"Non-destructive testing (NDT) is critical to many precision industries because it can provide important information about the structural health of critical components and systems. In addition, NDT can also identify situations that could potentially lead to critical failures. Specifically, NDT by optical methods have become popular because of their non-contact and non-invasive nature. Shearography is a high-resolution optical NDT method for identification and characterization of structural defects in components and has gained wide acceptance over the last decade. Traditional workflow of NDT by shearography has been determined to be inefficient, due to the requirements of having experienced operators that must determine the most suitable loading methods to identify defects in samples under testing as well as to determine the best system arrangement for obtaining the maximum measuring sensitivity. To reduce the number of experiments that are required and to allow inspectors to perform NDT by laser shearography in a more efficient way, it is necessary to optimize the experimental workflow. The goal of the optimization would be an appropriate selection of all experimental variables including loading methods, boundary conditions, and system¡¯s sensitivities, in order to avoid repeating experiments several times in the processes of components characterization and health monitoring. To achieve this goal, a hybrid approach using shearographic fringe prediction with Finite Element Analysis (FEA) has been developed. In the FEA simulations, different loading conditions are applied to samples with defects, and in turn, the shearographic fringes are predicted. Fringe patterns corresponding to specific loading conditions that are capable of detecting defects are chosen and experimental tests are performed using those loading conditions. As a result, using this approach, inspectors could try different combinations of loading methods, and system¡¯s sensitivities to investigate and select appropriate experimental parameters to improve defect detection capabilities of the system by using low-cost computer simulations instead of lengthy and expensive experiments. In addition, to improve the identification of defects on the sample, camera calibration and image registration algorithms are used to project the detected defects on the sample itself to locate and visualize the position of defects during shearographic investigations. This hybrid approach is illustrated by performing NDT of a plate made of acrylic that has a partial hole at the center. Fringe prediction with finite element analysis are used to characterize the optimized experimental procedures and in turn, corresponding measurements are performed. A multimedia projector is employed to project the defects on the surface of the plate in order to visualize the location of the partial hole (defect). Furthermore, shearographic system is used for other applications including NDT of a composites plate and of a thin latex membrane. The procedures shows the effectiveness of the approach to perform NDT with shearography methods. "

Lobjectif de cette thèse était de concevoir et développer un dispositif expérimental réalisant des mesures dans la gamme micrométrique, qui soit compact, transportable et le plus stable possible pour la réalisation de mesures in-situ. Ce projet a donc contribué à la conception et à la réalisation dun dispositif interférométrique de shearographie qui constituera une base pour de futurs développements. Un interféromètre original de shearographie à chemins optiques quasi-communs et utilisant la technique du décalage de phase temporel a été présenté dans ce travail. Lélément clef du montage expérimental de shearographie est le dispositif de cisaillement (« shearing device », en anglais) : il sagit dun prisme qui sépare les états de polarisation TE et TM grâce à une couche mince polarisante et une fine lame de verre qui lui est accolée. Cet élément de cisaillement ainsi que lutilisation dune caméra CMOS et dune cellule à cristaux liquide pour modulateur de phase, ont permis la réalisation dun interféromètre compact, en ligne, relativement bon marché et à chemins optiques quasi-communs, lui conférant ainsi une grande stabilité par rapport aux perturbations extérieures. De plus, la sensibilité de cet interféromètre peut être ajustée pour différentes applications en modifiant la distance de cisaillement, par exemple en utilisant une lame de verre dépaisseur différente accolée au prisme séparateur de polarisation. Des logiciels pour lacquisition et le traitement des images ont également été développés afin de rendre le système simple dutilisation et convivial. Lefficacité de cet interféromètre de shearographie a été prouvée dans le domaine mécanique et une application originale a été développée dans le domaine de la biophotonique.

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[pt] A integridade de tubulações é um dos aspectos-chave para a operação segura e eficiente das estruturas offshore. Falhas em tubulações podem resultar em consequências econômicas e ambientais significativas, tornando a gestão da integridade de tubulações uma prioridade importante para a indústria. Uma das ferramentas mais eficazes para gerenciar tubulações em serviço é através de testes não destrutivos (NDT, na sigla em inglês). Neste estudo, inspeções de ultrassom e shearografia foram realizadas em tubulações metálicas com reparos compósitos ao longo de aproximadamente dois anos e seus resultados foram comparados. As amostras de tubos de aço com reparos compósitos foram submetidas a pouco mais de 13.500 horas de envelhecimento acelerado por névoa salina, em três diferentes temperaturas. As amostras foram removidas das câmaras de névoa salina em intervalos regulares e inspecionadas usando aparelhos de inspeção em campo. Os resultados mostraram que ambas as técnicas forneceram resultados consistentes entre cada inspeção, embora nem sempre fossem consistentes entre si. Mapas comparando as detecções e a precisão de cada técnica foram fornecidos. A viabilidade de cada técnica como ferramenta de campo para monitorar a integridade das tubulações também foi avaliada com resultados positivos. Além disso, uma metodologia de Arrhenius modificada foi proposta como um primeiro passo para prever a propagação de danos a longo prazo. / [en] Pipeline integrity is one of the key aspects for safe and efficient operation of offshore structures. Pipeline failures can result in significant economic and environmental consequences, making pipeline integrity management a top priority for the industry. One of the most effective tools for managing in-service pipelines is non-destructive testing (NDT). In this study, ultrasound and shearography inspections were performed on composite pipeline repairs over the course of approximately two years and their results were compared. The test samples evaluated were steel pipes with composite repairs and were submitted to just over 13,500 hours of salt-spray accelerated ageing, under three different temperatures. Test samples were removed from the salt-spray chambers at regular intervals and inspected by using field inspection apparatus. The results showed that both techniques provided consistent results between each inspection, although not always being consistent with each other. Maps comparing detections and accuracy of each technique were provided. The feasibility of each technique as a field tool for monitoring pipeline integrity was also evaluated with positive results. Furthermore, a modified Arrhenius methodology was proposed as a first step towards predicting long-term damage propagation.