The characteristics and design principles of toy springs:
With the development of the mold industry, the number and varieties of special-shaped section steel wire mold springs are increasing. Special-shaped section mold springs have the characteristics of large stiffness, long life, and small size. However, the development of its design theory has been relatively slow. At present, except for square sections In addition to the more mature design methods of strong springs, the design methods of other cross-section strong springs are basically based on the specific cross-section through the test, find the correction coefficient to obtain the empirical design formula of the specific cross-section, and now give a brief introduction to the characteristics and design problems of this type of spring .
In the same space, the load-bearing capacity of the square section wire spring is 43-48% higher than that of the round section spring. Obviously, the rectangular spring is more than 50%.
From the analysis that excessive stress is the main reason for spring failure, under the same conditions, the service life of the special-shaped section wire spring is 13-14% longer than that of the round section wire spring.
Special-shaped cross-section wire spring can produce large deformation.
Special-shaped wire springs are heavy. Spring manufacturers
The linearity is better than that of the circular section spring, that is, the stiffness tends to be more constant. Especially the spring with the long side parallel to the axis.
The scope of application is subject to certain restrictions: from the analysis, it can be seen that if the special-shaped cross-section material spring cannot fully use its advantages, it will not produce economic benefits. Under what circumstances should it be used?
(1) The design load cannot be achieved with round cross-section materials.
(2) Replace the circular cross-section compound spring.
(3) When the round material spring cannot reach the required deformation.
(4) Where the spring installation space is small.
(5) Where strict spring characteristics are required.
《一》Mold spring design principles
A. The choice of spring material allowable stress [τ] should be mainly considered to ensure the fatigue life of the spring. The dynamic life of the spring is generally divided into three categories:
Class I: The number of alternating loads is 106; Class II: The number of alternating loads is 10?-105; Class III: The number of alternating loads is less than 10?;
B. When designing non-rectangular shaped cross-section springs, it is necessary to derive and draw curves or calculation formulas in different rotation ratios, different width to thickness ratios, deformation correction coefficients (τ) and shear stress correction coefficients (β).
C. The material width-to-thickness ratio (a/b) should not be too large, and the winding of the spring should not be too small.
D. According to the given conditions and constraints, choose a design method that is simple to calculate and select reasonable parameters.
The remaining problems in “Two”
A. The low degree of standardization of mold design limits the development speed of standardized mold springs.
B. The design theory is not perfect. At present, the rectangular cross-section spiral spring is more mature, but its tolerance selection is still inconclusive. The special-shaped cross-section spiral spring is based on the rectangular cross-section, which has been corrected by experiment.
C. The degree of standardization of mold springs is low. At present, there is no official national standard or industry standard in China except for the QC7111-7113 standard formulated by our institute for the automotive industry. Mold designers have no standard to choose from is an urgent problem to be solved.
d. There are no designated factories for the production of special-shaped cross-section materials, especially oil-quenched and tempered steel wire suppliers that do not have such materials. The materials restructured by the spring manufacturers themselves are of unstable quality and high cost, which affects the promotion and application of such springs .
E. There is no special coil spring equipment for the production of such springs. The coil spring winding ratio for molds is generally less than 4, while the domestic coil spring machine is suitable for springs with a winding ratio above 4.