, Paris Est, 2008. http://www.theses.fr/2008PEST0009.

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Ce travail de thèse porte sur l’analyse et le traitement des signaux ultrasonores pour la caractérisation de l’os cortical. La première partie est dédiée à l’analyse des signaux acquis par un prototype de sonde de transmission axiale à 1 MHz. Nous montrons qu’une contribution arrivant après le premier signal présente un intérêt pour la caractérisation ultrasonore de l’os cortical. En effet, cette contribution évaluée sur des radius humains in vitro est associée à une onde de flexion propagée dans l’os qui est dépendante de l’épaisseur corticale. L’analyse de cette contribution a nécessité le développement d’une technique de séparation d’ondes. Cette contribution étant plus basse fréquence que le premier signal et associée à un mode de propagation différent, nous montrons ainsi qu’une analyse plus poussée du signal peut permettre une approche multi-modes/multi-fréquences. Dans une seconde partie, nous montrons l’intérêt de l’évaluation de l’atténuation ultrasonore pour la caractérisation de l’os cortical. Lors d’une étude expérimentale in vitro sur des échantillons corticaux bovins, nous montrons la dépendance d’un paramètre d’atténuation aux propriétés osseuses et à la micro-structure. De plus, ce paramètre semble plus sensible aux propriétés osseuses que ne l’est la vitesse de l’onde longitudinale. Ainsi, l’atténuation évaluée en complément de la vitesse pourrait permettre de caractériser de manière plus complète l’os cortical
This work deals with the ultrasonic characterization of cortical bone. In a first part, the signals acquired with a 1-MHz axial transmission device are analyzed. A later contribution occuring after the first arriving signal is studied after the application of a wave separation procedure. This contribution is shown to be of interest for the ultrasonic characterization of cortical bone. Indeed, experiments performed in vitro on human radii show that this contribution is associated with a flexural wave guided which is dependent on the cortical thickness. In addition, this contribution has a lower frequency content than the first arriving signal and is associated with a different propagation mode. Therefore, a more thorough analysis of the ultrasonic signals enables a multi-modal/multi-frequency approach. In a second part, the ultrasonic attenuation is evaluated in an in vitro experimental study on bovine cortical bone samples. Ultrasonic attenuation is shown to be dependent on bone properties and micro-structure. Furthermore, this parameter seems to be more sensitive than the longitudinal wave velocity to bone parameters. Attenuation, in combination with ultrasonic wave velocity, is of interest and may provide a more comprehensive characterization of cortical bone

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45

Vogt, Thomas Karl. "Determination of material properties using guided waves". Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273280.

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46

Ouabi, Othmane-Latif. "Towards ultrasound-based localization and mapping for long-range inspection robots". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0145.

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L’inspection de larges structures en plaques métalliques, telles que les réservoirs de stockage ou les coques de navires, est un problème majeur dans l’industrie qui nécessite des solutions fiables et efficaces. Au cours du temps, des défauts non visibles, tels que des couches de corrosion apparaissant sur la partie intérieure des coques de navires, peuvent se développer et affecter l’intégrité de la structure. Pour empêcher des catastrophes, ces structures doivent être inspectées de façon à pouvoir planifier des opérations de maintenance lorsque des défauts sont détectés. Les méthodes d’inspection traditionnelles consistent à inspecter visuellement la structure, ou à effectuer des mesures d’épaisseur point par point. Celles-ci mènent toutefois à des temps longs d'inspection, et ne peuvent pas être utilisées pour une inspection à la fois précise et complète de larges structures. Cette thèse considère le déploiement de systèmes robotiques mobiles équipés d’un capteur ultrasonore pour l’émission et la réception d’ondes ultrasoniques guidées, dans le but de réaliser une tâche d’inspection. Ces ondes peuvent se propager à l’intérieur du matériau sur de longues distances, et sont sensibles à l’état du matériau. L’objectif est de permettre l’émergence de l’inspection robotique longue distance en écoutant les réflexions des ondes sur les éléments structurels. En raison de la possibilité de détecter des défauts à distance, tout le long de la trajectoire du robot, l’inspection robotique longue distance peut être beaucoup plus rapide et efficace que les méthodes d’inspection traditionnelles. La détermination de la trajectoire du robot avec précision et la cartographie de défauts potentiels sont critiques pour une opération d’inspection. Pour cette raison, cette thèse se concentre sur le problème de localisation et cartographie en simultané (l’acronyme anglais est SLAM) par ondes ultrasoniques guidées. Plus précisément, nous proposons différentes méthodes pour estimer la trajectoire du robot et cartographier des réflecteurs acoustiques en utilisant les mesures ultrasonores. En raison du caractère omnidirectionnel des ondes, les mesures résultantes contiennent de l’information sur le milieu dans toutes les directions. En revanche, ces données sont complexes, et leur traitement nécessite des méthodes spécifiques. Dans cette thèse, nous montrons que, en utilisant les réflexions des ondes ultrasonores sur les bords d’une plaque, une simple méthode de focalisation de voies par délai et somme et un modèle de propagation peuvent être combinés pour la localisation et la cartographie précises. La particularité de la méthode proposée est qu’elle ne nécessite pas d’étapes de détection et d’associations des échos contenus dans les signaux, alors que celles-ci sont des tâches délicates, en particulier lorsque les mesures sont bruitées. En somme, nous proposons des méthodes algorithmiques pour résoudre les problèmes de SLAM en temps réel, et de SLAM dit "entier". Nous considérons également les problèmes spécifiques qui émergent en raison de l’utilisation de la formation de voie par délai et somme, tels que le phénomène d’interférence du signal, et le manque d’évaluation de l’incertitude sur la carte. Une stratégie d’exploration est proposée afin de permettre la cartographie autonome d’une surface métallique par un système robotique. Enfin, nous proposons une méthode pour calibrer de façon automatique les paramètres du modèle de propagation lorsque les propriétés de propagation des ondes ne sont pas connues à priori. Les méthodes proposées sont validées expérimentalement en milieu de laboratoire, avec des mesures acoustiques obtenues en déplaçant les capteurs à la main, ou en utilisant une plateforme robotique réelle. Les résultats démontrent l’efficacité des méthodes proposées pour la localisation et la cartographie par ondes guidées et pourraient servir de support pour l’émergence d’une tâche réelle d’inspection robotique longue distance
The inspection of large plate-based metal structures, such as storage tanks or ship hulls, isa significant stake in the industry, which necessitates reliable and time-efficient solutions. Overthe time, concealed defects, such as corrosion patches growing from the inner side of ship hulls,can develop, and detrimentally affect the structural integrity. To avoid catastrophic failures, thestructures under operation must be inspected on a regular basis, so that structural maintenancecan be scheduled when defects are detected. Current inspection methods traditionally rely onvisual inspection, or on point-by-point thickness measurements, often performed by human operators. However, these methods are time-consuming, and cannot reasonably be used for anaccurate and complete inspection of large metal surfaces.This thesis considers the deployment of a mobile robotic system, equipped with an acousticsensor for emission and reception of omnidirectional ultrasonic guided waves, with the aim toassess the integrity of large structures. Guided waves can propagate inside the structure material,over large distances, following a direction parallel with the surface. What make them appealingis that they are sensitive to the material integrity. Hence, the target objective is to enablelong-range robotic inspection on large metal structures by listening to the wave reflections onstructural features. Due to the possibility to localize potential defects at long distance, all alongthe robot trajectory, long-range robotic inspection has the potential to be faster, and much moreefficient than traditional inspection methods.The abilities to accurately recover the robot position and to precisely map acoustic scatterers are critical for a successful inspection operation. For this reason, this thesis focuses onSimultaneous Localization and Mapping (SLAM) problems. More specifically, we propose various frameworks to recover the robot trajectory and map acoustic scatterers by relying on theultrasonic measurements. Due to the wave omnidirectionality, the measurements contain information from all directions. This results in significant data complexity, and calls for appropriatesignal processing methods. We will show that, by relying on ultrasonic wave reflections on theboundaries of a metal panel, the combination of a simple Delay-and-Sum (DAS) beamformingmethod with a wave propagation model can result in accurate localization and mapping. Theparticularity of the proposed approach is that no explicit echo detection, nor echo associationare required, whereas these are challenging tasks, especially in noisy environments. We proposealgorithmic solutions to solve both the online SLAM and the full SLAM problems. We alsotackle specific issues that arise when relying on DAS beamforming, such as signal interference,and the lack of uncertainty assessment on the map. An exploration strategy based on frontierexploration is also briefly presented, with the aim to enable the autonomous mapping of a metalsurface. Eventually, we propose a method to automatically calibrate the wave propagation modelwhen the propagation properties are not precisely known.The proposed methods are validated by performing experiments in laboratory conditions,either with measurements which are collected by manually moving the transducers, or by usinga real robotic platform. The results demonstrate the efficiency of our methods for on-platelocalization and mapping purposes, and may support the emergence of a true long-range roboticinspection operation

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47

Pezant, Joannes Charles. "High temperature thickness monitoring using ultrasonic waves". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26577.

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Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Michaels, Jennifer; Committee Member: Jacobs, Laurence; Committee Member: Michaels, Thomas. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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48

Mora, Pierric. "Réponse élastodynamique d'une plaque stratifiée anisotrope : approches comparées. : Vers le développement de méthodes hybrides". Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0382/document.

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Cette thèse traite de la résolution du problème direct de propagation d'un champ élastodynamique rayonné par une source dans un milieu stratifié anisotrope. Le contexte applicatif visé est le contrôle non destructif par ondes ultrasonores guidées de plaques de matériaux composites. Aux basses fréquences, ces matériaux sont assimilables à des milieux homogènes, anisotropes et dissipatifs. Deux approches causales sont étudiées et mises en oeuvre pour résoudre l'équation d'onde, et leur intérêt vis-à-vis de la méthode modale harmonique - la plus couramment employée dans ce domaine applicatif - est discuté. L'une des méthodes est modale et est formulée directement dans le domaine temporel. Elle permet de traiter facilement l'anisotropie, y compris en 3D, mais souffre des écueils classiques concernant le régime non-établi ou le cas du guide ouvert. L'autre approche est une formulation dans le domaine de Laplace de la méthode dite par ondes partielles. Elle présente l'intérêt d'être extrêmement polyvalente tout en conduisant à des coûts numériques tout à fait raisonnables. Dans un second temps, la possibilité d'exploiter ces deux méthodes pour résoudre des problèmes de diffraction par des défauts est étudiée. Une approche par éléments finis de frontière basée sur la méthode par ondes partielles est considérée. Elle permet de traiter efficacement le cas de défauts plans. L'extension à des défauts plus généraux est brièvement discutée
This work adresses the direct problem of the propagation of an elastodynamic field radiated by a source in an anisotropic layered medium. Applications concern non destructive evaluation of composite plates by ultrasonic guided waves. In the lower frequencies, these materials can be modeled as homogeneous, anisotropic and dissipative media. Two causal approaches are studied and developped to solve the wave equation, and their interest is discussed regarding to the widely used harmonic modal method. One of these methods is modal, and is formulated directly in the time domain. It allows to deal easily with anisotropy, even in 3D ; however it also suffers classical shortcomings such as the high cost of the unestablished regime or the difficulty to deal with open waveguides. The other method is a formulation of the so-called partial-waves method in the Laplace domain. Its attractiveness relies in its versatility and in the fact that computational costs can be very acceptable. In a second time, we consider using both methods to solve problems of diffraction by defects. A boundary element method based on the partial-waves approach is developped and leads to solve very efficiently the case of a planar defect. The possibility of treating more general defects is briefly discussed

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49

Bingham, Jill Paisley. "Ultrasonic guided wave interpretation for structural health inspections". W&M ScholarWorks, 2008. https://scholarworks.wm.edu/etd/1539623538.

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Structural Health Management (SHM) combines the use of onboard sensors with artificial intelligence algorithms to automatically identify and monitor structural health issues. A fully integrated approach to SHM systems demands an understanding of the sensor output relative to the structure, along with sophisticated prognostic systems that automatically draw conclusions about structural integrity issues. Ultrasonic guided wave methods allow us to examine the interaction of multimode signals within key structural components. Since they propagate relatively long distances within plate- and shell-like structures, guided waves allow inspection of greater areas with fewer sensors, making this technique attractive for a variety of applications.;This dissertation describes the experimental development of automatic guided wave interpretation for three real world applications. Using the guided wave theories for idealized plates we have systematically developed techniques for identifying the mass loading of underwater limpet mines on US Navy ship hulls, characterizing type and bonding of protective coatings on large diameter pipelines, and detecting the thinning effects of corrosion on aluminum aircraft structural stringers. In each of these circumstances the signals received are too complex for interpretation without knowledge of the guided wave physics. We employ a signal processing technique called the Dynamic Wavelet Fingerprint Technique (DFWT) in order to render the guided wave mode information in two-dimensional binary images. The use of wavelets allows us to keep track of both time and scale features from the original signals. With simple image processing we have developed automatic extraction algorithms for features that correspond to the arrival times of the guided wave modes of interest for each of the applications. Due to the dispersive nature of the guided wave modes, the mode arrival times give details of the structure in the propagation path.;For further understanding of how the guided wave modes propagate through the real structures, we have developed parallel processing, 3D elastic wave simulations using the finite integration technique (EFIT). This full field, numeric simulation technique easily examines models too complex for analytical solutions. We have developed the algorithm to handle built up 3D structures as well as layers with different material properties and surface detail. The simulations produce informative visualizations of the guided wave modes in the structures as well as the output from sensors placed in the simulation space to mimic the placement from experiment. Using the previously developed mode extraction algorithms we were then able to compare our 3D EFIT data to their experimental counterparts with consistency.

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50

Spratt, William. "Design and Testing of an Ultrasonic Torsional Wave Sensing Platform". Fogler Library, University of Maine, 2009. http://www.library.umaine.edu/theses/pdf/SprattW2009.pdf.

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