Multi-Angle Beam Generation and Steering via Meander-Line-Coil EMATs

Hurrell, Sam (2025) Multi-Angle Beam Generation and Steering via Meander-Line-Coil EMATs. Doctoral thesis, University of Wales Trinity Saint David.

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Abstract

This thesis investigates Meander-Line Coil (MLC) Electromagnetic Acoustic Transducers (EMATs) for the purposes of Non-Destructive Testing (NDT), focusing on their theoretical foundations, simulated modelling, and experimental validations. Whilst the detection of defects was not investigated, this work thoroughly examines the EMAT’s capability as a conventional transducer to steer the angle of its oblique ultrasonic waves. This culminates in the innovative generation of multi-angle bulk waves simultaneously from a single EMAT. The practical applications of a multi-angle EMAT include the ability to perform sectoral scans, currently only possible by Phased Array (PA) Ultrasonic Testing (PAUT). This is beneficial as EMATs are not restricted to using a coupling liquid for their operation, allowing them to be used on high-temperature materials or in hazardous areas where a coupling medium is unacceptable. The thesis begins with an overview of modern NDT methods (particularly Ultrasonic Testing (UT)) and explores the principles of electromagnetism relevant to EMATs. An in-depth analysis of EMATs covers their transduction methods, design configurations, and historical development, along with their associated electronic circuitry. A significant portion of this thesis involves constructing and validating a 2D Finite Element Method (FEM) model of the MLC EMAT using ‘COMSOL Multiphysics’ and understanding its properties through parametric studies. The following experimental validation focuses on the MLC EMAT's performance on non-ferromagnetic workpieces in comparison to the simulations to assess their accuracy. Further investigations examine the transmitted bulk waves via parametric studies on both the EMAT's magnetic and coil configurations. This research concludes with an exploration of generating multi-angle bulk waves by modifying the transmission signals through EMAT coils. These waves are analysed using the Fast Fourier Transform (FFT) to extract an individual angle’s A-scan from the overall complex signal received, demonstrating the feasibility of this novel approach. This study shows that EMATs can accurately steer the direction of their bulk waves as a function of frequency, supported by reliable simulated modelling and experimental evidence. The primary outcome of the research is the proof of concept for simultaneous transmission and reception of multi-angle waves via EMAT technology. This has the potential to enhance the EMAT’s defect detection by an increased coverage, the triangulation of these defects from different angled waves, and a greater range of flaw orientation.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	EMATs, beam steering, MLC, ultrasonic, directivity, multi-angle
Subjects:	T Technology > TJ Mechanical engineering and machinery
Divisions:	Theses and Dissertations > Doctoral Theses
Depositing User:	Sam Hurrell
Date Deposited:	14 Oct 2025 14:13
Last Modified:	14 Oct 2025 14:13
URI:	https://repository.uwtsd.ac.uk/id/eprint/3926

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