Insights into the influence of magnetic fields on the propagation of elastic wave packets within a piezoelectric micro-scale beams

Piezoelectric beams are principal components of energy harvesters that rely on piezoelectric transduction mechanism. Some recent applications of piezoelectric energy harvesters include magnetic field energy scavenging from power lines, and in the detection of magnetic field. The coupling of piezoelectricity and magnetic field holds great potentials for applications in contact free self-powered micro-electromechanical systems (MEMs). In this study, a preliminary assessment is presented, of the influence of an axially-directed magnetic field on the propagation of a packet of transverse elastic waves within a piezoelectric micro-scale beam. Presented results include a qualitative assessment of the effect of voltage variations, the magnetic field and the size-effect parameter on the dispersion relation of the wave. The two limiting branches of the phase and group speeds, inferred through the Descartes' rule of sign, are also illustrated. The study demonstrates the dramatic increase in the propagating speed of the piezoelectric micro-scale beam as its material length scale approaches the geometric length. It also reveals the dampening of the beam's acoustic signature as a result of the axially-directed magnetic field effect.