Electrical flow control devices are fundamental components in electrical appliances and computers; similarly, optical switches are essential in a number of communication, computation and quantum information-processing applications. An acoustic counterpart would use an acoustic (mechanical) signal to control the mechanical energy flow through a solid material. Although earlier research has demonstrated acoustic diodes or circulators, no acoustic switches with wide operational frequency ranges and controllability have been realized. Here we propose and demonstrate an acoustic switch based on a driven chain of spherical particles with a nonlinear contact force. We experimentally and numerically verify that this switching mechanism stems from a combination of nonlinearity and bandgap effects. We also realize the OR and AND acoustic logic elements by exploiting the nonlinear dynamical effects of the granular chain. We anticipate these results to enable the creation of novel acoustic devices for the control of mechanical energy flow in high-performance ultrasonic devices.
In the present work, we experimentally implement, numerically compute with, and theoretically analyze a configuration in the form of a single column woodpile periodic structure. Our main finding is that a Hertzian, locally resonant, woodpile lattice offers a test bed for the formation of genuinely traveling waves composed of a strongly localized solitary wave on top of a small amplitude oscillatory tail. This type of wave, called a nanopteron, is not only motivated theoretically and numerically, but is also visualized experimentally by means of a laser Doppler vibrometer. This system can also be useful for manipulating stress waves at will, for example, to achieve strong attenuation and modulation of high-amplitude impacts without relying on damping in the system.
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