ANALYSIS OF CRACK PROPAGATION OF CRACK STRAIGHT THROUGH BRAZILIAN DISC USING PARTICLE FLOW CODE

The Brazilian tests on Cracked Straight Through Brazilian Disc (CSTBD) specimens are simulated using Particle Flow Code (PFC). Then, the effects of inclination angle and length of the pre-existing crack on the crack evolution behavior are analyzed. The results indicate that depending on the crack initiation positions, two types of main crack exist, including mode Ⅰ main crack and mode Ⅱ main crack. Mode Ⅰ main crack is initiated at the tip of the pre-existing crack. And mode Ⅱ main crack is initiated at a distance from the tip of the pre-existing crack. There also exist two types of secondary crack, including mode Ⅰ secondary crack and mode Ⅱ secondary crack. Mode Ⅰ secondary crack is initiated near the load point. And mode Ⅱ secondary crack is initiated at a distance from the load point. When the crack length keeps constant and inclination angle increases, main crack would change from mode Ⅰ to mode Ⅱ and secondary crack would change from mode Ⅰ to mixed-mode (Ⅰ+Ⅱ), and finally transform into mode Ⅰ. When the inclination angle keep constant and crack length increases, main crack keep steady and secondary crack would change from mode Ⅰ to mixed-mode (Ⅰ+Ⅱ). After the radial stress exceeds the peak stress of the specimen, a large number of micro cracks would develop and propagate, which lead to the broke of the Brazil disc. The failure process of Brazil disc is mainly resulted from the ruptures of inter-particle bonding caused by tensile stress concentration and internal strain energy release.