Passive-adaptive mechanical wave manipulation using nonlinear metamaterial plates

Abstract

In many controlled acoustics applications, it is desirable to engineer passive-adaptive manipulation of mechanical waves through waveguides based solely on varying dynamic input. We investigate the potential of achieving this using experiments on several types of nonlinear acoustic metamaterial plates. By tuning the amplitude-dependent response of locally resonant attachments and tailoring their patterning on or within a host plate-type medium, amplitude-activated shifts in bandgap frequency ranges could be utilized to tailor the direction and bandwidth of wave propagation through such metamaterials. Prototype test articles for passive-adaptive wave rejection, steering, sorting and selective beaming were constructed and tested using customized rigs. The location, extent and shift of bandgaps were experimentally and numerically verified. Scalable waveguide designs are experimentally evaluated for low (150–250 Hz) and much higher (16–20 kHz) frequency ranges. The potential to steer and sort waves in a tunable frequency range toward specific regions or paths within the waveguide is demonstrated. With current precision and hybrid fabrication techniques attaining commercial maturity, metamaterials-based approaches offer great promise in realizing waveguides with built-in, adaptive functionalities related to filtering, transduction and actuation for mechanical waves.