Full band gap for surface acoustic waves in a piezoelectric phononic crystal

International audienceA plane-wave-expansion method suited to the analysis of surface-acoustic-wave propagation in two-dimensional piezoelectric phononic crystals is described. The surface modes of a square-lattice Y-cut lithium niobate phononic crystal with circular void inclusions with a filling fraction of 63% are identified. It is found that a large full band gap with a fractional bandwidth of 34% exists for surface acoustic waves of any polarization and incidence, coincidentally with the full band gap for bulk waves propagating in the plane of the surface. The excitation of surface acoustic waves by interdigital transducers is discussed

Theoretical analysis of damping effects of guided elastic waves at solid/fluid interfaces

International audienceA theoretical description of ideal and viscous fluid media is proposed to address the problem of modeling damping effects of surface acoustic waves and more generally of any guided elastic waves at the interface between viscous fluids and solids. It is based on the Fahmy-Adler eigenvalue representation of the elastic propagation problem, adapted to provide Green's function of the considered media. It takes advantage of previous efforts developed to numerically stabilize Green's-function computation process. This function is used to compute a harmonic admittance according to the Blötekjaër approach. The influence of acoustic radiation and viscosity effects on different kinds of waves excited on various substrates is reported and discussed

A least-action principle for the estimation of the slowness and the attenuation of pseudo surface acoustic waves

International audienc

Design guidelines of 1-3 piezoelectric composites dedicated to ultrasound imaging transducers, based on frequency band-gap considerations

International audiencePeriodic piezoelectric composites are widely used for imaging applications such as biomedical imaging or non destructive evaluation. We propose to view these structures as phononic crystals and investigate in this frame their properties with respect to periodicity. This approach is based on the investigation of band gaps, that strongly depend on the properties of the considered composites (geometry, size, nature of materials). It is motivated by the fact that band gaps in principle allow one to excite the thickness mode without exciting other parasitic waves. The plane-wave-expansion (PWE) method that we use has already been applied to periodic piezoelectric composites, but in contrast to previous approaches we consider not only waves propagating in the symmetry plane of the composite, but also waves propagating with a non-zero angle of incidence. The method is applied to a representative 1-3 connectivity piezocomposite in order to demonstrate its potentialities for design. The evolution of band gaps is explored with respect to the angle of incidence. All bulk waves that contribute to the setting-up of plate modes in the vicinity of the thickness mode are found and identified

A plane-wave expansion model to simulate phononic band-gap devices

International audienc

Full band gaps for surface acoustic waves in piezoelectric phononic crystals

International audienc

A full 3-D plane-wave-expansion model for piezocomposite structures

International audienc

Guided elastic waves along a rod-defect of a two-dimensional phononic crystal

International audienceIt was shown that elastic waves propagating out-of-plane in a two-dimensional phononic crystal can experience full-band-gaps for nonzero values of the wave-vector component parallel to the rods. By further inserting a rod defect, it is demonstrated that modes propagating along the rod defect can be localized within the band-gaps of the phononic crystal. Such waveguide modes are exhibited for a tungsten/epoxy composite containing an aluminum nitride rod as the rod defect. It is expected that guided modes of such a structure can be excited and detected electrically owing to the piezoelectric effect

A time domain approach for the analysis of periodic structures using finite element analysis

International audienc

Full 3D admittance computation of 1-3 piezocomposites radiating in fluids and solids

International audienc