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Damage in plate impacts of 50 kbar and 30 kbar Cu, has been simulated with the traditional square wave loading profile of plate impacts and a triangular loading profile to study the time dependence of the damage evolution. At 30 kbar loading the square wave loading produces complete fracture while the triangular wave loading does not, similar to experiments by Koller et al. [1]. The calculated stress and strain loading histories are compared to provide insight for this result. The damage process in the triangular loading simply stops before fracture due to lack of kinetic energy. [ABSTRACT FROM AUTHOR]

Using a line-imaging VISAR to infer the position (x) and time (t) dependent distension of a spalling sample requires two assumptions: (1) a calculated velocity surface v[no spall] (x, t) for the no-spall case to compare with the observed v [observed](x, t) surface, and (2) a lack of significant wave processing by the near-surface microstructure. We have designed and are conducting a matrix of experiments to evaluate these assumptions. In each experiment, we use a line-imaging VISAR to measure the velocity history of carefully characterized tantalum and copper samples taken to an incipient spall condition. The pre-shot characterization included spatially resolved mapping of grain locations and orientations by electron backscatter diffraction (EBSD). These samples are then soft-recovered and sectioned along the same line as monitored by the line-imaging VISAR. An initial pair of experiments provided ∼1 mm of spall separation; we are preparing further experiments with incipient spall conditions. [ABSTRACT FROM AUTHOR]

Shock wave interactions within a material create a three-dimensional damage field of voids and/or strain localizations. Using a direct high explosive experiment, seven identical shots were performed to test the reproducibility of the damage fields between replicate samples. These samples, along with a sample from a plate impact experiment, were metallographically characterized to quantify the spallation void statistics. Results demonstrate that multiple section planes are required to accurately quantify the damage within a specimen. To further understand the three-dimensional nature of incipient spallation, serial sectioning was performed on a flyer plate experimental sample. Serial sectioning is yielding void and strain localization interactions not available from two-dimensional slices. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Controlling phase development and optimizing grain-to-grain connectivity are the primary issues that affect the performance of (Bi,Pb)[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub 10-x] (Bi-2223) multifilamentary tapes. Analytical electron microscopy was used to identify defects in these tapes that were either structural, compositional, or a combination of the two. Defects are introduced into the filament microstructure either intrinsically through the normal evolution of phases or extrinsically by various aspects of the thermo-mechanical processing. Relationships between connectivity and microstructure are discussed in light of the present understanding of current transport in Bi-2223 tapes. [ABSTRACT FROM AUTHOR]