Computational Verification of the Optimum Boundary Condition of the Brazilian Tensile Test

Abstract

The present research analyses the configuration of jaws to avoid the premature failure of the disc in the Brazilian test. The objective is to depict the loading device configuration that most likely produces results comparable to the Hondros' analytical stress solution. To this end, several numerical analyses have been carried out for different contact angles with the Finite Element Method. It was deduced that the final contact angle plays an important part in the success of the Brazilian test and that the Griffith criterion can be fulfilled if the equivalent stress is calculated. Additionally, the orientation of the forces in the contact between the loading device and the disc has been studied for different friction conditions. According to the numerical results, it was found that a loading arc configuration of 20º shows the best agreement with the probable values given by the analytical stress model when the uncertainty of its magnitudes is taken into account. The study also demonstrates that the friction in the contact between the optimal loading configuration and the disc does not seem to significantly affect the theoretical predictions in the centre of the disc.

A Novel Analytical Solution for the Brazilian Test with Loading Arcs

“…Failure begins when the equivalent Griffith stress σ G is greater than or equal to the tensile strength σ t of the brittle material. e work performed by Satoh [36], and verified later by others authors [20,37], concludes that the predominant failure condition in this alternative test according to the Griffith criterion is 3σ θ + σ r < 0. erefore, the tensile strength is given by the equivalent Griffith's stress [8]:…”

“…e fact that the stress field at the centre of the disk is quite insensitive to the loading pressure distribution does not guarantee the validity of the results obtained from a statistical point of view. A recent research work indicated that the distribution of the contact load is not uniform and that the statistical validity of the prediction, based on the Hondros assumption [17], depends on the loading arc length [20]. e models developed in the engineering field usually intend to reproduce the case under study with the required accuracy.…”

Experimental verification of the boundary conditions in the success of the Brazilian test with loading arcs. An uncertainty approach using concrete disks

“…7 The range of contact angles recommended by the ISRM 11 does not seem to meet the Griffith's criterion, as it has been demonstrated that the failure, for these angles, can be located near the loading zone. 7,[14][15][16] This would invalidate the test for the determination of the tensile strength.…”

Experimental study correlating damage and permeability in concrete using confined, flattened Brazilian disks

“…The classic Brazilian disk test determines the tensile strength of brittle materials by diametrically loading a thin circular disk to failure. The test has become a standard method of determining the tensile strength of brittle rock by the International Society of Rock Mechanics (ISRM) and the American Society for Testing and Materials (ASTM) (Guti errez-Moizant et al, 2018). Hondros (1959) derived the full stress field for a diametrically loaded Brazilian disk under plane stress conditions.…”