Official Answer
Answer
The ring must be expanded (external) or contracted (internal) to clear the shaft or bore. The maximum stress during installation $\sigma_{inst}$ is $\sigma_{inst} = \frac{E \cdot t \cdot (D_s - D_{clear})}{D_m^2}$. If $\sigma_{inst}$ exceeds the yield strength $S_y$, the ring will experience permanent set and will not 'cling' to the groove bottom. The industry standard is to ensure $\sigma_{inst} < 0.8 S_y$. If a ring is over-expanded, its free diameter $D_s$ increases, and it may fail to provide the required centrifugal capacity or axial stability. If the application requires a large expansion, a material with a higher elastic limit or a different ring cross-section must be selected.
