Fatigue crack growth modelling based on CTOD for the 7050-T6 alloy

The plastic crack tip opening displacement (CTODp) is considered to replace Delta K in the study of fatigue crack propagation. The cyclic plastic deformation of the 7050-T6 aluminium alloy was determined experimentally and modeled analytically. Then, a three-dimensional elastic-plastic numerical model which included crack growth was developed in order to predict the plastic CTOD for different loading conditions. In a parallel study, crack growth rates were determined experimentally in M(T) specimens with a thickness of 6 mm. A relation was subsequently established between da/dN and plastic CTOD for the 7050-T6 aluminium alloy, independent of stress ratio, showing that the CTOD is a viable alternative to Delta K in the analysis of fatigue crack propagation.