Abstract
The frictional issues during motion of the axis-wheels assembly occurring in contact wheel–rail and in bogie bearing were studied. The influence of greases upon friction therein was also considered. The lateral dynamic behavior of the four-axle freight wagon model with two-axle Y25 bogies equipped with swing bolster was analyzed. Simulation models of such a wagon with bogies with and without swing bolsters were elaborated for calculations considering the nonlinearities of wheel–rail contact geometry and nonlinear methods of bogie stability. In these two options, the cases of empty and fully loaded wagon bodies were considered. The lateral dynamic models with 22 and 24 degrees of freedom were considered to determine the nonlinear critical speeds of a freight wagon. It was found that the resistive torque in bearings of the assembly studied varied nonlinearly with wagon speed. During motion along the curve track, values of such a torque can be higher by 50% in case of the wheel under overloading and lower by 50% in case of the wheel under underloading, respectively, compared to those obtained during motion along straight track.
Highlights
Most freight wagons currently in use in Europe have practically one suspension stage and they are designed to travel at speeds of 100–120 km/h on straight track
The movement of a wagon model was viewed as stable if the lateral oscillations of wheelsets decreased and vanished following discontinuation of the excitation, such as in the case presented in the Figure 6 for constant speed equal to 38 m/s
The obtained values of the resistive torque versus wagon speed in the tapered roller bearing are presented in Figure 10, for the case of motion along the straight track (Fz = 0.5Q), Lubricants 2022, 10, x FOR PEER REVaInEWd along the curved track for the wheel under overloading (Fz = 0.75Q) and 1u7nodfe2r0 underloading (Fz = 0.25Q)
Summary
Most freight wagons currently in use in Europe have practically one suspension stage and they are designed to travel at speeds of 100–120 km/h on straight track. Increasing this speed for existing designs would be possible, for instance, by changing the stiffness parameters of the first stage suspension This would mean agreeing to a very large increase in the stiffness of the wheelset guidance in the bogie frame. The paper presents the results of simulation studies necessary to assess the validity of the use in the construction of two-axle freight bogies a swing bolster and introducing the second stage of the suspension of the freight wagon. An example of such a concept are the prototypes of the Y25 family of freight bogies built in Poland in the years 1993–1995, in which a swing bolster was introduced.
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