Input-independent frequency conversion through transition waves in bistable metabeams

In this study, the input-independence characteristics of bistable lattices are extended to architectures exhibiting dynamics in two different size scales: the microscale excitation in the unit cell level and the macroscale response in the structural level. To that end, a metabeam is designed to allow vertical deflections augmenting a one-dimensional spring-joined bistable lattice. The metabeam is harmonically excited in the in-plane direction on the unit cell, and the out-of-plane motion is measured on the macroscopic structure. We construct a nonlinear frequency response diagram showing the contribution of available output frequencies for each input excitation. As long as transition waves propagate within the metastructure, the most dominant output frequency occurs near the natural frequency of the macroscale structure, which is independent of the input frequency. The studied metabeam shows a strong potential for energy transfer between two different size scales and uncorrelated frequencies (both low-to-high and high-to-low). Furthermore, we show that the triggering frequency range and the output frequency can be easily tuned by manipulating the unit cell and macroscopic frame designs, respectively.