Localized microjetting in the collapse of surface macrocavities

Abstract

This paper focuses on the multiscale mechanism of collapse of hemispherical annular surface macrocavities in steel caused by high strain, high strain rate plastic flow of copper. Experiments and simulations revealed that a two-stage process is responsible for the observed microjetting phenomena: the formation of lateral copper microjets from the localized shear flow in copper at the interface during the filling of the cavity, and their subsequent collision at the apex of the macrocavity generating two additional horizontal microjets. The lengths of these microjets were an order of magnitude smaller than the cavity size, but linearly scaled with cavity radius. This process of microjet development is sensitive to the cavity geometry and it is unlike the previously observed jetting phenomena in cavitation, impact crater collapse, or shock-induced cavity collapse.Introduction -This paper focuses on the phenomena of microjetting in the collapse of

Cavity collapse in highly heterogeneous granular mixtures with different grain size and porosity

“…In both cases, copper 110 soft temper was selected because of its resistance to shear localization due to low strength, high ductility, and heat conductivity. The toroidal cavities on the bottom and top plugs served for "soft" self-sealing of the samples during the test 30 to preserve integrity of the collapsed samples. The axial cavity in the bottom steel plug was necessary to avoid trapping of the small diameter central jet which can be detrimental for preserving microstructural features of the collapsed sample.…”