Discrete element analysis of diametrical compression of annular agglomerates

The tensile strength is an important material attribute of granular products, and diametrical compression is one of the most common methods to determine the tensile strength of the agglomerate. In this study, three-dimensional diametrical compression tests of annular agglomerates with various bonding strengths, i.e. interfacial energies and internal holes, are for the first time modelled by the Discrete Element Method (DEM) with the JKR theory. The fracture patterns and tensile strengths of annular specimens are analysed and compared with those of disc specimens. It is found that annular specimens show complete tension failures with progressive fractures along the loading diameter towards the central hole, while the disc specimens show wedge-shaped shear fractures near the platens. The results also show that the tensile strengths of annular specimens are linear with the surface energy, whereas increase with the size of internal hole and then decrease with the size of internal hole. A dimensionless parameter is introduced to analyse the failure mechanism of the agglomerate. This parameter quantifies the ratio between the external force exerted by the platens and the cohesive force among bonded particles. The proposed parameter emphasises the crucial influence of the internal hole size of an annular agglomerate and bonding capacity on its tensile strength.