The research aims at developing a fundamental understanding of shear-band initiation and propagation. The materials that will be investigated, titanium and aluminum alloys, have great importance in the aerospace industry; they undergo shear localization during plastic deformation and this is an important practical problem. Systematic and integrated experimental and theoretical investigation of the phenomenon of shear-band formation will be carried out. This will lead to the prediction and control of shear instability and to the establishment of its effect on the strength and failure modes of a broad class of materials. Dynamic experiments will be performed, in order to generate shear bands under controlled conditions. The Hopkinson bar experimental technique will be used with both hat-shaped and double-notched specimens. Pulse amplitude and shape in the Hopkinson bar will be varied to control the extent of shear-band propagation. This will be followed by microstructural characterization involving optical, scanning, and transmission electron microscopy. The microstructure after controlled high-strain-rate deformation stages and prior to the onset of macroscopic shear localization, will also be systematically investigated in order to establish which internal defects can lead to the initiation of localization and to characterize the microstructural evolution. The microstructure at the tip of the shear band will be examined in order to establish the structural changes in this zone prior to shear band extension.
