Mechanical springs. Axial load

Elastic connections are often used to absorb and then release energy in mechanical systems. They can be found both in fairly basic applications (clothespins, pens, etc.) and in high-tech applications (vehicle shock absorbers, engine valves, satellite panel deployment mechanisms), where it is vital to fully master the spring's behavior.

Unfortunately, however, the design of elastic connections is sometimes neglected, and this can lead to problems being identified late in the prototyping phase, resulting in potentially costly and time-consuming re-design phases.

The aim of this article is to provide theoretical and practical information on the design and manufacture of elastic connections. To take things a step further, we also share design tips, the main pitfalls to avoid and practical dimensioning methods that can save precious time on project development.

In this article, we discuss the characteristics of coil springs subjected to a coaxial force. The most common geometry is the constant-pitch cylindrical helix, which can work in compression or tension. Although simple in appearance, the correct implementation of helical spring connections requires considerable expertise. First, we cover the essential notions of the behavior of a helical solid subjected to a coaxial force. Next, we deal specifically with the notions to be integrated for compression springs and then for tension springs. For each type of spring, we detail, on the one hand, the interdependencies between design parameters which, if poorly understood, lead to impossible specifications and, on the other hand, the crucial influence of the ends which form the link between the system and the working part of the spring. In the remainder of this article, we look in detail at particular geometries with varied behaviours, enabling engineers to cover a very broad spectrum of applications (variable-pitch cylindrical springs, constant-pitch conical springs, constant-angle conical springs, volute springs).