Functionally graded elastic valley metamaterials for low-frequency surface wave manipulation

This paper proposes a groundbreaking surface wave metamaterial, which leverages common materials such as concrete and soil and operates on the principles of local resonance. The topological phase transition is controlled with the geometry of the resonant element, which is verified through the theoretical Valley Chern number. Moreover, a functionally graded elastic metamaterial is devised to achieve the topological rainbow effect of the low-frequency surface waves. The utilization of piezoelectric sheets validates energy harvesting with broadband low frequency for graded topological metamaterial. This study offers an innovative method for controlling surface elastic waves, paving the way for new avenues in energy harvesting, vibration mitigation, and noise reduction.