Simulation analyses of progress process of rail corrugation

Abstract

Rail corrugation is such phenomenon that roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and cause the vibration and the noise. In the previous papers of ours, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and verified their validity by comparing them with the field data. In this paper, we report the results of simulation analyses of the characteristics of each step of formation, growth and saturation of the rail corrugation using a discrete elastic support model close to the actual track. As a result of the simulation, the following are confirmed : (1) at the formation step, by providing a minute and irregular wheel load fluctuation, rail surface roughnesses are formed with such wavelengths that their amplification factor of roughness amplitude is maximal and greater than 1.0. (2) at the growth step, as the contact length of the wheel / rail becomes longer, growth of roughness of the short wavelength is suppressed. (3) at the saturation step, when the roughness amplitude increases and the wheel loses the contact with the rail, the growth is suppressed and the roughness amplitude saturates. Based on these results, we present the progress process of the rail corrugation and the ways to approach the countermeasures.

<b>Method for Evaluating Rail Corrugation Growth Process by Monitoring Vertical Rail Vibration</b>

“…In the "saturation stage," the wheels of a vehicle can no longer follow rails because of growing roughness and are repeatedly in and out of contact with the rails, resulting in the roughness waveform transforming from sinusoidal to triangular. Simulations confirm that this results in components, that are integral multiples of basic spatial frequency (harmonic components), appearing in the spatial frequency components of the roughness waveform [6], and harmonic components appear in the response of tracks and vehicles [8]. Thus, it is believed that collisions between wheels and rails at the saturation stage result in the actualization of the noise and vibration posing problems during actual operation.…”

“…11 (a), there is a tendency for power to increase in each frequency band from approximately 7 million tons after rail grinding at measurement point A, and the power of the fundamental frequency band (115-Hz band) increases ahead of the second harmonic band (230-Hz band). Here, based on the characteristics of the "saturation stage" according to numerical analysis [8], increased power in the fundamental frequency band in the vertical rail vibration is attributable to increased amplitude in the "growth stage," and increased power in the second harmonic band is attributable to the collision of the rail and wheels when transitioning to the "saturation stage. "…”