Official Answer
Answer
Dishing (or coning) occurs when the thrust load $P$ exceeds the moment resistance of the ring's cross-section. As the ring deforms into a cone shape, it expands radially and eventually slips out of the groove. This is usually caused by either a groove that is too shallow or a groove material with low yield strength. If the groove wall deforms, it provides a 'ramp' for the ring to climb. The solution is to use a harder groove material, increase the groove depth $d$, or use a heavier cross-section ring. Multi-turn rings are also more resistant to dishing than single-turn rings because the individual turns provide mutual support against the bending moment.
