Attenuation of impact waves in a nonlinear acoustic metamaterial beam

Wave propagation in nonlinear acoustic metamaterials (NAMs) has attracted broad attention. While showing the possibility of achieving low-frequency and broadband vibration suppression, most existing work focuses on harmonic waves. In this paper, we study the impact wave propagation and its mitigation in a nonlinear metamaterial beam. Thorough numerical analyses show that strongly nonlinear acoustic metamaterials can entail effective attenuation of impact waves in an infinite structure and the impact vibration in a finite structure with a much higher efficiency than what can be achieved in their linear counterparts. The attenuation properties, underlying mechanisms and the influence of key system parameters are clarified. Results show that the observed attenuation is dominated by the nonlinearity-induced self-broadening of the bandgaps whose bandwidths adaptively expand with the propagation distance/time, as a result of the amplitude-dependent nature of the band gaps in a NAM. In a finite NAM structure, significant attenuation of the impact vibration can be achieved, outperforming the corresponding linear cases. These findings shed lights on new physics relating to NAMs and might inspire their further study and application.