Describe the 'Dish Effect' and how it impacts the stress state of a multi-turn spiral retaining ring under high thrust.

Dishing occurs when a spiral retaining ring is subjected to high axial loads that cause it to tilt within the groove. This creates a moment $M$ on the ring's cross-section. The resulting stress is a combination of the initial installation stress and the applied bending stress. The dish angle $ heta$ is proportional to the applied load and inversely proportional to the ring's stiffness $E I$. As the ring dishes, the load is no longer applied uniformly, concentrating the stress on the inner edge of the ring. This can lead to permanent 'cupping' of the ring. Engineers use a safety factor, typically $2$ or $3$, to ensure that the ring stays within the elastic range to prevent this geometry-induced failure.