Local strain energy density to predict size-dependent brittle fracture of cracked specimens under mixed mode loading

In this paper the SED-approach is applied to a set of experimental data reported in the literature. Data are referred to mixed mode fracture resistance of Guiting Limestone, a sedimentary soft rock. Two types of specimens have been investigated: cracked Brazilian disk (BD) specimens under diametral compression and edge cracked semicircular bend (SCB) specimens under three-point bend loading. To evaluate size dependent behavior, specimens characterized by four different radii were tested under different mode mixities. To assess the static strength of cracked components the strain energy density (SED) criterion has been used. It is shown that this criterion can predict the size-dependent fracture behavior of Guiting Limestone. Critical experimental loads have been compared with the theoretical ones, estimated keeping constant the critical value of strain energy density (SED). The dimension of the control volume was found to be a function of specimen size and geometry.