A nonlinear FE model for wheel/rail curve squeal in the time-domain including acoustic predictions
Résumé
Squeal noise of rail-bound vehicles frequently occurs in curves with a small radius and is a major nuisance for transport users and local residents. For the quantification of squeal intensity, a complete vibro-acoustic analysis is developed in this paper. This complete analysis requires time-domain analysis able to introduce non linearities leading to obtain dynamic saturation at the contact zone and a computation of sound radiation of the whole system. For time-domain analysis, a finite element (FE) formulation around the stationary position in an Eulerian reference frame is derived with a fine discretization of the contact surface combined with unilateral and Coulomb friction laws. Appropriate numerical techniques and reduction strategies are then used in order to solve the non linear discrete equations in dynamic self-sustained conditions. Both the transient approach and linear stability analysis are carried out. For sound radiation calculation, the contact forces calculated from wheel/rail contact model are then used for the calculation of squeal noise by using a coupled fluid-structure resolution based on boundary element method for the acoustic part and finite element method for the structural part. Results are first discussed in terms of unstable modes which are consistent between transient and stability analysis. Transient calculation shows that the apparent global friction coefficient during stick-slip cycles is slightly smaller than the constant local friction coefficient, and a dynamic saturation curve with hysteresis considerably different of the quasi-static curve. Finally the sound radiation calculation showed that the sound power radiated from the wheel is dominant with harmonics coming from the contact non linearities.
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