| The heavy-haul freight wagon is developing towards to the trend of lightweight,so that the axle-load can be reduced and the carrying capacity can be improved.The research on the flexible vibration of wheelset and its dynamic influence on the whole vehicle is significant for the technical improvement and design optimization of heavy-haul railway vehicle equipment.In view of this,aiming at the new 30 t heavy-haul freight wagon,the study of dynamic performance for heavy-haul freight wagon considering flexible vibration of wheelset is carried out.Based on the wheelset structure,the transformation from physical coordinates to modal coordinates is realized by the modal superposition method.Then the model of wheelset flexible body is established.Furthermore,the suspension system is connected with the interface nodes of flexible body in UM software,the rigid-flexible coupling dynamics model of heavy-haul freight wagon is finally established.The nonlinear factors,such as the wedge nonlinear friction damper and wheel-rail nonlinear creep characteristics are considered in the model.By superimposing the shortwave excitation in the track irregularity,the differences of vibration response,motion stability and curving performance of rigid and flexible wheelset models of heavy-haul wagon are studied.Finally,the wheel polygon wear of heavy-haul freight wagon was measured in field,which was used as the input excitation.Based on the simulation model,the dynamic characteristics of heavy-haul freight wagon vehicles considering the evolution of wheel out-of-round are studied,and the service performance are evaluated.The results indicate that,the deformation of the flexible wheelset can alleviate the wheel-rail rigid impact and weaken the wheel-rail rigid restraint ability at the same time.So the vibration amplitude of the flexible wheelset is reduced.The linear critical speed of heavy-haul freight wagon decreases by about 9%.The vibration acceleration of the flexible wheelset also reduces by about 30% comparing with that of the rigid wheelset.The influence of the elastic vibration of wheelset on the vibration transfer characteristics of the vehicle is deeply investigated.As the secondary suspension plays a better vibration isolation performance,the rigid and flexible models of the wheelset has less influence on the vibrations of car body and the bolster in heavy-haul freight wagon.By comparing the dynamic indexes of the two models at 90 km/h and the statistical maximum values,it can be found that the dynamic indexes of flexible wheelset are generally slightly lower than the result of the rigid wheelset.The reason is that the flexible wheelset has elastic buffer effect.It is also helpful to improve the curve negotiation of the heavy-haul freight wagon.Furthermore,the independent influence rule of each mode of the flexible wheelset is studied.It is found that,the 1st-order vertical and lateral bending modes of the wheelset alleviate the wheel-rail force.But at the same time,the mentioned modes can produce greater longitudinal creep forces,which may induce local wear in wheel profile.In addition,the first-order torsion,lateral bending and 2nd-order vertical bending modes are sensitive to running speed.The 30% difference in dynamic indices at different speeds can be observed.Finally,the field test of wheel polygon wear of heavy-haul wagon is carried out,and the test results are input into two models.The results show that,with the increase of wheelset polygon wear,the higher order polygon excitation can reflect the dynamic difference of rigid and flexible model more obvious.The wheel polygon wear greatly excites the elastic vibration of the wheelset.In general,the linear critical velocity,wheel-rail dynamic interaction and vibration responses of heavy-haul freight wagon will be overestimated when rigid wheelset is used.Therefore,it is necessary to consider the elastic vibration of the wheelset model in the simulation and evaluation of vehicle dynamic performance. |
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