I. Rigid body penetration into brittle materials. II. Phase change effect on shock wave propagation

A technique was developed to measure rigid body penetration depth time history under deceleration ∼105 g. The experimental results of steel projectile penetration into G-mixture mortar targets in the velocity range of 100 to 500 m/s show that (1) The target materials are damaged via compacting in front of penetration and via radial and lateral cracks surrounding penetration; (2) The contact length between projectile and target materials is <20% of final penetration depth; (3) Penetration duration is dominated by projectile length. It is not sensitive to projectile diameter and increases slowly with initial impact velocity; (4) Shock wave generation is the major process that controls projectile-target energy exchange during penetration based on the averaged deceleration that is linearly proportional to initial impact velocity; (5) Penetration depth time history is found to be scaled by a relation between normalized penetration depth and time. Based on the present data, we suggested an analytic rigid body penetration model that incorporates projectile-target contact area, friction coefficient, penetration stop, and normal stress models.; Stress wave profiles in vitreous GeO2 show that GeO2 response to planar impact includes an elastic precursor, a ramp wave and a shock wave. The Hugoniot relation is D = 0.917 + 1.711 u (km/s) in 6 to 40 GPa. Phase change in GeO2 is found to occur in the pressure range of 4 to 15 GPa under planar loading. The Hugoniots of vitreous GeO2 and fused SiO2 are found to coincide approximately if the pressure in fused SiO2 is scaled by the ratio of SiO2 to GeO2 density. A simple analytic model is suggested to explain the different decay rate of a spherical elastic wave in fused SiO2 and vitreous GeO2.