Answer
The maximum operating stress $\sigma$ occurs at the peak of the waves and is given by $\sigma = \frac{1.5 \pi P D_m C_f}{Z^2 b t^2}$, where $C_f$ is a stress concentration factor related to the wave geometry. For 17-7PH stainless steel in the CH900 condition, the tensile strength $UTS$ is approximately $200-230$ ksi. To ensure an infinite fatigue life (over $10^6$ cycles), the operating stress at the maximum deflection must be kept below the fatigue endurance limit, typically $45-50\%$ of the $UTS$ for non-corrosive environments. If the application involves high-frequency cycling, a Goodman or Gerber criterion analysis should be performed, plotting the mean stress $\sigma_m = (\sigma_{max} + \sigma_{min})/2$ against the alternating stress $\sigma_a = (\sigma_{max} - \sigma_{min})/2$.
