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16th WCNDT 2004 - World Conference on NDT
CD-ROM Proceedings, Internet Version of ~600 Papers
Aug 30 - Sep 3, 2004 - Montreal, Canada
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SESSION: ARRAY TRANSDUCERS
ABSTRACT:
MINIMISATION OF MECHANICAL CROSS TALK IN PERIODIC PIEZOELECTRIC 
COMPOSITE ARRAYS 
D. Robertson,1 G. Hayward,1 A. Gachagan1 and P. Reynolds2 .
1University Of Strathclyde, Glasgow, United Kingdom;    2Weidlinger Associates, Los Altos, CA, United 
States.

This paper describes an investigation into mechanical cross talk within 1-3 and 2-2 connectivity 
piezoelectric composite array configurations, comprising a matrix of active piezoelectric elements embedded 
within a passive, polymeric, material. One way to take full advantage of the reported sensitivity and band 
width improvements from single crystal materials is to configure them as a piezoelectric composite. For this 
work, piezoelectric ceramic, lithium niobate and single crystal pmn-pt materials are investigated as the 
active component in the piezocomposite array designs. Within these piezoelectric configurations, the 
generation of ultrasonic inter pillar modes, which arise due to the periodicity of the active piezoelectric 
elements within the piezocomposite lattice, can be detrimental to the array performance. Consequently, 
finite element (FE) modelling, using PZFlex, is utilised to provide design techniques for the removal these 
inter pillar modes from the frequency band of interest and the realisation of unimodal piezocomposite 
transducer structures. Further FE modelling is used to generate dispersion data for 2-2, and doubly periodic 
1-3, composite substrates. This dispersion data is used to design the linear arrays, with the objective of 
minimising mechanical inter-element cross talk. A comparison between the FE predicted electrical 
impedance characteristics and mechanical cross coupling between array elements, for each composite 
material operating in air, is supported by experimentally measured data. Subsequently, the validated FE 
models are extended to include both operation into a solid load and the introduction of a backing material to 
simulate the operation of a practical NDE array transducer. The design techniques obtained from PZFlex are 
shown to produce arrays with low cross talk and the extent of the cross talk in manufactured and modelled 
ceramic, lithium niobate and pmn-pt single crystal arrays is compared.  
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MAIN AUTHOR:Anthony Gachagan, University Of Strathclyde, Glasgow, United Kingdom, University Of Strathclyde, United Kingdom
Paper CODE: 285

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