Study on corrugation distribution in metro ramps of curved tracks based on wheel-rail stick-slip characteristics

It is found that the distribution of corrugation of curved tracks is influenced by ramps: uphill sections have significant corrugation in high rail; downhill sections have more severe corrugation in low rail. To clarify this phenomenon, a vehicle-track rigid-flexible coupling model is developed from the perspective of stick-slip theory to calculate the saturation rate and the overall dispersion rate of adhesion coefficient; a wheel-rail coupling finite element model is developed to perform modal analysis for determining the wavelength fixation condition of ramp corrugation. The results show that: the adhesion coefficient of high rail is close to saturation while that of low rail is small in uphill sections, so high rail is more prone to stick-slip motion further developing into corrugation; the adhesion coefficients of low rail and high rail in downhill sections are close to saturation, so both of them are susceptible to stick-slip motion, and repeated so will induce uneven wear and under the influence of rail irregularity, stick-slip vibration intensity of low rail is more severe and corrugation develops more rapidly. Wheel-rail coupling vibration modes in the range of characteristic frequency of corrugation may provide wavelength fixation condition for the development of corrugation. The parameter analysis shows that: a large uphill gradient will further increase the probability of stick-slip motion in high rail, and a large downhill gradient will sharply increase the probability of stick-slip motion but slow down the rate of development of corrugation in low rail, which, however, will still rapid than that of high rail. For the field study line, slow application of braking/traction force is favorable for ramp corrugation control. The vertical stiffness of fasteners of 40 MN/m is detrimental to corrugation control. The high vertical damping of fasteners has a weak effect on corrugation suppression. Proper deficient super-elevation can alleviate corrugation.