RESUMO
Magnesium, titanium and zirconium and their alloys are extensively used in industrial and military applications where they would be subjected to extreme environments of high stress and strain-rate loading. Their hexagonal close-packed (HCP) crystal lattice structures present interesting challenges for optimizing their mechanical response under such loading conditions. In this paper, we review how these materials respond to shock loading via plate-impact experiments. We also discuss the relationship between a heterogeneous and anisotropic microstructure, typical of HCP materials, and the directional dependency of the elastic limit and, in some cases, the strength prior to failure.
RESUMO
An experimental apparatus has been developed for performing shear tests on specimens held under moderately high hydrostatic pressures (up to the order of 10 GPa). This testing procedure experimentally determines the pressure dependent shear strength of thin foil specimens. This information is necessary for models of materials subjected to extreme pressures and can assist in model validation for models such as discrete dislocation dynamics simulations, among others. This paper reports the development of the experimental procedures and the results of initial experiments on thin foils of polycrystalline Ta performed under hydrostatic pressures ranging from 2 to 4 GPa. Subsequent characterization of the samples held under pressure established that the procedure described herein represents a reliable method to impose nearly uniform hydrostatic pressure on thin foil specimens. Both yielding and hardening behavior of Ta are observed to be sensitive to the imposed pressure.
