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11.20.14 Ruggles

RESOLVING GEOMETRICALLY NECESSARY DISLOCATIONS ONTO INDIVIDUAL SLIP SYSTEMS USING EBSD-BASED CONTINUUM DISLOCATION MICROSCOPY

Timothy Ruggles, PhD Candidate, Brigham Young University
November 20, 2014, 10:30 am, NIA Building 100, Room 137

Abstract:
Modeling of plasticity is often hampered by the difficulty in accurately characterizing dislocation density on the microscale for real samples. It is particularly difficult to resolve measured dislocation content onto individual dislocation systems at the length scales most commonly of interest in plasticity studies. The Nye-Kroner continuum plasticity equations provide a link between lattice information recoverable via high resolution electron backscatter diffraction (EBSD) and the geometrically necessary dislocation content of the material. This presentation addresses a number of challenges in implementing EBSD continuum dislocation microscopy, including estimation of unknown lattice derivatives, solution of the underconstrained Nye-Kroner problem, and optimization of EBSD parameters. Two novel forms of dislocation microscopy are also presented, one that employs classical dislocation mechanics instead of the Nye-Kroner continuum relationship, and another that extracts information about the statistically stored dislocation content of the material.

Biography:
Tim Ruggles lives in Provo, UT with his wife and son where he is a doctoral candidate at Brigham Young University in mechanical engineering. Most of his research has been in using EBSD to characterize the dislocation content of metals, but he has also done research in materials design and fracture mechanics in advanced high strength steels. He originally hails from Allentown, PA.

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