Ultrasonic Collimated Beams in Elastic Solids

Ultrasonic collimated beams are directed beams that propagate in materials with very little angular spread. Generation of such beams in solids enable high resolution imaging of heterogeneous and attenuating materials like concrete and noninvasive materials characterization of anisotropic materials like composites. We present a simple approach to generating ultrasonic collimated beams that relies on a novel approach to generating Bessel beams using radial modes of piezoelectric disc transducers. We first discuss the resonance and vibration characteristics of radial modes of piezoelectric discs using numerical and experimental studies. Then, analytical and numerical results on ultrasonic Bessel beam generation in elastic solids will be presented. Finally, a technique for the reduction of side lobes in Bessel beams will be discussed and numerical results on ultrasonic collimated beam generation in elastic solids will be presented.