Preventing railway vehicles from derailing is an important issue for the rail industry. Also important is minimizing the outcome of a derailment by formulating post-derailment measures to limit the extent to which railway vehicles deviate from the track. In this paper, two kinds of post-derailment devices are designed and then validated using derailment experiments performed in the laboratory. The derailment experiments are performed on a derailment test bench designed by the Traction Power State Key Laboratory. To design the\ post-derailment devices, a half-car derailment test without any post-derailment device is conducted to understand the dynamic behaviour after a derailment. Then devices that can be mounted under the axle box to limit the lateral displacement of the vehicle during the derailment are designed on the basis of the observed dynamic behaviour. A theoretical analysis is used to derive the relationship between the mounting position and the initial conditions of the derailment. Finally, the two devices, which have different mounting positions, were verified in derailment experiments. The verification results indicate that a device with a reasonable mounting position can limit the lateral displacement of the vehicle and reduce the consequences of a derailment. Also, in order to avoid the fastener area, the distance between the device and the wheel needs to be larger than 180 mm.

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This paper proposes a fast and stable iterative algorithm for wheel–rail contact geometry based on constraint equations, which can be implemented in dynamic wear simulations that real-time profile updating is needed. Further, critical factors that determine convergence and iteration stability are analyzed. A B-spline is adopted for wheel–rail profile modeling because it does not contribute to changes in the global shape of curves. It is found that the smoothness of the first and second derivative curves significantly affects the numerical stability of the Jacobian matrix, which determines the increments in iterations. Moreover, a damped Newton's iteration formula with a scaling factor of 0.5 is proposed considering the convergence rate and out-of-bound issues for the updated step. The influence of the initial iteration parameters on the convergence is studied using Newton fractals. The range within ±3 mm, centered on the target contact point, is found to be an unconditionally stable domain. The proposed method could achieve convergence within 10 and 30 steps under thread and flange contact conditions, respectively.