Maoru Chi

The study of post-derailment measures to limit the extent of a derailment

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.

Post-derailment dynamic behavior of railway vehicles travelling on a railway bridge during an earthquake

This study developed a post-derailment dynamic model of railway vehicles to investigate their post-derailment dynamic behavior when travelling on a railway bridge during an earthquake. The model is composed of three parts: multi-body dynamic model of the railway vehicle, a collision detection model, and a contact force model. The dynamic model considered all the various kinds of contacts that may occur during the derailment, such as wheel/track slab contacts, wheel/fastener contacts, and brake-disc/rail contacts. A collision detection model that was based on the tight-fitting oriented bounding box trees approach was adopted to detect the collision situations during the derailment. The contact force model was used to calculate the contact force based on a Hertz spring-damper and the Coulomb friction law. Using this model, the post-derailment dynamic behavior of railway vehicles travelling on a railway bridge experiencing earthquake excitations was investigated. First, a seismic response analysis of the railway bridge was conducted in order to obtain the seismic response of the railway bridge; it was subsequently used as the input to the post-derailment dynamic model. Then the derailment postures of the vehicle and contact situations were fully analyzed to understand the post-derailment dynamic behavior of railway vehicles during the earthquake. The obtained results show that the brake disc adopted in the model has the ability to limit the deviation of the wheelsets after the derailment.