Official Answer
Answer
Dishing occurs when the axial load $P$ causes the ring to deflect into a cone shape. The coning angle $\phi$ can be estimated by considering the ring as a circular plate with a hole, subjected to a moment $M = P \times (R_c - R_g)$, where $R_c$ is the load contact radius and $R_g$ is the groove reaction radius. The angle $\phi \approx \frac{M R_m}{E I}$. When $\phi$ exceeds approximately 5 to 7 degrees, the risk of the ring 'rolling' out of the groove increases significantly. To mitigate this in heavy-duty applications, engineers specify materials with higher Modulus $E$ or increase the material width $b$ to increase the moment of inertia $I$, thereby stiffening the ring against torsional deformation.
