Application of shell jetting analysis to determine the location of the virtual origin in shaped charges

Abstract

Shaped charges are designed to produce high-velocity jets for penetration. During jet formation, the liner collapses and converges at a point source, also known as the virtual origin (VO), along the distance–time plane. The location of the VO must be known to allow the development of penetration analytical models. Here we determined the location of the VO using the ANSYS® Autodyn 2D shaped charge jetting technique. Jetting analysis was conducted for two shaped charges of 18 and 32 mm diameter. The explosive and casing were represented by Eulerian two-dimensional finite difference grids, whereas the liner was modelled using a shell formulation. The summary/history of the jetting analysis was used to determine the VO position in the shaped charges. Interpolating the point of intersection on the liner between the jet velocity (U-Jet) and the cumulative jet mass revealed the location of the VO at a distance equivalent to approximately two-thirds of the inner cone diameter of the shaped charges, in agreement with earlier studies based on different methods. Validation of this technique using the DiPersio, Simon and Merendino (DSM) model based on the Allison-Vitalli equation also showed good agreement with the numerical results.