This thesis summarizes my work at the University of Victoria to design and evaluate a proof-of-concept instrument called the Confocal Acoustic Holography Microscope (CAHM). The instrument will be able to measure small changes in temperature and composition in a fluid specimen, which can be indirectly measured via small fluctuations in the speed of sound. The CAHM combines concepts of confocal microscopy, interferometry, and ultrasonic imaging. This recent work in confocal acoustic holography has progressed from our previous research in confocal laser holography. The prototype CAHM design uses a frequency of 2.25 MHz, and can measure sound speed changes of 16 m/s, temperature changes of 5°C, with a spatial resolution of 660 μm. With future improvements to the CAHM, utilizing the latest technologies such as 2D array detectors, MEMS, and acoustic lenses, we expect resolutions of 1 m/s, 0.5°C, and 150 μm. The design of the CAHM involved the production of a 3D CAD layout of the optomechanical components and ray tracing simulations using Zemax optical design software. Simulated acoustic holograms and fringe shifts were produced and they were found to match up very well with theoretical calculations. A simplified acoustic holography instrument was built and tested. Speed of sound measurements were made for several test specimens, while keeping temperature constant. Specimens of ethanol, isopropanol, acetic acid, glycerine, and mineral oil were measured. Holograms were collected for acetic acid and mineral oil and were compared to the reference case (distilled water). The fringe spacing and phase shifts measured experimentally matched up well with the Zemax simulations and the theoretical calculations. Hence, the popular Zemax optical software can be effectively used to design acoustic instruments. To our knowledge, this is the first use of Zemax for acoustic designs. Based on the successful results of the simulations and experiments, the CAHM is expected to have many useful applications, especially in medical diagnostics where it could be used to measure density and temperature within the human body. Phase contrast images could also be used to help identify suspicious lesions, such as those found in prostate or breast tissue. Other applications include non-destructive testing of electronic and mechanical parts, measurements of fluid samples, material science experiments, and microgravity experiments, where non-invasive examination is required.

In this thesis, two ultrasonic timing methods are used in order to investigate the accuracy and reliability of measurements for surface breaking cracks having different orientations and heights. Also the best applicable measurement technique is searched by comparing the received test results. These methods are the Time of Flight Diffraction (TOFD) Method using diffraction of longitudinal waves and another method using the reflection of shear waves from the crack tips. In order to simulate and measure the height of surface breaking cracks three sets of test blocks from steel, and two sets of wedges from plexiglas material are manufactured. Also several probes having frequencies of 2Mhz, 4Mhz, 5Mhz and angles of 45o and 70o are used. Some test procedures are created to make realistic comparisons between the test results and the ones found by previous studies in literature. The results are compared according to the standard deviations of errors in crack height measurements and it is found that the depth, orientation of defects and the frequency of probes have considerable affect on the results. With wider probe angles and higher frequencies of probes to some extent the errors are observed to be running low and the height of cracks could be measured closer to the original size. The amount of the errors is increased in measurements with the increasing angle of cracks. The results of both methods are found to be very satisfactory. A range of &plusmn / 0.5 mm for means of error from the original vertical crack heights is determined. The results agree with the previous studies.

Terahertz radiation or T-rays or THz radiation refers to the region of the electromagnetic spectrum between approximately 100 GHz and 30 THz. This spectral region is often referred to as the THz gap as these frequencies fall between electronic (measurement of field with antennas) and optical (measurement of power with optical detectors) means of generation. THz measurements may yield useful information about the structural and chemical nature of the material inspected. Examples include detection of voids in materials and protein binding in biomolecules. This report provides an overview of THz measurements of defects in fiber composites. We find that it efficiently detects defects such as voids and delamination in glass fiber composites better than ultrasound, which was widely used for defect characterization in glass fiber earlier. Comparison of the existing methods with THz is presented in the report for characterization of defects.

O presente trabalho foi desenvolvido com o intuito de estudar a utilização do método de ensaio não destrutivo de ultrassom para inspecionar e caracterizar materiais compósitos. Os objetivos principais da pesquisa foram medir a espessura, encontrar e dimensionar delaminações em reparo de material compósito laminado para tubulações e medir a velocidade do som no concreto para o cálculo do módulo de elasticidade. Inicialmente foram estudados os parâmetros físicos relevantes inerentes a cada material para o método de ultrassom, para então estabelecer uma metodologia de inspeção. A técnica de pulso-eco foi capaz de encontrar as descontinuidades no compósito laminado. Para a determinação do módulo de elasticidade do concreto, a técnica de transmissão foi utilizada obtendo-se resultados satisfatórios. / This work was developed with the intention of using the non-destructive testing method of ultrasound to inspect and characterize composite materials. The main objectives of the research were to find and size delaminations in laminated composite material for pipeline repair and to measure sound speed in concrete in order to determine its elastic modulus. Initially, the relevant physical parameters inherent to each material were studied regarding ultrasound so to establish a testing methodology. The pulse-eco technique was used to find discontinuities in laminated composite. To determine the elastic modulus of concrete, the through transmission technique was used with satisfactory results.

Submitted by Maria Suzana Diniz (msuzanad@hotmail.com) on 2015-11-11T13:50:57Z No. of bitstreams: 1 arquivototal.pdf: 3438463 bytes, checksum: 58df13a5453da33ec72ad547b4ea7d40 (MD5) / Made available in DSpace on 2015-11-11T13:50:57Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 3438463 bytes, checksum: 58df13a5453da33ec72ad547b4ea7d40 (MD5) Previous issue date: 2014-12-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The use of ferromagnetic materials such as steel have been abundant in products and manufacturing equipment due to their magnetic properties, which generates an interaction between them and the applied magnetic fields. This interaction has been studied for the development of Non-Destructive Testing (NDT) used to detect cracks, heterogeneity, degree of deformation and accompanying precipitation of desirable and / or undesirable phases in materials. In this work a NDT technique based on the application of magnetic fields in the region of reversal of the magnetic materials has been developed. There were compared an SAE 1045 steel and an ASTM 6261 aluminum alloy, being then classified as paramagnetic and ferromagnetic, respectively. It was tried to knowledge of how the variables metallographic geometry and texture could interfere with magnetic induction (B) in these materials. It was determined the values of H and optimum thickness, the equations relating the geometry, thickness, and shape of the samples had magnetic anisotropy and rotating the samples. The technique proved promising with both materials interacted with the magnetic field applied by working in a common region for the two materials magnetization, the magnetic region of reversibility. The method was sensitive to metallographic texture, being promising for determining the best direction of magnetization in materials for electrical purposes. The geometry of the samples influenced the amount of magnetic induction, carrying out mathematical corrections for the comparison of different shapes, sizes, thicknesses and materials is required. For the SAE 1045 steel was magnetic anisotropy due to the existence of metallographic texture from the manufacturing process by rolling steel. For aluminum ASTM 6261 did not occur in magnetic anisotropy due to the lack of metallographic texture. / O uso de materiais ferromagnéticos como o aço tem sido abundante na fabricação de produtos e equipamentos devido às suas propriedades magnéticas, que gera uma interação entre eles e os campos magnéticos aplicados. Essa interação tem sido estudada para o desenvolvimento de Ensaios Não Destrutivos (END) utilizados na detecção de trincas, heterogeneidades, grau de deformação e acompanhamento da precipitação de fases desejáveis e/ou indesejáveis em materiais. Neste trabalho foi desenvolvida uma técnica END baseada na aplicação de campos magnéticos na região de reversibilidade magnética dos materiais. Foram comparados um aço SAE 1045 e uma liga de alumínio ASTM 6261, sendo eles classificados como ferromagnético e paramagnético, respectivamente. Buscou-se o conhecimento de como as variáveis geometria e textura metalográfica poderiam interferir nas respostas de campo magnético induzido (B) nestes materiais. Determinaram-se os valores de H e espessuras ideais, as equações que relacionam geometria, espessura e formato das amostras e se havia anisotropia magnética rotacionando as amostras. A técnica se mostrou promissora, tendo ambos os materiais interagido com o campo magnético aplicado por se trabalhar em uma região de magnetização comum aos dois materiais, a região de reversibilidade magnética. O método se mostrou sensível à textura metalográfica, sendo promissora para a determinação da direção de melhor magnetização em materiais para fins elétricos. A geometria das amostras influenciou no valor de campo magnético induzido, sendo necessária a realização de correções matemáticas para a comparação de materiais de diferentes formatos, espessuras e tamanhos. Para o aço SAE 1045 ocorreu anisotropia magnética em virtude da existência de textura metalográfica proveniente do processo de fabricação por laminação do aço. Para o alumínio ASTM 6261 não ocorreu anisotropia magnética em virtude da inexistência de textura metalográfica.

O presente trabalho foi desenvolvido com o intuito de estudar a utilização do método de ensaio não destrutivo de ultrassom para inspecionar e caracterizar materiais compósitos. Os objetivos principais da pesquisa foram medir a espessura, encontrar e dimensionar delaminações em reparo de material compósito laminado para tubulações e medir a velocidade do som no concreto para o cálculo do módulo de elasticidade. Inicialmente foram estudados os parâmetros físicos relevantes inerentes a cada material para o método de ultrassom, para então estabelecer uma metodologia de inspeção. A técnica de pulso-eco foi capaz de encontrar as descontinuidades no compósito laminado. Para a determinação do módulo de elasticidade do concreto, a técnica de transmissão foi utilizada obtendo-se resultados satisfatórios. / This work was developed with the intention of using the non-destructive testing method of ultrasound to inspect and characterize composite materials. The main objectives of the research were to find and size delaminations in laminated composite material for pipeline repair and to measure sound speed in concrete in order to determine its elastic modulus. Initially, the relevant physical parameters inherent to each material were studied regarding ultrasound so to establish a testing methodology. The pulse-eco technique was used to find discontinuities in laminated composite. To determine the elastic modulus of concrete, the through transmission technique was used with satisfactory results.

This thesis describes and investigates different approaches to indoor mapping and navigation. A system capable of mapping large indoor areas with a stereo camera and/or a laser camera mounted to e.g. a robot or a human is developed. The approaches investigated in this report are either based on Simultaneous Lo- calisation and Mapping (SLAM) techniques, e.g. Extended Kalman Filter-SLAM (EKF-SLAM) and Smoothing and Mapping (SAM), or registration techniques, e.g. Iterated Closest Point (ICP) and Normal Distributions Transform (NDT).In SLAM, it is demonstrated that the laser camera can contribute to the stereo camera by providing accurate distance estimates. By combining these sensors in EKF-SLAM, it is possible to obtain more accurate maps and trajectories compared to if the stereo camera is used alone.It is also demonstrated that by dividing the environment into smaller ones, i.e. submaps, it is possible to build large maps in close to linear time. A new approach to SLAM based on EKF-SLAM and SAM, called Submap Joining Smoothing and Mapping (SJSAM), is implemented to demonstrate this.NDT is also implemented and the objective is to register two point clouds from the laser camera to each other so that the relative motion can be obtained. The NDT implementation is compared to ICP and the results show that NDT performs better at estimating the angular difference between the point clouds.

This dissertation is concerned with three-dimensional (3D) sensing and 3D scan representation. Three-dimensional records are important tools in several disciplines; such as medical imaging, archaeology, and mobile robotics. This dissertation proposes the normal-distributions transform, NDT, as a general 3D surface representation with applications in scan registration, localisation, loop detection, and surface-structure analysis. After applying NDT, the surface is represented by a smooth function with analytic derivatives. This representation has several attractive properties. The smooth function representation makes it possible to use standard numerical optimisation methods, such as Newton’s method, for 3D registration. This dissertation extends the original two-dimensional NDT registration algorithm of Biber and Straßer to 3D and introduces a number of improvements. The 3D-NDT scan-registration algorithm is compared to current de facto standard registration algorithms. 3D-NDT scan registration with the proposed extensions is shown to be more robust, more accurate, and faster than the popular ICP algorithm. An additional benefit is that 3D-NDT registration provides a confidence measure of the result with little additional effort. Furthermore, a kernel-based extension to 3D-NDT for registering coloured data is proposed. Approaches based on local visual features typically use only a small fraction of the available 3D points for registration. In contrast, Colour-NDT uses all of the available 3D data. The dissertation proposes to use a combination of local visual features and Colour-NDT for robust registration of coloured 3D scans. Also building on NDT, a novel approach using 3D laser scans to perform appearance-based loop detection for mobile robots is proposed. Loop detection is an importantproblem in the SLAM (simultaneous localisation and mapping) domain. The proposed approach uses only the appearance of 3D point clouds to detect loops and requires nopose information. It exploits the NDT surface representation to create histograms based on local surface orientation and smoothness. The surface-shape histograms compress the input data by two to three orders of magnitude. Because of the high compression rate, the histograms can be matched efficiently to compare the appearance of two scans. Rotation invariance is achieved by aligning scans with respect to dominant surface orientations. In order to automatically determine the threshold that separates scans at loop closures from nonoverlapping ones, the proposed approach uses expectation maximisation to fit a Gamma mixture model to the output similarity measures. In order to enable more high-level tasks, it is desirable to extract semantic information from 3D models. One important task where such 3D surface analysis is useful is boulder detection for mining vehicles. This dissertation presents a method, also inspired by NDT, that provides clues as to where the pile is, where the bucket should be placed for loading, and where there are obstacles. The points of 3D point clouds are classified based on the surrounding surface roughness and orientation. Other potential applications include extraction of drivable paths over uneven surfaces.

Entre otras aplicaciones, el Grupo de Tratamiento de Señal (GTS) de la Universidad Politécnica de Valencia ha trabajado tradicionalmente en el campo de los ensayos no destructivos por ultrasonidos. el GTS ha desarrollado sofisticados algoritmos de procesado de señal para la detección y caracterización en materiales dispersivos. El procedimiento de inspección ultrasónica de materiales implica la obtención de un registro o señal mediante un equipo emisor-receptor de ultrasonidos. Este registro será posteriormente procesado para obterner información del material. La extracción de características puede realizarse calculando parámetros temporales y/o frecuenciales de los registros en cuestión. Estos parámetros contienen información que está relacionada con propiedades físicas de los materiales y que podrán ser empleados en definitiva para clasificar y caracterizar el material. El objetivo de la tesis es el de ampliar el conjunto de parémetros que se han venido usando de manera tradicional en el grupo. Los nuevos parámetros proponen un cambio de perspectiva mediante el uso de técnicas basadas en el tratamiento digital de imagen. Se presenta una colección de descriptores geométricos y de forma que serán aplicados a las imágenes obtenidas a partir de los diagramas tiempo-frecuencia. Los citados parámetros se aplicarán junto con los parámetros que componen el modelo tradicional, o versiones modificadas de éstos, a la caracterización ultrasónica de materiales dispersivos blandos. En la tesis se presenta un modelo matemático afín a los tipos de materiales que han sido evaluados en este trabajo. Se define así un esquema que modela en el dominio de la frecuencia el registro de señal procedente de la inspección ultrasónica del material. Se proponen y estudian además diferentes métodos con el objetivo de llevar a cabo el análisis espectral de la señal ultrasónica y se discuten diferentes alternativas para la obtención y mejora de los diagramas tiempo-frecuencia. / Gómez García, S. (2010). Descriptores Geométricos y de Forma: Aplicación a la caracterización ultrasónica de materiales [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8722 / Palancia

Les squats et les head-checks sont des défauts générés par l’endommagement des rails dû à la fatigue de contact de roulement, ils sont localisés à la surface du champignon du rail. La possibilité de les détecter en modes statique et dynamique lorsque leur profondeur se situe sous le seuil critique de 5 mm, constitue un challenge important pour l’industrie ferroviaire. Les méthodes d’inspection existantes ne permettent pas de les déceler avec certitude. L’objectif de ce travail a été de développer des méthodes alternatives pour l’inspection automatique du rail permettant de détecter ces défauts superficiels. Nous montrons que les méthodes sans contact : Ultrasons-Laser et EMATs (transducteurs électromagnétiques) sont très performantes pour la détection des défauts définis précédemment en utilisant des ondes acoustiques de surface, notamment dans le cas d’un contrôle dynamique. Cette étude présente les deux méthodes utilisées pour la génération et la détection des ondes de Rayleigh. Des essais sont effectués en modes statique et dynamique. Les résultats obtenus montrent la faisabilité des méthodes de contrôle non destructives envisagées pour la détection de squats et de head-checks de différentes profondeurs. Les essais EMAT se sont notamment révélés satisfaisants pour des vitesses importantes de déplacement de l’échantillon. / Squats and head-checks are a form of near surface rolling contact fatigue damage found in rail heads. The ability to detect these defects in static and dynamic modes when their depth is under the critical threshold of 5 mm represents a major challenge for the rail industry. Conventional inspection methods do not allow their detection with certainty. Therefore, the aim of this work was to develop alternative methods for automatic rail inspection leading to open cracks detection. We show that non-contact methods: Laser-Ultrasonics and electromagnetic transducers (EMAT) are very efficient for the detection of the previously defined defects using surface acoustic waves, particularly in the case of a dynamic control. This study presents two methods for the generation and detection of Rayleigh waves. Static and dynamic tests are performed. The experimental results show the feasibility of the envisaged methods for the detection of squats and head-checks of different depths. Especially, the EMAT tests were satisfactory for high speeds displacement of the sample.