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An Investigation of the Detailed Characterisation of Ultrasonic Transducer Behaviour.

Bangash, M. A. (1995) An Investigation of the Detailed Characterisation of Ultrasonic Transducer Behaviour. Doctoral thesis, University of Surrey (United Kingdom)..

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Abstract

Measurements of the complex pressure fields radiated by a variety of piezoelectric transducers, have been made using miniature piezoelectric polymer hydrophones, in order to reconstruct the surface vibration distributions of the transmitting transducers. These measurements have been compared with optical diffraction tomography measurements of the same fields made independently by the Physikalisch-Technische Bundesanstalt. Very good agreement was found for the two techniques. The vibrational behaviour of a ceramic transducer in the vicinity of its fundamental thickness mode resonance was also investigated using source reconstruction. The element was found to exhibit a strongly non piston-like behaviour, especially at resonance, in confirmation of previous suggestions in the literature. Error propagation in the technique of Fourier optical source reconstruction was investigated by numerical simulation. A range of measurement errors were identified and the effects of errors in assumed operating frequency, non-uniform sampling (probe positional jitter) and misalignment were considered, as were techniques for reducing the errors due to non-uniform sampling. A novel technique for the spatial characterisation of ultrasonic receivers has been developed, based on measurements of the two-dimensional directivity. A Gaussian transducer for the quasi-plane wave irradiation of such receivers was designed and tested. Preliminary measurements on a polymer receiving transducer with a 5mm radius, were made at 2MHz. Although limited in resolution due to experimental constraints, a good reconstruction of the spatial sensitivity function of the receiver was obtained. In addition, modifications to the receiving element, by using damping material to mask out some regions, could be identified by this reconstruction technique. The work reported has significantly advanced the techniques available for the characterisation of ultrasonic transducers.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : Bangash, M. A.
Date : 1995
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1995.
Depositing User : EPrints Services
Date Deposited : 30 Apr 2019 08:08
Last Modified : 20 Aug 2019 15:33
URI: http://epubs.surrey.ac.uk/id/eprint/851473

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