Search

The damage of a Hadfield steel crossing in a railway turnout due to wheel rolling impact passages is investigated numerically. A three dimensional elastic–plastic finite element model has been developed by taking into account non-linear material properties, dynamic wheel impact and wheel–crossing contact. The effects of wheel velocity on the damage and deformation of the crossing is analysed. In the present study, four rolling velocities of the wheel, i.e., 50 km/h, 100 km/h, 150 km/h, and 200 km/h were chosen. The wheel exhibits elastic material behaviour, whereas the crossing exhibits elastic–plastic material behaviour. To represent the damage and deformation behaviours of the crossing, non-linear dynamic work hardening is further included in the calculation. Dynamic stress and strain in the crossing were obtained by the explicit finite element method, including the maximum von Mises stress, the maximum strain, the maximum horizontal stress, perpendicular stress and parallel stress. The snake-like motion of the wheel rolling on the crossing was verified by the simulation; in the meantime, there is a significant impact load on the nose rail, which caused a big von Mises stress in the nose rail. The big von Mises stress is the main reason for the nose rail fatigue spalling. The maximum von Mises stress and maximum strain in the nose rail increase with the train speed increasing. The study provides a method for the further research on the fatigue and the wear behaviours of railway crossings.

An open-ended dielectric resonator method and experimental apparatus for measuring microwave surface resistance of the high Tc superconducting thin films are reported. Making use of two sapphire rods the quality factor related to the losses of the resonator except its superconducting part can be evaluated. The Rs value of an individual superconducting thin film can be determined without any assistance of other superconducting films or calibrators. This measurement provides a convenient and absolute approach for Rs-measurement of high Tc superconducting thin films. Also the error in the Rs-measurement with the method was discussed.