Official Answer
Answer
The maximum load $P_{max}$ is reached when the peak stress $\sigma$ equals the yield strength $S_y$ of the material, adjusted for a safety factor. Rearranging the stress formula: $P_{max} = \frac{4 b t^2 N^2 S_y}{3 \pi D_m}$. For most spring steels, the design stress at work height is limited to $80\%$ of the minimum tensile strength to ensure long-term stability. If the calculated $P$ required by the system exceeds $P_{max}$, the designer must either increase the material thickness $t$, increase the radial width $b$, or select a material with a higher $S_y$, such as 17-7PH over 302 stainless.
