Rebuttal: Shallow wide groove scratch tests do not give fracture toughness

Lin and Zhou (2013) recently showed that by using the depth of cut as a size measure, cutting forces from scratch tests on a quasibrittle material, such as rocks, followed Bažant’s simple size effect law (SEL). It was clear that LEFM applied only at deep cutting which might not be attainable. Akono et al. (2014) disagreed and contended that wide shallow groove cuts gave KIC based on an SEL that was scaled by width. We show herein that their conclusions were not supported by data and that the presence of sidewall friction on groove cuts further complicates efforts to obtain KIC.