Probabilistic relation between stress intensity and fracture toughness in ceramics

Abstract For fracture toughness (KIC) testing, the critical stress intensity factor (KC) equals KIC only when specimens satisfy linear elastic fracture mechanics (LEFM). Thus, direct experiments may not yield the KIC of a ceramic if the relation between KC and KIC is not well understood because valid tests are difficult for polycrystallines. This study proposes a fracture model characterizing the KC/KIC ratio as a function of the relative crack size a/G (a: initial crack size, G: average grain size). In addition, normal distribution is incorporated to describe the inevitable scatters in KC-measurements. The results show that the upper and lower bounds with 96% reliability cover nearly all experimental data, and they contribute to a better understanding of fracture unsatisfied with LEFM.