Official Answer
Answer
Fatigue failure typically occurs at the wave crests (inner or outer diameter) where the bending stress is maximal. To analyze this, we use the Goodman equation: $_x000c_rac{S_a}{S_e} + _x000c_rac{S_m}{S_u} = _x000c_rac{1}{FS}$, where $S_a$ is the alternating stress $(S_{max}-S_{min})/2$, $S_m$ is the mean stress $(S_{max}+S_{min})/2$, $S_e$ is the endurance limit, and $S_u$ is the ultimate tensile strength. If a wave spring fails prematurely, SEM (Scanning Electron Microscopy) is used to look for 'beach marks' and striations. Most failures result from $S_a$ being too high, often caused by an underestimated stroke or a lack of preload, allowing the spring to 'snap' or vibrate excessively.
