Development status of spring technology

In mechanical and electrical products, there are many kinds of springs, mainly the following types.
1) It is mainly used in automobile, motorcycle, diesel engine and gasoline engine. This kind of spring includes valve spring, suspension spring, damping spring and clutch spring, etc. the consumption is large, accounting for about 50% of spring production. It can be said that the technical level of these springs is representative. They mainly develop in the direction of high fatigue life and high anti relaxation, so as to reduce the mass.

2) Large spring and leaf spring are mainly used in railway rolling stock, heavy truck and construction machinery. These springs are mainly formed by hot coil, which is an important aspect of spring manufacturing industry. With the development of high-speed railway and the upgrading of vehicle damping system, the hot forming spring technology as vehicle suspension has been greatly improved. This kind of spring mainly develops towards high strength and high precision to stabilize product quality.
3) The typical products of electronic and electrical spring mainly include motor brush spring, switch spring, camera and camera spring, computer accessory spring, instrument accessory spring, etc. In this kind of spring, leaf spring and anisotropic spring account for a large proportion, and different products have different material and technical requirements. This kind of spring is mainly developed in the direction of high strength and miniaturization.

4) Hardware springs mainly used in daily machinery and electrical appliances, such as mattresses, sofas, door hinges, toys, lighters, etc., are in great demand, but the technical content is not high, which improves the development opportunities for small spring enterprises. This kind of spring mainly develops in the direction of miniaturization.
5) Special springs, such as cradle springs for textile machinery, are required to have high relaxation resistance; springs for ladle gate are required to have high heat resistance; The suspension spring for mine vibrating screen requires not only high fatigue performance, but also high corrosion resistance. Therefore, rubber metal composite spring is used: in order to meet the comfort of vehicle driving, the air spring is used.

For the different cross-section suspension spring and valve spring, it is more reasonable than the circular section spring from the light weight, saving space, improving the comfort and improving the stress distribution of the spring. However, the cost of this kind of spring is higher than that of the circular cross-section spring due to its high price and complex manufacturing technology. Therefore, there is no sign that the spring with different cross-section will replace the spring with the spring with circular cross-section.

Development of spring design
At present, the widely used calculation formula of spring stress and deformation is derived from material mechanics. Without certain practical experience, it is difficult to design and manufacture high-precision spring. With the increase of design stress, many previous experiences are no longer applicable. For example, when the design stress of the spring is increased, the helix angle will increase, and the fatigue source of the spring will be transferred from the inside to the outside of the coil. Therefore, it is necessary to use the precise analytical technique of spring, and the widely used method is finite element method (FEM).
The characteristic of vehicle suspension spring is that in addition to sufficient fatigue life, its permanent deformation should be small, that is, the anti relaxation performance should be within the specified range. Otherwise, due to the different deformation of spring, the body center of gravity will shift. At the same time, the influence of environmental corrosion on its fatigue life should be considered. With the increase of vehicle maintenance period, the permanent deformation and fatigue life are required to be more strict. Therefore, high-precision design method must be adopted. The finite element method can predict the effect of stress fatigue life and permanent deformation of spring in detail, and accurately reflect the relationship between material and spring fatigue life and permanent deformation.

In recent years, the finite element design method of spring has entered the practical stage, and many valuable reports have appeared, such as the influence of helix angle on spring stress, the relationship between stress and fatigue life calculated by finite element method, etc.
Figure 1-8 shows a comparison of the stress calculated by the current design method and the finite element method. For springs of the same structure, under the same load, it can be seen from the figure that the stress of high stress spring with less effective coils or large helix angle is quite different between the two methods. This is because with the increase of the helix angle, the load eccentricity increases, which makes the outer diameter or transverse deformation of the spring larger, so the stress is larger. It can not be accurately reflected by the current design calculation method, but can be reflected by the finite element method.