Ballistic and Hypervelocity Impact and Penetration

Fundamentals of plane shock wave loading are described in relation to spherical shock loading which is the characteristic of ballistic and hypervelocity impact and penetration of materials, particularly metals and alloys. The evolution of microstructure with shock pressure and especially shock-wave-induced twinning and the role of stacking-fault free energy in fcc metals and alloys are discussed along with critical shock pressure for twinning and the twinning-microband microstructure transition for oblique shock loading and spherical shock associated with impact crater production and subsequent penetration of targets. This includes the role played by dynamic recrystallization (DRX) in solid-state flow which facilitates crater formation. The penetration of rods in contrast to spherical projectiles in thick targets and plug formation and ejection by adiabatic shear band formation is described along with the fundamental, dynamic recrystallization (DRX) microstructure which characterizes such shear bands. Shaped charge and explosively formed penetrator structures and performance as penetrators in thick target materials are described. The role of DRX in these processes is also discussed. Finally, rail erosion characteristic of DRX in railgun operation is illustrated briefly as a related example of extreme plastic deformation along with the concept of explosively driven magnetic flux generation.