Made available in DSpace on 2014-12-17T14:07:09Z (GMT). No. of bitstreams: 1 AnaPPF_DISSERT.pdf: 3895025 bytes, checksum: 139d5ed551d6922e5b7f6e67a16602fd (MD5) Previous issue date: 2013-09-06 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Polymer matrix composites offer advantages for many applications due their combination of properties, which includes low density, high specific strength and modulus of elasticity and corrosion resistance. However, the application of non-destructive techniques using magnetic sensors for the evaluation these materials is not possible since the materials are non-magnetizable. Ferrites are materials with excellent magnetic properties, chemical stability and corrosion resistance. Due to these properties, these materials are promising for the development of polymer composites with magnetic properties. In this work, glass fiber / epoxy circular plates were produced with 10 wt% of cobalt or barium ferrite particles. The cobalt ferrite was synthesized by the Pechini method. The commercial barium ferrite was subjected to a milling process to study the effect of particle size on the magnetic properties of the material. The characterization of the ferrites was carried out by x-ray diffraction (XRD), field emission gun scanning electron microscopy (FEG-SEM) and vibrating sample magnetometry (VSM). Circular notches of 1, 5 and 10 mm diameter were introduced in the composite plates using a drill bit for the non-destructive evaluation by the technique of magnetic flux leakage (MFL). The results indicated that the magnetic signals measured in plates with barium ferrite without milling and cobalt ferrite showed good correlation with the presence of notches. The milling process for 12 h and 20 h did not contribute to improve the identification of smaller size notches (1 mm). However, the smaller particle size produced smoother magnetic curves, with fewer discontinuities and improved signal-to-noise ratio. In summary, the results suggest that the proposed approach has great potential for the detection of damage in polymer composites structures / Materiais comp?sitos polim?ricos oferecem vantagens para v?rias aplica??es pela combina??o de propriedades como baixa densidade, elevada resist?ncia mec?nica e m?dulo de elasticidade espec?ficos e resist?ncia a corros?o. Entretanto, por n?o serem magnetiz?veis, esses materiais n?o permitem a utiliza??o de t?cnicas de avalia??o n?o destrutivas que utilizem sensores magn?ticos. Ferritas s?o materiais com excelentes propriedades magn?ticas, estabilidade qu?mica e resist?ncia ? corros?o. Devido a essas propriedades esses materiais s?o promissores para o desenvolvimento de comp?sitos de matriz polim?rica com propriedades magn?ticas. Neste trabalho, discos de comp?sitos de fibra de vidro/ep?xi foram produzidos com adi??o de 10% em massa de part?culas de ferrita de cobalto ou de b?rio. A ferrita de cobalto foi sintetizada pelo m?todo Pechini. A ferrita comercial de b?rio foi submetida a um processo de moagem para se estudar o efeito do tamanho de part?cula nas propriedades magn?ticas do material. A caracteriza??o das ferritas foi realizada pelas t?cnicas de difra??o de raio x (DRX), microscopia eletr?nica de varredura (MEV-FEG) e magnetometria de amostra vibrante (MAV). Entalhes circulares com di?metros de 1, 5 e 10 mm foram introduzidos nos discos de comp?sitos com o aux?lio de uma broca para avalia??o n?o-destrutiva por meio da t?cnica de fuga de fluxo magn?tico (MFL). A abordagem apresentada permitiu identificar todos os entalhes introduzidos nos discos. Os resultados indicaram que os sinais magn?ticos medidos nos discos com a ferrita de b?rio sem moagem e de cobalto apresentaram boa correla??o com a presen?a dos entalhes. O processo de moagem por 12 h e 20 h n?o contribuiu para a melhor identifica??o de entalhes de menor dimens?o (1 mm). Entretanto, o menor tamanho de part?cula permitiu produzir curvas magn?ticas mais suaves, com menos descontinuidades e melhor rela??o sinal-ru?do. Em resumo, os resultados sugerem que a abordagem proposta tem grande potencial para a detec??o de falhas em estruturas de materiais comp?sitos polim?ricos

[pt] É notório que a resistência global de uma estrutura composta por várias camadas coladas depende diretamente da qualidade da adesão entre as mesmas. Imperfeições ao longo das interfaces de adesão comprometem significativamente a performance da estrutura. A caracterização não destrutiva destas imperfeições é geralmente tarefa muito difícil. O principal objetivo deste trabalho é apresentar um método analítico-numérico que permite modelar o campo acústico resultante da interação entre ondas ultra-sônicas e interfaces imperfeitas, auxiliando na escolha de parâmetros para o emprego de métodos ultra-sônicos de inspeção. No trabalho, a aproximação quase-estática, proposta por Thompson em meados da década de oitenta,é combinada com o método das perturbações para a modelagem de defeitos localizados ao longo da camada de adesão. O método desenvolvido admite que as camadas sejam feitas de materiais anisotrópicos, e permite a modelagem em altas frequências. Três simulações são apresentadas para exemplificar a aplicação do método. Resultados destas simulações onde feixes ultra-sônicos são incidentes em placas imersas em água revelam frequências e ângulos de incidência para os quais efeitos de espalhamento, que permitem a caracterização de defeitos localizados, são mais significativos. / [en] It is well known that the global strength of multi-layered composite structures strongly depends on the quality of the adhesion between its constituent elements. Imperfections along interfaces of adhesion can strongly compromise structure s performance. The characterization of such defects is a very difficult task. The main goal of this study is the development of an analytic-numerical method to simulate the acoustic field resulting from the interaction between ultrasonic waves and imperfect interfaces, helping in selection of parameters for ultra-sonic inspecting methods. The Quasistatic-approximation (QSA), introduced by Thompson in 1982, is applied together with the perturbation method to allow modelling of interfacial localized aws. A solution algorithm for the problem is developed with the aid of the invariant embedding method. It is applicable to solve wave propagation problems in arbitrarily anisotropic layered plates and it is stable for high frequencies. Three simulations of multi-layered plates immersed in acoustic uid are presented as illustration of the application of the developed method. Results of those simulations indicate the frequencies and angles of incidence where the scattering effects, which allow the characterization of localized defects, are more significant.

Nous proposons une nouvelle procédure de mesure permettant de tracer la courbe de résistivité en fonction de l'écartement électrode de courant-électrode de potentiel relié à la profondeur d'investigation et au gradient de teneur en eau. Les mesures de résistivité au droit des armatures sont réalisées et une procédure d'inversion permettant de remonter au gradient de résistivité est mise en place. Deux types de mesures ont été effectués expérimentalement, sur des dalles en béton armé et non armée. Deux types de gradient sont étudiés : le séchage et l'humidification. La présence de l'armature diminue significativement la résistivité à cause d'un effet de court-circuit. Les mesures montrent l'intérêt de la procédure pour l'étude du gradient de teneur en eau. Pour la partie numérique la simulation a montré que la mesure de résistivité permet effectivement de déterminer le gradient de résistivité et de définir les paramètres électrochimiques de l'acier via le modèle de Butler-Volmer. / We propose a new measurement procedure that allows drawing a resistivity curve as a function of the spacing between current electrode and potential electrode which is linked to the investigation depth and the water content gradient. The resistivity measurements above the rebars are performed and an inversion procedure to assess the resistivity gradient is carried out. For the experimental part two kinds of measurement are performed on concrete slabs (reinforced and unreinforced). Two gradient types are studied: drying and wetting. The presence of the reinforcement significantly decreases the measurement of the resistivity. The measurements show the interest of the proposed procedure for the study of the water content gradient. Two measurement results were considered in numerical analyses. The simulation shows that it is possible to assess the resistivity gradient and the electrochemical parameters of the rebar via the Butler-Volmer model.

Les travaux présentés dans cette thèse s’appliquent à la caractérisation de propriétés mécaniques par la microscopie acoustique. Ils décrivent un capteur focalisé innovant qui autorise à la fois une topographie et une imagerie quantitative d’un matériau élastique. L’innovation consiste en la séparation des différents modes de propagation d’un matériau excité par une sonde focalisée multiélément. La mesure par temps de vol de la vitesse de propagation des modes de surfaces de matériaux élastiques et anisotropes offre une possibilité de quantification du module caractérisant l’élasticité : le module de Young. Le dimensionnement de la sonde multiélément qui est décrit ici est rendu possible grâce au développement d’un modèle de champs acoustiques permettant d’anticiper le champ rayonné par chaque élément. Un deuxième modèle traitant de l’étude temporel des signaux reçus par la sonde focalisée est aussi présenté pour vérifier le comportement discriminant de la sonde des différentes ondes pouvant se propager. La mesure de propriétés mécaniques par la sonde focalisée est appliquée à différents échantillons et propose des résultats cohérents avec une grande sensibilité. La possibilité de réaliser des images de propriétés mécaniques est ainsi démontrée. D’abord adaptée pour des fréquences de l’ordre de la trentaine de mégahertz, cette sonde possède un nombre limité d’éléments pour assurer une simplicité de conception et de fabrication permettant par la suite une miniaturisation du capteur pour atteindre des fréquences proches du gigahertz. / The work presented in this thesis is applied to the characterization of mechanical properties by acoustic microscopy. It describes an innovative focused sensor that enables both topography and quantitative imaging of an elastic material. The innovation consists in the separation of the different propagation modes of a material excited by a focused multielement probe. Measuring the surface mode propagation velocity of elastic and anisotropic materials thanks to their time of flight provides a possibility of quantifying the module characterizing the elasticity: the Young's modulus. The dimensions of the multielement probe are described here and rely on an acoustic field model developed to anticipate the field radiated by each element. A second model studies the temporal behaviour of the focused probe and also verifies the discrimination of the different waves that propagate. The measurement of mechanical properties by the multielement probe is applied to different samples and provides consistent results with high sensitivity. The ability to produce images of mechanical properties is thus demonstrated. First suitable for frequencies near thirty megahertz, this sensor has a limited number of elements to ensure a simplicity of design and manufacture for a subsequent miniaturization of the sensor to achieve frequencies near the gigahertz.

Antes de utilizar as toras de madeira como elemento estrutural é necessário avaliar as propriedades mecânicas desse material tanto por inspeção visual quanto por ensaio mecânico. A técnica de vibração transversal tem se destacado entre os demais métodos de Avaliação Não-Destrutiva para madeira serrada por obter estimativas acuradas do módulo de elasticidade à flexão. Contudo, testes prévios com essa técnica evidenciaram dificuldades de empregá-la na avaliação a rigidez à flexão de toras. O objetivo deste trabalho foi propor um método de ensaio para estimar o módulo de elasticidade na flexão de toras de madeira por meio de vibração transversal. O método proposto foi testado e validado em uma amostra de 40 toras de Eucalyptus sp. Foram obtidas boas correlações entre o módulo de elasticidade estático e o módulo de elasticidade dinâmico obtido pelo ensaio de vibração transversal. / Before using the wood logs as a structural element is necessary to evaluate the mechanical properties of this material by visual inspection and mechanical testing. The transverse vibration technique has stood out among the other methods of Non-Destructive Evaluation for lumber to obtain accurate estimates of the bending modulus of elasticity. However, previous tests showed difficulties with this technique to use it to evaluate the bending stiffness of logs. The aim of this work is to propose a test method to estimate the bending modulus of elasticity of wood logs by means of transverse vibration. The proposed method was tested and validated on a sample of 40 logs of Eucalyptus sp. It was obtained good correlation between the static bending and dynamic modulus of elasticity obtained by transverse vibration test.

Orientador: Antonio Ludovico Beraldo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola / Made available in DSpace on 2018-08-09T06:15:33Z (GMT). No. of bitstreams: 1 Espelho_JeanClaudioChiozzini_M.pdf: 5138907 bytes, checksum: 875754541cac182e91f3c878f2be3883 (MD5) Previous issue date: 2007 / Resumo: O bambu é uma matéria-prima com múltiplas aplicações, principalmente no setor da construção. Seu desenvolvimento e seu desempenho mecânico são obtidos após um curto intervalo de tempo, quando comparado com as árvores. O bambu é um material renovável e encontrado em abundância em regiões tropicais e subtropicais, nas quais é considerado um material de baixo custo. No entanto, a maior parte das espécies de bambu é altamente susceptível ao ataque de fungos e insetos. Basicamente, pode-se aumentar a durabilidade dos colmos de bambu de duas maneiras, representadas por procedimentos culturais (naturais) e pelo tratamento dos colmos com produtos químicos. Dentre os diversos métodos que visam aumentar a durabilidade do bambu destaca-se o ¿Método de Boucherie Modificado¿. Neste trabalho testou-se a eficiência da aplicação do Método de Boucherie Modificado, comparando o aumento na durabilidade das amostras tratadas (taliscas de bambu) com amostras não tratadas ou testemunhas. Para tal, foram avaliados os efeitos de algumas variáveis como: posição da amostra no colmo, tipos de preservativo e sua concentração, duração do tratamento e tempo de exposição das taliscas em dois ambientes (protegido e exposto). Foram realizados ensaios não destrutivos - END (visual, pesagem das amostras e de ultra-som) e destrutivo (flexão estática). Também foram efetuadas análises químicas (concentração dos elementos químicos nas soluções e seu teor nas regiões do colmo) e de rastreabilidade dos elementos químicos por microscopia eletrônica de varredura (MEV). Os resultados obtidos permitiram verificar a falta de uniformidade da distribuição dos elementos químicos ao longo dos constituintes anatômicos do bambu, ocorrendo a deposição dos mesmos basicamente nos vasos. Verificou-se, igualmente, a ineficiência do uso de soluções com baixa concentração, principalmente quando foram combinadas com tratamentos de curta duração. Os ensaios de ultra-som e de flexão estática foram suficientemente sensíveis para detectar a melhor combinação do efeito dos parâmetros avaliados / Abstract: Bamboo is a raw material with several possibilities of applications, mainly for building purposes. Its development and its mechanical performance are obtained after a short interval of growing when compared with trees. Bamboo is renewable raw material and it is available in tropical and subtropical regions, where it is considered as a cheap material. Nevertheless, the most of bamboo species is highly decayed by insects and fungi attacks. Basically the bamboo culm protection can be obtained by means of a two treatment types: natural protection and chemical protection. In this last category one of the most employed is the Boucherie Modified Method. In this work it was evaluated the performance of a Boucherie Modified Method, comparing treated bamboo samples (bamboo splits) with no treated samples (control). It was evaluated the effect of the sample position in the culm, chemical solution type and its concentration, treatment elongation and the exposition period in two environment (protected and no protected). Non destructive evaluation - NDE (visual, weight control and ultrasound) and flexure test were applied to the specimens along the time. Also chemical analysis (chemical element concentration in the solution and its amount in the bamboo regions) and the traceability of these chemical elements by means a scanning electronic microscope (SEM) were employed. Results obtained showed a lack of uniformity of the distribution of the chemical elements across the bamboo anatomical constituents, occurring the salt deposition mainly in the vessel with a greater diameter. Smaller concentration solutions, mainly when they were combined with smaller treatment time, were not effective to protect bamboo against decay. Results obtained by ultrasound and flexure test were sensitive enough to detect the best combination of the effect of the parameters evaluated. / Mestrado / Construções Rurais e Ambiencia / Mestre em Engenharia Engenharia Agrícola

Les travaux présentés dans cette thèse contribuent au développement du contrôle non destructif des conduits de précontrainte extérieure dans les ouvrages d'art. Une sonde capacitive a été développée pour ausculter ces conduits. L'objectif est d'en améliorer le diagnostic.Dans un premier temps, une cellule de mesure en transmission coaxiale a été développée pour caractériser les matériaux présents dans le conduit sur la bande de fréquence 50 MHz - 1 GHz. Le ciment, les produits de la ségrégation du ciment et la cire d'injection ont été étudiés.La deuxième partie du travail exploite ces résultats dans une modélisation directe du problème global. Une étude paramétrique nous a permis de proposer une méthode d'estimation de l'épaisseur de vide à l'intérieur du conduit à partir des signaux délivrés par la sonde, qui a pu être validée sur une maquette de conduit. A partir de ces résultats sont proposées plusieurs améliorations du dispositif visant à l'obtention de signaux plus riches issus des capteurs, afin de pouvoir estimer un plus grand nombre de paramètres. / The work presented in this report contributes to the development of Non Destructive Evaluation of the external post-tensioned ducts in bridges. A capacitive probe has been developed for bridge monitoring applications. The aim of this work is to improve its diagnostic.In a first step, a coaxial transmission line was developed to characterize the materials involved in the duct over the frequency range 50 MHz - 1 GHz. The cement grout, segregation products of the cement grout and the injection wax were studied.In the second part of this work the previous results are used in the modelling of the devices. A parametrical study has shown the ability to get from the signals an estimate of the thickness of the void in the duct. This estimation method has been validated using a laboratory duct. Further, several improvements of the probes are proposed to get signals containing more information in order to get a better estimation of the target parameters.

Cette thèse s’inscrit dans le contexte de l’ANR ISABEAU (Innovating for Structural Adhesive Bonding Evaluation and Analysis with Ultrasounds, associant des physico-chimistes et des acousticiens) et cherche à apporter des connaissances nouvelles sur l’évaluation par ultrasons du niveau d’adhésion d’un collage structural par ondes de Lamb. La première partie porte sur l’aspect cohésif et particulièrement sur l’influence du paramètre de réticulation de réseaux époxys sur les courbes de dispersion des ondes de Lamb. La deuxième partie est consacrée à la caractérisation de niveaux d’adhésion dans une structure bicouche Aluminium Epoxy en tenant compte aussi bien des aspects cohésifs qu’adhésifs. Des échantillons à niveau d’adhésion connus et maîtrisés sont réalisés avec l’aide de physico-chimistes, où l’époxy est partiellement ou totalement réticulé, et où l’interface substrat adhésif a subit différents traitements chimiques et/ou mécaniques. Les résultats expérimentaux sont confrontés à ceux issus du modèle rhéologique de Jones résolu par éléments finis. Enfin, la troisième partie porte sur l’étude d’un assemblage tricouche Aluminium/Epoxy/Aluminium et cherche à qualifier différents niveaux d’adhésion à l’aide du modèle de Jones par ondes guidées et également par l’étude des fréquences de coupure des modes verticaux de la structure. / This thesis is in the context of the ANR ISABEAU (Innovating for Structural Adhesive Bonding Evaluation and Analysis with Ultrasounds, with the association of physico-chemists and acousticians) and seeks to bring new knowledge of the ultrasonic evaluation of the level of adhesion of structural bonding using Lamb waves. The first part focuses on the cohesive aspect, in particular on the influence of the crosslinking parameter of the polymer on the Lamb waves dispersion curves. The second part is dedicated to the evaluation of the adhesion level of a bi-layer Aluminum Epoxy taking into account the both cohesive and adhesive aspects. Samples of controlled and known adhesion levels are manufactured with the help of physico-chemists, where the crosslinking of the epoxy is partial or total, and the interface substrate-adhesive have been treated chemically and/or mechanically. The experimental results are compared to those obtained from a predictive model based on the rheological model of Jones solved by finite elements method. Finally, the third part focuses on the study of tri-layers Aluminum/Epoxy/Aluminum, looking for the qualification of different levels of adhesion with the Jones model using guided waves as well as the cut-off frequencies of the structure.

For the analysis of the wet pressing process, which was presented in the first part of this paper, a theoretical approach was chosen. This enabled the pre-definition of three quality-related priorities which now will be considered in detail in the second part. For further analysis, real process data, recorded in an early phase of the process implementation, are used. The challenge is that in this process status, the availability of data is limited or the data sets are incomplete. Supported by the theoretical approach, an easier interpretation of the process data, and in case of ambiguous issues, an accelerated decision making is expected. The objective is to show that this combination is suitable for the process analysis in an early production phase.

[pt] A avaliação não destrutiva ultrassônica é de extrema importância na indústria de óleo e gás, principalmente para ativos e estruturas sujeitos a condições que aceleram os mecanismos de falha. Apesar de amplamente difundidos, os métodos ultrassônicos não destrutivos dependem de uma força de trabalho especializada, sendo, portanto, suscetíveis a erros e demorados. Nesse contexto, métodos de reconhecimento de padrões, como o aprendizado de máquina, se encaixam convenientemente para solucionar os desafios da tarefa. Assim, este trabalho tem como objetivo a aplicação de técnicas de inteligência artificial para abordar a interpretação de dados adquiridos por meio de avaliação não destrutiva ultrassônica no contexto da indústria de óleo e gás. Para tanto, esta dissertação envolve três estudos de caso. Primeiramente, sinais de ondas guiadas ultrassônicas são usados para classificar os defeitos presentes em juntas soldadas de compósito termoplástico. Os resultados mostraram que, ao usar atributos extraídos com modelos autoregressivos, a acurácia do modelo de aprendizado de máquina melhora em pelo menos 72,5 por cento. Em segundo lugar, dados ultrassônicos em formato de imagens são usados para construir um sistema de diagnóstico de solda automático. A estrutura proposta resultou em um modelo computacionalmente eficiente, capaz de realizar classificações com acurácia superior à 99 por cento. Por fim, dados obtidos por simulação numérica foram usados para criar um modelo de aprendizado profundo visando estimar a severidade de defeitos semelhantes à corrosão em dutos. Resultados de R2 superiores a 0,99 foram alcançados. / [en] Ultrasonic non-destructive evaluation is of extreme importance in the oil and gas industry, especially for assets and structures subjected to conditions that accelerate failure mechanisms. Despite being widely spread, ultrasonic non-destructive methods depend on a specialized workforce, thus being errorprone and time-consuming. In this context, pattern recognition methods, like machine learning, fit conveniently to solve the challenges of the task. Hence, this work aims at applying artificial intelligence techniques to address the interpretation of data acquired through ultrasonic non-destructive evaluation in the context of the oil and gas industry. For that purpose, this dissertation involves three case studies. Firstly, ultrasonic guided wave signals are used to classify defects present in welded thermoplastic composite joints. Results have shown that, when using features extracted with autoregressive models, the accuracy of the machine learning model improves by at least 72.5 percent. Secondly, ultrasonic image data is used to construct an automatic weld diagnostic system. The proposed framework resulted in a lightweight model capable of performing classification with over 99 percent accuracy. Finally, simulation data was used to create a deep learning model for estimating the severity of corrosion-like defects in pipelines. R2 results superior to 0.99 were achieved.