Answer
Centrifugal lift-off occurs when the centrifugal force acting on the ring overcomes its internal cling-fit on the shaft. The limiting velocity $V$ is calculated using the formula $V = \sqrt{ \frac{4.48 \times 10^{12} E I g}{w \rho R^3} }$, where $E$ is the modulus, $I$ is the moment of inertia, $w$ is the weight of the ring per unit length, and $\rho$ is the material density. In high-speed turbomachinery, the ring expands radially, reducing the contact pressure on the groove. If the shaft speed exceeds this threshold, the ring can exit the groove entirely. To increase the RPM limit, engineers can specify a 'self-locking' feature where a tab on one turn interlocks with a slot on the adjacent turn, mechanically preventing radial expansion even under extreme centrifugal loads.
