Finite Element Analysis And Model Study On Frictional Self-excited Vibration Inducing Rail Corrugation On Tight Curves In Metro System

All the railway lines using the steel-wheel vehicles are subject to rail corrugation.The severe wheel-rail vibrations caused by rail corrugation may damage the components of vehicle systems,and generate squeal noise.Meanwhile,rail corrugation leads to settlement of sleepers,breakdown of ballast beds and loosening of under-rail structures.With the development of rail corrugation,the vibrations of train systems are aggravated,and the running safety may even been threatened.However,the generation mechanism and effective solution of rail corrugation are still not fully known so far.Many efforts have been made by researchers in this field for more than one hundred years,but there has not been a universally accepted explanation on how rail corrugation is caused.Slight rail corrugation can be eliminated by grinding,but when it becomes severe,the rail must be replaced,which costs time and money.Therefore,suppressing corrugation by investigating the corrugation mechanism is a fundamental solution.A wheel-rail contact model of a type B metro vehicle on tight curve is established by utilizing FEM based on the theory proposed by Professor Guangxiong Chen that the saturated wheel-rail creep force induces frictional self-excited vibration which resulting in rail corrugation.Moreover,this model is divided into three different fastener-simulation models: the spring-damper fastener model,the solid-connected model and the solid-contact model.Adopting the above model,complex eigenvalue analysis and transient dynamic analysis are conducted to deeply investigate the mechanism of rail corrugation,and the significant results are presented as follows:(1)The frequency range of rail corrugation in the actual railway is about 290-365 Hz based on the wave lengths measured in field tests.Complex eigenvalue analysis results show that the solid element fastener models is able to simulate rail corrugation better than the traditional spring-damper fastener model does.The unstable vibration frequency forecasted by the established contact model is 294.19 Hz,which is the most accurate result among the three models.Furthermore,the other unstable vibration at 516.01 Hz forecasted by the contact model is found to make a small contribution and thus can be ignored.(2)Transient dynamic analysis is conducted with the contact model whose performance is the best.Dynamic wheel-rail contact force and vertical acceleration of the test points indicate that the fluctuation at inner-rail position is obviously stronger than that at outer-rail position,and this result is in accordance with both the modal results obtained from complex eigenvalue analysis and the rail corrugation phenomenon observed in the field.PSD analysis result also demonstrates that the signal intension at inner-rail position is greater.Besides,the frequency of the strongest signal of PSD analysis is very close to the complex eigenvalue analysis result and within the frequency range of rail corrugation in the actual railway.(3)Impact analysis is conducted to study the influence on rail corrugation of the fasteners' equivalent stiffness.Variations of fastener stiffness in a certain range have little impact on frequencies of frictional self-excited vibrations.Nevertheless,the corrugation would be more serious when the vertical fastener stiffness is too small.In conclusion,the rail corrugation calculated with the wheel-rail contact model and the comparison between the analysis result and field investigation verify that friction-excited vibration is a significant factor of rail corrugation generation on the tight curves.The contact fastener model possesses an admirable accuracy in simulation,and this model should be used in numerical simulation.Increasing of the fasteners' vertical stiffness in a suitable range can suppress rail corrugation to a certain extent.