Research On Wheel Wear Of Heavy Haul Freight Car Based On The Creep Mechanism

With the increasing axle load of freight car, the researches on how to decrease wheel/rail wear and increase transportation economic benefits have important guiding significance. The vehicle system dynamic model was built in SIMPACK software and the power spectrum density of track irregularity was transformed to time-domain irregularity by Inverse Fourier Transform, then the wheel wear simulation program named WWS was developed in MATLAB. The simulation and field results were used to correct the Zobory wear model, then the factors which affect heavy haul car’s wheel wear were studied and the match relations between axle load and running velocity were determined base on wheel wear. The adaptabilities of wheel/rail profile and bogie structure to vehicle’s imperfect condition were analyzed by wheel wear simulation. The characteristics of rolling contact fatigue on rail surface were analyzed and the competitions between wheel wear and rolling contact fatigue were numerical simulated. Main conclusions are drawn as follows:1. The semi-Hertzian model’s patch is closer to CONTACT than Hertzian model, and the results of FASTSIM algorithm base on semi-Hertzian are agree well with the CONTACT’s. Because the calculation speed is very fast, so the semi-Hertzian model can be used in wheel wear simulation which need great deal of wheel/rail rolling contact computation.2. When elastic velocity and semi-Hertzian model were used in wear calculation, the results are agree well with the CONTACT’s. The normal load mainly affect the4th wear zone of Jendel model, creepage and friction coefficient mainly affect the adhere/slip area and wear zone. In small creep condition. Braghin model have maximum wear volume, Jendel model take second place and the Zobory model have minimum wear volume, in large creep condition, wear volume in Jendel model is much larger than the other models.3. All the correlation coefficients of American track center line’s irregularity are less than0.3and low correlative, so the relation between center line and left/right rail irregularity was used to transform the center line irregularity equivalency to left and right rail. The one side power spectrum density of America five grade railway is higher than the China main line in low frequency and less than it in high frequency.4. Wavelet smoothing can reflect the characteristic of original data than other smoothing methods, meanwhile the calculation speed and precision can be met when the maximum updating wear depth is0.1mm. When Zobory. Jendel and Braghin model were used to simulate the wheel wear of heavy haul car which running in Ring-line and Daqin railway line, all the simulation results are lager than field results, so the Zobory model was corrected in this paper, then the affects of worn wheel on vehicle system dynamics were analyzed.5. Increasing axle load lead wheel wear increase rapidly and the axle load mainly affect the wear in wheel tread rather than flange. Wear behaviour of swing motion bogie and cross-braced bogie nearly uniform, and the radial bogie can reduce the wheel flange wear effectively. Wheel tread’s wear will decrease with the increasing of bogie center distance. The lateral and vertical stiffness of primary suspension have little effect on wheel wear, meanwhile the longitudinal stiffness has great effect on wheel tread and flange wear. The wheel wear lifetime reduced with the increasing of wheelbase and decreasing of wheel radius. The increasing of curve radius can lead wheel wear decrease rapidly, and the gauge-widen can increasing the wheel wear lifetime. In view of wheel wear, the1/40rail cant is reasonable when LM wheel profile and CN75rail profile matched. The CN75rail profile can lead less wheel tread’s wear than CN60and UIC60. The wheel wear became more severe when the line grade is low. Vehicle’s velocity affect the wear in wheel tread rather than flange, and the wear increase rapidly with the increasing of vehicle velocity. When the wheel/rail friction coefficient is0.1, the wheel wear decreased obviously, but when the coefficients are0.25,0.4and0.55, the coefficient have little effect on wheel wear. Take for the wheel wear of the freight car which axle load is25t and running speed is100km/h as reference, the freight car with27.5t axle load do not need to decrease speed, and the speed of freight car with30t.32.5t and35t axle load need to decrease the running speed to85km/h,80km/h and60km/h respectively.6. The initial deflection angle ψ0have greater effect on attack angle of wheelset, and radius difference ΔD have greater effect on lateral displacement of wheelset, meanwhile, greater attack angle and lateral displacement can be caused by lower equivalent conicity of wheel profile. Both ψ0and ΔD will decrease wheel wear lifetime, ψ0, mainly affect wheel wear lifetime and ΔD mainly lead to wheel eccentric wear. In view of wheel wear, the swing motion bogie has best adaptability to vehicle’s imperfect condition, the cross-braced bogie takes the second place and the radial bogie has the poorest adaptability.7. With the increasing of velocity and axle load, the fatigue damage will increase to a peak and diminish because of the wear increased follow with the velocity and axle load. The wheel-rail lubricate system used in sharp curve which radius less than600m will augment the fatigue damage rapidly and influence the safety of train, so the lubricate system must be cautious to used and the grinding should used together with the lubricate system. The wheel/rail contact condition and wheel material have great effect on the competition relation between rolling contact fatigue and wear. When the friction coefficient and creepage are smaller, the wheel material more easy to occur rolling contact fatigue damage because the wear is mild; the large friction coefficient and creepage make the wear play a leading role, and no rolling contact fatigue damage occur. The rolling contact fatigue damage inhibition role of bainite steel is better than CL60steel because bainite steel have higher yield strength.