The dynamic fragmentation of Mott ring containing defects

This study investigates dynamic fragmentation mechanism in defective brittle materials under impulsive loading through an analysis of fragment size distribution in rock Mott rings. A hybrid finite-discrete element method with embedded cohesive fracture modeling is employed to simulate fracture propagation, with rigorous validation of mesh dependency effects via convergence analysis. A novel energy-based dynamic fragmentation model is proposed, integrating pre-existing defects into an energy equilibrium framework that balances kinetic energy conversion and fracture dissipation across both inherent flaws and newly formed cracks. Comparative analysis with the classical Grady model establishes marked improvements in resolving multi-stage fracture progression, particularly through the model's capacity to capture defect-mediated strain-rate dependencies. Results reveal three distinct fragmentation phases, elastic expansion, defect-dominated primary fragmentation, and strain-rate-dominated secondary fragmentation, in defective systems as the strain rate increases. Cumulative fragment distributions in defect-embedded rings identify three distinct failure regimes: defect-driven fragmentation, defect-strain rate coupled fragmentation, and strain-rate-dominated fragmentation. Parametric analysis reveal that (1) increased defect fracture energy destabilizes phase boundaries between primary and secondary fragmentation stages, (2) higher defect strength accentuates three-stage fragmentation under constant loading rates, while (3) defect elastic modulus shows minimal impact on staging characteristics. Fragment size agrees well with predictions from the newly proposed theoretical model, demonstrating its effectiveness in capturing defect-mediated fragmentation dynamics.