Study and implementation of fast compressive 3-D total focusing method ultrasonic imaging using 2-D sparse arrays

Abstract

This thesis explores the increasing focus on three-dimensional imaging in ultrasonic nondestructive testing (NDT), emphasizing the significance of phased array ultrasonic testing (PAUT) and the emerging potential of the total focusing method (TFM) for high-resolution imaging. When applying this method to a 2-D imaging context using linear array probes, limitations arise concerning the identification of defects, particularly in scenarios with random orientations such as cracks, demanding the necessity for 3-D imaging solutions. The study addresses the challenges associated with the use of volumetric imaging in NDT, primarily focusing on matrix phased arrays within the TFM framework, aiming to develop innovative ultrasonic acquisition and data processing strategies to enhance 3-D TFM productivity. The project’s scope involves two key facets. Firstly, the project examines the complexity associated with managing a high number of elements in ultrasonic matrix phased arrays, exploring element reduction techniques, notably element selection strategies like sparse arrays. Secondly, the research focuses on methodologies to reduce the substantial data volume generated, investigating innovative data compression techniques, such as compressive sensing (CS) approaches. The integration of these strategies is intended to pave the way for the development of lightweight ultrasonic scanners and to lay the theoretical foundation for their practical realization. Initially, this study introduced a method for designing sparse array layouts applied to linear phased arrays and compared it to the FMC and plane wave imaging (PWI). Then, this sparse array methodology was adapted and extended to matrix phased arrays to optimize data acquisition efficiency while balancing 3-D imaging quality. Finally, the sparse array methodology was combined with an efficient CS framework to match increased data acquisition rates with reductions in the data volumes at the same time. Experimental trials involving samples containing artificial flaws were performed to evaluate the proposed approach. As a result of this project, three significant outcomes were realized: (1) the proposed sparse-TFM reduced firing events by more than 90% while providing high accuracy, and its performance was superior to PWI; (2) an optimized sparse array technique for matrix probes achieved a 9.8-fold acceleration in 3-D TFM, preserving image quality and defect sizing capabilities; and (3) utilizing CS and sparse arrays enabled ultrasonic signal recovery at sampling rates below the Nyquist limit and faster TFM imaging, indicating a potential reduction of the hardware complexity in ultrasound devices for NDT applications.

Date	12 Apr 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Pierre Bélanger (Supervisor)