Curve squeal of modern tramcars: comparison between independently rotating wheels and solid axles

Curve squeal noise is still one of the most serious problems related to the operation of trams in urban networks. Several mitigation solutions have been proposed in past research, usually dealing with friction modifiers or damping elements installed on the wheels or on the rails. In this paper, the role of the bogie architecture on curve squeal occurrence is investigated. Vehicle dynamics simulations and a wheel/rail coupled model in the frequency domain are used to compare curve squeal predictions in case of Independently Rotating Wheels (IRW) and Solid Axles (SA). The SA configuration results in higher longitudinal creepage compared to IRW. This modifies the transverse creep curve, making this design solution less susceptible to curve squeal induced by falling friction. Despite the well-known improved curving behaviour in sharp curves, the IRW architecture has been found to be more prone to curve squeal compared to the SA tramcar.