Comparison between backprojection and algebraic methods for ultrasound tomography of concrete elements

• Ano de defesa: 2024
• Autor(a) principal: Anoni, Lara Guizi
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: algebraic methods; backprojection; concrete; concreto; image reconstruction; reconstrução algébrica; reconstrução de imagens; retroprojeção; tomografia ultrassônica; ultrasound; ultrasound tomography; ultrassom
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/18/18134/tde-14102024-151116/

Ultrasound tests have been widely applied for the evaluation of concrete elements, since they cause no damage to the inspected structure. One of its achievements in a simple analysis is the fast detection of non-homogeneities of the structure. The analysis of ultrasound results has gained complexity with the support of mathematical tools and computational data crossing, thus enabling the generation of tomographic images of internal sections of concrete. Among the several techniques addressed by the actual concrete tomography research are algebraic ones. Nevertheless, Backprojection method, widely used and consolidated in medical tomography, has been barely explored for concrete image reconstruction. This dissertation compares Backprojection, implemented in TUSom software, to recognized algebraic techniques. Additionally, methods such as Inverse Distance Weighting interpolation and interpolation of data using Artificial Neural Networks were employed to expand data and enhance image resolution. Velocity and attenuation tomography was generated from the time of flight of the ultrasonic wave and the variation in its amplitude through the reconstruction of numerically simulated and experimental concrete sections. As a primary result, it was possible to demonstrate the excellent performance of Backprojection, with and without the application of filters, in comparison to other evaluated image reconstruction techniques. Backprojection allowed for image generation even with a limited amount of data or enabled mesh enrichment to produce more accurate images. Although the interpolation techniques used reduced the image quality, IDW interpolation was successfully employed to generate images with only 12 readings. Furthermore, using the response of Backprojection as an initial guess for other techniques also proved to be a highly advantageous coupling method. With the results of this work, the aim is to have contributed to spreading the use of ultrasound tomography as a NonDestructive Testing method for concrete structures.