Mode I-III Decomposition of the J-integral from DIC Displacement Data

This paper presents the implementation of the decomposition method on digital image correlation (DIC) obtained displacement fields to obtain J-integral results (J) and respective stress intensity factors (SIFs). DIC is increasingly used with the J-integral approach in experimental mechanics to obtain J estimates from complex fracture processes. In this approach, the decomposition method is applied to DIC displacement fields for the first time. Here, displacement fields are separated before stresses and strains are computed, so that subsequent computation of separate J or SIF components may follow the classical full-field J-integral approach. The sensitivity of the decomposition method to experimental errors is investigated using synthetically generated errors imposed on crack tip displacement fields (Williams' series), from which improvements to the procedure are proposed. The method is experimentally tested on PMMA Arcan specimens under mode I, II, and III, and mixed-mode I-III loading. Test results were compared to fracture toughness values obtained from ASTM tests and literature with close agreement.