Official Answer
Answer
When a spiral ring fails below its rated thrust capacity, the root cause is often 'groove deformation' or 'ring dishing.' If the groove material (e.g., aluminum) is soft, the groove wall yields under the axial load, creating a ramp (chamfer). The ring then 'dishes' (cones) and follows this ramp, expanding radially until it clears the groove. This is a common failure mode in lightweight aerospace gearboxes. Analysis involves measuring the groove wall angle after failure. If the angle exceeds $10^{\circ}$, the groove is the culprit. The fix is to either harden the groove (e.g., anodizing or heat-treating) or use a thicker ring to distribute the bearing load over a larger groove area.
