A model for fragmentation of hard metallic targets due to projectile perforation

When a projectile perforates a hard metallic target it will emerge with a bundle of fragments from the target material. A model is suggested for the production of these fragments, which gives the total mass as well as the distribution of fragment masses, velocities and directions of motion. The intended application of the model is in computer programs for assessment of effects and vulnerability of complex targets such as tanks, fighters and naval ships. For this purpose rather simple physical models, such as the one suggested in this report, are to prefer instead of mostly empirical models. The suggested model involves two different fragment groups. One group consists of larger (spalling) fragments with velocities associated with the particle velocities from elastic wave reflection at the rear target surface. The other group has smaller total mass and consists of smaller but faster-moving fragments that are accelerated through contact with the residual projectile. The mass ratio between these two groups is a crucial parameter in the model and must be determined from experimental results. In reality the smaller but faster-moving fragments overtake the larger spalling fragments, but this complication is neglected in the model.