Dynamic Modelling and Response Research on Derailment Protection of High-Speed EMU

High-speed electric multiple units (EMUs) are exposed to derailment risks under extreme scenarios such as collisions or foreign object intrusions, posing serious threats to railway operational safety. To address this issue, a vehicle–track coupled dynamics model incorporating nonlinear wheel–rail interaction and 3D geometric contact relationships was developed. The model captures the complete evolution from normal operation to derailment and subsequent engagement of protective devices, while fully accounting for multipoint collisions and impact force transmission mechanisms among wheelsets, bogie frames, protective devices, and track components. Multi-condition simulations were conducted under varying speeds and collision scenarios to systematically analyze wheelset displacement responses, impact loads, and vibration characteristics. In addition, derailment bench tests were performed to replicate controlled derailment scenarios, during which the lateral and vertical displacements of wheelsets were measured. The experimental results exhibited high consistency with simulation predictions in terms of waveform and amplitude, thereby validating the reliability of the proposed model and confirming the effectiveness of the derailment protection devices. The results indicate that derailment protection devices can effectively suppress excessive lateral wheelset displacements, reduce the cyclic impact loads on track fastenings, and significantly enhance the post-derailment trajectory stability of vehicles. These findings provide theoretical support for the safety design optimization of EMUs and hold important engineering implications for improving the resilience of high-speed railway systems.