Experimental and numerical investigation of tramcar curve squeal under varying wheel-rail contact conditions

The variability of curve squeal generated by a modern articulated tramcar is investigated through noise and vibration measurements at two sites and numerical simulations. Accelerometers on the leading wheels of the second car show that different vibration modes intermittently dominate the wheel vibration during curving, with squeal also detected on the outer wheel. To study low-adhesion conditions, the track is artificially wetted. A reduction of nearly 15 dBA in Single Event Levels is obtained after water application, but the effect disappeared after a few passes. A numerical procedure supports the experiments, combining vehicle dynamics simulations with a frequency-domain wheel-rail interaction model. Predicted squeal frequencies agree with those measured. Variability in contact parameters is considered by simulating numerous variants per scenario. Squeal occurs in over 90% of cases on the front inner and rear outer wheels, and in fewer than 3% on the outer front wheel. Simulations with varying friction coefficients are aligned with experimental findings in dry and wet conditions, suggesting that water-based friction modifiers can significantly reduce squeal. A parametric study on curve radius confirms the leading inner wheel as most critical, while also showing multiple squealing wheels, including those under flange contact.