Rivets are short ductile and cylindrical bars which are used for making a permanent mechanical joint. The process of forming a riveted joint is called riveting. A rivet is divided into 3 parts i.e., the head at one end, the tapered tail and shank, the portion between head and tail as shown in the figure.
As it is a permanent joint it cannot be disassembled without the failure of the machine component. The material of rivet should be tough and ductile. They are usually made of low carbon steel, nickel steel, brass, Aluminum, copper etc.
Physics Behind Rivetting-
The main function of a rivet is to make a connection that has the strength to prevent failure and tightness to prevent leakage.
For connecting 2 metal plates, firstly holes are punched and reamed. The plates are then separated to remove any burrs or chips. The cylindrical cold or red hot rivet is then inserted into the hole. Then the head is backed by hammer or heavy bar and then the die as shown in the figure and is placed against the end to be headed and the blows are applied by a hammer.
Force applied causes the shank to expand and fill the gap. The force applied deforms the tail plastically and forms the required shape. As the rivet cools down, it contracts. But the lateral contraction is slight and there will be longitudinal tension which holds the plates firmly together.
The cold riveting process is used for structural joints while hot riveting is used to make leak proof joints.