Nonlinear effects of a new mesh-type rail pad on the coupled vehicle-slab track dynamics system under extremely cold environment

Nonlinear dynamic behavior of a new mesh-type rail pad on the vehicle-slab track coupled system is investigated considering the influences of frequency and amplitude dependence in extremely cold environment. The frequency dependence of the new mesh-type rail pad is modeled by a fractional derivative viscoelastic element while a frictional component considers the amplitude dependence. Laboratory tests are performed to investigate the frequency and amplitude dependent performance of the rail pad and to determine key model parameters. Temperature factor and Mooney-Rivlin strain energy density are also introduced to simulate the mechanical properties of the rubber material of rail pad in low temperature environments. Further, the proposed nonlinear model for the rail pad is implemented in a coupled vehicle-slab track dynamics model to investigate the complicated nonlinear effects of the rail pad due to the dependence of the temperature, amplitude and frequency. The analysis indicates that the dynamic stiffness and damping of the mesh-type rail pads increase with the frequency increases. The proposed model for the mesh-type rail pad enables a more accurate dynamic simulation of vehicle-slab track system in extremely cold environment than the traditional Kelvin-Voigt model which overestimates the wheel rail force, rail vibration acceleration and other indicators at 3.15 Hz–40 Hz and 250 Hz–500 Hz, while underestimates these indicators at 50 Hz–125 Hz.