Although the spring industry is a small industry in the entire machinery manufacturing industry, its role cannot be underestimated. With the continuous deepening of the degree of openness, the imported machinery manufacturing, automobile, petrochemical and electric power and other industrial equipment have been widely used in China. Correspondingly, we also understand some new parts with superior performance, and the multilayer wave spring is a relatively new elastic element.
The ordinary single-layer wave spring is an elastic element with several peaks and valleys on a metal ring. The multi-layer wave spring seems to be a combination of several ordinary single-layer wave springs. The difference is that it is not simply superimposed, but is processed through a special continuous winding process.
2. Classification and working principle
Wave springs are usually divided into: a, single-layer wave springs,
Single-layer closed type “O” shape wave spring,
Single-layer open type “C” shape wave spring;
B, multi-layer peak-to-peak (series) wave spring;
C, multi-layer stacked peak type is also called nested type (parallel type);
Single-layer wave spring: suitable for short-displacement and medium-low elastic working conditions, with good reliability and high working principle: the wave spring has the accuracy of the double working principle of cylindrical spring and disc spring.
Multi-layer wave spring counter-peak type (series type): The elasticity value is inversely proportional to the number of turns. It is mainly used in: large displacement, medium and low elasticity requirements, and is a substitute for cylindrical springs. Nested type (parallel type): The force value of the spring is proportional to the number of turns. While generating huge elastic force, it can also maintain all the precise characteristics of the wave spring. In many occasions, nested (parallel type) wave springs can be used. Instead of disc springs.
3. The influence of materials and temperature on fatigue failure
As far as the same material is concerned: the material with fine grain structure has higher yield strength and fatigue elasticity than the material with coarse grain structure; the fatigue life of the surface-strengthened material is much higher than that of the unstrengthened material; the surface of the material The smaller the roughness, the smaller the stress concentration, and the higher the fatigue strength; the fatigue life of materials with metallurgical defects will also be greatly reduced, causing the spring to cause fatigue failure in advance.
The wave spring produced by ordinary spring steel has good elasticity, electrical conductivity, and strong wear resistance. The fatigue failure of the spring is within the normal range at normal temperature (temperature ?200?). However, as the temperature increases, the elasticity of the spring will gradually decrease, and the failure phenomenon will increase significantly.
Wave springs made of stainless steel have high fatigue life and good relaxation resistance. At the same time, stainless steel has extremely high corrosion resistance and non-magnetic properties. Generally stainless steel temperature is greater than 400? Failure phenomenon occurs when the special stainless steel has extremely high corrosion resistance and non-magnetic properties. The working temperature of the special stainless steel reaches 650? It also has high resistance to relaxation and fatigue, and is a material that cannot be replaced in special working situations.
4. Prevention of fatigue failure of wave spring
The following is the formula for calculating the load and stress of the wave spring. We can use the formula to design the wave spring stress in a low-stress state, and the fatigue failure of the wave spring is not obvious.
(1) Calculation formula for single-layer wave spring: f=PKDm/Ebt3N4*ID/OD
(2) Multilayer series or peak-to-peak wave spring calculation formula;
(3) Multi-layer stacked peak type, also called nested type or parallel type wave spring calculation formula;
where: f=displacement; P=load; K=multi-turn coefficient; Dm=average diameter;
Z=number of turns; E=modulus of elasticity; b=material width; t=material thickness;
N=wave number; ID=inner circle diameter; OD=outer circle diameter; S=bending stress;
Through the fatigue test of the wave spring, we found that the fatigue life of the wave spring is far more than 500,000 times, and the normal is more than 1 million times. Our company produces outer diameter D=137mm, inner diameter d=125mm, thickness t=0.8mm, wave height H=6mm, when working displacement is 3.5mm, working force value F=1225N. This specification wave spring has passed a petrochemical enterprise for three years With more use, the spring has a life span of 1.8 million times, and some life spans are even higher.
Therefore, when designing the wave spring, we should choose a reasonable wave height and material thickness according to the load and displacement to effectively control the stress of the wave spring, and use the adjustable wave number to more effectively control the fatigue failure of the wave spring.