ADIABATIC SHEAR BANDS IN AXISYMMETRICAL IMPACT AND PENETRATION PROBLEMS

We study axisymmetric deformations of depleted uranium (DU) and tungst en heavy alloy (WHA) rods impacting at normal incidence either a Rat r igid or a thick steel target. Each deformable material is modeled as e lastic thermoviscoplastic; its flow stress increases with an increase in the effective plastic strain and effective plastic strain-rate but decreases with a rise in the temperature. An objective of this work is to ascertain when and where a shear band, defined as a narrow region of rapid, intense plastic deformation,forms in each material. The Tayl or impact simulations show that shear bands form earlier in WHA than i n DU for material parameters used. In the penetration simulations, she ar bands form continuously in the ejecta of the DU penetrator but only one shear band occurs in the WHA ejecta followed by its more uniform deformations.