A. Why do springs break in use?
a. If the mandrel is too small or the spring is used horizontally, the spring and the mandrel are worn and broken;
b. When the mandrel is too small / the assembly surface is not smooth / the parallelism of the positioning surfaces at both ends is poor, the spring will be compressed and twisted, and local high pressure will be produced to fracture;
c. If the spindle is too short and the end is not chamfered, the spring will break due to friction and wear;
d. The use of foreign bodies between the coils reduces the number of effective coils, resulting in high stress and fracture;
e. The spring is used in series to make it bend and exceed the length of mandrel or countersunk hole, or because of the small difference of spring itself, the weak load will bear greater compression and fracture;
f. When the maximum compression is exceeded, the spring will break due to high-efficiency stress;
g. The spring material is not uniform, or the impurity content exceeds the standard, resulting in stress concentration fracture;
h. Over burning, corrosion, high hardness and over extension of spring will reduce its tensile strength and cause fracture.
B. Why does spring show “insufficient elasticity” in use?
a. The design and manufacture parameters of non-standard spring are unreasonable: only pay attention to the outer diameter, inner diameter, length and other parameters, often ignore the size of wire cross-sectional area and pitch, resulting in insufficient elasticity;
b. Unreasonable selection of standard spring: due to the low price of the drawing, the lighter load type is selected, which can not bear the heavy load, resulting in insufficient sensory elasticity;
c. Wrong spring quality grade: unintentionally or intentionally use ordinary spring as high-quality spring or imported spring, resulting in insufficient elasticity;
d. The elasticity is reduced or even lost when it is used beyond the specified temperature;
e. The spring wire itself is soft, or the quenching temperature of the spring is low or the holding time is not long enough, or the tempering temperature is too high and the time is too long after forming the spring, which leads to the tensile compressive strength against the elastic force is not enough.