In fact, common springs have the following functions:

Even out shocks and absorb vibration.(e.g. springs of suspension in a vehicle)

Store and release energy (e.g. mainspring in clocks and watches)

Measure load(e.g. spring balance)

Control motion (e.g. springs in relief valves)

Springs can be classified in different ways. According to different materials, springs can be divided into metal springs and nonmetal springs. According to different shapes, they can be named as helical springs, disc springs, circular springs, plate springs and so on. According to different load bearing properties, springs can be defined as extension springs, compression springs, torsion springs and bending springs.

The materials of springs should have higher yield strength and fatigue strength, enough impact toughness and good heat treatment properties. The common materials for springs are: high quality carbon steel, alloy steels, stainless steels, copper alloys, rubbers and plastics.

Generally speaking, if a solid body recovers its original size and shape after deformed, it is said to be elastic. And if the deflection of an elastic body is proportional to the load, we can say, the body is linearly elastic and to satisfy Hooke’s law (formula 6-1).

       F=k·x      (formula 6-1)

       From the formula 6-1, we can get the conclusion that if the load is doubled the deflection is doubled.