Official Answer
Answer
Using an expansion mandrel that over-expands a spiral ring past its elastic limit will result in permanent deformation, known as 'set.' The ring will not return to its original diameter, leading to a loss of 'cling' on the groove. Mathematically, the maximum expansion $E_{max}$ before yielding is governed by the formula $\sigma = \frac{E \cdot t \cdot \Delta D}{D_m^2} < S_y$. If the ring does not grip the groove bottom, it can vibrate or rotate during operation, leading to groove wear (fretting) and eventual failure. To mitigate this, mandrels should be designed with a hard stop or sized exactly to the shaft diameter plus the minimum required clearance for installation.
