Magnetically tunable band gaps and defect states of longitudinal waves in hard magnetic soft phononic crystal beams

Abstract

Phononic crystals consisting of hard magnetic soft materials have attracted extensive attention due to their finite deformation when subjected to magnetic loading. However, achieving effective control defect states remains a challenge. We propose a novel design of hard magnetic soft phononic crystal beams to achieve the tunability of band gaps and defect states for longitudinal waves when the defect is introduced by adjusting magnetic loading. The nonlinear deformation of the unit cell under varying magnetic loadings is discussed. Then, the magnetically controllable band gaps and defect states of longitudinal waves are successfully observed without changing the structure. The edges and widths of band gaps are significantly affected by magnetic induction intensity because of the large magnetic induced deformation. The frequency and location of defect states can be dynamically adjusted by changing the distribution of magnetic induction intensity in different unit cells, which is robust against the defect location. The magnetically tunable band gaps and defect states of longitudinal waves offer a novel approach for the development of adaptive programmable devices, such as wave switching and energy harvesting.