Shock induced damage and failure mechanisms of magnesium aluminate spinel based on an atomistically calibrated bond-based peridynamic model

Abstract

Understanding the dynamic mechanical properties and failure behavior of polycrystalline magnesium aluminate spinel MgAl₂O₄ is an important task for the development and design of transparent ceramic armor. However, the lack of the consideration of the microstructural characteristics in existing investigations leads to difficulties in accurately explaining the relationship between microcrack propagation and macroscopic damage evolution. To further explore the influence of the microstructure on the dynamic mechanical behavior of MgAl₂O₄ spinel, in this study, we propose a modified peridynamic (PD) model which take into account the fracture properties of grain boundaries and a compressive failure criterion with a residual post-failure bond strength. Fracture parameters of grain boundaries in PD model are extracted from molecular dynamics (MD) modeling. Meanwhile, planar impact experiments are performed to calibrate the PD simulations. In addition to the observed pullback signal indicating spall, the reload signal representing failure wave is also captured in experiments. The numerical predictions agree well with present experimental results, and provide new insight into the damage characteristics and failure mechanisms in both spall and failure wave events. With the increase of grain size, the ultimate spall strength decreases, while the failure wave velocity increases. Moreover, the velocity transition interval between the spall fracture and the failure wave is obtained, and the appearance of the third recompression phenomenon is interpreted.