Numerical study of the Brazilian tensile test: 2D and 3D simulations

The Brazilian splitting test is widely used to determine the tensile strength of rocks and rock-like materials due to its easy sample preparation and an easier compressive test setup as an indirect testing method compared with performing a direct uniaxial tensile test. However, the accuracy of this method has also been criticized for a long time in the literature since its introduction. This paper carried out two-dimensional (2D)/three-dimensional (3D) numerical simulations of the Brazilian tensile test using a continuum elastoplastic analysis to reveal the variation of fracture modes of the Brazilian disk and its fracture evolution process. The effect of compression-tension ratios and contact loading angles on the fracture modes of the disk specimens was studied through 2D simulations. Through 3D simulations, the initiation and expansion processes of the 3D fracture under different loading angles were explored. The simulated results of failure modes, stress distributions, and calculated tensile strengths were analyzed. The 2D numerical results show that the larger the contact loading angle and the compression–tension ratio, the more likely the Brazilian disk specimens crack first at the disk center. The fracture initiation under the loading rims is caused by shear failure, but further propagation of the split fracture is driven by tension failure. The 3D numerical simulation results show that the crack initiation point is always located on the end face of the disk and gradually moves to the center from the loading ends as the loading angle increases. When the central tensile cracking appears, the 3D fracture expanded toward the inside of the specimen with an arc boundary. Regardless of whether the disk specimen starts to fracture initially at the disk center or the loading points, the Brazilian tensile test may underestimate the tensile strength of rocks due to the 3D effect.