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.
