Shear-band enforcement on flow upon stopping of penetrating projectiles by metallic targets

摘要

The influence of the penetrating rod material yield stress and elongation to failure on the flow field at the penetration head is analyzed using comparisons between predictions made by the One Streamline Model and Eulerian hydro-code runs. The lowest velocity at which the One Streamline model is still applicable is then defined. It is shown that between this velocity and the velocity where any further erosion completely stops, shear banding is enforced along the outgoing flow, changing its nature into what we called the "three-phase flow" or "split outgoing flow". This phenomenon is different from common shear-band formation in its being a semi steady state and not just a very short-lived transient phenomenon. It occurs in ductile metallic targets and it strongly affects their mode of failure near the ballistic limit. This prediction is confirmed by a cut in an aluminum witness target nearly penetrated by a steel projectile.