Although the spring finite element analysis method has been put into practice in the countries with higher spring technology level, although China has developed this technology, it has not yet formed a practical model.
In addition, the optimization design is introduced in the process of spring design. The structure of spring is relatively simple, the function is simple, and the parameters that affect the structure and performance are few. Therefore, the designer used the analytic method, graphic method or graphic analysis method to seek the optimal design scheme for a long time, and achieved certain results. With the development of computing technology, the optimization design of nonlinear programming with computer has achieved good results (see Chapter 10, section 11).
Reliability design is a series of analysis and design techniques used to ensure the reliability of the designed products. Its function 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 methods. Spring design has made some progress in the use of Reliability Technology (see Chapter 10, section 12). However, data development and accumulation are needed for further improvement.
With the development of computer technology, various versions of spring design programs have been compiled at home and abroad, which provides convenient conditions for spring technicians to develop and innovate. The arc clutch spring and drum suspension spring which are difficult to design are developed by using the design program.
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, which depends on experimental data. If the number of turns calculated according to the current design formula, the stiffness of the spring made is smaller than the design stiffness, and the effective number of coils should be reduced to meet the design requirements. The design trends of current mass production products are shown in table 1-5, taking the requirements of maximum working shear stress and fatigue life as examples.
Table 1-5 design trend of spring in mass production
Important requirements related to maximum working shear stress of product type
General mechanical structure spring static load 900 ~ 1200Mpa
Dynamic load of 900 ~ 1000MPa starts to meet the requirements of fatigue life
Spiral torsion spring 900 ~ 1000MPa
Engine valve spring
Mercury oil nozzle spring 950 ~ 1200Mpa
(generally 1100 MPa) the fatigue life requirement is 2.3 ×, and the reliability is more than 90%
Automobile gearbox and clutch spring 1100 ~ 1200Mpa
(generally 1100 MPa) with relaxation requirements, fatigue life requirements (3 ~ 10) × times
The static load of truck brake spring is 1100 ~ 1200Mpa, with relaxation requirement
Requirements for corrosion fatigue life of 1100 ~ 1200Mpa
(3 ~ 5) × times
Suspension spring of new high speed locomotive 1000 ~ 1200Mpa
Note: the above data are from the product drawings and information of the leading professional companies in the world