The resistance to impact damage and subsequent fatigue response of two titanium alloys

Two high performance titanium alloys, Ti–6Al–4V in a mill annealed form and Ti–25V–15Cr–2Al, have been assessed for their resistance to foreign object damage (FOD) and subsequent response to fatigue loading. Laboratory specimens, designed to simulate the cross sectional geometry of gas turbine aerofoils, were subjected to particle impacts of varying energy at edge locations in an attempt to represent severe particle ingestion during typical service. The form of impact damage is fully characterised in each alloy and related to the energy and specific location of impact. Compared to pristine specimens, the fatigue strength of damaged specimens is significantly reduced in both materials. Analytical techniques to account for the influence of FOD on fatigue strength are explored.