Improved Brazilian test specimen: From flattened Brazilian disc to grooved Brazilian disc

摘要

We ideate a new specimen configuration to improve the Brazilian test, i.e. grooved Brazilian disc (GBD). With a pair of narrow and shallow groove cut at opposite ends of the loading diameter, GBD relieves the shortcoming of non-central crack initiation possibly inherent to the counterpart complete Brazilian disc (BD) subjected to diametrically compression during testing. Having the same merit pertaining to our previously-proposed flattened Brazilian disc (FBD), GBD can be used in the Brazilian test more effectively than BD. GBD can represent the original BD, FBD, and the cracked Brazilian disc as its special cases. More advantages may be obtained if the geometric parameters of GBD are suitably chosen by referring to the analytical formulas, derived by superposition of two models we proposed. The approximate formulas can be used to predict qualitatively evolution trend of the stress both at and near the front of the apex of the groove, and also the influencing geometric parameters of GBD. Quantitative numerical calculations and experimental results are also provided. In conclusion, a minor change in boundary condition of a Brazilian disc specimen under diametral compression, such as FBD and GBD, can influence the fracture process of the tested specimen, enhancing their effectiveness in the Brazilian test.