Monitoring of rail corrugation growth due to irregular wear on a railway metro curve

Artikel i vetenskaplig tidskrift, 2009

Short-pitch rail corrugation developing on the low rail in sharp curves is a problem experienced by many railway networks worldwide. Because of the large existence of small radius curves, metro lines are particularly affected. This case study is performed as part of a project which aims at developing a numerical tool for prediction of rail corrugation growth on curves. The development of corrugation on a 120 m radius curve of the Stockholm metro has been monitored by repeated measurements of rail roughness and train pass-by noise. Within a grinding interval of 1 year, severe short-pitch corrugation was build up with maximum peak-to-peak magnitudes of about 0.15 mm. Spectral analysis of measurement data shows large roughness magnitudes in the wavelength interval 4-14 cm, with peaks at approximately 5 cm and 8 cm. The corrugation pattern has a pure longitudinal direction (with corrugation ridges transverse to the track direction) and an irregularly varying magnitude along the 100 m long measured track section. The roughness growth rate increased with time until 300 days after rail grinding, thereafter only moderate additional roughness growth was observed. Because of moderate train speeds of about 30 km/h, the rolling noise caused by the corrugation has a low-frequency content (< 200 Hz). A 10.1 dB unit increase (139-300 days after grinding) in roughness level in the wavelength interval 4-14 cm was found to correspond to an increase in rolling noise level in the frequency interval 60-200 Hz of 4.9 dB. In dry weather conditions, discomfort related to pass-by noise is rather linked to the occurrence of wheel squealing than to rolling noise.