Wave attenuation and tunability of a diatomic metamaterial

The exposition level of the built environment to seismic wave propagation underscores the critical need for advanced strategies to mitigate structural damage and life-threatening conditions during earthquake events. To reduce seismic wave impact, metamaterials have unveiled promising wave attenuation performance due to their design, adaptability, and effectiveness. While numerical studies have demonstrated the effectiveness of metamaterials in attenuating different frequency excitations (including earthquake excitations), experimental evidence to corroborate wave attenuation predictions and tunable mechanisms for low-frequency waves remains limited. This research presents the evaluation of wave attenuation in a mass-and-mass metamaterial under low-frequency excitations, incorporating a tunable mechanism based on the engagement of electromagnets. The mass-and-mass metamaterial consists of a one-dimensional diatomic chain, where varying engagements of electromagnets can modify the wave attenuation effect for different tunability purposes. The dispersive behavior and frequency bandgap of the metamaterial are derived for theoretical wave attenuation. In an analytical study, the predicted wave attenuation is examined through the time-history responses and frequency response functions of analytical metamaterial models according to different engagements of electromagnets. Then, an experimental study testing a small-scale metamaterial specimen is conducted to corroborate the wave attenuation effect and its tunability in the analytical results. The results demonstrate that intentional structural modifications via the engagement of electromagnets enable adaptive solutions over wave propagation characteristics. This investigation also contributes to the development of reconfigurable metamaterials for vibration mitigation in different wave propagation problems. Consequently, new pathways for tunable and efficient wave attenuation can be envisioned in large-scale applications, including earthquake engineering.