Experimental analysis of the plastic CTOD to characterize the variable amplitude fatigue crack growth in Grade 2 titanium samples

In this paper, the plastic component of the crack-tip opening displacement (CTODp) is experimentally evaluated to characterize the fatigue crack growth behavior in a Grade 2 titanium sample under single overload with constant amplitude loading conditions. The CTOD measurements were performed with the 2D-Digital Image Correlation (DIC) technique. The experimental results show a linear correlation between CTODp and fatigue crack growth rates, suggesting the independence of this relationship to load-interaction effects. Therefore, this study demonstrates that the CTODp can be a suitable crack-driving parameter to study crack propagation behavior under variable amplitude loading. Furthermore, it suggests that the fatigue crack growth process is primarily caused by cyclic plastic deformation.