Research On The Influences Of Abnormal Wheel-rail Relationship And Aerodynamic Loads On The Dynamics Performance Of High-speed Trains

When trains run through different railway lines or pass the abnormal sections of rail after grinding,the wheel-rail matching relationship is complex and changeable,meanwhile the abnormal wheel-rail matching relationship will cause to the hunting motion of railway vehicles and finally deteriorates the ride comfort and running safety.On condition that the hunting motion doesn’t satisfy the alarm criteria,the train still keeps running at high speed.At this point,the interaction between the train and the surrounding environment can’t be ignored.In this thesis,the aerodynamic forces are considered when the high-speed train is running in the environment,and the influences of abnormal wheel rail relationship and aerodynamic loads on the hunting stability and dynamic performance of the train are studied starting from the theory of multi-body dynamics and the method of fluid-structure coupling off-line simulation.The corresponding suggestions are given out based on the simulation results,which contains a certain engineering value to ensure the running safety of the high-speed trains.In this thesis,a typical type of high-speed train is taken as the research object,I mainly did the following work:(1)The three-car multiple unit model is developed using the multi-body dynamic software SIMPACK.The phenomena of stability,carbody hunting and bogie hunting are reproduced in simulation by integrating the wheel-rail contact relationships with different equivalent conicities into the model.The dynamic performances under these three states are then evaluated and compared,the differences between the stable state and the unstable state are summarized.(2)A simplified geometric model of the three-car multiple unit was established by using SOLIDWORKS software.Considering the typical operation conditions of a single train withstand the action of steady-state cross wind and two trains meeting at constant speed,the characteristics of pressure and aerodynamic load for each vehicle under these two typical cases are calculated and analyzed based on the fluent fluid numerical calculation software FLUENT.The results show that the aerodynamic forces of the head and tail cars are obviously different.Moreover,the simulation model is verified by comparing the carbody lateral acceleration between the simulation results and the test results at the speed of 200 km/h.(3)Using the fluid structure coupling off-line simulation method,the influences of abnormal wheel-rail relationship and aerodynamic loads on the hunting stability and dynamic performances of the train are studied from the perspective of displacements,running quality and running safety.The results show that the lateral displacement of head car is much larger than that of the tail car,and the movement of both carbody and wheelset are different under different wheel-rail contact relationships.The crosswind will aggravate the phenomenon of train tail sway at the running speed of 200 km/h and 250 km/h.Furthermore,when the train speed is 350 km/h,the train loses the ability of resisting the crosswind in the bogie hunting state at abnormal high equivalent conicity,at the running speed of 300 km/h,the worst wind resistance ability in the carbody hunting state at abnormal low equivalent conicity and the permissible wind velocity decreases with the increase of train running speed.The phenomenon of two trains’ meeting causes the aggravation of carbody hunting at abnormal low equivalent conicity.For the bogie hunting state at abnormal high equivalent conicity,there exists the risk of derailment for the train when the two trains’ meeting at the speed of 350 km/h.However,the two trains’ meeting has little influence on the bogie hunting motion at relatively low running speed.Aiming at the harsh working conditions of poor adaptability to the environment in the bogie hunting state at high equivalent conicity,optimizing the damping of the antisnaking damper can improve the wind resistance of the train at high speed.