Fracture Mechanical Properties of Rocklike Materials Under Half Symmetric Loading

The authors studied the fracture mechanical properties under half-symmetric loading in this paper. The stress distribution around the crack tip and the stress intensity factor of three kinds of notched specimens under half symmetric loading were compared. The maximum tensile stressσ_maxof double notch specimens was much greater than that of single notch specimens and the maximum shear stressτ_maxwas almost equal, which means that the single notch specimens were more prone to Mode II fractures. The intensity factorsK_IIof central notch specimens were very small compared with other specimens and they induced Mode I fractures. For both double notch and single notch specimens,K_IIwas kept at a constant level and did not change with the change ofa/h, andK_IIwas much larger thanK_I.K_IIhas the potential to reach its fracture toughnessK_IICbeforeK_Iand Mode II fractures occurred. Rock-like materials were introduced to produce single notch specimens. Test results show that the crack had been initiated at the crack tip and propagated along the original notch face, and a Mode II fracture occurred. There was no relationship between the peak load and the original notch length. The average value ofK_IICwas about 0.602 MPa×m^1/2, andK_IICwas about 3.8 timesK_IC. The half symmetric loading test of single notch specimens was one of the most effective methods to obtain a true Mode II fracture and determine Mode fracture toughness.