Impact analysis due to multiple wheel flats in three-dimensional railway vehicle-track system model and development of a smart wheelset

Wheel flats can create high-magnitude impact forces at the wheel/rail interface, these can induce high levels of local stress leading to fatigue damage, and failure of various vehicle and track components. With demands for increased load and speed levels, the issue of a strategy for effective maintenance and in-time replacement of defective wheel-flat-containing wheels has become an important concern for heavy haul operators. A comprehensive coupled vehicle/track model is generally used to predict the impact forces and the resulting component stresses in the presence of multiple flats. This paper considers the dynamic impact responses due to the presence of multiple flats. The characteristics of the bounce, pitch, and roll motions of the bogie due to a flat on a single wheel are investigated. The effect of multiple flats on the peak acceleration of a wheel is investigated for different sizes and relative positions of the flats, i.e. in-phase and out-of-phase conditions. This paper further presents the development of a smart wheelset for the detection of wheel flats for two different load conditions; it is based on a derived relationship between the peak wheel acceleration, vehicle speed and flat size.