Neste trabalho se estuda a aplicação de um método de Ensaio Não Destrutivo, baseado no Ruído Magnético de Barkhausen (RMB), na medição de falhas superficiais em aços. O RMB é gerado por abruptas mudanças na magnetização de materiais quando submetidos a campos magnéticos variáveis. Essas mudanças são afetadas pela microestrutura e a presença e distribuição de tensões elásticas (compressão e tração). Inicialmente apresenta-se um estudo de medições de tensões produzidas por flexão, e perfis de dureza, via RMB. Analisa-se a influência de parâmetros de medição e analise dos sinais, na qualidade do diagnostico. Analisou-se a sensibilidade dos sinais de RMB na medição de tensão a parâmetros tais como direção de laminação da chapa, intensidade e frequência de campo magnético de excitação. Nos estudos da aplicação do RMB em medições de dureza, se usaram amostras de ensaio Jominy, com variação contínua de dureza. Utilizou-se dois tipos de materiais e foram feitas medidas de dureza HRC, RMB e análise metalográfica. O comportamento de diferentes parâmetros dos sinais de RMB se correlacionou com as medições de Dureza e as micrografias obtidas. As amplitudes do RMB mostraram ser inversamente proporcionais aos níveis de dureza. Também se apresenta uma nova tecnologia para inspeção de superfícies, baseado no conceito do Barkhausen Contínuo. São apresentadas análises de parâmetros de medição e de configuração de sonda, na inspeção sob três situações: presença de defeitos volumétricos, deformação plástica, e tensões mecânicas aplicadas. Estudou-se a influência de parâmetros como, amplitude do campo aplicado, velocidade de varredura, posicionamento e características do sensor, no nível de detecção do dano. Métodos de processamento de sinais específicos foram desenvolvidos. Os resultados mostraram, que para cada um dos casos estudados, é possível detectar a posição e nível do dano produzido. Essa nova tecnologia aumenta o espectro de soluções de Ensaios Não Destrutivos para problemas não contemplados pelos métodos existentes. / This work studies the application of a non-destructive testing method, based on the Magnetic Barkhausen Noise (MBN). MBN is generated by abrupt changes in magnetization of ferromagnetic materials subjected to variable magnetic fields. These changes are affected by the presence and distribution of elastic stresses (compression and traction) in the material and by its microstructure. At first, the present study describes MBN measurements of stresses produced by bending and MBN measurements of hardness profiles, in steel samples. The influence of both, measurement parameters and signal analysis, in the quality of fault diagnosis is also analysed. In this context, regarding stress measurements, the MBN signal sensitivity to parameters like surface lamination direction, intensity and frequency of magnetic excitation field is studied. On the other hand, application of MBN to hardness measurements used Jominy essay samples presenting continuous hardness variation. In this case, samples of two different materials were employed and hardness measurements were obtained by HRC, MBN as well as by metallographic analysis techniques. Behaviour of different MBN signal parameters were correlated with obtained hardness measurements and micrography. MBN amplitudes were shown to be inversely proportional to hardness levels. Finally, the work describes a new surface inspection technology, based on the concept of Continuous Barkhausen. In this context, the study analyses probe configuration and measurement parameters, concerning inspection of surface fault from three different origins: volumetric, plastic deformation, applied mechanical stress. The influence of parameters like applied field amplitude, probe velocity, sensor position and characteristics, in detecting damage level was also evaluated. In particular, specific signal processing methods were developed. Results showed that, for each studied case, it is possible to detect damage position and level. This new technology increases the range of NDT essay solutions for problems not yet contemplated by existing methods.

Este trabalho apresenta os avanços no desenvolvimento de um novo método de ensaio não-destrutivo magnético. O método está baseado na técnica do Ruído Magnético de Barkhausen (RMB), particularmente em uma variante denominada Barkhausen Contínuo. O RMB é gerado devido à ação de um campo magnético variável magnetizante que produz mudanças abruptas e irreversíveis na estrutura magnética do material. Essas mudanças são influenciadas pela microestrutura e a distribuição de tensões dentro do mesmo. As medições podem ser usadas para construir uma distribuição bidimensional do RMB ao redor de um ponto fixo, cujo resultado irá refletir o nível de anisotropia magnética, usualmente indicando um eixo de fácil magnetização, parâmetro relevante dado que o comportamento da grande maioria de materiais ferromagnéticos de engenharia é usualmente anisotrópico. As mudanças no eixo de fácil magnetização podem indicar a presença de anomalias mecânicas ou abnormalidades no processo de fabricação e no caso da aplicação de uma tensão externa, podem refletir a magnitude e a direção da mesma. O presente trabalho descreve uma metodologia que faz uso de um campo magnético rotacional para obter sinais RMB relacionados ao angulo de giro, possibilitando a identificação da direção do eixo de fácil magnetização, ultrapassando as capacidades oferecidas pela técnica RMB convencional mediante o fornecimento de informação em tempo real, que permite a obtenção de um conjunto de parâmetros que quantificam a anisotropia magnética de uma amostra. A técnica foi usada para a detecção do eixo de fácil magnetização e o nível de anisotropia magnética em materiais diferentes devida aos efeitos do processo de fabricação. Posteriormente foi demonstrado que a técnica é capaz de monitorar a evolução da tensão uniaxial aplicada, obtendo curvas de calibração, sensíveis ao sentido de aplicação da tensão. Para o caso pouco estudado de amostras submetidas a tensões biaxiais, o uso da técnica do Barkhausen contínuo rotacional fez possível de verificar que as características morfológicas das medições de anisotropia magnética obtidas, guardam relação com a direção das tensões principais. Foi realizada uma avaliação do método aplicado para a medição dinâmica de anisotropia magnética em juntas soldadas, indicando estados de tensão e características microestruturais coerentes com as esperadas. O método tem a possibilidade de ser implementado para medições anisotropia magnética em alta resolução/alta velocidade. / This works presents the current advances on the development of a new method of magnetic non-destructive testing. The method is based on the magnetic Barkhausen noise (MBN), more specifically in one branch known as Continuous Barkhausen. MBN is produced due to the effect of a variable magnetic field, which causes abrupt and irreversible changes to the magnetic structure of the material. These changes are influenced by the microstructure of the material and the stress distributions within. Measurements can be used to construct a bi dimensional MBN distribution around a fixed point, which in turn will be a reflect of its magnetic anisotropy level, usually characterized by an easy axis of magnetization, an important parameter given that more often than not, the behavior of most engineering ferromagnetic materials is anisotropic. Variations of the easy axis could be the indication of mechanical anomalies or abnormalities that appear as a result of the fabrication process. If there is an external stress applied to the sample, it can provide information about its magnitude and direction. The present work describes a methodology which uses a precise rotating magnetic field in order to obtain MBN signals related to a given magnetization angle, making possible the finding of the easy axis, exceeding the limits of conventional MBN measurements by providing real time data which in turn will allow to infer a set of parameters that quantify the magnetic anisotropy of the sample. The proposed technique was successfully used to find both the easy axis and a quantitative level of magnetic anisotropy between different materials, consequence of the fabrication process. Subsequently, it was shown that the technique was able to perform a monitoring of the evolution of both uniaxial and biaxial applied stress, obtaining linear relationships (uniaxial case), sensitive to the direction of loading. In not so much studied case of biaxial loading, the use of the continuous rotational Barkhausen method made possible to observe that the morphologic characteristics of the magnetic anisotropy measurements bear a close resemblance to the direction of the principal stress field. An evaluation of the technique as a tool for the dynamic measurement of magnetic anisotropy on welded joints, indicating stress states and microstructural features coherent with the ones expected in this scenario. The method has the possibility of being implemented as a technique for high speed/high resolution measurements of magnetic anisotropy.

A análise dinâmica experimental tem sido amplamente pesquisada como uma ferramenta de avaliação de integridade de estruturas de concreto armado. Existem técnicas de identificação de danos baseadas em propriedades modais como frequências de ressonâncias, deformadas modais, curvaturas modais e amortecimento. Há também técnicas baseadas na não linearidade da resposta dinâmica, que apesar do grande potencial na detecção de danos, têm sido pouco exploradas nos últimos anos. Este trabalho tem por objetivo avaliar a integridade estrutural de vigas de concreto armado através do comportamento da resposta dinâmica. Foram realizados ensaios dinâmicos em duas vigas de concreto armado com 3,5 m de comprimento, 25 cm de largura, 35 cm de altura e idênticas taxas de armaduras, mas configuradas com barras de aço de diferentes diâmetros, 2 &#981 16 mm e 8 &#981 8 mm, respectivamente. Tais vigas, inicialmente íntegras, foram submetidas a ciclos de carregamento e descarregamento com intensidades crescentes até atingir a ruptura do elemento. Após cada ciclo, as propriedades dinâmicas foram avaliadas experimentalmente, com o emprego de técnicas de excitação por sinais do tipo aleatório e tipo transiente, respectivamente, visando determinar parâmetros que indiquem a deterioração gradativa do elemento. Nesses ensaios dinâmicos aplicaram-se diferentes amplitudes da força de excitação. Verificou-se que o aumento da amplitude da força dinâmica de excitação provocou reduções nos valores das frequências de ressonância de 1,1% e 2,4%, associadas, respectivamente, às excitações aleatórias e transientes; e um comportamento não linear dos índices de amortecimento, associados às excitações aleatórias, mantendo um crescimento linear com as excitações transientes. Constatou-se, ainda, que os valores das frequências de ressonância decrescem com a redução de rigidez mecânica, diminuída com o aumento do nível de fissuração induzido nos modelos. Já os valores dos índices de amortecimento, após cada ciclo, se comportaram de forma não linear e assumiram diferentes valores, conforme a técnica de excitação empregada. Acredita-se que esta não linearidade está relacionada aos danos provocados no elemento pela solicitação estrutural e, por consequência, ao processo de como a dissipação de energia é empregada no processo de instauração, configuração e propagação das fissuras nos elementos de concreto armado. / The experimental dynamic analysis has been widely investigated as a tool to assess integrity of reinforced concrete structures. State-of-the-art modal-based techniques for structural damage analysis use resonance frequencies, modal deformed, curvature and modal damping analysis. There are also techniques based on nonlinear dynamic response that despite the large potential for damage detection, have not been considered in recent years. This work aims to evaluate the structural integrity of reinforced concrete beams through the dynamic response behavior. Dynamic tests were performed on two reinforced concrete beams with 3.5 meters of length, 250 mm of width, 350 mm of height and identical reinforcement rates, but different steel bars diameters, 2 &#981 16 mm e 8 &#981 8 mm, respectively. Beams were initially intact and were subjected to loading and unloading cycles with increasing intensity until the rupture of the concrete beam. After each cycle, the dynamic properties were evaluated experimentally with random and transient excitation signals to determine parameters that indicate gradual deterioration of the beam. Different amplitudes of the excitation force were applied during dynamic testing of concrete beams. These results indicated that an increase in amplitude of dynamic excitation force caused reductions in frequency resonances by 1.1% and 2.4%, associated with the random and transient excitations, respectively. Furthermore, a non-linear behavior of the damping ratios related to random excitations was observed while a linear relationship with transient excitation was found. Moreover, it was found that the resonance frequency decreased with the cracking-related reduction of beam stiffness, caused by increasing level of loading. Additionally, the values of the damping ratios after each cycle behaved non-linearly assuming different values according to the used excitation technique. It is believed that this non-linearity can be related to the loading-related structural damage of the reinforced concrete beam. Therefore, the energy dissipation related to cracking initiation, configuration and propagation in reinforced concrete elements played an important role in the damping ratios of concrete beams.

Este trabalho apresenta um método para o reconhecimento e a detecção automática dos diferentes valores ou graus de deformação plástica em Ensaios Não Destrutivos empregando o Ruído Magnético de Barkhausen. O método é baseado no uso de uma Rede Neural Probabilística que permite o diagnóstico automático dos diferentes valores de deformação plástica, conteúdo de carbono, estas medidas são procedentes das medições das amostras de placas de aço AISI 1006, 1050 e 1070, esta base de dados foi feita pelo grupo de pesquisadores do Laboratório de Dinâmica e Instrumentação LADIN da Escola Politécnica da USP, departamento da Mecânica. Os excelentes resultados da rede neural probabilística de detectar automaticamente os valores de deformação mostram a efetividade do desempenho da rede neural probabilística que tem um desempenho superior aos métodos não destrutivos tradicionais e que realmente esta nova tecnologia é uma excelente solução para o diagnóstico. / This work presents a method for automatic detection and recognition of different levels or degrees of plastic deformation in Non-Destructive Testing using the Magnetic Barkhausen Noise. The method is based on using a Probabilistic Neural Network that allows the automatic diagnosis of the different values of plastic deformation and carbon content. The measurements corresponds to samples of steel plates AISI 1006, 1050 and 1070, this database was made by the group of researchers from the Laboratory of Dynamics and Instrumentation LADIN the Polytechnic School of USP, Department of Mechanical Engineering. The results show the effectiveness of the probabilistic neural network to automatically detect plastic deformation levels as well as carbon content level. This method has a superior performance in comparison to traditional nondestructive methods.

Dans cette thèse, nous présentons de nouvelles méthodes de traitement d’images pourextraire ou rehausser les éléments fins d’une image. Pour ces opérateurs, issus de la morphologie mathématique,l’accent a été mis principalement sur la précision de détection et sur le temps de calcul,qui doivent être optimisés pour pouvoir répondre aux contraintes de temps imposées par différentesapplications industrielles. La première partie de ce mémoire présente ces méthodes, organisées enfonction de la tortuosité des objets à détecter. Nous commençons par proposer un algorithme rapidepour le calcul des ouvertures 1-D afin d’extraire des structures rectilignes des images. Puis, nous étudionsune nouvelle classe d’opérateurs rapides avec les ouvertures parcimonieuses par chemins, permettantd’analyser des structures ayant une tortuosité modérée. Enfin, nous proposons de nouveauxéléments structurants adaptatifs et des filtres connexes construits avec des attributs géodésiques etgéométriques pour extraire des structures filiformes ayant une tortuosité quelconque.Dans un second temps, nous avons développé une méthode d’analyse statistique en introduisantune nouvelle pénalisation adaptative. L’objectif consiste à créer un modèle prédictif précis, quiminimise en même temps une fonction de coût, indépendante des données. Lorsque cette fonctionde coût est liée au temps de calcul de chaque descripteur, il est alors possible de créer un modèleparcimonieux précis et qui minimise les temps de calcul. Cette méthode est une généralisation desrégressions linéaires et logistiques Ridge, Forward stagewise, Lar, ou Lasso.Les algorithmes développés dans cette thèse ont été utilisés pour trois applications industrielles,très différentes les unes des autres, mais toutes faisant intervenir une approche multidisciplinaire : letraitement d’images et l’analyse statistique. L’association de ces deux disciplines permet d’améliorerla généricité des stratégies proposées puisque les opérateurs de traitement d’images alliés à un apprentissagesupervisé ou non supervisé, permettent d’adapter le traitement à chaque application.Mots clés : Traitement d’images, morphologie mathématique, analyse statistique, caractérisation deformes, contrôles non destructifs, ouvertures parcimonieuses par chemins, region growing structuringelements, amincissements par attributs géodésiques et topologiques, adaptive coefficient shrinkage. / This PhD is dedicated to new image processing methods to extract or enhance thinobjects from an image. These methods stem from mathematical morphology, and they mainly focuson the accuracy of the detection and on the computation time. This second constraint is imposed bythe fact that we are dealing with high-throughput applications. The first part of this thesis presentsthese methods, organized according to the tortuosity of the objects to detect. We first propose afast algorithm for the computation of 1-D openings, used to extract thin and straight structures in theimages. Then, we study a new class of fast operators, parsimonious path openings, which can extractthin structures with moderate tortuosities. Finally, we propose new adaptive structuring elementsand new thinnings with geodesic and geometric attributes to filter out the noise and to enhance thinstructures of any tortuosity.Besides, we have developed a machine learning method by introducing a new adaptive penalization.We aim at creating a predictive model that minimizes a cost function (independent of the data)while preserving a good accuracy. When this cost function is linked to the computation time of eachfeature, the resulting models will optimize the timings, while preserving a good accuracy. This methodis a generalization of linear and logistic regressions with Ridge, Forward stagewise, Lar or Lassopenalization.The algorithms developed in this thesis have been used for three industrial applications. While theirobjectives are very different, the framework is the same (non-destructive testing) and they all involvea multidisciplinary approach (images processing and statistical analysis). The combination of thesetwo fields yields a higher flexibility in comparison with classical methods. Generic strategies are used,since image processing operators are associated to statistical learning (supervised or unsupervised)to make a specific treatment for each application.Keywords: Image processing, mathematical morphology, statistical analysis, pattern recognition,non destructive testing, parsimonious path openings, region growing structuring elements, geodesicand topologic attributes thinnings, adaptive coefficient shrinkage.

Ces travaux traitent de l'utilisation de la thermographie infrarouge dans le cadre du contrôle non destructif des ouvrages de génie civil.Une première partie, traite de l’étude des paramètres influençant la mesure in situ, de la capacité de la technique à détecter la variation de propriétés intrinsèques au matériau, et de la détection de délaminations. Les résultats présentés sont issus de mesures expérimentales appuyées par une approche numérique aux éléments finis. Dans un premier temps, une étude sur la capacité de la thermographie infrarouge à détecter des variations de porosité ou de teneur en eau a été réalisée. Dans un second temps, des travaux sont menés sur la détermination des seuils de détection des délaminations en fonction des conditions d’exposition. Ils ont montré un seuil de détection correspondant à un rapport de 2, entre l’extension latérale du défaut et sa profondeur, pour un ensoleillement direct, et à un rapport de 3,3 pour un ouvrage soumis uniquement aux variations de température de l’air. La réalisation d’un suivi temporel combiné à l’étude de l’évolution des gradients temporels de température permet d’améliorer ces seuils de détection. Enfin, une étude originale sur le pontage présent au niveau des délaminations, a montré la prédominance de l’influence de celui‐ci sur la profondeur des délaminations.Une deuxième partie porte sur les travaux réalisés dans le cadre du projet ANR‐SENSO. Ils traitent de la combinaison des résultats issus de différentes techniques de CND dans le cadre plus large de l'amélioration des diagnostics pour la gestion du patrimoine. / This thesis focuses on the use of infrared thermography as a tool for non destructive testing ofbuildings. Mainly, the application is on civil engineering projects.The first part includes identifying the parameters that can affect this in situ technique. Thisparticularly deals with the infrared thermography capacity to detect intrinsic property variations, anddelamination detection. Combination of experiments on concrete slabs and numerical simulationsare used. In a first step, a study on the capacity of thermography to detect porosity and watercontent variation was conducted. In a second step a study on the thresholds for detectingdelaminations based on exposure conditions is carried out. As an outcome, the threshold that hasbeen detected corresponds to a ratio of 2 between the lateral extension of the defect and its depthto direct sunlight; while a ratio of 3,3 if it is exposed to air temperature variations. This studysuggests that a time monitoring combined with the study of the evolution of temporal temperaturegradients can improve the detection limits. Finally, an original study showed the predominance ofthe influence of bridging on the depth of delamination.The second part tackles the works carried out during the ANR project SENSO. Results fromdifferent non destructive tools were coupled for the purpose of improving diagnosis in the assetmanagement.

Les budgets alloués aux réparations des ouvrages et du patrimoine bâti ont atteint un niveau important. Une démarche scientifique est donc réfléchie pour réduire ces budgets par la mise en place d’outils visant à optimiser et fiabiliser le diagnostic structural des ouvrages. Les méthodes de contrôle non destructif (CND) constituent l’une des voies adaptées. Ces techniques reposent sur des principes physiques bien connus et les sociétés de service en proposent aujourd’hui un emploi courant, mais de nombreux verrous subsistent. Les deux besoins majeurs des gestionnaires d’ouvrages sont celui de l’optimisation de la stratégie de reconnaissance (où mesurer ? en combien de points ? avec quelle(s) techniques(s) et quelle précision ?) et celui de la quantification des propriétés mécaniques des matériaux ou des indicateurs de durabilité telles que la résistance à la compression, l’épaisseur carbonatée, le taux d’humidité. La question est comment déduire ces propriétés et ces indicateurs des mesures faites ? Et quelles sont la précision et la fiabilité de l’évaluation ?Cette thèse s’inscrit dans le cadre de deux projets nationaux de recherche : le projet ACDC-C2D2 et le projet ANR EvaDéOS. L’objectif principal est d’analyser la variabilité issue du CND pour ensuite remonter à la variabilité spatiale des bétons en conditions réelles. Les techniques de CND considérées sont choisies parmi les plus complémentaires : radar, résistivité électrique, ultrasons et rebond (scléromètre). Les résultats sont obtenus à partir d’une large campagne expérimentale effectuée sur des dalles d’un site test et sur deux ouvrages. L’analyse de la variabilité des CND a permis d’évaluer le nombre minimal de mesures nécessaire pour un niveau de confiance souhaité. D’autre part, la corrélation spatiale des données a été modélisée par l’analyse variographique. Les résultats montrent que, dans certain cas, les mesures de CND ne sont pas spatialement indépendantes. Les longueurs de corrélation identifiées dépendent de la propriété mesurée ainsi que du béton de l’ouvrage ausculté. La connaissance de ces longueurs de corrélation est un résultat nouveau qui permettra d’une part de mieux estimer la variabilité spatiale des bétons et d’autre part d’alimenter de manière plus réaliste les calculs fiabilistes des ouvrages. Elle permet également d’identifier un pas d’échantillonnage optimal sur ouvrage dans le cadre du suivi temporel ou pour effectuer des analyses complémentaires (ex. carottage, CND complémentaire ou plus fiable) et de représenter au mieux la cartographie spatiale des propriétés du béton.Dans le cadre du projet de recherche ANR EvaDéOS, les effets de la carbonatation et des gradients de teneur en eau (gradient d’humidité) sur les techniques CND ont été étudiés. Ce travail a pour objectifs d’étudier la sensibilité des techniques de CND à évaluer ces deux indicateurs de durabilité ainsi que leur impact sur la variabilité des mesures de CND. En laboratoire, des campagnes expérimentales ont été réalisées sur corps d’épreuve ayant différentes profondeurs de carbonatation ou des gradients d’humidité. L’effet de la carbonatation a été quantifié pour certains observables : résistivité électrique, vitesse ultrasonore et rebond. En ce qui concerne la variabilité des mesures de CND, l’effet de la carbonatation est seulement notable dans le cas du béton saturé, en particulier pour la variabilité locale de la résistivité électrique et du rebond. Cet effet reste faible par rapport à l’effet du degré de saturation. Les premiers résultats montrent également que les mesures de la résistivité électrique permettraient de suivre des gradients d’humidité dans le béton. / The budgets assigned to the repair of structures and built heritage have reached an alarming level. A scientific approach is needed to reduce these budgets by implementing tools for a more reliable and optimal assessment of existing structures. Non-destructive testing (NDT) techniques constitute one of approaches adapted to real conditions. These techniques are based on well-known physical principles. Many companies offer their services in NDT domain today but many challenges remain. The two particular needs of structure managers are the optimization of the assessment strategy (where to measure? how many testing points? what technique(s) and what precision?) and the quantification of mechanical properties of materials or durability indicators such as the compressive strength, the carbonation depth, the moisture content. The questions are how to estimate these properties from measurements performed, and what are the accuracy and reliability of the evaluation?This thesis is part of two French research projects: ACDC-C2D2 and ANR EVaDéOS. The main objective is to analyze the variability of non-destructive testing (NDT) measurements for assessing the spatial variability of concrete in real conditions. NDT techniques considered are chosen as being complementary: radar, electrical resistivity, ultrasonic, rebound hammer. The results are obtained from a wide campaign of measurements, which was performed on concrete slabs of a testing site and on two existing structures. The analysis of the NDT variability makes it possible to assess the necessary minimum number of measurements for a desired level of confidence. Furthermore, the spatial correlation of the data was modeled using the variogram analysis. In some cases, the results show that NDT measurements are not spatially independent. The correlation lengths identified depend on the measured property and the concrete of the structure inspected. They are a new result, which will provide on one hand a better evaluation of spatial variability of concrete and on the other hand a more realistic input of reliability calculations of structures. The correlation length allows also the identification of an optimal sampling distance on existing structure within the monitoring time or the implementation of additional analyses (eg. core, complementary or more reliable NDT) and a better representation of the spatial mapping of concrete properties.Within the framework of the ANR EvaDéOS research project, the effects of carbonation and of moisture gradients on NDT measurements were studied. This work aims to study the sensitivity of NDT techniques for assessing these two durability indicators and their impact on the variability of NDT measurements. In laboratory, the experimental surveys were carried out on testing specimens having different depths of carbonation or moisture gradients. The effect of carbonation was quantified for several parameters: electrical resistivity, ultrasonic pulse velocity and rebound hammer. With respect to the variability of NDT measurements, the effect of carbonation is only significant in the case of saturated concrete, in particular for the local variability of electrical resistivity and rebound hammer. This effect is weak in comparison with the effect of saturation degree. The first results show also that the measurements of electrical resistivity would follow moisture gradients in concrete.

Les travaux que nous avons menés concernent la modélisation de l’interaction laser-matière couplée à de la thermographie infrarouge, pour la détection de défauts débouchants et sous-jacents dans des matériaux métalliques. A terme, ce procédé de thermographie se veut être une alternative possible à la magnétoscopie et au ressuage dans le domaine des contrôles non destructifs. Ces travaux se sont déroulés en trois phases. Dans un premier temps, nous nous sommes intéressés à la caractérisation des propriétés optiques et thermophysiques des matériaux, pour alimenter le modèle de simulation numérique mais également pour les besoins des mesures de validation du modèle numérique. La deuxième partie de l’étude a permis la mise en place d’un modèle de simulation numérique représentatif de la réalité avec une approche en deux étapes : une première consistant à calculer des champs de températures éléments finis et une seconde à modéliser la caméra de thermographie infrarouge représentatif de celle utilisée dans le projet. Des solutions innovantes ont été utilisées pour obtenir un modèle qui intègre tous les paramètres, avec des temps de calculs faibles. Ce modèle a été ensuite validé par des mesures comparatives des champs de températures numériques et expérimentaux. Enfin, nous nous sommes appuyés sur ce modèle pour rechercher les paramètres optimaux de ce procédé, grâce à la méthode des plans d’expériences numériques. / The aim of this work is the detection of open and subjacent defects in metallic materials using laser-material interaction coupled with infrared thermography. This process is a possible alternative for magnetic particles testing and dye penetrant testing in the field of non-destructive testing. This work is divided into three main parties. At first, we have been interested in the characterization of optical and thermophysical properties of materials we used, in order to have good boundary conditions and also for the needs of temperatures fields measurements for validation. The second part concern the development of a numerical simulation model with two step approach: the first involves modelling temperature field with finite element method and the second details the infrared camera modelling. Innovative solutions were used to obtain model which integrates all parameters, with low time calculation. After validated temperature field, this model allows us to look for the process optimal parameters through numerical experimental designs.

This thesis work focuses mainly on the application of non-destructive testing (NDT) methods on wood-based panels (WBP) in order to estimate the bending properties. To prove the accuracy and applicability of these methods on WBP, their results are correlated with results from a standardized static bending test. The behavior in different climate conditions and the application on panels of larger sizes is also questioned to provide an indication about strong points and boundaries of NDT methods applied on WBP.The bending properties are of major importance, especially for materials suited to bear loads. Bending stiffness, represented by the modulus of elasticity (MOE), is an expression of the deflection rate of a material under load. The bending strength, represented by the modulus of rupture (MOR), is an expression of the maximum load withstood by a material before rupture.Before testing, the material is acclimatized in three climate conditions: dry (20°C, 35% RH), standard (20°C, 65% RH) and wet (20°C, 85% RH), to understand the bending properties variation and how the NDT methods are affected by the variation in moisture content.The materials used are seven types of WBP, in particular four types of particleboards (PB), one type of high-density fiberboard (HDF), one type of dual density PB (with high and low density areas along the production direction) and one type of light-weight panel (Board-on-stiles, a composite panel of HDF, PB and paper honeycomb).To test the bending properties the following NDT methods are considered: transversal resonance vibration and longitudinal resonance vibration with the use of the BING system and the time-of-flight with the use of Fakopp Ultrasonic Timer and Silvatest Trio. The resonance vibration methods, transversal and longitudinal, are based on the relation between resonance vibration properties and bending properties of a material. The relation with bending properties also exists for the stress wave velocity (SWV) through a material, calculated with the time-of-flight method. The dynamic MOE resulting from these tests is then correlated with the static MOE and MOR from the static bending test.The NDT methods resulted to be reliable on WBP, with generally high levels of correlation between dynamic MOE and static MOE and MoR. The highest correlation value for MoE is with the transversal resonance vibration while the highest for MOR is with the longitudinal resonance vibration. The results of the dynamic MOE for all the NDT methods are higher than the static MOE, as confirmed also in the literature; the average ratio between the dynamic and the static MOE is, for example, up to 1,6 for WBP in standard climate condition, tested with Fakopp U.T.. These results are extremely higher than values suggested by previous studies. Moreover, the ratio increases with increasing relative humidity of the climate condition. The results from the tests on larger sizes suggest a possible application in this field. The time-of-flight method is suitable for in-plane uniform materials, like the PB and HDF, while the transversal resonance methods give also a good representation of the properties of the dual density PB and the light-weight panel.

Les transducteurs ultrasonores font l'objet de nombreux développements en contrôle non-destructif (CND) industriel. Utilisé ponctuellement et périodiquement, le CND ultrasonore permet d'établir des diagnostics sur la santé des matériaux. La caractérisation ultrasonore en temps réel constitue un outil de surveillance de l'évolution des propriétés physiques lors de la fabrication des matériaux composites. Dans ce contexte, des études sont menées au LOMC pour optimiser le procédé de fabrication des matériaux composites par RTM (Resin Transfer Molding) afin d’améliorer la qualité du produit. Ce travail de thèse consiste à développer des méthodes ultrasonores pour le suivi des propriétés viscoélastiques d’un composite pendant la phase de production. Les propriétés viscoélastiques sont étudiées à l’aide de modèles théoriques, de simulations numériques et de résultats expérimentaux. Des études de calibration ont été menées afin d’étudier les facteurs d’influence sur le suivi de propriétés ultrasonores lors de la mise en oeuvre d’un procédé RTM. Le suivi des paramètres viscoélastiques de résines époxy est effectué dans un premier temps à basse température au cours d'une polymérisation isotherme et d’une post-cuisson. Ensuite, une approche basée sur la méthode de caractérisation en émission/transmission a été développée afin d’étudier le comportement à haute température. La modélisation de la réponse électroacoustique par série de Debye (DSM) a été effectuée en se basant sur des approches analytiques. L’utilisation des transducteurs multiéléments permet la localisation et le dimensionnement de défauts lors du déplacement de fibres de carbone dans une résine liquide, entre des moules. / The developments based on ultrasonic transducers are nowadays numerous in the industrial non-destructive testing (NDT). Used punctually and periodically, the ultrasonic NDT is used for health diagnostics of materials. Ultrasonic characterization in real time allows a physical properties monitoring during the manufacturing of composite materials. In this context, studies are conducted in LOMC in view to optimize the manufacturing process of composite materials using RTM (Resin Transfer Molding) in order to improve the product quality. This work consists to develop ultrasonic methods for the monitoring of viscoelastic properties during the production phase of composites. The viscoelastic properties are studied using theoretical models, numerical simulations and experimental measurements. Calibration studies were carried out to study the influencing factors on the monitoring of ultrasonic properties during the RTM process. The monitoring of viscoelastic parameters of epoxy resins is performed in a first time at low temperature during an isothermal polymerization and a post-curing. Then, an approach based on the transmission mode characterization was developed to study high-temperature behavior. Based on analytical approaches, the electroacoustic response was simulated by Debye series method (DSM). The use of phased array transducers was investigated for the location and sizing of defects during the movement of the carbon fiber in a liquid resin between the molds.