Evolution on deformation behaviour of brazilian test under different contact area using particle image velocimetry and finite element modelling

Abstract

This paper presents a study on the deformational behaviour of homogeneous material using Particle Image Velocimetry (PIV) and the Finite Element Method (FEM). For the initial stage, as to eliminate the inhomogeneity characteristic of rock material, homogenous acrylic material, were tested for its tensile strength using Brazilian test, under different contact area. Later, the test was carried out using a sandstone sample. It was found, with increases in the contact area, the tensile strength decreases. Based on the displacement vector of the PIV and stress concentration in the FEM, it is proven that the failure initiates from the center of the sample, which describes the bi-axial state of stress experienced in the sample. The FEM has successfully simulated that with increasing contact area, the vertical stress act in compression increases. It concentrated at the center of the sample, and move outward from the sample horizontally in lower tensile stress, which caused the diametrical fracture. In conclusion, FEM and PIV are effective tools for a better understanding of the failure behaviour samples under tensile load, particularly with varying contact area between sample and loading platen.