Official Answer
Answer
Fatigue failure in wave springs usually initiates at the inner or outer diameter of the wave peak where tensile stress is maximized. Using the Goodman Criterion, the safety factor $S_f$ can be estimated by $\frac{\sigma_a}{S_e} + \frac{\sigma_m}{S_u} = \frac{1}{S_f}$, where $\sigma_a$ is the alternating stress and $\sigma_m$ is the mean stress. Common failure triggers include hydrogen embrittlement in carbon steel (SAE 1070) if not properly baked after plating, and surface pitting in corrosive environments which acts as a stress concentrator. To extend life, shot peening the surface can induce compressive residual stresses, effectively shifting the mean stress downward.
