Zbornik radova Koridor 10 - Kirilo Savić

3rd International Scientific and Professional Conference
CORRIDOR 10 - a sustainable way of integrations
compressive layer, especially in new or newer rails that are exposed to adverse wheel/rail contact
conditions by poor track geometry, wheel geometry irregularities, bogie characteristics, etc.
It is especially important to note that under poor wheel/rail contact conditions (due to excessive shear
stresses), new higher strength rails may be more susceptible to the growth of checking cracks into the
rail head. The new higher strength rails are more resistant to plastic flow and hence work hardening
and the development of a deep compressive residual stress layer. This must be taken into account
when using the new higher strength rails.
Unfortunately, the very effective lubrication of the outer rail in curves (used on railways in order to
decrease lateral rail wear of the outer rail and wheel flange wear) stimulates a growth of head
checking rail defect. Lubricant penetrates in to the fissures (together with impurities and atmospheric
water) and the pressure from the wheel on fissure walls lead to faster advancement and dilatation of
fissures (Figure 14). For example, the visual inspection on Serbian railways shows a progressive
development of HC defects due to the penetration of lubricant mixed with impurities and water in the
fissures on gauge corner. Also, lubricants have a negative influence on visual inspection, especially in
tunnels because of reduced visibility and disable the use of penetrates.
FIGURE 14. Fissure propagation due to lubricant penetration
It is of particular importance to note that some controlled rail wear is preferable to having no wear.
Consequently, the factors that reduce rail wear (reduced track curvature, very effective lubrication, -
higher hardness/strength steel, wheel and rail profiles designed to reduce wear) contribute to the
growth of the fatigue cracks.
3. TREATMENT OF DEFECTS DUE TO ROLLING CONTACT FATIGUE
The rail infrastructure managers have to correctly choose the quality of rail steel. A key parameter in
this selection of rail steel grades is the procurement and maintenance cost of the rails. It is important
to consider whether the higher capital costs of 350 HT, 350 LHT and 320 Cr grades are offset by
longer service life and/or lower maintenance outlay [8]. Figure 15 shows the recommendations for use
of normal and hard steel grade rails in accordance with [8].
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