Tensile behaviors of granite: Grain scale cracking and fracture process zone

This work presents results on grain scale cracking behaviors, inhomogeneous deformation and fracture process zone of Australian Harcourt granite under tensile conditions. Brazilian test was performed with cracking initiation and propagation being monitored by a high speed camera (2×105 frames/s). Digital image correlation (DIC) was utilized to obtain full-field kinetics and, the development of fracture process zone was characterized using an extended DIC algorithm. The obtained real-time information was further cooperated with the distribution of mineral grains obtained by the synchrotron micro CT and the digital photograph of crack surfaces. The initiative location and the interaction between the micro-cracking process and mineral grains were identified and analyzed. It is found that the first crack initiates on a quartz grain near a biotite particle with some deviation away from the disc geometrical center. Besides, biotite grains trend to deviate or arrest micro cracks resulting from the cleavage structure and higher ductility. The fracture process zone presents as a narrow band whereas it occurs and develops prior to visible cracks.