Amorphous metals, also referred to as bulk metallic glasses (BMGs), differ from ordinary metals in that their constituent atoms are not arranged on a crystalline lattice. Due to their randomly-ordered atomic structures, metallic glasses are known to exhibit unusual mechanical properties, such as near theoretical strength, large elastic strains, high hardness, excellent wear and corrosion resistance, and increased fracture toughness when compared to other brittle, high compressive strength materials. The dynamic response of BMGs is of considerable interest for gaining insight into the high strain-rate response of this class of materials and for potential applications, such as kinetic energy penetrators. In particular, the 82.5 mm bore single stage gas-gun at Case Western Reserve University is utilized to obtain shock wave profiles in a zirconium-based BMG, Zr41.25Ti13.75Ni10Cu12.5Be22.5, subjected to planar shock compression.
The bulk metallic glass samples were shock loaded by utilizing Ti-6Al-4V flyer plates to impact stresses around 7 GPa; the flyer thickness in each experiment was carefully designed to produce a state of tension near the center of the BMG target plates. During the experiments, the free-surface particle velocity history at the back of the bulk metallic glass target plate was recorded using a VALYNTM VISAR. These measurements were used to estimate the spall strength as a function of normal and shear stresses, and the Hugoniot elastic limit (HEL) of the Zr-based BMG.. Also the single stage gas-gun will be employed to determine the dynamic response of the Zr-based BMG with pressure-shear sandwich configuration (strain rates ~ 106 s-1). My Ph.D. research work includes: (1) Mechanisms of Slip Weakening of Rocks and Analog Materials at Co-Seismic Slip Rates; (2) High-speed Friction at Metal-on-metal Interfaces; (3) Spall Strength of Glass Fiber Reinforced Polymer Composites; (4) Spall strength, HEL and dynamic response of a Zr-based BMG material.
Post-doctoral work will investigate the high strain rate response of HSLA-65 steel over a range of test temperatures relevant to friction stir welding conditions. Additional experiments will be devised to investigate the friction coefficient under high strain rate conditions relevant to friction stir welding. These experiments are being conducted in collaboration with Prof. Vikas Prakash in the Department of Mechanical and Aerospace Engineering at CWRU.
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