The Lamb wave based, non-contact damage detection techniques are developed using the Modified Time Reversal (MTR) method and the model based inverse problem approach. In the first part of this work, the Lamb wave-based MTR method along with the non-contacting sensors is used for structural damage detection. The use of non-contact measurements for MTR method is validated through experimental results and finite element simulations. A novel technique in frequency-time domain is developed to detect linear damages using the MTR method. The technique is highly suitable for the detection of damages in large metallic structures, even when the damage is superficial, and the severity is low. In this technique, no baseline data are used, and all the wave motion measurements are made remotely using a laser vibrometer. Additionally, this novel MTR based technique is not affected due to changes in the material properties of a structure, environmental conditions, or structural loading conditions. Further, the MTR method is improved for two-dimensional damage imaging. The damage imaging technique is successfully tested through experimental results and finite element simulations. In the second part of this work, an inverse problem approach is developed for the detection and estimation of major damage types experienced in adhesive joints. The inverse problem solution is obtained through an optimization algorithm wherein the objective function is formulated using the Lamb wave propagation data. The technique is successfully used for the detection/estimation of cohesive damages, micro-voids, debonds, and weak bonds. Further, the inverse problem solution is separately obtained through a fully connected artificial neural network. The neural network is trained using the Lamb wave propagation data generated from Wavelet Spectral Finite Element (WSFE) model which is computationally much faster than a conventional finite element model. This inverse problem approach technique requires a single point measurement for the inspection of the entire width of the adhesive joint. The proposed technique can be used as an automated quality assurance tool during the manufacturing process, and as an inspection tool during the operational life of adhesively bonded structures.

Experimentation exploring the movement of voids within carbon fiber reinforced plastics was performed using fluorescent dye infused into the laminates observed through a transparent mold under ultraviolet light. In situ photography was used as an inspection method for void content during Resin Transfer Molding for these laminates. This in situ inspection method for determining the void content of composite laminates was compared to more common ex-situ quality inspection methods i.e. ultrasonic inspection and cross-section microscopy. Results for localized and total void count in each of these methods were directly compared to test samples and linear correlations between the three test methods were sought. Test coupons were then cut from these laminates and were used to calculate the interlaminar shear strength at certain locations throughout the laminates. Although this research did not adequately observe correlations between results obtained from ultrasonic C-scans, cross-sectional microscopy and in situ photography of the surface, it was seen that the fluid dynamics of the thermosetting epoxy used in this experimentation correlated to results obtained from previous experimentation performed by students at Brigham Young University using vegetable oil as a substitute for resin.

Die Durchstrahlungsprüfung ist in der klassischen Materialprüfung aus guten Gründen seit Jahrzehnten etabliert, bietet sie doch als einziges zerstörungsfreies Verfahren die Möglichkeit einer direkten Bildgebung des Innern von Schweißnähten, Guss- und Werkstücken. In der zerstörungsfreien Prüfung im Bauwesen (ZfPBau) wird das Verfahren bislang nicht systematisch angewandt, obwohl sich dank Weiterentwicklungen insbesondere im Bereich der digitalen, mobilen Radiographie viele praktische Einsatzmöglichkeiten anbieten. Qualitätssicherung im Neubau, Schadensbewertung im Bestand oder die noninvasive Untersuchung von Spannbeton und Denkmalschutzbauten – die Palette ist breit gefächert. Mit der Radiographie ist eine eindeutige Abbildung, Vermessung und Identifikation von Einbauteilen, Bewehrungs- und Spannstahl möglich. Die zielführende Untersuchung von Rissen im Beton oder Restquerschnitten korrosiver Bewehrung ist ebenfalls denkbar und kann Stoff zukünftiger Forschungsarbeiten sein. Der Beitrag soll anhand von aktuellsten Praxisbeispielen das künftige Potential und auch die Anwendungsgrenzen des Verfahrens in der Praxis der ZfPBau demonstrieren.

<p dir="ltr">Unmanned Aerial Systems (UAS) have the potential to drastically change how civil infrastructure is inspected, monitored, and managed. This innovative technology can ensure the inspector’s safety, provide additional inspection information, and reduce costs. However, a challenge arose as this industry expanded: a lack of standardized guidelines or minimum performance requirements to perform these operations. With no standard tests to verify UAS’ ability to conduct inspections and unknown detection capabilities, agencies are left to rely upon consultants’ or vendors’ promotional material and claims when considering UAS deployment. The following work proposes a series of performance-based assessments and procedural documentation to establish minimum standards for using UAS in bridge inspection applications. Through this work, the following performance-based tests have been developed: (1) a controlled environment simulating bridge geometries to assess the overall capability of a UAS used for bridge inspection [evaluation chamber], (2) an assessment of UAS performance under multiple environmental temperatures [environmental temperature chamber], (3) a UAS performance assessment under varying wind speeds [wind chamber], (4) a consolidated checklist compiling Federal Aviation Administration guidelines and best practices [flight checklist], (5) a field assessment of UAS under conditions analogous to on-site bridge inspection [practical test]. For infrastructure owners, embracing these performance-based assessments will help ensure that UAS meets a minimum level of performance and allow owners to verify and distinguish between various UAS used for bridge inspection. This work also discusses positive feedback from beta testing provided by industry and infrastructure owner representatives, showcasing the effectiveness of providing an authentic assessment of UAS bridge inspection capabilities. Future work encourages the wide implementation of this assessment program and encourages owners to refrain from using untested technology in the inspection of their infrastructure.</p>

This thesis deals with building survey of bridge register number 43-011 located near Česká. The part of thesis is literary reaserch dealing with system of management and cotrol of road bridges, precast bridge contructions made with DS-C type girgers and about general diagnostical methods. The practical section contains of in situ diagnostical survey and bridge inspection, laboratory evaluation and comparision, load bearing capacity calculation and suggestion of potencional technical precautions.

The aim of this thesis is to evaluate the real condition of reinforced concrete beam bridge located in Brno Jundrov. In order to evaluate this condition, there was made the main bridge inspection. Subsequently, a number of diagnostic methods were used, such as hardness tests, concrete stress strenght, ultrasonic pulse method, including their evaluation. In terms of the main inspection, the condition of construction of the bridge was evaluated as V - bad. We found out that the concrete from which the bridge is built of is in very good condition. The problem, however, is the condition of the reinforcement located on the bridge. Based on its condition there must be expected lifespan within the next 5-10 years.

Le contexte de ce travail concerne le process d'Infusion de Résine Liquide (LRI) développé dans le cadre du projet « FUSelage COMPosite » par DAHER SOCATA. Ce process de fabrication permet de réaliser des pièces de formes complexes et des panneaux entiers de fuselage en composites, ce qui réduit considérablement les étapes d'assemblages et donc les temps de production. Les travaux de thèse portent sur l'identification expérimentale du comportement d'un fuselage composite. Ce travail se divise en deux parties qui sont la qualification du contrôle non destructif (CND) par rapport à une taille de défaut critique et l'identification du comportement d'une structure composite orthotrope en présence de ce défaut. Le premier volet consiste à évaluer les techniques de CND basées sur des mesures de champs (acoustiques, thermiques et densimétriques), capables de détecter des défauts internes de types délaminage et porosité au sein de structures composites monolithiques et sandwichs, et fournissant une visualisation des résultats par une cartographie de défauts 2D ou 3D. Le choix de ces méthodes a été motivé par la volonté de DAHER SOCATA d'acquérir de nouvelles compétences en matière de CND. Le deuxième volet consiste à évaluer les paramètres élastiques d'une structure composite orthotrope (structure comprenant une zone saine et une zone localement dégradée) via une procédure d'identification, à partir de mesures de champs, globale et locale par recalage de modèles éléments finis. Cette procédure se décompose en quatre parties avec tout d'abord l'identification des propriétés de la structure saine, ensuite la localisation de la zone dégradée, l'intégration de celle-ci dans le modèle éléments finis, et l'identification des propriétés de cette dernière. / The context of this work concerns the process of Liquid Resin Infusion (LRI) developed under the project "composite fuselage" by DAHER SOCATA. This manufacturing process can produce parts with complex shapes and entire panels of composite fuselage, reducing assembly steps and therefore the production time. The thesis work focused on the experimental identification of the behavior of a composite fuselage. This work is divided into two parts which are the qualification of non destructive testing (NDT) compared to a critical defect size and the identification of the behavior of an orthotropic composite structure with defect. The first part is to evaluate the NDT techniques based on full field measurements (acoustic, thermal and densimetric), capable of detecting internal defects as porosities and delaminations in monolithic and sandwich composite structures, and providing a results visualization by a 2D or 3D defects map. The choice of these methods was motivated by DAHER SOCATA which wants to learn new NDT skills. The second part is to evaluate the elastic parameters of an orthotropic composite structure (structure composed by a virgin zone and a damaged zone) through an identification process from field measurements, by global and local step. This procedure is divided into four parts with two identification steps and a image processing step.

Magnetisch-induktive Techniken finden seit langer Zeit viele Anwendungsfelder in der Medizin, Sicherheitstechnik und der Industrie. Obwohl die technischen Grundlagen seit vielen Jahrzehnten bekannt sind, werden auf Basis detaillierter Analysen spezielle Lösungsansätze verfolgt, die neuartiges Anwendungspotential erschließen sollen. Dazu dienen verbesserte Werkzeuge wie Computersimulationen und analytische Berechnungen sowie neu kombinierte Methoden und Aufbauten aus Leistungselektronik und Signaldetektion. Die Vorteile magnetisch-induktiver Techniken sind dabei u.a., dass sie das Prüfobjekt nicht schädigen, berührungslos arbeiten, robust gegenüber Verschmutzungen und einfach im Aufbau sind. Ein Nachteil dieser Technik ist die unzureichende Auflösung von feinen Strukturen. In der aktuellen Forschung und Entwicklung werden unterschiedliche Spulenanordnungen zur Anwendung in industriellen und medizinischen Fragestellungen untersucht und optimiert. Thema dieser Arbeit ist es, durch Verbesserung der Spuleneigenschaften, neue Anwendungsbereiche für die zerstörungsfreie Materialprüfung zu erschließen. Es wird eine Methode vorgestellt, die Eigenschaften magnetisch-induktiver Tastspulen zu verbessern und so den Aufwand bei der Signalverarbeitung zur Rekonstruktion im Rechner zu reduzieren sowie die Auflösung zu erhöhen. Dazu werden zwei Spulenanordnungen, Transmissions - Tastspulen und Gradiometer - Tastspulen, vergleichend gegenübergestellt und ihre technischen Grenzen aufgezeigt. / Magneto-inductive techniques are found in many fields of application areas so in medicine, security technology and industry. Although the technical basis has been known for many decades, special solutions are pursued on the basis of detailed analysis that should open new application potential. These are enhanced tools such as computer simulations, analytical calculations, new combined methods and structures of power electronics and signal detection. The advantages of magneto-inductive techniques are that they do not damage the test object, are contactless, robust against dirt and simple in construction. A disadvantage of this technique is the insufficient resolution of fine structures. In current research and development different coil assemblies are investigated in industrial and medical applications. The aim of this work is to improve the coil properties by changing geometric constructions and current patterns of the coils, in order to allow a sharper localization of objects in space and to tap new application areas for non-destructive testing. A method to improve the properties of magneto-inductive coils and thus to reduce the effort in signal processing and image reconstruction as well as to increase the resolution is presented. Two different coil assemblies, gradiometer – coils and transmission – coils, are compared and their technical limits shown.

Ce travail de thèse porte sur le développement d’outils de modélisation pour le contrôle non destructif (CND) par courants de Foucault (CF). Il existe actuellement une tendance à la mise en œuvre de capteurs souples qui représentent une solution pertinente pour inspecter des pièces ayant une surface complexe. L’objectif principal de cette thèse est l’élaboration de techniques permettant la modélisation de ce type de capteurs au sein de la méthode des éléments finis (MEF).Lors de la modélisation d’un capteur souple avec la MEF, trois problématiques se manifestent. La première concerne le maillage des milieux fins qui apparaissent dans ce type de configuration (distance capteur-pièce contrôlée, bobine plate, revêtement fin...). Le maillage de ces régions par des éléments simpliciaux peut poser des problèmes numériques (éléments déformés quand un maillage grossier est considéré et grand nombre d’inconnues quand un maillage fin est utilisé). La deuxième problématique concerne le déplacement du capteur. Si les différents sous-domaines géométriques (air, pièce, capteur...) sont convenablement remaillés pour chaque position du capteur, le temps total pourra être pénalisant. La troisième problématique relative à la modélisation d’un capteur souple porte sur l’imposition du courant dans des bobines déformées.Une comparaison de différentes approches nous a conduit à retenir la méthode overlapping, qui permet de considérer simultanément des milieux fins avec maillages non-conformes. Cette méthode permet d’effectuer le recollement de deux surfaces non planes et/ou de géométries différentes. La méthode overlapping a été implantée dans deux formulations duales (magnétique et électrique) en 2D et 3D intégrées dans le code de calcul DOLMEN (C++) du LGEP. La méthode overlapping a été validée pour la prise en compte de plusieurs types de régions minces (air, milieux conducteurs, milieux magnétiques, bobines plates...). La modélisation des capteurs souples nécessite aussi l’implantation d’une technique permettant d’imposer correctement les courants dans un inducteur de forme arbitraire. Une technique a été sélectionnée et programmée, d’abord pour des bobines classiques (volumiques) déformées puis pour des bobines plates flexibles. Afin de valider les développements réalisés, différentes configurations de test ont été traitées et les résultats comparés avec des solutions de référence analytiques ou expérimentales. / The objective of this thesis is the development of modeling tools for eddy current testing (ECT). Currently there is a tendency to use flexible sensors which represent a viable solution for inspecting parts with a complex surface. The main objective of this thesis is the development of techniques for taking into account this kind of sensors within the finite element method (FEM).When modeling a flexible sensor with the FEM, three issues have to be considered. The first one is related to the mesh of thin regions that appear in this kind of configuration (sensor-inspected part distance, thin coating...). The meshing of these regions with simplicial elements can cause numerical problems (distorted elements when a coarse mesh is considered and high number of unknowns when a fine mesh is used). The second issue is related to the displacement of the sensor on the part surface. If the different subdomains (air, part, sensor ...) are properly remeshed for each position of the sensor, the required time can be penalizing. The third issue, related to the modeling of a flexible sensor, is the computation of the current in distorted sensor coils.A comparison of different approaches has led to select the overlapping element method, which allows to simultaneously consider the thin regions with nonconforming meshes. This method allows to perform the connection of two surfaces which can be non-planar and/or have different geometries. The overlapping method has been implemented in two dual formulations (magnetic and electric) in 2D and 3D and integrated in the computation code (C++) DOLMEN of LGEP. The overlapping method has been validated for several kinds of thin regions (air, conductive regions, magnetic regions, flat coils...). The modeling of flexible sensors also requires the establishment of a technique for properly imposing the current in an inductor of arbitrary shape. A technique has been selected and implemented for conventional (volumic) distorted coils but also for flexible flat coils. Different test configurations have been considered in order to validate the developments and the results have been compared with analytical references or experimental solutions.

Este trabalho descreve o desenvolvimento de um algoritmo para avaliar o grau de corrosão em paredes de oleodutos, através de ultrassom. O algoritmo desenvolvido será implementado em um circuito digital, fazendo parte de um sistema que poderá ser embarcado em pigs ultrassônicos para inspeção de dutos à procura de corrosão. O modelo matemático conhecido como filtro casado é usado como base do algoritmo, além de um método de detecção de picos para localização dos sinais de eco de ultrassom, provenientes das reflexões do sinal nas paredes dos dutos. Um dos problemas é a definição do sinal (e do filtro) que será utilizado, mas por meio de sinais sintetizados (signal design) uma grande gama de alternativas foi analisada e apenas algumas foram selecionadas para testes em experimentos. Por último os melhores sinais foram utilizados na inspeção de um corpo de prova feito à partir de um duto corroído, e os resultados são analisados. A detecção da primeira parede do oleoduto apresenta resultados promissores em comparação com a medição tridimensional das mesmas paredes. O sistema foi capaz de reconstruir o perfil da parede interna do duto com elevada verossimilhança, mesmo em regiões severamente corroídas. A detecção da segunda parede apresenta resultados satisfatórios para baixos níveis de corrosão, porém alguns problemas foram encontrados para níveis mais altos de corrosão, prejudicando a medição direta da espessura da parede nestas condições. / This work describes the development of an algorithm to evaluate the degree of corrosion in pipeline walls, using ultrasound. The developed algorithm will be implemented in a dedicated digital circuit that can be embedded in ultrasonic pigs for pipeline corrosion inspection. The algorithm is based on the mathematic model known as matched filter, besides a peak detection method for the location of ultrasound echoes, originated from the signal reflections in the pipeline walls. One problem is the determination of the signal (and filter) that should be used, but using a signal design approach a large number of possibilities could be analyzed and only a few was tested in experiments. Finally, the best signals were used to inspect a test specimen made of a corroded pipeline section, and the results were analyzed. The first wall detection shows promising results when compared to the results of a three-dimensional inspection of the same walls. It was possible to reconstruct the profile of the internal wall with good likelihood, even at badly corroded areas. The second wall detection shows some satisfactory results on low corrosion levels, but show some problems with high corrosion levels, compromising the direct measurement of the wall of the pipeline.