Loading rate strengthening mechanism of alumina and zirconia ceramics

The dynamic mechanical properties of ceramic materials are often significantly different from their quasi-static properties. Back-side tensile failure caused by bending stress is the most common failure mode of ceramic target plate structures under quasi-static or dynamic impact loading. However, current research on the dynamic bending behavior of ceramics remains limited. In particular, the strengthening mechanism related to loading rate under dynamic bending conditions is not well understood. To address this issue, this study designed mini three-point bending specimens and matching fixtures based on the split Hopkinson pressure bar (SHPB) system. Zirconia (ZrO₂) and alumina (Al₂O₃), two typical ceramic materials, were selected for testing. Experimental results show that the dynamic bending strength of both ceramics increases with loading rate. To further understand the mechanism of this strengthening phenomenon, finite element analysis (FEA) was used to simulate the structural response under dynamic bending. The results indicate that the bending strength of ZrO₂ and Al₂O₃ depends on both structural and material responses. These effects were quantified by comparing the experimental results with the FEA predictions. Additionally, a microstructural transition was observed in the ceramics under varying loading conditions. This transition provides insight into the underlying mechanisms of the material's response. In summary, the structural effect results from the inertia constraints, while the material response arises from failure mechanism transition. This study offers new methods and perspectives for understanding the dynamic strength enhancement of brittle materials.