An analysis of fracture under biaxial loading using the non-singular T-stress

Finite element analysis using a two-dimensional modified-boundary-layer approach was used to model the effects of biaxial loading on crack tip stress fields. Loadings were applied corresponding to an elastic K-I field, non-singular T-stress and a biaxial stress. For through-thickness cracks the T-stress inherent in the specimen geometry is augmented by the external biaxial stress. For surface-notched specimens the biaxial stress acts out of the crack plane. This effect was modelled with generalized plane strain elements. Results were analysed using the Anderson-Dodds approach for cleavage and the Beremin model in the ductile regime. Biaxial loading is predicted to have a large effect on the toughness of a through-thickness crack but little effect on a surface crack. Experimental results from a previous series of large-scale biaxial fracture tests are generally consistent with these predictions.