The lightweight design of the brake disc, which are one of the rotating part of train’s wheelsets, can effectively reduce the dynamic axle weight, which will certainly affect wheel-rail contact characteristics and the vibration response. Hereby, the wheel-rail excitations and variations of wheel set’s characteristic frequency caused by reduction in dynamic axle weight, as well as its influences on the bogie vibrations and wheel polygons deserve in-depth study.In this work, based on applications of aluminum alloy brake discs and cast iron ones, the influences of weight reduction in brake disc on dynamic performances of the urban railway vehicles were systematically studied by methods of dynamics simulation, track test, etc.Using dynamics simulations, straight and curvilinear dynamic performances and operation safety of the vehicles were contrastively analyzed, in conditions of rail vehicles mounted with aluminum alloy brake discs and cast iron brake discs separately.The results revealed that the vertical loads of wheel-rail and rate of wheel load reduction could be improved for the vehicles assembled with aluminum alloy brake discs compared with the cast iron ones，and little impacts had made on the stability, ride comfort and derailment coefficient of the vehicles at the same time. In addition, comparative track tests of the vehicles using aluminum alloy brake discs and cast iron ones were carried out. Compared with cast iron brake discs, aluminum alloy ones could reduce the vertical acceleration of axle box and bogie frame by about 10% and 21%, respectively. and meanwhile little difference have produced in ride stability of the vehicles. Moreover, dynamic impacts between wheel and rail and wheel polygon states were monitored through MTPDS (Metro Train Performance Detection System) both for the vehicles assembled with aluminum alloy brake discs and cast iron ones. The results showed that the proportion of non-polygonal wheels could be increased by about 16% for the case of using aluminum alloy brake discs.In conclusion of simulation results, the field test and the wheel-rail condition monitoring, the lightweight aluminum alloy brake disc can reduce the unsprung mass of rail vehicles and improve the dynamic performances, Based on the dynamics simulations, track tests and wheel-rail condition monitoring, it demonstrated that the lightweight aluminum alloy brake discs could reduce the unsprung mass and thus improve the dynamic performances of the vehicles,which can reduce the vibration loads of train bogies and the evolution speed to polygonal wheels. This study is the first to quantitatively analyse the influences of the lightweight brake disc on dynamic performances of the rail vehicle, which provides a new design idea for vehicle performances optimization.

Mr. Jian-Hang Cao, Senior Engineer, China Academy of Railway Sciences; Mr. Biao-qiang Jiao, Professor, China Academy of Railway Sciences Corporation Limted