Official Answer
Answer
Critical deflection is the point at which the wave spring ceases to exhibit linear elastic behavior and enters the plastic deformation zone. For materials like 17-7PH CH900, this is typically defined where the calculated fiber stress $S = _x000c_rac{3 _x0008_eta P D}{4 b t^2 N}$ exceeds the proportional limit. Operating a spring beyond $80\%$ of its available deflection often leads to permanent set, as the localized stresses at the wave crests exceed the yield point. Designers use a safety factor, comparing the calculated stress at maximum working height against the material's tensile strength, ensuring that $S_{max} < ext{Yield Strength} / FS$ to prevent fatigue failure in dynamic applications.
