Effect of the crystal habit on micromechanical extensile behaviors of the crystalline rock during compression

The crystal habit controls the microstructure heterogeneity of the crystalline rock and significantly affects its mechanical behaviors. However, thus far, this effect has not been quantitatively characterized. Here we established a grain-based model to investigate effects of the crystal habit on compression-induced micromechanical extensile behaviors of the crystalline rock. Alteration of the grain morphology heterogeneity from the euhedral to anhedral was quantitatively depicted by the fractal dimension. Meanwhile, heterogeneity of grain-scale mechanical properties was also considered, which depended on the stress state. We identified two effects related to the crystal habit that affected mechanical behaviors of the crystalline rock: the tensile stress concentration effect (TSCE) and the grain boundary interlocking effect (ILE). These two effects counteracted with each other with modulating the crystal habit. The stress threshold of the crack initiation of the crystalline rock generally decreased as the crystal habit modulated from the euhedral to anhedral, while the stress thresholds of the crack damage and the peak stress first decreased and then increased. The crystal habit had important influences on the stress distributions and further affected the progressive failure characteristics of the crystalline rock. The intergranular cracking was throughout the whole process while the transgranular failure mainly emerged adjacent to the crack damage stage. With modulating the crystal habit from the euhedral to anhedral, the number of the transgranular failure zone first decreased then increased. We acquired new insights into the microcracking behaviors of the crystalline rock in which the transition to the anhedral microstructure could favor the transgranular failure.