Failure wave effects in hypervelocity penetration

• Published in: International journal of impact engineering 1998-11, Vol.23 (1), p.995-1001
• Main Authors: Zilberbrand, E L, Vlasov, A S, Cazamias, J U, Bless, S J, Kozhushko, A A
• Format: Article
• Language: English
• ISSN: 0734-743X

It has been known for several years that glass is a relatively effective armor against shaped charge jets even though its performance against conventional long-rod projectiles is mediocre. Some of the authors have earlier postulated that this effect is due at least in part to an increase of the R sub t value at hypervelocity. This enhancement is due to the fact that in long-rod penetration of brittle materials, a failure wave is generated in front of the penetrator which prematurely damages the material; however, if the penetrator is supersonic relative to this failure velocity, penetration is always occurring in intact material. Consequently, the true strength of a brittle material is only measured in hypervelocity experiments. In order to avoid the uncertainties of analyzing shaped charge penetration data, we have conducted experiments with L/D = 10 W alloy rods ( rho = 17.2 g/cm exp 3 ) against glass targets ( rho = 2.5 g/cm exp 3 ) to unambiguously search for this effect. In low velocity experiments, the penetration was essentially hydrodynamic, while above 3.9 km /s, the R sub t -Y value was on the order of 5.7 to 7.2 GPa. This substantiates the failure wave hypothesis.