High Rate Plastic Deformation and Failure of Tungsten-Sintered Metals

Report No. ARL-RP-84
Authors: Todd W. Bjerke and William R. Edmanson
Date/Pages: September 2004; 12 pages
Abstract: The competition between plastic deformation and brittle fracture during high rate loading of a tungsten-sintered metal is examined through impact experiments, post-experiment microscopy, and numerical simulation. The impact specimens were beam-shaped with a square cross section made from 93% tungsten with a tungsten-nickel-iron binder. The specimens were impacted at the mid-span location with a tungsten striker bar having an initial speed of 55 m/s. Dynamic stretching of the beam rear surface and time of fracture initiation was measured with a strain gage. Strain gage signals indicated that the strain-to-failure was approximately 1.3%, however a significant number of microcracks were observed to have opened underneath the strain gage location. Scanning electron microscopy revealed that brittle ?pre-cracking? of the rear surface preceded the ultimate failure of the specimen. A numerical simulation of the impact event was performed using the finite element code ABAQUS to better evaluate the possible role of plastic deformation in the tungsten material prior to failure.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2004