Kudos for “When Nurse Becomes Patient”

Abstract

This paper is concerned with the guided elastic waves propagating in nanoscale layered periodic piezoelectric composites. The equations of wave motion based on the nonlocal piezoelectricity continuum theory are derived, and the symmetric wave mode is considered. According to the continuity conditions of the mechanical and electric field quantities on the interface between the two neighboring sub-layers, we obtain the dispersion relation to analyze the behavior of the guided elastic waves and the influences of the nanoscale size-effect. A cut-off frequency appears when taking the nanoscale size-effect into consideration. The variations of the mechanical displacements and the electrical potential are calculated and discussed. The influences of the nanoscale size-effect and the volume fractions on the mode conversions are analyzed in details. It is found that all the dispersion curves including the mode conversion zones are compressed under the cut-off frequency. As the ratio of the internal to external characteristic lengths increases, the cut-off frequency decreases, while the frequency and the wave number of the mode conversion reduce. The present investigation may help us to control the cut-off frequency and the mode conversions by tuning the internal or external characteristic lengths and the volume fractions of the nanoscale layered periodic piezoelectric composites. The corresponding results may provide the theoretical basis for nanoscale wave device applications to control the wave mode conversions and the cut-off frequency.