An investigation of the influence of wheel/rail contact conditions on curve squeal

Curve squeal is produced by the self-excited vibration of a railway wheel, as a result of the contact phenomena taking place at wheel/rail interface during curve negotiation. In addition to the curve radius, squeal occurrence depends on the rolling stock characteristics, on the friction coefficient at wheel/rail contact and on the geometry of the coupled wheel/rail profiles. Real contact conditions can significantly differ from theoretical ones, when worn wheel/rail profiles and rail deflection under the loads produced by train transit are taken into account. This paper addresses the problem of estimating the influence of these parameters on the actual wheel/rail geometrical coupling and on the consequent possible occurrence of squeal noise. The analyses presented are based on two simulation steps. First 3D multibody simulations of a rail vehicle running in curve are carried out (track flexibility is accounted for, through detailed modelling of the ballasted track). Then squeal simulation is performed, which is based on linear wheel and rail models, coupled through a nonlinear contact model. Stability analysis of the open loop transfer function of the overall system yields the possible unstable frequencies while time domain approach can be used to estimate the limit cycle and the consequent noise levels.