Vehicle dynamic performance under steel spring failure conditions

Four failure cases of axlebox steel spring for one side of leading wheelset were considered, namely: the inner and outer rings of steel spring both fractured; just the outer ring fractured; just the inner ring fractured; the whole spring frozen.Then vehicle dynamics model considering the failure cases was set up, and the influence of spring failure on vehicle dynamics performance was analyzed.Simulation result indicates that when the spring is in failure conditions, the equilibrium positions of wheelsets deviate from track center line, the critical speeds of vehicle reduce, the deviation and decrease are largest when the inner and outer rings of steel spring both fracture, and their largest values are about 3mm and 30km·h^-1 respectively.The wheelset with failure spring has larger wheel unloading, the value is largest in the both fractured case and is about 50 kN.For the bogie, the vertical suspension forces decrease at the positions of failure spring and its diagonal axle box, while the vertical suspension forces increase at the positions of another diagonal axle boxes, which results in large torsion force acting on the bogie.Spring fracture more easily brings the safety indexes(such as derailment coefficient and wheel unloading rate)to exceed their limit values, which greatly increases the safety risk of vehicle operation.When the ranges of speed are 200-300km·h^-1 on straight track and 100-300km·h^-1 oncurved track with radius 7 000 m, wheel unloading rates in both fractured case are greater than 0.8.The spring failure has little influence on the lateral riding performance of vehicle, but spring frozen failure will worsen the vertical riding performance of vehicle, and it increases by 0.1when vehicle speed is 300km·h^-1 compared with normal vehicle.