Bending of Threaded and Unthreaded Tungsten Rods Under Oblique Impact

Report No. ARL-TR-3578
Authors: Martin N. Raftenberg and Todd W. Bjerke (both of ARL)
Date/Pages: August 2005; 50 pages
Abstract: We employed ballistic experiments and finite element (FE) analysis to explore the extent to which, and the mechanism by which, the threading on a tungsten heavy alloy rod increases its susceptibility to break up under conditions of oblique impact. In the laboratory, small-scale rods with and without threads were launched into thin rolled homogeneous armor plates at 1300 m/s and 60 degrees? obliquity. Fracture near the nose of the rod occurred more consistently with the threaded rods. LSDYNA1 was used to analyze plane strain elastic impact of threaded and unthreaded rods striking a rigid surface at 10 m/s and 60 degrees? obliquity. These calculations revealed a greater degree of bending in a threaded rod than in an unthreaded rod of the same diameter. The maximum principal stress, which has been used as a criterion for brittle tensile fracture, also attained larger values in the threaded than in the unthreaded rod. With the aid of static FE analyses of cantilevered, point-loaded, threaded and unthreaded rods, the results of which could be compared with an analytical result from plate theory, we associated the increased bending with a decrease in effective rod thickness. 1LS-DYNA, which is not an acronym, is a trademark of Livermore Software Technology Corp.
Distribution: Approved for public release
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Last Update / Reviewed: August 1, 2005