Kiskon sivukulumisen vaikutus kaluston suistumisriskiin

Increasing rail side wear limits would decrease the need for rail change and rail
grinding which would bring on great financial benefits. Side wear in rail, however, changes track gauge and rail profile shape, which immediately affects
train movement. It is typical that in curves rail wear occurs on the side of rail
head and in straight track on top of rail. As a phenomenon, rail side wear is more severe than rail top wear since strong rotational creep forces will arise in the contact between wheel flange and rail side.

The aim of this project was to observe the validity of current rail side wear limits
in Finland. It was also important to look at potential derailment risk caused by
strong rail side wear, especially in good quality track sections with high
velocities. The project also included evaluation of train passenger inconvenience
and its dependency on rail side wear. Literature review was made to find out how
rail side wear limits in Finland compare to other countries. It was found out, that
the limits in Finland are quite strict.

In calculational study, rail side wear was consistently noticed to weaken wheel-
set guiding properties, which increases the amount of wheelset side movement
in curves. However, due to rail side wear, track clearance has also grown, so
there is more space for the wheelset to move laterally without flange contact.
Flange contact always causes a high lateral force, which increases the value of
Y/Q and therefore the risk of derailment.

Based on simulation results, it was concluded that rail side wear limits in Finland
can be increased several millimeters. Rail side wear was not noticed to cause
any significant change on train derailment risk or passenger inconvenience.
Train guidance properties are mainly affected by the shape of rail profile, not the
amount of rail side wear.

Unstable behavior of a vehicle is one obvious reason for higher derailment risk.
In a large number of simulations made in this project, unstable behavior was
observed a few times. Reason for that, however, was not the amount of side
wear in rail directly, but rather the poor interoperability in the combinations of
rail and wheel profiles.

Rail side wear limits in Finland can be increased, but it requires some control
measurements to be done in both vehicles and track, to be sure that the Y/Q
value stays low enough. Along with rail wear, the rate of rail wear may also rise,
and it is good to be prepared for that. This phenomenon, however, is highly
dependent on the combinations of wheel and rail profiles. Therefore, the rate of
rail wear varies in different track sections.