Application of Weakest Link Probabilistic Framework for Fatigue Notch Factor to Aero Engine Materials

Nickel base super alloy and titanium alloy notched components are of utmost importance because of their application in the aero industry. Titanium alloy is used for airframe components and compressor blades application because of its high strength and fracture toughness at low temperatures and high strength and creep resistance at elevated temperature. Nickel base super alloy is used in hot sections of the gas turbine engine due to its high strength and good creep, fatigue, and corrosion resistance at high temperature. The microstructure features of these alloys are reviewed and crystal plasticity finite element modeling is presented. A new probabilistic approach based on weakest-link theory which captures both the essence of microstructure and the notch root stress gradient is described and applied to nickel base superalloy and titanium alloys to determine their microstructure sensitive fatigue notch factor and notch sensitivity index at varying notch root radii. The effects of the position and the orientations of inclusion on the fatigue notch factor of nickel base super alloy is also investigated. The fatigue notch factors obtained are in direct correlation with the experimentally obtained value for the different notch root radii.