A novel sandwich meta-structure pipe and its mechanism of ultra-low frequency broadband vibration bandgap

Abstract Addressing the challenge of achieving flexural vibration control in the ultra-low frequency range 0 to 15 Hz with conventional meta-structure pipes requires a new design. A sandwich meta-structure pipe is introduced that integrates lightweight, high stiffness, with an ultra-low-frequency broadband vibration bandgap. Numerical simulations and experimental investigations were conducted to examine the bandgap and vibration transmission properties. The proposed sandwich meta-structure pipe exhibits a bandgap opening frequency of 6.7 Hz. The design lowers the bandgap opening frequency by 91% and increases the bandgap width by 84.3% compared with conventional meta-structure pipes. According to the bandgap formation mechanism, the novel oscillator simultaneously increases the dynamic equivalent mass. It reduces the dynamic equivalent stiffness, without altering the actual mass or stiffness of the structure or applying external loads or pre-displacements, thereby enabling the formation of an ultra-low-frequency bandgap. The dual suppression forces resulting from the symmetrical arrangement of the novel oscillators are key to broadening the bandgap. Furthermore, by adjusting structural parameters of the oscillator, desired bandgap characteristics and vibration transmission performance can be achieved. The proposed sandwich meta-structure pipe offers a novel approach to controlling ultra-low-frequency vibrations in pipeline structures.