An experimental, metallurgical and modelling analysis of silver and copper explosively formed projectiles (EFPs)

Abstract
This paper describes an experimental, metallurgical and modelling study into the structure and properties of silver and copper explosively fonned projectiles. The project started with the conditioning, processing and characterisation of the non-shocked silver and copper materials. Here, the material constants were derived for the Goldthorpe path-dependant constitutive model [1]. For the purposes of this study the warhead designs produced some conservative EFP projectiles. These were designed using the indigenous Eulerian hydrocode GRIM. Due to the ductile nature of both silver and copper, care was taken with respect to the equation of state, in particular with the temperature supplied to the constitutive models. The EFP projectiles were then experimentally recovered using soft-capturing techniques [2]. The comparison of the code predictions with the experimental radiography results was very good, suggesting that there could not be large material phase changes or significant changes to the microstructure of the material due to the explosively applied shock. Finally, the sectioning and metallurgical analysis of the recovered projectiles showed that although there were some variations in both grain size, microstructure and material hardness throughoutlacross the sectioned projectiles, these were not significant.