Zbornik radova Koridor 10 - Kirilo Savić

3rd International Scientific and Professional Conference
CORRIDOR 10 - a sustainable way of integrations
5.1 Maintenance of the upper part of the rail head
Corrugation of the upper part of the rail head is the common cause of the roughness of the rail head
running surface (Figure 10). The phenomenon is observed as a periodical sequence of bright ridges
and dark hollows on the running surface (International Union of Railways, 2002).
Constructive measures for corrugation reduction are continual rail support or decrease of space
between discrete rail supports (space between sleepers 60 cm, which increases rail bending
stiffness) and decrease of direct fastening system stiffness (recommended value of static stiffness of
rail pads is up to 200 kN/cm). Experience showed that corrugation doesn’t occur in the case of
continually supported rails, or it occurs with time delay with respect to discretely supported rails.
FIG. 10. Rail head slip waves - code number 2202 (photos taken on the New Belgrade – Zemun
section, 28 July 2004)
To eliminate rail head corrugation, grinding is applied (International Union of Railways, 2007). Today,
grinding (along with lubrication of outer rail in curve) is a part of the routine rail-care. Timely grinding of
surface roughness prevents its further development. The grinding effect is not permanent. After some
time, corrugation reoccurs.
It is considered that the noise decrease potential, based on the rail-care, is from 15 to 20 dB(A) with
respect to the track condition without rail-care (Schöch, 2008).
The objective of grinding strategy is rail life extension, reduction of total track and vehicle maintenance
costs, and reduction of railway traffic vibration and noise level. Preventive, corrective and cyclic
activities make the grinding strategy.
Preventive activities are undertaken before the defects are noted in the zones where their occurrence
is empirically expected. Preventive grinding is applied after laying new rails on the track before
acceptance of works. If the rail has to be replaced on the existing track, new rails can be grinded right
away or a few weeks after the assembly.
The target of corrective grinding is re-establishing regular longitudinal rail profile by removing
corrugation. Different railway managements set different limit values of corrugation depth for
application of corrective grinding. In spite of diversity of corrugation grinding strategies, it is generally
accepted in Europe that removing corrugation is essential and worthwhile.
Depending on the depth of the rail head damage, material is removed from the surface of the head in
order to allow the wheels to roll on the undamaged steel surface. By removing the material by
grinding, rail cross profile has to be maintained, so that the wheel/rail contact stresses are maintained
within acceptable limits and a stable ride quality is provided.
Sometimes corrugation appears combined with squats (Figure 11, right) mainly on straight lines and
curves of radius R ≥ 3000 m with high shear stresses, especially zones where accelerations and
breaking occurs (Schöch, 2008). If the defect is noticed in the initial stadium, it can be removed by
grinding and thus the rail replacement can be deferred. Only in some cases welding can repair this
defect. Rail replacement most frequently solves the problem, though.
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