Fatigue Cracked Helicopter Gears that Initiated from Exogenous Inclusions and Subsequent Fatigue Testing to Evaluate Micro-Cleanliness of the VIMVAR SteelThursday (28.05.2020) 10:20 - 10:40
Examples of several fatigue cracked helicopter gearbox gears made from VIMVAR steel that initiated at exogenous inclusions will be presented. One inclusion cluster that measured 0.46 mm by 0.13 mm was traced back to the VIM crucible refractory brick. Shot peened axial fatigue test specimens were used to evaluate inclusion type, size, and prevalence for various steel mills for this particular steel alloy. As expected, scatter in the data was observed due to the limited number of specimens and the inclusion size/type, but some trends did emerge.