Bandgap mechanism and vibration reduction property of wave-resistance sleeper with negative effective mass density

Based on the capability of controlling low-frequency elastic waves in solids with subwavelength size, locally resonant phononic crystals have potential applications in track vibration reduction. By periodically embedding 3D locally resonant unit cells (LRUCs) in a concrete matrix, a wave-resistance sleeper with a negative effective mass density is proposed, and the generation mechanism of the bandgap and parameter sensitivity are studied. Furthermore, the vibration mitigation performance of the wave-resistance sleeper applied to the ballastless track is analyzed. The results show that the local resonance of the LRUC results in negative responses in the wave-resistance sleeper to the vibration excitation, and a bandgap is generated in this frequency range. By changing the elastic modulus of the coating or the core density, the boundary frequencies of the bandgap of the wave-resistance sleeper can be effectively adjusted, and the bandwidth can be expanded by increasing the ratio of core radius to coating thickness, or by increasing the filling fraction, and adopting a thinner steel spherical shell. The bandgap of the wave-resistance sleeper was verified by test results. Based on the local resonance mechanism, the wave-resistance sleeper can effectively prohibit vibrations at multiple design frequencies from transmitting to the track bed.