DISCRETE ELEMENT SIMULATIONS OF THE HIGH VELOCITY EXPANSION AND FRAGMENTATION OF QUARTZ GLASS RINGS

The mechanical behavior of quartz glass rings under internal velocity impact is simulated by using discrete element method (DEM) based on the flat-jointed bond model. The microscopic mechanical parameters of the quartz glass ring were determined by comparing the standard uniaxial compressive/tensile and three-point bending numerical test results with the experimental results. Using these material parameters, the fragmentation processes of quartz glass rings under different impact velocities were numerically simulated. The numerical results showed that: the failure time of the quartz glass ring corresponded to a rebounding of the radial velocity, macroscopically this timing is coincident with the rapid drop of average stress. This radial velocity rebounding is attributed to the unloading waves incited from the brittle cracking of the tensile specimen, and can be used in the numerical analysis as the failure point. Detailed numerical tests and analysis showed that: (1) The fracture strain of quartz glass ring increases with the increase of strain rate, a phenomenon consistent with experimental observations for ductile materials; (2) The average mass of the quartz glass ring decreases with the increasing strain rate; (3) The average fragment size in the simulation was consistent with the theoretical and experimental data in other papers. An experiment device of liquid-driven expanding ring was used to conduct preliminary tests. The morphology and the number of fragments recovered from real tests are consistent with the numerical simulations.