SHEAR LOCALIZATION IN HIGH-STRAIN-RATE DEFORMATION OF GRANULAR ALUMINA

摘要

Dynamic deformation of densified granular alumina of two different particle sizes was investigated by the radial symmetric collapse of a thick-walled cylinder. The densified granular alumina was used to model the flow in ballistic impact and penetration of fragmented ceramic armor. Shear localization was a well developed deformation mode at an overall radial strain of ～0.2-0.4 and strain rate of 10~4 S~(-1). The following qualitative features of shear bands were established: · Shear bands have clear boundaries and their thickness does not depend on the initial particle size and has a typical value ～ 10μm. · The structure of the shear bands was dependent on initial particle size, suggesting differences in the mechanisms of flow. For the ～ 4μm alumina, comminution (break-up) and softening of particles were observed. For the ～ 0.4 μm particles, a peculiar structure consisting of a central crack with two lateral cracks was formed. ·Distributions of shear bands and displacement magnitudes were dependent on initial particle size.