Abstract: Effects of three types of loading, i.e. concentrated loading, plate loading and flattened loading, on the macroscopically mechanical behaviors, tensile strength and cracking processes of Brazilian disks are numerically investigated. The effect of tensile strengths of materials is presented for three kinds of loading types. In addition, the modified coefficients of tensile strength at different loading angles are presented for the flattened Brazilian discs. A continuum-discontinuum method which combines the Lagrangian element method, the deformational discrete element method and the fictitious crack model is adopted. The method can be used to simulate the deformation in the elastic stage and actual cracking of materials. It is found that the flattened loading easily leads to a crack at the center of Brazilian disc, while the concentrated loading or plate loading most likely results in shear failure. When the disk failures at the center, the numerical solution of the concentrated loading is closest to the calculated tensile strength, followed by the plate loading mode, and finally the flattened loading. The materials with low tensile strength normally leads to cracking at the center of the disk for any loading type; otherwise, there is shear failure at two loading ends of the disc. After the disk centrally cracks, a great number of microcracks coalesce to form a band that continuously propagates along the loading direction, and meanwhile the failure is accompanied by stress wave generation and propagation.

Key words: Brazilian disc, cracking, tensile strength, plate, flattened Brazilian disc, concentrated force, continuum-discontinuum method, numerical simulation