Contact Forces and Running Stability of Railway Vehicles

Running stability, intended here as stability against derailment, is governed mainly by the magnitude of the contact forces, which are effective only if they are able to prevent the wheel lifting from the rail. Contact-force measurement methods are still necessary for the acceptance of the vehicles, especially for those designed for high speeds. However, they are affected by uncertainties in the results which depend on the measurement techniques. In this paper, we analyse different measurement systems, both on-board and track-side, and their ability to meet requirements coming from design, operation, and maintenance. We examine measurement principles, advantages and disadvantages of the methods characterized by sensors on the wheel, on the axle, and on both or on the rail. In particular, we consider the uncertainties that arise from the position of the wheel/rail contact point, from the effects of speed and temperature on the strain of the wheel and the overall uncertainties reported in the literature by the authors. The quantitative knowledge of the uncertainties can guide manufacturers in the choice of a cost-effective method for use in acceptance testing and can guide researchers in seeking directions for improvement.