Answer
Groove wall yielding occurs when the material of the shaft or bore (e.g., aluminum) cannot support the localized stress at the edge of the groove. This is identified by a 'rounding' or 'mushrooming' of the groove edge upon inspection after failure. The ring itself may appear undamaged, but the assembly fails because the groove has effectively 'widened,' allowing the ring to tilt and pop out. The remedy is to either increase the groove depth $d$, use a harder material for the housing, or specify a 'load-spreading' washer between the component and the retaining ring. Mathematically, the bearing stress $\sigma_b = \frac{P}{\pi D d}$ must be kept below the yield strength of the groove material, with a significant safety factor for cyclic loads.
