Correlating track forces and track profile

Abstract

Wheel/rail dynamic forces are dependent upon the characteristics of both train and track, and lead to time-dependent degradation of the track. The quality of maintenance of both train and track affect the amplitude of these forces and therefore the rate of degradation of track. These relationships are being studied at Queensland University of Technology via a Rail CRC project, using test track and test vehicles provided by QR. A central part of the study is attempting to relate wheel/rail forces to the longitudinal vertical profile of the track; the profile is measured by QR’s Track Recording Car (TRC) and their Corrugation Analysis Trolley (CAT). However, because doing detailed measurements of the longitudinal profile frequently over the study period is impractical, the authors developed an innovative algorithm that converts track recording car (TRC) rail top offset measurements into suitably accurate longitudinal profiles. The study takes those profiles and correlates them against the vertical wheel-rail forces measured by the test vehicle. But those forces are comprised of many continuously varying frequencies and amplitudes and the track profile varies significantly in position and time, making correlations between them quite complex. The authors have therefore drawn on signal processing principles that convert data into power spectral density plots and then apply a function known as coherence. The study has found that at low frequencies, there is very strong correlation between forces and track profile, as would be expected. However, there is diminishing correlation as frequencies increase. This has implications for relating bogie characteristics to track degradation.