Numerical investigation of rock sphere breakage upon oblique impact: effect of the contact friction coefficient and impact angle

Abstract

Discrete element simulations are performed to better understand the breakage of marble spheres upon oblique impact. The influence of the contact friction coefficient and impact angle on the impact-induced breakage is considered. A modelling method for oblique impact is proposed. Detailed parameter calibration and verification of the modelling method were performed. The oblique simulations show that the laboratory breakage behaviour of marble spheres upon normal and oblique impact is well matched through the proposed modelling method. Tensile and shear breakage patterns are observed in laboratory tests and simulations and are significantly influenced by the contact friction coefficient and impact angle. The shear component of the impact velocity determines the breakage at a low impact angle and high contact friction coefficient, while the normal component dominates the breakage at a high impact angle or low contact friction coefficient. The damage ratio, contact force and fragment characteristics are also analysed. Two constants, i.e., the critical shear contact force and critical normal contact force, are obtained. Finally, a comprehensive breakage criterion for brittle particles under oblique impact is proposed. The breakage patterns of brittle particles can easily be determined through the proposed breakage criterion.