Magneto-mechanical-thermal coupling tunability of the topological interface state of longitudinal waves in magnetostrictive phononic crystal beams

Abstract

Topological phononic crystals (PCs) have attracted increasing attention owing to their elastic wave topological transmission with high robustness, backscattering suppression, and defect immunity. However, the effective regulation of the topological interface state of elastic waves in multi-field environments remains a challenge, particularly in the magneto-mechanical-thermal coupling field. In this study, a magnetostrictive PC beam composed of Terfenol-D and aluminum rods was designed to dynamically manipulate the topological interface state of longitudinal waves when the system was subjected to magnetic, mechanical, and thermal loadings. First, the Zak phase transition of the band gap was induced by simply controlling the magnetic field distribution of a unit cell based on the nonlinear magneto-mechanical-thermal coupling constitutive characteristics of magnetostrictive materials. The frequency of the Zak point was also significantly affected by pre-stress and temperature. Subsequently, the controllable topological interface state of the longitudinal wave was successfully observed at the interface of magnetostrictive PC beams in a multi-field environment without altering the structure. The results showed that the frequency and location of the topological interface state could be dynamically tuned by magnetic, stress, and thermal loadings. The robustness of the topological interface state was also investigated. Finally, the magneto-mechanical-thermal coupling tunability of longitudinal-wave topological transport was experimentally verified for the proposed magnetostrictive PC systems. This study provides an effective method for the active modulation of elastic wave topological transmission and the development of novel tunable topological devices.