Research On Coupler With MRF Wheelsets And Dynamics Performance Of The Vehicle

Since railway is plunged into business, the wheelsets with twowheels fixed to two ends of one axle has commonly been adopted in railway vehicle. The advantage of traditional fixed wheelsets is that they have self-steering capability produced by longitudinal creep moments, however it possibly occurs of hunting unstability when the speed becomes higher, so independently rotating wheels(IRW) is attached importance increasingly. IRW don' t possess longitudinal creep forces, so it doesn' t occur of hunting and the stability of the vehicle system is improved. But IRW lose self-steering capability without longitudinal creep moments, so its restoration capability and curving performances become worse. Thereupon, the idea of coupled wheelsets is brought forward that the left and right wheels of wheelsets are properly coupled to produce a few longitudinal creep forces. In this way, coupled wheelsets have both self-steering capability and higher critical velocity. Some researches on coupled wheelsets have been carried on abroad while scholars in our country do less works before 2001. In 2002, Dr Chimaoru with Sothwest jiaotong University raise magneto-rheologial fluid coupled wheelsets (MRFCW) on the basis of concluding research achievements at home or aboard and combining technology progress of magneto-rheologial fluid(MRF) nowadays, at the same time, he has done lots of works. This paper explores deeply on the basis of Chimaoru' s works and hope to stride a big step in MRFCW vehicle.The paper firstly discovers particularity of MRFCW to MRF , adopts big viscidity grease as baseoil and provides magnet field always using permanent magnet. Therefore, MRF is semi-solid all the time when vehicle is still, and then very simple MRFCW device is designed, so magnet particle' s anti-settling is solved. Dynamic model; are established on the basis of MRF bi-viscidity model including railway vehicles of 4 MRFCW(CCCC model), of fixed 1^st and 3^rd wheelsets, MRF coupled 2^nd and 4^th wheelsets (TCTC model), of coupled 1^st and 3^rd wheelsets, MRF fixed 2^nd and 4^th wheelsets (CTTC model), of fixed 1^st and 4^th wheelsets, coupled MRF 2^nd and 3^rd wheelsets(TCCT model) and traditional vehicle(TTTT), the dynamics simulating software of these models are programmed.Simulation shows that MRFCW vehicle possess higher critical velocity under the condition of MRF smaller yield stress, but bigger MRFCW lateral displacement, two-point contact occur in the meantime, critical velocity sharply descended in increasing yield stress, MRFCW lateral displacement decreased, yield stress increased continually, critical velocity descended slowly, but lateral displacement become bigger. Anti-hunting damper can raise critical velocity of MRFCW vehicle opposite traditional vehicle to speak. TCCT vehicle possess better dynamic performances in 4 kinds of MRFCW vehicles and it runs on the high-speed and quasi-highspeed track alternatively, this shows TCCT movement group possess better dynamic performances with comparison to its towing vehicle. In addition, influences of TCCT vehicle suspension parameter on critical velocity are analyzed and suspension parameters are optimized. Influence of wheelbase and diagonal difference of bogie, track condition on critical velocity, result demonstrates both former have little influence, but track condition has big influence. Besides, self-steered MRF radial truck is analyzed, but result proves that the bogie can' t decrease lateral displacement and it isn' t suitable in reality.TCCT vehicle possesses very high critical velocity and better dynamic performances when MRF yield stress and suspension parameter are appropriate by analyzing under the condition of not controlling MRF yield stress on the highspeed and quasi-highspeed railway, besides, TCCT vehicle possesses symmetrical simplified structure and the dynamic performances in front and behind.In addition, total wheel/rail contact calculation with divided rail outline method are raised. Under the condition of considering the displacement, bouncing, yaw, roll of wheelsets and displacement, bouncing, roll of rails, minimum gap between rail and wheel were calculated by the trochoid method and divided rail outline method, we can easily judge totally real contact states of the wheel/rail such as normal one-point contact, nonnormal one-point contact, two-point contact and wheel complete lift. Wheel/rail normal forces in the two contact point are respectively calculated by nonlinear Hertz contact theory, and then, result of simulation more close to reality on actual track. This method can also be applied in contact of wheel/rail in traditional vehicle dynamics.