# Some problems in spring design

1. What is the characteristic curve of spring? What is its relationship with spring stiffness? What is the difference between the characteristic curve of constant stiffness spring and variable stiffness spring?
Answer: the relation curve between the spring load and its deformation is called the spring characteristic curve. The slope value of the characteristic curve reflects the stiffness of the spring. The characteristic curve of constant stiffness spring is straight line, while that of variable stiffness spring is curve.

Q: what is the purpose of spring strength calculation and stiffness calculation? What are the main factors affecting the strength and stiffness of cylindrical spiral compression (tension) spring?
Answer: the purpose of spring strength calculation is to ensure that the spring does not appear plastic deformation and fatigue damage when it works. The purpose of spring stiffness calculation is to ensure that the spring has the required elasticity.

Question 3: given that the external load of cylindrical spiral compression (tension) spring is f, try to analyze whether the spring deformation increases or decreases only by increasing the diameter of spring wire D, the number of effective coils n, and the medium diameter D?
Answer: under the action of F, the deformation decreases only when D is increased; when n is increased, the deformation increases; when only D is increased, the deformation increases.

Question 4: if the material, wire diameter, middle diameter and end structure of the two existing cylindrical spiral tension springs are identical, only the effective number of coils is different, try to analyze their strength and stiffness.
Answer: the strength of the spring has nothing to do with the number of effective coils n. The stiffness of the spring is inversely proportional to the number of effective coils n.