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 should allow one to predict surface wavefields not only at planar surfaces but also propagating along curved surfaces described by CAD or analytically.
展开▼
