A PCM based rigid-flexible coupled dynamic modeling approach for post-derailment response analysis of URT vehicles

As unmanned driving technology advances, the autonomous safety of urban rail transit (URT) vehicles has been recognized as a paramount concern. As the final line of defense for the safety of autonomous operations, research into post-derailment behavior is deemed critical for the assessment of operational safety and the prevention of accident escalation. However, existing derailment monitoring and post-derailment alarm systems, which rely on axle box acceleration (ABA) signals, lack clear standards and evaluation metrics for identifying and assessing post-derailment impact responses. To address this issue, a rigid-flexible modeling approach based on the polygon contact model (PCM) is proposed to accurately simulate post-derailment dynamic behavior and impact responses. A multi-rigid-body vehicle-track model is established using Type A URT vehicle parameters, with flexible wheelsets and rails replacing rigid components. Hertz and PCM contacts are applied to pre- and post-derailment areas respectively, developing a rigid-flexible coupled derailment dynamics model (RFCDDM). The feasibility and accuracy of RFCDDM are verified through comparisons with monitored ABA data and derailment tests. Further, the verified model is used to reproduce post-derailment scenarios under varied speed-load combinations, revealing impact amplitude variation laws. The results indicate that increased speed shifts wheelset lateral displacement-induced impact locations from fasteners to sleepers or track beds; the first impact response presents a “rise-fall-rise” trend, while continuous impacts show attenuation. These findings support the optimization on optimizing safety evaluation systems for health monitoring in the operation of URT vehicles.