| In order to satisfy the requirements of the heavy-load and transrapid development in railway freight transportation, many novel-type vehicles have been designed and manufactured. In these freight vehicles, 3-piece bogie and frame bogie still are the two main bogies in common use. The bolster suspension is adopted in 3-piece bogie with sharp wedge friction damper, while axle-box suspension is adopted in frame bogie with flat wedge friction damper, both of which are belong to variant friction suspensions. The dry friction of wedge, therefore, has been become one of the main influential factors to freight vehicle performance.In the low-frequency motion of bolster suspension, the wedge friction jamming brings the severe disadvantage influence to the performance of laden vehicle, so the relative friction factor is usually controlled under 0.1. And the design of axle-box suspension takes account of wheelset locating, wheel-rail lateral force and travel stability, etc., the friction damper method is, therefore, one of the key technology in axle-box suspension. So far there are the three following friction damper methods with axle-box suspension: double-wedge damper, mono-wedge damper and Lenoir damper. Lenoir damper can be able to increase the contribution to the longitudinal stiffness in wheelset locating; meanwhile the laden springs do not take part in the friction damping. The biggest merit of double-wedge damper is the allowance of lateral jumping of wheelset in curve negotiation, and the wheel-rail lateral force is further decreased. But its contribution to the longitudinal stiffness in wheelset locating is very limited. Contrastingly, mono-wedge damper causes to go beyond the laden standard limit of wheel-rail lateral force in in curve negotiation.In this paper, the technical project of new-type articulated container flatcar proposed by a vehicle manufactory is taken as investigated subject. The technical project has the following features: the fore and rear flatcar articulated, the running gear with 2-axle and 3-axle bogie mixture, 4-vehicle unit constructed by traction rod. Because of the mixed axle-box suspension and bolster suspension, the stiffness of the axle-box suspensions in the second 3-axle frame bogie must be increased in order to satisfy the critical velocity requirement of 120km/h, in result that the running gear is formed the soft-hard-soft suspension stiffness characteristic. It is shown in rigid-flex coupling dynamical simulation analysis that the running gear with this stiffness characteristic has the three following disadvantage influences to the articulated flatcar: firstly, from the viewpoint of vehicle flexibility, the second frame bogie is not fit to be adopted the plane center bowl, since the small margin of critical velocity (sphere center bowl, 150km/h; whilst plane center bowl, 130 km/h). Secondly, tare comfort index decreased (Wz approached to 4.20), at the same time the lateral acceleration is on high side(≥0.5g)in the middle laden vehicle. In the trial calculation of running gear suspension stiffness decrease, the comfort index has shown to be improved remarkably. Finally, since the relative small contribution of the end bolster suspensions to the container flatcar's rolling stiffness, the lost-load of the side bearing on the carry-on side of the articulator is caused to be appeared, and result in the impulse side-bearing forces are presented successively.There are the following novelties in this paper's investigation: Firstly, according to the (quasi) equilibrium principal, the simple model of variant friction suspension is established based on the interaction analysis of wedge. Secondly, for the strong lateral coupling of the articulated flatcar, the modeling mythology of rigid-flex coupling system is adopted.
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