Numerical assessment of rupture mechanisms in Brazilian test of brittle materials. (15th December 2019) - Bahaaddini, Mojtaba
Highlights: The effect of contact loading conditions on failure mechanism in the Brazilian test of brittle materials was numerically studied. At low contact loading angles, cracks are initiated at the vicinity of loading rims. With an increase in the contact loading angle, tensile rupture initiates at the disc centre. It was found that the transition in the failure mode is material dependent. The ratio of uniaxial compressive strength to tensile strength was suggested for evaluation of the failure transition in the Brazilian test. Abstract: Due to the difficulties associated with performing a direct uniaxial tensile test, the tensile strength of brittle materials is commonly estimated indirectly. The Brazilian test is probably the most widely accepted indirect technique among others. Since the development of the Brazilian test, the test has received considerable attention due to its ease of sample preparation and interpretation. However, the accuracy of this method has also been criticized for a long time in the literature. This paper aims to numerically study some of these criticisms by mainly focusing on failure mechanisms, the effect of contact loading conditions and stress distributions induced in the Brazilian test. Brazilian discs having contact angles ranging from 1 to 30° (i.e. concentrated to distributed loading scenarios) were simulated in the Fast Lagrangian Analysis of Continua (FLAC) based on the finite difference model. Results of this study show that at low contact loading angles, zones of high compressive stresses are generated at the vicinity of loading rims which is followed by an initiation and propagation of the cracks from these high-stressed zones. With an increase in the contact loading angle, the magnitude of compressive stresses at the vicinity of loading rims decreases leading to the disc's tensile rupture initiation at its centre. Also, it was found that the transition in the observed failure mode from cracking under the loading rims to central tensile cracking is material dependent in a Brazilian test. Finally, the ratio of uniaxial compressive strength to tensile strength was suggested as a controlling parameter for the evaluation of failure transition in a Brazilian test. Graphical abstract: Image, graphical abstract