| The formation mechanism of rail corrugation is still a problem to be solved.Rail corrugation,especially short-pitch corrugation is easy to excite the high-frequency vibration of the wheel and rail system,which leads to abnormal vibration and noise and fatigue failure of key components of vehicle and track,and threatens the safety of the train operation for serious rail corrugation.In recent years,with the continuous improvement and application of new types of vibration-reduction track structure in metro,the improving of vehicle operation speed and axle load,rail corrugation on metro line shows diversification.Its cause is not completely clear,so that it is impossible to take effective measures to alleviate or eliminate rail corrugation.Aiming at the phenomenon of short-pitch corrugation occurring on the fastener vibration damping track of metro,this thesis investigated its formation mechanism from the point of view of the high-frequency dynamic characteristics of wheel-rail system through by combining field test and theoretical simulation method.The main work and conclusions are as follows.(1)The typical rail corrugation characteristics of the fastener vibration damping track were investigated on site.The test results showed that the significant wavelength of rail corrugation is 40-50 mm and the wave depth is about 0.05-0.12 mm.Its passing frequency is572-715 Hz at a normal vehicle speed of 103 km/h.Under the same vehicle operation conditions,different track structures of the same line show rail corrugation with different wavelength,which may be related to the inherent characteristics of the track.(2)A three-dimensional finite element model of elastic wheel-rail transient rolling contact for the metro fastener vibration damping track was established based on the combination of the implicit and explicit algorithm of the finite element software ABAQUS.The model considered the high-frequency flexibility of the wheel-rail structure,the rotation effect of the wheelset,the inertia effect of spring mass.The vibration damping fastener system and primary suspension were simulated by stiffness and damping elements.Using the numerical model,the wheel-rail transient rolling contact behavior,including the wheel-rail high-frequency vibration characteristics,rail dynamic displacement,adhesion-slip distribution in the contact area,transient rolling contact force and stress distribution of wheel-rail,was investigated when the wheel rolling on a straight rail under typical working conditions.The results showed that after the wheel rolls about 2.2 m at the speed of 103 km/h,the wheel-rail vibration basically reaches a steady state and the wheel-rail vertical force differs from the static wheel load by 0.39-4.68 k N.The model can consider the influence of vehicle traction on the wheel-rail longitudinal creep force.Compared with the condition without traction,i.e.pure rolling contact,the slip area in the wheel-rail contact area with a traction coefficient of0.3 accounts for 31.5% of the total contact area,and the maximum tangential contact stress increases by about 6.5 times.In addition,the accuracy of the finite element model was verified by the Hertzian contact theory and Kalker’s program CONTACT.the maximum contact pressure obtained by the finite element model is 7.11% smaller than the Hertzian contact theory and 4.74% smaller than the program CONTACT.The tangential contact stresses in the adhesion area calculated by the finite element model was slightly different from that by the program CONTACT,with the maximum difference of about 6%.(3)The high-frequency dynamic characteristics of the track,wheelset and coupling structure were studied by modal analysis method,and the high-frequency sensitive frequency band of the track structure is analyzed by hammer excitation on site and the broadband excitation response method.The results showed that the passing frequency of rail corrugation(572-715 Hz)on fastener vibration damping track is different from the pinned-pinned resonance frequency(1106 Hz),but is similar to the rail sensitive modal frequency(570-720Hz)at which the rail vibrates with vertical bending against the track bed.When the wheel rolls on rail dents with different wavelengths(25-90 mm),the vibration acceleration and vertical force response of wheel and rail are the most sensitive under the excitation of rail dent with a wavelength of 40 mm.Their frequency bands are 488-899 Hz and 521-736 Hz,respectively,which are close to the sensitive frequency band of track.The track resonance can easily occur under the excitation of a 40 mm wavelength irregularity,which is easy to induce rail corrugation with main wavelength of 39-50 mm.(4)Combining with the contact parameters such as wheel-rail force and adhesion-slip distribution obtained from the wheel-rail transient rolling contact finite element model,a rail wear model based on the Archard wear calculation method was established.The characteristics of wheel-rail contact force and rail longitudinal wear were investigated when a wheel passed through a rail dent.The simulation results show that the wheel-rail force fluctuation is directly related to the rail friction work and rail wear.When the traction coefficient is 0.075,0.15 and0.3,the wavelength of rail wear is basically constant,and the significant wavelengths are 51 mm,52 mm and 52 mm respectively.When the vehicle passes through the fastener vibration damping track,the wheel-rail vertical force and rail longitudinal wear performance shows frequency-fixing mechanism with significant frequency range of 610-838 Hz under different vehicle operating speeds.The significant wavelengths of rail wear at vehicle operation speed of 75 km/h,85 km/h,95 km/h and 103 km/h are 44 mm,46 mm,49 mm and 52 mm,respectively.The formation of the 40-50mm short-pitch corrugation on the fastener vibration damping track is mainly caused by the vertical bending mode of the rail in the sensitive frequency band od 570-720 Hz being excited.The simulated rail wear wavelength is basically consistent with the field test results. |
PDF Full Text Request