| ABSTRACT: | SIMULATION OF ULTRASONIC EXAMINATIONS USING SURFACE ACOUSTIC WAVES
N.A. Leymarie1, A. Lhémery1, P. Calmon1 and R. Coulette2
1Commissariat À L'énergie Atomique, Gif-sur-yvette, France, 2Snecma, Evry, France
The UT simulation tools developed at the French Atomic Energy Commission (CEA) in the CIVA software
platform were up to now limited to methods based on bulk ultrasonic waves. This study aims at extending
the capabilities of the models to deal with testing configurations using surface acoustic waves (SAW). In
such configurations, specific transducer arrangement is made to generate and receive surface waves. Very
often, the field is generated by refracting a bulk longitudinal beam at the surface under test at a specific
angle (e.g. Rayleigh angle).
In the present work, a model has been derived to predict the SAW wavefield in the part under test by an
arbitrary transducer as well as the leaky surface acoustic wave associated to the SAW propagation radiated
in the coupling medium. First, asymptotic expressions for SAW and leaky surface waves are derived in the
case of a point source radiating from a fluid medium over an elastic half-space. A geometrical interpretation
is proposed allowing to derive a more general model based on the pencil method. Fields radiated by an
arbitrary transducer are obtained and expressed as impulse responses to be convolved with an excitation
pulse to quantitatively predict useful quantities (particle displacement, stress etc.). Examples of surface
wavefields computed by the proposed model are given and compared with exact results (planar interface)
showing its accuracy. The method allows one to predict surface wavefields not only at planar surfaces but
also propagating
along curved surfaces. Being implemented within CIVA the method allows to deal with curved surfaces
described by CAD.
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