Crack evolution characteristics and mechanism in dynamic splitting failure of alumina ceramics

This study investigates the crack evolution mechanisms of alumina ceramics under dynamic splitting failure through a combined experimental and numerical approach. Dynamic splitting tests were conducted on flattened Brazilian disc (FBD) specimens using a modified split Hopkinson pressure bar (SHPB) system equipped with digital image correlation (DIC). Experimental results reveal that microcracks initiate at the flattened ends and progressively coalesce into a central macrocrack, ultimately forming a transverse fracture zone. The strain fields from DIC correlate well with strain localization during crack development. The lateral strain field exhibits semi-circular compressive strain concentrations at the flattened ends, while the longitudinal strain field shows a spindle-shaped tensile strain concentration at the specimen center. A coupled DEM-FDM numerical model was established to simulate the dynamic splitting process. The simulated stress–strain curves agreed well with experimental data, and the specimen morphologies at characteristic instants closely matched those captured by high-speed photography, thereby validating the model’s reliability. Numerical results further elucidate that the dynamic splitting process comprises four distinct stages, each characterized by specific stress responses and microcracking evolution. Microcracks first nucleate and propagate at both the flattened ends and the specimen center. The interaction of these damage zones forms a highly damaged central region that governs macrocrack propagation. Tensile microcracks dominate throughout failure, accounting for over 90% of the total crack population, whereas shear microcracks concentrate mainly in the central region and play a secondary role. Notably, the distinct distributions of lateral and longitudinal displacement fields give rise to tensile and mixed particle displacement modes, which respectively govern the generation of tensile and shear microcracks.