On the I-II mixed mode fracture of granite using four-point bend specimen

Four-point bend experiments on black granite are conducted. The fracture behaviours of granite under pure mode I, pure mode II and I-II mixed mode are investigated, and the corresponding stress intensity factors K-I , K-II and the non-singular term T-stress are obtained through numerical-experimental method. The results are compared with the theoretical predictions of generalized maximum tangential stress criterion and other conventional criteria. It shows that generalized maximum tangential stress criterion fits the experimental results better for considering the effect of T-stress. Contrasting with other loading configurations, the values of T-stress for asymmetric four-point bend specimens are much smaller, especially for pure mode II specimens, which provide an asymmetric deformation field where the T-stress is approaching zero.