Three-dimensional numerical evaluation of the progressive fracture mechanism of cracked chevron notched semi-circular bend rock specimens

• 3D progressive fracture processes of CCNSCB specimens are numerically assessed for the first time.
• The crack front of the CCNSCB specimen is not straight-through but considerably curved.
• Not only the notch tips but also the two saw-cut notch edges crack simultaneously.
• The damaged zone can be prominently confined in the ligament for a specimen with large supporting span.

The cracked chevron notched semi-circular bending (CCNSCB) method for Mode-I fracture toughness measurement has adopted the straight-through crack propagation assumption but never being fully verified. In this study, three-dimensional progressive fracture processes of CCNSCB specimens are numerically evaluated for the first time considering different supporting spans and heterogeneities. Results show that the crack front of the CCNSCB specimen is not straight-through but considerably curved, which inevitably induces errors for fracture toughness measurement; and the damaged/fractured zone can be prominently confined in the chevron notched ligament for a CCNSCB specimen with a large supporting span.