(1)Load-deformation relationship

When the load on the spring: P and the deformation: δ are proportional to each other (in a linear relation), they are said to behave under "Hooke's law". The constant of proportion: k at this time is called the "spring constant". [Fig.1] shows a relationship between the load and deformation. The slope in this figure represents spring constant: k.

Examples of products designed and manufactured by taking advantage of this property include spring balances (scales for load weight measurement) and springs for safety valves operating at a certain required force.

(2)Springs with various loading characteristics

Contrary to the linear characteristics shown in (1), some of the springs' load and deformation are in a non-linear relationship.
Helical compression springs having non-linear characteristics of load and deflection are available in the following three types:

The functions of helical compression springs with non-linear characteristics are achieved when the line or lines and the seating surface contact each other as the load increases. This occurs because the coil spring position causes a change in at least one of the following design parameters: [1] coil diameter, [2] pitch, or [3] wire diameter.

The following table summarizes advantages and disadvantages of typical springs having the non-linear characteristics introduced earlier.

= Advantages and disadvantages of typical springs with non-linear characteristics