The same does not apply to spring washers which, being flat springs, can use flexion, torsion and shear compression. By combining different compression types as the deformation varies, the forces obtained do not need to be proportional to displacement, enabling the elasticity curve to vary to achieve the desired force.
It is possible, for example, to design spring washers for which the force increases throughout the first part of deflection, then remains constant during the remaining displacement. Likewise, spring washers can be designed to have a force that increases to a maximum value then decreases. If only the falling part of the elasticity curve is used, the result is a spring that “gets stronger as it releases”.
There are many applications for this specific feature.
