J-Integral Evaluation for Finite Strain Elastic-plastic Solid from Displacements Measured Using Digital Image Correlation

Abstract

This paper proposes a method for evaluating J-integral from measured displacements based on the finite strain theory. Logarithmic strain components in the material coordinate system are evaluated from displacements measured using digital image correlation. A finite element model is utilized to obtain the logarithmic strains as well as the displacement gradients from measured displacement distributions. Then, the stresses are computed from the logarithmic strains using the incremental strain theory. Finally, the J-integral values are obtained numerically using the domain integration. The effectiveness of the proposed method is demonstrated by applying it to the displacement fields measured by digital image correlation. The J integral values obtained using the proposed method are compared with those obtained based on the small strain theory and with those obtained from the HRR displacement fields. Results show that the J-integral evaluation based on the small strain theory and that from the HRR displacement fields underestimate the J-integral values.