A series of approximately 150 tests were conducted on ceramic targets struck by cylindro-conical hard-steel projectiles at normal incidence up to velocities of about 1000 m/s. The primary objective was the determination of the effect of layering and the delineation of the ballistic limit of various combinations. In addition, a study of the erosive effect of the ceramic was executed. It was found that, on the basis of areal density, metal plates prefaced by ceramic materials are ballistically more inefficient than purely metallic targets in the low velocity range, while the reverse was found at speeds above 250 m/s. The eroded length was found to be related to the velocity of the projectile and the thickness of the ceramic layer. The projectile displacement data were found to be in very good accord with the results obtained from a previously utilized analytic force history taking into account the erosion process. The energy required to erode the projectile was found to be several orders of magnitude greater than that consumed in the fracture process of the frontal ceramic plate.
Explosive reactive armor (ERA) is a type of add-on armor that ustialty consists of tiles made of two metal plates with an e.xplosive layer in between. The ERA is placed at a certain distance from the main armor to enhance its performance. ERA design is optimized based on the required effectiveness of the tiles. Various methods of defining ERA effectiveness are described. The effectiveness parameters ofthe mass-ßux model and its derivatives, the effect of material properties, the escape length of the fet tip precursor, the explosive layer thickness, and the edge effects are analyzed, and correlations betören them are presented. Analysis tesults are compared with available experimental data and a very good correlation isfound.
We present an experimental technique for the direct measurement of stress-time histories in axially symmetric dynamic impacts, where the state of strain is not uniaxial. The technique is based on placing two different well-calibrated piezoresistance gauges in the desired location on the symmetry axis. The two measured resistance changes are then substituted in a system of two equations with two unknowns from which one obtains the axial stress and the lateral strain histories. We demonstrate the technique with manganin and constantan gauges which were calibrated both under uniaxial strain and hydrostatic conditions. As an example we bring the results of stress measurements inside thick polymethyl methacrylate targets which were impacted by thick copper discs. The measured stress-time history is then compared to that predicted by a two-dimensional Lagrangian code.
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