In recent years, numerous studies have been undertaken to advance the understanding of the various mechanisms involved in projectile penetration processes leading to significant improvements in predictive capability. This work is concerned with the special case of plugging of plates that are thin or of intermediate thickness struck by blunt projectiles at normal incidence. The resulting penetration model extends existing theories to include projectile and plate deformation over the velocity range from the ballistic limit up to the hyper-velocity regime.

The analysis utilizes uniaxial plastic wave theory to construct a five-stage model resulting from penetration that consists of indentation, plug formation, plug separation, plug slipping, and post-perforation deformation. The dynamic response of the target is modeled by a plastic hinge resulting from the single deflection mechanism of direct shear. The striker is generally considered as rigid with an extension presented for deforming projectiles, while the target material is characterized in the dynamic regime by a rigid/plastic linear work-hardening constitutive relation. The equations of motion are obtained for the small number of rigid bodies defined by the system components, the various wave fronts and the hinges.

The rigid projectile case was coded in Fortran IV and was run on a PDP-11/60 computer. The experimental program was conducted to verify the assumptions and check the overall efficacy. The 0.04 and 0.034 kg blunt hard-steel projectiles were shot with a pneumatic and powder guns against 3.2, 6.4, 9.8, and 12.75 mm thick 2024-0 aluminum plates at velocities up to 600 m/s. A previously developed instrumented projectile permitted the determination of the force history resulting from the impact.

Numerical and experimental results for the final velocity showed good correlation especially for tests substantially above the ballistic limit. Excellent correspondence was obtained for all system parameters for thicker plates at all impact velocities. Plug thickness was always predicted to within 10%. The analysis provided good agreement with measured force histories and penetration durations. The axial shear deformation mode does not adequately predict the total target deflection and contributes only within a narrow zone of the order of projectile radius, with bending being the dominant mechanism. However, its inclusion was found to be significant for the prediction of trends in system behavior especially near the ballistic limit.