Broadband controllable defect state of longitudinal waves in one-dimensional pillared phononic crystal beams

Defect state of phononic crystals (PCs) has attracted fast-growing attention due to wave energy localization, which can serve as an effective means of controlling elastic waves. In this paper, we investigate the defect state of a one-dimensional (1D) broadband controllable pillared PC beam consisting of pillared permanent magnets on an aluminium beam through numerical simulations and experiments. First, the width and position of the band gap are altered by adjusting the height of the magnetic pillars’. Then, building on this foundation, we successfully observe the controllable defect states of longitudinal waves at the defects of pillared PC beams through a simple adjustment of the height of the defective magnetic pillars’. Finally, we conduct an experimental validation to confirm the feasibility of the localization behavior of elastic waves in the pillared PC system. This research offers a straightforward method to dynamically control the defect state of PCs and enhance the applications for defected PCs, spanning novel filters, defect detectors, and broadband energy harvesting.