Wave-resistance sleeper with locally resonant phononic crystals: Bandgap property and vibration reduction mechanism

As an artificially engineered metamaterial, locally resonant phononic crystals (LRPCs) exhibit great potential for the vibration reduction of urban rail transit due to their capability to prohibit the propagation of elastic waves with long wavelengths. This study proposes a wave-resistance sleeper with negative dynamic mass density by periodically embedding LRPCs into the concrete sleeper and provides new approaches to improve its bandgap property. Furthermore, the vibration reduction effect of the wave-resistance sleeper applied in a slab track was evaluated with a three-dimensional half-track model. The results show that the wave-resistance sleeper has two bandgaps below the frequency of 2000 Hz and can effectively prohibit the vibration within the bandwidth from transmitting to the track bed. Setting intervals in the rubber coating and increasing the void fraction can significantly reduce boundary frequencies of the first bandgap, whereas the second bandgap attenuates completely as the vibration can no longer be localized in the discontinuous rubber coating. A larger metal core is beneficial for obtaining a wider bandgap in the low-frequency range, whereas a thicker rubber coating can be used to obtain a wider bandgap in the medium-frequency range. To obtain wider bandgaps, the steel tube used should be as thin as possible and the use of an oval metal core should be avoided. It is hoped that the research results can provide a useful reference for the vibration reduction of track in rail transit.