  One dimentional strongly nonlinear phononic crystals were assembled from
chains of PTFE (polytetrafluoroethylene) and stainless steel spheres with
gauges installed inside the beads. Trains of strongly nonlinear solitary waves
were excited by an impact. A significant modification of the signal shape and
an increase of solitary wave speed up to two times (at the same amplitude of
dynamic contact force)were achieved through a noncontact magnetically induced
precompression of the chains. Data for PTFE based chains are presented for the
first time and data for stainless steel based chains were extended into a
smaller range of amplitudes by more than one order of magnitude than previously
reported. Experimental results were found to be in reasonable agreement with
the long wave approximation and with numerical calculations based on Hertz
interaction law for discrete chains.
