STUDY ON THE DYNAMIC INDENTATION LOADING RESPONSE OF AlON TRANSPARENT CERAMICS

Transparent ceramics exhibit outstanding light transmission and impact resistance, the loading response characteristics under impact loads are crucial for understanding the material's failure mechanisms. To elucidate the failure response of transparent ceramics under complex stress conditions, dynamic indentation loading experiments on AlON transparent ceramic materials were conducted using a split Hopkinson pressure bar (SHPB) system. By capturing strain signals of incident, transmitted, and reflected waves on the surface of the bars, the P-h response curves of the material under dynamic loading with a spherical indenter were obtained. The damage characteristics of transparent ceramics under static and dynamic loads were comparatively analyzed using an optical microscope. The indenter loading process was equivalent to the deformation process of a spherical cavity expanding outward under internal pressure p_i, with corrections made to the effective indenter shape during unloading. An improved embedded center of dilatation (ECD) model under spherical indenter loading was established to calculate the loading response process and the stress field distribution inside the ceramic during dynamic indentation. The results indicate that the dynamic indentation tests based on SHPB system can characterize the dynamic deformation response of ceramics. AlON transparent ceramics exhibit significant plastic deformation response during dynamic indentation. Compared to static loading, the surface damage of the material is aggravated and shows a certain degree of spalling. The Brinell hardness (HB) of the material shows significant strain rate sensitivity and indentation size effect (ISE), that is, the hardness gradually decreases with the increase of loading force. The indenter radius R, the strain hardening index n of the material, and the dimensionless parameter ε_b have significant effects on the indentation loading process. During the unloading process of the indenter, the presence of the plastic stress field leads to the initiation of radial cracks in the dynamic indentation process.