Official Answer
Answer
Dishing occurs when the ring deflects into a conical shape under high axial load due to the moment arm created between the point of load application and the groove support. This non-planar deformation results in a shift from uniform surface contact to line contact at the groove edge. The contact stress $\sigma_c$ increases significantly: $\sigma_c = \sqrt{\frac{P \cdot E}{2 \pi R (1-\nu^2)}}$. This high localized stress can exceed the compressive yield of the groove material, accelerating 'groove rolling'. Engineers minimize dishing by selecting thicker rings or by using 'back-to-back' ring configurations to increase the effective moment of inertia $I = \frac{b t^3}{12}$ against axial bending.
