Enlargement of out-of-round wheel profiles on high speed trains

Radial deviations from the ideal round shape of railway wheels and out-of-round (OOR) phenomena more generally have been a well known problem for a long time. Since the typical speed range of modern high speed trains have become higher and the newer building substructures "stiffer", in some vehicles both a disturbing, humming noise within the passenger compartment at high speeds and an increase of maintenance costs due to OOR wheel shapes can be observed. Measurements show that small radius deviations of some typical OOR shapes enlarge rapidly. In order to analyze the origin and the enlargement of OOR phenomena a vehicle-track model was developed to describe the short term system dynamics of an ICE-1 carriage. While running on an elastic track, disturbances by wheel radius deformations are assumed. In a second step, this model was extended by an iterative long term wear model to analyze the changes in radius deviations over a long operating period. Simulation results show that OOR wheel shapes cause extensive variations in normal forces on stiff substructures at high speeds. Under realistic operating conditions even a periodical wheel-rail lift-off can be observed. The normal force variations accelerate the wheel vertically and excite a bending oscillation of the wheelset axle which leads to lateral slip and lateral material excavation. Subsequently, the location and amplitude of the two excavation maxima-for the positive and negative maximum of the lateral slip-within the tread were investigated. Their locations change as a function of vertical track properties as well as of the excitation frequency which is the product of the rotation frequency of the wheel and the number of OOR periods over the wheel circumference (OOR order). It is shown that under specific operating conditions only some OOR shapes enlarge while others lead ro higher harmonic orders. (C) 1999 Academic Press.