An Explosively Formed Penetrator (EFP) is a type of shaped charge where the liner is formed into a high velocity slug, rather than a hyper velocity jet (which most shaped charges are). EFPs are infamous for their effectiveness as IEDs, which were used with great effect in the Iraq War.
The simulation presents a large, simple EFP, against 75mm of Rolled Homogenous Armour (RHA) at 800mm (4 Charge Diameters) of standoff. The EFP modelled is 200mm wide, 200mm deep, with a 8mm thick copper liner, and TNT explosive filler. The detonation point is at the back centre of the charge. In the simulation, the slug reaches a velocity of ~1500m/s. The formation and velocity of the EFP is in decent agreement with experimental data of similar EFP designs.
There are a variety of ways to simulate EFPs, with most modelling the liner as a Eulerian body, due to the large amounts of deformation. However, as the EFP slug takes a large distance to form and is relatively thin, the Eulerian domain would need to be very long and with a fine mesh, resulting in an exceptionally large amount of cells and a slow simulation.
Due to this, I chose to test if a Lagrangian liner would be suitable, with the results being surprisingly promising. The copper liner is made of 3D elements with a strain failure limit (this strain limit should be higher, however these excessively strained elements reduce the time increment and slow down the simulation so a compromise was made -this is why some of the material in the tail 'breaks' and converts to particles). A sheet body could be used for the liner as well, but this wouldn't be as visually impressive, especially in a crossection view.
16 июн 2023
