Abstract: To explore the mechanism of moderately thick water-backed metal plates penetrated by high-velocity blunt-nosed projectiles, the whole process of high-velocity blunt-nosed projectiles perpendicularly penetrating moderately thick water-backed metal plates was divided into three consecutive phases, i.e., compression and mushrooming phase, shearing and compression phase and shearing and intruding phase, according to different mechanical states and energy-dissipative mechanisms during penetrating process together with the high-velocity penetration-resistant characteristic of moderately thick water-backed metal plates. Based on the 3-phase penetration mechanism, an analytical model was established to calculate instantaneous residual velocities of the blunt-nosed projectiles perforating moderately thick water-backed metal plates. By adopting the model, the instantaneous residual velocities of cubic projectiles with 3.3g penetrating 5mm-thick water-backed steel plates were computed. Good agreements were obtained between the theoretical values and experimental results as well as corresponding numerical results. Due to the consideration for several phenomena, such as the dynamic supporting action and kinetic energy dissipation effort of the water medium behind the target, the 3-phase model can be employed to more reasonably predict the instantaneous residual velocities of the blunt-nosed projectiles perforating moderately thick water-backed metal plates, and therefore, has theoretical and engineering application value.

Key words: perforation mechanics, high-velocity blunt-nosed projectiles, water-backed target, instantaneous residual velocity, theoretical model