Experiments in phononic crystal plates for negatively-refracted guided shear-horizontal waves by using magnetostrictive patch transducers

Abstract

Experiments performed for negatively-refracted bulk shear waves in elastic media have been reported in literature, not for negatively-refracted guided shear waves in a plate. In this work, we present the negatively-refracted guided shear-horizontal wave experiment results in a thin Phononic Crystal (PC) plate. An interesting feature with negative refraction experiments in a plate, compared with those in a bulk medium, is that one can measure full wave field in a nominal base plate as soon as the negatively-refracted wave exists from a PC plate. Therefore, the actual wave path in the nominal plate can be visualized by the present experiment. For successful experiments, among others, the use of proper transducers is important. In particular, pure shear-horizontal wave generating transducers with narrow beam width are preferred. Here, we employed PSA-OPMT's (Planar Solenoid Array Orientation-adjustable Patch-type Magnetostrcitve Transducers) for wave generation and measurement. The negative refraction angle estimated from the experiments is shown to be in good agreement with the theoretically calculated values through Snell's law. For instance, the experimentally-determined refraction angle is -11.35 degree at the frequency of 220 kHz and it differs within 10% from the theoretical value, -12.67 degree.