Analysis of the Noneroding Penetration of Tungsten Alloy Long Rods Into Aluminum Targets

Report No. ARL-TR-3075
Authors: Steven B. Segletes
Date/Pages: September 2003; 27 pages
Abstract: Data concerning the rigid/eroding-rod threshold transition are reported for hemispherical-nosed tungsten rods penetrating into thick 5083-aluminum targets. Presented data quantitatively buttress existing explanations. The current analysis suggests that the penetrator must bring to bear a different "apparent" strength in the noneroding- vs. the eroding-penetration regimes. Conventional one-dimensional penetration analysis reveals that the noneroding datum is wholly consistent with the notion of treating the rod as if it penetrated in a rigid-body fashion, possessing unrealistically high yield strength. Study of a recovered rod fragment reveals that the penetrating rod nonetheless deformed, but did so without erosion. Such an observation for hemispherical-nosed rods is consistent with past qualitative explanations posited for ogival-nosed rods. The phenomenon, supported by analysis, is that an exaggerated stress was axially applied by the rod to the target interface, composed of both the rod's intrinsic yield strength plus a confining stress caused by a lateral interference fit between the rod and target during the penetration event. The lateral interference of the target was kinematically sufficient to prevent an erosive flow field from being established in the rod. In such a fashion, the rod was able to employ the target's lateral resistance to great axial advantage.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2003