A J-integral estimation method for C(T) specimens using the Common Format Equation

A new J estimation scheme based on the Common Format Equation (CFE) is laid out for Compact Tension (C(T)) specimens. In this context, the CFE constraint factor *, originally given only for the two limits plane stress, and plane strain, is discussed. A nonlinear finite element analysis of the behaviour of blunt notched C(T) specimens with varying crack length was performed. The specimen thickness B has been varied from 3.125 up to 25 mm. Furthermore the special cases plane stress and plane strain have been considered. Considering a linear elastic - ideal plastic material, a limit load analysis has been performed numerically from which * has been obtained as a function of the ligament-to-thickness-ratio B/b. The J -integral as a function of the load line displacement v has been determined for isotropic, nonlinear hardening material, where J has been calculated using its definition as contour or surface integral, respectively. It is shown that if the obtained J (v) curves are normalized according to the Common Format Methodology, all curves fall approximately into one single curve. This allows to estimate J(v) curves for C(T) specimens using the CFE