24-10-2012, 11:38 AM
High Rate Plastic Deformation and Failure of Tungsten-Sintered Metals
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.