FINITE-ELEMENT SIMULATIONS OF SHEAR LOCALIZATION IN PLATE IMPACT

SHEAR BAND development in a tungsten heavy alloy (WHA) during pressure shear plate impact is analysed numerically. The alloy has a microstru cture of hard tungsten grains embedded in a soft alloy matrix. A two-d imensional, plane strain model of the alloy microstructure is used in the computations. For this model microstructure a fully coupled thermo -mechanical initial boundary value problem is formulated and solved, a ccounting for finite deformations, inertia, heat conduction, thermal s oftening, strain hardening and strain-rate hardening. Calculations are carried out for distributions of uniform grains and for microstructur es obtained from digitized micrographs of the actual alloy. The effect s of variations in grain volume fraction and grain size are considered . Experiments and the numerical calculations show that the two-phase a lloy is more susceptible to shear banding than either of the constitue nt phases. While the onset of shear localization depends on the grain distribution and volume fraction, the shear band width is found to be set by heat conduction and is insensitive to the grain volume fraction and the grain morphology. The shear band width obtained from the calc ulations is in good agreement with what is observed in the experiments . Furthermore, the computed shapes of the deformed tungsten grains ins ide the band resemble closely the observed shapes of the deformed grai ns in the experiments.