Abstract：Some testing samples containing a pre-existing ellipse flaw (b/a=0.5) made from non-transparent mortar and transparent resin material are built. Under uniaxial compression, a series of observation experiments on the 3-D fracture process of the flaw are carried out. The experimental results show that the primary crack shapes are basically similar in the two different materials, are a pairs of antisymmetric wrapping wing cracks. But, their initial fractured places are different. Some new cracks initiated almost simultaneously near the long-axis tips of the ellipse flaw, yet not on its long-axis tips in transparent resin. but, cracks started to extend near short-axis tips, yet not on its tips in mortar samples. And, the finally fractured patterns from the samples from the two materials are greatly different under the same loading. The samples are cleaved by macroscopically tensile fracture planes in resin samples, cut by compression-shearing fracture faces in mortar ones. It may be resulted from material behavior and initial fractured place. The results from 3-D fracture analysis agree with the observed phenomena in experiments. The result from the 2-D simplified mode only is the characteristic solution in the normal plane cross ellipse long-axis, and the fractured effect from Mode III is omitted. It need further investigate the 3-D fracture mechanism of pre-existing flaws with mode III fracture.
2011, Vol. 32 
