Answer
Impact loading (or dynamic loading) is significantly more dangerous for retaining rings than static loading. When a mass hits the retained part, the kinetic energy $E_k = \frac{1}{2}mv^2$ must be absorbed by the ring and the groove. This creates a transient load $P_{peak}$ that can be many times higher than the static weight. The safety factor $K$ must be increased from 3 (standard static) to 5 or 10 for impact applications. Failure under impact often looks like 'groove deformation' because the peak force exceeds the yield strength of the housing for a fraction of a second, causing the ring to dish and pop out. Engineers should use 'Heavy Duty' series rings (thicker $T$ and deeper $d$) and verify the design using the impulse-momentum theorem ($F \cdot Δt = m \cdot Δv$).
