Rough Grinding and Rolling Contact Fatigue (RCF)
systems have relatively light axle loads, and the residual post grind roughness
due to rail grinding therefore can take considerable time to diminish
completely. This residual roughness can contribute to excessive vehicle noise
and other potential issues.
Research is needed to understand if
and at what level rough grinding can contribute to the development of excessive
vehicle noise and near surface fatigue cracks. Secondly, research is needed to evaluate the
tradeoffs between rougher or finer stones in terms of the conflicting demands
between productivity and surface quality (including roughness, noise, vibration
and potential RCF and corrugation development).
whether high productivity, coarse grinding stones and the resulting surface
finish of the rail contribute to rolling contact fatigue in a rail transit environment.
A secondary objective is to evaluate the
productivity tradeoff between coarse high material removal grind stones and
fine less material removal grind stones.
transit systems throughout North America grind rail on a regular basis. While
some focus on noise and rail corrugation, for others there are strong concerns
about rolling contact fatigue. Most are
interested in the most cost effective approach to alleviating those issues and
are unsure what level of surface finish is worth pursuing at a higher
designs and rail grinding strategies that optimize the amount of metal removed
to treat surface condition problems have seen much attention in the last two
decades. More recently there has been
exploration of the impact of rail grinding on noise and rail corrugation,
though this is in its infancy. Those
efforts now underway could also be leveraged to explore the concern about
surface fatigue cracking. Major rail grinding programs are underway in cities
such as New York, Toronto, San Francisco, Seattle and Vancouver that can be
called upon to support this investigation.
Complementary work on rail
grinding quality indices is being conducted in collaboration with the
University of Manitoba and in economic evaluations through an International
Collaborative Research Initiative on RCF and wear of rails and wheels. Metallurgical work is ongoing through an FRA
sponsored project to “Qualify Rail Surface Damage” that involves the collection
of dozens of rail samples from industry for sectioning to compare visible
surface damage with internal damage. It
would be relatively cost effective to add the required rail samples to the
ongoing work stream.
review of the problem should be undertaken, looking not only to experience in
North America, Australia and Europe but also across other industries if
appropriate. Review of academic and theoretical work in this field (e.g.
modeling of plastic deformation, crack initiation and propagation) should be
It is expected that both
laboratory and field testing would follow. While disc on disc testing is
possible, scaling effects are always problematic and probably insurmountable
for this study. And while full scale testing
is possible, it is both expensive and possibly inconclusive since a realistic
loading environment (e.g., combination of powered and non-powered wheels) that
reflects the true operating conditions is difficult to define and more
difficult to replicate. Accordingly, the
problem would best be understood through analysis of in-service rail samples.
One or more railroads willing to
remove rail samples with a variety of rail surface finishes both immediately
after grinding work and after some level of accumulated traffic would be
Cracks on any collected samples
would be sized using eddy current measurement and then metallurgically
sectioned to look for tearing and cracking in the grinding furrows and evidence
of plastic flow over furrows.
Other field testing would include
grinding and monitoring two curves of similar makeup – one with high material
removal grinding and one with acoustic grinding. Monitoring would include visual inspection
(enhanced with magnetic particle highlighting as required) and eddy
current. A portable single probe system
such as the Elotest can be used to size single cracks for the detailed
If it is determined that rough
grinding is indeed the contributor to rolling contact fatigue, then a
cost-benefit analysis is needed. While rough grinding is more productive and
less costly on a pass-mile basis, if it contributes to RCF formation then the
initial savings might be offset by the more frequent and heavier grinding
required to remove surface defects arising more rapidly. A potential hybrid
approach using first coarse and then fine stones to grind rail could be
is likely to become part of a widely used rail grinding guideline by transit
agencies. As such it will impact all
agencies but clearly those more invested in maximizing the effectiveness of
their rail grinding programs will take stronger notice of its impact. Rail
grinding companies and wheel-rail consultants will be active in assuring its
application to transit properties.
Increasing focus on the contribution of rail grinding to the elimination of, and contribution to, noise and vibration have raised the profile of rail grinding and current practices are being questioned. The push to finer grit stones is tempting but the cost of doing so is not inconsiderable. Answering the question posed by this RSN will provided a needed input to resolving the issue.
|Sponsoring Committee:||AR050, Railroad Infrastructure Design and Maintenance
|Research Period:||12 - 24 months|
|RNS Developer:||Eric E. Magel, Principal Engineer, Rolling Contact Fatigue, National Research Council, Canada, firstname.lastname@example.org, +1 250 317 0205 Mark Reimer, Director of Projects, Advanced Rail Management Corporation, Indialantic, Florida, email@example.com, +1 204 792 7555|
|Index Terms:||Rail grinding, Rolling contact, Maintenance of way, Alternatives analysis, |
Maintenance and Preservation