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Shock compaction and impact response of thermite powder mixturesFredenburg, David Anthony 27 August 2010 (has links)
This dissertation focuses on developing a predictive method for determining the dynamic
densification behavior of thermite powder mixtures consisting of equivolumetric
mixtures of Ta + Fe₂O₃ and Ta + Bi₂O₃. Of primary importance to these highly reactive
powder mixtures is the ability to characterize the stress at which full compaction occurs,
the crush strength, which can significantly influence the stress required to initiate reaction
during dynamic or impact loading. Examined specifically are the quasi-static and dynamic
compaction responses of these mixtures. Experimentally obtained compaction responses
in the quasi-static regime are analyzed using available compaction models, and an analysis
technique is developed that allows for a correct measurement of the apparent yield strength
of the powder mixtures. The correctly determined apparent yield strength is combined with
an equation of state to yield a prediction of the shock densification response, including the
dynamic crush strength of the thermite powder mixtures. The validated approach is also extended
to the Al + Fe₂O₃ thermite system. It is found that accurate predictions of the crush
strength can be obtained through determination of the apparent yield strength of the powder
mixture when incorporated into the equation of state. It is observed that the predictive
ability in the incomplete compaction region is configurationally dependent for highly heterogeneous
thermite powder systems, which is in turn influenced by particle morphology
and differences in intrinsic properties of constituents (density, strength, etc.).
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Crush Strength Analysis of Hollow Glass MicrospheresDillinger, Benjamin Eugene 21 September 2016 (has links)
Porous Wall Hollow Glass Microspheres (PWHGMs) were developed by the Savannah River National Laboratory. What makes these microspheres unique is the interconnected porosity spread throughout their wall allowing various materials to travel from the surface to the hollow interior. With their characteristic porosity, the PWHGMs are a great tool for encapsulating or filtrating different materials. Unfortunately, there is little information available on the mechanical properties of PWHGMs.
The main goal of this research was to develop a method to crush individual microspheres and statistically analyze the results. One objective towards completing this goal was to measure the microsphere diameter distribution. Microsphere diameter is a major factor affecting strength as well as the Weibull parameters. Two different methods, microscopy counting and laser light scattering, used in the research yielded similar distributions.
The main objective of this research was to analyze the crush strength of individual microspheres. Using nanoindentation, data were collected to analyze the crush strength of PWHGMs in uniaxial compression. Nanoindentation data were used to analyze how the strength of the PWHGMs changes through the different stages of production and at different diameter ranges. Data for 3M commercial microspheres were compared to ARC microspheres. Most data were analyzed using a statistical technique known as the two parameter Weibull analysis. The data indicated that the strength generally decreased as the microsphere diameter increased. Scattering in the data was nearly the same across all sample sets tested. Results indicated that the PWHGMs were weaker than the ARC hollow glass microspheres (HGMs). This is primarily due to the addition of wall porosity in the PWHGM. / Master of Science
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