An entropy-efficiency-energy framework for mechanism transitions in dynamic particle fragmentation

Dynamic particle fragmentation under impact arises from nonlinear interactions among particle morphology, moisture, and energy dissipation. Although high strain-rate experiments and numerical simulations have improved understanding of bulk responses, they still provide limited insight into the coupled evolution of microstructural reorganization and energy transfer. To address this limitation, this study proposes a dimensionless entropy-efficiency-energy framework that links energy dissipation with structural evolution and disorder generation. Split Hopkinson Pressure Bar (SHPB) experiments on particle assemblies with different shapes and saturation levels are combined with morphological descriptors and Markov transition modelling. The analysis identifies three distinct fragmentation behaviours associated with different compression stages under the impact loading: reversible-dissipative, irreversible-fragmentation, and transitional restructuring. Angular particles exhibit progressive entropy growth and permanent breakage, rounded particles dissipate energy primarily through reversible processes, and mixed-shape systems show stage-dependent restructuring, primarily shaped by morphology and modulated by moisture. Trajectory bend angles and directional breakage rates emerge as sensitive indicators of fragmentation transitions. This framework resolves the gap by linking energy dissipation with structural reorganization under shape-moisture coupling, enabling both physical interpretation and predictive classification of dynamic fragmentation.