Each rail is connected to one another by a spacing between them. The small spaces provide space for the train to easily move over the summer, and the constant friction between the rail wheels and rails during the summer causes the tracks to expand and get out of the heat. This can cause train derailment and is therefore dangerous. There are gaps between the length of the railway tracks to allow for expansion
All solids expand in a certain volume (increase in size) when exposed to high temperatures – and shrink when cooled. This is a basic thermodynamic fact: when the molecules are always vibrating and heated, this vibration increases, extending the bulk of the material slightly. When the principal volume of a solid is linear (as in rails) we speak of linear thermal expansion. This effect can be modeled with a constant coefficient for ambient temperatures. The rails are made of steel and have a linear thermal expansion coefficient of 12 µm / (m · K). That is: each meter train extends 0,012 millimeters per degree of temperature rise (kelvin and centigrade are the same “size”, and relative to what we consider to be a measurement).
Practically: We use 90-degree rails at 15 ° C. What is the length of the train during a hot, 40 ° C summer day? 12 × 90 × (40 – 15) computing gives 27000 µm, that is, the 2.7 cm rails that must be counted when laying tracks, extending beyond the dilation clearance, without causing each other to start pushing, and possibly rails. Dilation clearances between rails are best calculated for the most common temperature at the locale.
Modern railways use continuous soldering rails and track expansion equipment at regular intervals (and usually at the beginning and end of bridges, tunnels, and other structures) to prevent maintenance problems caused by rail thermal expansion and increase rolling comfort.
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