Aren’t the adjustment switches some really nice devices? On one side we have rails subjected to thermal stress, tending to seriously expand or contract due to the environment temperature, and on the other side no stress is transferred. Smart! We cut the rails in that funny shape, grease the clamp plates, and we let the…
Disclaimer – this includes a back-of-the-envelope calculation. Take it with a pinch of salt. If a steel beam is exposed to an increased temperature, it will tend to expand. If there is nothing to oppose that expansion, then the beam increases in length by ΔL. If, however, the beam’s ends don’t allow this expansion then…
This is the link to the second article I wrote together with Levente Nogy – “Rail thermal force calculations for jointed track” – and published in the Permanent Way Institution Journal – Vol 135 Part 2 (April 2017). Article 2
The location of the stress transition zone is not only limited to the extremities of a continuous welded rail (CWR) track, the case presented in a previous article – CWR stress transition zone. A stress transition zone may also be present between two fixed zones, inside the CWR. These internal stress transition zones are shorter…
Rail steel has a considerably higher carbon content (0.7-0.8%), and hence is more brittle than mild steel. A variety of stress concentrating defects in rails, combined with the alternating loads from the passage of traffic, can produce slowly propagating fatigue crack. When this crack attains a critical size it causes an almost instantaneous brittle fracture…
(prelude to a new PWI Journal article) A stress transition zone is any section of continuous welded rails (CWR) where the thermal force is variable, the longitudinal resistance (p) is active and rail movement occurs due to rail temperature variations. The most common (and well known) location of the stress transition zone is at the…
ΔG = αLΔT°. Free expansion For a free thermal expansion jointed track the rails expand and contract freely and the track components do not provide any resistance to oppose this rail length variation. The joint gap varies linearly relative to the rail temperature. The figure below presents the joint gap variation for a jointed track formed…
The thermal behaviour of the jointed track can be analysed throughout a full annual temperature variation and used to define the joint expansion gap variations. The joint gap varies between the maximum value and zero and this is related to the way the rails are allowed by the track resistance forces to contract and expand in…
This is the presentation I gave to the West of England Section of the Permanent Way Institution:
I feel very honoured and proud to see the article “An introduction to rail thermal force calculations” I wrote with my friend, Levente Nogy, published and featured on the front cover of the Journal of the Permanent Way Institution.
A railway track blog 