Fe Analyses Of High-speed Rolling Contact Behavior Of Polygonized Wheelset During Curving

The high-order polygonal wear is a kind of wheel damage widely occurring in high-speed trains,which increases the wheel-rail forces dramatically,resulting in the intense vibration and noise.Vibration transmitted in the vehicle-track system further leads to the fatigue damage and failure of some important components.In addition,the wheel-rail interaction during curving is more complex than that in tangent track at high-speed,and the longitudinal,lateral and spin creeps when curving are larger than those in tangent tracks,under the same conditions.When the polygonal wheel operates on the curves at high speed,the deeply analysis on transient wheel-rail rolling contact behavior will have the great meaning for understanding the formational mechanism of the polygonal wear.So,a vehicle dynamics model using SIMPACK and a 3D transient wheelset-rail rolling contact finite element(FE)model using ANSYS/Ls-dyna are established,to consider the influence of the polygonal wheel on the rolling contact behavior in high frequency during curving.The research backgrounds and current progresses of the polygonal wear,curve behaviors and wheel-rail rolling contact firstly reviewed in the first chapter.Note that the FE models is more fit for the contact analysis between wheel and rail in high frequency than the dynamics models,showing the necessity of developing a 3D transient FE model to study those issues.A typical case of polygonal wear and the corresponding monitor tests are described in chapter 2.The obvious 22~24 order polygonal wear occurring on the wheels is found with the maximum radial runout deviation of 0.506 mm.Based on the measured results of a large number of polygonal wheels,two typically polygonal patterns,i.e.,the measured polygonal wheel and the harmonic polygonal wheel with typical wave-length and wave-depth abstracted from the measured results,are used for simulatingTwo analysis models,based on a high-speed railway system in China,are introduced in chapter 3,including a vehicle dynamics model and a 3D transient wheelset-rail rolling contact FE model with polygonal wheels.The lateral displacement,roll angle and yaw angle of quasi-static wheelset are calculated by the vehicle dynamics model during curving,as the initial conditions of the FE model.Then using the FE model numerically simulates transient rolling-sliding behavior in the domain of a free wheelset passing over curve at high speed.Compared to the previous half-wheelset model,this model is further extended to a whole wheelset and curved track,taking the lateral creep and spin into account more accurately,which can also study the interactions of wheel-rail rolling contact behavior on both sides.In chapter 4,the transient rolling contact behaviors are analyzed on smooth contact surface when the wheelset operates on curves at high speed.The effects of different curve radius,speed,wheelset lateral displacement,traction and friction coefficient on contact force,stress,relative slip,stick-slip distributions and friction work are emphatically compared.The results show that the friction work of the outer rail and the inner rail respectively increased by 33.5% and decreased by 28.1%,when the curve radius decreases from the infinite to 7000 m at 280 km/h.The asymmetric wear phenomenon is more serious for the curves than the tangent tracks.During the wheelset runs on a R7000 m curve at 280 km/h(equilibrium speed 277.7 km/h),it’s found that wheel/rail wear becomes severe,either the traction coefficient is greater than 0.1(friction coefficient is 0.5)or the friction coefficient less than 0.2(traction coefficient is 0.1).In chapter 5,the differences of rolling contact behaviors are compared and analyzed when a free wheelset operates on a R7000 m curve at 280 km/h under the condition of smooth contact surface and polygonal wheel.It is found that the polygonal wear can significantly change the contact behaviors between wheel and rail,resulting in periodical fluctuations in contact force,contact stress,contact patch,equivalent stress and friction work,all related to a certain phase difference with polygonal wheel.The vibrational amplitude of wheel-rail force increases monotonously with the increase of wave depth and order of wheel polygon.For example,the 23 order polygonal wear wheel with wave depth of 0.3 mm,running on a R7000 m curve at 280 km/h,can cause the separation between wheel and rail.High frequency wheel-rail interaction excited by the polygonal wheel on one side of rails can be transmitted to the other side through axle,resulting in the uneven wear of the wheel and the rail on the other side.Moreover,the larger the traction coefficient is,the higher the transmission efficiency is,which may eventually lead to the polygonal wear on both sides’ wheels.Finally,the conclusions are given and the future work is discussed.