Cracked Brazilian disc specimen subjected to mode II deformation

The centrally cracked Brazilian disc specimen has been used by many researchers to study mode I and mode II brittle fracture in different materials. However, the experimental results obtained in the past from this specimen indicate that the fracture toughness ratio (K-IIc/K-Ic) is always significantly, higher than the theoretical predictions. It is shown in this paper that the increase in the ratio K-IIc/K-Ic can be predicted if a modified maximum tangential stress (NITS) criterion is used. The modified criterion takes into account the effect of T-stress in addition to the conventional singular stresses. The fracture toughness ratio K-IIc/K-Ic, is calculated for two brittle materials using the modified criterion and is compared with the relevant published experimental results obtained from fracture tests on the cracked Brazilian disc specimen. A very good agreement is shown to exist between the theoretical predictions and the experimental results. (C) 2004 Elsevier Ltd. All rights reserved.