Enhanced vibration suppression using diatomic acoustic metamaterial with negative stiffness mechanism

This paper presents a diatomic-chain locally resonant acoustic metamaterial (LRAM) structure with negative-stiffness mechanism for enhanced suppression of vibration transmission. The bandgap properties of the diatomic configuration were studied and shown to enhance performance benefits by introducing two extra bandgaps that exploit Bragg scattering, located on both sides of the local resonant bandgap. The upper band-folding-induced bandgap exhibits better performance than the lower band-folding-induced bandgap. Converting a monoatomic configuration into a diatomic configuration is shown to be beneficial. A dispersion relation analysis is performed and new phenomena are revealed from the viewpoint of the vibration power flow and wave transmittance, demonstrating the potential application of negative stiffness for performance improvement. A geometrical nonlinear mechanism is studied, and the results demonstrate the possibility of providing a constant negative stiffness under specific material parameters. With the application of this negative-stiffness mechanism for the critical, effective stiffness value, the locally resonant bandgap of the metamaterial configuration shifted toward the lower frequency range, effective from zero frequency, thus achieving ultralow frequency vibration control. The proposed implementation of the negative-stiffness mechanism in a diatomic metamaterial structure is shown to yield desirable bandgap properties, providing potential benefits for vibration suppression.