Analysis And Assessment Of Highspeed Trains Dynamic Performance Due To Performance Evolution Of Key Components

Speed and safety are the development target and eternal theme for railway transportation.As part of the huge system of high speed railway,high-speed train adopts the way of wheel/rail rolling contact to complete tasks of loading and passenger transport.With the significant increase in train speed,the dynamic interaction between vehicle and track becomes stronger,and the relevant dynamic problems which can affect running safety and ride comfort in line operations are growing,such as wheel wear,wheel polygonalization,rail corrugation and suspension component failures.If these problems are not detected and eliminated timely,the normal operations of high-speed train will be seriously affected.What is worse,the major security incident may occur which can bring great loss in economy and personal property for passengers.Therefore,the relevant dynamic problems appearing in line operations are intensively studied in this paper combining with mechanism analysis and numerical calculation.The specific research works of this paper are shown as follows:(1)Due to the appearances of middle and high frequency vibration and carbody elastic vibration problems for high speed train in service,a corresponding analytical model is improved,where the influences of elastic deformation of main vehicle parts and track are comprehensively considered.Based on rigid-flexible coupling dynamics theory,main components in vehicle dynamics model such as wheelset,axlebox,bogie frame and carbody are modeled as flexible bodies so that the coupling between elastic deformation and rigid motion of these main parts is possible to be simulated.The slab track is treated as a flexible structure system where the rails are built as two discretely supported continuous beams,and the slab is modeled using 3D solid finite element method.The linear spring-damper elements are used to simulate the fastener system and the support structure between slab and subgrade.(2)To well understand the vibration characteristics of vehicle system under axlebox bearing fault condition,the axlebox bearing dynamics model is essential.Based on the vehicle system dynamics model the rigid-body dynamics model of axlebox bearing is set up including outer ring,inner ring and cage.And the interaction between outer ring and inner ring is transferred through rollers which are equivalent to several force elements.(3)A detailed study on the relation between tread equivalent concity and operating mileage in the wheel reprofiling interval is carried out,and the influence of wheel tread wear on high speed train dynamics is also analyzed.Using different evaluating methods for the hunting instability,the critical speed of high speed vehicle under different operating mileages are achieved respectively.According to the hunting instability problems presented by high speed train in service,the scope of equivalent concity which meets the normal operation request for high-speed trains is suggested.(4)Based on the improved analytical model,the change of wheel radius method to simulate defective wheel such as wheel flat and wheel polygonalization is used.And the effect of defective wheel on the vibration response of high speed vehicle is investigated.Also the vibration responses due to rail corrugation and weld joint are discussed.According to the numerical simulation results and the wheel/rail vertical force limit value,the related permitted sizes of wheel flat,wheel polygonalization,rail corrugation and rail weld joint are suggested and discussed.(5)Based on the roller rig test results,the phase differences of vertical-pitch as well as vertical-roll are compared between the normal case and different primary vertical damper failure cases.Through a series of numerical simulations,the characteristics of phase differences of vertical-pitch as well as vertical-roll are summarized in the case of the primary vertical damper failure at different positions.(6)The dynamic performances of high-speed vehicle are systematically analyzed under different suspension parameters including anti-yaw damper force,the clearance of guiding arm joint for axlebox,the stiffness of the joint and primary steel spring.And the scopes of suspension parameters which meet the normal operation request for high-speed trains are suggested.Under the axlebox bearing fault condition considering bearing surface early defect and waviness,the vehicle system vibration characteristics are analyzed.These results help to provide theoretical guidance and reference for railway vehicle axlebox bearing fault detection.