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 distancetime plane. The location of the VO must be known to allow the development of penetration analytical models. Here we determined the VO position 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 location of the VO of the shaped charges. Interpolating the point of intersection between the jet velocity (U-Jet) and the cumulative jet mass, on the liner, 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 using

Polylactic acid (PLA) is commonly used as a feedstock material for commercial 3D printing. As components manufactured from such material become more commonplace, it is inevitable that some of the resultant systems will be exposed to high strain-rate/impact events during their design-life (for example, components being dropped or even involved in a high-speed crash). To this end, understanding the shock properties of polylactic acid, in its role as a major raw material for 3D printed components, is of particular importance. In this work, printed samples of PLA were deformed by one-dimensional shock waves generated via the plate impact technique, allowing determination of both the Hugoniot Equation of State (EOS) and shear strength of the material. Both linear and non-linear EOS forms were considered in the U S -Up plane, with the best-fit found to take the general form U S = 1.28 + 3.06 − 1.09U 2 p in the U s −U p plane, consistent with other polymers. Use of lateral Manganin gauges embedded in the material flow allowed consideration of lateral stress evolution at impact pressures ranging from 0.3 to 4.0 GPa. Shear strength was observed to increase with impact stress, however, with minimal strengthening behind the shock front. Deviation of the measured stress from the predicted elastic measurement (corresponding to the PLA's Hugoniot Elastic Limit) was observed at longitudinal stress of 0.90 ± 0.05 GPa, within range of polymeric materials of similar characteristics-the first time this important parameter has been measured for PLA. As a result, this material characterisation will allow numerical modellers to accurately predict the structural response of PLA-based components/structures against high strain rates such as impacts or drops.

To gain further insight into the mechanisms underlying jet formation and elongation of laser sintered shaped charge liners under high strain rate deformation, Cu-Cr-Zr alloy liners fabricated by selective laser sintering process were deformed by explosive detonation. Their as-manufactured (liner) and resultant (slug) microstructure have been investigated in comparison with those of traditional machined liners employing both optical and scanning electron microscopy. The resultant slug microstructure of both machined and laser sintered liners revealed a smaller refined equiaxed grain size consistent with traditionally fabricated liners, characteristic of dynamic recrystallization. The disappearance of the (originally present) pores in the post-shot/recovered material microstructure was observed for laser-sintered liners. Comparison of the forward and rear region of the slug revealed variations in liner deformation, a result attributed to temperature variation across the slug. In contrast with the machined liner, a unique feature of precipitation, observed in the ending (slug) microstructure of the laser sintered liner is indicative of the associated extreme high strain and strain rate liner deformation which occurred during slug formation. The precipitates are likely compounds of Chromium and Zirconium which are constituents of the laser sintered copper alloy-the first time this observation is reported. This study provides a link between post charge evolution microstructure and liner manufacturing processes, potentially providing a new route to help optimise jet formation and effectiveness.