Eriksson, Tobias J. R. (2016) Development of piezoelectric and electrodynamic flexural transducers for air-coupled ultrasonics. PhD thesis, University of Warwick.

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Abstract

Phased array ultrasound transducers could offer significant benefits over single element transducers in flow metering technology. By steering the ultrasonic beam transmitted through the flow, a single pair of phased array transducers have the potential to replace several pairs of traditional single element transducers. A first step in researching the potential for phased array transducers in flow meters is to investigate a suitable array element.

Flexural ultrasound transducers use the bending modes in a thin plate to generate ultrasound waves in low impedance media, such as liquids and gases. The behaviour of piezoelectric flexural transducers was studied using theoretical modelling, finite element (FE) modelling and experimental techniques. Some focus was put on characterising the passive layer of the transducer, which was shown to be largely responsible for the flexural behaviour. That is, the dimensions of the passive layer largely determined the resonance frequencies of the flexural vibration modes of the transducer. Also, the viability of flexural transducers for flow applications was assessed.

A new method of constructing air-coupled ultrasound phased array transducers was suggested. A 3 x 3 array was constructed and tested. The individual elements of the array behaved as single element flexural transducers, but the system as a whole could be improved to allow for better beam shaping.

A novel electrodynamic flexural transducer (EDFT) for air-coupled ultrasonic transduction without use of piezoelectric materials was proposed, developed and experimentally tested. The transducer combines the contactless coupling method used by electromagnetic acoustic transducers (EMATs) with the flexural vibration modes of a thin plate to transmit and receive ultrasound waves in air. The output pressure of the transducers was high, with SPLs over 100 dB, but the sensitivity was low compared to piezoelectric transducers.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QC Physics
Library of Congress Subject Headings (LCSH):	Ultrasonic transducers -- Design and construction, Piezoelectric transducers -- Design and construction, Flow meters -- Design and construction
Official Date:	September 2016
Dates:	Date Event September 2016 Submitted
Institution:	University of Warwick
Theses Department:	Department of Physics
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Dixon, Steve ; Ramadas, Sivaram Nishal
Format of File:	pdf
Extent:	xviii, 145 leaves : illustrations, charts
Language:	eng

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