Dissertations / Theses on the topic 'Contrôle Santé Intégré (CSI)'
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Kergosien, Nina. "Instrumentation de plaque composite de type aéronautique pour le contrôle santé intégré." Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0008.
SHM systems are currently being developed to check the integrity of aircraft composite materials. These systems will help optimize maintenance by enabling real-time monitoring of structural condition, or spot-checking of parts that are difficult to access using conventional NDT methods. Composite materials offer the possibility of integrating a SHM system directly into the material. In this way, the instrumentation is protected from the environment and surface bonding issues are resolved. The aim of this thesis is to determine the effects of integrating piezoelectric transducers into the core of an aeronautical laminated CFRP composite on their Lamb-wave emission and reception abilities, in order to demonstrate the advantages and disadvantages for the design of a defect detection SHM system. Thin PZT transducers proved to be the most suitable ones for integration, as they can withstand the processing conditions of an autoclave-processed composite (7 bar and 180°C). They are also capable of transmitting and receiving guided waves, which are propagating in the plates. Moreover, the integration method was adapted to preserve the integrity of the PZTs and to optimize their ability to transmit waves in a composite. In order to assess the effectiveness of the integration, electromechanical impedance measurements were made a fast checking process. Characterization of qA0 mode wavefield transmitted by embedded PZT was carried out experimentally. Surface-bonded and embedded PZT were excited at frequencies between 30 and 200 kHz, while out-of-plane displacements were measured with a laser vibrometer. The ability of the embedded PZT to detect a simulated magnet-type defect are also studied in pitch-catch tests, and compared with the behavior of surface-bonded PZT to the composite surface. A dynamic finite element modelling study was then conducted to highlight the physical phenomena induced by the integration of a PZT in the composite core. The direction of the plies in contact with the embedded PZT, the depth of integration and the coupling of the PZT with the composite are influencing the ultrasonic transduction mechanism. Furthermore, it appears that the stresses induced by the PZT actuator cannot be simplified by the pin-force model usually used to load a PZT on an isotropic material surface in flaw detection models. These stresses are not radially oriented and depend on the PZT electrode considered, as well as on the wave generation frequencies
SAINTHUILE, Thomas. "Récupération d'Energie Vibratoire pour Systèmes de Contrôle Santé Intégré de Structures Aéronautiques." Phd thesis, Université de Valenciennes et du Hainaut-Cambresis, 2012. http://tel.archives-ouvertes.fr/tel-00819117.
Druet, Tom. "Tomographie passive par ondes guidées pour des applications de contrôle santé intégré." Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0032/document.
This manuscript presents a baseline-free quantitative method for the imaging of corrosion flaws present in thin plates. This method only requires an embedded guided waves sensors network in a fully passive way. The field ofapplications are Structural Health Monitoring (SHM) of critical structures with heavy constrains on both sensors intrusiveness and diagnostic reliability. A promising solution allowing to increase the number of measurement points without increasing the intrusiveness of the system is provided by the Fiber Bragg Gratings (FBGs). However, unlike piezoelectric transducers generally used in SHM, the FBGs cannot emit elastic waves. The idea consists in using passive methods in order to retrieve the Green function from elastic diffuse fields - naturally present in structures - measured simultaneously between two sensors. In this manuscript, two passive methods are studied: the ambient noise correlation and the passive inverse filter. It is shown that the latter gives better results when coupled with tomography. Several tomography algorithms are assessed with numerical simulations and then applied to active and passive datasets measured by a PZT network. In order to make passive tomography robust, a time of flight identification method is proposed, based on a time-frequency representation. Finally, a novel experimental demonstration of passive measurements with FBGs only is presented, suggesting high potential for FBGs passive tomography
Sainthuile, Thomas. "Récupération d'Energie Vibratoire pour Systèmes de Contrôle Santé Intégré de Structures Aéronautiques." Thesis, Valenciennes, 2012. http://www.theses.fr/2012VALE0036/document.
The aim of this thesis is to develop a self-powered Structural Health Monitoring (SHM) system for aeronautical applications. This system has to be fully autonomous and has to be able to carry out SHM tasks such as damage detection and location. The energetic autonomy of the system is provided by a vibrational energy harvesting technology using bonded SHM piezoelectric transducers. In this document,an analytical model of the energy harvesting process has been proposed. This model, validated by the Finite Element Method (FEM), allows the optimization of the energy harvesting system by determining the ideal type of transducers as well as their optimal dimensions and locations. Then, this model has been applied to a configuration aiming to be more representative of the in-flight vibrations experienced by a structure. Good agreement has been found between the analytical simulation and the experimental measurements. A power of 1.67mW has been harvested and the wideband capability of the transducers has been verified. Afterwards, the possibility of using the vibrational energy harvesting technology to control composite structures on assembly line has been investigated. For this case study, a transducer strategically located nearby an available power supply generates Lamb waves throughout the structure to tackle the absence of natural vibration. The remaining sensors, spread all over the structure, convertthe mechanical vibrations into electrical power. Using this technology, a power of 7.36mW has been harvested. Finally, this SHM system has also been able to detect a tool drop on the composite structure and to light simultaneously and autonomously a light-emitting diode (LED) simulating the consumption required to transmit the information wirelessly
Chapuis, Bastien. "Contrôle santé intégré par méthode ultrasonore des réparations composites collées sur des structures métalliques." Paris 7, 2010. http://www.theses.fr/2010PA077122.
This document presents the development of a Structural Health Monitoring (SHM) System for composite patches bonded to aluminum plates. These patches are used in aeronautic industries to repair cracked or corroded structures. The SHM System studied consists in three thin piezoelectric ceramic (PZT) discs embedded in the repair and used to generate and detect Lamb waves propagating in the structure. The defect is revealed by the echo emitted by the diffraction of the incident wave on the defect. The modelling of Lamb waves propagation in anisotropic structures enables to select the mode. In particular, the description of the focusing phenomenon shows that the use of A₀ mode has to be preferred when the anisotropy of the propagating medium is important. To set up the monitoring strategy some experiments have been performed. Pulse-echo measurements, for which the same disc is used to excite and to detect Lamb waves, are used. Moreover, it seems necessary to compare the signal measured in a given state to a baseline signal for which other non destructive techniques have checked the lack of defect in the structure. Finally, some fatigue mechanical résistance tests of a smart repair are presented. These tests have been achieved to verify that the introduction of the discs does not degrade the performances of the repair and to test the SHM System in an environment closer to operational conditions
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.
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
Abou, Leyla Najib. "Contrôle santé intégré passif par corrélation de champ acoustique ambiant : Application aux structures aéronautiques." Valenciennes, 2010. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/fa3a198c-8d6b-49e7-96ef-883d2c5a09e1.
Structural Health Monitoring (SHM) is an autonomous and permanent technique for checking the integrity of a mechanical structure. The interest of is to inspect the integrity of the structure in near real time, which increases reliability, and avoiding immobilization of the aircraft during the inspection phase, and thus reduce maintenance cost. The work presented here is devoted to the study of a passive SHM in aeronautics using an ambient noise cross correlation. Indeed, recent studies have shown a relationship between the correlation function of a diffuse field between two points, and the Green’s function between them. The aim is to exploit the mechanical vibrations in an aircraft during the flight. In a first step, the potential of this method is verified experimentally, and the problems and difficulties due to some imperfections of application are outlined. In a second step, a simulation tool is developed to better understand certain acoustic phenomena, and a solution to solve the problem caused by the imperfections of the application (non-diffuse field) is proposed and validated experimentally. Finally, an optimization of this solution is made with a quantification of the influence of certain parameters. For this purpose a statistical theoretical approach is made and compared with experimental results
Hoang, Huu Tinh. "Contrôle santé intégré passif par ondes élastiques guidées de tuyauteries pour applications nucléaires et pétrolières." Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2020. http://www.theses.fr/2020UPHF0023.
Structural Health Monitoring (SHM) consists in embedding sensors into a structure in order to monitor its health inreal time throughout its lifetime. The research works carried out in this thesis aimed at developing a new approachof SHM for the detection of corrosion/erosion in pipes. This manuscript presents a new quantitative imaging method,called passive elastic guided wave tomography, based on the use of an embedded network of piezoelectric sensors(PZT) listening and analyzing only the ambient elastic noise which is naturally generated by the fluid circulation inpipes. This passive method offers many advantages for a SHM system, such as reduction of energy consumption,simplified electronics and ability to perform an inspection while the structure is in operation. In addition, thispassive method makes SHM systems possible to use Fiber Bragg Grating sensors (FBG) which have several advantagesover traditional PZT sensors (low intrusivity, resistance to harsh environments, etc.) but which are not able to emitwaves. A first demonstration of the feasibility of corrosion/erosion imaging by FBG is illustrated experimentallythanks to a result obtained by hybrid tomography in which wave emission is performed by PZT and reception byFBG. All these works offer promising perspectives for the application of passive tomography on industrial structuresusing a pure FBG system. Among the various results presented in this thesis, we also show that corrosion/erosiondefects can be characterized by tomography on a straight pipe without the need for a baseline measurement in apristine state. It is feasible by using a new method of auto-calibration of the data used for tomography. The absenceof baseline measurement makes the method very reliable and avoid false alarms of the system. Finally, preliminarystudies on tomography for more complex structures such as a bended pipe have been realized and validated throughsimulations
Devillers, David. "Étude de faisabilité d'un contrôle santé intégré de plaques composites sandwich utilisant des ondes de Lamb." Paris 7, 2002. http://www.theses.fr/2002PA077070.
Grésil, Matthieu. "Contribution à l'étude du contrôle de santé intégré associé à une protection électromagnétique pour les matériaux composites." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2009. http://tel.archives-ouvertes.fr/tel-00763266.
Gresil, Matthieu. "Contribution à l'étude du contrôle de santé intégré associé à une protection électromagnétique pour les matériaux composites." Cachan, Ecole normale supérieure, 2009. http://tel.archives-ouvertes.fr/tel-00763266.
The quality and variety of their properties, the composite materials are widely used in naval military. The possibility of integrating smart function in materials represents a significant advance for their uses. To reduce the costs of inspections required, it is preferable to use materials integrating a health monitoring. Thus, we sought to define a nondestructive evaluation method, to provide better security at lower cos structures. The Lamb waves were seen in their work this concept is generalized to the case of anisotropic laminated materials. The characteristics of these dispersive modes have been studied in relation to mechanical properties. Achieving instrumented plates allowed the detection of realistic defects by defining damage parameters. The location of defects was estimated by a signal processing based on discrete and continuous wavelet transform. Finally, the Lamb modes were modeled using the finite element method. In parallel, an electromagnetic shielding based on the electrical conductivity of carbon fibers have allowed us to obtain a high level of shielding effectiveness for the military naval sector. In particular, the importance of electrical continuity between the different plates on the measured performance was developed. A model based on the distributed point source method allowed us to model the propagation of electromagnetic waves. The originality of this study is the integration of two functions in composite materials
Hourany, Karl. "Contribution à l'exploitation du bruit ambiant pour le contrôle santé intégré passif des barres et des tubes." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0039/document.
The works presented in this manuscript are based on previous studies conducted at the Institute of Electronics Microelectronics and Nanotechnology of the University of Valenciennes and Hainaut Cambrésis. They concern the development of an embedded monitoring system for the control of materials and structures used in different transport domains (pipeline, aerospace, railway ...). This is the Structural Health-Monitoring principle. The idea is to integrate sensors into the surfaces of the controlled structures in order to achieve a non-destructive control system for the control of the latter during their entire lifetime. First the work done at the laboratory in this domain, are illustrated, some definitions such as ultrasonic waves, the Non Destructive Testing and the Structural Health Monitoring are recalled, to switch later to the explanation of the passage from an active control to a passive control. In a second step, an images comparison algorithm based on the local minima present in these images has been proposed and tested on simple images of sixteen pixels and was used to test the degree of resemblance between them. The explanation of the developed algorithm is divided into two parts. In the first one, we explain how to extract the local minima of an image. The second part describes the procedure for determining the rate of resemblance between the images. The simulation of the propagation of a signal in a reverberant plate and the obtaining of the frequency time images corresponding to filtered correlation (autocorrelation) has been described. The algorithm was validated on those images allowing the localization of an unknown source position
Grondel, Sébastien. "Contribution à l’optimisation du contrôle santé intégré par ondes de Lamb : Application à la surveillance de structures aéronautiques." Valenciennes, 2000. https://ged.uphf.fr/nuxeo/site/esupversions/78128995-960f-471e-a183-bca2c37f9aa6.
Methenni, Hajer. "Modélisation mathématique et méthode numérique pour la simulation du contrôle santé intégré par ultrasons de plaques composites stratifiées." Electronic Thesis or Diss., Institut polytechnique de Paris, 2021. http://www.theses.fr/2021IPPAE002.
This thesis is embedded in the context of « Structural Health Monitoring ». This method of non-destructive testing aiming at monitoring in-situ an engineered structure is increasingly used in numerous industrial fields, e.g. the aeronautics industry. It is based upon elastic guided waves propagating over large distances. The interactions between incident wave fields and structural defects are gathered through a network of receiving sensors. The dispersive nature of guided waves, combined with the inherent anisotropy of some industrial materials, such as composites, makes the interpretation of the output signals difficult. The goal of this thesis is to provide meaningful numerical tools enhancing the understanding and analysis of propagation and interaction phenomena, appearing during the control experiment. The thesis lies between the physical and mathematical modelling of elastic waves and the construction of relevant numerical schemes, altogether in an innovating industrial context involving complex geometries and materials
El, Youbi Faysal. "Etude de transducteurs multiéléments pour le contrôle santé intégré par ondes de Lamb et développement du traitement de signal associé." Valenciennes, 2005. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/42645aa4-651d-459d-b3dd-ce534a2906da.
This work concerns firstly, the study of an Integrated Health Monitoring System (IHMS) based on the generation and the reception of Lamb waves by multi-element transducers and secondly, the development of a signal processing tool able to identify all present Lamb modes and to study their sensitivities to the presence of defects. To achieve this task, a theoretical relationship between the Short Time Fourier Transform (STFT) and the Two Dimensional Fourier Transform (2D-TF) was demonstrated. The comparison of the amplitudes obtained was made possible by the application of these two signal processing techniques. This allowed firstly, to improve the Lamb modes identification and secondly, to note the presence of parasitic modes. In addition, Finite Elements Modeling (FEM) of the system revealed that the piezoelectric elements composing emitter and receiver transducers were at the origin of these parasitic modes. In order to eliminate these parasites, the solution suggested was to reduce elements thickness. Moreover, this study showed that the transducer in reception could be improved by developing a segmented transducer. Once this system optimized, a hole was introduced in the centre of the plate in order to study the sensitivity of the modes to its presence and its size. The received signals were then treated. The results obtained made possible to test the sensitivity of the modes with respect to the size of this hole. Thus, they show clearly the effectiveness of the system developed for structural health monitoring
Duquenne, Laurent. "Développement d'une méthode d'estimation de la génération transitoire d'ondes de Lamb : Application à la modélisation d'un système de contrôle santé intégré." Valenciennes, 2003. http://ged.univ-valenciennes.fr/nuxeo/site/esupversions/2807daf5-ac69-4a5c-a2ae-2ab8d5e7fb56.
For several year, research has been undertaken to integrate a nondestructive evaluation system in the structure with the objective to facilitate regular monitoring. This " health monitoring system " would allow the selection of the components requiring repairs. The technique considered is the use of the Lamb waves generated by integrated piezoelectric transducers which are able to emit or to receipt this waves. Nevertheless, the control of the generated waves by these transducers is still a problem. The aim of this work is then to develop a method allowing to estimate the transient generation of Lamb wave. The advantage of the hybrid method finite elements/Normal mode expansion is the direct computation of the contribution of each mode. The assumptions have been checked and the results have been confronted successfully with experimental results
Lizé, Emmanuel. "Détection d'endommagement sans état de référence et estimation de la température pour le contrôle santé intégré de structures composites par ondes guidées." Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0058/document.
This thesis work concerns the Structural Health Monitoring (SHM) of aeronautical composite structures by guided waves with piezoelectric transducers (PZT). Conventional detection methods are based on the comparison of signals from the inspected structure in the current state with those measured in a healthy state (the baseline). Temperature significantly alters the measured signals and the associated diagnosis if its influence is not considered in the baseline. Also, the acquisition of the baseline is very constraining for the deployment of SHM systems in real conditions. The first contribution of this thesis is the estimation of the temperature field from the PZT measurements (modal frequency shift and static capacity), which allows to compensate the effect of temperature in the baseline without adding dedicated sensors. The second contribution of this thesis concerns baseline free methods. The detection performance of four methods are compared (reciprocity principle, amplitude variation, Lamb mode analysis and instantaneous baseline) on a numerical model and experimental cases of damages at different temperatures on a highly anisotropic composite plate. The results obtained show that the decomposition of Lamb wave modes in signals measured via dual PZTs (PZTs consisting of two concentric electrodes - a ring and a disk - on their upper side) significantly improves the detection performance of these methods. A dimensioning process for the deployment of these methods on complex anisotropic structures is proposed. These results open up promising opportunities that potentially contribute to the transfer of SHM technologies from laboratories to industry
Krishna, Aditya. "Topological Imaging of Tubular Structures using Ultrasonic guided waves." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0111.
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
Chaouch, Olfa. "Tomographie passive des ondes acoustiques : Prédiction et identification à partir du bruit ambiant." Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1035/document.
The work presented is in the domain of SHM. An identification method based on the cross correlations functions between piezoelectric sensors was proposed and gave birth to two criterion of identification. The first is a visual criterion, it is based on the superposition of the envelopes of the cross correlation functions obtained by Hilbert transform for two configurations, the first is a defect free configuration of reference and the other is with defect.The second criterion is numerical; it is the mean of the differences between two envelopes. The performance of these criterions was tested first on an aluminum plate in free edges conditions, using a source located in space; the intensity of this source was not controlled. The results of the first experiment has certainly shown the sensitivity of these criterion to the appearance of defects despite the randomness of the source, but also highly sensitivity to changes in the position of the source was found. In the second experiment a source not localized in space was used, and the plate was in clamped edges conditions. The proposed criterions have been tested using a single frequency sine signal as a source first and using a white noise filtered signal secondly. With the proposed criterion, the defect was certainly identified; however, it remains to find a way to locate and to characterize the defect
Goutaudier, Dimitri. "Méthode d'identification d'un impact appliqué sur une structure admettant des modes de vibration basse fréquence faiblement amortis et bien séparés." Thesis, Paris, CNAM, 2019. http://www.theses.fr/2019CNAM1225/document.
Many industrial structures operate in an environment with a high risk of collision. The detection of impacts and the assessment of their severity is a major preoccupation in Structural Health Monitoring. This work deals with the development of an impact identification technique that is applicable to a large composite structure, numerically robust and time efficient, and that requires a low number of sensors. The first step was to describe the image of the impact point in the vibration response as a modal participation vector. The idea was to introduce the existence of a discriminating modes familly to make a bijective link between the modal participations and the impact point. A least-squares procedure is developed to estimate those modal participations by measuring the vibration response of a single point on the structure. The second step was to extend the procedure to the identification of a parametric law representing the impact load history. Some conditions on measurement parameters and modal properties of the structure are identified to guarantee both the accuracy and the robustness of the procedure. The approach developed in this work is new regarding the state of the art: only one measurement point is considered for identifying an impact event. An experimental validation on an A350 crown panel indicates that the methodology is valid for large composite structures
Barnoncel, David. "Etude d'un système de contrôle santé intègré pour structures sandwich composites utilisant des transducteurs piézo-électriques minces." Paris, CNAM, 2006. http://www.theses.fr/2006CNAM0501.
This PhD is a study of a Integrated Health Monitoring System (IHMS) for a sandwich structure : Rafale nose. The goal of the IHMS is to detect, localize and estimate the size of damages appearing during the life. The characterization of the damages is made with Lamb waves that propagate in the structure. In order to have an integrated system we use slim piezo-electric devices. The use of the flexural wave at low frequencies is adapted to the shape of the damages. The method used with the IHMS needs to knowledge of the sandwich Lamb waves with charateristics (dissipation, Phases speed). In order to measure theses characteistics which have build a NDE system. That have also give a visualisation of the interaction of the waves with damages. The use of special signal processing method and a base references made by simulation with the IHMS signal gives a method to detect, localise and estimate the size of a real damage
Zhou, Huan. "Etude théorique et expérimentale de systèmes à ondes de surface dans des structures multicouches piézomagnétiques pour des applications en contrôle santé intégré de MEMS par imagerie acoustique non linéaire." Phd thesis, Ecole Centrale de Lille, 2014. http://tel.archives-ouvertes.fr/tel-00991915.
Taupin, Laura. "Modélisation des méthodes ultrasonores de surveillance de structures aéronautiques instrumentées en vue de leur optimisation." Phd thesis, Palaiseau, Ecole polytechnique, 2011. https://pastel.hal.science/docs/00/65/35/53/PDF/manuscrit_LTAUPIN.pdf.
Structural health monitoring (SHM) using elastic guided waves is under study for the inspection of aircraft multilayered composite stiffened plates. Two simulation tools are developed to discuss its feasibility. The first predicts the wave propagation in the plates as a modal series by the semi-analytical finite element method (SAFE). The second tool is a hybrid computing predicting diffraction of guided waves in arbitrary incidence on a composite stiffener. The diffraction is calculated locally by finite element (FE), the global propagation by the SAFE method. The link between the two calculations is done through transparent boundaries of the FE domain avoiding artificial reflections, allowing the projection of the field in the stiffener on the modes of the plate and minimizing the FE computation domain. The tools are used in typical cases, the predictions are discussed in view of the industrial application of SHM
Taupin, Laura. "Modélisation des méthodes ultrasonores de surveillance de structures aéronautiques instrumentées en vue de leur optimisation." Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00653553.
Nerlikar, Vivek. "Digital Twin in Structural Health Monitoring for Aerospace using Machine Learning." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASG080.
Modern engineering systems and structures often utilize a combination of materials such as metals, concrete, and composites, carefully optimized to achieve superior performance in their designated functions while also minimizing overall economic costs. Primarily, engineering structures are subjected to dynamic loads during their operational life. The manufacturing issues and/or the perpetual dynamic operations often lead to some changes into a system that adversely impact its present and/or future performance; these changes can be defined as damage. The identification of damage is a crucial process that ensures the smooth functioning of equipment or structures throughout their life cycle. It alerts the maintenance department to take the necessary measures for repair. Structural Health Monitoring (SHM) is a potential damage identification technique which has attracted more attention in the last few decades. It has the capability to overcome the downsides of traditional Non-Destructive Testing (NDT). In this thesis, we used Ultrasonic Guided Waves (GW) technique for SHM. However, sensitivity of GW to Environmental and Operational Conditions (EOC) modify the response signals to mask defect signatures. This makes it difficult to isolate defect signatures using methods such as baseline comparison, where damage-free GW signals are compared with current acquisitions Baseline-free methods can be an alternative, but they are limited to simple geometries. Moreover, high sensitivity of GW to EOC and measurement noise poses a challenge in modelling GW through physics-based models. The recent advancements in Machine Learning (ML) has created a new modelling axis, including data-driven modelling and physics-based modelling, often referred to as Scientific ML. Data-driven modelling is extremely helpful to model the phenomena that cannot be explained by physics, allowing for the isolation of subtle defect signatures and the development of robust damage detection procedures. However, ML-based methods require more data to capture all the information to enhance the generalization capability of ML models. SHM, on the other hand, tends to generate mostly damage-free data, as damage episodes seldom occur. This particular gap can be filled through physics-based modeling. In this approach, the modeling capabilities of physics-based models are combined with measurement data to explain unexplainable phenomena using ML. The primary objective of this thesis is to develop a data-driven damage detection methodology for identifying defects in composite panels. This methodology is designed for monitoring similar structures, such as wind or jet turbine blades, without requiring pristine (damage-free) states of all structures, thereby avoiding the need for direct baseline comparisons. The second goal is to develop a physics-based ML model for integrating physics-based simulations with experimental data within the context of a Digital Twin. The development of this physics-based ML model involves multi-fidelity modeling and surrogate modeling. To validate this model, we utilize an experimental and simulation dataset of an Aluminium panel. Furthermore, the developed model is employed to generate realistic GW responses at the required damage size and sensor path. These generated signals are then used to compute a Probability of Detection (POD) curve, assessing the reliability of a GW-based SHM system
Masmoudi, Sahir. "Comportement mécanique et caractérisation par implant piézoélectrique ultrasonore intégré d'un matériau composite." Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-00955508.
Hubert, Elisa. "Vibration monitoring of an aeronautic power transmission system." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSES015.
This thesis contains the results of the research studies performed with SafranTech and the Laboratoire d’Analyse des Signaux et des Processus Industriels (LASPI) of the University of Lyon. The main subject focuses on vibratory surveillance of aeronautic power transmission systems and more specifically gearboxes.Usually, vibrations are investigated with spectral analysis by means of the common representation of the Fourier spectrum. Based on these observations, gearbox vibrations have been represented by an empirical product model: on one hand the meshing signal, with high frequency, and on the other hand the gears rotations signals, with low frequencies.Indeed, gearbox vibrations develop a line spectrum having similar characteristics with some communication signals, as a carrier signal modulated in amplitude. For the purpose of incipient fault detection, it is interesting to be able to separate low frequency signals as they usually convey more fault information. Based on these model and observation, this research work investigate the answer to the two following questions:1. To which point the vibration signals produced by gears rotation can be explained by the representation as a product?2. Given a signal, is it possible to rebuild it by estimating the two components? Is the solution unique?In order to answer those questions, the given model was formulated as an optimization problem. Then a new tool has been defined to represent the discrete spectrum of gearbox vibration signal as a matrix containing the Fourier coefficients. This work has proven equivalence between the two representations of the matrix product of two vectors and the temporal multiplication of two signals. Furthermore, it allowed us to link the remote fields of signal demodulation and low rank approximation.This new separation and estimation approach for gearbox vibration signals has shown theoretical interesting performances, close to the ideal and allowed us to perform efficient incipient fault detection on real gearbox vibration dataset
Sadoudi, Laïd. "Étude et développement d'une plateforme de communication pour les réseaux de capteurs acoustiques sans fil : application au contrôle-santé des rails par corrélation du bruit ambiant." Thesis, Valenciennes, 2016. http://www.theses.fr/2016VALE0018/document.
Structural Health Monitoring (SHM) reduces human inspection requirements through automated monitoring, reduces maintenance costs by early detection of defects before they escalate, and improves safety and reliability of services. The work presented in this thesis aims to design a wireless communication platform for railway structures health monitoring. The control principle is based on the reconstruction of impulse responses (Green’s functions) by correlation of random noise propagated in the medium. In this work, direct comparison between an active emission-reception response and the estimated noise correlation function has confirmed the validity of the equivalence relation between them. Thus, we have demonstrated the applicability of the correlation functions for local defect detection in a rail. Then, we conducted an experimental study on the characterization of a ZigBee transmission in terms of path loss and communication range in multiple environments. In the railway environment under test, we showed the adequacy with the range of a ZigBee single-hop transmission (within a radius of 76m). Furthermore, a flexible solution for sensors synchronization during the sampling process, based on IEEE 802.15.4 standard was proposed and validated by a measurement campaign. It has been demonstrated that this approach provides a precision of a few hundred nanoseconds. A wireless communication-platform prototype based on the ZigBee/IEEE 802.15.4 technology has been implemented and deployed on a rail sample. This solution enabled the validation of the platform performances, once the data collected by the transducers, the information is transmitted by a ZigBee link to a base station where detection algorithms are applied
Hafidi, Alaoui Hamza. "Imagerie topologique ultrasonore des milieux périodiques." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0388/document.
The detection, localization and monitoring of the evolution of defects in periodic media and waveguides is a major issue in the field of Non-Destructive Testing (NDT). Wave propagation in such media is complex, for example when the velocity depends on the frequency (dispersion) or direction of propagation (anisotropy). The signature of the defect can also be "embedded" in the acoustic field reflected by the structure (reverberation or multiple diffusion). It is to answer these stakes of the size that the Topological Optimization (TO) has been adapted to the problems of diffraction of the acoustic waves by infinitesimal defects in order to obtain reflectivity images of the inspected media. The method can be applied to all kinds of media, regardless of their complexity, provided an exact simulation of the wave propagation in a reference medium (without defects) is performed. Inspired by the TO, the work of this thesis proposes to implement qualitative imaging methods adapted to the specificities of Phononic Crystals (PC) and waveguides. First, we focus on the description of the mathematical formalism of Topological Optimization and Full-Waveform Inversion (FWI). Although these methods do not try to solve the same inverse problems, we highlight their similarities. In a second step, we apply Topological Imaging (TI) to the inspection in pulse-echo configuration of weakly heterogeneous media. Thirdly, we draw inspiration from TI to define a new variant of this method called Hybrid Topological Imaging (HTI).We apply these methods for the pulse-echo configuration inspection of PCs created by steel rods immersed in water.We compare the performance of these methods according to the kind of defects in the PC. Numerical simulations for some case studies are supported by conclusive experimental trials. In a fourth step, we adapt the TI to a pitch-catch configuration in order to implement a new method of Structural Health Monitoring (SHM) of waveguides. In this regard, we have developed a new imaging method that is better suited than TI to pitch-catch configurations
Cury, Alexandre. "Techniques d'anormalité appliquées à la surveillance de santé structurale." Phd thesis, Université Paris-Est, 2010. http://tel.archives-ouvertes.fr/tel-00581772.
Kulakovskyi, Andrii. "Développement d’un système SHM pour aéronef par ondes élastiques guidées." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX021/document.
A guided wave-based structural health monitoring (SHM) system aims at determining the integrity of a wide variety of plate-like structures, including aircraft fuselages, pipes, tanks etc. It relies on a sparse array of piezoelectric transducers for guided waves (GWs) excitation and sensing. With a number of benefits, these waves are standing out among other methods as a promising method for the inspection of large structures. They can propagate on significant distances with small attenuation while being sensitive to surface and subsurface defects.This thesis presents studies conducted with the purpose of developing such a GWs-based SHM system that is capable of efficient defect detection, localization and sizing aeronautical plate-like structures made of aluminum and composite materials. Simulation and data-driven approaches are presented for determining principal characteristics of propagating GWs, namely modal group and phase velocities, 3D Green's functions etc. in structures of interest. They are then used for GWs signals processing in order to compute images representing the integrity of studied structures. This work also provides a comprehensive overview of DAS, MV and Excitelet defect imaging algorithms, determines their performance using statistical analysis of an extensive dataset of simulated guided waves imaging (GWI) results and proposes a method for sparse defect imaging.While defect detection and localization are straightforward from the image analysis, the defect sizing is a more complex problem due to its high dimensionality and non-linearity. It is demonstrated that this problem can be solved by means of machine learning methods, relying on an extensive database of simulated GWI results. Aforementioned defect imaging methods are baseline demanding. They are efficient under stationary operational conditions but vulnerable to environmental variations, especially to the temperature fluctuation.Finally, this work presents studies on the robustness of GWI methods against thermal effects, and a defect detection model capable of analyzing deteriorated GWI results is proposed. Different techniques for thermal effects compensation are reviewed, and improvements are proposed. Their effectiveness is validated for aluminum plates but further improvements are required to translate these techniques to composite plates
Hamdi, Seif Eddine. "Contribution au traitement du signal pour le contrôle de santé in situ de structures composites : application au suivi de température et à l’analyse des signaux d’émission acoustique." Thesis, Le Mans, 2012. http://www.theses.fr/2012LEMA1017/document.
Structural health monitoring (SHM) of materials is a fundamental measure to master thedurability and the reliability of structures in service. Beyond the industrial and human issuesever increasing in terms of safety and reliability, health monitoring must cope with demandsincreasingly sophisticated. New health monitoring strategies must not only detect and identifydamage but also quantify the various phenomena involved in it. To achieve this objective, itis necessary to reach a better understanding of the damage process. Moreover, they frequentlyoccur as a result of mechanical and environmental stresses. Thus, it is essential, first, to developsignal processing methods for estimating the effects of environmental and operational conditions,in the context of the analysis of precursor events of damage mechanisms, and on theother hand, to define the damage descriptors that are the most suitable to this analysis. Thisstudy proposes signal processing methods to achieve this goal. At first, to the estimation ofexternal effects on the scattered waves in an active health control context, in a second step, tothe extraction of a damage indicator from the signals analysis of acoustic emission in a passivehealth monitoring context.In the first part of this work, four signal processing methods are proposed. These allow takinginto account the variation of environmental conditions in the structure, which in this thesis,were limited to the particular case of temperature change. Indeed, temperature changes have theeffect of altering the mechanical properties of the material and therefore the propagation velocityof ultrasonic waves. This phenomenon then causes a dilation of the acoustic signals that shouldbe estimated in order to monitor changes in temperature. Four estimators of dilation coefficientsare then studied: the intercorrelation sliding window, used as reference method, the stretchingmethod, the minimum variance estimator and the exponential transform. The first two methodshave already been validated in the literature while the latter two were developed specificallyin the context of this study. Thereafter, a statistical evaluation of the quality of estimates isconducted through Monte Carlo simulations using synthetic signals. These signals are basedon a scattered signal model taking into account the influence of temperature. A raw estimateof the computational complexity of signal processing methods also completes this evaluationphase. Finally, the experimental validation of estimation methods is performed on two types ofmaterial: First, in an aluminum plate, homogeneous medium whose characteristics are known,then, in a second step in a highly heterogeneous environment in the form of a compositeglass/epoxy plate. In these experiments, the plates are subjected to different temperatures in acontrolled thermal environment. The temperature estimates are then faced with an analyticalmodel describing the material behavior.The second part of this work concerns in situ characterization of damage mechanisms byacoustic emission in heterogeneous materials. Acoustic emission sources generate non-stationarysignals. The Hilbert-Huang transform is thus proposed for the discrimination of signals representativeof four typical sources of acoustic emission in composites: matrix cracking, debondingfiber/matrix, fiber breakage and delamination. A new time-frequency descriptor is then definedfrom the Hilbert-Huang transform and is introduced into an online classification algorithm. Amethod of unsupervised classification, based on the k-means method, is then used to discriminatethe sources of acoustic emission and the data segmentation quality is evaluated. Thesignals are recorded from blank samples, using piezoelectric sensors stuck to the surface of thematerial and sensitive samples (sensors integrated within the material)
Lemartinel, Antoine. "Development of self-sensing structural composites parts for wind mill blades monitoring." Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS466.
The growing demands for electrical energy, especially renewable, is boosting the development of wind turbines equipped with longer composite blades. To reduce the maintenance cost of such huge composite parts, the structural health monitoring (SHM) is an approach to anticipate and/or follow the structural behaviour along time. To do so, a proper instrumentation is necessary and has to be as less intrusive as possible. To this end, the development of carbon nanotube- epoxy Quantum Resistive Sensor (QRS) is presented. QRS can be as well glued on the surface or embedded in the core of the composite structure during the stacking sequence. During manufacturing, both the temperature and resin crosslinking can be detected with the change in the QRS electrical characteristics. Once the structural part is made, the effect of the external parameters (strain rate, temperature, humidity, Poisson ratio…) on the electrical characteristics of QRS has been studied. During the composite life, the QRS electrical behaviour has also demonstrate its capability to detect the initiation and propagation of damage until final failure. A non-intrusive monitoring with QRS of the structure life cycle, from manufacturing until final breakage is therefore possible
Serey, Valentin. "Sélectivité modale d'ondes ultrasonores dans des guides d'ondes de section finie à l'aide d'éléments piézoélectriques intégrés pour le SHM." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0403/document.
SHM systems (Structural Health Monitoring) based on ultrasonic guided waves propagation are used for large structures, e.g. in Aerospace or Civil Engineering. Lamb or SH waves are usually employed as they propagate over long distances in plate-like structures while probing the entire thickness. However less conventional modes propagate in wave guides with finite crosssection,such as bars, rails or pipes. The number of modes can be very high even at low frequencyin this type of guide, and it is important to carefully select a specific mode. Current methods for modal selectivity, based on the use of several emitters, usually consider identical PZT elements(same sensitivity, same frequency response, etc.) and do not account for real experimental conditions and possible differences (variable coupling between transducers, flawed alignment,variable electronic response, etc.). This work presents a global methodology for modal selectivity in waveguides with finite cross-section, using several piezoelectric elements attached to their surface. This selectivity is based on experimental measurements, with a 3D laser vibrometer,of the amplitudes of the modes generated by each emitter. An optimization process allows to inverse the problem in order to maximize the amplitude of the desired mode, then generated by exciting all the emitters at once. This process requires knowing dispersion curves as well as the displacements of the various modes, calculated with SAFE 2D method. The methodology is tested through numerical simulations and experiments on an aluminium rectangular bar instrumented with 8 PZT elements on top. The method efficiency to generate different pure modes,and to detect and locate calibrated defects, is demonstrated for the aluminium bar. Its potential for SHM application of more complex structures is studied, like a rail or an adhesively bonded composite structure
Zhu, Boyao. "Identification and metamodeling characterization of singularities in composite, highly dispersive media." Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0006.
Structural health monitoring (SHM) plays a crucial role in many industrial fields to ensure the safety, reliability, and performance of critical structures. The development of various types of sensors, data analysis, and wireless communication systems, enables the collection in situ of data attesting to the real-time state of structures within the framework of SHM modules helping for more accurate and automated decision-making processes. However, the SHM modules require data basis characterizing safe and damaged structures. Simulations based on numerical modelling such as finite element methods, are often used to construct this data basis. However, this approach is very time-consuming especially when the finite element model is complex, which is often the case due to the increasing complexity of structures. This thesis is within this framework. Indeed, it deals with the problem of efficiently obtaining damage-sensitive features of complex composite structures. More specifically, it aims to define and develop efficient numerical tools helping for SHM of complex composite structures. Hence, model reduction and metamodeling approaches based on the Wave-finite element (WFE) and Kriging methods respectively are proposed and investigated. So, the main objective of the present work is to assess the potential of the combination of the WFE and kriging metamodeling to be useful and efficient in predicting the structural and dynamic characteristics of complex composite structures. This efficiency is quantified by the prediction accuracy and the involved cost. Based on the predicted dynamic properties, some damage-sensitive indicators (such as amplitudes, natural frequencies, phase shifts) are defined and exploited to evaluate the health status of the considered structures.Based on the accomplished studies, it is shown that the proposed strategy, namely the Kriging-based WFEM, can ensure an interesting efficiency resulting in a suitable accuracy of predictions of the structural and dynamical properties while involving a smaller cost than the WFEM-based calculations. Moreover, the proposed strategy has kept the same sensitivity levels of dynamic properties to the considered damages (cracks and delamination) with the associated indexes. The strategy proved to be more efficient when using the adaptive sampling scheme with kriging
Boniface, Antoine. "Détection et évaluation de l'endommagement mécanique du béton par émission acoustique." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0954/document.
Nuclear safety issues involve the evaluation of existing installations, and in particular of containment systems. The enclosure is a double sarcophagus of reinforced concrete. It constitutes a protective barrier to both the reactor of an external aggression but also an agent of protection of the exterior of a possible leak in case of accident. The correct functioning of the enclosure is ensured in full filling of the functions of resistance and sealing. The evaluation of these two functions in particular for monitoring the state of cracking of the enclosure.The cracking of the concrete is associated with the development of micro-cracks which appear when the local stresses of the material are exceeded. As a result of these micro-cracks, the release of energy is propagated in the material in the form of mechanical waves. This phenomenon is called "acoustic emission".Acoustic emission (EA) is also the name of the technique used to directly measure the manifestation of these micro-cracks. The EA consists of recording, by means of a network of piezoelectric sensors placed on the surface, the ultrasonic waves emitted by the micro-cracks within the material. This particularity of the AE places it at the forefront of inspection techniques for monitoring the damage and cracking of concrete.The accuracy of the existing location tools is highly dependent on the methods of analyzing the recorded EA signals. This dependence constitutes an important lock that must be lifted in order to ensure the spatial follow-up of the most reliable crack propagation possible. Moreover, the identification of the source mechanisms of EA is a crucial stake because it makes it possible to characterize the different phenomena that intervene during the propagation of crack.On the basis of tests of cracking and thermal damage of the concrete we shown the impact of the strategies of localization on the representation of the damage. Based on our results, we proposed a spatial analysis based on the acoustic event density and the released energy allowing to follow the propagation of the thermal damage also of the cracking in the specimens. An original analysis of the signals by cross-correlation is proposed in order to group the signals into classes. Finally, the methods developed were applied during crack opening and referencing trials on the Onera blower and on a 1/3 scale model of a nuclear power plant confinement enclosure called “Vercors”
Tuloup, Corentin. "Process and structural health monitoring of Polymer-Matrix Composites (PMC) using embedded piezoelectric transducers." Thesis, Compiègne, 2020. https://bibliotheque.utc.fr/Default/doc/SYRACUSE/2020COMP2593.
This innovative work studies the interest of integrating piezoelectric transducers (ceramic and/or polymer-based) within Polymer- Matrix Composite materials (PMC) to perform real-time and in-situ monitoring of their manufacturing process (Process Monitoring PM) as well as their lifespan (Structural Health Monitoring SHM). To do this, the piezoelectric transducers were integrated into the heart of the fibrous stacks using an innovative methodology developed within the "Materials and Surfaces" research team at the Roberval laboratory. The Liquid Resin Infusion (LRI) manufacturing system used (PM campaign), as well as the resulting samples tested mechanically (SHM campaign), were multi-instrumented using several Non-Destructive Testing devices (NDT: Acoustic Emission (AE), Infrared Thermography (IRT), Digital Image Correlation (DIC), etc.) in order to establish multi-physical couplings between the signals of external NDT techniques and the internal signature (electrical capacitance) coming from the transducers integrated into the heart of the material. In PM, the piezoceramic (PZT) transducers were found to be sensitive to the various key steps of the LRI process (flow front passing, impregnation, end of injection, chemo-physical transitions during curing and associated consolidation rates) achieved at different hardener rates, and able to detect manufacturing defects. These results showed great potential, worthy of future use on an industrial scale. In SHM, after verification of the non-intrusiveness of the ceramic and polymer-based transducers integrated into the heart of the mechanical test specimens, the polymer transducers allowed a real-time evaluation of the triaxial strain state and the rigidity loss experienced by the host PMC during its mechanical loading. However, despite a Non-Working Threshold (NWT) linked to the brittleness of their constitutive material, the piezoceramic transducers have shown a high sensitivity to the detection and monitoring of damage in real-time when they are positioned intelligently with respect to the mechanical stress. These thesis works ended with a first attempt aimed at transposing the knowledge acquired on PM and SHM of in-situ piezoelectric transducers from a 2D “laboratory” scale to a 3D structural one closer to industrial realities. The multi-instrumented manufacturing of an “Omega” stiffener PMC structure integrating 14 piezoelectric transducers (PZT and P(VDF-TrFE) copolymer) and reinforced through-the-thickness by a carbon tuft thread allowed confirming the previously evidenced PM abilities of the PZT, and showed a difference between how the electrical capacitance signals of PZT and copolymers react to the whole manufacturing process
Sharma, Sanjay. "Performance Demonstration of Guided Waves based Structural Health Monitoring system for Aerospace Application." Electronic Thesis or Diss., université Paris-Saclay, 2022. http://www.theses.fr/2022UPASG073.
Guided elastic waves emitted and received by thin piezoelectric transducers are recognized as a promising technology for several applications of Structural Health Monitoring, especially of aerospace components. Demonstration of the performances of such systems, often expressed in terms of Probability Of Detection (POD) curve, is a key enabler of the successful deployment of the technology in industry. POD curve experimental determination requires many instrumented samples making its cost prohibitive. A simulation-based approach, or model-assisted, is an attractive alternative. However, simulation in guided waves-based SHM and POD determination of such systems are so far limited due to a lack of specific methodology, procedures, appropriate statistical methods, and validation. This thesis proposes a general methodology for a model-assisted POD approach of guided waves based SHM, with a demonstration on monitoring of a growing crack from a hole in an aluminum plate. The methodology benefits from the efficient time domain transient spectral finite element simulation tool developed at CEA-List (CIVA SHM module) that allows to run the large simulation campaigns required to determine a POD curve. A new hybrid actuator model has been proposed in this work by considering the transducer frequency dependent behaviour and normal stress in addition to radial stress as a surface loads to enable the use of simulation on a higher range of excitation frequencies, suitable for the targeted application. Two recent suitable statistical methods: length-at-detection and random effects, have then been adapted to estimate and to compare the POD curve from both experimental and simulated datasets. The Bayesian approach is found to be more useful in model parameter estimation of random effects method for comparing the uncertainty bound for each model parameter from experimental and simulated datasets than Maximum Likelihood Estimation. Finally, a sample size determination study has been conducted based on the random effects method to identify how many samples are required to achieve the requirement of a particular SHM application. All these results show great confidence in the model-assisted approach to POD estimation methodology and confirm the potential of this solution as a cost-effective tool for performance demonstration of guided waves-based SHM systems
Chehami, Lynda. "Surveillance passive des milieux réverbérants par corrélation de bruit ambiant : application à la localisation de défauts." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0035/document.
Green’s functions retrieval from ambient noise correlation has recently drawn a new interest in structural health monitoring. In this manuscript, we propose an original method based on this approach to detect and locate defects (cracks, holes, grooves) in a reverberant thin plate with a limited number of sensors. Flexural waves that propagate on the plate are generated by either a set of sources distributed randomly on the surface or an ambient noise. Covariance matrices are estimated from the sparse array after damage and compared to baseline-correlation matrix recorded from the healthy plate. An evaluation criterion has developed in the form of relative noise level to predict the quality of the GF reconstruction. The differential correlation matrix w/o defect is used to localize the defect. We have shown numerically and experimentally that this technique is exploitable for defect detection and localization, despite a non-perfect estimation of the GF. We have also proposed a passive technique to identify the regions of noise. A filtering technique based on the singular value decomposition is shown to improve the detection. A secondary acoustic sources have been developped to harvesting the LF ambient noise to HF field, used to localize defects in platelike structures. Finally, it was shown that such method could also be used to characterize a defect in a reverberant structure, in particular, it has been drawn that the obtained images intensity is related to the defect cross-section