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

A new 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 Ω*, 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 Ω* has been obtained as a function of the ligament-to-thickness-ratio B/b. The -integral as a function of the load line displacement v has been determined for isotropic, nonlinear hardening material, where has been calculated using its definition as contour or surface integral, respectively. It is shown that if the obtained 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.