Research On Key Factors Of Non-linear Stability Of High-speed Railway Vehicle

The general issues of mechanical system dynamics is vibration issues, but there are somemotion stability issues in vehicle system dynamics of high-speed railway, which are morecomplex than the general issues of mechanical system dynamics. This thesis describes indepth research background and significance of non-linear stability of high-speed railwayvehicle，and discusses current research about non-linear stability of high-speed railwayvehicle and several fundamental nonlinear influencing factors, including wheel-rail contactgeometry, wheel-rail contact creep and nonlinear properties of anti hunting damper. Thenthese nonlinear issues are studied and thesis discussed the relationship between them andnon-linear stability of the high-speed railway vehicle.(1) Thesis improved a kind of calculation methods of wheel-rail rolling contact geometrybased on polynomial function, and compared with conventional trace method and Adams/Rail RSGEO (geometry calculations module). After calculated accordingly to LMA/CHN60,CN profile/CHN60, S1002/UIC60, results show that there are more closed among resultsfrom polynomial function method and Adams/Rail RSGEO, and the gap among them is lessthan20%. Then it is used to calculate nonlinear parameters of LMA/CHN60new and wearingwheel-rail rolling contact geometry that are achieved by polynomial fitting method anddiscussed the relationship between them and non-linear stability of the high-speed railwayvehicle. The results from the simulation show the speed bifurcation curves will move to rightwith the decrease of nominal equivalent conicity, namely the critical speed linear andnonlinear critical velocity increases; when their nominal equivalent conicity are roughly same,the nonlinear parameters affect the dynamic response of the vehicle, and the linear criticalvelocity is significantly reduced with the decrease ofλ N,1. The results are verified by analysisof measured data.(2) Thesis established the finite element model of wheel-rail rolling contact based on LEmethod (Lagrange-Euler method) in ABAQUS, and simulated unsteady state of wheel-railrolling contact by adding inertial forces to wheelset axis and flowing material along thecircumference and surface of wheel. Elastic creepage calculated by the finite element modelcompared with rigid creepage. Results show that in the lateral movement, value differencebetween their longitudinal creepage is small, and maximum error is less than20%; there ismore distinct change trend about lateral creepage in left contact area than one in right contact area; rotate creepage of left wheel drop down in4mm lateral displacement. In the yawmovement, there are small fluctuations in elastic longitudinal creepage, and elastic lateralwheel creepage of left and right wheel appear different, but not change with increase of yawangle. When calculating wheel/rail contact creep forces by application of the finite elementmodel, the longitudinal creep force of the left and right wheels is close to results from KalkerCONTACT. Just difference is that lateral creep force distribution in contact area show bothpositive and negative, and makes much change of lateral creep force and maximum errorachieves42.7%, but maximum error of the longitudinal creep force is less than40%. Whenwheelset yaws, the longitudinal creep force of the wheels drop down with increase of yawangle. But the lateral creep force of the wheels enhances with increase of yaw angle, but itwill tend to saturation, which keeps same trend with results from Kalker theoreticalcalculations.(3) A series of creep force data has been calculated in different operating conditions(change of y′/vand y) by using the finite element model of wheel-rail rolling contact inABAQUS, which is applied in dynamic simulation by interpolation accordingly to change ofy′/vand y. The conventional calculation method of the creep force based on creepages is notused, but tables of creep force data from the finite element model are applied to research onnon-linear stability of single wheelset. Thesis elementarily explores application of creep forcedata from the finite element model in research on non-linear stability of high-speed railwayvehicle. Compared with the simulation of single wheelset model in Adams/Rail, the resultsshow that lateral displacement and yaw angle of wheelset keep same response with time, andtheir RMS value are17.9%and10.1%. Table of creep force data from the finite elementmodel can be effectively applied to dynamic simulation if enough operating conditions arecalculated.(4) Thesis constructed accurate and efficient numerical non-linear hydraulic model of antihunting damper in Easy5which can be applied in different kinds of damper and change innerphysical construction parameters according to analysis of its structure and working principle.Number of trials required to adjust the model can reduce to a minimum, and its applicationcan solve some disadvantages including model complexity and low efficiency or evendivergence of calculating results in simulations. Co-simulation method is used to researchstructure parameters of anti hunting damper and different hydraulic flowing mode, and their impact to vehicle stability and stationary. The results show that their impacts to vehiclestability are distinct, but their impacts to vehicle stationary are low. Different hydraulicflowing mode influences properties of anti hunting damper. There is more fluctuation whenusing vehicle model included yaw model with oil double orientation flowing to simulate.Therefore, we should try to improve symmetrical rate of the tensile/compressioncharacteristics of anti hunting damper in order to improve the stability of the vehicle.