Theory:

Thermal Expansion
The expansion of a substance on heating is called, the thermal expansion of that substance.
Uses of thermal expansion

1. Fitting the iron rim on the wooden wheel:

The iron ring is always made slightly lesser in diameter than that of the wooden wheel. Therefore, the iron ring cannot easily slip on it from the rim of the wooden wheel.

Image-of-Heating-and-cooling-an-iron-wheel.png

Wooden (Cart) wheel with an iron rod

When the iron ring is heated to a higher temperature, it results in the expansion in the size of the ring. Then, the hot ring is easily slipped over to the wooden wheel's rim. Coldwater is poured on the iron ring to contract in size and hold the wooden wheel tightly.

download (1).jpg

Iron ring fitted over to the wooden wheel

2. Riveting

Riveting is one of the most cost-effective and superior methods of fastening (join two parts). Rivets have a head on one side, a tail on the other, which is used to join two steel plates together. Hot rivet is forced through the hole in the plates. One end of the rivet is beaten to make a new rivet head. When cooled, the rivet will contract and keep the two plates tightly together.
 
riveting.jpg
Rivets
 
3. Gaps are left in between rails while laying a railway track.
An increase in temperature during the summer days causes expansion in rails. So, to permit expansion at the joints of the rails, a slight gap is provided in between the rails while fixing a railway track
 
shutterstock_149941751.jpg
Gap in the rails of the track
 
If such a gap is not left at the rail's joints, the track will get deformed due to thermal expansion. It will cause derailment of trains.
Reference:
https://pxhere.com/en/photo/854017