Answer
The maximum fiber stress $\sigma$ at a given work height occurs at the crests of the waves and is calculated using $\sigma = \frac{3 \pi P D_m}{4 b t^2 N_w^2}$, where $P$ is the load at that height. The stress distribution is non-uniform because the wave spring functions as a series of redundant curved beams; the bending moment is highest at the contact points (crests) and decreases toward the nodes. For materials like Inconel X-750, engineers must ensure that this calculated stress does not exceed the minimum yield strength of the material at the operating temperature. If the stress exceeds approximately 80 percent of the yield strength, the spring may undergo permanent set (plastic deformation), which is often modeled using a corrected stress factor for multi-turn springs to account for the actual geometry and friction between turns.
