J-integral evaluation from measured displacement fields using digital image correlation

In this paper, a method for evaluating the J-integral for the displacement field obtained by digital image correlation without modeling the stress strain relationship is proposed. First the displacement gradient and strain are determined from the displacements using a local least-squares method on the domain of integration. Next, the stress components are determined from the strain using the Hencky's equation and material properties. Finally, the J-integral value is determined by the numerical integration on the domain of integration. The usefulness of this evaluation method is verified by applying this method to the displacement field obtained from the elastic-plastic finite element analysis and digital image correlation. (author)