Influence of suspension system service degradation characteristics on running stability performance of 160 km/h express freight car

This study proposes a simulation-based evaluation framework to investigate the effects of suspension component degradation on the dynamic performance of 160 km/h express freight cars. A multibody dynamics model was developed using SIMPACK to analyze several typical failure scenarios, including axle-box rubber spring degradation, primary vertical damper failure, secondary lateral damper malfunction, anti-yaw damper loss, and air spring leakage. Under the assumed track and loading conditions, single-component failures generally did not cause the stability index (W) to exceed the threshold of 2.5 at the design speed of 160 km/h. However, more severe cases—such as dual secondary damper failures, anti-yaw damper loss, and air spring rupture—led to noticeable increases in dynamic response. Based on these findings, preliminary speed restrictions ranging from 150 km/h to 50 km/h are suggested for different failure combinations. It should be emphasized that these conclusions are conditional and derived from simulation models with idealized assumptions. Further validation through instrumented field tests, broader parametric studies, and real-world condition modeling is essential before operational implementation. The study offers initial guidance for defining thresholds in train control and monitoring systems (TCMS) and for developing emergency response strategies under suspension fault conditions. This paper introduces the basic structure of the new 160 km/h express freight car and the special operating conditions associated with suspension failure. In this study, a transverse and vertical coupling nonlinear dynamic model of the vehicle system is established using SIMPACK, a multi-body system dynamics software. In this study, the SIMPACK multi-body system dynamics software is utilized to examine the unique operational conditions of express freight car, including scenarios such as the failure of axle-box rubber springs, primary vertical dampers, secondary lateral dampers, anti-yaw dampers, and air springs.