The Influence of Wheel/Rail Contact Conditions on Curve Squeal Noise: Experimental and Numerical Investigation

Curve squeal is still one of the most relevant railway noise problems in urban areas, disturbing thousands of inhabitants every day. In this paper, the variability of curve squeal generated by a modern low floor tramcar is investigated through noise and vibration measurements. Various wheel vibration modes are intermittently found to dominate the wheel vibration during a single curve negotiation. Curve squeal on the outer wheel is also highlighted. Dissimilar squealing patterns are observed in tramcars of the same type that negotiate the same curve. These findings reveal that curve squeal exhibits significant variability due to small changes in wheel/rail contact conditions, rendering the phenomenon, in some instances, highly unpredictable. Numerical simulations are carried out to give an explanation of these experimental findings. Curve squeal occurrence is predicted on both inner and outer wheels at frequencies close to the measured ones. Furthermore, it has been observed that a minor change in the track gauge can consistently influence the contact conditions in extremely tight curves. The contact between the flange back of the inner wheel and the check rail is found to alter the squealing frequencies predicted for a single contact point. It is shown that reducing the friction coefficient can mitigate the occurrence of curve squeal.