Effect of damper moment of inertia on the effective dynamic properties of railway tracks attached with dampers

Rail dampers are longitudinally installed along the track, leading to high moment of inertia effects in the high-frequency band. The metamaterial properties resulting from the periodic installation of rail dampers while considering the moment of inertia effect are investigated. This study analyzes the relationship between the effective dynamic characteristics and the track decay rate (TDR), as well as band gap properties. The wave propagation method was employed to predict the flexural vibration of the rail with periodically attached dampers. A comparison was made between the effective mass density with and without accounting for the damper’s moment of inertia effect. The wavenumber for the flexural vibration of the railway was determined for calculating the frequency-dependent TDR. The spectral element method and the Bloch’s theory were employed to predict the flexural wave propagation constants. The study investigated the band gap characteristics of an infinite damped track while considering the moment of inertia effect. The effective mass density exhibited significant variation near the bounce and pitch mode frequencies of the rail damper. When the real part of the effective mass density turned negative, the propagating wavenumber components vanished, and the attenuation of damped railway vibration become significant. A wide band gap phenomenon was identified due to the coupling effect of the bounce and pitch motion of the damper. Experiments were conducted to validate the effectiveness and band gap properties of periodic dampers in practice. The moment of inertia effect from rail dampers must be considered in the analysis of the vibration damping mechanism.