Study On The Influence Of The Imperfect State Wheel On Metro Vehicle Dynamics Performance

With the rapid development of economy and the speeding up of urbanization, most cities in the world are faced with the problem of how to transport passengers quickly and efficiently over long distances. As an important part in the modern urban rail transit, metro vehicle plays an important role in easing traffic congestion, improving efficiency of citizen travel and reducing environment pollution, ect. However, because of the poor manufacturing process, low maintenance level, vehicle running and other impact factors, wheelset always appears some imperfect state, such as tread worn, wheel diameter difference, and so on. This will not only worsen the riding index and safety when curve passing, but also undermine the track structure, and accelerate the line deformation. Therefore, study on the influence of the imperfect state wheel has much more practical significance, and it can also provide a theoretical basis and technical support for the future metro vehicle structure design, hanging design and the maintenance of the vehicles.This paper expounds the development history of the metro vehicle at home and abroad, briefly illustrates the kinds and forming reason of the imperfect, and on the base of the fundamental of multi-body system dynamics, essential assumption and nonlinear relationship treatments, a metro vehicle model has been build by using the multi-body dynamics simulation software SIMPACK, then make an emulating calculation with the references in GB5599-85. The calculation results of the vehicle running performance show that the nonlinear critical speed of the vehicle, riding index and curve passing performance all can meet the standard requirements.On the base of above research, it was also studied that the influences of wheel diameter difference, wheel tread worn and wheel quality eccentric on metro vehicle dynamics performance in this paper. The results show that: the wheel diameter difference has a negative effect on the nonlinear critical speed, but has no influence on riding index. In curve passing,the wheel diameter difference has a little influence on capsizal coefficient, while the equivalence same phases wheel diameter difference has serious impact on the wheel/rail lateral force, derailment coefficient and abrasion index, and the equivalence opposite phases wheel diameter difference has most serious impact on wheel/axle lateral force and wheel load reduction rate. The tread worn will observably increase the rolling radius difference, the contact angles difference of wheel/rail, equivalent conicity and wheel contact position in the wheel/rail contact geometric. And for the vehicle running performance, The tread worn has a negative effect on nonlinear critical speed and riding index of the vehicle. In terms of curve passing, it can markedly reduce wheel/rail lateral force, derailment coefficient and abrasion index. Although wheel quality eccentric will produce a periodic excitation on the wheel, and will make a periodic forced vibration on the wheel/rail system, but has no effect on riding index and little effect on curve passing performance in the range of5mm eccentricity.