DIMENSIONALLY SCALED PENETRATION EXPERIMENTS - ALUMINUM TARGETS AND GLASS PROJECTILES 50 MU-M TO 3.2-MM IN DIAMETER

Spherical soda-lime glass projectiles 50, 150, 1000 and 3175 mum in di ameter (D(p)) in aluminum targets (series 1100, ''annealed'') of varia ble thickness T were used to determine how the penetration-hole diamet er (D(h)) varied as a function of D(p)/T at a constant impact velocity of 6 km/s. The target thickness ranged from infinite half-space geome tries to 0.8 mum thick foils. Virtually identical morphologies charact erize the penetration holes, no matter what projectile size, at equiva lent D(p)/T conditions. The relative hole diameter (D(h)/D(p)) decreas es systematically with increasing D(p)/T from D(h) congruent-to 4D(p) for massive targets, to D(h) = D(p) for very thin foils. A modest depe ndence on the absolute projectile size is observed; comparatively smal l cracters, yet relatively large penetration holes are produced by the smallest (50 mum) impactors. Nevertheless, linear dimensional scaling seems suitable for first-order estimates of D(p) from the measurement of D(h) and T on space-exposed surfaces. The projectile fragments and the debris dislodged from the target were intercepted by witness plat es that were located behind the target. The dispersion angle of this d ebris cloud depends on the thickness of the target. In addition, milli meter-sized impactors are collisionally fragmented with greater ease t han small impactors. Furthermore, we observe that systematic changes i n the specific energy of dislodged projectile and target material occu r as a function of D(p)/T. While linear scaling of target and projecti le dimensions is a useful framework to explain many observations and a ssociated shock processes, we suggest that consideration of the absolu te and relative shock-pulse duration in the projectile (t(p)) and targ et (t(t)) may ultimately be the more useful approach. It implicitly ac counts for all dimensions and, additionally, for specific impact veloc ities and pertinent material properties, via equations-of-state, for t he impacting pair.