As an advanced ceramic, boron carbide has both a low density and excellent mechanical strength. Under impact loading, the fragmented ceramic can transform to a granular medium, and the flow behavior of this granular phase under high rates and large pressures remains unknown. In order to mechanically characterize the multi-axial flow behavior of granular boron carbide, pressure shear plate impact (PSPI) experiments were designed and performed on a series of commercial boron carbide powders with average particle size ranging from 0.7 to 50 microns. The boron carbide powders are deformed at a shearing rate as high as 2×104 s-1 with a superimposed hydrostatic pressure up to 3 GPa. The measured granular shear strength is between ~200 and 400MPa with a strong pressure dependence. Other important mechanical properties such as granular wave speed and Drucker – Prager coefficient can be extracted from the experiments. With the help of X-ray tomography and phase contrast imaging, accurate microstructural reconstructions with enriched material information were obtained for our powders. From the CT data, the larger particles contain smaller voids which can act as the crack nucleation sites during deformation. Some particles have non-convex shapes, which introduce the particle bending mechanism locally. A meso-scale finite element simulation on the reconstructed CT images will be compared with the experimental results in order to help us understand the granular flow.
2021-04-07 08:00:00
