Explain the mechanism of 'ring walking' and how to mitigate it in oscillating applications.

'Ring walking' is a phenomenon where the ring rotates within its groove due to vibration or oscillating thrust loads. In severe cases, this can lead to abrasive wear of the groove walls. Mitigation strategies include increasing the 'clinging' force by reducing the ring's free diameter or using a 'heavy duty' series ring with a larger radial wall $w$. Alternatively, a 'self-locking' spiral ring can be used, which features a tab on the inner turn that locks into a notch on the outer turn, preventing both radial expansion and circumferential rotation. This is standard in high-vibration aerospace and automotive driveline components.