The stability of shaped-charge jets

Abstract

Shaped-charge jets have a tendency to break up into a series of segments along the jet axis, as evidenced by flash radiographs. This paper studies the stability of stretching plastic shaped-charge jets by two approaches. First, a one-dimensional theory is formulated. This theory yields a stability criterion which depends on the instantaneous values of stress and the slope of the stress-strain curve. It also relates the disturbance growth rate to disturbance wavelength, stretching rate, and yield stress to density ratio. In the second approach, two-dimensional finite-difference calculations are performed which substantiate all of the trends indicated by the one-dimensional theory. Also, the two-dimensional calculation shows the existence of a critical wavelength; disturbances of this wavelength grow faster than all others. Other effects such as irregular surface disturbances and elasticity are also studied.