| With the further implementation of China’s railway planning of “Eight vertical and eight horizontal high-speed railway network”,high-speed railway has not only improved people’s way of travelling,but also ushered in more opportunities and challenges.With the increase of EMU operation mileage,the problem of wheel-rail periodic wear gradually highlights and seriously affects the normal operation and maintenance cycle of the train,which urgently needs to be solved.Therefore,this dissertation analyzes the influencing factors,formation and growth mechanism through the actual measurement and theory.Based on the dynamic model of the vehicle-orbit coupling system,the influence on the dynamic response of the rail system is studied,and the occurrence mechanism is summarized,and the inhibition measures are proposed.The specific research work and the innovative achievements are as follows:(1)Wheel-rail periodic grinding mainly refers to the wheel harmonic grinding and steel rail grinding.By testing the wheel harmonic grinding,and measuring the relationship between wheel diameter,speed and wheelbase,the relationship between the frame and the modal vibration and frequency of the frame.The results show that the wheel-rail shock vibration frequency is related to the wheelbase and rail type.When the wheel produces an initial defect,each orbital impact will produce friction at the defect position,and the wear extends wavy along the circumference of the tread.When the wave grinding head is connected,the initial wheel harmonic wear is formed.The initial wheel harmonic grinding further aggravates the wheel and rail vibration,making the wheel harmonic grinding gradually develop from low order to higher order.When the amplitude and order reach a certain extent,the impact vibration will occur between the wheels and rail,and the wheel harmonic grinding will grow faster.When entering and leaving the station or large slope section,the vehicle frequently increases and slows the stable sliding relationship between the wheels and rail,which increases the sliding area at the wheel and rail contact spot,and forms the small radius curve section,the wheels causes the first order bending,vertical and transverse load,leading to the formation of the rail grinding.(2)The occurrence mechanism of wheel-rail periodic grinding is further theoretically analyzed.By establishing a nonlinear dynamic model of stick-slip vibration considering dry friction factors,the connection relationship of adhesion,sliding and collision motion in the system motion is deduced.The mechanism and motion behavior of stick-slip vibration are studied.The occurrence mechanism of periodic wear of wheel and rail is revealed.The results show that the low frequency area system shows large oscillation and reciprocating change between the oscillation,for a kind of typical periodic vibration motion that makes the wheel and rail contact spot stick-slip area sharp change,which causes wheel-rail contact area wheel rail transverse sliding,so that the transverse force is periodic change,and eventually induce the occurrence of wheel and rail periodic wear.(3)Based on the Kalker simplified theory,the helep force of the rolling elastic contact is derived,and the equation of motion along the linear track is obtained by coordinate transformation.The influence of the wheel-track periodic wear on the dynamic response of the rail system is analyzed.The results show that the wheel-rail vertical force increases with the amplitude,and the speed and order do not show a single growth trend.The peak vibration value of the bogie frame and axle box is close to the excitation frequency of wheel harmonic grinding,and the vibration amplitude increases with the increase of wheel harmonic grinding amplitude.The wheel harmonic grinding excitation frequency at high order is easy to stimulate the inherent bending mode of the wheel,which intensifies the vibration of wheel and rail,then affects the contact relationship between wheels and rail,and significantly increases the creep rate / force.The influence of fastener stiffness on the creep characteristic is correlated with the speed;and the maximum value of the vertical force is in the grinding section of the periodic wear condition 1.At high speed,the rail jump occurs due to the periodic wear of the wheel and rail.The rail wave grinding has less influence on the transverse force of wheel and rail.The periodic wear of wheel and rail is significantly affected by the speed,while the influence of rail grinding on the transverse creep force has no dominant role.Residual wave grinding has little influence on dynamic interaction force and creep characteristics between wheel and rail.(4)According to EN 13103-1:2017 standard,the fatigue strength of non-power axle and power axle is calculated respectively,without unbalanced lateral acceleration and unbalanced lateral acceleration.The results show that the minimum safety factor of the main test parts is lower than that of the non-power axle.Therefore,using the von Mises axle,the axle stress is obtained by finite element analysis,the axle load time course under wheel harmonic grinding,and Brown-Miller method to calculate the axle fatigue life under wheel harmonic grinding.The results show that the axle fatigue life under the wheel harmonic wear is 19.2a,occurring at the arc transition site inside the wheel seat.The wheel rail vibration has obvious adverse effects on the fatigue life of the axle. |
