Energy dissipation from two-glass-bead chains under impact

The mechanisms of energy dissipation during the dynamic fracture and fragmentation of granular materials play a significant role in controlling the evolution of geological structures, enhancing the efficiency of industrial comminution and blasting, and reducing the geoenvironmental hazards. In this research, impact tests on two-glass-bead chains accompanied by micro-CT of crushed fragments are performed. The results reveal that only a small portion of the input stress wave energy is dissipated through the fragmentation of the two-bead-chain system and that the energy dissipation efficiency increases with increasing input energy. It is found that generally the glass bead at the back of the chain always experiences more damage regardless of the input stress wave energy level. The micro-CT results show that the fracture energy only accounts for a small portion (0.3%-1.4%) of the chain system absorbed energy. Such a low conversion rate is attributed to the underestimated surface area of the micro-cracks, caused by the finite resolution of the micro-CT. By pursuing a fractal dimension analysis, designed to account for the undetected micro-crack surface area, it is estimated that the energy conversion rate could be increased to 0.7%-5.1%. It appears that friction dissipation appears to always be predominant, in particular during severe fragmentation.