No abstract

To consider the rail pads of thermoplastic polyurethane elastomer (TPE), chloroprene rubber (CR), and ethylene propylene diene monomer (EPDM) that are usually used in the Chinese subway as test subjects, their static stiffness at temperatures of À40 C to 70 C was measured by a universal testing machine equipped with a temperature control box. Then, the influence of the temperature-dependent stiffness of the rail pads on the vertical vehicle-track coupled vibrations was investigated with application of a vehicle-track coupled dynamic model. It was found that the static stiffness of these rail pads exhibits a nonlinear variation with temperature. Their static stiffness is considerably sensitive to temperatures below 20 C, when the CR rail pad is the most sensitive. At temperatures above 20 C, their static stiffness slightly alters with increasing temperature. The temperature-dependent stiffness of these rail pads mainly affects the vertical vibrations of the vehicle system above the one-third octave center frequency of 31.5 Hz and the vertical rail vibrations near the center frequency of 63 Hz. Moreover, the influence of the low-temperature stiffness of rail pads at À40 C to 20 C is far greater than the effect of the high-temperature stiffness of rail pads at 20-70 C. Thus, TPE, CR, and EPDM rail pads have excellent high-temperature stability and adverse low-temperature sensibility.