Railhead Damage

Introduction

The most common form of periodic damage on rails is corrugation. A well accepted mechanism for corrugation formation is shown.

The “wavelength-fixing mechanism” (WFM) is the dynamic behaviour that “fixes” both the wavelength and the position of corrugation along the track.

All types of corrugation whose cause has been identified to date are “constant frequency” phenomena, whose wavelength is:

λ = v/f

v= predominant train speed, f = frequency of the WFM

WFMs that have been identified to date lie in the range of about 50-1200Hz.  Examples of corrugation that occur from the following WFMs are considered here, in order of approximately increasing frequency:

Type of corrugation (WFM) Approximate frequency (Hz)
P2 resonance 50-100Hz
Rutting 50-150Hz
Trackform-specific 300-500Hz
Pinned-pinned resonance 450-1200 Hz

The “damage mechanism” causes the dynamic load (vertical or tangential) to result in an irregularity.  The most common damage mechanism is wear.A basic classification of corrugation is given here by considering different WFMs.

Because irregularities on a rail excite the dynamic behaviour, all corrugation can be reduced to some extent by ensuring a good longitudinal profile i.e. a “smooth” rail.  Practical limits on irregularities left by typical reprofiling operations are proposed in a European standard1.

1Railway applications – track – Acceptance of work – Part 3, Acceptance of rail grinding, milling and planing work in track, European Standard, EN 13231-3, European Committee for Standardisation, rue de Stassart 36, B-1050 Brussels, May 2006