Presentations and Papers
Summary - Mitigation of Wheel Squeal Noise in Queensland, New South Wales and South Australia
Presenter: David Anderson
Operational noise is an increasingly important issue for the rail industry. One source of operational noise is curve squeal, a high pitched screech noise that can occur when trains traverse curves in the track. Curve squeal is one of the Australian rail industry’s top noise mitigation priorities, on account of the acute levels of noise it generates, together with the large number of populated locations near curves.
This paper provides an overview of many of the curve squeal investigations and trials that have been carried out in Australia, and summarises the lessons learnt and the patterns observed. Observations suggest that the majority of curve squeal effects can be categorised into one of three types. Importantly, the techniques for investigation and effective treatment can differ significantly between the types.
The first type, referred to in this paper as “friction controlled”, is normally relatively moderate curve squeal associated with a small proportion of the passing rolling stock (typically less than 10% of axles). Noise can be very substantially reduced (or even eliminated) by changes in top of rail friction characteristics, either due to the deliberate introduction of a friction modifier, or due to changes in tribology that can be brought about by environmental conditions (fluctuations in meteorological conditions or the presence of foreign material, such as brake dust or pollen). It is the latter effect that causes one of the defining features of this category of curve squeal, namely that it exhibits what appears, on first inspection, to be random variation. For example, the same train may pass the same curve several times during a day with substantially different curve squeal outcomes.
The second type, referred to in this paper as “steering controlled”, is often relatively severe curve squeal associated with a very small (but more repeatable) proportion of the passing rolling stock (typically less than 2% of axles). Changes in top of rail friction characteristics provide little or no improvement, but studies have demonstrated a high correlation with poor steering. Wayside detection systems can be used effectively to identify the responsible wagons so that corrective maintenance can be carried out.
Finally, a third type is referred to in this paper as “systemic” as it involves curve squeal effects caused by a relatively high proportion of axles. In some cases, improvements can be obtained with relatively minor adjustments, such as lubrication practices. However, in other cases, noise reductions may only be possible with significant changes to the track and/or rolling stock configuration.
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