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Regardless of the mode of transportation, directional changes generate greater forces on the infrastructure as a result of the lateral load transfer and of the respective steering forces in the vehicles. In the case of Railway transportation, a concentrated damage occurs in the rail at the initiation of the turning maneuver, whose magnitude depends on the bogie´s yaw stiffness and on the level of friction at its centre plate. To mitigate such rail-damaging effects, some new designs have been proposed and used for the bogies´ wheelset. However, no new designs for the centre plate have been used. In this paper, a review of the causality for the forces arising during Railway Vehicle's turn negotiations, is presented, including the description of a modeling framework to analyze the influential Parameters for determining the magnitude of such forces.
Turning maneuvers performed by railway cars, imply the development of steering forces at the wheel-track interface, whose magnitude depends on a set of properties and operating conditions related to the vehicle and to the infrastructure, including track´s turning radius and vehicle´s yaw resistance.
Yaw resistance integrates two components. On the one hand, there is the yaw stiffness, as a function of the different vehicle suspension components. On the other hand, there is the dry friction at the centre plate. Such yaw resistance of the car´s bogies, has a two-contradictory effect on railway performance, as a flexible bogie reduces the level of the steering forces, but at the same time, it increases the probability of having hunting instability. A variable yaw resistance, with high values at straight track segments and low values at curved tracks, seems to be an interesting design. In this paper, a variable friction Center plate is proposed, aiming at maximizing the yaw resistance on straight track segments, and minimizing such resistance at curved tracks. The conceptual design of this device is described, together with its ability to reduce the yaw torque. Benefits of this device, regarding the transport energy consumption and the magnitude of the steering forces, are estimated on the order of 1 to 10, when comparing the proposed design with the standard center plate design.