Wave propagation in periodic track structures: band-gap behaviours and formation mechanisms

Abstract

This paper presents the results of a study concerning the band-gap behaviours and formation mechanisms of periodic track structures. Based on the band-gap theories introduced from phononic crystal which concentrates on the elastic wave propagation in periodic structures, the railway track can be regarded as a novel locally resonant phononic crystal. The band-gaps are found by using the transfer matrix method combined with Bloch theorem, and the attenuation factors in band-gaps are also obtained firstly. Then, band-gap behaviours of periodic track structures are investigated with various parameters such as stiffness of rail pad, fastening spacing and thermal force in rail. Bounding frequencies and width of band-gaps are closely related to the parameters of track structures, resulting from the various wave motion modes at the bounding frequencies. Moreover, it has been found that Bragg band-gaps and locally resonance band-gaps coexist in periodic track structures. And formation mechanisms of band-gaps in periodic track structures can be explained by the Bragg scattering mechanism and locally resonance mechanism. The theoretical analysis is verified by the frequency response functions calculated through the finite element models at last.