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Characterization of Aluminum Honeycomb and Experimentation for Model Development and Validation, Volume I: Discovery and Characterization Experiments for High-Density Aluminum Honeycomb

Lu, Wei-Yang L.; Korellis, John S.; Lee, Kenneth L.; Scheffel, Simon S.; Hinnerichs, Terry D.; Neilsen, Michael K.; Scherzinger, William M.

Honeycomb is a structure that consists of two-dimensional regular arrays of open cells. High-density aluminum honeycomb has been used in weapon assemblies to mitigate shock and protect payload because of its excellent crush properties. In order to use honeycomb efficiently and to certify the payload is protected by the honeycomb under various loading conditions, a validated honeycomb crush model is required and the mechanical properties of the honeycombs need to be fully characterized. Volume I of this report documents an experimental study of the crush behavior of high-density honeycombs. Two sets of honeycombs were included in this investigation: commercial grade for initial exploratory experiments, and weapon grade, which satisfied B61 specifications. This investigation also includes developing proper experimental methods for crush characterization, conducting discovery experiments to explore crush behaviors for model improvement, and identifying experimental and material uncertainties.

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TYPE SAND Report YEAR 2006
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Joining SI3N4 for Advanced Turbomachinery Applications

Glass, Sarah J.; Loehman, Ronald E.; Hosking, F.M.; Stephens, John J.; Vianco, Paul T.; Neilsen, Michael K.; Walker, Charles A.

The main objective of this project was to develop reliable, low-cost techniques for joining silicon nitride (Si{sub 3}N{sub 4}) to itself and to metals. For Si{sub 3}N{sub 4} to be widely used in advanced turbomachinery applications, joining techniques must be developed that are reliable, cost-effective, and manufacturable. This project addressed those needs by developing and testing two Si{sub 3}N{sub 4} joining systems; oxynitride glass joining materials and high temperature braze alloys. Extensive measurements were also made of the mechanical properties and oxidation resistance of the braze materials. Finite element models were used to predict the magnitudes and positions of the stresses in the ceramic regions of ceramic-to-metal joints sleeve and butt joints, similar to the geometries used for stator assemblies.

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TYPE Report YEAR 2000
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Computational methods for coupling microstructural and micromechanical materials response simulations

Holm, Elizabeth A.; Wellman, Gerald W.; Battaile, Corbett C.; Buchheit, Thomas E.; Fang, H.E.; Rintoul, Mark D.; Glass, Sarah J.; Knorovsky, Gerald A.; Neilsen, Michael K.

Computational materials simulations have traditionally focused on individual phenomena: grain growth, crack propagation, plastic flow, etc. However, real materials behavior results from a complex interplay between phenomena. In this project, the authors explored methods for coupling mesoscale simulations of microstructural evolution and micromechanical response. In one case, massively parallel (MP) simulations for grain evolution and microcracking in alumina stronglink materials were dynamically coupled. In the other, codes for domain coarsening and plastic deformation in CuSi braze alloys were iteratively linked. this program provided the first comparison of two promising ways to integrate mesoscale computer codes. Coupled microstructural/micromechanical codes were applied to experimentally observed microstructures for the first time. In addition to the coupled codes, this project developed a suite of new computational capabilities (PARGRAIN, GLAD, OOF, MPM, polycrystal plasticity, front tracking). The problem of plasticity length scale in continuum calculations was recognized and a solution strategy was developed. The simulations were experimentally validated on stockpile materials.

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TYPE Report YEAR 2000
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Results 76–99 of 99
Results 76–99 of 99