# Calculation formula of spring characteristic variable

The effect of spring deformation energy on tension and compression spring is as follows:
For torsion spring:
The relation curve between load f (or T) and deformation f (or ч) is called the characteristic line of spring. There are three types of characteristic lines of spring
(1) Linear type;
(2) Increasing type;
(3) Decreasing type;

The ratio of load increment DF (or DT) to deformation increment DF (or D ч), that is, the load required to produce unit deformation, is called the spring stiffness. For compression and tension springs, the stiffness is f = DF / DF, and for torsion springs, t = DT / D ч.
When designing buffer or vibration isolation spring, the deformation energy of spring, that is, the energy absorbed and accumulated after loading, should be calculated.

G — shear modulus of spring material
E — elastic modulus of spring material
K —— proportional coefficient, which has different values for different types of springs. It indicates the utilization degree of materials, so it is also called utilization coefficient.
It can be seen from the formula that the deformation energy is inversely proportional to the modulus G and E. therefore, a lower modulus is beneficial to the higher deformation energy required. Similarly, low modulus is beneficial to spring stiffness. The deformation energy is directly proportional to the square of the maximum working stress. Increasing the stress means that the material should have a high elastic limit, and a high elastic limit also corresponds to a high modulus. But the stress is in the form of square, so it plays a decisive role in the selection of materials.
In the design of spring, in order to obtain large deformation, it can be seen from the equation that the volume or stress of spring material can be increased, or both can be increased.