Enhanced wave absorption due to local flexibility on wide beams using mass-spring-damper scatterersa)

It is known that total absorption of flexural waves in a thin beam is possible through the use of monopole-dipole scatterers. In this study, we introduce a pair of identical monopole scatterers for near-total absorption of flexural waves in a thin and wide beam. Despite the two scatterers being both of the monopole type, the resonant modes of the scatterer pair exhibit monopole and dipole properties. By selecting the proper width for the beam, the two resonant modes degenerate, which leads to the total absorption. Although the beam is considerably wide, the frequency range of interest remains below the cut-on frequency of the n = 1 propagating mode, ensuring one-dimensional flexural wave propagation. Further simulations and theoretical analysis revealed that the degeneracy of the monopole and dipole modes results from their interaction with a higher-order localized flexural mode. The simulation results demonstrate absorption exceeding 99%, complemented by experimental data showing approximately 90% absorption.