Zennaro, Marco; NSIRC National Structural Integrity Research Centre; United Kingdom

Zennaro, M.; NSIRC; United Kingdom
Haig, A.; Eddyfi; United Kingdom
O´boy, D.J.; AACME; United Kingdom
Walsh, S.J.; AACME; United Kingdom

ID: ECNDT-0253-2018
Download: PDF
Session: Guided Waves Techniques 1
Room: G3
Date: 2018-06-14
Time: 13:50 - 14:10

The use of dry-coupled thickness-shear piezoelectric transducers for the generation of guided waves is well present in industry. The effective control of guided waves requires the designing of transducers to achieve a uniform excitation over frequency and contact area. This is necessary to control the wave modes generated such that only modes with characteristics useful for inspection are significantly transmitted and received. Recent research has identified the need to improve the ultrasonic performance in terms of amplitude and signal to noise ratio of guided waves via a miniaturization of the transducers, normally used in arrays in large numbers. The influence of the geometry of the transducer on the generation of guided waves needs to be investigated. It is well known that the geometry of the transducers influences the normal modes of the ultrasonic transducers, which in turn can influence their ability to excite ultrasonic guided waves. The relation of length, thickness and width among each other and their influence on resonances is known in the literature. However, the influence of geometry on ultrasonic performance is still not completely understood: the influence of mode coupling and the presence of satellite modes might be detrimental for the generation of guided waves, especially where the intention is to use the transducers at non-resonant frequencies. These requirements drive the testing of design changes in terms of geometry and shape of the electrodes to improve the ultrasonic performance of the aforementioned transducers. Design changes in terms of length, thickness and width are analysed both numerically (by finite element analysis) and experimentally (with Laser Vibrometry) to offer a characterisation of existing piezoelectric elements. Moreover the influence of the geometry of the electrode is investigated. The changes are then discussed in terms of mode shape of the transducer and ultrasonic output to indicate the preferable design changes.