Analytical model of hypervelocity penetration into rock

The results of dynamic compression tests of the rock revealed that the actual working pressure ranged from 5 GPa to 20 GPa when the penetration velocity ranged from 1000 m/s to 4000 m/s. The region is exactly the transition area where the compression state changes from elastoplasticity to hydrodynamics, and the rock is subject to restricted internal friction. Also the region lacks accurate representation in existing penetration theories. A study of the hydrodynamic was performed by using the internal friction theory. Equations were systematically presented which covered and linked up the elastoplasticity-semifluid with internal friction and hydrodynamic pressure. And the essential connections and differences between the penetration of hypervelocity kinetic energy bombs and common penetrating bombs were illuminated. Furthermore the velocity region of hypervelocity was demarcated theoretically, illuminating the transformation of the target medium with the increased penetration velocity from elastoplasticity to semifluid with internal friction and hydrodynamics. The calculations revealed the characteristic phenomenon that the decrease of penetration depth in that the abrasion of the bomb mass and the existence of a limitation depth. In conclusion the formulas to calculate the depth and diameter of the crater were presented.