Experimental study on cracking process and fracture properties of granite under mode I loading by acoustic emission and digital image correlation

Abstract

To explore mode‐I fracture process of hard brittle rocks, semi‐circular bending (SCB) experiments were performed with the concurrent monitoring of acoustic emission (AE) and digital image correlation (DIC). Experimental results revealed that all specimens exhibited ductile fracture characteristic and the fracture planes deviated from the ligament plane to different degrees due to interference from mineral crystals or pre‐existing weak surfaces within the intergranular boundaries. The whole cracking process can be divided into four stages: Microcrack initiation preparation, microcrack initiation and stable propagation, macrocrack formation and unstable propagation, and macrocrack coalescence. The onset of the microcrack initiation occurred at about pre‐80% load. The fracture process zone (FPZ) maintained a constant length as the crack propagated and the length of the traction free zone (TFZ) increased. The identified crack lengths based on the AE locations and energy statistical analysis consisted well with the crack lengths obtained from the DIC.