Rail corrugation growth on small radius curves-Measurements and validation of a numerical prediction model

The development of low rail corrugation (rutting corrugation) on a 120 m radius curve on the Stockholm metro is studied by field measurements, laboratory measurements and numerical simulations. The corrugation develops exclusively on the low rail with wavelengths of about 5 cm and 8 cm. It is concluded by field measurements that the application of friction modification effectively mitigates the corrugation growth on the curve. For the low rail, high levels of lateral acceleration and plastic material flow in the surface layer orientated towards the field side indicate large magnitude lateral creep forces generated by the curving vehicles. A time-domain model for prediction of roughness growth on small radius curves is applied to obtain an improved understanding of the wheel-rail interaction leading to rutting corrugation. The model is validated by comparison of predicted long-term rail roughness growth against measured data, and it is concluded that the corrugation is generated by the low rail contact of the leading wheelset of passing bogies. The corrugation wavelengths observed on the curve are related to excitation of the first symmetric and first antisymmetric bending eigenmodes of the leading wheelsets. Important parameters for the identified wavelength-fixing mechanisms are investigated.