Investigation of ultrasonic transducer responses when coupled with solid materials

Joyce, Katelyn (2023) Investigation of ultrasonic transducer responses when coupled with solid materials. Masters thesis, Memorial University of Newfoundland.

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Abstract

This research focuses on ultrasonic transducer responses and elastic wave propagation in solid materials. This work was inspired by previous studies in geophysics, and its applications span several disciplines, such as material science, medicine and civil engineering. Previous geophysical work used a non-destructive testing method to investigate whether the frequency of a single-cycle ultrasonic pulse is related to the magnitude of its non-linear interactions. This work was inconclusive because the elastic wave frequency before and after propagating through the material was inconsistent. Hence, this research focuses on the fundamentals of how to analyze single-cycle pulses after they've travelled through solids using the Fast Fourier Transform and attempts to identify the source of the reported frequency discrepancy. This unexpected frequency discrepancy leads us to two hypotheses: (1) the examined material possesses the capacity for frequency conversion, or (2) aws in the experimental setup led to misleading results. To investigate these hypotheses, we conducted a series of experiments to establish the capabilities and limitations of our instruments. Before examining frequency conversion, it was essential to establish our setup's ability to generate and measure desired frequencies in the range of 50 kHz to 1 MHz. Using ultrasonic transducers to trigger wave propagation in various solid materials, we develop optimal operating parameters when coupling transducers to solid samples. The significance of this research lies in the understanding of how ultrasonic transducers couple with different materials. Although the motivation for this research lies in non-linear elasticity, these understandings apply to a diverse variety of fields. This contribution to the field of physics and instrumentation will lead to improved protocols for non-linear elastic data collection, ultimately enhancing our ability to measure and understand elastic wave propagation.

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