MIXED MODE DYNAMIC STRESS INTENSITY FACTORS OF CRACKED STRAIGHT THROUGH FLATTENED BRAZILIAN DISC SPECIMENS

In order to establish a standard for the test of mixed modedynamic fracture of rock with the cracked straight through flattenedBrazilian disc (CSTFBD) specimen, we use finite element method first tocheck the related results in literature on the cracked straight throughBrazilian disc specimen (CSTBD). The I-II mixed mode dynamic stressintensity factors (SIFs) of the two kinds of discs with differentdimensionless crack lengths (i.e. the half length of the crack normalized bythe radius of the specimen) are obtained to show that the differences of the dynamic SIF's time history between these two kindsof specimens are within 10\%, and the numerical method used in this paperis valid. Then for CSTFBD specimens, the I-II mixed ratio, the angle ofcrack initiation, and the loading angle for pure mode II fracture testare obtained. The results are useful for mixed mode dynamicfracture test of CSTFBD, including specimens preparation, the location anddirectional alignment of the strain gages, as well as the estimation for the crack initiation time andthe crack initiation direction.