A B S T R A C TThe work demonstrates how the theory of the fatigue damage map (FDM) can be used in order to define a closed form locus where fatigue crack growth can be sought. The Intrinsic FDM Locus depending only on readily material properties represents a tool able to accurately predict crack growth of polycrystals. If the Locus is expressed in terms of a surface plot after triangulation of the data, it concludes into visualization of the potential for multiple similitude stages. The stages are defined as a function of the maximum far field stress and K. Multiple similitude stages are found to dominate the short and near threshold area (Stage I growth) and represent direct result of the effect of polycrystalline behaviour to flow resistance. The work concludes that interrogation of the points defining the Intrinsic FDM Locus and related to the three thresholds can provide potential characteristics in the quest for an ideal damage tolerance material.Keywords fatigue damage map; fatigue damage map locus; fatigue life reliability; fatigue property; fatigue threshold; grain size.
N O M E N C L A T U R Eb = Burger's vector D = average grain size E = elastic modulus G = shear modulus K Ic = fracture toughness plane strain m i /m 1 = grain orientation factor R = stress ratio R C = stage I intensification factor S = stiffness modulus α = crack length K = stress intensity factor range σ c y = cyclic yield stress σ max FL(R=−1) = maximum value of the fatigue limit, R = −1