The minimum dimensionless stress intensity factor and its upper bound for CCNBD fracture toughness specimen analyzed with straight through crack assumption

The minimum dimensionless stress intensity factor of cracked chevron notched Brazilian disc specimen is the coefficient in the crucial formula for calculating the fracture toughness using the method suggested by the International Society for Rock Mechanics. This coefficient can be conveniently obtained by the analytical method based on the straight through crack assumption proposed by Munz et al. (1980) [17], so it is very easy to determine the upper bound on the coefficient for any cracked chevron notched Brazilian disc specimen. Furthermore, the upper bound is explained by comparing the load bearing capacity of a cracked chevron notched Brazilian disc with that of the counterpart cracked straight through Brazilian disc, this comparison identifies that the upper bound concept is inherent with sound physical significance, so violation of this upper bound for the stress intensity factor is unreasonable.