Official Answer
Answer
Fatigue cracking in spiral rings often initiates at the 'End-Cut' or 'Notch' where the ring is split. In high-vibration environments (e.g., aerospace turbine housings), the ring can resonate, leading to high-cycle fatigue ($>10^7$ cycles). Diagnosis involves inspection under a microscope to find the 'Origin' of the crack, which usually shows a smooth 'Mirror' zone followed by 'Beach Marks'. If the vibration frequency matches the natural frequency of the ring $f_n$, the stress amplitudes are amplified. Mitigation includes changing the mass of the ring (using a different thickness) to shift $f_n$ away from the operating frequency, or applying a dampening grease.
