Role of particle shape in determining tensile strength and energy release in diametrical compression of natural silica grains

Extensive particle fracture has been noticed in projectile penetration tests. However current models for predicting projectile penetration depths do not consider particle fracture. Therefore, in order to understand the role of particle shape on single grain strength and the subsequent comminution process, single grain crushing tests on sand grains of different shapes and sizes were performed. High-resolution, three dimensional images of grain surface, were created using confocal microscope and fracture of the grains were captured with high-speed imaging. Acoustic emissions during single grain crushing was used to estimate the energy released during grain fracture. It was found that local stress fields influence particle strength and in natural granular material surface flaws maybe the critical flaw causing fracture. The estimated critical flaw size causing fracture were submicron in size. The mass specific fracture energy increased with increasing failure stress and decreasing particle size and is significantly greater than that computed from pure diametrical breaking. Except for large angular grains, mass specific energies for different shapes were similar. Angular sands required multiple events to break. The outcome of this work can be utilized in geomechanics to understand the comminution process and in power industry to estimate the energy required for comminution.