Official Answer
Answer
For external rings, centrifugal force causes the ring to expand radially, which can eventually lead to the ring lifting out of the groove. The maximum RPM ($V$) is calculated using the formula $V = \frac{715}{D_o} \sqrt{\frac{E imes I imes ext{cl}}{_x000d_ho imes A imes R_m^4}}$, where $D_o$ is the shaft diameter, $E$ is the modulus, $I$ is the moment of inertia, 'cl' is the centrifugal clearance (groove depth - ring radial wall), $\rho$ is the density, $A$ is the cross-sectional area, and $R_m$ is the mean radius. Engineers must ensure the operating RPM is at least 20% below this theoretical limit. If higher speeds are required, a 'self-locking' feature (a tab and slot) is integrated to mechanically prevent expansion.
