Failure criterion for brittle materials with U‐notches: Unification of characteristic length‐based and grain size‐based criteria.

Here, the limitations of characteristic length‐based (Lchb) and grain size‐based (Gb) criteria with two or three parameters were pointed out employing the apparent toughness tests of 12 different ceramics at a large span range of U‐notch root radius (ρ) values. After comprehensively considering the potential influencing factors of stress intensity factor (Kc), ρ divided by critical notch tip radius (ρc) was proposed as the independent variable, and the data of 21 materials (covering ceramics, plastics, resins, rocks, and metals) was summarized and discussed to establish a simple and more applicable Kc prediction model. Results indicated that Kc/KIc was a power function of ρ/ρc with a power exponent n of 0.5 for ideal materials and less than 0.5 for actual materials. It was also found that ρc can be calculated simply by KIc2/(πσ02), where σ0 represented the inherent strength. This semiempirical criterion succeeded in unifying the Lchb and Gb criteria without introducing more parameters to increase the prediction accuracy of the Kc at the U‐notch root for brittle materials like ceramics. [ABSTRACT FROM AUTHOR]