One-dimensional nonlinear crystals have been assembled from periodic diatomic chains of stainless steel cylinders alternated with Polytetrafluoroethylene spheres. This system allows dramatic changes of behavior (from linear to strongly nonlinear) by the application of compressive forces practically without changes to the geometry of the system. The relevance of classical acoustic band-gap, characteristic for a chain with linear interaction forces and derived from the dispersion relation of the linearized system, on the transformation of single and multiple pulses in linear, nonlinear and strongly nonlinear regimes is investigated with numerical calculations and experiments. The limiting frequencies of the acoustic band-gap for the investigated system with a constant precompression force are within the audible frequency range (20-20,000 Hz) and can be tuned by varying the particle's material properties, mass and initial compression. In the linear elastic chain the presence of the acoustic band-gap was apparent through a fast transformation of incoming pulses within very short distances from the end of the chain. It is interesting that pulses with relatively large amplitude (nonlinear elastic chain) exhibit qualitatively similar behavior indicating the relevance of the acoustic band gap also for the transformation of nonlinear signals. The effects of an in situ band-gap created by a mean dynamic compression are observed in the strongly nonlinear wave regime.

Abstract. Attenuation of short, strongly nonlinear stress pulses in chains of spheres and cylinders was investigated experimentally and numerically for two ratios of their masses keeping their contacts identical. The chain with mass ratio 0.98 supports solitary waves and another one (with mass ratio 0.55) supports nonstationary pulses which preserve their identity only on relatively short distances, but attenuate on longer distances because of radiation of small amplitude tails generated by oscillating small mass particles. Pulse attenuation in experiments in the chain with mass ratio 0.55 was faster at the same number of the particles from the entrance than in the chain with mass ratio 0.98. It is in quantitative agreement with results of numerical calculations with effective damping coefficient 6 kg/s. This level of damping was critical for eliminating the gap openings between particles in the system with mass ratio 0.55 present at lower or no damping. However with increase of dissipation numerical results show that the chain with mass ratio 0.98 provides faster attenuation than chain with mass ratio 0.55 due to the 2 fact that the former system supports the narrower pulse with the larger difference between velocities of neighboring particles. The investigated chains demonstrated different wave structure at zero dissipation and at intermediate damping coefficients and the similar behavior at large damping.

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