Springs are used to exert forces or torques in a mechanism or primarily to store the energy of impact loads. These flexible members often operate with high values for the ultimate stresses and with varying loads. Helical springs are round or rectangular wire, and flat springs (cantilever or simply supported beams) are in widespread usage. Springs come in a number of other kinds, such as disk, ring, spiral, and torsion bar springs. Numerous standard spring configurations are available as stock catalog items from spring manufacturers. Figure 14.1 shows various compression, tension, and torsion springs. The designer must understand and appropriately apply spring theory to specify or design a component.

Pneumatic springs of diverse types take advantage of the elastic compressibility of gases, as compressed air in automotive air shock absorbers. For applications involving very large forces with small displacements, hydraulic springs have proven very effective. Our concern in this text is only with springs of common geometric form made of solid metal or rubber. For more information on others, see [1-5]. As discussed in Section 1.4, mechanical components are usually designed on the basis of strength. Generally, displacement is of minor significance. Often deflection is checked whether it is reasonable. However, in the design of springs, displacement is as important as strength. Anotable deflection is essential to most spring applications.