An investigation into the effect of frequency- and amplitude-dependent stiffness of railpads on the vehicle-track dynamics of high-speed railways

Rail fasteners play a crucial role in high-speed railway tracks as they provide the primary elastic properties necessary for the track’s functionality. Accurately characterizing these fasteners is vital for dynamic analyses that assess wear, fatigue, and reliability during track-vehicle interactions. The railpads exhibit highly nonlinear mechanical characteristics, which traditional spring-damping models fail to accurately depict. To address this inadequacy, this study introduces a dynamic fastener model sensitive to both frequency and amplitude variations. This model incorporates fractional derivative calculations to capture the viscoelastic forces accurately and utilizes the Berg friction model for assessing frictional forces. The paper starts with a theoretical analysis of the dynamic properties of the proposed model, followed by its integration into various dynamic systems. The findings reveal that unlike conventional models, the stiffness in this model increases with rising excitation frequency and decreases with higher excitation amplitudes, showing high conformity with actual situations. The dynamical characteristics of this model were further clarified through weld excitation in a coupled vehicle-track system. Additionally, under random irregularity excitation, this fastener model shows superior performance in simulations related to driving safety, predicting fastener damage, and enhancing forecasts of passenger comfort.