Size effect and other effects on mode I fracture toughness using two testing methods

Mode I fracture toughness (KIC) is an intrinsic material property that quantifies its resistance to tensile propagation. The International Society for Rock Mechanics has endorsed four methods determine the KIC of rock, namely, short rod, chevron bend, cracked notched Brazilian disc, and semi-circular bend (SCB) methods. In this study, we compare results SCB technique with those recently proposed pseudo-compact tension (pCT) test, which proven be convenient assessment in both fragile ductile rocks. We select as a benchmark method due popularity, simplicity, straightforward testing configuration. discuss 146 tests performed different lithologies (Arcera, Pinacas Corvio sandstones, Blanco Mera granite), sample sizes (100, 50 38 mm diameter), range notch lengths. also assess test repeatability intercomparability obtained using two techniques. Compared pCT allows improved control specimen behaviour after peak load, provides greater wealth mechanics information. specimens yield higher than samples. Although observe tends decrease increase length ratio, effect appears non-significant based on statistical assessments. Accordingly, corresponding mean values are comparable medium- large specimens. influence size more pronounced tests, while show less dependence harder lithologies. Therefore, set up minimum requirements testing, addition geometrical constraints, some key lithology-dependent properties (strength, mineralogy, grain size, etc.) should considered. Further methodological considerations related execution discussed.