Effect Of Wheel Tread Damage On Dynamic Behaviour Of High Speed Trains

The wheel damage such as the wheel wear, polygon and flat is an important issue in high speed railway transportation in recent years. As the increasing of the operation speed of the train, the wheel damage problem has become more and more serious. The change of wheel profile will make the wheel/rail relation more complex and affect the vehicle dynamic performance, including the hunting stability, ride quality, safety and reliability of the vehicle system. In this thesis, using the method of combining the numerical simulations and tests, the effects of wheel danage on wheel/rail geometry match, contact mechanics and vehicle dynamics are analyzed in detail. The main research work of the thesis is as below:(1) Based on the field test data of a high speed train on the Beijing-Shanghai line, the wheel wear is classified as vertical even wear, asymmetric wear, out of round wear (polygon),etc. The relation between the tread wear and the operating mileage is concluded according to the measured tread/flange wear volume and wear range. Meanwhile, the influence of the equivalent conicity on the motion stability of high speed train is discussed by analyzing the relation between the wheel wear and the contact parameters, such as equivalent conicity, contact angle. The ratio of the contact angle difference to the equivalent conicity is usually about 27 when the wheelset lateral displacement equals to 3 mm, which provides a reference to study the vehicle dynamic performance in the case of without the actual wheel wear profile.(2) The multi-body dynamic model of the vehicle system is set up to study the influence of the wheel wear on the dynamic performance of the high-speed train. The flexible-rigid coupled model is set up to study the influence of the high frequency vibration caused by the wheel out of roundness (OOR) on the dynamic perofrmance, in which the carbody, bogie and wheelset are treated as flexible bodies. A new wheel OOR model is presented in which the wheel radius changes along the circumferential direction and the effect of radius on wheel/rail relation is considered. The mathematic model for wheel flat is modified based on the work of former researchers. The wheel flat is simulated through adjusting the wheel radius and the influence of the radius on the wheel/rail contact parameters is taken into consideration.(3) In order to understand the calculating difference between the multi-body rigid model and the flexible-rigid coupled model, especially the influence of the high frequency vibration caused by the wheel OOR on the dynamic performance, the dynamic performance including the stability, ride comfort and curving behavior for standard wheel, polygon wheel and flat wheel are calculated and compared using the two models.(4) The wheel/rail contact geometry is the foundation for studying the wheel/rail dynamics interaction. The non-Hertz contact theory is adopted to calculate the contact span and normal force and then the programme developed by using Matlab can be used to calculate normal contact force for the arbitrary wheel/rail profile. The normal contact stresses are analyzed in one wear cyclefor vertical even wear wheel, four polygon wheel profiles measured on Beijing-Shanghai line and the new wheel flat model. In the mean time, the wheel/rail creep forces in one wear cycle are calculated by using the simplified Kalker theory.(5) Based on the measured S1002CN wheel profile wear data, the wheel profiles for different mileage are built using the muti-body dynamic code SIMPACK and the effects of vertical even wear and asymmetric wear on dynamic performance of high speed vehicle are calculated. The asymmetric cases include wheel radius difference and actual measured asymmetric wear. The wear profiles under different wear milages are fitted according to the actual measured wear and the dynamic calculations are conducted. The limit value of the wheel radius difference for high speed train is proposed based on the dynamic simulation for asymmetric wheel wear.(6) Wheel OOR is an already well-known problem, and the main forms of OOR are 1,3,6 and 11 order polygonals on Beijing -shanghai line. It is assumed that the shape of wheel profile is unchanged but only the wheel OOR changes. The polygonal wheels are simulated by programming while the phase difference of the two wheel out of roundness of the same wheelset is ignored. This paper simulates the dynamic performance of the main polygon wheel when high-speed running, and determines the critical range of the wheel OOR. The vertical wheel-rail contact forces are used for the vehicle running safety evaluation.(7) The models of the new and old wheel flat are set up. The wheel/rail vertical interactive force produced by the wheel flat is analyzed. The results show that the wheel/rail vertical interaction force produced by the old wheel flat increases as the vehicle running speed increases, and it is considerably larger than the force produced by the new wheel flat in the high speed region. The sprung mass and unsprung mass has little influence on the P1 and P2 forces. The wheel flat permitted value is determined by using the wheel/rail vertical force limit.