Curve squeal of train wheels, Part 1: Mathematical model for its generation

A mathematical model is presented for the squeal noise generated by trains when traversing tight curves. Curve squeal is presumed to arise from latera l crabbing of the wheels across the rail head. This induces a lateral frict ion force acting at the contact of each wheel with the rail. An individual wheel then performs out-of-plane oscillations which are radiated and heard as squeal. This phenomenon is modelled by considering a flat round disc, wi th several out-of-plane modes, excited at one point along the edge by a dry -friction force (typically a stick/slip force) which is dependent on the di sc velocity. An iteration scheme is developed which gives the time history of the disc velocity. The iteration is straightforward and only requires th e impulse response (or the Green's function) of the disc and the functional dependence between friction force and disc velocity (friction characterist ic). The numerical simulations produce time histories that show transient p henomena, such as exponential amplitude growth and the onset of limit cycle s. The way these phenomena are influenced by some parameters, in particular the modal loss factors of the disc and its crabbing speed, will be examine d. Practical methods to reduce or eliminate curve squeal will be discussed. (C) 2000 Academic Press.