Experimental characterisation of railway wheel squeal occurring in large-radius curves

Abstract

Tonal squeal noise (i.e. the high amplitude singing of a railway wheel with pure tone components) is emitted by some trailing inner wagon wheels on heavy haul trains in 1000m radius curves on the iron ore export line in South Africa. Field measurements have shown that the trailing inner wheels that squeal are subject to predominantly longitudinal creepage with little to no lateral creepage. The longitudinal creepage acting at the contact of the squealing wheels exceeds 1%, which supports the likelihood of creep saturation and subsequently squeal due to unsteady longitudinal creepage in the large radius curves. Experimental modal analysis of the wheel types identified to be relevant to squeal has revealed that for each unstable frequency, two eigenmodes are likely to be important: one which has a large mode shape component at the wheel-rail contact in the circumferential direction and another which has a large mode shape component at the wheel-rail contact in the radial direction. A frictional self-excitation mechanism based on mode-coupling is favoured as being responsible for squeal excited in large radius curves.