Hypervelocity impact heating of porous aluminum

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Abstract
Based on experimental shock data of Al'tschuler, Anderson, and Kormer, an equation of state from Zel'dovich is used to estimate thermodynamic characteristics of a porous aluminum target, after impact by iron or aluminum projectiles, in the impact velocity range ∼8–20 km s−1, which produces shock pressures in the range 0.4–8Mbar. The initial target distention, m=ρ0/ρ00, is varied from 1 to 3. It is found that projectile and target pressures and the projectile thermal energy are monotonically decreasing functions of m. The thermal energy E′ retained in the relaxed target is a monotonically increasing function of m. The electronic fraction of thermal pressure ranges from a few percent for a nonporous target at 8 km s−1 up to 20% at 20 km s−1 and m=3. Within the ranges of target density, ρ0i , and target distention, m, considered in this study, and in the impact velocity range Vi =8–16 km s−1, the relative effectiveness of these parameters in producing target heat E′ (erg/g) can be roughly characterized by the relation E′∝ lim ∼ ρ 0i 0.47 m 1.49 V i 2.13 . The minimum velocity that will produce significant target vaporization in aluminum‐aluminum impact decreases from 18.4 to 7.9 km s−1 as m is changed from 1 to 3, whereas that for iron‐aluminum impact drops from 14.0 to 7.4 km s−1.

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