Application and technology development of spring
In mechanical and electrical products, there are three major types of springs with the largest consumption
1) The spring of motor vehicle is mainly automobile;
2) Spring of electronic products based on daily electrical appliances;
3) The spring of optical device mainly composed of camera, copier and camera.
Motor vehicle springs are mainly developed in the direction of high strength to reduce mass; electronic springs are mainly developed in the direction of miniaturization; and the springs of optical devices are mainly developed in the direction of both high strength and small shape. The corresponding spring design method, material and processing technology have been developed.
1、 Development of spring design
At present, the widely used calculation formula of spring stress and deformation is derived from the mechanics of materials. 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 With the increase of design stress, many previous experiences are no longer applicable.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, precise analytical techniques must be used. 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 the center of gravity deviation of vehicle body will occur. 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 spring stress on fatigue life and permanent deformation in detail, and can accurately reflect the relationship between material and fatigue life and permanent deformation of spring.
In recent years, the finite element method 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.
For the spring with the same structure, under the same load, the stress of the dynamic 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 and the eccentricity of the load, the outer diameter or transverse deformation of the spring is larger, so the stress is also larger. It can not be accurately reflected by the current design calculation method, but can be reflected by the finite element method.
In addition, the optimization design is introduced in the spring design process. The spring structure is relatively simple, the function is simple, and the parameters affecting the structure and performance are saved. Therefore, the designer has long used the analytic method, graphic method or graphic analysis method to seek the optimal design scheme, and achieved certain results. With the development of computing technology, the optimization design of nonlinear programming with computer has achieved good results.
Reliability design is a series of analysis and design techniques used to ensure the reliability of the designed products. Its task is to make the designed products reach the specified reliability target value on the basis of predicting and preventing the possible failure of products. It is a supplement and improvement of traditional design method. Spring design has made some progress in the use of reliability technology, but to further improve, it needs data development and accumulation.
With the development of spring application technology, many new problems need to be paid attention to and solved by designers. For example, the influence of material, high pressure and shot peening on fatigue and relaxation properties is difficult to calculate accurately in design; it depends on experimental data; and if the number of turns calculated according to the current design formula is smaller than the designed stiffness value, the effective number of coils needs to be reduced to meet the design requirements.