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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Effects of particle size, shape and loading rate on the normal compaction of an advanced granular ceramic

Compaction behavior of granular materials is influenced by strain rate, particle size, and shape. In this report, boron carbide powders with different particle sizes under uni-axial strain conditions are studied using quasi-static compression, dynamic Kolsky bar experiments and normal plate impact. A rounded powder is compacted to investigate the effect of particle shape. The normal plate impact technique is an excellent tool in characterization of powder compaction behavior up to strain rates of ~10 5 s -1 . From our experiments, granular boron carbide shows a highly compressible behavior with significant volume compaction. Constitutive responses are obtained for four powders. Particle fracture is identified as key deformation mechanism. Dynamic loading introduces more particle fragmentation than quasi-static loading. Morphological characterization of particle shapes shows that the deformation from powder compaction alters the particle shape distribution, which is also rate-dependent. Particle size, shape and strain rate effects on the normal stress are discussed accordingly.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Depolarization mechanisms of PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} and PbZr{sub 0.95}Ti{sub 0.05}O{sub 3} poled ferroelectrics under high strain rate loading

Stress-induced and thermal-induced depolarization studies along with X-ray diffraction were performed on lead zirconate titanate ferroelectrics of different compositions, PbZr{sub 0.52}Ti{sub 0.48}O{sub 3} (PZT 52/48) and PbZr{sub 0.95}Ti{sub 0.05}O{sub 3} (PZT 95/5). Specimens were shock loaded perpendicular to the polarization vector. It was found that the polarity of the stress-induced charge released by PZT 52/48 and 95/5 was opposite to the polarity of the charge generated due to the piezoelectric effect. PZT 52/48 was only partially (45%) depolarized under 1.5 ± 0.1 GPa mechanical compression, as opposed to PZT 95/5 which was fully depolarized. The experimental results indicate that the stress-induced depolarization mechanisms are different for these two compositions. PZT 52/48 is transformed to a state with lower polarization, while PZT 95/5 undergoes a phase transition to a non-polar antiferroelectric phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Three-dimensional modeling and simulations of single-crystal and bi-crystal titanium for high-strain-rate loading conditions

High purity single crystal titanium (Ti) under shock wave loading is modeled under both one-dimensional and three-dimensional cylindrical conditions. Cylinder sizes of 10 μm and 20 μm radius are both considered in order to assess influence of boundary conditions. A thermodynamically consistent single crystal model for application to shock conditions is presented. The model accounts for the coupled non-linear elastic, dislocation slip, deformation twinning, and structural phase transformation response of the titanium material. Plate impact experiment results using a copper flyer are used to compare against the simulations for crystals oriented in [0001] and [10$\overline1$1] crystallographic directions. The one-dimensional and threedimensional simulations of the two differently oriented single crystals indicate differences between the one-dimensional and three-dimensional representation, especially for the [10$\overline1$1] oriented single crystal. This orientation breaks the relative orientation symmetry between the crystal and cylinder which otherwise exists for the [0001] oriented single crystal. A significant amount of heterogeneity in the field response of the[10$\overline1$1] oriented simulation was demonstrated due to the highly coupled nature of the deformation. A bi-crystal model composed of both the [0001] and [10$\overline1$1] orientations with the boundary between the two along the axis of the cylinder is also considered for a cylinder model size of 10 μm. The results indicate a strong interaction between the two grains that affects the ω phase volume fraction achieved relative to the single crystal calculations.

36 MATERIALS SCIENCE↗