Effect of the pre-crack non-uniformity on the initiation of brittle fracture in mini-CT specimen

Abstract

Non-uniform pre-crack fronts often develop during fatigue pre-cracking of mini-CT specimen, resulting in invalid measurement when following the tight requirements of the ASTM standards regarding fatigue pre-crack curvature. Invalid measurements lead to a waste of test resources which is a major issue for irradiated materials. Previous studies have demonstrated a weak effect of excessive pre-crack curvature on the experimentally measured fracture toughness in the transition regime. In this paper, experimental investigations as well as finite element simulations were performed to provide additional confirmation of this conclusion. In order to demonstrate that meaningful results can still be generated in the brittle regime from non-uniformly pre-cracked mini-CT specimens, a local approach of brittle fracture was adopted to quantify the effect of pre-crack front non-uniformity on the initiation of brittle fracture. The final goal is to contribute to consolidate relevant requirements on the pre-crack front curvature.