Effects of the ratio of flaw size to specimen size on cracking behavior

To investigate the size effects on the cracking behavior of flaw-containing specimens under compressive loading, rectangular parallelepiped specimens containing a single centrally located flaw are numerically loaded using the bonded-particle model (BPM). Effects of the ratio of flaw size (length) to specimen size on cracking behavior are carefully studied. The numerical results show that increasing the ratio of flaw size to specimen size within a reasonable range (≤0.33) has no obvious effects on the first crack initiation stress, but decreases the uniaxial compressive strength. In specimens of a high flaw size to specimen size ratio, the newly generated cracks have longer extension length, which allows for easier crack identification as compared with that of the low ratio specimens. These phenomena are also observed in the physical test. Based on the present study, recommendations are given on choosing appropriate specimen widths in the BPM simulation. The failures of flaw-containing specimens as well as the outward bending effect of narrow specimens are also discussed.