Vibration transmission and damping characteristics of double-layer non-linear fasteners

As a widely used fastening type in urban rail transit, a fastening system equipped with a double-layer non-linear rubber pad largely compensates for the insufficient elasticity of ballastless track systems. Studying the vibration transmission characteristics within double-layer non-linear fasteners is a prerequisite for understanding their damping mechanisms and optimising their efficiency. Based on preliminary investigations of the vibration transmission characteristics between fastener layers using hammer tests, a refined dynamic finite-element model was established and validated. The distribution and attenuation of wheel–rail dynamic responses in each layer of the system were analysed. It was found that vibration is gradually attenuated from the rail downwards, with high-frequency vibrations exhibiting more significant attenuation. The middle rubber pad exhibits stronger vibration-damping capability than the under-rail rubber pad, especially for medium- and low-frequency vibrations. To a certain extent, it compensates for the inadequate vibration-damping performance of the overall fastener system in the low-frequency range. The coordinated use of the two rubber pads endows the double-layer non-linear fastener with layered and progressive vibration-damping characteristics. Reasonable matching of the stiffness of the two rubber pads can selectively attenuate wheel–rail dynamic responses in different frequency bands, thereby achieving optimised vibration-damping performance.