Analyze a failure where a spiral retaining ring has 'dished' but not sheared. What are the likely causes?

'Dishing' occurs when the ring deforms elastically or plastically into a conical shape. This is typically not a shear failure of the material but a structural stability failure. The most likely causes are: (1) Excessive radius or chamfer on the mating part, which applies the load too far from the groove wall; (2) The groove material is too soft, allowing the groove wall to deform and 'roll' the ring; or (3) The axial load exceeded the ring's moment capacity. Troubleshooting involves checking the 'squareness' of the retained part and verifying the groove hardness (e.g., ensuring a minimum of 30 HRC for steel housings).