Investigation on tunable low-frequency property of magnetic field induced phononic crystal with Archimedean spiral-beams

Phononic crystal is a type of periodic artificial structure in which the elastic waves can be controlled. However, the immutable dynamic characteristics of fabricated phononic crystals restrict their applications. Therefore, a phononic crystal with tunable ultra-low frequency bandgap, which was controlled by magnetic field, was proposed to overcome this disadvantage. The proposed phononic crystal consisted of a frame, two spiral beams, and two electromagnets. The phononic crystal was fabricated using 3D-printing technology. The electromagnets were embedded in the spiral beams. An ultra-low frequency bandgap of lower than 20 Hz was obtained. In addition, the ultra-low frequency bandgap was tuned by switching the magnetic field. The bandgap was adjusted by changing the geometrical parameters of the spiral beams, which enhanced the design flexibility. Theoretical calculations and finite element simulations were conducted, and the results were experimentally verified. The proposed tunable phononic crystal can be used in the field of vibration suppression in ultra-low frequency range for infrasound-control requirements.