Effects of Ballistic Impact Damage on Fatigue Crack Initiation in Ti- 6Al-4V Simulated Engine Blades

摘要

Damage induced by the ingestion of debris into jet engines has caused great concern for maintenance personnel. The impact of the debris on the leading edges of blades creates nicks and dents, which are referred to as foreign object damage (FOD). FOD can significantly reduce the fatigue resistance of the component. Due to this concern, supplementary FOD inspections and guidelines were implemented into maintenance to prevent possible catastrophic failures. The guidelines provide instructions of serviceability and repair limits for damaged engine blades based on the depth of the defects. This study characterizes damage caused by ballistically impacting spherical glass beads on leads edges of simulated engine blades and correlates it to their high cycle fatigue strength. Both leading edges of diamond cross-section tension axial fatigue samples were impacted with 1 mm (0.040 inch) diameter glass beads at 305 m/s (1000 f/s) at an angle of incidence of either degree or 30 degrees. The samples contained either a sharp leading-edge (LE) radius of 0.381 mm (0.015 inch) or a blunt LE radius of 0.127 mm (0.005 inch).