Research on Impact Initiation of Unconfined and Confined Explosives by Explosively Formed Projectile

Abstract Explosively formed projectile (EFP), characterized by its insensitivity to stand-off distance and high kinetic energy, demonstrates considerable potential for application in anti-missile munitions. Numerical simulation, theoretical modeling, and experimental studies were conducted to investigate the impact initiation of both unconfined and confined explosives by EFP. A simulation model for EFP formation and its subsequent impact initiation process was developed using Autodyn software. The initiation mechanisms of explosives under varying cover plate thicknesses were analyzed, revealing a transition in the initiation mode from shock wave initiation to direct impact initiation by the residual EFP. Based on the simulation results, an equivalent diameter calculation method was proposed to characterize the impact initiation behavior of annular cross-section EFP. By integrating the A-T penetration model and the Held criterion, an engineering model for predicting the critical initiation threshold of explosives by EFP impact was established. Experimental results verify the capability of this engineering model to predict the critical cover plate thickness, as well as the accuracy of the numerical simulations.