Development of high-speed railway vehicle derailment simulation – Part II: Exploring the derailment mechanism

Based on the exactly solution for the wheel/rail contact point and the contact force, a vehicle/rail coupling model for analyzing dynamic derailment is developed in MATLAB as DDSHV (Dynamic Derailment Simulation for High-speed Vehicle). The calculation process of the simulation system is presented in detail, and the best solution conditions are also discussed to quickly obtain results. Two common types of dynamic derailment are studied in DDSHV. There exists a critical point in the process of wheel climb, and the dynamic weakening effect will promote the wheel-climbing rail. Meanwhile, some main factors, such as the speed, the rail condition and the wheel unload rate, have been studied on the dynamic weakening effect. The collision speed of the wheelset is the most important factor affecting impact derailment. As time becomes shorter, the collision can be investigated using LS-DYNA. The results confirm the equation for the critical impact speed used in this paper. DDSHV can also be used to find the vehicle running stability. Through the design of uplink and downlink algorithms, two critical running speeds, the critical speed and the nonlinear critical speed have been found. Yet, the changes in suspension parameters will directly influence these critical speeds. Therefore, an accurate configuration in vehicle will help to reduce the disturbances while an inaccurate configuration may lead to an incident. Although it is dangerous and difficult to make a derailment online test, the effectiveness of DDSHV has been verified by the known dynamic cases and lab tests. In conclusion, DDSHV has assisted in understanding the process of derailment, finding the important factors affecting derailment and exploring the mechanism of dynamic derailment.

► The processes of two different types of derailment are explained.
► Critical point for wheel climb and critical speed for impact derailment are given.
► Hopf bifurcation behaviors of wheelset and derailment conditions on running instability are given.
► The simulation is testified by Manchester Benchmark, dynamic line test and lab test.