Unidirectional Interfacial Waves in Gyroscopic Elastic Systems

Wave propagation in an elastic triangular lattice connected to a system of gyroscopic spinners is studied. The attention is focussed on waves travelling at the interface between two half-planes, where the spinners rotate in opposite directions. The relation describing the dispersive properties of these interfacial waves is given in closed form. These interfacial waves exist within a narrow frequency interval in the internal stop-band for the bulk medium, and are characterised by very low group velocity. The results of the dispersion analysis are confirmed by independent finite element simulations, which show that time-harmonic forces applied in proximity of the interface generate waves that are localised at the interface and do not propagate inside the bulk of the medium. In addition, these waves mainly propagate in one specific direction, that can be predicted from the dispersion curves and that can be reversed by changing the direction of rotation of the spinners. The model described here is an alternative to other elastic structures proposed in the literature and, considering its tuning properties, may be useful for different engineering applications including wave guiding, vibration isolation and energy harvesting.