Theoretical analyses of growth mechanism of rail corrugation

Abstract

Rail corrugation is a phenomenon in which roughness patterns of approximately regular wavelengths are formed on the rail running surface by trains running, and causes the vibration and the noise. Therefore, in this paper, we analyze the amplification factor of roughness amplitude using a model that takes into consideration the interaction between the track and the vehicle, and clarify the growth mechanism and the wavelength determination mechanism of the rail corrugation. As a result of the theoretical analyses, it is indicated that the essential factors of growth of the corrugation are (1) interference of rail wave motion between the front and the rear wheels of a bogie of the vehicle, (2) anti-resonance phenomenon of the elastic support of the track system, (3) anti-resonance phenomenon of the total system of the track and the vehicle, and (4) anti-resonance phenomenon of the vehicle system. In addition, as a result of examing the rail corrugation measured on the commercial lines, it is confirmed that the causes of the corrugation occurrence are the above mentioned (1),(2) and (3) factors, and that the measured wavelengths almost agree with the theoretical values.

<b>Growth Mechanism and Evolution Process of Rail Corrugation</b>

“…It is possible to measure the rail surface roughness continuously and accurately independently of travel speed of the trolley. Figure 13 shows a measured example of rail corrugation [5]. STFT means a short time Fourier transform, and is modified according to the diminishing multiplication rule of 10 -3 .…”

“…The motion equations of the vehicle are expressed in (5), where y a～d , M a～d , K a～c and D a～c are displacement, mass, spring constant and damping coefficient of each part of the vehicle.…”

“…7 corresponds to about 20 Hz. At this frequency, the track and the vehicle are equal in the absolute values of the mechanical impedances, and the series mechanical impedance of the track and the vehicle reach a maximum [5]. This maximum is considered to be an anti-resonance phenomenon where a large force is required to achieve forcible displacement between the rail and the wheelsets.…”

“…Therefore, the cause of this corrugation can be identified as the interference of the rail wave motion with the wheelbase of the vehicle. Figure 15 shows another example of rail corrugation [5]. Corrugation occurs when the train speed is in the 20～60 km/h range, and spatial frequency is 10～30 (1/m): the spatial frequency tends to be inversely proportional to train speed.…”

“…Finally, this paper proposes possible approaches for developing countermeasures. Figure 2 shows the theoretical analysis model [5]. The track system is modeled as an elastically supported beam, and the vehicle as a mass-spring system moving at speed v. The elastic support models of the track are shown in Fig.…”