Dynamic characteristics and growth curve of rail corrugation at saturation stage

Abstract

Rail corrugation, which causes the vibration and the noise, is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running. In the previous paper, we have already explained the growth mechanism and the wavelength determination mechanism of the rail corrugation from the dynamic point of view and that there are three stages in the evolution process of the corrugation: formation, growth and saturation. In this paper, we analyze the dynamic characteristics of the track and vehicle in the saturation stage, propose a growth curve of corrugation, and verify them based on measured data obtained on commercial lines. As a result, it is confirmed that when the roughness amplitude grows and exceeds the critical roughness amplitude, there are two characteristics: the significant increase of the contact force fluctuation and the acceleration of the rail and wheel, formation of higher-order roughness components of the corrugation. The growth curve of the corrugation can be approximated by a logistic function.

<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.…”

“…However, we found that when about 14.03 million tons passed after rail grinding and rail corrugation amplitude reached about 0.2 mm, a dominant spatial frequency component (① in the figure) was recognized, and rail corrugation of about spatial frequency 10 [1/m] (wavelength 100 mm) was being generated. In addition, the dominant spatial frequency component near 20 [1/m] in this section (② in the figure) is approximately two times the aforementioned basic spatial frequency of rail corrugation and is believed to be a harmonic appearing at the saturation stage of corrugation [6]. On the other hand, we see that in the section of direct fastened track with anti-vibration sleeper including measurement point B, the component of spatial frequency 18 [1/m] (wavelength 55 mm) increased slightly as the passing tonnage increased after rail grinding (③ in the figure).…”

“…Figure 2 shows a model of the growth process of rail corrugation proposed by the authors [6]. The growth process of rail corrugation has three stages -the "formation stage," "growth stage" and "saturation stage" -and the increasing tendency of rail corrugation amplitude can be modeled with a growth curve.…”

“…Based on the above, vertical rail vibration monitoring is effective in evaluating growth process based upon the characteristics of the "saturation stage" of rail corrugation [6].…”

“…Many studies and research [1-4 for example] have attempted to identify the mechanism underlying rail corrugation from a variety of viewpoints, but none have been fully successful, so no basic measures against rail corrugation have yet been proposed. The authors of this paper posit however, that it is possible to model the increasing tendency in the amplitude of rail corrugation on a growth curve from the results of regular measurements of rail corrugation on commercial lines [5] and dynamic simulation accounting for track/ vehicle interaction [6]. In addition, we believe that the noise and vibrations that pose problems during actual operation actualize during the final "saturation stage" of the growth process.…”