How do you diagnose a 'Shear Failure' versus a 'Groove Yielding' failure in a retaining ring assembly?

In a Shear Failure, the ring itself is cut into two pieces along its circumference. The failure surface will appear as a shiny, burnished area followed by a rough fracture, indicating that the shear stress $\tau = P / (\pi D t)$ exceeded the material's shear strength ($~0.6 \times UTS$). Groove Yielding, however, is characterized by the groove wall being pushed back or 'rolled' over. The ring may remain intact but will be 'dished' or deformed. Diagnosis is simple: if the groove is still sharp and within tolerance but the ring is sheared, the ring material was insufficient. If the groove is deformed and the ring 'popped out', the housing material was too soft or the groove was too shallow for the applied load.