Dynamic Simulation Study On The Impact Of Deviation Of Cargo Gravity Centre On The NX₇₀ Flat Car Running Safety

The loading position of cargo can directly affects the running stability of the railway vehicle. Based on the vehicle dynamics, the lateral and longitudinal offset of the center of gravity of cargo affects the running stability of railway vehicle. Derailment may be caused when the lateral or longitudinal offset is too large. Currently, the provision of the lateral and longitudinal gravity center offset limit lacks experimental and theoretical basis. A precise measurement of the offset involves very complex technical problems and requires a lot of manpower and material resources. Therefore, computer simulation becomes a very important way to carry out such research.This work focuses on how lateral and longitudinal offset of cargo gravity center affect the vehicle running safety indicators. The main content includes the following aspects:(1) The first part gives an introduction to the derailment criteria of foreign countries and China. The derailment coefficient and wheel load reduction rate limit, defined in the National Standards NO. GB5599-85, are taken as the derailment criteria.(2) Based on the presented running safety influence factors, an analysis of the forces to the vehicle when lateral offset happens on straight track, and when inward/outward lateral offset or longitude offset happens on curve track.(3) The dynamic simulation model of the NX70flat car is constructed using SIMPACK, considering the non-linear parts. The simulated rail line condition chooses the best track condition (level I) and the worst track condition (level â…¢) in China rail system. The plus excitation chooses the American fifth and third track spectrum. Finally, the reasonability of the simulation model is proved by some actual test data.(4)300simulation experimental programs are design based on the combination of many selected cargo loading conditions, track conditions and running speeds. The variation patterns of the derailment coefficient and the wheel load reduction rate corresponding to different track condition levels (â… , â…¢), different line conditions (straight, curve), different speeds (20km/h,70km/h,78km/h,120km/h) and different cargo gravity center positions are proposed through lots of simulation data. Consequently, the most adverse running condition can be found, which will offer valuable reference to the actual vehicle experiments in the future.