Abstract Summary
Short pitch corrugation (hereinafter corrugation) is one of the major rail defects in railway tracks worldwide. It is recognized as a (quasi-) periodic undulation of the rail surface with shiny crests and dark valleys. Corrugation excites high-frequency wheel-rail dynamic forces, induces strong vibration and noise, and accelerates the degradation of railway components, which significantly increase the maintenance cost. Despite extensive theoretical and experimental research in recent decades, corrugation development mechanism remains unclear. This work proposes an integrated approach to identify the corrugation formation process, including field observation and measurement, numerical simulation employing a three-dimensional (3D) finite element model (FEM), and experimental validation using an innovative downscale V-Track test rig The field observation and measurement show that corrugation wavelength falls typically in the range of 20-80 mm and insensitive to trains speed variation. Corrugation can develop in the embedded rail system with continuous support where the pinned-pinned resonance is absent. Corrugation with visible initial excitation (e.g., rail joints, squats) usually decay after several waves, while corrugation with invisible excitation often occurs with a much longer distance. This work focuses on the latter corrugation. To investigate the corrugation formation mechanism, a 3D FE vehicle-track interaction model is employed which can simultaneously consider the contact mechanics and structural dynamics, as well as their interplay. The rail damage mechanism is assumed as wear. The simulation results indicate that with nominal track parameters, corrugation cannot initiate, and a predefined corrugation will also be erased by the wheel-rail dynamic interaction. However, by introducing an initial excitation to the vehicle-track system from the degraded fastenings, corrugation can initiate and consistently grow up to 80 um. The reproduced corrugation agrees with the field observation in terms of the wavelength and periodicity. Further analysis shows that longitudinal compression modes are responsible for corrugation initiation, and the consistency between the longitudinal compression and vertical bending eigenfrequencies of the wheel-track system is required for consistent corrugation growth. To validate the FEM simulation results, we perform the corrugation experiment using the V-Track test rig. Compared to other testing facilities, the V-Track can comprehensively simulate both the wheel-rail contact and the high-frequency dynamics of the real vehicle-track system. During the corrugation experiment, the fastening clips are loosened at certain locations of the ring track to simulate fastening degradation and introduce dynamic effects to the vehicle-track system for corrugation initiation. Overall, the FEM simulation and the V-Track experiment both highlight the significance of rail longitudinal vibration modes on corrugation formation.
